Genetic Evidence of Contemporary Dispersal of the Intermediate Snail Host of Schistosoma japonicum: Movement of an NTD Host Is Facilitated by Land Use and Landscape Connectivity

PubMed Central

Chang, Howard; Li, Qunna; Hoover, Christopher M.; Wilke, Thomas; Clewing, Catharina; Carlton, Elizabeth J.; Liang, Song; Lu, Ding; Zhong, Bo; Remais, Justin V.

2016-01-01

Background While the dispersal of hosts and vectors—through active or passive movement—is known to facilitate the spread and re-emergence of certain infectious diseases, little is known about the movement ecology of Oncomelania spp., intermediate snail host of the parasite Schistosoma japonicum, and its consequences for the spread of schistosomiasis in East and Southeast Asia. In China, despite intense control programs aimed at preventing schistosomiasis transmission, there is evidence in recent years of re-emergence and persistence of infection in some areas, as well as an increase in the spatial extent of the snail host. A quantitative understanding of the dispersal characteristics of the intermediate host can provide new insights into the spatial dynamics of transmission, and can assist public health officials in limiting the geographic spread of infection. Methodology/Principal findings Oncomelania hupensis robertsoni snails (n = 833) were sampled from 29 sites in Sichuan, China, genotyped, and analyzed using Bayesian assignment to estimate the rate of recent snail migration across sites. Landscape connectivity between each site pair was estimated using the geographic distance distributions derived from nine environmental models: Euclidean, topography, incline, wetness, land use, watershed, stream use, streams and channels, and stream velocity. Among sites, 14.4% to 32.8% of sampled snails were identified as recent migrants, with 20 sites comprising >20% migrants. Migration rates were generally low between sites, but at 8 sites, over 10% of the overall host population originated from one proximal site. Greater landscape connectivity was significantly associated with increased odds of migration, with the minimum path distance (as opposed to median or first quartile) emerging as the strongest predictor across all environmental models. Models accounting for land use explained the largest proportion of the variance in migration rates between sites. A greater number of irrigation channels leading into a site was associated with an increase in the site’s propensity to both attract and retain snails. Conclusions/Significance Our findings have important implications for controlling the geographic spread of schistosomiasis in China, through improved understanding of the dispersal capacity of the parasite’s intermediate host. PMID:27977674

Genetic Evidence of Contemporary Dispersal of the Intermediate Snail Host of Schistosoma japonicum: Movement of an NTD Host Is Facilitated by Land Use and Landscape Connectivity.

PubMed

Head, Jennifer R; Chang, Howard; Li, Qunna; Hoover, Christopher M; Wilke, Thomas; Clewing, Catharina; Carlton, Elizabeth J; Liang, Song; Lu, Ding; Zhong, Bo; Remais, Justin V

2016-12-01

While the dispersal of hosts and vectors-through active or passive movement-is known to facilitate the spread and re-emergence of certain infectious diseases, little is known about the movement ecology of Oncomelania spp., intermediate snail host of the parasite Schistosoma japonicum, and its consequences for the spread of schistosomiasis in East and Southeast Asia. In China, despite intense control programs aimed at preventing schistosomiasis transmission, there is evidence in recent years of re-emergence and persistence of infection in some areas, as well as an increase in the spatial extent of the snail host. A quantitative understanding of the dispersal characteristics of the intermediate host can provide new insights into the spatial dynamics of transmission, and can assist public health officials in limiting the geographic spread of infection. Oncomelania hupensis robertsoni snails (n = 833) were sampled from 29 sites in Sichuan, China, genotyped, and analyzed using Bayesian assignment to estimate the rate of recent snail migration across sites. Landscape connectivity between each site pair was estimated using the geographic distance distributions derived from nine environmental models: Euclidean, topography, incline, wetness, land use, watershed, stream use, streams and channels, and stream velocity. Among sites, 14.4% to 32.8% of sampled snails were identified as recent migrants, with 20 sites comprising >20% migrants. Migration rates were generally low between sites, but at 8 sites, over 10% of the overall host population originated from one proximal site. Greater landscape connectivity was significantly associated with increased odds of migration, with the minimum path distance (as opposed to median or first quartile) emerging as the strongest predictor across all environmental models. Models accounting for land use explained the largest proportion of the variance in migration rates between sites. A greater number of irrigation channels leading into a site was associated with an increase in the site's propensity to both attract and retain snails. Our findings have important implications for controlling the geographic spread of schistosomiasis in China, through improved understanding of the dispersal capacity of the parasite's intermediate host.

Is Galba schirazensis (Mollusca, Gastropoda) an intermediate host of Fasciola hepatica (Trematoda, Digenea) in Ecuador?

PubMed

Caron, Yannick; Celi-Erazo, Maritza; Hurtrez-Boussès, Sylvie; Lounnas, Mannon; Pointier, Jean-Pierre; Saegerman, Claude; Losson, Bertrand; Benítez-Ortíz, Washington

2017-01-01

Fasciolosis is a widely distributed disease in livestock in South America but knowledge about the epidemiology and the intermediate hosts is relatively scarce in Ecuador. For three months, lymnaeid snails were sampled (n = 1482) in Pichincha Province at two sites located in a highly endemic area. Snails were identified (based on morphology and ITS-2 sequences) and the infection status was established through microscopic dissection and a multiplex polymerase chain reaction (PCR)-based technique. Techniques based on morphology were not useful to accurately name the collected snail species. Comparison with available DNA sequences showed that a single snail species was collected, Galba schirazensis. Live rediae were observed in 1.75% (26/1482) and Fasciola sp. DNA was detected in 6% (89/1482) of collected snails. The COX-1 region permitted identification of the parasite as Fasciola hepatica. The relative sensitivity and specificity of the microscope study, compared to PCR results, were 25.84% and 99.78%, respectively. The mean size of the snails recorded positive for F. hepatica through crushing and microscopy was significantly higher than the mean size of negative snails, but there was no such difference in PCR-positive snails. The role of G. schirazensis as an intermediate host of F. hepatica in Ecuador is discussed and the hypothesis of an adaptation of the parasite to this invasive snail is proposed. For the first time, an epidemiological survey based on molecular biology-based techniques assessed the possible role of lymnaeid snails in the epidemiology of fasciolosis in Ecuador. © Y. Caron et al., published by EDP Sciences, 2017.

Is Galba schirazensis (Mollusca, Gastropoda) an intermediate host of Fasciola hepatica (Trematoda, Digenea) in Ecuador?

PubMed Central

Caron, Yannick; Celi-Erazo, Maritza; Hurtrez-Boussès, Sylvie; Lounnas, Mannon; Pointier, Jean-Pierre; Saegerman, Claude; Losson, Bertrand; Benítez-Ortíz, Washington

2017-01-01

Fasciolosis is a widely distributed disease in livestock in South America but knowledge about the epidemiology and the intermediate hosts is relatively scarce in Ecuador. For three months, lymnaeid snails were sampled (n = 1482) in Pichincha Province at two sites located in a highly endemic area. Snails were identified (based on morphology and ITS-2 sequences) and the infection status was established through microscopic dissection and a multiplex polymerase chain reaction (PCR)-based technique. Techniques based on morphology were not useful to accurately name the collected snail species. Comparison with available DNA sequences showed that a single snail species was collected, Galba schirazensis. Live rediae were observed in 1.75% (26/1482) and Fasciola sp. DNA was detected in 6% (89/1482) of collected snails. The COX-1 region permitted identification of the parasite as Fasciola hepatica. The relative sensitivity and specificity of the microscope study, compared to PCR results, were 25.84% and 99.78%, respectively. The mean size of the snails recorded positive for F. hepatica through crushing and microscopy was significantly higher than the mean size of negative snails, but there was no such difference in PCR-positive snails. The role of G. schirazensis as an intermediate host of F. hepatica in Ecuador is discussed and the hypothesis of an adaptation of the parasite to this invasive snail is proposed. For the first time, an epidemiological survey based on molecular biology-based techniques assessed the possible role of lymnaeid snails in the epidemiology of fasciolosis in Ecuador. PMID:28664841

Metagonimoides oregonensis (Heterophyidae:Digenea) Infection in pleurocerid snails and Desmognathus quadramaculatus salamander larvae in southern Appalachian streams

Treesearch

Lisa K. Belden; William E. Peterman; Stephen A. Smith; Lauren R. Brooks; E.F. Benfield; Wesley P. Black; Zhaomin Yang; Jeremy M. Wojdak

2012-01-01

Metagonimoides oregonensis (Heterophyidae) is a little-known digenetic trematode that uses raccoons and possibly mink as definitive hosts, and stream snails and amphibians as intermediate hosts. Some variation in the life cycle and adult morphology in western and eastern populations has been previously noted. In the southern Appalachians, Pleurocera snails and stream...

Trematode communities in snails can indicate impact and recovery from hurricanes in a tropical coastal lagoon.

PubMed

Aguirre-Macedo, María Leopoldina; Vidal-Martínez, Victor M; Lafferty, Kevin D

2011-11-01

In September 2002, Hurricane Isidore devastated the Yucatán Peninsula, Mexico. To understand its effects on the parasites of aquatic organisms, we analyzed long-term monthly population data of the horn snail Cerithidea pliculosa and its trematode communities in Celestún, Yucatán, Mexico before and after the hurricane (February 2001 to December 2009). Five trematode species occurred in the snail population: Mesostephanus appendiculatoides, Euhaplorchis californiensis, two species of the genus Renicola and one Heterophyidae gen. sp. Because these parasites use snails as first intermediate hosts, fishes as second intermediate hosts and birds as final hosts, their presence in snails depends on food webs. No snails were present at the sampled sites for 6 months after the hurricane. After snails recolonised the site, no trematodes were found in snails until 14 months after the hurricane. It took several years for snail and trematode populations to recover. Our results suggest that the increase in the occurrence of hurricanes predicted due to climate change can impact upon parasites with complex life cycles. However, both the snail populations and their parasite communities eventually reached numbers of individuals and species similar to those before the hurricane. Thus, the trematode parasites of snails can be useful indicators of coastal lagoon ecosystem degradation and recovery. Copyright © 2011 Australian Society for Parasitology Inc. All rights reserved.

Effect of Echinostoma friedi (Trematoda: Echinostomatidae) experimental infection on longevity, growth and fecundity of juvenile Radix peregra (Gastropoda: Lymnaeidae) and Biomphalaria glabrata (Gastropoda: Planorbidae) snails.

PubMed

Muñoz-Antoli, Carla; Marín, Antoni; Toledo, Rafael; Esteban, José-Guillermo

2007-11-01

The effect of Echinostoma friedi experimental infection on longevity, growth and fecundity of two susceptible first intermediate host snails, Radix peregra and Biomphalaria glabrata, was studied to contrast the level of compatibility. 120 R. peregra and 150 B. glabrata snails were used exposed to one, three or five miracidia and divided in three categories: INF (snails exposed and infected); ENI (exposed but not infected) and C (control or not miracidial-exposed snails). R. peregra INF snails' death process starts sooner, but in a prolonged extension, while B. glabrata INF snails have a much shorter life span. The infection and the miracidial exposure are able to reduce R. peregra normal development (stunting). B. glabrata INF snails' growth exceeds that of C snails (gigantism). E. friedi produces a total parasitic castration of R. peregra and B. glabrata INF snails. R. peregra would be considered as the required snail host, while B. glabrata only as an adequate snail host.

Transplantation of schistosome sporocysts between host snails: A video guide

PubMed Central

Mouahid, Gabriel; Rognon, Anne; de Carvalho Augusto, Ronaldo; Driguez, Patrick; Geyer, Kathy; Karinshak, Shannon; Luviano, Nelia; Mann, Victoria; Quack, Thomas; Rawlinson, Kate; Wendt, George; Grunau, Christoph; Moné, Hélène

2018-01-01

Schistosomiasis is an important parasitic disease, touching roughly 200 million people worldwide. The causative agents are different Schistosoma species. Schistosomes have a complex life cycle, with a freshwater snail as intermediate host. After infection, sporocysts develop inside the snail host and give rise to human dwelling larvae. We present here a detailed step-by-step video instruction in English, French, Spanish and Portuguese that shows how these sporocysts can be manipulated and transferred from one snail to another. This procedure provides a technical basis for different types of ex vivo modifications, such as those used in functional genomics studies. PMID:29487916

Global assessment of schistosomiasis control over the past century shows targeting the snail intermediate host works best

USGS Publications Warehouse

Sokolow, Susanne H.; Wood, Chelsea L.; Jones, Isabel J.; Swartz, Scott J.; Lopez, Melina; Hsieh, Michael H.; Lafferty, Kevin D.; Kuris, Armand M.; Rickards, Chloe; De Leo, Giulio A.

2016-01-01

Snail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis.

Reduced transmission of human schistosomiasis after restoration of a native river prawn that preys on the snail intermediate host

USGS Publications Warehouse

Sokolow, Susanne H.; Huttinger, Elizabeth; Jouanard, Nicolas; Hsieh, Michael H.; Lafferty, Kevin D.; Kuris, Armand M.; Riveau, Gilles; Senghor, Simon; Thiam, Cheikh; D'Diaye, Alassane; Faye, Djibril Sarr; De Leo, Giulio A.

2015-01-01

Eliminating human parasitic disease often requires interrupting complex transmission pathways. Even when drugs to treat people are available, disease control can be difficult if the parasite can persist in nonhuman hosts. Here, we show that restoration of a natural predator of a parasite’s intermediate hosts may enhance drug-based schistosomiasis control. Our study site was the Senegal River Basin, where villagers suffered a massive outbreak and persistent epidemic after the 1986 completion of the Diama Dam. The dam blocked the annual migration of native river prawns (Macrobrachium vollenhoveni) that are voracious predators of the snail intermediate hosts for schistosomiasis. We tested schistosomiasis control by reintroduced river prawns in a before-after-control-impact field experiment that tracked parasitism in snails and people at two matched villages after prawns were stocked at one village’s river access point. The abundance of infected snails was 80% lower at that village, presumably because prawn predation reduced the abundance and average life span of latently infected snails. As expected from a reduction in infected snails, human schistosomiasis prevalence was 18 ± 5% lower and egg burden was 50 ± 8% lower at the prawn-stocking village compared with the control village. In a mathematical model of the system, stocking prawns, coupled with infrequent mass drug treatment, eliminates schistosomiasis from high-transmission sites. We conclude that restoring river prawns could be a novel contribution to controlling, or eliminating, schistosomiasis.                            

Modeling the combined influence of host dispersal and waterborne fate and transport on pathogen spread in complex landscapes

PubMed Central

Lu, Ding; McDowell, Julia Z.; Davis, George M.; Spear, Robert C.; Remais, Justin V.

2012-01-01

Environmental models, often applied to questions on the fate and transport of chemical hazards, have recently become important in tracing certain environmental pathogens to their upstream sources of contamination. These tools, such as first order decay models applied to contaminants in surface waters, offer promise for quantifying the fate and transport of pathogens with multiple environmental stages and/or multiple hosts, in addition to those pathogens whose environmental stages are entirely waterborne. Here we consider the fate and transport capabilities of the human schistosome Schistosoma japonicum, which exhibits two waterborne stages and is carried by an amphibious intermediate snail host. We present experimentally-derived dispersal estimates for the intermediate snail host and fate and transport estimates for the passive downstream diffusion of cercariae, the waterborne, human-infective parasite stage. Using a one dimensional advective transport model exhibiting first-order decay, we simulate the added spatial reach and relative increase in cercarial concentrations that dispersing snail hosts contribute to downstream sites. Simulation results suggest that snail dispersal can substantially increase the concentrations of cercariae reaching downstream locations, relative to no snail dispersal, effectively putting otherwise isolated downstream sites at increased risk of exposure to cercariae from upstream sources. The models developed here can be applied to other infectious diseases with multiple life-stages and hosts, and have important implications for targeted ecological control of disease spread. PMID:23162675

Epidemiology of cercarial stage of trematodes in freshwater snails from Chiang Mai province, Thailand.

PubMed

Chontananarth, Thapana; Wongsawad, Chalobol

2013-03-01

To investigate the epidemiological situation of cercarial trematodes infection in freshwater snails from different water resources in Chiang Mai province, Thailand. The snail specimens were collected from 13 districts of Chiang Mai province during April 2008 to February 2012. The prevalence of cercarial infection in snails was investigated using the crushing method. The drawing was done with the help of a camera lucida for the morphological study. A total of 2 479 snail individuals were collected and classified into 7 families, 11 genera, and 14 species, Among them, 8 snails species were found to be infected with an overall prevalence of 17.27% (428/2 479), which infected with nine groups of cercariae; gymnocephalous cercaria, strigea cercaria, megalurous cercaria, monostome cercaria, parapleurolophocercous cercaria (Haplorchis cercaria), pleurolophocercous cercaria, furcocercous cercaria (Transversotrema cercaria), xiphidiocercaria, and virgulate cercaria. The parapleurolophocercous cercaria was found to be the dominant type among the cercarial infection in the snails (64.25%). The various species of snails found in the research location act as the intermediate hosts for the high prevalence of parasitic infection of many species of mammals. This work will provide new information on both the distribution and first intermediate host of trematodes.

Density of Trematocranus placodon (Pisces: Cichlidae): a predictor of density of the schistosome intermediate host, Bulinus nyassanus (Gastropoda: Planorbidae), in Lake Malaŵi.

PubMed

Madsen, Henry; Stauffer, Jay R

2011-06-01

From the mid-1980s, we recorded a significant increase in urinary schistosomiasis infection rate and transmission among inhabitants of lakeshore communities in the southern part of Lake Malaŵi, particularly on Nankumba peninsula in Mangochi District. We suggested that the increase was due to over-fishing, which reduced the density of snail-eating fishes, thereby allowing schistosome intermediate host snails to increase to higher densities. In this article, we collected data to test this hypothesis. The density of both Bulinus nyassanus, the intermediate host of Schistosoma haematobium, and Melanoides spp. was negatively related to density of Trematocranus placodon, the most common of the snail-eating fishes in the shallow water of Lake Malaŵi. Both these snails are consumed by T. placodon. Transmission of S. haematobium through B. nyassanus only occurs in the southern part of the lake and only at villages where high density of the intermediate host is found relatively close to the shore. Thus, we believe that implementation of an effective fish ban up to 100-m offshore along these specific shorelines in front of villages would allow populations of T. placodon to increase in density and this would lead to reduced density of B. nyassanus and possibly schistosome transmission. To reduce dependence on natural fish populations in the lake and still maintain a source of high quality food, culture of indigenous fishes may be a viable alternative.

Snail species diversity impacts the infection patterns of Echinostoma spp.: Examples from field collected data.

PubMed

Zimmermann, Michael R; Luth, Kyle E; Esch, Gerald W

2017-09-26

Rapid losses of biodiversity due to the changing landscape have spurred increased interest in the role of species diversity and disease risk. A leading hypothesis for the importance of biodiversity in disease reduction is the dilution effect, which suggests that increasing species diversity within a system decreases the risk of disease among the organisms inhabiting it. The role of species diversity in trematode infection was investigated using field studies from sites across the U.S. to examine the impact of snail diversity in the infection dynamics of both first and second intermediate larval stages of Echinostoma spp. parasites. The prevalence of Echinostoma spp. sporocysts/rediae infection was not affected by increases in snail diversity, but significant negative correlations in metacercariae prevalence and intensity with snail diversity were observed. Additionally, varying effectiveness of the diluting hosts was found, i.e., snail species that were incompatible first intermediate hosts for Echinostoma spp. were more successful at diluting the echinostome parasites in the focal species, while H. trivolvis, a snail species that can harbor the first intermediate larval stages, amplified infection. These findings have important implications not only on the role of species diversity in reducing disease risk, but the success of the parasites in completing their life cycles and maintaining their abundance within an aquatic system.

Echinostoma revolutum: freshwater snails as the second intermediate hosts in Chiang Mai, Thailand.

PubMed

Chantima, Kittichai; Chai, Jong-Yil; Wongsawad, Chalobol

2013-04-01

The occurrence of 37-collar spined echinostome metacercariae in freshwater snails was investigated in 6 districts of Chiang Mai Province, Thailand, from October 2011 to April 2012. A total of 2,914 snails that belong to 12 species were examined, and 7 snail species (Clea helena, Eyriesia eyriesi, Bithynia funiculata, Bithynia siamensis siamensis, Filopaludina doliaris, Filopaludina sumatrensis polygramma, and Filopaludina martensi martensi) were found infected with echinostome metacercariae. The prevalence of metacercariae was the highest in Filopaludina spp. (38.5-58.7%) followed by B. funiculata (44.0%), E. eyriesi (12.5%), B. siamensis siamensis (8.2%), and C. helena (5.1%). Metacercariae were experimentally fed to hamsters and domestic chicks, and adult flukes were recovered from both hosts at days 15 and 20 post-infection. The adult flukes were identified based on morphological features, morphometrics, host-parasite relationships, and geographical distribution. They were compatible to Echinostoma revolutum or Echinostoma jurini, with only minor differences. As the adults were recovered from both hamsters and chicks, our specimens were more compatible to E. revolutum rather than E. jurini (reported only from mammals). This is the first report for metacercariae of E. revolutum in the snail host, C. helena, and also confirmed that Filopaludina spp., E. eryresi, and Bithynia spp. act as the second intermediate hosts of E. revolutum under natural conditions, which are indigenously distributed in Chiang Mai province.

Echinostoma revolutum: Freshwater Snails as the Second Intermediate Hosts in Chiang Mai, Thailand

PubMed Central

Chantima, Kittichai; Chai, Jong-Yil

2013-01-01

The occurrence of 37-collar spined echinostome metacercariae in freshwater snails was investigated in 6 districts of Chiang Mai Province, Thailand, from October 2011 to April 2012. A total of 2,914 snails that belong to 12 species were examined, and 7 snail species (Clea helena, Eyriesia eyriesi, Bithynia funiculata, Bithynia siamensis siamensis, Filopaludina doliaris, Filopaludina sumatrensis polygramma, and Filopaludina martensi martensi) were found infected with echinostome metacercariae. The prevalence of metacercariae was the highest in Filopaludina spp. (38.5-58.7%) followed by B. funiculata (44.0%), E. eyriesi (12.5%), B. siamensis siamensis (8.2%), and C. helena (5.1%). Metacercariae were experimentally fed to hamsters and domestic chicks, and adult flukes were recovered from both hosts at days 15 and 20 post-infection. The adult flukes were identified based on morphological features, morphometrics, host-parasite relationships, and geographical distribution. They were compatible to Echinostoma revolutum or Echinostoma jurini, with only minor differences. As the adults were recovered from both hamsters and chicks, our specimens were more compatible to E. revolutum rather than E. jurini (reported only from mammals). This is the first report for metacercariae of E. revolutum in the snail host, C. helena, and also confirmed that Filopaludina spp., E. eryresi, and Bithynia spp. act as the second intermediate hosts of E. revolutum under natural conditions, which are indigenously distributed in Chiang Mai province. PMID:23710085

Infections of Larval Stages of Dicrocoelium dendriticum and Brachylaima sp. in Brown Garden Snail, Helix aspersa, in Turkey.

PubMed

Köse, Mustafa; Eser, Mustafa; Kartal, Kürşat; Bozkurt, Mehmet Fatih

2015-10-01

The aim of this study was to determine the presence and prevalence of larval stages of Dicrocoelium dendriticum and Brachylaima sp. in the first intermediate host, a species of land snail, Helix aspersa, in Turkey. A total of 211 snails were collected in April-May 2014 from pastures in Mersin District. Larval stages of D. dendriticum were identified under a light microscope. Hepatopancreas from naturally infected H. aspersa snails were examined histologically. The prevalence of larval stages of D. dendriticum and Brachylaima sp. in H. aspersa snails was found to be 2.4% and 1.9%, respectively, in Mersin, Turkey. Cercariae were not matured in sporocysts at the beginning of April; however, it was observed that cercariae matured and started to leave sporocysts by early-May. Thus, it was concluded that H. aspersa acts as an intermediate host to D. dendriticumin and Brachylaima sp. in Mersin, Turkey. A digenean trematode Brachylaima sp. was seen for the first time in Turkey.

Host density increases parasite recruitment but decreases host risk in a snail-trematode system.

PubMed

Buck, J C; Hechinger, R F; Wood, A C; Stewart, T E; Kuris, A M; Lafferty, K D

2017-08-01

Most species aggregate in local patches. High host density in patches increases contact rate between hosts and parasites, increasing parasite transmission success. At the same time, for environmentally transmitted parasites, high host density can decrease infection risk to individual hosts, because infective stages are divided among all hosts in a patch, leading to safety in numbers. We tested these predictions using the California horn snail, Cerithideopsis californica (=Cerithidea californica), which is the first intermediate host for at least 19 digenean trematode species in California estuaries. Snails become infected by ingesting trematode eggs or through penetration by free-swimming miracidia that hatch from trematode eggs deposited with final-host (bird or mammal) feces. This complex life cycle decouples infective-stage production from transmission, raising the possibility of an inverse relationship between host density and infection risk at local scales. In a field survey, higher snail density was associated with increased trematode (infected snail) density, but decreased trematode prevalence, consistent with either safety in numbers, parasitic castration, or both. To determine the extent to which safety in numbers drove the negative snail-density-trematode-prevalence association, we manipulated uninfected snail density in 83 cages at eight sites within Carpinteria Salt Marsh (California, USA). At each site, we quantified snail density and used data on final-host (bird and raccoon) distributions to control for between-site variation in infective-stage supply. After three months, overall trematode infections per cage increased with snail biomass density. For egg-transmitted trematodes, per-snail infection risk decreased with snail biomass density in the cage and surrounding area, whereas per-snail infection risk did not decrease for miracidium-transmitted trematodes. Furthermore, both trematode recruitment and infection risk increased with infective-stage input, but this was significant only for miracidium-transmitted species. A model parameterized with our experimental results and snail densities from 524 field transects estimated that safety in numbers, when combined with patchy host density, halved per capita infection risk in this snail population. We conclude that, depending on transmission mode, host density can enhance parasite recruitment and reduce per capita infection risk. © 2017 by the Ecological Society of America.

Host density increases parasite recruitment but decreases host risk in a snail-trematode system

USGS Publications Warehouse

Buck, Julia C; Hechinger, R.F.; Wood, A.C.; Stewart, T.E.; Kuris, A.M.; Lafferty, Kevin D.

2017-01-01

Most species aggregate in local patches. High host density in patches increases contact rate between hosts and parasites, increasing parasite transmission success. At the same time, for environmentally-transmitted parasites, high host density can decrease infection risk to individual hosts, because infective stages are divided among all hosts in a patch, leading to safety in numbers. We tested these predictions using the California horn snail, Cerithideopsis californica (=Cerithidea californica), which is the first intermediate host for at least 19 digenean trematode species in California estuaries. Snails become infected by ingesting trematode eggs or through penetration by free-swimming miracidia that hatch from trematode eggs deposited with final-host (bird or mammal) feces. This complex life cycle decouples infective-stage production from transmission, raising the possibility of an inverse relationship between host density and infection risk. In a field survey, higher snail density was associated with increased trematode (infected snail) density, but decreased trematode prevalence, consistent with either safety in numbers, parasitic castration, or both. To determine the extent to which safety in numbers drove the negative snail density-trematode prevalence association, we manipulated uninfected snail density in 83 cages at eight sites within Carpinteria Salt Marsh (CA, USA). At each site, we quantified snail density and used data on final-host (bird and raccoon) distributions to control for between-site variation in infective-stage supply. After three months, overall trematode infections per cage increased with snail-biomass density. For egg-transmitted trematodes, per-snail infection risk decreased with snail-biomass density in the cage and surrounding area, whereas per-snail infection risk did not decrease for miracidium-transmitted trematodes. Furthermore, both trematode recruitment and infection risk increased with infective-stage input, but this was significant only for miracidium-transmitted species. A model parameterized with our experimental results and snail densities from 524 field transects estimated that safety in numbers, when combined with host aggregation, halved per-capita infection risk in this snail population. We conclude that, depending on transmission mode, host density can enhance parasite recruitment and reduce per-capita infection risk.

Female biased sex-ratio in Schistosoma mansoni after exposure to an allopatric intermediate host strain of Biomphalaria glabrata.

PubMed

Lepesant, Julie M J; Boissier, Jérôme; Climent, Déborah; Cosseau, Céline; Grunau, Christoph

2013-10-01

For parasites that require multiple hosts to complete their development, the interaction with the intermediate host may have an impact on parasite transmission and development in the definitive host. The human parasite Schistosoma mansoni needs two different hosts to complete its life cycle: the freshwater snail Biomphalaria glabrata (in South America) as intermediate host and a human or rodents as final host. To investigate the influence of the host environment on life history traits in the absence of selection, we performed experimental infections of two B. glabrata strains of different geographic origin with the same clonal population of S. mansoni. One B. glabrata strain is the sympatric host and the other one the allopatric host. We measured prevalence in the snail, the cercarial infectivity, sex-ratio, immunopathology in the final host and microsatellite frequencies of individual larvae in three successive generations. We show that, even if the parasite population is clonal based on neutral markers, S. mansoni keeps the capacity of generating phenotypic plasticity and/or variability for different life history traits when confront to an unusual environment, in this study the intermediate host. The most dramatic change was observed in sex-ratio: in average 1.7 times more female cercariae were produced when the parasite developed in an allopatric intermediate host. Copyright © 2013 Elsevier Inc. All rights reserved.

Epidemiology of cercarial stage of trematodes in freshwater snails from Chiang Mai province, Thailand

PubMed Central

Chontananarth, Thapana; Wongsawad, Chalobol

2013-01-01

Objective To investigate the epidemiological situation of cercarial trematodes infection in freshwater snails from different water resources in Chiang Mai province, Thailand. Methods The snail specimens were collected from 13 districts of Chiang Mai province during April 2008 to February 2012. The prevalence of cercarial infection in snails was investigated using the crushing method. The drawing was done with the help of a camera lucida for the morphological study. Results A total of 2 479 snail individuals were collected and classified into 7 families, 11 genera, and 14 species, Among them, 8 snails species were found to be infected with an overall prevalence of 17.27% (428/2 479), which infected with nine groups of cercariae; gymnocephalous cercaria, strigea cercaria, megalurous cercaria, monostome cercaria, parapleurolophocercous cercaria (Haplorchis cercaria), pleurolophocercous cercaria, furcocercous cercaria (Transversotrema cercaria), xiphidiocercaria, and virgulate cercaria. The parapleurolophocercous cercaria was found to be the dominant type among the cercarial infection in the snails (64.25%). Conclusions The various species of snails found in the research location act as the intermediate hosts for the high prevalence of parasitic infection of many species of mammals. This work will provide new information on both the distribution and first intermediate host of trematodes. PMID:23620846

Metagonimoides oregonensis (Heterophyidae: Digenea) infection in Pleurocerid snails and Desmognathus quadramaculatus salamander larvae in Southern Appalachian streams.

PubMed

Belden, Lisa K; Peterman, William E; Smith, Stephen A; Brooks, Lauren R; Benfield, E F; Black, Wesley P; Yang, Zhaomin; Wojdak, Jeremy M

2012-08-01

Metagonimoides oregonensis (Heterophyidae) is a little-known digenetic trematode that uses raccoons and possibly mink as definitive hosts, and stream snails and amphibians as intermediate hosts. Some variation in the life cycle and adult morphology in western and eastern populations has been previously noted. In the southern Appalachians, Pleurocera snails and stream salamanders, e.g., Desmognathus spp., are used as intermediate hosts in the life cycle. We completed a series of studies in this system examining some aspects of larval trematode morphology and first and second intermediate host use. Molecular sequencing of the 28S rDNA of cercariae in our survey placed them clearly within the heterophyid family. However, light and scanning electron microscopy revealed both lateral and dorso-ventral finfolds on the cercariae in our region, whereas original descriptions of M. oregonensis cercariae from the west coast indicate only a dorso-ventral finfold, so further work on the systematics of this group may be warranted. A survey of first intermediate host, Pleurocera proxima, from 7 streams in the region identified only M. oregonensis, virgulate-type cercariae, and cotylomicrocercous-type cercariae in the streams, with M. oregonensis having the highest prevalence, and the only type present that use amphibians as second intermediate hosts. Based on clearing and staining of 6 Desmognathus quadramaculatus salamander larvae, we found that individual salamanders could have over 600 metacercariae, which form between muscle fibers throughout the body. Histological observations suggest that the metacercariae do not cause excessive tissue damage or inflammation, and likely persist through metamorphosis, thereby transmitting potentially large numbers of worms to definitive host raccoons foraging along streams.

Hydrology and density feedbacks control the ecology of intermediate hosts of schistosomiasis across habitats in seasonal climates

PubMed Central

Perez-Saez, Javier; Mande, Theophile; Ceperley, Natalie; Bertuzzo, Enrico; Mari, Lorenzo; Rinaldo, Andrea

2016-01-01

We report about field and theoretical studies on the ecology of the aquatic snails (Bulinus spp. and Biomphalaria pfeifferi) that serve as obligate intermediate hosts in the complex life cycle of the parasites causing human schistosomiasis. Snail abundance fosters disease transmission, and thus the dynamics of snail populations are critically important for schistosomiasis modeling and control. Here, we single out hydrological drivers and density dependence (or lack of it) of ecological growth rates of local snail populations by contrasting novel ecological and environmental data with various models of host demography. Specifically, we study various natural and man-made habitats across Burkina Faso’s highly seasonal climatic zones. Demographic models are ranked through formal model comparison and structural risk minimization. The latter allows us to evaluate the suitability of population models while clarifying the relevant covariates that explain empirical observations of snail abundance under the actual climatic forcings experienced by the various field sites. Our results link quantitatively hydrological drivers to distinct population dynamics through specific density feedbacks, and show that statistical methods based on model averaging provide reliable snail abundance projections. The consistency of our ranking results suggests the use of ad hoc models of snail demography depending on habitat type (e.g., natural vs. man-made) and hydrological characteristics (e.g., ephemeral vs. permanent). Implications for risk mapping and space-time allocation of control measures in schistosomiasis-endemic contexts are discussed. PMID:27162339

Hydrology and density feedbacks control the ecology of intermediate hosts of schistosomiasis across habitats in seasonal climates.

PubMed

Perez-Saez, Javier; Mande, Theophile; Ceperley, Natalie; Bertuzzo, Enrico; Mari, Lorenzo; Gatto, Marino; Rinaldo, Andrea

2016-06-07

We report about field and theoretical studies on the ecology of the aquatic snails (Bulinus spp. and Biomphalaria pfeifferi) that serve as obligate intermediate hosts in the complex life cycle of the parasites causing human schistosomiasis. Snail abundance fosters disease transmission, and thus the dynamics of snail populations are critically important for schistosomiasis modeling and control. Here, we single out hydrological drivers and density dependence (or lack of it) of ecological growth rates of local snail populations by contrasting novel ecological and environmental data with various models of host demography. Specifically, we study various natural and man-made habitats across Burkina Faso's highly seasonal climatic zones. Demographic models are ranked through formal model comparison and structural risk minimization. The latter allows us to evaluate the suitability of population models while clarifying the relevant covariates that explain empirical observations of snail abundance under the actual climatic forcings experienced by the various field sites. Our results link quantitatively hydrological drivers to distinct population dynamics through specific density feedbacks, and show that statistical methods based on model averaging provide reliable snail abundance projections. The consistency of our ranking results suggests the use of ad hoc models of snail demography depending on habitat type (e.g., natural vs. man-made) and hydrological characteristics (e.g., ephemeral vs. permanent). Implications for risk mapping and space-time allocation of control measures in schistosomiasis-endemic contexts are discussed.

The role of light and gravity in the experimental transmission of Echinostoma caproni (Digenea: Echinostomatidae) cercariae to the second intermediate host, Biomphalaria glabrata (Gastropoda: Pulmonata).

PubMed

Platt, Thomas R; Burnside, Lindsay; Bush, Elizabeth

2009-06-01

Trematode cercariae inhabit predictable environments and respond to trigger cues with genetically fixed releaser responses when foraging for the upstream host. The effect of light and gravity on the transmission of Echinostoma caproni cercariae to Biomphalaria glabrata was investigated experimentally. Transmission chambers were constructed of clear polyvinyl chloride pipe. Snails were constrained within the chamber to prevent movement, while permitting the cercariae to swim freely. A trial consisted of 2 infected B. glabrata shedding E. caproni cercariae placed at the center of the chamber, with 5 uninfected B. glabrata placed 10 cm on either side (or above and below) of the shedding snails as sentinels. There was no significant difference in the prevalence of infection sentinel snails in either experiment (light vs. dark or top vs. bottom); however, mean intensity was significantly higher in sentinel snails in the dark portion of the chamber (42.5 vs. 10.4; P = 0.001) and the top of the transmission chamber (66.1 vs. 38.0; P = 0.0003). There was a high correlation between the number of metacercariae collected from sentinel snails and the total number of infective units (metacercariae + unsuccessful cercariae): r = 0.992 (light vs. dark) and r = 0.957 (top vs. bottom), respectively, at cercariae densities estimated from 22 to 3,304/L. The results suggest that cercariae of E. caproni exhibit negative photo- and geotaxis in searching for a second intermediate host. Stereotypical releaser responses to environmental trigger cues (light and gravity) allow E. caproni cercariae to exploit flexible strategies for completing the life cycle consistent with the broad range second intermediate and definitive hosts used by E. caproni cercariae and adults, respectively.

Highland cattle and Radix labiata, the hosts of Fascioloides magna

PubMed Central

2014-01-01

Background Fascioloides magna is a pathogenic fluke introduced to Europe ca 140 years ago. As it is spreading over the continent, new intermediate and definitive hosts might be involved in transmission of the parasite. In Europe, several studies reported potential new intermediate snail hosts (Radix spp.) for F. magna, and also several cases of fascioloidosis of wild and domestic animals were published. However, the data based on molecular and histological analyses confirming these findings remained unreported. This study aims to refer to unique findings of F. magna in European snails and domestic animals (the first observation in the Czech Republic in the last 30 years) and demonstrate the use of molecular techniques in determination of F. magna. Results Two snails of R. labiata naturally infected with F. magna were found; mature cercariae and daughter rediae were observed. Maturity of cercariae was checked by histological methods, however, their ability to encyst was not confirmed. Co-infection of F. magna and Fasciola hepatica in the liver of two highland cattle bulls was proved. Adult fasciolid flukes producing eggs were found in the liver pseudocysts (F. magna) and the bile ducts (F. hepatica). Identification of intermediate hosts, intramolluscan stages, adult flukes and eggs was performed by sequencing the ITS2 region. Connection of F. magna pseudocysts with the gut (via the bile ducts) was not confirmed by means of histological and coprological examinations. Conclusions For the first time, Radix labiata was confirmed as the snail host for F. magna under natural conditions and, together with the finding of F. magna infection in cattle, we can expect further transmission of F. magna from wildlife to livestock in localities shared by these hosts. PMID:24517409

Biompha-LAMP: A New Rapid Loop-Mediated Isothermal Amplification Assay for Detecting Schistosoma mansoni in Biomphalaria glabrata Snail Host.

PubMed

Gandasegui, Javier; Fernández-Soto, Pedro; Hernández-Goenaga, Juan; López-Abán, Julio; Vicente, Belén; Muro, Antonio

2016-12-01

Schistosomiasis remains one of the most common endemic parasitic diseases affecting over 230 million people worlwide. Schistosoma mansoni is the main species causing intestinal and hepatic schistosomiasis and the fresh water pulmonate snails of the genus Biomphalaria are best known for their role as intermediate hosts of the parasite. The development of new molecular monitoring assays for large-scale screening of snails from transmission sites to detect the presence of schistosomes is an important point to consider for snail control interventions related to schistosomiasis elimination. Our work was focussed on developing and evaluating a new LAMP assay combined with a simple DNA extraction method to detect S. mansoni in experimentally infected snails as a diagnostic tool for field conditions. A LAMP assay using a set of six primers targeting a sequence of S. mansoni ribosomal intergenic spacer 28S-18S rRNA was designed. The detection limit of the LAMP assay was 0.1 fg of S. mansoni DNA at 63°C for 50 minutes. LAMP was evaluated by examining S. mansoni DNA in B. glabrata snails experimentally exposed to miracidia at different times post-exposure: early prepatent period (before cercarial shedding), light infections (snails exposed to a low number of miracidia) and detection of infected snails in pooled samples (within a group of uninfected snails). DNA for LAMP assays was obtained by using a commercial DNA extraction kit or a simple heat NaOH extraction method. We detected S. mansoni DNA in all groups of snails by using no complicated requirement procedure for DNA obtaining. Our LAMP assay, named Biompha-LAMP, is specific, sensitive, rapid and potentially adaptable as a cost-effective method for screening of intermediate hosts infected with S. mansoni in both individual snails and pooled samples. The assay could be suitable for large-scale field surveys for schistosomes control campaigns in endemic areas.

Biompha-LAMP: A New Rapid Loop-Mediated Isothermal Amplification Assay for Detecting Schistosoma mansoni in Biomphalaria glabrata Snail Host

PubMed Central

Hernández-Goenaga, Juan; López-Abán, Julio; Vicente, Belén; Muro, Antonio

2016-01-01

Background Schistosomiasis remains one of the most common endemic parasitic diseases affecting over 230 million people worlwide. Schistosoma mansoni is the main species causing intestinal and hepatic schistosomiasis and the fresh water pulmonate snails of the genus Biomphalaria are best known for their role as intermediate hosts of the parasite. The development of new molecular monitoring assays for large-scale screening of snails from transmission sites to detect the presence of schistosomes is an important point to consider for snail control interventions related to schistosomiasis elimination. Our work was focussed on developing and evaluating a new LAMP assay combined with a simple DNA extraction method to detect S. mansoni in experimentally infected snails as a diagnostic tool for field conditions. Methodology/Principal findings A LAMP assay using a set of six primers targeting a sequence of S. mansoni ribosomal intergenic spacer 28S-18S rRNA was designed. The detection limit of the LAMP assay was 0.1 fg of S. mansoni DNA at 63°C for 50 minutes. LAMP was evaluated by examining S. mansoni DNA in B. glabrata snails experimentally exposed to miracidia at different times post-exposure: early prepatent period (before cercarial shedding), light infections (snails exposed to a low number of miracidia) and detection of infected snails in pooled samples (within a group of uninfected snails). DNA for LAMP assays was obtained by using a commercial DNA extraction kit or a simple heat NaOH extraction method. We detected S. mansoni DNA in all groups of snails by using no complicated requirement procedure for DNA obtaining. Conclusions/Significance Our LAMP assay, named Biompha-LAMP, is specific, sensitive, rapid and potentially adaptable as a cost-effective method for screening of intermediate hosts infected with S. mansoni in both individual snails and pooled samples. The assay could be suitable for large-scale field surveys for schistosomes control campaigns in endemic areas. PMID:27941967

Comparative Phylogenetic Studies on Schistosoma japonicum and Its Snail Intermediate Host Oncomelania hupensis: Origins, Dispersal and Coevolution

PubMed Central

Attwood, Stephen W.; Ibaraki, Motomu; Saitoh, Yasuhide; Nihei, Naoko; Janies, Daniel A.

2015-01-01

Background Schistosoma japonicum causes major public health problems in China and the Philippines; this parasite, which is transmitted by freshwater snails of the species Oncomelania hupensis, causes the disease intestinal schistosomiasis in humans and cattle. Researchers working on Schistosoma in Africa have described the relationship between the parasites and their snail intermediate hosts as coevolved or even as an evolutionary arms race. In the present study this hypothesis of coevolution is evaluated for S. japonicum and O. hupensis. The origins and radiation of the snails and the parasite across China, and the taxonomic validity of the sub-species of O. hupensis, are also assessed. Methodology/Principal Findings The findings provide no evidence for coevolution between S. japonicum and O. hupensis, and the phylogeographical analysis suggests a heterochronous radiation of the parasites and snails in response to different palaeogeographical and climatic triggers. The results are consistent with a hypothesis of East to West colonisation of China by Oncomelania with a re-invasion of Japan by O. hupensis from China. The Taiwan population of S. japonicum appears to be recently established in comparison with mainland Chinese populations. Conclusions/Significance The snail and parasite populations of the western mountain region of China (Yunnan and Sichuan) appear to have been isolated from Southeast Asian populations since the Pleistocene; this has implications for road and rail links being constructed in the region, which will breach biogeographical barriers between China and Southeast Asia. The results also have implications for the spread of S. japonicum. In the absence of coevolution, the parasite may more readily colonise new snail populations to which it is not locally adapted, or even new intermediate host species; this can facilitate its dispersal into new areas. Additional work is required to assess further the risk of spread of S. japonicum. PMID:26230619

[Experimental and epidemiological studies on the life cycle of Echinostoma hortense Asada, 1926 (Trematoda: Echinostomatidae)

PubMed

Ahn, Yung Kyum; Ryang, Yong Suk

1986-12-01

Recently there have been some reports on human infections of Echinostoma hortense in Korea. It was found that a few species of freshwater fishes were playing the role of the second intermediate host of E. hortense. However, molluscan intermediate host has not been identified yet in Korea. The present study aimed to establish the life cycle of E. hortense in laboratory. Experimental studies such as egg production from the rat, development of the eggs in vitro, exposure of miracidia to freshwater snails, shedding pattern of cercariae from infected snails, morphology of cercariae, cercarial infection to the second intermediate host and infection of metacercariae to the difinitive hosts were done. In addition, epidemiological surveys on the infection status in inhabitants and house rats, and on the natural infection of larval echinostomes in the snails and fishes were carried out along the South Hangang-river. The results obtained were as follows: The eggs deposited from adults in physiological saline were cultivated at room temperature (20-24C). The miracidia were firstly observed on 8 days after cultivation, and 85.5 per cent of the eggs contained the mature miracidia on 11 days after cultivation. More than 90 per cent formed the miracidia when cultivated at temperature 22-27C. Hatching of the miracidia began on 12 days after cultivation and continued for a week. The size of the miracidia was 103.0 x 51.4 micrometer in average. The motility of miracidia were active up to 8 hours after shedding, but they were all dead within 10 hours after shedding. A freshwater snail, Radix auricularia coreana was cultivated in aquaria. A hatched F1 snails from the egg masses were exposed to 20 miracidia respectively. Escape of cercariae started on 15 days after infection. Radix auricularia coreana was experimentally identified as the first intermediate host of E. hortense in Korea. Cercarial shedding started on 15-20 days after infection by snail, continued for about 10 days (8.8 days in average). Infected snails were dead within 32 days after the miracidial infection. About 1,335 cercariae (328-1,994) per snail were shed in its life, and 119 cercariae in average per snail per day were shed. The cercariae were motile for more than 24 hours, and then squirming at the bottom until death. The body and tail sizes of cercariae were 356 x 186 micrometer and 510 x 68 micrometer in average, respectively. The rediae parasitized in the snail hosts were found mainly around the pericardial regions, and their size was 1,575 x 258 micrometer in average. The numbers of developing cercariae in a mature redia were 14 in average (7-20 in range). The numbers of rediae in a snail were 102 in average on 15 days after miracidial infection and 221 in average on 28 days. Three uninfected Misgurnus anguillicaudatus, less than 6.5 cm long were used in for the cercaria1 infection. They were all exposed with 755 cercariae, and examined at 5-day intervals starting from 10 days after infection. All the fihes were infected with metacercariae of E. hortense and a total of 275 was found infected (36.4 per cent). The metacercariae were fed to rats and the adult worms were obtained on 15 days after infection. The infected rats began to deposit the eggs on 11 days after infection. The number of eggs deposited per day per worm (EPD/worm) was 400-500 on 3 weeks after infection and was increased to 1,000-1,500 on 4 to 17 weeks, then decreased to 800 on 2l weeks after infection. A total of 745 stool specimens collected from 576 male and 169 female residents of 8 different villages along South Hangang basin was examined. Out of 745 specimens, the eggs of Echinostoma sp. were found in 2 cases (0.3 per cent). Of 34 house rats one showed egg-positive (2.9 per cent). Total 971 Radix auricularia coreana collected from 7 sampling stations were examined for shedding of cercariae. Three snails (0.3 per cent) shed the cercariae of E. hortense. A total of 119 out of 542 freshwater fishes (22.0 per cent) had the metacercariae of E. hortense. The fishes parasitized with the metacercariae were 4 out of 14 examined species. The infection rate of 4 species were 34.1 per cent (106 out of 311) in Misgurnus anguillicaudatus, 30.4 per cent 7 out of 23) in Misgurnus mizolepis, 4.3 per cent (2 out of 46) in Moroco oxycephalus and 22.2 per cent (4 out of 18) in Odontobutis obscura interrupta. In summarizing the above results, the first intermediate host of E. hortense was found as Radix auricularia coreana in Korea. Also it took about 46 days for the shortest completion of a life cycle of E. hortense in summer; that is, 10 days for miracidial development in eggs, 15 days for cercarial development in the snail, about 10 days for metacercarial development in the second intermediate hosts, 11 days for the maturation as the adults in the definitive hosts. The natural infection rates of E. hortense in the intermediate hosts were relatively high but those in the definitive hosts were low in the middle areas of South Hangang basin.

Implications of Changing Temperatures on the Growth, Fecundity and Survival of Intermediate Host Snails of Schistosomiasis: A Systematic Review.

PubMed

Kalinda, Chester; Chimbari, Moses; Mukaratirwa, Samson

2017-01-13

Climate change has been predicted to increase the global mean temperature and to alter the ecological interactions among organisms. These changes may play critical roles in influencing the life history traits of the intermediate hosts (IHs). This review focused on studies and disease models that evaluate the potential effect of temperature rise on the ecology of IH snails and the development of parasites within them. The main focus was on IH snails of schistosome parasites that cause schistosomiasis in humans. A literature search was conducted on Google Scholar, EBSCOhost and PubMed databases using predefined medical subject heading terms, Boolean operators and truncation symbols in combinations with direct key words. The final synthesis included nineteen published articles. The studies reviewed indicated that temperature rise may alter the distribution, optimal conditions for breeding, growth and survival of IH snails which may eventually increase the spread and/or transmission of schistosomiasis. The literature also confirmed that the life history traits of IH snails and their interaction with the schistosome parasites are affected by temperature and hence a change in climate may have profound outcomes on the population size of snails, parasite density and disease epidemiology. We concluded that understanding the impact of temperature on the growth, fecundity and survival of IH snails may broaden the knowledge on the possible effects of climate change and hence inform schistosomiasis control programmes.

The Complete Mitochondrial Genome of Galba pervia (Gastropoda: Mollusca), an Intermediate Host Snail of Fasciola spp

PubMed Central

Huang, Wei-Yi; Zhao, Guang-Hui; Wei, Shu-Jun; Song, Hui-Qun; Xu, Min-Jun; Lin, Rui-Qing; Zhou, Dong-Hui; Zhu, Xing-Quan

2012-01-01

Complete mitochondrial (mt) genomes and the gene rearrangements are increasingly used as molecular markers for investigating phylogenetic relationships. Contributing to the complete mt genomes of Gastropoda, especially Pulmonata, we determined the mt genome of the freshwater snail Galba pervia, which is an important intermediate host for Fasciola spp. in China. The complete mt genome of G. pervia is 13,768 bp in length. Its genome is circular, and consists of 37 genes, including 13 genes for proteins, 2 genes for rRNA, 22 genes for tRNA. The mt gene order of G. pervia showed novel arrangement (tRNA-His, tRNA-Gly and tRNA-Tyr change positions and directions) when compared with mt genomes of Pulmonata species sequenced to date, indicating divergence among different species within the Pulmonata. A total of 3655 amino acids were deduced to encode 13 protein genes. The most frequently used amino acid is Leu (15.05%), followed by Phe (11.24%), Ser (10.76%) and IIe (8.346%). Phylogenetic analyses using the concatenated amino acid sequences of the 13 protein-coding genes, with three different computational algorithms (maximum parsimony, maximum likelihood and Bayesian analysis), all revealed that the families Lymnaeidae and Planorbidae are closely related two snail families, consistent with previous classifications based on morphological and molecular studies. The complete mt genome sequence of G. pervia showed a novel gene arrangement and it represents the first sequenced high quality mt genome of the family Lymnaeidae. These novel mtDNA data provide additional genetic markers for studying the epidemiology, population genetics and phylogeographics of freshwater snails, as well as for understanding interplay between the intermediate snail hosts and the intra-mollusca stages of Fasciola spp.. PMID:22844544

Fasciola hepatica in Cuba: compatibility of different isolates with two intermediate snail hosts, Galba cubensis and Pseudosuccinea columella.

PubMed

Vázquez, A A; Sánchez, J; Pointier, J-P; Théron, A; Hurtrez-Boussès, S

2014-12-01

In Cuba, only two lymnaeid snails, Galba cubensis and Pseudosuccinea columella, with different ecology and distribution patterns, are intermediate hosts for Fasciola hepatica. The compatibility of these two species as hosts was analysed through their rates of infection, the production of rediae and survivorship when exposed to F. hepatica miracidia. Ten populations of G. cubensis, eight of P. columella collected from various habitats and six isolates of F. hepatica sampled in slaughterhouses from different localities were tested. Our results clearly demonstrate that G. cubensis is a more compatible host for F. hepatica in Cuba when compared with P. columella. However, the role that P. columella may have in fascioliasis transmission under certain conditions should not be disregarded. Variation in infectivity among isolates of F. hepatica were also observed and may explain why some regions in Cuba are more commonly subjected to fascioliasis outbreaks.

Host quality and spatial patterning in infections of the Eastern mudsnail (Ilyanassa obsoleta) by two trematodes (Himasthla quissetensis and Zoogonus rubellus).

PubMed

Rossiter, Wayne; Sukhdeo, Michael V K

2012-04-01

Several studies have suggested that the fitness of a parasite can be directly impacted by the quality of its host. In such cases, selective pressures could act to funnel parasites towards the highest-quality hosts in a population. The results of this study demonstrate that snail host quality is strongly correlated with spatial patterning in trematode infections and that habitat type is the underlying driver for both of these variables. Two trematodes (Himasthla quissetensis and Zoogonus rubellus) with very different life cycles assume the same spatial infection pattern in populations of the first intermediate host (Ilyanassa obsoleta) in coastal marsh habitats. Infected snails are disproportionately recovered from intertidal panne habitats, which offer more hospitable environs for snails than do adjacent habitats (intertidal creeks, coastal flats, and subtidal creeks), in terms of protection from turbulence and wave action, as well as the availability of food stuffs. Snails in intertidal panne habitats are of higher quality when assessed in terms of average size-specific mass, growth rate, and fecundity. In mark-recapture experiments, snails frequently dispersed into intertidal pannes but were never observed leaving them. In addition, field experiments demonstrate that snails confined to intertidal panne habitats are disproportionately infected by both trematode species, relative to conspecifics confined to adjacent habitats. Laboratory experiments show that infected snails suffer significant energetic losses and consume more than uninfected conspecifics, suggesting that infected snails in intertidal pannes may survive better than in adjacent habitats. We speculate that 1 possible mechanism for the observed patterns is that the life cycles of both trematode species allows them to contact the highest-quality snails in this marsh ecosystem.

Internal movement of estuarine digenetic trematodes through their intermediate snail host Cerithidea californica.

PubMed

Oates, Jessica; Fingerut, Jonathan

2011-12-01

The ability of free-swimming larval parasites to control emergence from their hosts can be critical in increasing the chances of successful infection transmission. For a group of estuarine trematodes, emergence of cercariae from their snail hosts is known to match favorable temperature, tidal activity, and light intensity. How the larvae time this behavior is not well understood, but the pathway that the larvae take through their host may play a role. Through video and histological analysis, we were able to identify the snail's anus as the emergence point and the peri-intestinal sinus dorsal to the intestines as the route by which they reach that point. By moving through this open sinus, the larvae have an energetically efficient pathway to reach their emergence point while minimizing damage to the host. Most importantly, it allows control over emergence to be maintained by the parasite, not the host, thus increasing the chances of the larva successfully reaching its intended destination.

Geographic distribution of Angiostrongylus cantonensis in wild rats (Rattus rattus) and terrestrial snails in Florida, USA

PubMed Central

Slapcinsky, John D.; Roff, Shannon; Mendieta Calle, Jorge; Diaz Goodwin, Zakia; Stern, Jere; Corlett, Rachel; Conway, Julia; McIntosh, Antoinette

2017-01-01

The parasitic nematode Angiostrongylus cantonensis is a major cause of eosinophilic meningitis in humans, and has been documented in other incidental hosts such as birds, horses, dogs and non-human primates. It is endemic in Hawaii, and there have been sporadic reports in the southern continental United States. This parasite uses rats as definitive hosts and snails as intermediate hosts. In this study, we collected potential definitive and intermediate hosts throughout Florida to ascertain the geographic distribution in the state: Rats, environmental rat fecal samples, and snails were collected from 18 counties throughout the state. Classical diagnostics and morphological identification, along with molecular techniques were used to identify nematode species and confirm the presence of A. cantonensis. Of the 171 Rattus rattus collected, 39 (22.8%) were positive for A. cantonensis, and 6 of the 37 (16.2%) environmental rat fecal samples collected in three of the surveyed counties were also positive for this parasite by real time PCR. We examined 1,437 gastropods, which represented 32 species; 27 (1.9%) were positive for A. cantonensis from multiple sites across Florida. Three non-native gastropod species, Bradybaena similaris, Zachrysia provisoria, and Paropeas achatinaceum, and three native gastropod species, Succinea floridana, Ventridens demissus, and Zonitoides arboreus, which are newly recorded intermediate hosts for the parasite, were positive for A. cantonensis. This study indicates that A. cantonensis is established in Florida through the finding of adult and larval stages in definitive and intermediate hosts, respectively, throughout the state. The ability for this historically subtropical nematode to thrive in a more temperate climate is alarming, however as the climate changes and average temperatures rise, gastropod distributions will probably expand, leading to the spread of this parasite in more temperate areas. Through greater awareness of host species and prevalence of A. cantonensis in the United States, potential accidental infections may be avoided. PMID:28542310

Effects of Schistosoma haematobium infection on reproductive success and male outcrossing ability in the simultaneous hermaphrodite, Bulinus truncatus (Gastropoda: Planorbidae).

PubMed

Schrag, S J; Rollinson, D

1994-01-01

The schistosome intermediate snail host, Bulinus truncatus (Mollusca: Planorbidae), has two reproductive (phally) morphs. Both aphallics and euphallics can self-fertilize, but aphallics cannot donate sperm because they do not develop a functional penis and prostate. This study investigated the interactions between phally and fitness consequences of Schistosoma haematobium infection in B. truncatus. Snails which developed patent infections produced 26% fewer eggs than controls and 35% fewer eggs than exposed snails which did not develop infections. This reduction was due to a lower lifetime production of egg masses and a smaller mean number of eggs/mass in infected snails relative to control or exposed snails. However, there was no evidence of increased mortality in infected snails. Contrary to reports of fecundity compensation in other intermediate host snails, egg production post-exposure during the pre-patent period did not increase relative to that of controls in either infected or exposed snails. Phally did not influence susceptibility to infection or length of the prepatent period. Furthermore, lifetime egg, egg mass and hatchling production, as well as mean eggs/mass and number of hatchlings reaching maturity, did not differ significantly between aphallics and euphallics within control of exposed experimental groups. However, within the infected group euphallics produced 38% fewer eggs, smaller egg masses, and fewer hatchlings reaching maturity than aphallics, supporting the prediction of a cost to the growth and maintenance of a full male tract. This cost was detectable only when snails were under the stress of infection. The proportion of euphallic offspring produced did not differ across experimental groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative PCR estimates Angiostrongylus cantonensis (rat lungworm) infection levels in semi-slugs (Parmarion martensi)

PubMed Central

Jarvi, Susan I.; Farias, Margaret E.M.; Howe, Kay; Jacquier, Steven; Hollingsworth, Robert; Pitt, William

2013-01-01

The life cycle of the nematode Angiostrongylus cantonensis involves rats as the definitive host and slugs and snails as intermediate hosts. Humans can become infected upon ingestion of intermediate or paratenic (passive carrier) hosts containing stage L3 A. cantonensis larvae. Here, we report a quantitative PCR (qPCR) assay that provides a reliable, relative measure of parasite load in intermediate hosts. Quantification of the levels of infection of intermediate hosts is critical for determining A. cantonensis intensity on the Island of Hawaii. The identification of high intensity infection ‘hotspots’ will allow for more effective targeted rat and slug control measures. qPCR appears more efficient and sensitive than microscopy and provides a new tool for quantification of larvae from intermediate hosts, and potentially from other sources as well. PMID:22902292

Infection with schistosome parasites in snails leads to increased predation by prawns: implications for human schistosomiasis control.

PubMed

Swartz, Scott J; De Leo, Giulio A; Wood, Chelsea L; Sokolow, Susanne H

2015-12-01

Schistosomiasis - a parasitic disease that affects over 200 million people across the globe - is primarily transmitted between human definitive hosts and snail intermediate hosts. To reduce schistosomiasis transmission, some have advocated disrupting the schistosome life cycle through biological control of snails, achieved by boosting the abundance of snails' natural predators. But little is known about the effect of parasitic infection on predator-prey interactions, especially in the case of schistosomiasis. Here, we present the results of laboratory experiments performed on Bulinus truncatus and Biomphalaria glabrata snails to investigate: (i) rates of predation on schistosome-infected versus uninfected snails by a sympatric native river prawn, Macrobrachium vollenhovenii, and (ii) differences in snail behavior (including movement, refuge-seeking and anti-predator behavior) between infected and uninfected snails. In predation trials, prawns showed a preference for consuming snails infected with schistosome larvae. In behavioral trials, infected snails moved less quickly and less often than uninfected snails, and were less likely to avoid predation by exiting the water or hiding under substrate. Although the mechanism by which the parasite alters snail behavior remains unknown, these results provide insight into the effects of parasitic infection on predator-prey dynamics and suggest that boosting natural rates of predation on snails may be a useful strategy for reducing transmission in schistosomiasis hotspots. © 2015. Published by The Company of Biologists Ltd.

EGG-HATCHING MECHANISM OF HUMAN LIVER FLUKE, OPISTHORCHIS VIVERRINI: A ROLE FOR LEUCINE AMINOPEPTIDASES FROM THE SNAIL HOST, BITHYNIA SIAMENSIS GONIOMPHALOS.

PubMed

Tesana, Smarn; Khampoosa, P; Piratae, S; Prasopdee, S; Sripanidkulchai, B

2018-05-08

The human liver fluke Opisthorchis viverrini (Platyhelminthes, Trematoda, Digenea) uses snails of the genus Bithynia as first intermediate host. Peculiarly among trematodes, the eggs of O. viverrini hatch within the digestive tract of its snail host. It remains uncertain whether hatching in this species is mediated through mechanical fracture of the eggshell or by digestion with specific digestive enzymes. This study aimed to characterize enzymes with specific inhibitor and factors involved in the hatching activity of O. viverrini eggs. For measuring egg hatching in vivo, 50 O. viverrini mature eggs were fed to individual Bithynia siamensis goniomphalos snail at various temperature conditions for 24 hrs. Ex vivo, mature eggs were incubated with crude snail extract and commercial leucine aminopeptidase (LAP). Egg-hatching of O. viverrini was temperature dependent, with optimal hatching occurring at 24-28 C, with a peak of hatching of 93.54% in vivo and 30.55% ex vivo occurring at these temperatures. Ex vivo hatching rates increased to 45.87% under anaerobic conditions at 28 C. Some 22.70% and 16.21% of heat-killed eggs also hatched within the snail digestive tract and snail extract, respectively, indicating that host molecules are involved in the hatching response. Most eggs hatch in the anterior regions of the digestive tract. Hatching was completely inhibited in the presence of bestatin, an inhibitor of leucine aminopeptidase (LAP), but not in the presence of phosphatase inhibitors. Bestatin inhibition of hatching was reversible. Finally, egg hatching could be induced by addition of a porcine LAP. The results indicate that this digenean utilizes both LAP of the snail host and movement of miracidia for hatching.

Toxic effects of chromium on Schistosoma haematobium miracidia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolmarans, C.T.; Yssel, E.; Hamilton-Attwell, V.L.

1988-12-01

Various heavy metals have recently been evaluated as molluscicides for freshwater snails, which act as intermediate hosts of trematode parasites of medical or veterinary importance. Very little information, however, is available on heavy metals that may be suitable to eliminate the parasites as such. Suitable compounds should also inhibit the penetration ability of parasites as well as stunt the development of those who do not penetrate their hosts. In the light of these requirements, the present study evaluated the effect of chromium on the miracidia of Schistosoma haematobium, which causes urinary bilharzia. Attention was mainly focused on (1) the chromiummore » concentration which resulted in 100% mortality (2) the effect of chromium on the external and internal morphology of the miracidia, and (3) the ability of the miracidia to form sporocytes in vitro and in vivo and to penetrate their intermediate host snail, Bulinus africanus.« less

Histamine Immunoreactive Elements in the Central and Peripheral Nervous Systems of the Snail, Biomphalaria spp., Intermediate Host for Schistosoma mansoni

PubMed Central

Habib, Mohamed R.; Mohamed, Azza H.; Osman, Gamalat Y.; Sharaf El-Din, Ahmed T.; Mossalem, Hanan S.; Delgado, Nadia; Torres, Grace; Rolón-Martínez, Solymar; Miller, Mark W.; Croll, Roger P.

2015-01-01

Histamine appears to be an important transmitter throughout the Animal Kingdom. Gastropods, in particular, have been used in numerous studies establishing potential roles for this biogenic amine in the nervous system and showing its involvement in the generation of diverse behaviours. And yet, the distribution of histamine has only previously been described in a small number of molluscan species. The present study examined the localization of histamine-like immunoreactivity in the central and peripheral nervous systems of pulmonate snails of the genus Biomphalaria. This investigation demonstrates immunoreactive cells throughout the buccal, cerebral, pedal, left parietal and visceral ganglia, indicative of diverse regulatory functions in Biomphalaria. Immunoreactivity was also present in statocyst hair cells, supporting a role for histamine in graviception. In the periphery, dense innervation by immunoreactive fibers was observed in the anterior foot, perioral zone, and other regions of the body wall. This study thus shows that histamine is an abundant transmitter in these snails and its distribution suggest involvement in numerous neural circuits. In addition to providing novel subjects for comparative studies of histaminegic neurons in gastropods, Biomphalaria is also the major intermediate host for the digenetic trematode parasite, which causes human schistosomiasis. The study therefore provides a foundation for understanding potential roles for histamine in interactions between the snail hosts and their trematode parasites. PMID:26086611

Multi-host model and threshold of intermediate host Oncomelania snail density for eliminating schistosomiasis transmission in China.

PubMed

Zhou, Yi-Biao; Chen, Yue; Liang, Song; Song, Xiu-Xia; Chen, Geng-Xin; He, Zhong; Cai, Bin; Yihuo, Wu-Li; He, Zong-Gui; Jiang, Qing-Wu

2016-08-18

Schistosomiasis remains a serious public health issue in many tropical countries, with more than 700 million people at risk of infection. In China, a national integrated control strategy, aiming at blocking its transmission, has been carried out throughout endemic areas since 2005. A longitudinal study was conducted to determine the effects of different intervention measures on the transmission dynamics of S. japonicum in three study areas and the data were analyzed using a multi-host model. The multi-host model was also used to estimate the threshold of Oncomelania snail density for interrupting schistosomiasis transmission based on the longitudinal data as well as data from the national surveillance system for schistosomiasis. The data showed a continuous decline in the risk of human infection and the multi-host model fit the data well. The 25th, 50th and 75th percentiles, and the mean of estimated thresholds of Oncomelania snail density below which the schistosomiasis transmission cannot be sustained were 0.006, 0.009, 0.028 and 0.020 snails/0.11 m(2), respectively. The study results could help develop specific strategies of schistosomiasis control and elimination tailored to the local situation for each endemic area.

Natural infection of the feline lungworm Aelurostrongylus abstrusus in the invasive snail Achatina fulica from Argentina.

PubMed

Valente, Romina; Diaz, Julia Ines; Salomón, Oscar Daniel; Navone, Graciela Teresa

2017-02-15

The giant African snail Achatina fulica is an invasive mollusk native to Africa, the first record in Argentina was in Puerto Iguazú, in northeastern Argentina in 2010. Recently it was reported in Corrientes Province. This snail can act as an intermediate host of Metastrongyloidea nematodes of importance in public health as: Angiostrongylus cantonensis, Angiostrongylus costaricensis and Angiostrongylus vasorum. Taking into account the presence of A. fulica in Argentina, the objectives of this study is to assess the presence of Metastrongyloidea nematodes in this mollusk species in Puerto Iguazú, Misiones, close to the international border with Brazil and Paraguay. A total of 451 samples were collected from February 2014 to November 2015. The snails were processed using a digestion technique to recover the parasites. A total of 206 nematodes larvae were founded in the digestion solution of 10 hosts (P=2%; MA=0.5; MI=21). Third larval stage (L3) nematodes identified as Aelurostrongylus abstrusus were founded parasitizing the snails. No other larval stage was observed. This species has veterinary importance because it causes 'aelurostrongilosis', also known as feline strongyloidosis. This study constitutes the first record of a Metastrongyloidea nematode in A. fulica in Argentina and also highlights the susceptibility of this mollusk as intermediate host of other helminthes of health importance. The present study suggests that there is a need to establish an epidemiological monitoring system in order to prevent the possible installation of an infected mollusks focus. Copyright © 2017 Elsevier B.V. All rights reserved.

Reproduction and caste ratios under stress in trematode colonies with a division of labour.

PubMed

Lloyd, Melanie M; Poulin, Robert

2013-06-01

Trematodes form clonal colonies in their first intermediate host. Individuals are, depending on species, rediae or sporocysts (which asexually reproduce) and cercariae (which develop within rediae or sporocysts and infect the next host). Some species use a division of labour within colonies, with 2 distinct redial morphs: small rediae (non-reproducing) and large rediae (individuals which produce cercariae). The theory of optimal caste ratio predicts that the ratio of caste members (small to large rediae) responds to environmental variability. This was tested in Philophthalmus sp. colonies exposed to host starvation and competition with the trematode, Maritrema novaezealandensis. Philophthalmus sp. infected snails, with and without M. novaezealandensis, were subjected to food treatments. Reproductive output, number of rediae, and the ratio of small to large rediae were compared among treatments. Philophthalmus sp. colonies responded to host starvation and competition; reproductive output was higher in well-fed snails of both infection types compared with snails in lower food treatments and well-fed, single infected snails compared with well-fed double infected snails. Furthermore, the caste ratio in Philophthalmus sp. colonies was altered in response to competition. This is the first study showing caste ratio responses to environmental pressures in trematodes with a division of labour.

Phylogenetic relationships of some species of the family Echinostomatidae Odner, 1910 (Trematoda), inferred from nuclear rDNA sequences and karyological analysis.

PubMed

Stanevičiūtė, Gražina; Stunžėnas, Virmantas; Petkevičiūtė, Romualda

2015-01-01

The family Echinostomatidae Looss, 1899 exhibits a substantial taxonomic diversity, morphological criteria adopted by different authors have resulted in its subdivision into an impressive number of subfamilies. The status of the subfamily Echinochasminae Odhner, 1910 was changed in various classifications. Genetic characteristics and phylogenetic analysis of four Echinostomatidae species - Echinochasmus sp., Echinochasmuscoaxatus Dietz, 1909, Stephanoprorapseudoechinata (Olsson, 1876) and Echinoparyphiummordwilkoi Skrjabin, 1915 were obtained to understand well enough the homogeneity of the Echinochasminae and phylogenetic relationships within the Echinostomatidae. Chromosome set and nuclear rDNA (ITS2 and 28S) sequences of parthenites of Echinochasmus sp. were studied. The karyotype of this species (2n=20, one pair of large bi-armed chromosomes and others are smaller-sized, mainly one-armed, chromosomes) differed from that previously described for two other representatives of the Echinochasminae, Echinochasmusbeleocephalus (von Linstow, 1893), 2n=14, and Episthmiumbursicola (Creplin, 1937), 2n=18. In phylogenetic trees based on ITS2 and 28S datasets, a well-supported subclade with Echinochasmus sp. and Stephanoprorapseudoechinata clustered with one well-supported clade together with Echinochasmusjaponicus Tanabe, 1926 (data only for 28S) and Echinochasmuscoaxatus. These results supported close phylogenetic relationships between Echinochasmus Dietz, 1909 and Stephanoprora Odhner, 1902. Phylogenetic analysis revealed a clear separation of related species of Echinostomatoidea restricted to prosobranch snails as first intermediate hosts, from other species of Echinostomatidae and Psilostomidae, developing in Lymnaeoidea snails as first intermediate hosts. According to the data based on rDNA phylogeny, it was supposed that evolution of parasitic flukes linked with first intermediate hosts. Digeneans parasitizing prosobranch snails showed higher dynamic of karyotype evolution provided by different chromosomal rearrangements including Robertsonian translocations and pericentric inversions than more stable karyotype of digenean worms parasitizing lymnaeoid pulmonate snails.

Behavioural responses of the snail Lymnaea acuminata to carbohydrates in snail-attractant pellets

NASA Astrophysics Data System (ADS)

Tiwari, Farindra; Singh, D. K.

Snail control is one of the most important tools in the campaign to reduce the incidence of fascioliasis. In order to attain this objective, the method of bait formulation in order to contain an attractant and a molluscicide is an expedient approach to lure the target snail population to the molluscicide. This study identifies certain carbohydrates, namely sucrose, maltose, glucose, fructose and starch, for preparing such baits. These were tested on Lymnaea acuminata, an intermediate host of the digenean trematodes Fasciola hepatica and Fasciola gigantica. The behavioural responses of snails to these carbohydrates were examined. Significant variations in behavioural responses were observed in the snail even when the five carbohydrates were used in low concentrations in snail-attractant pellets. Starch emerged as the strongest attractant for Lymnaea acuminata, followed by maltose.

Host diversity begets parasite diversity: bird final hosts and trematodes in snail intermediate hosts

USGS Publications Warehouse

Hechinger, R.F.; Lafferty, K.D.

2005-01-01

It is postulated that disease is a product of adverse habitats. Overpopulation causes overutilization of food supplies, which results in malnutrition and a decrease in resistance to diseases. Examples of such ecological relationships in populations of Canada geese, California quail, red grouse, deer, rabbits, voles, mice and lemmings are presented.

The giant African snail Achatina fulica as natural intermediate host of Angiostrongylus cantonensis in Pernambuco, northeast Brazil.

PubMed

Thiengo, S C; Maldonado, A; Mota, E M; Torres, E J L; Caldeira, R; Carvalho, O S; Oliveira, A P M; Simões, R O; Fernandez, M A; Lanfredi, R M

2010-09-01

The human cases of eosinophilic meningitis recently reported from Brazil have focused the attention of the public health agencies on the role the introduced snail Achatina fulica plays as hosts of the metastrongylid nematodes. Determining the potential of this snail to host and develop infective larval stages of metastrongylids in the wild and identify the species harbored by them is crucial for designing effective control measures. Here we assess if A. fulica may act as intermediate host of A. cantonensis at the peridomiciliary areas of a patient's house from state of Pernambuco (PE), who was diagnosed with eosinophilic meningitis and a history of ingesting raw molluscs. Larvae obtained from naturally infected A. fulica were orally administered to Rattus norvegicus. The worms were collected from the pulmonary artery and brain, and were morphologically characterized and compared to the Japan isolate of A. cantonensis. Adult worms and infective L(3) larvae (PE isolate) recovered from A. fulica specimens were also analyzed by polymerase chain reaction and restriction fragment length polymorphism of ITS2 region from rDNA and compared to A. cantonensis (ES isolate), A. vasorum (MG isolate) and A. costaricensis (RS isolate). The large size of the spicules (greater than those observed in other species of Angiostrongylus) and the pattern of the bursal rays agree with the original species description by Chen (1935). Furthermore, the morphology of the PE isolate was similar to that of Japan isolate. The PCR-RFLP profiles obtained were distinctive among species and no variation in patterns was detected among adult individuals from A. cantonensis isolates from PE and ES. The importance of A. fulica as an intermediate host of eosinophilic menigoencepahlitis in Brazil is emphasized. 2010 Elsevier B.V. All rights reserved.

Effects of Smallmouth Buffalo and Potassium Permanganate Treatment on Plankton ans Pond Water Quality

USDA-ARS?s Scientific Manuscript database

Removal of intermediate hosts is one option for control of disease in channel catfish production systems. We evaluated use of predaceous fish (smallmouth buffalo) and chemical treatment (potassium permanganate) to remove snails that serve as hosts protecting Dero worms. Both methods of treatment r...

Life history and biology of Fascioloides magna (Trematoda) and its native and exotic hosts

PubMed Central

Malcicka, Miriama

2015-01-01

Host–parasite interactions are model systems in a wide range of ecological and evolutionary fields and may be utilized for testing numerous theories and hypotheses in terms of both applied and fundamental research. For instance, they are important in terms of studying coevolutionary arms races, species invasions, and in economic terms the health of livestock and humans. Here, I present a comprehensive description of the life history, biogeography, and biology of the giant liver fluke, Fascioloides magna, and both its intermediate and definitive hosts. F. magna is native to North America where it uses several species of freshwater snails (Lymnaeidae) as intermediate hosts and four main species of ungulates as definitive hosts. The fluke has also been introduced into parts of Europe where it is now established in two lymnaeid snail species and three ungulate species. This study gives a comprehensive description of different developmental stages of the fluke in its two host classes, as well as detailed notes on historical and present distributions of F. magna in North America and Europe as well as in its snail and deer hosts (with range maps provided). Aberrant and dead-end hosts are also discussed in detail, and descriptive phylogenies are provided for all of the organisms. I briefly discuss how F. magna represents a model example of multiple-level ecological fitting, a phenomenon not yet described in the empirical literature. Lastly, I explore possible future scenarios for fluke invasion in Europe, where it is currently expanding its range. PMID:25897378

Larval excretory-secretory products from the parasite Schistosoma mansoni modulate HSP70 protein expression in defence cells of its snail host, Biomphalaria glabrata

PubMed Central

Zahoor, Zahida; Davies, Angela J.; Kirk, Ruth S.; Rollinson, David

2010-01-01

Synthesis of heat shock proteins (HSPs) following cellular stress is a response shared by many organisms. Amongst the HSP family, the ∼70 kDa HSPs are the most evolutionarily conserved with intracellular chaperone and extracellular immunoregulatory functions. This study focused on the effects of larval excretory-secretory products (ESPs) from the parasite Schistosoma mansoni on HSP70 protein expression levels in haemocytes (defence cells) from its snail intermediate host Biomphalaria glabrata. S. mansoni larval stage ESPs are known to interfere with haemocyte physiology and behaviour. Haemocytes from two different B. glabrata strains, one which is susceptible to S. mansoni infection and one which is resistant, both showed reduced HSP70 protein levels following 1 h challenge with S. mansoni ESPs when compared to unchallenged controls; however, the reduction observed in the resistant strain was less marked. The decline in intracellular HSP70 protein persisted for at least 5 h in resistant snail haemocytes only. Furthermore, in schistosome-susceptible snails infected by S. mansoni for 35 days, haemocytes possessed approximately 70% less HSP70. The proteasome inhibitor, MG132, partially restored HSP70 protein levels in ESP-challenged haemocytes, demonstrating that the decrease in HSP70 was in part due to intracellular degradation. The extracellular signal-regulated kinase (ERK) signalling pathway appears to regulate HSP70 protein expression in these cells, as the mitogen-activated protein-ERK kinase 1/2 (MEK1/2) inhibitor, U0126, significantly reduced HSP70 protein levels. Disruption of intracellular HSP70 protein expression in B. glabrata haemocytes by S. mansoni ESPs may be a strategy employed by the parasite to manipulate the immune response of the intermediate snail host. PMID:20182834

Larval excretory-secretory products from the parasite Schistosoma mansoni modulate HSP70 protein expression in defence cells of its snail host, Biomphalaria glabrata.

PubMed

Zahoor, Zahida; Davies, Angela J; Kirk, Ruth S; Rollinson, David; Walker, Anthony John

2010-09-01

Synthesis of heat shock proteins (HSPs) following cellular stress is a response shared by many organisms. Amongst the HSP family, the approximately 70 kDa HSPs are the most evolutionarily conserved with intracellular chaperone and extracellular immunoregulatory functions. This study focused on the effects of larval excretory-secretory products (ESPs) from the parasite Schistosoma mansoni on HSP70 protein expression levels in haemocytes (defence cells) from its snail intermediate host Biomphalaria glabrata. S. mansoni larval stage ESPs are known to interfere with haemocyte physiology and behaviour. Haemocytes from two different B. glabrata strains, one which is susceptible to S. mansoni infection and one which is resistant, both showed reduced HSP70 protein levels following 1 h challenge with S. mansoni ESPs when compared to unchallenged controls; however, the reduction observed in the resistant strain was less marked. The decline in intracellular HSP70 protein persisted for at least 5 h in resistant snail haemocytes only. Furthermore, in schistosome-susceptible snails infected by S. mansoni for 35 days, haemocytes possessed approximately 70% less HSP70. The proteasome inhibitor, MG132, partially restored HSP70 protein levels in ESP-challenged haemocytes, demonstrating that the decrease in HSP70 was in part due to intracellular degradation. The extracellular signal-regulated kinase (ERK) signalling pathway appears to regulate HSP70 protein expression in these cells, as the mitogen-activated protein-ERK kinase 1/2 (MEK1/2) inhibitor, U0126, significantly reduced HSP70 protein levels. Disruption of intracellular HSP70 protein expression in B. glabrata haemocytes by S. mansoni ESPs may be a strategy employed by the parasite to manipulate the immune response of the intermediate snail host.

Measurement of Selected Enzymatic Activities in Solanum nigrum-Treated Biomphalaria arabica Snails

NASA Astrophysics Data System (ADS)

Al-Daihan, Sooad

In the present study, glucose, acid and alkaline phosphatases (ACP and ALP), α-amylase and lipase were measured for the first time in tissue homogenates of Biomphalaria arabica snails, molluscan intermediate host for Schistosoma mansoni in Saudi Arabia. Also, the effect of sublethal concentrations (LC25) of dry powdered Solanum nigrum leaf was tested as plant molluscicide against this snail species. The tested enzymes were altered in molluscicide-treated snails compared to control. While ALP and amylase were slightly affected, ACP and lipase were significantly altered. Glucose as an important energy source for a successful schistosome-snail relationship was significantly reduced in molluscicide-treated snails. In conclusion, sublethal concentration of the molluscicide showed potent effect in disturbing snail biochemistry which may render them physiologically unsuitable for the developing of schistosome parasite. This could be considered as a promising strategy to control the disease.

Prevalence of Fasciola in cattle and of its intermediate host Lymnaea snails in central Vietnam.

PubMed

Nguyen, Sam Thi; Nguyen, Duc Tan; Van Nguyen, Thoai; Huynh, Vu Vy; Le, Duc Quyet; Fukuda, Yasuhiro; Nakai, Yutaka

2012-12-01

The aims of this study were to investigate the prevalence of natural Fasciola infections in both the definitive hosts (cattle) and the intermediate hosts (Lymnaea snails) in central Vietnam. A total of 1,075 fecal samples, randomly collected from cattle in Binh Dinh, Khanh Hoa, and Phu Yen provinces, were examined for Fasciola eggs by a sedimentation method. The overall prevalence of Fasciola was 45.3 %. A subset of the animals (235) was also screened for antibodies against Fasciola by an enzyme-linked immunosorbent assay. Overall, 46.3 % of these animals were shedding Fasciola eggs while 87.2 % were Fasciola seropositive. A lower prevalence of Fasciola was observed in calves ≤ 2 years of age (37.6 %) compared to that in cattle >2 years of age (53.7 %) (p < 0.05). The prevalence in the rainy season (50.8 %) was significantly different to that in the dry season (38.1 %) (p < 0.05). Of the 3.269 Lymnaea viridis and 1.128 Lymnaea swinhoei examined, 31 (0.95 %) and seven (0.62 %), respectively, were found to be infected with Fasciola. This appears to be the first epidemiological survey of the prevalence of Fasciola in cattle and snails in these three provinces in central Vietnam.

Types of trematodes infecting freshwater snails found in irrigation canals in the East Nile locality, Khartoum, Sudan.

PubMed

Mohammed, Nidal A I; Madsen, Henry; Ahmed, Abdel Aziz A R M

2016-02-25

The planorbid freshwater snails of the two genera, Biomphalaria and Bulinus -have been vigorously studied due to the role they play as intermediate hosts of schistosomiasis. In Sudan specifically, most studies have focused on the chemical and ecological control of the two genera, but few studies have looked at their biological control. This study explored the coexistence of other species of freshwater snails and the two genera along with their trematode infections in relation to a number of environmental factors in the East Nile locality, Khartoum state, Sudan. Freshwater snails from irrigation canals (abueshreens) were sampled monthly from January 2004 to December 2005. The snails were examined for trematode infections by cercarial emergence immediately after collection and then weekly for an additional four weeks to allow for the maturation of prepatent infections. Vegetation cover in the study sites as well as the physicochemical characteristics of the water, including temperature, were also recorded. A total of 10,493 snails, representing seven species, were collected. The most abundant species was Biomphalaria pfeifferi, representing 48.6 % of the sample. Overall, 14.1 % of the snails were found to be shedding some type of cercariae. Five species were found to have infections; among these the Bulinus truncatus species was found to be the most heavily infected, with an overall prevalence of 46.2 %. Double infections were recorded in only two B. truncatus snails and one Cleopatra bulimoides snail. Twenty different morphotypes of cercariae were recorded, seven of which appeared not to conform to previously described cercariae from Africa. Xiphidiocercariae type 1 was the most common type of cercariae recovered, accounting for 44.3 % of all infections. The density of snails tended to be lower during the summer months than the winter months, except for M. tuberculata snails, which were not affected by seasonal changes. The findings of this study indicate that besides schistosomes, other larval trematodes are found, and some use the same intermediate hosts as the schistosomes. Further studies should be conducted to determine whether some of these trematodes could be manipulated for the biological control of schistosomiasis.

Taken to the limit--Is desiccation stress causing precocious encystment of trematode parasites in snails?

PubMed

O'Dwyer, Katie; Poulin, Robert

2015-12-01

When hosts experience environmental stress, the quantity and quality of resources they provide for parasites may be diminished, and host longevity may be decreased. Under stress, parasites may adopt alternative strategies to avoid fitness reductions. Trematode parasites typically have complex life cycles, involving asexual reproduction in a gastropod first intermediate host. A rare phenomenon, briefly mentioned in the literature, and termed 'precocious encystment' involves the next stage in the parasites' life cycle (metacercarial cyst) forming within the preceding stage (redia), while still inside the snail. In the trematode Parorchis sp. NZ using rocky shore snails exposed to long periods outside water, we hypothesised that this might be an adaptive strategy against desiccation, preventing parasite emergence from the snail. To test this, we first investigated the effect of prolonged desiccation on the survival of two species of high intertidal snails. Secondly, we measured the reproductive output (cercarial production) of the parasite under wet and dry conditions. Finally, we quantified the influence of desiccation stress on the occurrence of precocious encystment. Snail mortality was higher under dry conditions, indicating stress, and it was somewhat exacerbated for infected snails. Parasite reproductive output differed between wet and dry conditions, with parasites of snails kept in dry conditions producing more cercariae when placed in water. Little variation was observed in the occurrence of precocious encystment, although some subtle patterns emerged. Given the stresses associated with living in high intertidal environments, we discuss precocious encystment as a possible stress response in this trematode parasite. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Seasonal and Spatial Environmental Influence on Opisthorchis viverrini Intermediate Hosts, Abundance, and Distribution: Insights on Transmission Dynamics and Sustainable Control

PubMed Central

Kim, Christina Sunyoung; Echaubard, Pierre; Suwannatrai, Apiporn; Kaewkes, Sasithorn; Wilcox, Bruce A.; Sripa, Banchob

2016-01-01

Background Opisthorchis viverrini (Ov) is a complex-life-cycle trematode affecting 10 million people in SEA (Southeast Asia). Human infection occurs when infected cyprinid fish are consumed raw or undercooked. Ov requires three hosts and presents two free-living parasitic stages. As a consequence Ov transmission and infection in intermediate and human hosts are strongly mediated by environmental factors and understanding how environmental variability influences intermediate host abundance is critical. The objectives of this study were 1) to document water parameters, intermediate hosts abundance and infection spatio-temporal variation, 2) to assess their causal relationships and identify windows of transmission risk. Methodology/Principal Findings Fish and snails were collected monthly for one year at 12 sites in Lawa Lake, an Ov-endemic region of Khon Kaen Province in Northeast Thailand. Physicochemical water parameters [pH, temperature (Tp), dissolved oxygen (DO), Salinity, electrical conductivity (EC), total dissolved solid (TDS), nitrite nitrogen (NO2-N), lead (Pb), total coliform bacteria (TCB) and fecal coliform bacteria (FCB)] were measured. Multivariate analyses, linear models and kriging were used to characterize water parameter variation and its influence on host abundance and infection prevalence. We found that sampling sites could be grouped in three clusters and discriminated along a nitrogen-salinity gradient where higher levels in the lake’s southern region predicted higher Bithynia relative abundance (P<0.05) and lower snail and fish species diversity (P<0.05). Highest Bithynia abundance occurred during rainy season (P<0.001), independently of site influence. Cyprinids were the most abundant fish family and higher cyprinid relative abundance was found in areas with higher Bithynia relative abundance (P<0.05). Ov infection in snails was anecdotal while Ov infection in fish was higher in the southern region (P<0.001) at sites showing high FCB. Conclusions/Significance Our results indicate that water contamination and waterways configuration can influence freshwater communities’ assemblages possibly creating ideal conditions for sustained transmission. Sustainable control may require a better appreciation of the system’s ecology with wise governance and development planning particularly in the current context of SEA agricultural intensification and landscape modification. PMID:27880787

Seasonal and Spatial Environmental Influence on Opisthorchis viverrini Intermediate Hosts, Abundance, and Distribution: Insights on Transmission Dynamics and Sustainable Control.

PubMed

Kim, Christina Sunyoung; Echaubard, Pierre; Suwannatrai, Apiporn; Kaewkes, Sasithorn; Wilcox, Bruce A; Sripa, Banchob

2016-11-01

Opisthorchis viverrini (Ov) is a complex-life-cycle trematode affecting 10 million people in SEA (Southeast Asia). Human infection occurs when infected cyprinid fish are consumed raw or undercooked. Ov requires three hosts and presents two free-living parasitic stages. As a consequence Ov transmission and infection in intermediate and human hosts are strongly mediated by environmental factors and understanding how environmental variability influences intermediate host abundance is critical. The objectives of this study were 1) to document water parameters, intermediate hosts abundance and infection spatio-temporal variation, 2) to assess their causal relationships and identify windows of transmission risk. Fish and snails were collected monthly for one year at 12 sites in Lawa Lake, an Ov-endemic region of Khon Kaen Province in Northeast Thailand. Physicochemical water parameters [pH, temperature (Tp), dissolved oxygen (DO), Salinity, electrical conductivity (EC), total dissolved solid (TDS), nitrite nitrogen (NO2-N), lead (Pb), total coliform bacteria (TCB) and fecal coliform bacteria (FCB)] were measured. Multivariate analyses, linear models and kriging were used to characterize water parameter variation and its influence on host abundance and infection prevalence. We found that sampling sites could be grouped in three clusters and discriminated along a nitrogen-salinity gradient where higher levels in the lake's southern region predicted higher Bithynia relative abundance (P<0.05) and lower snail and fish species diversity (P<0.05). Highest Bithynia abundance occurred during rainy season (P<0.001), independently of site influence. Cyprinids were the most abundant fish family and higher cyprinid relative abundance was found in areas with higher Bithynia relative abundance (P<0.05). Ov infection in snails was anecdotal while Ov infection in fish was higher in the southern region (P<0.001) at sites showing high FCB. Our results indicate that water contamination and waterways configuration can influence freshwater communities' assemblages possibly creating ideal conditions for sustained transmission. Sustainable control may require a better appreciation of the system's ecology with wise governance and development planning particularly in the current context of SEA agricultural intensification and landscape modification.

Seasonal variation in abiotic factors and ferulic acid toxicity in snail-attractant pellets against the intermediate host snail Lymnaea acuminata.

PubMed

Agrahari, P; Singh, D K

2013-11-01

Laboratory evaluation was made to access the seasonal variations in abiotic environmental factors temperature, pH, dissolved oxygen, carbon dioxide, electrical conductivity and ferulic acid toxicity in snail-attractant pellets (SAP) against the intermediate host snail Lymnaea acuminata in each month of the years 2010 and 2011. On the basis of a 24-h toxicity assay, it was noted that lethal concentration values of 4.03, 3.73% and 4.45% in SAP containing starch and 4.16, 4.23% and 4.29% in SAP containing proline during the months of May, June and September, respectively, were most effective in killing the snails, while SAP containing starch/proline + ferulic acid was least effective in the month of January/February (24-h lethal concentration value was 7.67%/7.63% in SAP). There was a significant positive correlation between lethal concentration value of ferulic acid containing SAP and levels of dissolved O2 /pH of water in corresponding months. On the contrary, a negative correlation was observed between lethal concentration value and dissolved CO2 /temperature of test water in the same months. To ascertain that such a relationship between toxicity and abiotic factors is not co-incidental, the nervous tissue of treated (40% and 80% of 24-h lethal concentration value) and control group of snails was assayed for the activity of acetylcholinesterase (AChE) in each of the 12 months of the same year. There was a maximum inhibition of 58.43% of AChE, in snails exposed to 80% of the 24-h lethal concentration value of ferulic acid + starch in the month of May. This work shows conclusively that the best time to control snail population with SAP containing ferulic acid is during the months of May, June and September. © 2012 Blackwell Verlag GmbH.

Refined stratified-worm-burden models that incorporate specific biological features of human and snail hosts provide better estimates of Schistosoma diagnosis, transmission, and control.

PubMed

Gurarie, David; King, Charles H; Yoon, Nara; Li, Emily

2016-08-04

Schistosoma parasites sustain a complex transmission process that cycles between a definitive human host, two free-swimming larval stages, and an intermediate snail host. Multiple factors modify their transmission and affect their control, including heterogeneity in host populations and environment, the aggregated distribution of human worm burdens, and features of parasite reproduction and host snail biology. Because these factors serve to enhance local transmission, their inclusion is important in attempting accurate quantitative prediction of the outcomes of schistosomiasis control programs. However, their inclusion raises many mathematical and computational challenges. To address these, we have recently developed a tractable stratified worm burden (SWB) model that occupies an intermediate place between simpler deterministic mean worm burden models and the very computationally-intensive, autonomous agent models. To refine the accuracy of model predictions, we modified an earlier version of the SWB by incorporating factors representing essential in-host biology (parasite mating, aggregation, density-dependent fecundity, and random egg-release) into demographically structured host communities. We also revised the snail component of the transmission model to reflect a saturable form of human-to-snail transmission. The new model allowed us to realistically simulate overdispersed egg-test results observed in individual-level field data. We further developed a Bayesian-type calibration methodology that accounted for model and data uncertainties. The new model methodology was applied to multi-year, individual-level field data on S. haematobium infections in coastal Kenya. We successfully derived age-specific estimates of worm burden distributions and worm fecundity and crowding functions for children and adults. Estimates from the new SWB model were compared with those from the older, simpler SWB with some substantial differences noted. We validated our new SWB estimates in prediction of drug treatment-based control outcomes for a typical Kenyan community. The new version of the SWB model provides a better tool to predict the outcomes of ongoing schistosomiasis control programs. It reflects parasite features that augment and perpetuate transmission, while it also readily incorporates differences in diagnostic testing and human sub-population differences in treatment coverage. Once extended to other Schistosoma species and transmission environments, it will provide a useful and efficient tool for planning control and elimination strategies.

Phylogenetic relationships of some species of the family Echinostomatidae Odner, 1910 (Trematoda), inferred from nuclear rDNA sequences and karyological analysis

PubMed Central

Stanevičiūtė, Gražina; Stunžėnas, Virmantas; Petkevičiūtė, Romualda

2015-01-01

Abstract The family Echinostomatidae Looss, 1899 exhibits a substantial taxonomic diversity, morphological criteria adopted by different authors have resulted in its subdivision into an impressive number of subfamilies. The status of the subfamily Echinochasminae Odhner, 1910 was changed in various classifications. Genetic characteristics and phylogenetic analysis of four Echinostomatidae species – Echinochasmus sp., Echinochasmus coaxatus Dietz, 1909, Stephanoprora pseudoechinata (Olsson, 1876) and Echinoparyphium mordwilkoi Skrjabin, 1915 were obtained to understand well enough the homogeneity of the Echinochasminae and phylogenetic relationships within the Echinostomatidae. Chromosome set and nuclear rDNA (ITS2 and 28S) sequences of parthenites of Echinochasmus sp. were studied. The karyotype of this species (2n=20, one pair of large bi-armed chromosomes and others are smaller-sized, mainly one-armed, chromosomes) differed from that previously described for two other representatives of the Echinochasminae, Echinochasmus beleocephalus (von Linstow, 1893), 2n=14, and Episthmium bursicola (Creplin, 1937), 2n=18. In phylogenetic trees based on ITS2 and 28S datasets, a well-supported subclade with Echinochasmus sp. and Stephanoprora pseudoechinata clustered with one well-supported clade together with Echinochasmus japonicus Tanabe, 1926 (data only for 28S) and Echinochasmus coaxatus. These results supported close phylogenetic relationships between Echinochasmus Dietz, 1909 and Stephanoprora Odhner, 1902. Phylogenetic analysis revealed a clear separation of related species of Echinostomatoidea restricted to prosobranch snails as first intermediate hosts, from other species of Echinostomatidae and Psilostomidae, developing in Lymnaeoidea snails as first intermediate hosts. According to the data based on rDNA phylogeny, it was supposed that evolution of parasitic flukes linked with first intermediate hosts. Digeneans parasitizing prosobranch snails showed higher dynamic of karyotype evolution provided by different chromosomal rearrangements including Robertsonian translocations and pericentric inversions than more stable karyotype of digenean worms parasitizing lymnaeoid pulmonate snails. PMID:26140167

Description and proposed life cycle of Maritrema novaezealandensis n. sp. (Microphallidae) parasitic in red-billed gulls, Larus novaehollandiae scopulinus, from Otago Harbor, South Island, New Zealand.

PubMed

Martorelli, Sergio R; Fredensborg, Brian L; Mouritsen, Kim N; Poulin, Robert

2004-04-01

Maritrema novaezealandensis n. sp. is described from Otago Harbor, South Island, New Zealand, on the basis of adult specimens collected from the Red-billed gull, Larus novaehollandiae scopulinus, and excysted metacercariae obtained from crabs. It belongs to the "eroliae group" and differs from other related species mainly in the shape, size, and patterns of distributions of the spines on the cirrus, the shape of the metraterm, the presence of an unlobed ovary, and the complete ring of the vitelline follicles. Based on morphometric features of metacercariae and adult specimens, the trophic relationships among invertebrate and vertebrate hosts, experimental infections, and previous reports of species of Maritrema with similar transmission patterns, the life cycle of M. novaezealandensis n. sp. is described. A 3-host life cycle is proposed for this parasite. The first intermediate host is the mud snail, Zeacumantus subcarinatus, in which the cercarial stage is produced in sporocysts located within the gonad of the snail. At least 3 crab species (Hemigrapsus crenulatus, Macrophtalmus hirtipes, and Halicarcinus whitei) and several species of amphipods act as second intermediate hosts, with metacercariae encysted in the body cavity of the crustacean host. Finally, the definitive host, the gull, L. n. scopulinus, harbors the adult worms in its intestine.

Research on Dynamic Monitoring (1990-2010)of Schistosomiasis Vector- Snail at Xinmin Beach, Gaoyou Lake, Jiangsu Province, China

NASA Astrophysics Data System (ADS)

Liu, Zhaoyan; Li, Chuanrong; Tang, Lingli; Zhou, Xiaonong; Ma, Lingling

2014-11-01

Schistosomiasis is a parasitic disease that menaces human health. In terms of impact, this disease is second only to malaria as the most devastating parasitic disease. Oncomelania hupensis (snail) is the unique intermediate host of schistosoma, so monitoring and controlling of the number of snail is key to reduce the risk of schistosomiasis transmission. Remote sensing technology can real-timely access the large-scale environmental factors related to snail breeding and reproduction, and can also provide the efficient information to determine the location, area, and spread tendency of snail. Based on the T-S (Takagi-Sugeno) fuzzy information theory, a quantitative remote sensing monitoring model of snail has been developed in previous wok. In a case study, this paper will take Xinmin beach, Gaoyou Lake as new research area, carry out 20 years (1990 - 2010) dynamic monitoring, to further validate the effectiveness of the T-S Fuzzy RS snail monitoring model.

Research on Dynamic Monitoring (1990-2010) of Schistosomiasis Vector-Snail at Xinmin Beach, Gaoyou Lake, Jiangsu Province, China

NASA Astrophysics Data System (ADS)

Liu, Zhaoyan; Li, Chuanrong; Tang, Lingli; Zhou, Xiaonong; Ma, Lingling

2014-11-01

Schistosomiasis is a parasitic disease that menaces human health. In terms of impact, this disease is second only to malaria as the most devastating parasitic disease. Oncomelania hupensis (snail) is the unique intermediate host of schistosoma, so monitoring and controlling of the number of snail is key to reduce the risk of schistosomiasis transmission. Remote sensing technology can real-timely access the large-scale environmental factors related to snail breeding and reproduction, and can also provide the efficient information to determine the location, area, and spread tendency of snail. Based on the T-S (Takagi-Sugeno) fuzzy information theory, a quantitative remote sensing monitoring model of snail has been developed in previous wok. In a case study, this paper will take Xinmin beach, Gaoyou Lake as new research area, carry out 20 years (1990 - 2010) dynamic monitoring, to further validate the effectiveness of the T-S Fuzzy RS snail monitoring model.

Detection of early and single infections of Schistosoma japonicum in the intermediate host snail, Oncomelania hupensis, by PCR and loop-mediated isothermal amplification (LAMP) assay.

PubMed

Kumagai, Takashi; Furushima-Shimogawara, Rieko; Ohmae, Hiroshi; Wang, Tian-Ping; Lu, Shaohong; Chen, Rui; Wen, Liyong; Ohta, Nobuo

2010-09-01

Polymerase chain reaction (PCR) with the specific primer set amplifying 28S ribosomal DNA (rDNA) of Schistosoma japonicum was able to detect genomic DNA of S. japonicum, but not S. mansoni, at 100 fg. This procedure enabled us to detect the DNA from a single miracidium and a snail infected with one miracidium at just 1 day after infection. We compared these results with those from loop-mediated isothermal amplification (LAMP) targeting 28S rDNA and found similar results. The LAMP could amplify the specific DNA from a group of 100 normal snails mixed with one infected snail A PCR screening of infected snails from endemic regions in Anhui Province revealed schistosomal DNA even in snails found negative by microscopy. PCR and LAMP show promise for monitoring the early infection rate in snails, and they may be useful for predicting the risk of infection in the endemic places.

MALACOLOGICAL INVESTIGATION OF THE FULLY OPERATIONAL NAM THEUN 2 HYDROELECTRIC DAM PROJECT IN KHAMMOUANE PROVINCE, CENTRAL LAO PDR.

PubMed

Sri-aroon, Pusadee; Chusongsang, Phiraphol; Chusongsang, Yupa; Limpanont, Yanin; Surinthwong, Pornpimol; Vongphayloth, Khamsing; Brey, Paul T

2015-09-01

We conducted a malacological investigation in four districts of the Nam Theun 2 (NT2) hydroelectric dam project area, Khammouane Province, central Lao PDR (Nakai, Gnommalath, Mahaxai and Xe Bang Fai), after the first and second years of full operation in March 2010 and November 2011 to determine health risks for humans. A total 10,863 snail specimens (10 families/23 species) from 57 sampling stations and 12,902 snail specimens (eight families/21 species) from 66 sampling stations were collected in 2010 and 2011, respectively. Neotricula aperta (gamma race), the intermediate host for Schistosoma mekongi, was found in large numbers (5,853 specimens) in 2010 in Nam Gnom (downstream) at Station 25 (Mueang Gnommalath: Gnommalath District) and in fewer numbers (170 specimens) at Station 26 (Ban Thathod: Gnommalath District). In 2011, significantly fewer numbers (434 specimens) of N. aperta were found at Station 25. No snails were found to be infected with S. mekongi; however, 3.6% and 0.45% of Bithynia (D.). s. goniomphalos specimens collected were found to be infected with Opisthorchis viverrini (human liver fluke) during 2010 and 2011, respectively. Pomacea canaliculata, the rice crop pest, the intermediate host of Angiostrongylus (Parastrongylus) cantonensis, was found in the greatest numbers during 2010 and 2011; the prevalence increased significantly from 1.3% in 2010 to 53.3% in 2011. We also found seasonal variation in snail populations in terms of abundance and diversity. The snail fauna and risk for transmission of parasitic diseases need to be monitored continuously to evaluate the long-term impact of the dam project.

Endemic angiostrongyliasis in the Brazilian Amazon: natural parasitism of Angiostrongylus cantonensis in Rattus rattus and R. norvegicus, and sympatric giant African land snails, Achatina fulica.

PubMed

Moreira, V L C; Giese, E G; Melo, F T V; Simões, R O; Thiengo, S C; Maldonado, A; Santos, J N

2013-01-01

Angiostrongylus cantonensis, the rat lungworm, is one etiological agent of eosinophilic meningoencephalitis in humans. This zoonosis is frequently found in Asia and, more recently, in North America, Caribbean Island and northeastern of South America. Until now, research of A. cantonensis in southern, southeastern and northeastern regions of Brazil has been found natural infections only terrestrial and freshwater intermediate snail hosts (Achatina fulica, Sarasinula marginata, Subulina octona, Bradybaena similaris and Pomacea lineate). In this study, we examined the occurrence of helminthes in the synantropic rodents Rattus rattus and Rattus norvegicus in northern Brazil, focusing on the role of these species as vertebrate hosts of A. cantonensis and A. fulica as intermediate host have found natural. Thirty specimens of R. rattus and twelve of R. norvegicus were collected in the Guamá and Jurunas neighborhoods of the city of Belém, in the Brazilian state of Pará, of which almost 10% harbored adult worms in their pulmonary arteries. Sympatric A. fulica were found to be infected by L(3) larvae, which experimental infection confirmed to be A. cantonensis. Natural infection of snails and rodents with A. cantonensis was confirmed through morphological and morphometrical analyses of adults and larvae using light microscopy, scanning electron microscopy and molecular sequences of partial Cytochrome Oxidase subunit I. Phylogenetic analyses showed that A. cantonensis isolated from Pará, Brazil is similar to Japan isolate; once these specimens produced a single haplotype with high bootstrap support with Rio de Janeiro isolate. This study confirms that A. cantonensis is now endemic in northern Brazil, and that R. rattus and R. norvegicus act as natural definitive hosts, and A. fulica as the intermediate host of the parasite in this region. Copyright © 2012 Elsevier B.V. All rights reserved.

Fascioliasis of livestock and snail host for Fasciola in the Altiplano Region of Bolivia.

PubMed

Ueno, H; Arandia, R; Morales, G; Medina, G

1975-01-01

Fascioliasis caused by Fasciola hepatica was a serious problem for sheep and alpacas in the Altiplano Region of Bolivia. In some provinces close to Lake Titicaca, the raising of sheep was forced to discontinue, because infection with the fluke made it unprofitable and almost impossible. It was proved that in the Altiplano Region, two species of freshwater snails, Lymnaea viatrix and L. cubensis var., served as intermediate hosts for F. hepatica. In some subtropical areas of Bolivia, these snails could not be found, although other Lymnaea sp. was widely distributed there. As it is possible for Lymnaea sp. to be intermediate host for the fluke, further studies are required on the identification. Acute fascioliasis of sheep occurred in the Altiplano Region principally during a period from May to July, or the dry season. In some areas, the mortality rate of infected sheep was roughly estimated as 15 to 25% annually. Contamination with Fasciola metacercariae of herbage and semi-aquatic plants grown in a swamp in one of these areas was biologically assessed, using guinea pigs. Plants of Compositae and Eleocharis sp. were contaminated most intensely and those of Senicio sp. and Vallisneria sp. carried a fairly large number of cysts, while plants of Scirpus sp. and Ranunclaceae carried only a few cysts. No signs of Fasciola infection were observed in any animal given the plants of Liliaceae.

Survival of the faucet snail after chemical disinfection, pH extremes, and heated water bath treatments

USGS Publications Warehouse

Mitchell, A.J.; Cole, Rebecca A.

2008-01-01

The faucet snail Bithynia tentaculata, a nonindigenous aquatic snail from Eurasia, was introduced into Lake Michigan in 1871 and has spread to the mid-Atlantic states, the Great Lakes region, Montana, and most recently, the Mississippi River. The faucet snail serves as intermediate host for several trematodes that have caused large-scale mortality among water birds, primarily in the Great Lakes region and Montana. It is important to limit the spread of the faucet snail; small fisheries equipment can serve as a method of snail distribution. Treatments with chemical disinfection, pH extremes, and heated water baths were tested to determine their effectiveness as a disinfectant for small fisheries equipment. Two treatments eliminated all test snails: (1) a 24-h exposure to Hydrothol 191 at a concentration of at least 20 mg/L and (2) a treatment with 50°C heated water for 1 min or longer. Faucet snails were highly resistant to ethanol, NaCl, formalin, Lysol, potassium permanganate, copper sulfate, Baquacil, Virkon, household bleach, and pH extremes (as low as 1 and as high as 13).

SPATIAL DISTRIBUTION OF LYMNAEIDAE (MOLLUSCA, BASOMMATOPHORA), INTERMEDIATE HOST OF Fasciola hepatica LINNAEUS, 1758 (TREMATODA, DIGENEA) IN BRAZIL

PubMed Central

Medeiros, Camilla; Scholte, Ronaldo Guilherme Carvalho; D'ávila, Sthefane; Caldeira, Roberta Lima; Carvalho, Omar dos Santos

2014-01-01

Snails of the family Lymnaeidae act as intermediate hosts in the biological cycle of Fasciola hepatica, which is a biological agent of fasciolosis, a parasitic disease of medical importance for humans and animals. The present work aimed to update and map the spatial distribution of the intermediate host snails of F. hepatica in Brazil. Data on the distribution of lymnaeids species were compiled from the Collection of Medical Malacology (Fiocruz-CMM, CPqRR), Collection of Malacology (MZUSP), “SpeciesLink” (CRIA) network and through systematic surveys in the literature. Our maps of the distribution of lymnaeids show that Pseudosuccinea columella is the most common species and it is widespread in the South and Southeast with few records in the Midwest, North and Northeast regions. The distribution of the Galba viatrix, G. cubensis and G. truncatula showed a few records in the South and Southeast regions, they were not reported for the Midwest, North and Northeast. In addition, in the South region there are a few records for G. viatrix and one occurrence of Lymnaea rupestris. Our findings resulted in the first map of the spatial distribution of Lymnaeidae species in Brazil which might be useful to better understand the fasciolosis distribution and delineate priority areas for control interventions. PMID:24879003

Cross-Sectional Serological Survey of Human Fascioliasis in Canutama Municipality in Western Amazon, Brazil

PubMed Central

Lima, Walter dos Santos; de Almeida, Francisco Lazaro Moreira; Coelho, Leila Inês Aguiar Raposo Câmara; Araújo, Guilherme Alfredo Novelino; Lima, Mariana Gomes; Maciel, Luiz Henrique Gonçalves; Pereira, Cíntia Aparecida de Jesus; Maciel, Thaís Costa da Silva; Guerra, Jorge Augusto de Oliveira; Santana, Rosa Amélia Gonçalves; Guerra, Maria das Graças Vale Barbosa

2018-01-01

Background Fascioliasis is an important parasitic disease. In the northern region of Brazil, a human parasite infection has been reported through a coprological survey. Eggs of Fasciola hepatica were found in fecal samples of 11 individuals. Knowledge of the infection in animals or the presence of snails is necessary to address the possibility of the parasite cycle occurrence in that region. The aim of this study was to describe the transmission of human fascioliasis in Canutama, Amazonas, in Western Amazonia, Brazil. Methods Serological (ELISA and Western Blot, WB) and parasitological analyses were carried out in humans. In addition, the presence of the intermediate snail host within the community was examined. Results A total of 434 human samples were included in the study, of which 36 (8.3%) were reactive by ELISA and 8 (1.8%) were reactive by WB. Fasciola hepatica eggs were found in one human sample. The occurrence of the intermediated host was recorded and 31/43 specimens were identified as Lymnaea columella. Conclusion. Canutama constitutes a focus of transmission of human fascioliasis. This study describes the first serological survey for human fascioliasis, as well as its simultaneous occurrence in human hosts and possible intermediates performed in northern Brazil. PMID:29593895

Laboratory breeding and testing of Australorbis glabratus for molluscicidal screening

PubMed Central

Hopf, H. S.; Muller, R. L.

1962-01-01

The authors describe a technique for laboratory breeding of Australorbis glabratus, the intermediate host of Schistosoma mansoni in South America. This technique is suitable for obtaining large numbers of snails in a small space with the minimum of maintenance time and under carefully controlled conditions. Techniques are also outlined for testing molluscicides against eggs and young snails as well as against adults. It is considered that, in view of the saving in breeding time and space effected, testing against young snails has several advantages for primary screening. With no compounds tested have anomalous results been obtained. Finally, the authors report on the results obtained with a new class of molluscicidal compounds—the organo-tins—which cause snail mortality in concentrations as low as those of any of the other molluscicides tested. PMID:13961665

Agrochemicals increase risk of human schistosomiasis by supporting higher densities of intermediate hosts.

PubMed

Halstead, Neal T; Hoover, Christopher M; Arakala, Arathi; Civitello, David J; De Leo, Giulio A; Gambhir, Manoj; Johnson, Steve A; Jouanard, Nicolas; Loerns, Kristin A; McMahon, Taegan A; Ndione, Raphael A; Nguyen, Karena; Raffel, Thomas R; Remais, Justin V; Riveau, Gilles; Sokolow, Susanne H; Rohr, Jason R

2018-02-26

Schistosomiasis is a snail-borne parasitic disease that ranks among the most important water-based diseases of humans in developing countries. Increased prevalence and spread of human schistosomiasis to non-endemic areas has been consistently linked with water resource management related to agricultural expansion. However, the role of agrochemical pollution in human schistosome transmission remains unexplored, despite strong evidence of agrochemicals increasing snail-borne diseases of wildlife and a projected 2- to 5-fold increase in global agrochemical use by 2050. Using a field mesocosm experiment, we show that environmentally relevant concentrations of fertilizer, a herbicide, and an insecticide, individually and as mixtures, increase densities of schistosome-infected snails by increasing the algae snails eat and decreasing densities of snail predators. Epidemiological models indicate that these agrochemical effects can increase transmission of schistosomes. Identifying agricultural practices or agrochemicals that minimize disease risk will be critical to meeting growing food demands while improving human wellbeing.

Schistosomiasis in Zambia: a systematic review of past and present experiences.

PubMed

Kalinda, Chester; Chimbari, Moses J; Mukaratirwa, Samson

2018-04-30

The speedy rate of change in the environmental and socio-economics factors may increase the incidence, prevalence and risk of schistosomiasis infections in Zambia. However, available information does not provide a comprehensive understanding of the biogeography and distribution of the disease, ecology and population dynamics of intermediate host snails. The current study used an information-theoretical approach to understand the biogeography and prevalence schistosomiasis and identified knowledge gaps that would be useful to improve policy towards surveillance and eradication of intermediate hosts snails in Zambia. To summarise the existing knowledge and build on past and present experiences of schistosomiasis epidemiology for effective disease control in Zambia, a systematic search of literature for the period 2000-2017 was done on PubMed, Google Scholar and EBSCOhost. Using the key words: 'Schistosomiasis', 'Biomphalaria', 'Bulinus', 'Schistosoma mansoni', 'Schistosoma haematobium', and 'Zambia', in combination with Booleans terms 'AND' and 'OR', published reports/papers were obtained and reviewed independently for inclusion. Thirteen papers published in English that fulfilled the inclusion criteria were selected for the final review. The papers suggest that the risk of infection has increased over the years and this has been attributed to environmental, socio-economic and demographic factors. Furthermore, schistosomiasis is endemic in many parts of the country with infection due to Schistosoma haematobium being more prevalent than that due to S. mansoni. This review also found that S. haematobium was linked to genital lesions, thus increasing risks of contracting other diseases such as HIV and cervical cancer. For both S. haematobium and S. mansoni, environmental, socio-economic, and demographic factors were influential in the transmission and prevalence of the disease and highlight the need for detailed knowledge on ecological modelling and mapping the distribution of the disease and intermediate host snails for effective implementation of control strategies.

High prevalence of cattle fascioliasis in coastal areas of Thua Thien Hue province, Vietnam.

PubMed

Nguyen, Nga Thi; LE, Thinh Cong; Vo, Minh Duc Co; VAN Cao, Hoang; Nguyen, Ly Thi; Ho, Khanh Thi; Nguyen, Quyet Ngoc; Tran, Vui Quang; Matsumoto, Yasunobu

2017-06-16

In Vietnam, especially central Vietnam, patients with fascioliasis are increasingly being reported. Since the fascioliasis is zoonotic, survey on the cattle fascioliasis should be informative for the control of human fascioliasis. In this study, the prevalence of cattle fascioliasis as well as the density of the intermediate host snails, Lymnaea swinhoei and L. viridis, were studied in Thua Thien Hue (TTH) province during 2014-2015. A total of 572 cattle feces were examined from 27 communes in 9 districts. Fasciola eggs were detected in cattle from 24 communes with an average prevalence of 23.4% (134/ 572). The highest prevalence was detected in cattle in the coastal plain terrain (31.0%) followed by plain (25.5%), mountain (21.7%), and low hilly (16.2%) terrains. The highest proportion of heavy infection (>200 EPG) was observed in the coastal plain terrain (36.1%), followed by mountains (20.0%), low hills (13.0%), and plains (8.9%). Low number of heavy infection, as well as relatively low prevalence in low hills and plains were associated with the extensive use of anti-fluke treatments. High number of intermediate host snails in low hilly and plain terrains also indicate high risk of fascioliasis. In this study, the density of Lymnaea snails in the coastal plain terrain was found to be very high (17.3 snails/m 2 ) compared to that in previous studies. This is the first report indicating the recent expansion of cattle fascioliasis in the coastal region in Vietnam.

Proteomic Analysis of the Schistosoma mansoni Miracidium.

PubMed

Wang, Tianfang; Zhao, Min; Rotgans, Bronwyn A; Strong, April; Liang, Di; Ni, Guoying; Limpanont, Yanin; Ramasoota, Pongrama; McManus, Donald P; Cummins, Scott F

2016-01-01

Despite extensive control efforts, schistosomiasis continues to be a major public health problem in developing nations in the tropics and sub-tropics. The miracidium, along with the cercaria, both of which are water-borne and free-living, are the only two stages in the life-cycle of Schistosoma mansoni which are involved in host invasion. Miracidia penetrate intermediate host snails and develop into sporocysts, which lead to cercariae that can infect humans. Infection of the snail host by the miracidium represents an ideal point at which to interrupt the parasite's life-cycle. This research focuses on an analysis of the miracidium proteome, including those proteins that are secreted. We have identified a repertoire of proteins in the S. mansoni miracidium at 2 hours post-hatch, including proteases, venom allergen-like proteins, receptors and HSP70, which might play roles in snail-parasite interplay. Proteins involved in energy production and conservation were prevalent, as were proteins predicted to be associated with defence. This study also provides a strong foundation for further understanding the roles that neurohormones play in host-seeking by schistosomes, with the potential for development of novel anthelmintics that interfere with its various life-cycle stages.

Population genetics of Schistosoma japonicum within the Philippines suggest high levels of transmission between humans and dogs.

PubMed

Rudge, James W; Carabin, Hélène; Balolong, Ernesto; Tallo, Veronica; Shrivastava, Jaya; Lu, Da-Bing; Basáñez, María-Gloria; Olveda, Remigio; McGarvey, Stephen T; Webster, Joanne P

2008-01-01

Schistosoma japonicum, which remains a major public health problem in the Philippines and mainland China, is the only schistosome species for which zoonotic transmission is considered important. While bovines are suspected as the main zoonotic reservoir in parts of China, the relative contributions of various non-human mammals to S. japonicum transmission in the Philippines remain to be determined. We examined the population genetics of S. japonicum in the Philippines in order to elucidate transmission patterns across host species and geographic areas. S. japonicum miracidia (hatched from eggs within fecal samples) from humans, dogs, pigs and rats, and cercariae shed from snail-intermediate hosts, were collected across two geographic areas of Samar Province. Individual isolates were then genotyped using seven multiplexed microsatellite loci. Wright's F(ST) values and phylogenetic trees calculated for parasite populations suggest a high frequency of parasite gene-flow across definitive host species, particularly between dogs and humans. Parasite genetic differentiation between areas was not evident at the definitive host level, possibly suggesting frequent import and export of infections between villages, although there was some evidence of geographic structuring at the snail-intermediate host level. These results suggest very high levels of transmission across host species, and indicate that the role of dogs should be considered when planning control programs. Furthermore, a regional approach to treatment programs is recommended where human migration is extensive.

Specific detection of Angiostrongylus cantonensis in the snail Achatina fulica using a loop-mediated isothermal amplification (LAMP) assay.

PubMed

Liu, Chun-Yan; Song, Hui-Qun; Zhang, Ren-Li; Chen, Mu-Xin; Xu, Min-Jun; Ai, Lin; Chen, Xiao-Guang; Zhan, Xi-Mei; Liang, Shao-Hui; Yuan, Zi-Guo; Lin, Rui-Qing; Zhu, Xing-Quan

2011-08-01

Angiostrongylus cantonensis, a rat lungworm, can cause eosinophilic meningitis and angiostrongyliasis in humans following ingestion of contaminated foods or intermediate/paratenic hosts with infective larvae. The snail Achatina fulica is one of the important intermediate hosts of A. cantonensis and is commonly eaten by humans in some countries. In the present study, we developed a loop-mediated isothermal amplification (LAMP) method for the specific detection of A. cantonensis in Ac. fulica. Primers for LAMP were designed based on the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA (rDNA) of A. cantonensis. Specificity tests showed that only the products of A. cantonensis were detected when DNA samples of A. cantonensis and the heterologous control samples Anisakis simplex s.s, Trichuris trichiura, Toxocara canis, Trichinella spiralis and Ascaris lumbricoides were amplified by LAMP. Sensitivity evaluation indicated that the LAMP assay is 10 times more sensitive than the conventional polymerase chain reaction (PCR) assay. The established LAMP assay is rapid, inexpensive and easy to be performed. It can be used in clinical applications for rapid and sensitive detection of A. cantonensis in snails, which has implications for the effective control of angiostrongyliasis. Copyright © 2011 Elsevier Ltd. All rights reserved.

The interaction of light and gravity on the transmission of Echinostoma caproni (Digenea: Echinostomatidae) cercariae to the second intermediate host, Biomphalaria glabrata (Gastropoda: Pulmonata).

PubMed

Platt, Thomas R; Greenlee, Hali; Zelmer, Derek A

2010-04-01

The current experiments were designed to assess the interaction of light and gravity on the transmission of Echinostoma caproni cercariae to the second intermediate host, Biomphalaria glabrata. Transmission chambers were constructed of clear polyvinyl chloride pipe covered with a black sleeve to exclude light. Snails were constrained within the chamber to prevent movement, while permitting the cercariae to swim freely. A trial consisted of 2 infected B. glabrata shedding E. caproni cercariae placed at the center of the chamber with 5 uninfected B. glabrata placed 10 cm above and below the shedding snails as sentinels. Three experiments, consisting of 12 trials each, were conducted under the following lighting conditions, i.e., above and below the transmission chamber, and in complete darkness. In all 3 experiments, the proportion of metacercariae was significantly higher in snails at the top of the chamber. The results suggest that a negative geotaxis is the primary factor in the initial dispersal of E. caproni cercariae. Coupling negative geotaxis and positive phototaxis (light from above) resulted in a significantly higher proportion of metacercariae in sentinel snails at the top of the transmission chamber when corrected for cercarial density. There was no significant difference in the proportion of metacercariae in snails at the top or bottom of the transmission chamber with light at the bottom of the chamber or in complete darkness. Cercariae of E. caproni only respond to light in context, i.e., from above, and ignore the light stimulus when it comes from an unexpected location (bottom of the water column). Significantly greater numbers of cercariae were released from shedding snails when light was present, suggesting that emergence of cercariae from B. glabrata is dependent on light regardless of the position of the light source.

The Intestinal Microbiota of Tadpoles Differs from Those of Syntopic Aquatic Invertebrates.

PubMed

Lyra, Mariana L; Bletz, Molly C; Haddad, Célio F B; Vences, Miguel

2017-11-20

Bacterial communities associated to eukaryotes play important roles in the physiology, development, and health of their hosts. Here, we examine the intestinal microbiota in tadpoles and aquatic invertebrates (insects and gastropods) to better understand the degree of specialization in the tadpole microbiotas. Samples were collected at the same time in one pond, and the V4 region of the bacterial 16S rRNA gene was sequenced with Illumina amplicon sequencing. We found that bacterial richness and diversity were highest in two studied snail individuals, intermediate in tadpoles, and lowest in the four groups of aquatic insects. All groups had substantial numbers of exclusive bacterial operational taxonomic units (OTUs) in their guts, but also shared a high proportion of OTUs, probably corresponding to transient environmental bacteria. Significant differences were found for all pairwise comparisons of tadpoles and snails with the major groups of insects, but not among insect groups or between snails and tadpoles. The similarity between tadpoles and snails may be related to similar feeding mode as both snails and tadpoles scratch biofilms and algae from surfaces; however, this requires confirmation due to low sample sizes. Overall, the gut microbiota differences found among syntopic aquatic animals are likely shaped by both food preferences and host identity.

The biology of Echinoparyphium (Trematoda, Echinostomatidae).

PubMed

Huffman, Jane E; Fried, Bernard

2012-09-01

Echinoparyphium species are common, widely distributed intestinal parasites causing disease in animals worldwide. Intermediate hosts include snails, bivalves, and fish, whereas the definitive hosts are mainly birds and mammals. This review examines the significant literature on Echinoparyphium. Descriptive studies, life cycle, experimental and manipulative studies, and biochemical and molecular studies are presented. The influence of environmental factors, and toxic pollutants, are reviewed as well as studies on the pathology of Echinoparyphium.

Enzootic Angiostrongyliasis in Guangzhou, China, 2008–2010

PubMed Central

Yang, Xiao; Qu, Zhenyu; He, Hualiang; Zheng, Xiaoying; He, Ai; Wu, Yu; Liu, Qian; Zhang, Dongjing; Wu, Zhongdao; Li, Zhuoya; Zhan, Ximei

2012-01-01

This study was conducted to gain an understanding of the Angiostrongylus cantonensis infection status of rodent definitive host, snail intermediate host, and local residents in Guangzhou, China. A total of 430 rats were captured and 23 rats, from two species, were infected, with an average infection rate of 5.35%. A total of 795 Achatina fulica snails and 734 Pomacea canaliculata snails were collected. The average infection rates of these two species were 13.96% (111 of 795) and 1.50% (11 of 734), respectively. As for the seroprevalence of different occupations, the rate among the “general group” was significantly lower than the “occupational group.” From this survey, Guangzhou is implicated to be the natural focus of Angiostrongylus cantonensis. Rattus norvegicus and Achatina fulica play important roles in spreading this nematode in Guangzhou. Residents who live in Guangzhou, especially those working in certain industries such as agriculture, food-making, and aquaculture, face a higher risk of infection. PMID:22556086

Relationships between nutrient enrichment, pleurocerid snail density and trematode infection rate in streams

USGS Publications Warehouse

Ciparis, Serena; Iwanowicz, Deborah D.; Voshell, J. Reese

2013-01-01

Summary 1. Nutrient enrichment is a widespread environmental problem in freshwater ecosystems. Eutrophic conditions caused by nutrient enrichment may result in a higher prevalence of infection by trematode parasites in host populations, due to greater resource availability for the molluscan first intermediate hosts. 2. This study examined relationships among land use, environmental variables indicating eutrophication, population density of the pleurocerid snail, Leptoxis carinata, and trematode infections. Fifteen study sites were located in streams within the Shenandoah River catchment (Virginia, U.S.A.), where widespread nutrient enrichment has occurred. 3. Snail population density had a weak positive relationship with stream water nutrient concentration. Snail population density also increased as human activities within stream catchments increased, but density did not continue to increase in catchments where anthropogenic disturbance was greatest. 4. Cercariae from five families of trematodes were identified in L. carinata, and infection rate was generally low (<10%). Neither total infection rate nor the infection rate of individual trematode types showed a positive relationship with snail population density, nutrients or land use. 5. There were statistically significant but weak relationships between the prevalence of infection by two trematode families and physical and biological variables. The prevalence of Notocotylidae was positively related to water depth, which may be related to habitat use by definitive hosts. Prevalence of Opecoelidae had a negative relationship with orthophosphate concentration and a polynomial relationship with chlorophyll a concentration. Transmission of Opecoelid trematodes between hosts may be inhibited by eutrophic conditions. 6. Leptoxis carinata appears to be a useful species for monitoring the biological effects of eutrophication and investigating trematode transmission dynamics in lotic systems.

Effects of temperature and salinity on emergence of Gynaecotyla adunca cercariae from the intertidal gastropod Ilyanassa obsoleta.

PubMed

Koprivnikar, J; Ellis, D; Shim, K C; Forbes, M R

2014-04-01

Fluctuating abiotic conditions within intertidal zones have been shown to affect the emergence of free-swimming trematode infectious stages (cercariae) from their gastropod first intermediate hosts, likely reflecting adaptations to maximize transmission in this marine environment. We investigated the influences of temperature (17 and 22 C) and salinity (25, 30, and 35 ppt) on the emergence of marine cercariae (Gynaecotyla adunca) from their mud snail first intermediate host ( Ilyanassa obsoleta ). Cercariae emerged in greater numbers at 22 C and the 2 lowest salinities, with a sharp decrease at the 35 ppt level, but there was no interactive effect. We discuss these patterns of G. adunca emergence as possible adaptations to facilitate transmission to its amphipod second intermediate host ( Corophium volutator ) in conditions common to the Upper Bay of Fundy.

Differential Protein Expression in the Hemolymph of Bithynia siamensis goniomphalos Infected with Opisthorchis viverrini

PubMed Central

Suwannatrai, Kulwadee; Suwannatrai, Apiporn; Tabsripair, Pairat; Welbat, Jariya Umka; Tangkawattana, Sirikachorn; Cantacessi, Cinzia; Mulvenna, Jason; Tesana, Smarn; Loukas, Alex

2016-01-01

Bithynia siamensis goniomphalos is a freshwater snail that serves as the first intermediate host of the human liver fluke Opisthorchis viverrini. This parasite is a major public health problem in different countries throughout the Greater Mekong sub-region (Thailand, southern Vietnam, Lao PDR and Cambodia). Chronic O. viverrini infection also results in a gradual increase of fibrotic tissues in the biliary tract that are associated with hepatobiliary diseases and contribute to cholangiocarcinoma (a fatal type of bile duct cancer). Infectivity of the parasite in the snail host is strongly correlated with destruction of helminths by the snail’s innate immune system, composed of cellular (hemocyte) and humoral (plasma) defense factors. To better understand this important host-parasite interface we applied sequential window acquisition of all theoretical spectra mass spectrometry (SWATH-MS) to identify and quantify the proteins from the hemolymph of B. siamensis goniomphalos experimentally infected with O. viverrini and compare them to non-infected snails (control group). A total of 362 and 242 proteins were identified in the hemocytes and plasma, respectively. Of these, 145 and 117 proteins exhibited significant differences in expression upon fluke infection in hemocytes and plasma, respectively. Among the proteins with significantly different expression patterns, we found proteins related to immune response (up-regulated in both hemocyte and plasma of infected snails) and proteins belonging to the structural and motor group (mostly down-regulated in hemocytes but up-regulated in plasma of infected snails). The proteins identified and quantified in this work will provide important information for the understanding of the factors involved in snail defense against O. viverrini and might facilitate the development of new strategies to control O. viverrini infection in endemic areas. PMID:27893749

The ecology of vector snail habitats and mosquito breeding-places

PubMed Central

Muirhead-Thomson, R. C.

1958-01-01

The ecology of freshwater snails—in particular those which act as intermediate hosts of bilharziasis—is reviewed in the light of the much more extensive knowledge available on the breeding-places of anopheline mosquitos. Experimental ecological methods are recommended for the field and laboratory investigation of a number of common problems involved in the study of snail habitats and mosquito breeding-places. Among the environmental factors discussed are temperature, oxygen concentration, water movement, pollution and salinity. Sampling methods for estimating populations of both snails and mosquito larvae are also described. An attempt is made to show how malacologists and entomologists alike would benefit from improved facilities for keeping abreast of general developments in the wider field of freshwater ecology. PMID:13596888

Recovery of primary sporocysts in vivo in the Schistosoma mansoni/Biomphalaria glabrata model using a simple fixation method suitable for extraction of genomic DNA and RNA.

PubMed

Allienne, Jean-François; Théron, André; Gourbal, Benjamin

2011-09-01

Detailed studies of host/parasite interactions are currently limited because in situ gene sequencing or monitoring of parasite gene expression is so far limited to genes presenting a high loci copy number in the Schistosome genome or a high level of expression. Indeed, how to investigate the host parasite molecular interplay when parasites are not directly accessible in vivo? Here we describe a method to circumvent this problem and to analyze DNA and RNA of Schistosoma mansoni during the interaction with its intermediate snail host Biomphalaria glabrata. We propose a technique for improved DNA and RNA extraction from the intra-molluscan stage of the parasite recovered after fixation of infected snails in Raillet-Henry solution. The extractions can be used for genetic analysis, transcription studies and microsatellite genotyping. Copyright © 2011 Elsevier Inc. All rights reserved.

High prevalence of cattle fascioliasis in coastal areas of Thua Thien Hue province, Vietnam

PubMed Central

NGUYEN, Nga Thi; LE, Thinh Cong; VO, Minh Duc Co; VAN CAO, Hoang; NGUYEN, Ly Thi; HO, Khanh Thi; NGUYEN, Quyet Ngoc; TRAN, Vui Quang; MATSUMOTO, Yasunobu

2017-01-01

In Vietnam, especially central Vietnam, patients with fascioliasis are increasingly being reported. Since the fascioliasis is zoonotic, survey on the cattle fascioliasis should be informative for the control of human fascioliasis. In this study, the prevalence of cattle fascioliasis as well as the density of the intermediate host snails, Lymnaea swinhoei and L. viridis, were studied in Thua Thien Hue (TTH) province during 2014–2015. A total of 572 cattle feces were examined from 27 communes in 9 districts. Fasciola eggs were detected in cattle from 24 communes with an average prevalence of 23.4% (134/ 572). The highest prevalence was detected in cattle in the coastal plain terrain (31.0%) followed by plain (25.5%), mountain (21.7%), and low hilly (16.2%) terrains. The highest proportion of heavy infection (>200 EPG) was observed in the coastal plain terrain (36.1%), followed by mountains (20.0%), low hills (13.0%), and plains (8.9%). Low number of heavy infection, as well as relatively low prevalence in low hills and plains were associated with the extensive use of anti-fluke treatments. High number of intermediate host snails in low hilly and plain terrains also indicate high risk of fascioliasis. In this study, the density of Lymnaea snails in the coastal plain terrain was found to be very high (17.3 snails/m2) compared to that in previous studies. This is the first report indicating the recent expansion of cattle fascioliasis in the coastal region in Vietnam. PMID:28458272

The Occurrence of the Rat Lungworm, Angiostrongylus cantonensis, in Nonindigenous Snails in the Gulf of Mexico Region of the United States

PubMed Central

Qvarnstrom, Yvonne; Bishop, Henry S; da Silva, Alexandre J; Carter, Jacoby; White-Mclean, Jodi; Smith, Trevor

2013-01-01

Nonindigenous apple snails, Pomacea maculata (formerly Pomacea insularum), are currently spreading rapidly through the southeastern United States. This mollusk serves as an intermediate host of the rat lungworm parasite (Angiostrongylus cantonensis), which can cause eosinophilic meningitis in humans who consume infected mollusks. A PCR-based detection assay was used to test nonindigenous apple snails for the rat lungworm parasite in Louisiana, Texas, Mississippi, and Florida. Only apple snails obtained from the New Orleans, Louisiana, area tested positive for the parasite. These results provide the first evidence that Angiostrongylus cantonensis does occur in nonindigenous apple snails in the southeastern United States. Additionally, Angiostrongylus cantonensis was identified in the terrestrial species Achatina fulica in Miami, Florida, indicating that rat lungworm is now established in Florida as well as Louisiana. Although the study suggests that the rat lungworm is not widespread in the Gulf States region, the infected snail population could still pose a risk to human health and facilitate the spread of the parasite to new areas. PMID:23901374

The occurrence of the rat lungworm, Angiostrongylus cantonensis, in nonindigenous snails in the Gulf of Mexico region of the United States

USGS Publications Warehouse

Teem, John L.; Qvarnstrom, Yvonne; Bishop, Henry S.; da Silva, Alexandre J.; Carter, Jacoby; White-McLean, Jodi; Smith, Trevor

2013-01-01

Nonindigenous apple snails, Pomacea maculata (formerly Pomacea insularum), are currently spreading rapidly through the southeastern United States. This mollusk serves as an intermediate host of the rat lungworm parasite (Angiostrongylus cantonensis), which can cause eosinophilic meningitis in humans who consume infected mollusks. A PCR-based detection assay was used to test nonindigenous apple snails for the rat lungworm parasite in Louisiana, Texas, Mississippi, and Florida. Only apple snails obtained from the New Orleans, Louisiana, area tested positive for the parasite. These results provide the first evidence that Angiostrongylus cantonensis does occur in nonindigenous apple snails in the southeastern United States. Additionally, Angiostrongylus cantonensis was identified in the terrestrial species Achatina fulica in Miami, Florida, indicating that rat lungworm is now established in Florida as well as Louisiana. Although the study suggests that the rat lungworm is not widespread in the Gulf States region, the infected snail population could still pose a risk to human health and facilitate the spread of the parasite to new areas.

The role of rice fields, fish ponds and water canals for transmission of fish-borne zoonotic trematodes in aquaculture ponds in Nam Dinh Province, Vietnam.

PubMed

Madsen, Henry; Dung, Bui Thi; The, Dang Tat; Viet, Nguyen Khue; Dalsgaard, Anders; Van, Phan Thi

2015-12-08

Fish-borne zoonotic trematodes (FZT), such as Clonorchis sinensis, Opistorchis viverini (Opisthorchiidae) and intestinal trematodes of the family Heterophyidae, constitute a public health hazard in Vietnam and infections with these trematodes has been linked to consumption of raw or undercooked fish from aquaculture. The FZT transmission pathways, however, are more complicated than just the presence of intermediate snail hosts in aquaculture ponds as ponds may exchange water with surrounding habitats such as rice fields and irrigation canals and thereby these surrounding habitats may be a source of snails and cercariae and contribute to FZT infection in cultured fish. This is a longitudinal descriptive study on selected farms (n = 30) in Nam Dinh Province which is endemic for FZT. At each farm, we sampled one pond, a small irrigation canal used to supply the pond with water, and a nearby rice field. At each of these three sites, we estimated the density of the FZT intermediate snail hosts and determined their trematode infection status. Comparative analysis was performed for the prevalence and density of FZT infections in fish and snails. Species of the Thiaridae, and most notably Melanoides tuberculata, the most important host species for FZT belonging to the Heterophyidae, were particularly abundant in ponds and small canals, i.e. M. tuberculata was found in 27 ponds and 13 small canals. Bithynia fuchsiana, a potential host for both Heterophyidae and Opisthorchiidae, was rarely found in fish ponds but common in rice fields. A total of 12 types of cercariae were found in the snails and pleurolophocercous cercariae, primarily FZT, constituted about 40 % of all cercarial infections. The fish species cultured were mainly carp species and Haplorchis pumilio was the dominating trematode species infecting fish. Clonorchis spp. were not recorded in any of the ponds. FZT transmission to fish was intense during the summer period (May-June to November) but less intense during the winter months (December-January) partly because cercarial emergence ceases due to the low temperature. Our findings highlight the complexity of FZT transmission within aquaculture farm settings and suggest that efforts to control these infections must take a holistic approach using interventions against all stages of the transmission cycle.

Population genetics of the Schistosoma snail host Bulinus truncatus in Egypt.

PubMed

Zein-Eddine, Rima; Djuikwo-Teukeng, Félicité F; Dar, Yasser; Dreyfuss, Gilles; Van den Broeck, Frederik

2017-08-01

The tropical freshwater snail Bulinus truncatus serves as an important intermediate host of several human and cattle Schistosoma species in many African regions. Despite some ecological and malacological studies, there is no information on the genetic diversity of B. truncatus in Egypt. Here, we sampled 70-100 snails in ten localities in Upper Egypt and the Nile Delta. Per locality, we sequenced 10 snails at a partial fragment of the cytochrome c oxidase subunit 1 gene (cox1) and we genotyped 25-30 snails at six microsatellite markers. A total of nine mitochondrial haplotypes were detected, of which five were unique to the Nile Delta and three were unique to Upper Egypt, indicating that snail populations may have evolved independently in both regions. Bayesian clustering and hierarchical F-statistics using microsatellite markers further revealed strong population genetic structure at the level of locality. Observed heterozygosity was much lower compared to what is expected under random mating, which could be explained by high selfing rates, population size reductions and to a lesser extent by the Wahlund effect. Despite these observations, we found signatures of gene flow and cross-fertilization, even between snails from the Nile Delta and Upper Egypt, indicating that B. truncatus can travel across large distances in Egypt. These observations could have serious consequences for disease epidemiology, as it means that infected snails from one region could rapidly and unexpectedly spark a new epidemic in another distant region. This could be one of the factors explaining the rebound of human Schistosoma infections in the Nile Delta, despite decades of sustained schistosomiasis control. Copyright © 2017 Elsevier B.V. All rights reserved.

Hydrological modelling of snail dispersal patterns in Msambweni, Kenya and potential resurgence of Schistosoma haematobium transmission.

PubMed

Clennon, J A; King, C H; Muchiri, E M; Kitron, U

2007-05-01

Urinary schistosomiasis is an important source of human morbidity in Msambweni, Kenya, where the intermediate host snail, Bulinus nasutus is found in ponds and water pools. In the past, aquatic habitats in the area have been studied separately; however, recent collections of B. nasutus snails and shells indicated that many of these ponds are in fact connected during and following sufficient rains. Satellite imagery and a geographical information system (GIS) were used to survey the main water courses and potential drainage routes, to locate potential source populations of snails and to determine probable snail dispersal routes. The 2 water bodies implicated as being the most important Schistosoma haematobium transmission foci in the area were found to differ in their degree of connectivity to other B. nasutus source habitats. One pond becomes connected even after normal rains, while the other pond requires prolonged rains or flooding to become connected with source habitats. Consequently, the transmission foci differ in their susceptibility to snail population control measures. Spatially explicit dispersal models that consider the spatial and temporal patterns of connectivity between aquatic habitats will contribute to improved snail surveillance and more focused control for urinary schistosomiasis at a local level.

Biomphalaria glabrata transcriptome: cDNA microarray profiling identifies resistant- and susceptible-specific gene expression in haemocytes from snail strains exposed to Schistosoma mansoni

PubMed Central

Lockyer, Anne E; Spinks, Jenny; Kane, Richard A; Hoffmann, Karl F; Fitzpatrick, Jennifer M; Rollinson, David; Noble, Leslie R; Jones, Catherine S

2008-01-01

Background Biomphalaria glabrata is an intermediate snail host for Schistosoma mansoni, one of the important schistosomes infecting man. B. glabrata/S. mansoni provides a useful model system for investigating the intimate interactions between host and parasite. Examining differential gene expression between S. mansoni-exposed schistosome-resistant and susceptible snail lines will identify genes and pathways that may be involved in snail defences. Results We have developed a 2053 element cDNA microarray for B. glabrata containing clones from ORESTES (Open Reading frame ESTs) libraries, suppression subtractive hybridization (SSH) libraries and clones identified in previous expression studies. Snail haemocyte RNA, extracted from parasite-challenged resistant and susceptible snails, 2 to 24 h post-exposure to S. mansoni, was hybridized to the custom made cDNA microarray and 98 differentially expressed genes or gene clusters were identified, 94 resistant-associated and 4 susceptible-associated. Quantitative PCR analysis verified the cDNA microarray results for representative transcripts. Differentially expressed genes were annotated and clustered using gene ontology (GO) terminology and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis. 61% of the identified differentially expressed genes have no known function including the 4 susceptible strain-specific transcripts. Resistant strain-specific expression of genes implicated in innate immunity of invertebrates was identified, including hydrolytic enzymes such as cathepsin L, a cysteine proteinase involved in lysis of phagocytosed particles; metabolic enzymes such as ornithine decarboxylase, the rate-limiting enzyme in the production of polyamines, important in inflammation and infection processes, as well as scavenging damaging free radicals produced during production of reactive oxygen species; stress response genes such as HSP70; proteins involved in signalling, such as importin 7 and copine 1, cytoplasmic intermediate filament (IF) protein and transcription enzymes such as elongation factor 1α and EF-2. Conclusion Production of the first cDNA microarray for profiling gene expression in B. glabrata provides a foundation for expanding our understanding of pathways and genes involved in the snail internal defence system (IDS). We demonstrate resistant strain-specific expression of genes potentially associated with the snail IDS, ranging from signalling and inflammation responses through to lysis of proteinacous products (encapsulated sporocysts or phagocytosed parasite components) and processing/degradation of these targeted products by ubiquitination. PMID:19114004

Biomphalaria glabrata transcriptome: cDNA microarray profiling identifies resistant- and susceptible-specific gene expression in haemocytes from snail strains exposed to Schistosoma mansoni.

PubMed

Lockyer, Anne E; Spinks, Jenny; Kane, Richard A; Hoffmann, Karl F; Fitzpatrick, Jennifer M; Rollinson, David; Noble, Leslie R; Jones, Catherine S

2008-12-29

Biomphalaria glabrata is an intermediate snail host for Schistosoma mansoni, one of the important schistosomes infecting man. B. glabrata/S. mansoni provides a useful model system for investigating the intimate interactions between host and parasite. Examining differential gene expression between S. mansoni-exposed schistosome-resistant and susceptible snail lines will identify genes and pathways that may be involved in snail defences. We have developed a 2053 element cDNA microarray for B. glabrata containing clones from ORESTES (Open Reading frame ESTs) libraries, suppression subtractive hybridization (SSH) libraries and clones identified in previous expression studies. Snail haemocyte RNA, extracted from parasite-challenged resistant and susceptible snails, 2 to 24 h post-exposure to S. mansoni, was hybridized to the custom made cDNA microarray and 98 differentially expressed genes or gene clusters were identified, 94 resistant-associated and 4 susceptible-associated. Quantitative PCR analysis verified the cDNA microarray results for representative transcripts. Differentially expressed genes were annotated and clustered using gene ontology (GO) terminology and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis. 61% of the identified differentially expressed genes have no known function including the 4 susceptible strain-specific transcripts. Resistant strain-specific expression of genes implicated in innate immunity of invertebrates was identified, including hydrolytic enzymes such as cathepsin L, a cysteine proteinase involved in lysis of phagocytosed particles; metabolic enzymes such as ornithine decarboxylase, the rate-limiting enzyme in the production of polyamines, important in inflammation and infection processes, as well as scavenging damaging free radicals produced during production of reactive oxygen species; stress response genes such as HSP70; proteins involved in signalling, such as importin 7 and copine 1, cytoplasmic intermediate filament (IF) protein and transcription enzymes such as elongation factor 1alpha and EF-2. Production of the first cDNA microarray for profiling gene expression in B. glabrata provides a foundation for expanding our understanding of pathways and genes involved in the snail internal defence system (IDS). We demonstrate resistant strain-specific expression of genes potentially associated with the snail IDS, ranging from signalling and inflammation responses through to lysis of proteinacous products (encapsulated sporocysts or phagocytosed parasite components) and processing/degradation of these targeted products by ubiquitination.

Evaluation of sodium fluoride toxicity in Schistosoma infected snails: assessment of antioxidants, antiapoptotic, hypoprotein and hypocholesterol activities.

PubMed

Koriem, Khaled M M; Shamsuri, Radziyah B; Ubaidillah, Asliza M

2016-12-01

The snails' tissues represents an intermediate or secondary host for Schistosoma sporocysts where, germ cells within the secondary sporocyst begin to divide to produce thousands of cercariae capable of infecting humans. The aim of the study was to evaluate the toxicity of sodium fluoride in Schistosoma snails' tissue homogenates. A total number of 264 different Schistosoma snails were collected from eight drainage water resources and divided into control uninfected and infected snails; where infected snails divided into four group; the first group without any treatment while second, third and fourth groups immersed in 25, 50 and 100 mg sodium fluoride/L during the period of 4 weeks then the snails' hemolymph and tissue homogenates were prepared to evaluate the snail' tissue antioxidants, protein content, lipid profile and apoptosis. The results obtained revealed that superoxide dismutase, glutathione- S -transferase, glutathione peroxidase, catalase, reduced glutathione, glutathione reductase levels were decreased while malondialdehyde, protein carbonyl, total protein, albumin, globulin, cholesterol, low density lipoprotein and triglycerides levels were increased in Schistosoma infected snails' tissues. Schistosoma also induced apoptosis in snails' tissues homogenates. Sodium fluoride restores all the above parameters to approach the control uninfected snails levels. In conclusion, sodium fluoride inhibits oxidative stress and apoptosis produced in Schistosoma infected snails and consequently it is be useful to be used in Schistosoma infection inhibition where sodium fluoride at higher dose was more effective than the lower two doses.

From first to second and back to first intermediate host: the unusual transmission route of Curtuteria australis (Digenea: Echinostomatidae).

PubMed

McFarland, L H; Mouritsen, K N; Poulin, Robert

2003-06-01

The trematode Curtuteria australis uses the whelk Cominella glandiformis as first intermediate host and the cockle Austrovenus stutchburyi as second intermediate host before maturing in shorebirds. The whelk also happen to be an important predator of cockles on intertidal mudflats. In this study we show that whelks can act as temporary paratenic hosts for the trematode. A single whelk feeding on 1 cockle can ingest large numbers of metacercariae, which remain within the whelk for 1-3 days before passing out in feces. The viability of these metacercariae assessed as the percentage capable of successfully excysting under conditions simulating those inside a bird's digestive tract, is lower after passage through a whelk (48%) than before (59%). Still, given that shorebird definitive hosts prey on whelks as well as cockles, survival inside the whelk allows C. australis to complete its life cycle: overall, though, whelk predation is likely to be an important sink for the trematode population. To our knowledge, this is the first report of a trematode using a snail as both first intermediate host and paratenic host, offering an alternative transmission route for the parasite as a result of the unusual trophic relationships of its hosts.

Parasite infection alters nitrogen cycling at the ecosystem scale.

PubMed

Mischler, John; Johnson, Pieter T J; McKenzie, Valerie J; Townsend, Alan R

2016-05-01

Despite growing evidence that parasites often alter nutrient flows through their hosts and can comprise a substantial amount of biomass in many systems, whether endemic parasites influence ecosystem nutrient cycling, and which nutrient pathways may be important, remains conjectural. A framework to evaluate how endemic parasites alter nutrient cycling across varied ecosystems requires an understanding of the following: (i) parasite effects on host nutrient excretion; (ii) ecosystem nutrient limitation; (iii) effects of parasite abundance, host density, host functional role and host excretion rate on nutrient flows; and (iv) how this infection-induced nutrient flux compares to other pools and fluxes. Pathogens that significantly increase the availability of a limiting nutrient within an ecosystem should produce a measurable ecosystem-scale response. Here, we combined field-derived estimates of trematode parasite infections in aquatic snails with measurements of snail excretion and tissue stoichiometry to show that parasites are capable of altering nutrient excretion in their intermediate host snails (dominant grazers). We integrated laboratory measurements of host nitrogen excretion with field-based estimates of infection in an ecosystem model and compared these fluxes to other pools and fluxes of nitrogen as measured in the field. Eighteen nitrogen-limited ponds were examined to determine whether infection had a measurable effect on ecosystem-scale nitrogen cycling. Because of their low nitrogen content and high demand for host carbon, parasites accelerated the rate at which infected hosts excreted nitrogen to the water column in a dose-response manner, thereby shifting nutrient stoichiometry and availability at the ecosystem scale. Infection-enhanced fluxes of dissolved inorganic nitrogen were similar to other commonly important environmental sources of bioavailable nitrogen to the system. Additional field measurements within nitrogen-limited ponds indicated that nitrogen flux rates from the periphyton to the water column in high-snail density/high-infection ponds were up to 50% higher than low-infection ponds. By altering host nutrient assimilation/excretion flexibility, parasites could play a widespread, but currently unrecognized, role in ecosystem nutrient cycling, especially when parasite and host abundances are high and hosts play a central role in ecosystem nutrient cycling. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Developmental Regulation of Genes Encoding Universal Stress Proteins in Schistosoma mansoni

PubMed Central

Isokpehi, Raphael D.; Mahmud, Ousman; Mbah, Andreas N.; Simmons, Shaneka S.; Avelar, Lívia; Rajnarayanan, Rajendram V.; Udensi, Udensi K.; Ayensu, Wellington K.; Cohly, Hari H.; Brown, Shyretha D.; Dates, Centdrika R.; Hentz, Sonya D.; Hughes, Shawntae J.; Smith-McInnis, Dominique R.; Patterson, Carvey O.; Sims, Jennifer N.; Turner, Kelisha T.; Williams, Baraka S.; Johnson, Matilda O.; Adubi, Taiwo; Mbuh, Judith V.; Anumudu, Chiaka I.; Adeoye, Grace O.; Thomas, Bolaji N.; Nashiru, Oyekanmi; Oliveira, Guilherme

2011-01-01

The draft nuclear genome sequence of the snail-transmitted, dimorphic, parasitic, platyhelminth Schistosoma mansoni revealed eight genes encoding proteins that contain the Universal Stress Protein (USP) domain. Schistosoma mansoni is a causative agent of human schistosomiasis, a severe and debilitating Neglected Tropical Disease (NTD) of poverty, which is endemic in at least 76 countries. The availability of the genome sequences of Schistosoma species presents opportunities for bioinformatics and genomics analyses of associated gene families that could be targets for understanding schistosomiasis ecology, intervention, prevention and control. Proteins with the USP domain are known to provide bacteria, archaea, fungi, protists and plants with the ability to respond to diverse environmental stresses. In this research investigation, the functional annotations of the USP genes and predicted nucleotide and protein sequences were initially verified. Subsequently, sequence clusters and distinctive features of the sequences were determined. A total of twelve ligand binding sites were predicted based on alignment to the ATP-binding universal stress protein from Methanocaldococcus jannaschii. In addition, six USP sequences showed the presence of ATP-binding motif residues indicating that they may be regulated by ATP. Public domain gene expression data and RT-PCR assays confirmed that all the S. mansoni USP genes were transcribed in at least one of the developmental life cycle stages of the helminth. Six of these genes were up-regulated in the miracidium, a free-swimming stage that is critical for transmission to the snail intermediate host. It is possible that during the intra-snail stages, S. mansoni gene transcripts for universal stress proteins are low abundant and are induced to perform specialized functions triggered by environmental stressors such as oxidative stress due to hydrogen peroxide that is present in the snail hemocytes. This report serves to catalyze the formation of a network of researchers to understand the function and regulation of the universal stress proteins encoded in genomes of schistosomes and their snail intermediate hosts. PMID:22084571

Modeling and Validation of Environmental Suitability for Schistosomiasis Transmission Using Remote Sensing

PubMed Central

Walz, Yvonne; Wegmann, Martin; Dech, Stefan; Vounatsou, Penelope; Poda, Jean-Noël; N'Goran, Eliézer K.; Utzinger, Jürg; Raso, Giovanna

2015-01-01

Background Schistosomiasis is the most widespread water-based disease in sub-Saharan Africa. Transmission is governed by the spatial distribution of specific freshwater snails that act as intermediate hosts and human water contact patterns. Remote sensing data have been utilized for spatially explicit risk profiling of schistosomiasis. We investigated the potential of remote sensing to characterize habitat conditions of parasite and intermediate host snails and discuss the relevance for public health. Methodology We employed high-resolution remote sensing data, environmental field measurements, and ecological data to model environmental suitability for schistosomiasis-related parasite and snail species. The model was developed for Burkina Faso using a habitat suitability index (HSI). The plausibility of remote sensing habitat variables was validated using field measurements. The established model was transferred to different ecological settings in Côte d’Ivoire and validated against readily available survey data from school-aged children. Principal Findings Environmental suitability for schistosomiasis transmission was spatially delineated and quantified by seven habitat variables derived from remote sensing data. The strengths and weaknesses highlighted by the plausibility analysis showed that temporal dynamic water and vegetation measures were particularly useful to model parasite and snail habitat suitability, whereas the measurement of water surface temperature and topographic variables did not perform appropriately. The transferability of the model showed significant relations between the HSI and infection prevalence in study sites of Côte d’Ivoire. Conclusions/Significance A predictive map of environmental suitability for schistosomiasis transmission can support measures to gain and sustain control. This is particularly relevant as emphasis is shifting from morbidity control to interrupting transmission. Further validation of our mechanistic model needs to be complemented by field data of parasite- and snail-related fitness. Our model provides a useful tool to monitor the development of new hotspots of potential schistosomiasis transmission based on regularly updated remote sensing data. PMID:26587839

Modeling and Validation of Environmental Suitability for Schistosomiasis Transmission Using Remote Sensing.

PubMed

Walz, Yvonne; Wegmann, Martin; Dech, Stefan; Vounatsou, Penelope; Poda, Jean-Noël; N'Goran, Eliézer K; Utzinger, Jürg; Raso, Giovanna

2015-11-01

Schistosomiasis is the most widespread water-based disease in sub-Saharan Africa. Transmission is governed by the spatial distribution of specific freshwater snails that act as intermediate hosts and human water contact patterns. Remote sensing data have been utilized for spatially explicit risk profiling of schistosomiasis. We investigated the potential of remote sensing to characterize habitat conditions of parasite and intermediate host snails and discuss the relevance for public health. We employed high-resolution remote sensing data, environmental field measurements, and ecological data to model environmental suitability for schistosomiasis-related parasite and snail species. The model was developed for Burkina Faso using a habitat suitability index (HSI). The plausibility of remote sensing habitat variables was validated using field measurements. The established model was transferred to different ecological settings in Côte d'Ivoire and validated against readily available survey data from school-aged children. Environmental suitability for schistosomiasis transmission was spatially delineated and quantified by seven habitat variables derived from remote sensing data. The strengths and weaknesses highlighted by the plausibility analysis showed that temporal dynamic water and vegetation measures were particularly useful to model parasite and snail habitat suitability, whereas the measurement of water surface temperature and topographic variables did not perform appropriately. The transferability of the model showed significant relations between the HSI and infection prevalence in study sites of Côte d'Ivoire. A predictive map of environmental suitability for schistosomiasis transmission can support measures to gain and sustain control. This is particularly relevant as emphasis is shifting from morbidity control to interrupting transmission. Further validation of our mechanistic model needs to be complemented by field data of parasite- and snail-related fitness. Our model provides a useful tool to monitor the development of new hotspots of potential schistosomiasis transmission based on regularly updated remote sensing data.

Detection of Galba truncatula, Fasciola hepatica and Calicophoron daubneyi environmental DNA within water sources on pasture land, a future tool for fluke control?

PubMed

Jones, Rhys Aled; Brophy, Peter M; Davis, Chelsea N; Davies, Teri E; Emberson, Holly; Rees Stevens, Pauline; Williams, Hefin Wyn

2018-06-08

Increasing trematode prevalence and disease occurrence in livestock is a major concern. With the global spread of anthelmintic resistant trematodes, future control strategies must incorporate approaches focusing on avoidance of infection. The reliance of trematodes on intermediate snail hosts to successfully complete their life-cycle means livestock infections are linked to the availability of respective snail populations. By identifying intermediate snail host habitats, infection risk models may be strengthened whilst farmers may confidently apply pasture management strategies to disrupt the trematode life-cycle. However, accurately identifying and mapping these risk areas is challenging. In this study, environmental DNA (eDNA) assays were designed to reveal Galba truncatula, Fasciola hepatica and Calicophoron daubneyi presence within water sources on pasture land. eDNA was captured using a filter-based protocol, with DNA extracted using the DNeasy® PowerSoil® kit and amplified via PCR. In total, 19 potential G. truncatula habitats were analysed on four farms grazed by livestock infected with both F. hepatica and C. daubneyi. Galba truncatula eDNA was identified in 10/10 habitats where the snail was detected by eye. Galba truncatula eDNA was also identified in four further habitats where the snail was not physically detected. Fasciola hepatica and C. daubneyi eDNA was also identified in 5/19 and 8/19 habitats, respectively. This study demonstrated that eDNA assays have the capabilities of detecting G. truncatula, F. hepatica and C. daubneyi DNA in the environment. Further assay development will be required for a field test capable of identifying and quantifying F. hepatica and C. daubneyi infection risk areas, to support future control strategies. An eDNA test would also be a powerful new tool for epidemiological investigations of parasite infections on farms.

Patterns of parasite transmission in polar seas: Daily rhythms of cercarial emergence from intertidal snails

NASA Astrophysics Data System (ADS)

Prokofiev, Vladimir V.; Galaktionov, Kirill V.; Levakin, Ivan A.

2016-07-01

Trematodes are common parasites in intertidal ecosystems. Cercariae, their dispersive larvae, ensure transmission of infection from the first intermediate molluscan host to the second intermediate (invertebrates and fishes) or the final (fishes, marine birds and mammals) host. Trematode transmission in polar seas, while interesting in many respects, is poorly studied. This study aimed to elucidate the patterns of cercarial emergence from intertidal snails at the White Sea and Barents Sea. The study, involving cercariae of 12 species, has provided the most extensive material obtained so far in high latitude seas (66-69° N). The experiments were conducted in situ. Multichannel singular spectral analysis (MSSA) used for processing primary data made it possible to estimate the relative contribution of different oscillations into the analysed time series and to separate the daily component from the other oscillatory components and the noise. Cercarial emergence had pronounced daily rhythms, which did not depend on the daily tidal schedule but were regulated by thermo- and photoperiod. Daily emergence maximums coincided with periods favourable for infecting the second intermediate hosts. Cercarial daily emergence rhythms differed in species using the same molluscan hosts which can be explained by cercarial host searching behaviour. Daily cercarial output (DCO) correlated negatively with larval volume and positively with that of the molluscan host except in cercariae using ambuscade behaviour. In the Barents Sea cercariae emerged from their molluscan hosts at lower temperatures than in the warmer White Sea but the daily emergence period was prolonged. Thus, DCO of related species were similar in these two seas and comparable with DCO values reported for boreal seas. Local temperature adaptations in cercarial emergence suggests that in case of Arctic climate warming trematode transmission in coastal ecosystems is likely to be intensified not because of the increased summer temperature but because of the prolongation of the warm season favouring cercarial emergence (transmission window).

Use of Molecular Methods for the Rapid Mass Detection of Schistosoma mansoni (Platyhelminthes: Trematoda) in Biomphalaria spp. (Gastropoda: Planorbidae)

PubMed Central

Jannotti-Passos, Liana Konovaloffi; Dos Santos Carvalho, Omar

2017-01-01

The low stringency-polymerase chain reaction (LS-PCR) and loop-mediated isothermal amplification (LAMP) assays were used to detect the presence of S. mansoni DNA in (1) Brazilian intermediate hosts (Biomphalaria glabrata, B. straminea, and B. tenagophila) with patent S. mansoni infections, (2) B. glabrata snails with prepatent S. mansoni infections, (3) various mixtures of infected and noninfected snails; and (4) snails infected with other trematode species. The assays showed high sensitivity and specificity and could detect S. mansoni DNA when one positive snail was included in a pool of 1,000 negative specimens of Biomphalaria. These molecular approaches can provide a low-cost, effective, and rapid method for detecting the presence of S. mansoni in pooled samples of field-collected Biomphalaria. These assays should aid mapping of transmission sites in endemic areas, especially in low prevalence regions and improve schistosomiasis surveillance. It will be a useful tool to monitor low infection rates of snails in areas where control interventions are leading towards the elimination of schistosomiasis. PMID:28246533

Anserobilharzia gen. n. (Digenea, Schistosomatidae) and redescription of A. brantae (Farr & Blankemeyer, 1956) comb. n. (syn. Trichobilharzia brantae), a parasite of geese (Anseriformes).

PubMed

Brant, Sara V; Jouet, Damien; Ferte, Hubert; Loker, Eric S

2013-01-01

A new genus, Anserobilharzia, is proposed to accommodate Anserobilharzia brantae n. comb. (syn. Trichobilharzia bran- tae Farr & Blankemeyer, 1956), a species of avian schistosome thus far found exclusively in anserini geese (Anser, Branta, Chen) from Europe and North America, and Gyraulus snails. Recent collections and subsequent molecular analyses showed that A. brantae was distinct from Allobilharzia and Trichobilharzia and grouped basal to Trichobilharzia. Using nuclear 28S, ITS and mitochondrial cox1 as genetic yardsticks, samples of A. brantae from North America and Europe were each other's closest relative and distinct from Allobilharzia and Trichobilharzia. Anserobilharzia brantae was also distinct when compared morphologically with other species of closely related avian schistosomes. The following descrip- tion is based on males, females, eggs, and cercariae. The new genus is characterized by a) ovoid egg (72-145µm x 44- 89 µm) with spine, b) male with > 500 testes and caecal reunion anteriad to seminal vesicle, c) cercariae with 5+1 flame cells, and d) intermediate hosts are planorbid snails. The only confirmed species of snail host is Gyraulus parvus in North America. Based on presented data, we propose a new genus and new combination for A. brantae justified by morpholog- ical, host use, and molecular characteristics.

Schistosoma mansoni miracidia transformed by particle bombardment infect Biomphalaria glabrata snails and develop into transgenic sporocysts.

PubMed

Heyers, Oliver; Walduck, Anna K; Brindley, Paul J; Bleiss, Wilfrid; Lucius, Richard; Dorbic, Tomislav; Wittig, Burghardt; Kalinna, Bernd H

2003-10-01

Miracidia (and adults) of Schistosoma mansoni which had been subjected to particle bombardment with a plasmid DNA encoding enhanced green fluorescent protein (EGFP) under control of the S. mansoni heat shock protein 70 (HSP70) promoter and termination elements were shown to express the reporter gene. Bombarded miracidia were able to penetrate and establish in Biomphalaria glabrata the intermediate host snail. Gold particles could be detected in the germ balls of parasites in paraffin-sections of snail tissue. The bombarded miracidia were able to develop normally and to transform into mother sporocysts. Reporter gene activity could be determined at 10 days post-infection by RT-PCR in snail tissues, but not by microscopy or Western blot which probably reflected sub-optimal expression levels of constructs. Our findings indicated that it is feasible to return transgenic miracidia to the life cycle, a crucial step for the establishment of a transgenesis system for schistosomes.

Apropos: critical analysis of molluscicide application in schistosomiasis control programs in Brazil.

PubMed

Li, Hongjun; Wang, Wei

2017-03-07

Schistosomiasis is a snail-transmitted infectious disease affecting over 200 million people worldwide. Snail control has been recognized as an effective approach to interrupt the transmission of schistosomiasis, since the geographic distribution of this neglected tropical disease is determined by the presence of the intermediate host snails. In a recent Scoping Review published in Infectious Diseases of Poverty, Coelho and Caldeira performed a critical review of using molluscicides in the national schistosomiasis control programs in Brazil. They also described some chemical and plant-derived molluscicides used in China. In addition to the molluscicides described by Coelho and Caldeira, a large number of chemicals, plant extracts and microorganisms have been screened and tested for molluscicidal actions against Oncomelania hupensis, the intermediate host of Schistosoma japonicum in China. Here, we presented the currently commercial molluscicides available in China, including 26% suspension concentrate of metaldehyde and niclosamide (MNSC), 25% suspension concentrate of niclosamide ethanolamine salt (SCNE), 50% niclosamide ethanolamine salt wettable powder (WPN), 4% niclosamide ethanolamine salt dustable powder (NESP), 5% niclosamide ethanolamine salt granule (NESG) and the plant-derived molluscicide "Luowei". These molluscicides have been proved to be active against O. hupensis in both laboratory and endemic fields, playing an important role in the national schistosomiasis control program of China. Currently, China is transferring its successful experiences on schistosomiasis control to African countries. The introduction of Chinese commercial molluscicides to Africa, with adaptation to local conditions, may facilitate the progress towards the elimination of schisosomiasis in Africa.

Localization of Tyrosine Hydroxylase-like Immunoreactivity in the Nervous Systems of Biomphalaria glabrata and Biomphalaria alexandrina, Intermediate Hosts for Schistosomiasis

PubMed Central

Vallejo, Deborah; Habib, Mohammed R.; Delgado, Nadia; Vaasjo, Lee O.; Croll, Roger P.; Miller, Mark W.

2014-01-01

Planorbid snails of the genus Biomphalaria are major intermediate hosts for the digenetic trematode parasite Schistosoma mansoni. Evidence suggests that levels of the neurotransmitter dopamine (DA) are reduced during the course of S. mansoni multiplication and transformation within the snail. This investigation used immunohistochemical methods to localize tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of catecholamines, in the nervous system of Biomphalaria. The two species examined, Biomphalaria glabrata and Biomphalaria alexandrina, are the major intermediate hosts for S. mansoni in sub-Saharan Africa, where more than 90% of global cases of human intestinal schistosomiasis occur. TH-like immunoreactive (THli) neurons were distributed throughout the central nervous system (CNS) and labeled fibers were present in all commissures, connectives, and nerves. Some asymmetries were observed, including a large distinctive neuron (LPeD1) in the pedal ganglion described previously in several pulmonates. The majority of TH-like immunoreactive neurons were detected in the peripheral nervous system (PNS), especially in lip and foot regions of the anterior integument. Independent observations supporting the dopaminergic phenotype of THli neurons included 1) block of LPeD1 synaptic signaling by the D2/3 antagonist sulpiride, and 2) the similar localization of aqueous aldehyde (FaGlu) induced fluorescence. The distribution of THli neurons indicates that, as in other gastropods, dopamine functions as a sensory neurotransmitter and in the regulation of feeding and reproductive behaviors in Biomphalaria. It is hypothesized that infection could stimulate transmitter release from dopaminergic sensory neurons and that dopaminergic signaling could contribute to modifications of both host and parasite behavior. PMID:24477836

Three Gorges Dam: polynomial regression modeling of water level and the density of schistosome-transmitting snails Oncomelania hupensis.

PubMed

Yang, Ya; Gao, Jianchuan; Cheng, Wanting; Pan, Xiang; Yang, Yu; Chen, Yue; Dai, Qingqing; Zhu, Lan; Zhou, Yibiao; Jiang, Qingwu

2018-03-14

Schistosomiasis remains a major public health concern in China. Oncomelania hupensis (O. hupensis) is the sole intermediate host of Schistosoma japonicum, and its change in distribution and density influences the endemic S. japonicum. The Three Gorges Dam (TGD) has substantially changed the downstream water levels of the dam. This study investigated the quantitative relationship between flooding duration and the density of the snail population. Two bottomlands without any control measures for snails were selected in Yueyang City, Hunan Province. Data for the density of the snail population and water level in both spring and autumn were collected for the period 2009-2015. Polynomial regression analysis was applied to explore the relationship between flooding duration and the density of the snail population. Data showed a convex relationship between spring snail density and flooding duration of the previous year (adjusted R 2 , aR 2  = 0.61). The spring snail density remained low when the flooding duration was fewer than 50 days in the previous year, was the highest when the flooding duration was 123 days, and decreased thereafter. There was a similar convex relationship between autumn snail density and flooding duration of the current year (aR 2  = 0.77). The snail density was low when the flooding duration was fewer than 50 days and was the highest when the flooding duration was 139 days. There was a convex relationship between flooding duration and the spring or autumn snail density. The snail density was the highest when flooding lasted about four to 5 months.

EFFECTS OF NUTRIENT AND PESTICIDE LOADING ON AQUATIC ECOSYSTEMS AS PERTAINING TO THE EMERGENCE AND TRANSMISSION OF HUMAN DISEASE: THE CASE OF “SWIMMERS’ ITCH”

EPA Science Inventory

It is expected that nutrient additions (nitrogen and phosphorus in the form of fertilizers, sewage effluent, etc.) boost both food quantity and food quality for aquatic snails (the intermediate hosts for cercarial dermatitis). As a result, these grazers will be more competent ...

Global Assessment of Schistosomiasis Control Over the Past Century Shows Targeting the Snail Intermediate Host Works Best

PubMed Central

Sokolow, Susanne H.; Wood, Chelsea L.; Jones, Isabel J.; Lopez, Melina; Lafferty, Kevin D.; Kuris, Armand M.; Rickards, Chloe; De Leo, Giulio A.

2016-01-01

Background Despite control efforts, human schistosomiasis remains prevalent throughout Africa, Asia, and South America. The global schistosomiasis burden has changed little since the new anthelmintic drug, praziquantel, promised widespread control. Methodology We evaluated large-scale schistosomiasis control attempts over the past century and across the globe by identifying factors that predict control program success: snail control (e.g., molluscicides or biological control), mass drug administrations (MDA) with praziquantel, or a combined strategy using both. For data, we compiled historical information on control tactics and their quantitative outcomes for all 83 countries and territories in which: (i) schistosomiasis was allegedly endemic during the 20th century, and (ii) schistosomiasis remains endemic, or (iii) schistosomiasis has been "eliminated," or is "no longer endemic," or transmission has been interrupted. Principal Findings Widespread snail control reduced prevalence by 92 ± 5% (N = 19) vs. 37 ± 7% (N = 29) for programs using little or no snail control. In addition, ecological, economic, and political factors contributed to schistosomiasis elimination. For instance, snail control was most common and widespread in wealthier countries and when control began earlier in the 20th century. Conclusions/Significance Snail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis. PMID:27441556

Global Assessment of Schistosomiasis Control Over the Past Century Shows Targeting the Snail Intermediate Host Works Best.

PubMed

Sokolow, Susanne H; Wood, Chelsea L; Jones, Isabel J; Swartz, Scott J; Lopez, Melina; Hsieh, Michael H; Lafferty, Kevin D; Kuris, Armand M; Rickards, Chloe; De Leo, Giulio A

2016-07-01

Despite control efforts, human schistosomiasis remains prevalent throughout Africa, Asia, and South America. The global schistosomiasis burden has changed little since the new anthelmintic drug, praziquantel, promised widespread control. We evaluated large-scale schistosomiasis control attempts over the past century and across the globe by identifying factors that predict control program success: snail control (e.g., molluscicides or biological control), mass drug administrations (MDA) with praziquantel, or a combined strategy using both. For data, we compiled historical information on control tactics and their quantitative outcomes for all 83 countries and territories in which: (i) schistosomiasis was allegedly endemic during the 20th century, and (ii) schistosomiasis remains endemic, or (iii) schistosomiasis has been "eliminated," or is "no longer endemic," or transmission has been interrupted. Widespread snail control reduced prevalence by 92 ± 5% (N = 19) vs. 37 ± 7% (N = 29) for programs using little or no snail control. In addition, ecological, economic, and political factors contributed to schistosomiasis elimination. For instance, snail control was most common and widespread in wealthier countries and when control began earlier in the 20th century. Snail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis.

Schistosomiasis

PubMed Central

Tucker, Matthew S.; Karunaratne, Laksiri B.; Lewis, Fred A.; Freitas, Tori C.; Liang, Yung-san

2014-01-01

Schistosomiasis is the second most important parasitic disease in the world in terms of public health impact. Globally, it is estimated that the disease affects over 200 million people and is responsible for 200,000 deaths each year. The three major schistosomes infecting humans are Schistosoma mansoni, S. japonicum, and S. haematobium. Much immunological research has focused on schistosomiasis because of the pathological effects of the disease, which include liver fibrosis and bladder dysfunction. This Unit covers a wide range of aspects of maintaining the life cycles of these parasites, including preparation of schistosome egg antigen, maintenance of intermediate snail hosts, infection of the definitive and intermediate hosts, and others. The Unit primariiy focues on S. mansoni, but also includes coverage of S. japonicum and S. haematobium life cycles. PMID:18432750

Ecology of larval trematodes in three marine gastropods.

PubMed

Curtis, Lawrence A

2002-01-01

To comprehend natural host-parasite systems, ecological knowledge of both hosts and parasites is critical. Here I present a view of marine systems based on the snail Ilyanassa obsoleta and its trematodes. This system is reviewed and two others, those of the snails Cerithidea californica and Littorina littorea, are then summarized and compared. Trematodes can profoundly affect the physiology, behaviour and spatial distribution of hosts. Studying these systems is challenging because trematodes are often embedded in host populations in unappreciated ways. Trematode prevalence is variable, but can be high in populations of all three hosts. Conditions under which single- and multiple-species infections can accumulate are considered. Adaptive relations between species are likely the most important and potentials for adaptation of parasites to hosts, hosts to parasites, and parasites to other parasites are also considered. Even if colonization rate is low, a snail population can develop high trematode prevalence, if infections persist long and the host is long-lived and abundant. Trematodes must be adapted to use their snail hosts. However, both I. obsoleta and L. littorea possess highly dispersed planktonic larvae and trematode prevalence is variable among snail populations. Host adaptation to specific infections, or even to trematodes in general, is unlikely because routine exposure to trematodes is improbable. Crawl-away juveniles of C. californica make adaptation to trematodes in that system a possibility. Trematode species in all three systems are not likely adapted to each other. Multiple-species infections are rare and definitive hosts scatter parasite eggs among snail populations with variable prevalences. Routine co-occurrence of trematodes in snails is thus unlikely. Adaptations of these larval trematodes to inhabit the snail host must, then, be the basis for what happens when they do co-occur.

Study 8: Prevalence and load of Nanophyetus salmincola infection in outmigrating steelhead trout from five Puget Sound rivers

USGS Publications Warehouse

Chen, M.F.; Stewart, B.A.; Senkvik, Kevin; Hershberger, Paul

2015-01-01

Nanophyetus salmincola is a parasitic trematode, or flatworm, that infects salmonid fishes in the Pacific Northwest, including Washington, Oregon, and portions of California. The adult worm lives in the intestine of fish-eating birds and mammals. Eggs shed into the water hatch into miracidia which penetrate the first intermediate host, one of two species of snail Juga plicifera or J. silicula. Asexual reproduction occurs within the snail. Free-swimming cercaria are released from the snail and penetrate the secondary intermediate host, often a salmonid fish, in fresh and brackish water. The cercaria encyst as metacercaria in various organs of the fish, including gills, muscle and heart, but favor the posterior kidney. Penetration and migration by the cercaria through the fish causes damage to nearly every organ system. Once encysted, metacercaria survive the ocean phase of salmonid life cycle. N. salmincola is a likely contributor to mortality of juvenile coho salmon (Oncorhynchus kisutch) during the early ocean rearing phase, and it is the most prevalent pathogen of outmigrating steelhead in the estuaries of the Pacific Northwest.A field survey was implemented from March-June 2014 to compare the prevalence and parasite load of N. salmincola infections in outmigrating steelhead from five Puget Sound watersheds and to assess changes in infection levels that occurred during the smolt out-migration through each watershed. N. salmincola infection prevalence and parasite loads were determined by counting metacercaria in posterior kidney samples. Tissue samples were collected and examined by standard histological methods.

Control Measures for Slug and Snail Hosts of Angiostrongylus cantonensis, with Special Reference to the Semi-slug Parmarion martensi

PubMed Central

Howe, Kathleen; Jarvi, Susan I

2013-01-01

Slugs and snails (class Gastropoda) are the obligate intermediate hosts of the rat lungworm, Angiostrongylus cantonensis. This nematode is the causative agent of human angiostrongyliasis and the most common cause of human eosinophilic meningoencephalitis. Humans can become infected by accidental consumption of slugs or snails and possibly flatworms (or a portion of one of these animals) in fresh produce, but the slime from these animals can contain nematodes and may also constitute a disease risk. Gastropod carriers in Hawai‘i include, among other species, giant African snails, veronicellid slugs, and the semi-slug Parmarion martensi. This latter species was first discovered on the island of Hawai‘i in 2004 and is now common in the area where the majority of the state's documented cases of human angiostrongyliasis occurred between 2005 and 2011. This species is considered a high risk carrier of A. cantonensis because of its climbing behavior, abundance around human dwellings, and high worm burdens. One individual collected from east Hawai‘i Island contained >6,800 infective third stage A. cantonensis larvae. Common and efficient control methods for slugs and snails include sanitation (eg, removal of objects that serve as hiding places) and the use of poison food baits, such as those containing metaldehyde and iron. An iron-containing bait that is relatively safe to non-target organisms was effective in controlling semi-slugs in cage experiments, although it killed more slowly than a metaldehyde-containing bait and the majority of slugs affected did not die until 1–2 weeks following ingestion. PMID:23901389

Epidemiology of intestinal helminthiasis among school children with emphasis on Schistosoma mansoni infection in Wolaita zone, Southern Ethiopia.

PubMed

Alemayehu, Bereket; Tomass, Zewdneh; Wadilo, Fiseha; Leja, Dawit; Liang, Song; Erko, Berhanu

2017-06-20

Intestinal helminth infections are major parasitic diseases causing public health problems in Ethiopia. Although the epidemiology of these infections are well documented in Ethiopia, new transmission foci for schistosomiasis are being reported in different parts of the country. The objective of this study was to assess the prevalence of Schistosoma mansoni and other intestinal helminth infections among school children and determine the endemicity of schistosomiasis in Wolaita Zone, southern Ethiopia. Cross-sectional parasitological and malacological surveys were conducted by collecting stool samples for microscopic examination and snails for intermediate host identification. Stool samples were collected from 503 children and processed for microscopic examination using Kato-Katz and formalin-ether concentration methods. Snails collected from aquatic environments in the study area were identified to species level and Biomphalaria pfeifferi snails, the intermediate host of S. mansoni,, were individually exposed to artificial light in order to induce cercariae shedding. Cercariae shed from snails were used to infect laboratory-bred Swiss albino mice in order to identify the schistosome to species level. The overall prevalence of intestinal helminth infections was 72.2% among school children. S. mansoni infection prevalence was 58.6%. The prevalence and intensity of S. mansoni infections varied among schools and sex of children. Swimming was the only factor reported to be significantly associated with S. mansoni infection (AOR = 2.954, 95% CI:1.962-4.449). Other intestinal helminth species identified were hookworms (27.6%), Ascaris lumbricoides (8.7%), E. vermicularis (2.8%), Taenia species (2.6%), T. trichiura (1.2%) and H. nana (0.6%). Only B. pfeifferi snails collected from streams shed schistosome cercariae and 792 adult S. mansoni worms were harvested from mice exposed to cercariae shed from B. pfeifferi on the 6th week post-exposure. The present study found high level of intestinal helminth infections in the study area. The study also confirmed autochthonous transmission and endemicity of S. mansoni as evidenced by both parasitological and malacological findings as well as by further establishing infections in lab-bred mice. Therefore, there is a need to include the area in the control programs with anti-helminth drugs and also consider other complementary measures including sanitation, provision of clean water supply, and snail control.

[Reexamination of the life cycle of Isthmiophora melis (Trematoda: Echinostomatidae) on material from southeast Europe].

PubMed

Radev, V; Kanev, I; Khrusanov, D; Fried, B

2009-01-01

The life cycle of Isthmiophora melis (Schrank, 1788) on material from Southeast Europe was experimentally reexamined. Thirteen names or combinations can be accepted as true synonyms of I. melis: Distoma melis (Schrank, 1788) Zeder, 1800; Echinocirrus melis (Schrank, 1788) Mendhaim, 1943; Isthmiophora spiculator (Dujardin, 1845); Echinostoma trigonocephalum (Rud., 1802) Cobbold, 1861; E. melis (Schrank, 1788) Dietz, 1909; E. spiculator Dujardin, 1845; Euparyphium jassyense Leon and Ciurea, 1922; E. melis (Schrank, 1788) Railliet, 1919; E. suinum Ciurea, 1921; Fasciola armata Rud., 1802; F. melis Schrank, 1788; F. putorii Gmelin, 1791; F. trigonocephala Rud., 1802. The first intermediate hosts are the pulmonate freshwater snail Lymnaea stagnalis. The second intermediate hosts are many amphibians and freshwater fishes. The list of definitive hosts includes more than 30 species of vertebrates including humans. I. melis occurs in Europe, Asia and North America.

Physiological changes in Lymnaea columella (Say, 1817) (Mollusca, Gastropoda) in response to Echinostoma paraensei Lie and Basch, 1967 (Trematoda: Echinostomatidae) infection.

PubMed

Pinheiro, J; Maldonado Júnior, A; Lanfredi, R M

2009-12-01

The physiological interaction between the digenean Echinostoma paraensei larvae and the intermediate snail host Lymnaea columella was studied. The carbohydrate content was significantly altered in the digestive gland tissue of snails, decreasing after 20 days postinfection. At the end of the prepatent period, the carbohydrate content was reduced by 60% when compared to uninfected snails. The total protein was reduced by 80.01% and 76.42% in the hemolymph and digestive gland, respectively. The end products resulting from nitrogen degradation were also analyzed. The urea was significantly increased in both the hemolymph and digestive gland. In the former, the highest concentration was detected at day 10 postinfection and then decreased until the end of the prepatent period. In digestive glands from infected snails, urea was significantly higher than in uninfected ones after 20 days. The uric acid content was reduced by 94.72% in the hemolymph and 43.75% in digestive glands after 10 days postinfection. The ammonia was undetectable under the experimental conditions employed.

Spatial and temporal relationships between the invasive snail Bithynia tentaculata and submersed aquatic vegetation in Pool 8 of the Upper Mississippi River

USGS Publications Warehouse

Weeks, Alicia M.; DeJager, Nathan R.; Haro, Roger J.; Sandland, Greg J.

2017-01-01

Bithynia tentaculata is an invasive snail that was first reported in Lake Michigan in 1871 and has since spread throughout a number of freshwater systems of the USA. This invasion has been extremely problematic in the Upper Mississippi River as the snails serve as intermediate hosts for several trematode parasites that have been associated with waterfowl mortality in the region. This study was designed to assess the abundance and distribution of B. tentaculata relative to submersed aquatic vegetation as macrophytes provide important nesting and food resources for migrating waterfowl. Temporal changes in both vegetation and snail densities were compared between 2007 and 2015. Between these years, B. tentaculata densities have nearly quadrupled despite minor changes in vegetation abundance, distribution and composition. Understanding the spatial distribution of B. tentaculata in relation to other habitat features, including submersed vegetation, and quantifying any further changes in the abundance and distribution of B. tentaculata over time will be important for better identifying areas of risk for disease transmission to waterfowl.

Exploring molecular variation in Schistosoma japonicum in China.

PubMed

Young, Neil D; Chan, Kok-Gan; Korhonen, Pasi K; Min Chong, Teik; Ee, Robson; Mohandas, Namitha; Koehler, Anson V; Lim, Yan-Lue; Hofmann, Andreas; Jex, Aaron R; Qian, Baozhen; Chilton, Neil B; Gobert, Geoffrey N; McManus, Donald P; Tan, Patrick; Webster, Bonnie L; Rollinson, David; Gasser, Robin B

2015-12-01

Schistosomiasis is a neglected tropical disease that affects more than 200 million people worldwide. The main disease-causing agents, Schistosoma japonicum, S. mansoni and S. haematobium, are blood flukes that have complex life cycles involving a snail intermediate host. In Asia, S. japonicum causes hepatointestinal disease (schistosomiasis japonica) and is challenging to control due to a broad distribution of its snail hosts and range of animal reservoir hosts. In China, extensive efforts have been underway to control this parasite, but genetic variability in S. japonicum populations could represent an obstacle to eliminating schistosomiasis japonica. Although a draft genome sequence is available for S. japonicum, there has been no previous study of molecular variation in this parasite on a genome-wide scale. In this study, we conducted the first deep genomic exploration of seven S. japonicum populations from mainland China, constructed phylogenies using mitochondrial and nuclear genomic data sets, and established considerable variation between some of the populations in genes inferred to be linked to key cellular processes and/or pathogen-host interactions. Based on the findings from this study, we propose that verifying intraspecific conservation in vaccine or drug target candidates is an important first step toward developing effective vaccines and chemotherapies against schistosomiasis.

Are sick individuals weak competitors? Competitive ability of snails parasitized by a gigantism-inducing trematode.

PubMed

Seppälä, Otto; Karvonen, Anssi; Kuosa, Marja; Haataja, Maarit; Jokela, Jukka

2013-01-01

Parasitized individuals are often expected to be poor competitors because they are weakened by infections. Many trematode species, however, although extensively exploiting their mollusc hosts, also induce gigantism (increased host size) by diverting host resources towards growth instead of reproduction. In such systems, alternatively to reduced competitive ability due to negative effects of parasitism on host performance, larger size could allow more efficient resource acquisition and thus increase the relative competitive ability of host individuals. We addressed this hypothesis by testing the effect of a trematode parasite Diplostomum pseudospathaceum on the competitive ability of its snail host Lymnaea stagnalis. We experimentally examined the growth of snails kept in pairs in relation to their infection status and intensity of resource competition (i.e. food availability). We found that parasitized snails grew faster and their reproduction was reduced compared to unparasitized individuals indicating parasite-induced gigantism. However, growth of the snails was faster when competing with parasitized individuals compared to unparasitized snails indicating reduced competitive ability due to parasitism. The latter effect, however, was relatively weak suggesting that the effects of the parasite on snail physiology may partly override each other in determining competitive ability.

Are Sick Individuals Weak Competitors? Competitive Ability of Snails Parasitized by a Gigantism-Inducing Trematode

PubMed Central

Seppälä, Otto; Karvonen, Anssi; Kuosa, Marja; Haataja, Maarit; Jokela, Jukka

2013-01-01

Parasitized individuals are often expected to be poor competitors because they are weakened by infections. Many trematode species, however, although extensively exploiting their mollusc hosts, also induce gigantism (increased host size) by diverting host resources towards growth instead of reproduction. In such systems, alternatively to reduced competitive ability due to negative effects of parasitism on host performance, larger size could allow more efficient resource acquisition and thus increase the relative competitive ability of host individuals. We addressed this hypothesis by testing the effect of a trematode parasite Diplostomum pseudospathaceum on the competitive ability of its snail host Lymnaea stagnalis. We experimentally examined the growth of snails kept in pairs in relation to their infection status and intensity of resource competition (i.e. food availability). We found that parasitized snails grew faster and their reproduction was reduced compared to unparasitized individuals indicating parasite-induced gigantism. However, growth of the snails was faster when competing with parasitized individuals compared to unparasitized snails indicating reduced competitive ability due to parasitism. The latter effect, however, was relatively weak suggesting that the effects of the parasite on snail physiology may partly override each other in determining competitive ability. PMID:24205383

Molecular characterization of cryptic and sympatric lymnaeid species from the Galba/Fossaria group in Mendoza Province, Northern Patagonia, Argentina

PubMed Central

2013-01-01

Background Freshwater lymnaeid snails can act as the intermediate hosts for trematode parasites such as the liver fluke Fasciola hepatica, that cause significant economic and biomedical burden worldwide, particularly through bovine fascioliasis. Transmission potential is tightly coupled to local compatibility with snail hosts, so accurate identification of lymnaeid species is crucial for understanding disease risk, especially when invasive species are encountered. Mendoza Province, in Argentina, is a center of livestock production and also an area of endemic fascioliasis transmission. However, the distribution of lymnaeid species in the region is not well known. Methods This study examined lymnaeid snails from seven localities in the Department of Malarguë, Mendoza Province, using morphological and molecular analyses and also describing ecological variables associated with snail presence. Results While morphological characters identified two species of lymnaeid, Galba truncatula and G. viatrix, molecular data revealed a third, cryptic species, G. neotropica, which was sympatric with G. viatrix. G. truncatula was exclusively found in high altitude (>1900 meters above sea level [masl]) sites, whereas mixed G. neotropica/G. viatrix localities were at middle elevations (1300–1900 masl), and G. viatrix was found alone at the lowest altitude sites (<1300 masl). Phylogenetic analysis using two mitochondrial markers revealed G. neotropica and G. viatrix to be closely related, and given their morphological similarities, their validities as separate taxonomic entities should be questioned. Conclusions This study highlights the need of a robust taxonomic framework for the identification of lymnaeid snails, incorporating molecular, morphological and ecological variables while avoiding nomenclature redundancy. As the three species observed here, including one alien invasive species, are considered hosts of varying susceptibility to Fasciola parasites, and given the economic importance of fascioliasis for livestock production, this research has critical importance for the ultimate aim of controlling disease transmission. PMID:24499569

Review of the trematode genus Ribeiroia (Psilostomidae): ecology, life history and pathogenesis with special emphasis on the amphibian malformation problem.

PubMed

Johnson, Pieter T J; Sutherland, Daniel R; Kinsella, J M; Lunde, Kevin B

2004-01-01

Trematodes in the genus Ribeiroia have an indirect life cycle involving planorbid snails as first intermediate hosts, fishes or amphibians as second intermediate hosts and birds or mammals as definitive hosts. Although rarely pathogenic in definitive hosts, Ribeiroia infection can cause severe pathology and mortality in snails and amphibians. This group of parasites has gained notoriety for its prominent rol in the recent rash of amphibian deformities in North America. Under some circumstances, these malformations may enhance parasite transmission by rendering infected amphibian hosts more susceptible to definitive host predators. However, increasing reports of malformations in North American amphibian populations emphasize the importance of understanding infection patterns. Here we review important aspects of the biology, ecology, life cycle and pathogenesis of parasites in the genus Ribeiroia and identify priorities for future research. Based on available morphological descriptions and preliminary molecular data, three species of Ribeiroia are recognized: R. ondatrae in the Americas, R. marini in the Caribbean and R. congolensis/C. lileta in Africa. We further evaluate the influence of abiotic and biotic factors in determining the intensity and prevalence of Ribeiroia infection and malformations in amphibians, highlighting the importance of habitat alteration and secondary factors (e.g. aquatic eutrophication, contaminants) in promoting infection. Although not a "new" parasite, Ribeiroia may have increased in range, prevalence, or intensity in recent years, particularly within amphibian hosts. Nevertheless, while much is known about this intriguing group of parasites, there remains much that we do not know. Particular importance for future research is placed on the following areas: evaluating the phylogenetic position of the genus, establishing the molecular mechanism of parasite-induced malformations in amphibians, isolating the drivers of parasite transmission under field conditions and studying the consequences of malformations for parasite and host populations. Investigation of these questions will benefit enormously from a multidisciplinary approach that effectively integrates parasitology, developmental biology, immunology, herpetology and aquatic ecology.

Toxicity of anti-fouling biocides to encysted metacercariae of Echinoparyphium recurvatum (Digenea: Echinostomatidae) and their snail hosts.

PubMed

Morley, N J; Leung, K M Y; Morritt, D; Crane, M

2004-07-01

The toxicity of the anti-fouling biocides tributyltin (TBTO), copper, and Irgarol 1051 (irgarol) at a nominal concentration of 10 microg/l over a 30 day period were investigated against the viability of metacercarial cysts of the digenean parasite Echinoparyphium recurvatum resident within the body of two common freshwater snails, Lymnaea peregra and Physa fontinalis. Reduced parasite viability was found under most exposures in both snail species. However a greater effect of toxicant exposure was found in cysts within P. fontinalis compared to those in L. peregra. This was associated with an increased mortality of the host snail. Among all tested biocides, TBTO exposures induced the highest mortality to both the parasite and their hosts. These results suggest that parasite viability is interlinked with survival of the host snail. The mechanisms of differing toxicity between host species and its relevance to successful parasite transmission to the next host are discussed.

Eating habits associated with Echinostoma malayanum infections in the Philippines.

PubMed

Tangtrongchitr, A; Monzon, R B

1991-12-01

A survey of 61 residents belonging to 12 pre-selected families (having at least one member positive for echinostomiasis malayanum) from Barangay Malibago, Echague, Isabela (northern Luzon) suggested that infections with Echinostoma malayanum follow a "familial trend". The parasite is endemic because the raw ingestion of Lymnaea (Bullastra) cumingiana, the second intermediate host in the Philippines, is a learned habit passed down from one generation to the next. A questionnaire on eating habits revealed that Lymnaea (Bullastra) cumingiana or "birabid" was usually prepared raw or half-cooked after treatment with salt or "bagoong" (salted fish paste). It was abundant in rice fields during the wet months of the year, thus implying a seasonal infection pattern since eating frequency was affected by availability. Those who ate this snail reported a long duration of indulgence with this habit. In contrast, Pila luzonica or "kuhol", the second intermediate host of E. ilocanum, is subjected to similar eating practices but is rarely ingested raw or "half-cooked". Other than snails, shrimps, fish (Tilapia sp.) and meat are also eaten raw. This suggests that the local population is potentially susceptible to other food-borne helminthiases. Extensive use of mass media and public health education is necessary to awaken the awareness of the people to the potential hazards associated with their traditional eating habits.

The life cycle of Ascocotyle (Phagicola) longa (Digenea: Heterophyidae), a causative agent of fish-borne trematodosis.

PubMed

Simões, Susana Balmant Emerique; Barbosa, Helene Santos; Santos, Cláudia Portes

2010-03-01

The complete life cycle of the trematode Ascocotyle (Phagicola) longa (Digenea: Heterophyidae) is elucidated by natural observation validated by experimental infections. The natural first intermediate host of A. (P.) longa, an agent of human heterophyiasis in Brazil, is the cochliopid snail Heleobia australis (new first intermediate host). Metacercariae were found encysted in the body musculature, heart, stomach, liver, kidney, spleen, gonads and mesentery of mullets Mugil liza. Hamsters Mesocricetus auratus were experimentally infected with metacercariae of A. (P.) longa obtained from the mullets, and the adults recovered were used to infect the snails H. australis. Rediae and cercariae of A. (P.) longa are described for the first time. The ultrastructure of the tegument of A. (P.) longa shows a change in spination pattern from the cercaria with single-pointed spines to the metacercaria and adult with multipointed, brush-shaped spines. The life cycle of A. (P.) longa is related to estuaries and coastal lagoons where the recruitment of mugilid juveniles occurs. The high prevalence (100%) of A. (P.) longa encysted in the mullets examined within the urban area of Rio de Janeiro indicates the potentially great public health impact of the consumption of raw mullets. Copyright 2009 Elsevier B.V. All rights reserved.

Ecology and distribution of Bulinus truncatus in the Middle East

PubMed Central

Watson, J. M.

1958-01-01

The author gives a comprehensive account of the present status of knowledge regarding the ecology and distribution of Bulinus truncatus, the intermediate host of Schistosoma haematobium in the Middle East and North Africa. He discusses in detail the types of habitat favoured by this snail, its life-cycle and seasonal variations in its populations, the effect of ecological factors on its distribution and occurrence, and the relationship between its control and its bionomics, stressing the many aspects of these subjects that require further investigation and suggesting lines for future research. In addition, the author outlines briefly the effect of some human activities (for example, extension of irrigation and agriculture), in their relationship to the snail host, on the incidence of bilharziasis haematobia in the Middle East and Africa. He concludes the paper with a summary of the three basic needs in respect of bilharziasis control: ecological research; prevention of pollution of waters with human excrement; and avoidance of human contact with infective water. PMID:13573115

OVICIDAL EFFECT OF PIPERACEAE SPECIES ON Biomphalaria glabrata, Schistosoma mansoni HOST

PubMed Central

Rapado, Ludmila Nakamura; Lopes, Priscila Orechio de Moraes; Yamaguchi, Lydia Fumiko; Nakano, Eliana

2013-01-01

SUMMARY Schistosomiasis is a neglected disease with public health importance in tropical and subtropical regions. An alternative to the disease control is the use of molluscicides to eliminate or reduce the intermediate host snail population causing a reduction of transmission in endemic regions. In this study nine extracts from eight Piperaceae species were evaluated against Biomphalaria glabrata embryos at blastula stage. The extracts were evaluated in concentrations ranging from 100 to 10 mg/L. Piper crassinervium and Piper tuberculatum extracts were the most active (100% of mortality at 20 mg/L and 30 mg/L respectively). PMID:24213196

Genetic variability and molecular identification of Brazilian Biomphalaria species (Mollusca: Planorbidae).

PubMed

Carvalho, S; Caldeira, R L; Simpson, A J; Vidigal, T H

2001-01-01

Freshwater snails belonging to the genus Biomphalaria are intermediate hosts of the trematode Schistosoma mansoni in the Neotropical region and Africa. In Brazil, one subspecies and ten species of Biomphalaria have been identified: B. glabrata, B. tenagophila, B. straminea, B. occidentalis, B. peregrina, B. kuhniana, B. schrammi, B. amazonica, B. oligoza, B. intermedia and B.t. guaibensis. However, only the first three species are found naturally infected with S. mansoni. The classical identification of these planorbids is based on comparison of morphological characteristics of the shell and male and female reproductive organs, which is greatly complicated by the extensive intra-specific variation. Several molecular techniques have been used in studies on the identification, genetic structure as well as phylogenetic relationships between these groups of organisms. Using the randomly amplified polymorphic DNAs (RAPD) analysis we demonstrated that B. glabrata exhibits a remarkable degree of intra-specific polymorphism. Thus, the genetics of the snail host may be more important to the epidemiology of schistosomiasis than those of the parasite itself. Using the simple sequence repeat anchored polymerase chain reaction (SSR-PCR) in intra-populational and intra-specific studies we have demonstrated that snails belonging to the B. straminea complex (B. straminea, B. kuhniana and B. intermedia) clearly presented higher heterogeneity. Using the low stringency polymerase chain reaction (LS-PCR) technique we were able to separate B. glabrata from B. tenagophila and B. tenagophila from B. occidentalis. To separate all Brazilian Biomphalaria species we used the restriction fragment length polymorphism (PCR-RFLP) of the internal transcribed spacer region (ITS) of the DNA gene. The method also proved to be efficient for the specific identification of DNA extracted from snail eggs. Recently we have sequenced the ITS2 region for phylogenetic studies of all Biomphalaria snails from Brazil.

Shading decreases the abundance of the herbivorous California horn snail, Cerithidea californica

USGS Publications Warehouse

Lorda, Julio; Lafferty, Kevin D.

2012-01-01

Most of the intertidal zone in estuaries of California, USA and Baja California, Mexico is covered with vascular vegetation. Shading by these vascular plants influences abiotic and biotic processes that shape benthic community assemblages. We present data on the effects of shading on the California horn snail, Cerithidea californica. This species is important because it is the most common benthic macrofaunal species in these systems and acts as an obligate intermediate host of several species of rematode parasites that infect several other species. Using observational and experimental studies, we found a negative effect of shade on the distribution and abundance of the California horn snail. We hypothesized that shading reduces the abundance of the epipelic diatoms that the snails feeds on, causing snails to leave haded areas. We observed a negative relationship between vascular plant cover, sub-canopy light levels, and snail density in Mugu Lagoon. Then we experimentally manipulated light regimes, by clipping vegetation and adding shade structures, and found higher snail densities at higher light levels. In Goleta Slough, we isolated the effect of shade from vegetation by documenting a negative relationship between the shade created by two bridges and diatom and snail densities. We also found that snails moved the greatest distances over shaded channel banks compared to unshaded channel banks. Further, we documented the effect of water depth and channel bank orientation on shading in this system. An additional effect of shading is the reduction of temperature, providing an alternative explanation for some of our results. These results broaden our knowledge of how variation in the light environment influences the ecology of estuarine ecosystems.

Cercarial emergence patterns for Opisthorchis viverrini sensu lato infecting Bithynia siamensis goniomphalos from Sakon Nakhon Province, Thailand.

PubMed

Laoprom, Nonglak; Kiatsopit, Nadda; Sithithaworn, Paiboon; Kopolrat, Kulthida; Namsanor, Jutamas; Andrews, Ross H; Petney, Trevor N

2016-09-01

Opisthorchis viverrini sensu lato is a food-borne trematode which is classified as a class 1 carcinogen, with infection potentially leading to cholangiocarcinoma. Snails of the genus Bithynia act as the first intermediate hosts and an amplifying point in the parasite life cycle. In order to investigate seasonal effect on transmission dynamics of O. viverrini in Bithynia siamensis goniomphalos, cercarial emergence and output profiles were monitored at different season. A total of 4533 snails originating from Sakon Nakhon Province, Thailand, collected during the three main seasons, were analyzed for O. viverrini s.l. Emergence of O. viverrini s.l. cercariae from snails was monitored daily from 06:00 to 18:00 h for seven consecutive days. The prevalence of infection in the snails was highest in the hot-dry season and declined in the rainy and cool-dry seasons. Peak cercarial emergence occurred between 08:00 and 10:00 h during the rainy and cool-dry seasons and between 10:00 and 12:00 h during the hot-dry season. The cercarial output was highest in the hot-dry season, similar to a previous study from Lao People's Democratic Republic (PDR). Average cercarial output/snail in Thailand was higher than in Lao PDR. The number of cercariae emerging from the snails was strongly related to snail size, but the relationship between prevalence of infection and snail size differed between seasons. Observed discrepancies in the emergence patterns and per capita cercarial release may reflect differences in environmental, snail, and/or parasite factors particularly biological characteristics between the cryptic species of O. viverrini s.l. and B. s. goniomphalos from Thailand and Lao PDR.

Schistosoma mansoni: resistant specific infection-induced gene expression in Biomphalaria glabrata identified by fluorescent-based differential display.

PubMed

Lockyer, Anne E; Noble, Leslie R; Rollinson, David; Jones, Catherine S

2004-01-01

The freshwater tropical snail Biomphalaria glabrata is an intermediate host for Schistosoma mansoni, the causative agent of human intestinal schistosomiasis, and strains differ in their susceptibility to parasite infection. Changes in gene expression in response to parasite infection have been simultaneously examined in a susceptible strain (NHM1742) and a resistant strain (NHM1981) using a newly developed fluorescent-based differential display method. Such RNA profiling techniques allow the examination of changes in gene expression in response to parasite infection, without requiring previous sequence knowledge, or selecting candidate genes that may be involved in the complex neuroendocrine or defence systems of the snail. Thus, novel genes may be identified. Ten transcripts were initially identified, present only in the profiles derived from snails of the resistant strain when exposed to infection. The differential expression of five of these genes, including HSP70 and several novel transcripts with one containing at least two globin-like domains, has been confirmed by semi-quantitative RT-PCR.

Application of Radar Altimetry Methods to Monitoring of Parasitic Disease Transmission: Schistosomiasis in Poyang Lake, China

NASA Astrophysics Data System (ADS)

McCandless, M.; Ibaraki, M.; Shum, C.; Lee, H.; Liang, S.

2008-12-01

Schistosomiasis is the second-most prevalent tropical disease after malaria affecting two-hundred million people annually world-wide; it shortens lifespan on average by ten years in endemic areas and no vaccine exists. The current control methods of human host chemotherapy and application of molluscicides to the environment do not break the disease transmission cycle. Schistosomiasis transmission in southern China involves an amphibious intermediate host snail for which hydrology is a key factor because the adults need moist vegetation while the juveniles are fully aquatic. Thus, hydrology is a key factor in schistosomiasis transmission and understanding its role can inform control measures. Our objective is to integrate hydrologic, ecologic, and other environmental factors to determine the changes in available snail habitat through space and time. We use radar altimetry measurements to determine water level every 35 days when the Envisat (Environmental Satellite) passes over the lake. The radar altimetry readings have been calibrated to levels from in-situ gauging stations and will support remote analysis of disease transmission potential without the need for gauging station data. A geographic information system was used to combine key factors including water level, topography, and air temperature data to identify areas of available snail habitat. In order to accomplish this, we conducted three steps including: delineating the watershed, specifying potential snail habitat areas through topography and air temperature classification, and calculating the intersection between potential snail habitat and non-flooded areas in the watershed. Statistical analyses of total available habitat area are also conducted. These maps and statistics analyses can be used by public health agencies to monitor snail habitat trends over time. Coupling remote sensing of water levels with a geographic information system model will continue to be important as the hydrology of the lake changes due to the completion of the upstream Three Gorges Dam project.

Monitoring Temporal Evolution of the Presence Intermediate Host of the Schistosomiasis and its Risk Transmission Based on Dragon Times Series in Poyang Lake Area Jiangxi Province, P.R. China

NASA Astrophysics Data System (ADS)

Marie, Tiphanie; Lai, Xijun; Huber, Claire; Chen, Xiaoling; Uribe, Carlos; Huang, Shifeng; LaCaux, Jean-Pierre; LaFaye, Murielle; Yesou, Herve

2010-12-01

Earth Observation data were used for mapping potential Schistosomiasis japonica distribution, within Poyang Lake (Jiangxi Province, PR China), as well as transmission risk associated with fishing activities. Areas suitable for the development of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum, were derived from submersion time parameters and vegetation community indicators. Monthly maps showing the annual dynamic of potential O. hupensis presence areas were obtained from December 2005 to December 2008. Human potential transmission risk was handled through the mapping of settlements and the identification of the principal human activity sensitive to transmission: fishing in the central part of Poyang Lake. Finally, data crossing of the different parameters highlight the potential risk of transmission in most of the fishing nets areas.

Identification of Potential High-Risk Habitats within the Transmission Reach of Oncomelania hupensis after Floods Based on SAR Techniques in a Plane Region in China

PubMed Central

Shi, Yuanyuan; Qiu, Juan; Li, Rendong; Shen, Qiang; Huang, Duan

2017-01-01

Schistosomiasis japonica is an infectious disease caused by Schistosoma japonicum, and it remains endemic in China. Flooding is the main hazard factor, as it causes the spread of Oncomelania hupensis, the only intermediate host of Schistosoma japonicum, thereby triggering schistosomiasis outbreaks. Based on multi-source real-time remote sensing data, we used remote sensing (RS) technology, especially synthetic aperture radar (SAR), and geographic information system (GIS) techniques to carry out warning research on potential snail habitats within the snail dispersal range following flooding. Our research result demonstrated: (1) SAR data from Sentinel-1A before and during a flood were used to identify submerged areas rapidly and effectively; (2) the likelihood of snail survival was positively correlated with the clay proportion, core area standard deviation, and ditch length but negatively correlated with the wetness index, NDVI (normalized difference vegetation index), elevation, woodland area, and construction land area; (3) the snail habitats were most abundant near rivers and ditches in paddy fields; (4) the rivers and paddy irrigation ditches in the submerged areas must be the focused of mitigation efforts following future floods. PMID:28867814

Identification of Potential High-Risk Habitats within the Transmission Reach of Oncomelania hupensis after Floods Based on SAR Techniques in a Plane Region in China.

PubMed

Shi, Yuanyuan; Qiu, Juan; Li, Rendong; Shen, Qiang; Huang, Duan

2017-08-30

Schistosomiasis japonica is an infectious disease caused by Schistosoma japonicum , and it remains endemic in China. Flooding is the main hazard factor, as it causes the spread of Oncomelania hupensis , the only intermediate host of Schistosoma japonicum , thereby triggering schistosomiasis outbreaks. Based on multi-source real-time remote sensing data, we used remote sensing (RS) technology, especially synthetic aperture radar (SAR), and geographic information system (GIS) techniques to carry out warning research on potential snail habitats within the snail dispersal range following flooding. Our research result demonstrated: (1) SAR data from Sentinel-1A before and during a flood were used to identify submerged areas rapidly and effectively; (2) the likelihood of snail survival was positively correlated with the clay proportion, core area standard deviation, and ditch length but negatively correlated with the wetness index, NDVI (normalized difference vegetation index), elevation, woodland area, and construction land area; (3) the snail habitats were most abundant near rivers and ditches in paddy fields; (4) the rivers and paddy irrigation ditches in the submerged areas must be the focused of mitigation efforts following future floods.

Reaching the Surveillance-Response Stage of Schistosomiasis Control in The People's Republic of China: A Modelling Approach.

PubMed

Feng, Y; Liu, L; Xia, S; Xu, J-F; Bergquist, R; Yang, G-J

2016-01-01

With the goal set to eliminate schistosomiasis nationwide by 2020, The People's Republic of China has initiated the surveillance-response stage to identify remaining sources of infection and potential pockets from where the disease could reemerge. Shifting the focus from classical monitoring and evaluation to rapid detection and immediate response, this approach requires modelling to bridge the surveillance and response components. We review here studies relevant to schistosomiasis modelling in a Chinese surveillance-response system with the expectation to achieve a practically useful understanding of the current situation and potential future study directions. We also present useful experience that could tentatively be applied in other endemic regions in the world. Modelling is discussed at length as it plays an essential role, both with regard to the intermediate snail host and in the definitive, mammal hosts. Research gaps with respect to snail infection, animal hosts and sectoral research cooperation are identified and examined against the prevailing background of ecosystem and socioeconomic changes with a focus on coexisting challenges and opportunities in a situation with increasing financial constraints. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ecological Model to Predict Potential Habitats of Oncomelania hupensis, the Intermediate Host of Schistosoma japonicum in the Mountainous Regions, China.

PubMed

Zhu, Hong-Ru; Liu, Lu; Zhou, Xiao-Nong; Yang, Guo-Jing

2015-01-01

Schistosomiasis japonica is a parasitic disease that remains endemic in seven provinces in the People's Republic of China (P.R. China). One of the most important measures in the process of schistosomiasis elimination in P.R. China is control of Oncomelania hupensis, the unique intermediate host snail of Schistosoma japonicum. Compared with plains/swamp and lake regions, the hilly/mountainous regions of schistosomiasis endemic areas are more complicated, which makes the snail survey difficult to conduct precisely and efficiently. There is a pressing call to identify the snail habitats of mountainous regions in an efficient and cost-effective manner. Twelve out of 56 administrative villages distributed with O. hupensis in Eryuan, Yunnan Province, were randomly selected to set up the ecological model. Thirty out of the rest of 78 villages (villages selected for building model were excluded from the villages for validation) in Eryuan and 30 out of 89 villages in Midu, Yunnan Province were selected via a chessboard method for model validation, respectively. Nine-year-average Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) as well as Digital Elevation Model (DEM) covering Eryuan and Midu were extracted from MODIS and ASTER satellite images, respectively. Slope, elevation and the distance from every village to its nearest stream were derived from DEM. Suitable survival environment conditions for snails were defined by comparing historical snail presence data and remote sensing derived images. According to the suitable conditions for snails, environment factors, i.e. NDVI, LST, elevation, slope and the distance from every village to its nearest stream, were integrated into an ecological niche model to predict O. hupensis potential habitats in Eryuan and Midu. The evaluation of the model was assessed by comparing the model prediction and field investigation. Then, the consistency rate of model validation was calculated in Eryuan and Midu Counties, respectively. The final ecological niche model for potential O. hupensis habitats prediction comprised the following environmental factors, namely: NDVI (≥ 0.446), LST (≥ 22.70°C), elevation (≤ 2,300 m), slope (≤ 11°) and the distance to nearest stream (≤ 1,000 m). The potential O. hupensis habitats in Eryuan distributed in the Lancang River basin and O. hupensis in Midu shows a trend of clustering in the north and spotty distribution in the south. The consistency rates of the ecological niche model in Eryuan and Midu were 76.67% and 83.33%, respectively. The ecological niche model integrated with NDVI, LST, elevation, slope and distance from every village to its nearest stream adequately predicted the snail habitats in the mountainous regions.

Effect of water temperature and population density on the population dynamics of Schistosoma mansoni intermediate host snails.

PubMed

McCreesh, Nicky; Arinaitwe, Moses; Arineitwe, Wilber; Tukahebwa, Edridah M; Booth, Mark

2014-11-12

Mathematical models can be used to identify areas at risk of increased or new schistosomiasis transmission as a result of climate change. The results of these models can be very different when parameterised to different species of host snail, which have varying temperature preferences. Currently, the experimental data needed by these models are available for only a few species of snail. The choice of density-dependent functions can also affect model results, but the effects of increasing densities on Biomphalaria populations have only previously been investigated in artificial aquariums. Laboratory experiments were conducted to estimate Biomphalaria sudanica mortality, fecundity and growth rates at ten different constant water temperatures, ranging from 13-32°C. Snail cages were used to determine the effects of snail densities on B. sudanica and B. stanleyi mortality and fecundity rates in semi-natural conditions in Lake Albert. B. sudanica survival and fecundity were highest at 20°C and 22°C respectively. Growth in shell diameter was estimated to be highest at 23°C in small and medium sized snails, but the relationship between temperature and growth was not clear. The fecundity of both B. sudanica and B. stanleyi decreased by 72-75% with a four-fold increase in population density. Increasing densities four-fold also doubled B. stanleyi mortality rates, but had no effect on the survival of B. sudanica. The optimum temperature for fecundity was lower for B. sudanica than for previously studied species of Biomphalaria. In contrast to other Biomphalaria species, B. sudanica have a distinct peak temperature for survival, as opposed to a plateau of highly suitable temperatures. For both B. stanleyi and B. sudanica, fecundity decreased with increasing population densities. This means that snail populations may experience large fluctuations in numbers, even in the absence of any external factors such as seasonal temperature changes. Survival also decreased with increasing density for B. stanleyi, in contrast to B. sudanica and other studied Biomphalaria species where only fecundity has been shown to decrease.

Ionotropic Receptors Identified within the Tentacle of the Freshwater Snail Biomphalaria glabrata, an Intermediate Host of Schistosoma mansoni

PubMed Central

Liang, Di; Wang, Tianfang; Rotgans, Bronwyn A.; McManus, Donald P.; Cummins, Scott F.

2016-01-01

Biomphalaria glabrata (B. glabrata) is an air-breathing aquatic mollusc found in freshwater habitats across the Western Hemisphere. It is most well-known for its recognized capacity to act as a major intermediate host for Schistosoma mansoni, the human blood fluke parasite. Ionotropic receptors (IRs), a variant family of the ionotropic glutamate receptors (iGluR), have an evolutionary ancient function in detecting odors to initiate chemosensory signaling. In this study, we applied an array of methods towards the goal of identifying IR-like family members in B. glabrata, ultimately revealing two types, the iGluR and IR. Sequence alignment showed that three ligand-binding residues are conserved in most Biomphalaria iGluR sequences, while the IRs did exhibit a variable pattern, lacking some or all known glutamate-interactingresidues, supporting their distinct classification from the iGluRs. We show that B. glabrata contains 7 putative IRs, some of which are expressed within its chemosensory organs. To further investigate a role for the more ancient IR25a type in chemoreception, we tested its spatial distribution pattern within the snail cephalic tentacle by in situ hybridization. The presence of IR25a within presumptive sensory neurons supports a role for this receptor in olfactory processing, contributing to our understanding of the molecular pathways that are involved in Biomphalaria olfactory processing. PMID:27253696

Pathology and first report of natural eye infection with the trematode Philophthalmus gralli (Digenea, Philophthalmidae) in Tinamus major (Tinamiformes, Tinamidae), Costa Rica.

PubMed

Rojas, Diana; Soto, Carmen; Rojas, Alicia

2013-12-01

The eye-fluke Philophthalmus gralli (Philophthalmidae Looss, 1899) was found in six birds known as great tinamous (Tinamus major) reared in a wild animal shelter located in Alajuela, Costa Rica. The birds presented conjunctival hyperemia, blepharitis, anorexia and weakness. Some of them suffered from unilateral blindness and ocular loss. After morphometric analysis, the specimens showed characteristics compatible with the digenean trematode P. gralli. The clinical signs of infection were resolved by manual removal of the adults, treatment with praziquantel and relocation into an environment without a natural water source. In order to determine if an ongoing cycle of this pathogen was present in the shelter, the habitat of the birds was inspected for the presence of infected intermediate hosts and contaminated water and objects. It was found that the snails Melanoides tuberculata acted as the intermediate host, and reared the infectious stages toward other animals, as shown by the reproduction of ocular philophthalmiasis in chickens artificially infected with excysted metacercaria. Moreover, three out of every ten snails found in the place were infected with rediae of P. gralli, raising the possibility of the dispersion of the parasite into new environments as well as the imminent zoonotic risk. The finding of P. gralli in Costa Rica is the first official report in Central America. © 2013.

Ionotropic Receptors Identified within the Tentacle of the Freshwater Snail Biomphalaria glabrata, an Intermediate Host of Schistosoma mansoni.

PubMed

Liang, Di; Wang, Tianfang; Rotgans, Bronwyn A; McManus, Donald P; Cummins, Scott F

2016-01-01

Biomphalaria glabrata (B. glabrata) is an air-breathing aquatic mollusc found in freshwater habitats across the Western Hemisphere. It is most well-known for its recognized capacity to act as a major intermediate host for Schistosoma mansoni, the human blood fluke parasite. Ionotropic receptors (IRs), a variant family of the ionotropic glutamate receptors (iGluR), have an evolutionary ancient function in detecting odors to initiate chemosensory signaling. In this study, we applied an array of methods towards the goal of identifying IR-like family members in B. glabrata, ultimately revealing two types, the iGluR and IR. Sequence alignment showed that three ligand-binding residues are conserved in most Biomphalaria iGluR sequences, while the IRs did exhibit a variable pattern, lacking some or all known glutamate-interactingresidues, supporting their distinct classification from the iGluRs. We show that B. glabrata contains 7 putative IRs, some of which are expressed within its chemosensory organs. To further investigate a role for the more ancient IR25a type in chemoreception, we tested its spatial distribution pattern within the snail cephalic tentacle by in situ hybridization. The presence of IR25a within presumptive sensory neurons supports a role for this receptor in olfactory processing, contributing to our understanding of the molecular pathways that are involved in Biomphalaria olfactory processing.

Urinary Schistosomiasis in Urban and Semi-Urban Communities in South-Eastern Nigeria

PubMed Central

OKEKE, Ogochukwu Caroline; UBACHUKWU, Patience Obiageli

2013-01-01

Background In view of the massive rural-to-urban migration in Nigeria, investigations on transmission of urinary schistosomiasis were carried out in urban and semi-urban communities in Nike Lake area of Enugu State, Nigeria. Methods Urine samples of school children were tested for micro-haematuria using reagent strips followed by microscopic examination for Schistosoma haematobium eggs. Water contact sites were also identified and sampled for snails. Results The overall prevalence of S. haematobium eggs in school children was 4.64%. The mean intensity of infection was 1.14 ± 0.41 eggs/10ml urine. Males had insignificantly higher prevalence and intensity of S. haematobium infection than females. The youngest age group (4-7 years) had no infection. The prevalence of micro-haematuria (6.2%) was higher than that of microscopy, and this correlated positively with prevalence (r = 0.65, P < 0.01) and intensity (r = 0.50, P < 0.01) of the infection. Potential intermediate host of human shistosome collected were: Bulinus globosus, B. senegalensis and Biomphalaria pfeifferi. However, only B. globosus shed cercariae of S. haematobium, with a snail infection rate of 0.73%. Transmission was in the dry season coinciding with the drying of wells. Conclusion The results revealed that urinary schistosomiasis is prevalent, and that B. globosus and not B. truncatus as previously reported is the main intermediate host of urinary schistosomiasis in this part of Enugu State. PMID:24454442

Urinary schistosomiasis in urban and semi-urban communities in South-eastern Nigeria.

PubMed

Okeke, Ogochukwu Caroline; Ubachukwu, Patience Obiageli

2013-07-01

In view of the massive rural-to-urban migration in Nigeria, investigations on transmission of urinary schistosomiasis were carried out in urban and semi-urban communities in Nike Lake area of Enugu State, Nigeria. Urine samples of school children were tested for micro-haematuria using reagent strips followed by microscopic examination for Schistosoma haematobium eggs. Water contact sites were also identified and sampled for snails. The overall prevalence of S. haematobium eggs in school children was 4.64%. The mean intensity of infection was 1.14 ± 0.41 eggs/10ml urine. Males had insignificantly higher prevalence and intensity of S. haematobium infection than females. The youngest age group (4-7 years) had no infection. The prevalence of micro-haematuria (6.2%) was higher than that of microscopy, and this correlated positively with prevalence (r = 0.65, P < 0.01) and intensity (r = 0.50, P < 0.01) of the infection. Potential intermediate host of human shistosome collected were: Bulinus globosus, B. senegalensis and Biomphalaria pfeifferi. However, only B. globosus shed cercariae of S. haematobium, with a snail infection rate of 0.73%. Transmission was in the dry season coinciding with the drying of wells. The results revealed that urinary schistosomiasis is prevalent, and that B. globosus and not B. truncatus as previously reported is the main intermediate host of urinary schistosomiasis in this part of Enugu State.

Heterophysiasis, an intestinal fluke infection of man and vertebrates transmitted by euryhaline gastropods and fish

NASA Astrophysics Data System (ADS)

Taraschewski, H.

1984-03-01

Heterophyes heterophyes, agent of human heterophyiasis in the Near East, is transmitted in marine lagoons and saline inland waters, where the euryhaline intermediate hosts are abundant. In Egypt, mullets, the predominant second intermediate hosts, are customarily consumed raw; thus man becomes infected easily. Symptoms of human infections are usually considered mild. Mullets do not seem to be affected by the metacercariae encysted in the muscles, whereas the growth of the snail host Pirenella conica was found to be enhanced due to the infestation by the trematodes. In laboratory experiments, the flukes were found to be well developed in dogs, foxes and cats, but failed to reach sexual maturity in several other potentially piscivorous mammals and birds. In nature, dogs probably serve as the major reservoir hosts. Heterophyiasis is most prevalent in the Nile Delta, a huge brackish water area which is densely populated by humans and, consequently, also by dogs and cats. In the Far East, besides Heterophyes nocens, several other heterophysids with marine or fresh-water life-cycles are known to infect humans.

A field survey using LAMP assay for detection of Schistosoma mansoni in a low-transmission area of schistosomiasis in Umbuzeiro, Brazil: Assessment in human and snail samples.

PubMed

Gandasegui, Javier; Fernández-Soto, Pedro; Muro, Antonio; Simões Barbosa, Constança; Lopes de Melo, Fabio; Loyo, Rodrigo; de Souza Gomes, Elainne Christine

2018-03-01

In Brazil, schistosomiasis is a parasitic disease of public health relevance, mainly in poor areas where Schistosoma mansoni is the only human species encountered and Biomphalaria straminea is one of the intermediate host snails. A nested-PCR based on a specific mitochondrial S. mansoni minisatellite DNA region has been successfully developed and applied as a reference method in Brazil for S. mansoni detection, mainly in host snails for epidemiological studies. The amplification efficiency of LAMP is known to be higher than PCR. The present work aimed to assess the utility of our previously described SmMIT-LAMP assay for S. mansoni detection in human stool and snail samples in a low-transmission area of schistosomiasis in the municipality of Umbuzeiro, Paraíba State, Northeast Region of Brazil. A total of 427 human stool samples were collected during June-July 2016 in the municipality of Umbuzeiro and an overall prevalence of 3.04% (13/427) resulted positive by duplicate Kato-Katz thick smear. A total of 1,175 snails identified as Biomphalaria straminea were collected from 14 breeding sites along the Paraíba riverbank and distributed in 46 pools. DNA from human stool samples and pooled snails was extracted using the phenol/chloroform method. When performing the SmMIT-LAMP assay a total of 49/162 (30.24%) stool samples resulted positive, including 12/13 (92.31%) that were Kato-Katz positive and 37/149 (24.83%) previously Kato-Katz negative. By nested-PCR, only 1/46 pooled DNA snail samples was positive. By SmMIT-LAMP assay, the same sample also resulted positive and an additional one was positive from a different breeding site. Data of human and snail surveys were used to build risk maps of schistosomiasis incidence using kernel density analysis. This is the first study in which a LAMP assay was evaluated in both human stool and snail samples from a low-transmission schistosomiasis-endemic area. Our SmMIT-LAMP proved to be much more efficient in detection of S. mansoni in comparison to the 'gold standard' Kato-Katz method in human stool samples and the reference molecular nested-PCR in snails. The SmMIT-LAMP has demonstrated to be a useful molecular tool to identify potential foci of transmission in order to build risk maps of schistosomiasis.

Quantitative estimation of the cost of parasitic castration in a Helisoma anceps population using a matrix population model.

PubMed

Negovetich, N J; Esch, G W

2008-10-01

Larval trematodes frequently castrate their snail intermediate hosts. When castrated, the snails do not contribute offspring to the population, yet they persist and compete with the uninfected individuals for the available food resources. Parasitic castration should reduce the population growth rate lambda, but the magnitude of this decrease is unknown. The present study attempted to quantify the cost of parasitic castration at the level of the population by mathematically modeling the population of the planorbid snail Helisoma anceps in Charlie's Pond, North Carolina. Analysis of the model identified the life-history trait that most affects lambda, and the degree to which parasitic castration can lower lambda. A period matrix product model was constructed with estimates of fecundity, survival, growth rates, and infection probabilities calculated in a previous study. Elasticity analysis was performed by increasing the values of the life-history traits by 10% and recording the percentage change in lambda. Parasitic castration resulted in a 40% decrease in lambda of H. anceps. Analysis of the model suggests that decreasing the size at maturity was more effective at reducing the cost of castration than increasing survival or growth rates of the snails. The current matrix model was the first to mathematically describe a snail population, and the predictions of the model are in agreement with published research.

Relationship between snail population density and infection status of snails and fish with zoonotic trematodes in Vietnamese carp nurseries.

PubMed

Clausen, Jesper Hedegaard; Madsen, Henry; Murrell, K Darwin; Phan Thi, Van; Nguyen Manh, Hung; Viet, Khue Nguyen; Dalsgaard, Anders

2012-01-01

Fish-borne zoonotic trematodes (FZT) are a food safety and health concern in Vietnam. Humans and other final hosts acquire these parasites from eating raw or under-cooked fish with FZT metacercariae. Fish raised in ponds are exposed to cercariae shed by snail hosts that are common in fish farm ponds. Previous risk assessment on FZT transmission in the Red River Delta of Vietnam identified carp nursery ponds as major sites of transmission. In this study, we analyzed the association between snail population density and heterophyid trematode infection in snails with the rate of FZT transmission to juvenile fish raised in carp nurseries. Snail population density and prevalence of trematode (Heterophyidae) infections were determined in 48 carp nurseries producing Rohu juveniles, (Labeo rohita) in the Red River Delta area. Fish samples were examined at 3, 6 and 9 weeks after the juvenile fish were introduced into the ponds. There was a significant positive correlation between prevalence of FZT metacercariae in juvenile fish and density of infected snails. Thus, the odds of infection in juvenile fish were 4.36 and 11.32 times higher for ponds with medium and high density of snails, respectively, compared to ponds where no infected snails were found. Further, the intensity of fish FZT infections increased with the density of infected snails. Interestingly, however, some ponds with no or few infected snails were collected also had high prevalence and intensity of FZT in juvenile fish. This may be due to immigration of cercariae into the pond from external water sources. The total number and density of potential host snails and density of host snails infected with heterophyid trematodes in the aquaculture pond is a useful predictor for infections in juvenile fish, although infection levels in juvenile fish can occur despite low density or absence infected snails. This suggests that intervention programs to control FZT infection of fish should include not only intra-pond snail control, but also include water sources of allochthonous cercariae, i.e. canals supplying water to ponds as well as snail habitats outside the pond such as rice fields and surrounding ponds.

Multi level ecological fitting: indirect life cycles are not a barrier to host switching and invasion.

PubMed

Malcicka, Miriama; Agosta, Salvatore J; Harvey, Jeffrey A

2015-09-01

Many invasive species are able to escape from coevolved enemies and thus enjoy a competitive advantage over native species. However, during the invasion phase, non-native species must overcome many ecological and/or physiological hurdles before they become established and spread in their new habitats. This may explain why most introduced species either fail to establish or remain as rare interstitials in their new ranges. Studies focusing on invasive species have been based on plants or animals where establishment requires the possession of preadapted traits from their native ranges that enables them to establish and spread in their new habitats. The possession of preadapted traits that facilitate the exploitation of novel resources or to colonize novel habitats is known as 'ecological fitting'. Some species have evolved traits and life histories that reflect highly intimate associations with very specific types of habitats or niches. For these species, their phenological windows are narrow, and thus the ability to colonize non-native habitats requires that a number of conditions need to be met in accordance with their more specialized life histories. Some of the strongest examples of more complex ecological fitting involve invasive parasites that require different animal hosts to complete their life cycles. For instance, the giant liver fluke, Fascioloides magna, is a major parasite of several species of ungulates in North America. The species exhibits a life cycle whereby newly hatched larvae must find suitable intermediate hosts (freshwater snails) and mature larvae, definitive hosts (ungulates). Intermediate and definitive host ranges of F. magna in its native range are low in number, yet this parasite has been successfully introduced into Europe where it has become a parasite of native European snails and deer. We discuss how the ability of these parasites to overcome multiple ecophysiological barriers represents an excellent example of 'multiple-level ecological fitting'. © 2015 John Wiley & Sons Ltd.

[Occurrence of Achatina fulica in the Vale do Paraíba, Rio de Janeiro state, Brazil].

PubMed

Vasconcellos, M C; Pile, E

2001-12-01

The first occurrence of the Achatina fulica, an intermediate host of Angiostrongylus cantonensis, the etiological agent of meningoencephalic angiostrongiliasis, is reported in Resende municipality, Brazil. In the five visited localities, snails were found living freely, and the larvae of this parasite was not seen in any of them. The finding of A. fulica in the area may be related to its commercialization as a food item and embodies the possibility of new focus.

Cytometric analysis, genetic manipulation and antibiotic selection of the snail embryonic cell line Bge from Biomphalaria glabrata, the intermediate host of Schistosoma mansoni.

PubMed

Rinaldi, Gabriel; Yan, Hongbin; Nacif-Pimenta, Rafael; Matchimakul, Pitchaya; Bridger, Joanna; Mann, Victoria H; Smout, Michael J; Brindley, Paul J; Knight, Matty

2015-07-01

The invertebrate cell line, Bge, from embryos of the snail Biomphalaria glabrata, remains to date the only established cell line from any species of the Phylum Mollusca. Since its establishment in 1976 by Eder Hansen, few studies have focused on profiling its cytometrics, growth characteristics or sensitivity to xenobiotics. Bge cells are reputed to be challenging to propagate and maintain. Therefore, even though this cell line is a noteworthy resource, it has not been studied widely. With growing interest in functional genomics, including genetic transformation, to elucidate molecular aspects of the snail intermediate hosts responsible for transmission of schistosomiasis, and aiming to enhance the convenience of maintenance of this molluscan cell line, we deployed the xCELLigene real time approach to study Bge cells. Doubling times for three isolates of Bge, termed CB, SL and UK, were longer than for mammalian cell lines - longer than 40 h in complete Bge medium supplemented with 7% fetal bovine serum at 25°C, ranging from ∼42 h to ∼157 h when 40,000 cells were seeded. To assess the potential of the cells for genetic transformation, antibiotic selection was explored. Bge cells were sensitive to the aminonucleoside antibiotic puromycin (from Streptomyces alboniger) from 5 μg/ml to 200 ng/ml, displaying a half maximal inhibitory concentration (IC50) of ∼1.91 μg/ml. Sensitivity to puromycin, and a relatively quick kill time (<48 h in 5 μg/ml) facilitated use of this antibiotic, together with the cognate resistance gene (puromycin N-acetyl-transferase) for selection of Bge cells transformed with the PAC gene (puroR). Bge cells transfected with a plasmid encoding puroR were partially rescued when cultured in the presence of 5 μg/ml of puromycin. These findings pave the way for the development of functional genomic tools applied to the host-parasite interaction during schistosomiasis and neglected tropical trematodiases at large. Copyright © 2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Simultaneous infection of Schistosoma mansoni and S. rodhaini in Biomphalaria glabrata: impact on chronobiology and cercarial behaviour

PubMed Central

Norton, Alice; Rollinson, David; Richards, Louisa; Webster, Joanne

2008-01-01

Background The chances of a schistosome cercaria encountering a suitable definitive host may be enhanced by emergence from the molluscan intermediate host with maximal glycogen stores and by an appropriate chronobiological rhythm. This study aimed to identify and characterize the effects of potential competitive interactions in the snail host Biomphalaria glabrata, between the closely-related Schistosoma mansoni and S. rodhaini, on phenotypic behavioural traits. It was predicted that inter-specific competition would affect chronobiological emergence rhythms and reduce the activity of schistosome swimming behavioural traits. Biomphalaria glabrata snails (120) were exposed to either S. mansoni or S. rodhaini single infections, or a mixed infection of both species simultaneously and the resulting cercarial phenotypic traits were characterised. Cercariae were identified from co-exposed snails by amplification and sequencing of the mitochondrial cytochrome oxidase subunit 1 (CO1). Results S. mansoni and S. rodhaini largely maintained their distinct chronobiological rhythms after mixed exposures and infections. However, inter-specific competition appeared to result in a restriction of the shedding pattern of S. rodhaini and slight shift in the shedding pattern of S. mansoni. Inter-specific competition also significantly lowered hourly cercarial production for both parasite species in comparison to single exposures and infections and reduced cercarial swimming activity. Conclusion Inter-specific competition was shown to influence cercarial production, chronobiology and activity and should therefore be investigated further in field situations to determine the effects of these changes on parasite fitness (incorporating both host finding and infectivity) where these two species overlap. Importantly this competition did not result in a large change in chronobiological emergence of cercariae for either species indicating that it would not have a large influence on the species of hosts available for infection at time of emergence. This study has furthermore demonstrated the potential for phenotypic measures to provide markers for species-specific identification even in conditions of co-infection. PMID:19055722

New locality record for Haplorchoides mehrai and possible interactions with Opisthorchis viverrini metacercariae in cyprinid fishes in Northeast Thailand.

PubMed

Manpratum, Yupin; Kaewkes, Wanlop; Echaubard, Pierre; Sripa, Banchob; Kaewkes, Sasithorn

2017-02-01

Metacercariae of Opisthorchis viverrini, a carcinogenic liver fluke, and Haplorchoides sp., a trematode maturing in catfish, are commonly found in cyprinid fish, the second intermediate hosts of both flukes. However, the specific identity of Haplorchoides sp. in Thailand and a precise assessment of the effects of co-infections with O. viverrini have never been clarified. Therefore, we aimed to identify the species of Haplorchoides and to investigate possible interactions of the two trematode species in cyprinid fishes. Based on the morphology and morphometry of the cercaria, metacercaria, and adult stages, the Haplorchoides species found was identified as Haplorchoides mehrai Pande and Shukla 1976. Thailand is formally recorded as a new locality for H. mehrai, where naturally infected hosts include the snail Melanoides tuberculata (first intermediate host), the cyprinid fishes Hampala dispar, Cyclocheilichthys apogon, Puntius leiacanthus, Labiobarbus burmanicus, and Cirrhina jullieni (second intermediate hosts), and a catfish, Mystus nemurus (definitive host). The co-infection rates of O. viverrini and H. mehrai were significantly associated with fish species and fish body region (P < 0.001), with an overall significantly higher average intensity of H. mehrai (126.26 metacercariae/fish) than that of O. viverrini (18.02 metacercariae/fish). Further work is required to demonstrate the extent and mechanisms of possible interactions between these trematode species in the fish host. These data may provide a better understanding of O. viverrini transmission dynamics, and help design integrated control interventions.

DNA Barcode Identification of Freshwater Snails in the Family Bithyniidae from Thailand

PubMed Central

Kulsantiwong, Jutharat; Prasopdee, Sattrachai; Ruangsittichai, Jiraporn; Ruangjirachuporn, Wipaporn; Boonmars, Thidarut; Viyanant, Vithoon; Pierossi, Paola; Hebert, Paul D. N.; Tesana, Smarn

2013-01-01

Freshwater snails in the family Bithyniidae are the first intermediate host for Southeast Asian liver fluke (Opisthorchis viverrini), the causative agent of opisthorchiasis. Unfortunately, the subtle morphological characters that differentiate species in this group are not easily discerned by non-specialists. This is a serious matter because the identification of bithyniid species is a fundamental prerequisite for better understanding of the epidemiology of this disease. Because DNA barcoding, the analysis of sequence diversity in the 5’ region of the mitochondrial COI gene, has shown strong performance in other taxonomic groups, we decided to test its capacity to resolve 10 species/ subspecies of bithyniids from Thailand. Our analysis of 217 specimens indicated that COI sequences delivered species-level identification for 9 of 10 currently recognized species. The mean intraspecific divergence of COI was 2.3% (range 0-9.2 %), whereas sequence divergences between congeneric species averaged 8.7% (range 0-22.2 %). Although our results indicate that DNA barcoding can differentiate species of these medically-important snails, we also detected evidence for the presence of one overlooked species and one possible case of synonymy. PMID:24223896

Observations on the distribution of freshwater mollusca and chemistry of the natural waters in the south-eastern Transvaal and adjacent northern Swaziland*

PubMed Central

Schutte, C. H. J.; Frank, G. H.

1964-01-01

An extensive survey of the molluscan fauna and of the chemistry of the freshwaters of the Eastern Transvaal Lowveld has revealed no simple correlation between the two. The waters fall into four fairly distinct and geographically associated groups chiefly characterized by their calcium and magnesium content. The frequency of the two intermediate hosts of bilharziasis was found to be roughly proportional to the hardness of the water but as the latter, in this area, is associated with altitude and this again with temperature and stream gradient it is thought highly probable that the distribution of these snails is the result of the interaction of a complex of factors. None of the individual chemical constituents in any of the waters examined is regarded as outside the tolerance range of these snails. It is also concluded that under natural conditions this area would have had few waterbodies suitable for colonization by these snails but that the expansion of irrigation schemes has created ideal conditions for their rapid establishment throughout the area. PMID:14163962

Genetic structure of faucet snail, Bithynia tentaculata populations in North Americal based on microsattelite markers

USGS Publications Warehouse

Perez, Kathryn E.; Werren, Rebecca L.; Lynum, Christopher A.; Hartman, Levi A.; Majoros, Gabor; Cole, Rebecca A.

2016-01-01

Bithynia tentaculata is believed to have been extirpated from North America during the last glacial maximum. It was reintroduced into North America via the Great Lakes basin in the 1800’s and has recently been expanding its geographic range. This snail serves as intermediate host for three trematodes that cause extensive recurring morbidity and mortality events in migratory water birds along the Mississippi River. Using twelve microsatellite loci for ~200 individual snails from 11 populations in North America and Europe, we examined one of the three major geographic regions from which founding populations into the Great Lakes typically originate. Our data supports a single recolonization of North America into the Great Lakes Basin followed by subsequent introduction events from the Great Lakes to other large watersheds in North America. However, additional watersheds in Europe require sampling to confirm this result. No populations with genetic signatures indicative of North American glacial relics were found. The initial invasion of North America was likely not from the Ponto-Caspian basin, the usual source of freshwater invasive species to the Laurentian Great Lakes.

Optimizing molluscicide treatment strategies in different control stages of schistosomiasis in the People's Republic of China.

PubMed

Yang, Guo-Jing; Sun, Le-Ping; Hong, Qing-Biao; Zhu, Hong-Ru; Yang, Kun; Gao, Qi; Zhou, Xiao-Nong

2012-11-14

The application of chemical molluscicides is still one of the most effective measures for schistosomiasis control in P. R. China. By applying diverse molluscicide treatment scenarios on different snail densities in the field, we attempted to understand the cost-effectiveness of molluscicide application so as to prescribe an optimal management approach to control intermediate host snail Oncomelania hupensis under acceptable thresholds based on the goal of the National Schistosomiasis Control Programme. The molluscicidal field trial was carried out in the marshland of an island along the Yangtze River, Jiangsu province, P.R. China in October 2010. Three plots in the island representing low-density, medium-density and high-density groups were identified after the baseline survey on snail density. Each snail density plot was divided into four experimental units in which molluscicide (50% niclosamide ethanolamine salt wettable powder) was applied once, twice, trice and four times, respectively. The logistic regression model to correlate snail mortality rate with the covariates of number of molluscicidal treatment and snail density, and a linear regression model to investigate the relationship between cost-effectiveness and number of molluscicidal treatment as well as snail density were established. The study revealed that increase in the number of molluscicide treatments led to increased snail mortality across all three population density groups. The most cost-effective regimen was seen in the high snail density group with a single molluscicide treatment. For both high and low density groups, the more times molluscicide were applied, the less cost-effectiveness was. However, for the median density group, the level of cost-effectiveness for two applications was slightly higher than that in one time. We concluded that different stages of the national schistosomiasis control/elimination programme, namely morbidity control, transmission control and transmission interruption, should utilize different molluscicide treatment strategies to maximize cost-effectiveness.

Schistosomin: a pronase-sensitive agent in the hemolymph of Trichobilharzia ocellata-infected Lymnaea stagnalis inhibits the activity of albumen glands in vitro.

PubMed

Joosse, J; van Elk, R; Mosselman, S; Wortelboer, H; van Diepen, J C

1988-01-01

The schistosome parasite, Trichobilharzia ocellata, nearly completely inhibits the reproductive activity of its intermediate host, Lymnaea stagnalis. The synthetic activity of albumen glands of infected snails at day 35 postinfection (p.i.) is only 1% of the control value. The parasite acts by humoral means. We tested the hypothesis that (a) specific humoral agent(s) is (are) involved and refer to this (these) agent(s) as schistosomin. The presence of schistosomin in the hemolymph of infected snails was investigated by using galactogen synthesis in albumen glands as an in vitro bioassay. The synthetic activity of albumen glands of noninfected snails decreased by about 50% during a 1-h incubation in the hemolymph of infected snails. This inhibition is attributed to schistosomin. Based on these results, with the present bioassay schistosomin appears in the hemolymph between days 28-36 p.i. onwards. Schistosomin is heat-stable (100 degrees C) and pronase-sensitive, and therefore it might have a peptide nature. Schistosomin suppresses the stimulating action of the female, gonadotrophic dorsal body hormone at relatively low doses, which suggests that it may compete with this hormone for the same receptors. The development of two other bioassays for schistosomin in our laboratory is discussed.

Assessing the role of landscape connectivity on Opisthorchis viverrini transmission dynamics.

PubMed

Wang, Yi-Chen; Yuen, Roy; Feng, Chen-Chieh; Sithithaworn, Paiboon; Kim, Ick-Hoi

2017-08-01

Opisthorchis viverrini (Ov) is one of the most important human parasitic diseases in Southeast Asia. Although the concept of connectivity is widely used to comprehend disease dispersal, knowledge of the influences of landscape connectivity on Ov transmission is still rudimentary. This study aimed to investigate the role of landscape connectivity in Ov transmission between the human and the first intermediate snail hosts. Fieldwork was conducted in three villages respectively in Kamalasai District, Kalasin Province, Phu Wiang District, Khon Kaen Province, and Nong Saeng District, Udon Thani Province. Bithynia snails were collected to examine parasitic infections, water samples were analyzed for fecal contamination, and locations of septic tanks and connections between habitat patches with observable water movement were surveyed. Euclidean distance, topological link and distance, and graph measures were employed to quantify the connectivity between human and snail habitats. The findings showed that snail patches with higher fecal contents were generally located nearer to septic tanks. The statistically significant results for the topological link and distance measures highlighted the importance of water in functionally facilitating Ov transmission. Graph measures revealed differences in landscape connectivity across the sites. The site with the largest landscape component size and the most mutually connected snail patches coincided with the presence of Ov parasite, reinforcing its higher risk for human to snail transmission. The site with the dissected landscape structure potentially limited the transmission. This study underscored the potential effect of landscape connectivity on Ov transmission, contributing to the understanding of the spatial variation of Ov infection risk. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Characterization of immune genes from the schistosome host snail Biomphalaria glabrata that encode peptidoglycan recognition proteins and gram-negative bacteria binding protein

PubMed Central

Zeng, Yong; Loker, Eric S.

2013-01-01

Peptidoglycan (PGN) recognition proteins (PGRPs) and gram-negative bacteria binding proteins (GNBPs) play an essential role in Toll/Imd signaling pathways in arthropods. The existence of homologous pathways involving PGRPs and GNBPs in other major invertebrate phyla such as the Mollusca remains unclear. In this paper, we report four full-length PGRP cDNAs and one full-length GNBP cDNA cloned from the snail Biomphalaria glabrata, the intermediate host of the human blood fluke Schistosoma mansoni, designated as BgPGRPs and BgGNBP, respectively. Three transcripts are generated from a long form PGRP gene (BgPGRP-LA) by alternative splicing and one from a short form PGRP gene (BgPGRP-SA). BgGNBP encodes a putative secreted protein. Northern blots demonstrated that expression of BgPGRP-SA and BgGNBP was down-regulated in B. glabrata at 6 h after exposure to three types of microbes. No significant changes in expression were observed in snails at 2 days post-exposure (dpe) to the trematodes Echinostoma paraensei or S. mansoni. However, up-regulation of BgPGRP-SA in M line snails at later time points of infection with E. paraensei (i.e., 12 and 17 dpe) was observed. Our study revealed that exposure to either microbes or trematodes did not alter the expression levels of BgPGRP-LAs, which were consistently low. This study provides new insights into the potential pathogen recognition capabilities of molluscs, indicates that further studies of the Toll/Imd pathways in this phylum are in order, and provides additional ways to judge the importance of this pathway in the evolution of internal defense across the animal phyla. PMID:17805526

Endangered light-footed clapper rail affects parasite community structure in coastal wetlands

USGS Publications Warehouse

Whitney, Kathleen L.; Hechinger, Ryan F.; Kuris, Armand M.; Lafferty, Kevin D.

2007-01-01

An extinction necessarily affects community members that have obligate relationships with the extinct species. Indirect or cascading effects can lead to even broader changes at the community or ecosystem level. However, it is not clear whether generalist parasites should be affected by the extinction of one of their hosts. We tested the prediction that loss of a host species could affect the structure of a generalist parasite community by investigating the role of endangered Light-footed Clapper Rails (Rallus longirostris levipes) in structuring trematode communities in four tidal wetlands in southern California, USA (Carpinteria Salt Marsh, Mugu Lagoon) and Mexico (Estero de Punta Banda, Bahia Falsa–San Quintín). We used larval trematode parasites in first intermediate host snails (Cerithidea californica) as windows into the adult trematodes that parasitize Clapper Rails. Within and among wetlands, we found positive associations between Clapper Rails and four trematode species, particularly in the vegetated marsh habitat where Clapper Rails typically occur. This suggests that further loss of Clapper Rails is likely to affect the abundance of several competitively dominant trematode species in wetlands with California horn snails, with possible indirect effects on the trematode community and changes in the impacts of these parasites on fishes and invertebrates.

Drivers of symbiont diversity in freshwater snails: a comparative analysis of resource availability, community heterogeneity, and colonization opportunities

PubMed Central

McCaffrey, Keegan; Johnson, Pieter T. J.

2017-01-01

Decades of community ecology research have highlighted the importance of resource availability, habitat heterogeneity, and colonization opportunities in driving biodiversity. Less clear, however, is whether a similar suite of factors explains the diversity of symbionts. Here, we used a hierarchical dataset involving 12,712 freshwater snail hosts representing five species to test the relative importance of potential factors in driving symbiont richness. Specifically, we used model selection to assess the explanatory power of variables related to host species identity, resource availability (average body size, host density), ecological heterogeneity (richness of hosts and other taxa), and colonization opportunities (wetland size and amount of neighboring wetland area) on symbiont richness in 146 snail host populations in California, USA. We encountered a total of 24 taxa of symbionts, including both obligatory parasites such as digenetic trematodes as well as more commensal, mutualistic, or opportunistic groups such as aquatic insect larvae, annelids, and leeches. After validating richness estimates per host population using species accumulative curves, we detected positive effects on symbiont richness from host body size, total richness of the aquatic community, and colonization opportunities. Neither snail density nor the richness of snail species accounted for significant variation in symbiont diversity. Host species identity also affected symbiont richness, with higher gamma and average alpha diversity among more common host species and with higher local abundances. These findings highlight the importance of multiple, concurrent factors in driving symbiont richness that extend beyond epidemiological measures of host abundance or host diversity alone. PMID:28039528

Prediction of the potential global distribution for Biomphalaria straminea, an intermediate host for Schistosoma mansoni

PubMed Central

Yang, Ya; Cheng, Wanting; Wu, Xiaoying; Huang, Shaoyu; Deng, Zhuohui; Zeng, Xin; Yang, Yu; Wu, Zhongdao; Chen, Yue; Zhou, Yibiao; Jiang, Qingwu

2018-01-01

Background Schistosomiasis is a snail-borne parasitic disease and is endemic in many tropical and subtropical countries. Biomphalaria straminea, an intermediate host for Schistosoma mansoni, is native to the southeastern part of South America and has established in other regions of South America, Central America and southern China during the last decades. S. mansoni is endemic in Africa, the Middle East, South America and the Caribbean. Knowledge of the potential global distribution of this snail is essential for risk assessment, monitoring, disease prevention and control. Methods and findings A comprehensive database of cross-continental occurrence for B. straminea was compiled to construct ecological models. We used several approaches to investigate the distribution of B. straminea, including direct comparison of climatic conditions, principal component analysis and niche overlap analyses to detect niche shifts. We also investigated the impacts of bioclimatic and human factors, and then used the bioclimatic and footprint layers to predict the potential distribution of B. straminea at global scale. We detected niche shifts accompanying the invasions of B. straminea in the Americas and China. The introduced populations had enlarged its habitats to subtropical regions where annual mean temperature is relatively low. Annual mean temperature, isothermality and temperature seasonality were identified as most important climatic features for the occurrence of B. straminea. Additionally, human factors improved the model prediction (P<0.001). Our model showed that under current climate conditions the snail should mostly be confined to the tropic and subtropic regions, including South America, Central America, Sub-Saharan Africa and Southeast Asia. Conclusions Our results confirmed that niche shifts took place in the invasions of B. straminea, in which bioclimatic and human factors played an important role. Our model predicted the global distribution of B. straminea based on habitat suitability, which would help for prioritizing monitoring and management efforts for B. straminea control in the context of ongoing climate change and human disturbances. PMID:29813073

Evaluation of the mitochondrial system in the gonad-digestive gland complex of Biomphalaria glabrata (Mollusca, Gastropoda) after infection by Echinostoma paraensei (Trematoda, Echinostomatidae).

PubMed

Tunholi, Victor Menezes; Tunholi-Alves, Vinícius Menezes; Santos, Anderson Teixeira; Garcia, Juberlan da Silva; Maldonado, Arnaldo; da-Silva, Wagner Seixas; Rodrigues, Maria de Lurdes de Azevedo; Pinheiro, Jairo

2016-05-01

The effect of infection by Echinostoma paraensei on the mitochondrial physiology of Biomphalaria glabrata was investigated after exposure to 50 miracidia. The snails were dissected one, two, three and four weeks after infection for collection and mechanical permeabilization of the gonad-digestive gland (DGG) complex. The results obtained indicate that prepatent infection by this echinostomatid fluke significantly suppresses the phosphorylation state (respiratory state 3) and basal oxygen consumption of B. glabrata, demonstrating that the infection reduces the ability of the intermediate host to carry out aerobic oxidative reactions. Additionally, relevant variations related to the uncoupled mitochondrial (state 3u) of B. glabrata infected by E. paraensei were observed. Four weeks after exposure, a significant reduction in mitochondrial oxygen consumption after addition of ADP (3.68±0.26pmol O2/mg proteins) was observed in the infected snails in comparison with the respective control group (5.14±0.25). In the uncoupled state, the infected snails consumed about 62% less oxygen than the infected snails (7.87±0.84pmol O2/mg proteins) in the same period. These results demonstrate a reduction in oxidative decarboxylation rate of the tricarboxylic acid cycle and faster anaerobic degradation of carbohydrates in the infected snails. The possible mechanisms that explain this new metabolic condition in the infected organisms are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Angiostrongylus cantonensis and Rat Lungworm Disease in Brazil

PubMed Central

de Oliveira Simões, Raquel; Fernandez, Monica Ammon; Júnior, Arnaldo Maldonado

2013-01-01

The metastrongyloid nematode genus Angiostrongylus includes 18 species, two of which are relevant from a medical standpoint, Angiostrongylus costaricensis and Angiostrongylus cantonensis. The first was described from Costa Rica in 1971 and causes abdominal angiostrongyliasis in the Americas, including in Brazil. Angiostrongylus cantonensis, first described in 1935 from Canton, China, is the causative agent of eosinophilic meningitis. The natural definitive hosts are rodents, and molluscs are the intermediate hosts. Paratenic or carrier hosts include crabs, freshwater shrimp, amphibians, flatworms, and fish. Humans become infected accidentally by ingestion of intermediate or paratenic hosts and the parasite does not complete the life cycle as it does in rats. Worms in the brain cause eosinophilic meningitis. This zoonosis, widespread in Southeast Asia and the Pacific islands, has now been reported from other regions. In the Americas there are records from the United States, Cuba, Jamaica, Brazil, Ecuador, and Haiti. In Brazil seven human cases have been reported since 2007 from the southeastern and northeastern regions. Epidemiological studies found infected specimens of Rattus norvegicus and Rattus rattus as well as many species of molluscs, including the giant African land snail, Achatina fulica, from various regions of Brazil. The spread of angiostrongyliasis is currently a matter of concern in Brazil. PMID:23901376

Sensitivity of Oncomelania hupensis to Niclosamide: A Nation-Wide Survey in China

PubMed Central

Dai, Jianrong; Li, Youzi; Wang, Wei; Xing, Yuntian; Qu, Guoli; Liang, Yousheng

2014-01-01

Schistosomiasis japonica, transmitted by the intermediate host snail Oncomelania hupensis of the causative agent Schistosoma japonicum, remains a major public-health concern in China, and control of this snail is one of the major approaches used in attempts to interrupt the transmission of this neglected tropical disease. Niclosamide is currently the only commercial molluscicide available for the control of O. hupensis snails in China. The purpose of this study was to evaluate the current sensitivity of O. hupensis to niclosamide in China. O. hupensis snails derived from 17 sampling sites from eight schistosomiasis-endemic provinces of China were used for the molluscicidal tests. Active adult snails (10 for each drug concentration), were immersed in solutions of 1, 0.5, 0.25, 0.125, 0.063, 0.032, 0.016 and 0.008 mg/L of 50% wettable powder of niclosamide ethanolamine salt (WPN) for 24 and 48 h at 25°C, and then the snail mortality was estimated and LC50 values were calculated. All field-derived O. hupensis snails were dead following immersion in 0.5 and 1 mg/L WPN for 24 h, whereas no death was observed after immersion in 0.008 mg/L WPN for 24 h. Immersion in 0.5, 0.25, 0.125, 0.063, 0.032 and 0.016 mg/L WPN for 24 h resulted in 80%–100%, 63.33%–100%, 0%–85%, 0%–50%, 0%–15%, and 0%–5% snail mortalities, respectively. The 24 h WPN LC50 values for the O. hupensis snails derived from the 17 sampling sites in China ranged from 0.0743 to 0.2285 mg/L, and no significant difference was detected by the Kolmogorov-Smirnov test (p = 0.2). The results indicate that there is no regional variation in the current susceptibility to niclosamide in O. hupensis populations in China. It is suggested that the current sensitivity of niclosamide against O. hupensis remains high and has not changed after more than two decades of repeated, extensive application for snail control in the main endemic areas of China. PMID:24625624

Epigenetic modulation, stress and plasticity in susceptibility of the snail host, Biomphalaria glabrata, to Schistosoma mansoni infection.

PubMed

Knight, Matty; Ittiprasert, Wannaporn; Arican-Goktas, Halime D; Bridger, Joanna M

2016-06-01

Blood flukes are the causative agent of schistosomiasis - a major neglected tropical disease that remains endemic in numerous countries of the tropics and sub-tropics. During the past decade, a concerted effort has been made to control the spread of schistosomiasis, using a drug intervention program aimed at curtailing transmission. These efforts notwithstanding, schistosomiasis has re-emerged in southern Europe, raising concerns that global warming could contribute to the spread of this disease to higher latitude countries where transmission presently does not take place. Vaccines against schistosomiasis are not currently available and reducing transmission by drug intervention programs alone does not prevent reinfection in treated populations. These challenges have spurred awareness that new interventions to control schistosomiasis are needed, especially since the World Health Organization hopes to eradicate the disease by 2025. For one of the major species of human schistosomes, Schistosoma mansoni, the causative agent of hepatointestinal schistosomiasis in Africa and the Western Hemisphere, freshwater snails of the genus Biomphalaria serve as the obligate intermediate host of this parasite. To determine mechanisms that underlie parasitism by S. mansoni of Biomphalaria glabrata, which might be manipulated to block the development of intramolluscan larval stages of the parasite, we focused effort on the impact of schistosome infection on the epigenome of the snail. Results to date reveal a complex relationship, manifested by the ability of the schistosome to manipulate the snail genome, including the expression of specific genes. Notably, the parasite subverts the stress response of the host to ensure productive parasitism. Indeed, in isolates of B. glabrata native to central and South America, susceptible to infection with S. mansoni, the heat shock protein 70 (Bg-HSP70) gene of this snail is rapidly relocated in the nucleus and transcribed to express HSP70. Concurrently, hypomethylation of the CpG sites, within the Bg-HSP70 intergenic DNA region, proceeds by conveying epigenetic and spatio-epigenetic mechanisms in temporal concordance. It is notable that this is only the second example reported where a pathogen has been shown to control host cell spatio-epigenetics for its own advantage. Nonetheless, the remarkable mechanisms through which genes become activated i.e. DNA and chromatin remodeling and relocation to a nuclear compartment conducive to gene expression may represent novel intervention targets. Copyright © 2016 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Three Gorges Dam: Impact of Water Level Changes on the Density of Schistosome-Transmitting Snail Oncomelania hupensis in Dongting Lake Area, China

PubMed Central

Wu, Jin-Yi; Zhou, Yi-Biao; Chen, Yue; Liang, Song; Li, Lin-Han; Zheng, Sheng-Bang; Zhu, Shao-ping; Ren, Guang-Hui; Song, Xiu-Xia; Jiang, Qing-Wu

2015-01-01

Background Schistosomiasis remains an important public health issue in China and worldwide. Oncomelania hupensis is the unique intermediate host of schistosoma japonicum, and its change influences the distribution of S. japonica. The Three Gorges Dam (TGD) has substantially changed the ecology and environment in the Dongting Lake region. This study investigated the impact of water level and elevation on the survival and habitat of the snails. Methods Data were collected for 16 bottomlands around 4 hydrological stations, which included water, density of living snails (form the Anxiang Station for Schistosomiasis Control) and elevation (from Google Earth). Based on the elevation, sixteen bottomlands were divided into 3 groups. ARIMA models were built to predict the density of living snails in different elevation areas. Results Before closure of TGD, 7 out of 9 years had a water level beyond the warning level at least once at Anxiang hydrological station, compared with only 3 out of 10 years after closure of TGD. There were two severe droughts that happened in 2006 and 2011, with much fewer number of flooding per year compared with other study years. Overall, there was a correlation between water level changing and density of living snails variation in all the elevations areas. The density of living snails in all elevations areas was decreasing after the TGD was built. The relationship between number of flooding per year and the density of living snails was more pronounced in the medium and high elevation areas; the density of living snails kept decreasing from 2003 to 2014. In low elevation area however, the density of living snails decreased after 2003 first and turned to increase after 2011. Our ARIMA prediction models indicated that the snails would not disappear in the Dongting Lake region in the next 7 years. In the low elevation area, the density of living snails would increase slightly, and then stabilize after the year 2017. In the medium elevation region, the change of the density of living snails would be more obvious and would increase till the year 2020. In the high elevation area, the density of living snails would remain stable after the year 2015. Conclusion The TGD influenced water levels and reduced the risk of flooding and the density of living snails in the study region. Based on our prediction models, the density of living snails in all elevations tends to be stabilized. Control of S. japonica would continue to be an important task in the study area in the coming decade. PMID:26114956

Low-altitude outbreaks of human fascioliasis related with summer rainfall in Gilan province, Iran.

PubMed

Salahi-Moghaddam, Abdoreza; Habibi-Nokhandam, Majid; Fuentes, Màrius V

2011-11-01

Following human fascioliasis outbreaks in 1988 and 1999 in Gilan province, northern Iran, efforts are now made to shed light on the seasonal pattern of fascioliasis transmission in this endemic area, taking into account snail host populations, climatic conditions and human cases. Populations of the intermediate host snail (Lymnaea spp.) peak in May and November, while there is a fourfold increase in the rate of human fascioliasis in February compared to that of September. Transmission is likely to occur mainly in late autumn and sporadically in late spring. Rainfall, seasonally analysed in periods of 3 years, indicates that accumulated summer rainfall may be related with the 1988 and 1999 human fascioliasis outbreaks. Although a more detailed picture, based on the analysis of further abiotic and biotic factors influencing fascioliasis transmission in this area, is required to substantiate this hypothesis, our results serve as the first step of a geographical information system project concerning the epidemiological study of fascioliasis in Iran. This local-scale study concerning the effects of climate change and natural disasters on the spread of fascioliasis aims to facilitate the understanding of what goes on at the regional scale in this respect.

A TaqMan real-time PCR-based assay for the identification of Fasciola spp.

PubMed

Alasaad, Samer; Soriguer, Ramón C; Abu-Madi, Marawan; El Behairy, Ahmed; Jowers, Michael J; Baños, Pablo Díez; Píriz, Ana; Fickel, Joerns; Zhu, Xing-Quan

2011-06-30

Real time quantitative PCR (qPCR) is one of the key technologies of the post-genome era, with clear advantages compared to normal end-point PCR. In this paper, we report the first qPCR-based assay for the identification of Fasciola spp. Based on sequences of the second internal transcribed spacers (ITS-2) of the ribosomal rRNA gene, we used a set of genus-specific primers for Fasciola ITS-2 amplification, and we designed species-specific internal TaqMan probes to identify F. hepatica and F. gigantica, as well as the hybrid 'intermediate'Fasciola. These primers and probes were used for the highly specific, sensitive, and simple identification of Fasciola species collected from different animal host from China, Spain, Niger and Egypt. The novel qPCR-based technique for the identification of Fasciola spp. may provide a useful tool for the epidemiological investigation of Fasciola infection, including their intermediate snail hosts. Copyright © 2011 Elsevier B.V. All rights reserved.

Removal of corallivorous snails as a proactive tool for the conservation of acroporid corals

PubMed Central

Miller, Margaret W.; Bright, Allan J.; Cameron, Caitlin M.

2014-01-01

Corallivorous snail feeding is a common source of tissue loss for the threatened coral, Acropora palmata, accounting for roughly one-quarter of tissue loss in monitored study plots over seven years. In contrast with larger threats such as bleaching, disease, or storms, corallivory by Coralliophila abbreviata is one of the few direct sources of partial mortality that may be locally managed. We conducted a field experiment to explore the effectiveness and feasibility of snail removal. Long-term monitoring plots on six reefs in the upper Florida Keys were assigned to one of three removal treatments: (1) removal from A. palmata only, (2) removal from all host coral species, or (3) no-removal controls. During the initial removal in June 2011, 436 snails were removed from twelve 150 m2 plots. Snails were removed three additional times during a seven month “removal phase”, then counted at five surveys over the next 19 months to track recolonization. At the conclusion, snails were collected, measured and sexed. Before-After-Control-Impact analysis revealed that both snail abundance and feeding scar prevalence were reduced in removal treatments compared to the control, but there was no difference between removal treatments. Recolonization by snails to baseline abundance is estimated to be 3.7 years and did not differ between removal treatments. Recolonization rate was significantly correlated with baseline snail abundance. Maximum snail size decreased from 47.0 mm to 34.6 mm in the removal treatments. The effort required to remove snails from A. palmata was 30 diver minutes per 150 m2 plot, compared with 51 min to remove snails from all host corals. Since there was no additional benefit observed with removing snails from all host species, removals can be more efficiently focused on only A. palmata colonies and in areas where C. abbreviata abundance is high, to effectively conserve A. palmata in targeted areas. PMID:25469321

Experimental life history and biological characteristics of Fasciola gigantica (Digenea: Fasciolidae).

PubMed

Phalee, Anawat; Wongsawad, Chalobol; Rojanapaibul, Amnat; Chai, Jong-Yil

2015-02-01

This study was conducted to investigate the life history, morphology, and maturation of larval stages and adult worms of Fasciola gigantica in experimental mice. Lymnaea auricularia rubiginosa was used as the intermediate host, and Oryza sativa was used for encystment of the metacercariae, while Mus musculus was used as the definitive host for maturation study. Fresh eggs from the gall bladder of water buffaloes fully developed into embryonated ones and hatched out at days 11-12 after incubation at about 29ºC. Free-swimming miracidia rapidly penetrated into the snail host, and gradually developed into the next larval stages; sporocyst, redia, and daughter redia with cercariae. Fully-developed cercariae were separated from the redia and shed from the snails on day 39 post-infection (PI). Free-swimming cercariae were immediately allowed to adhere to rice plants, and capsules were constructed to protect metacercariae on rice plants. Juvenile worms were detected in intestines of mice at days 3 and 6 PI, but they were found in the bile duct from day 9 PI. Juvenile and adult flukes were recovered from 16 mice experimentally infected with metacercariae, with the average recovery rate of 35.8%. Sexually mature adult flukes were recovered from day 42 PI. It could be confirmed that experimentally encysted metacercariae could infect and develop to maturity in the experimental host. The present study reports for the first time the complete life history of F. gigantica by an experimental study in Thailand. The obtained information can be used as a guide for prevention, elimination, and treatment of F. gigantica at environment and in other hosts.

Experimental Life History and Biological Characteristics of Fasciola gigantica (Digenea: Fasciolidae)

PubMed Central

Phalee, Anawat; Wongsawad, Chalobol; Rojanapaibul, Amnat; Chai, Jong-Yil

2015-01-01

This study was conducted to investigate the life history, morphology, and maturation of larval stages and adult worms of Fasciola gigantica in experimental mice. Lymnaea auricularia rubiginosa was used as the intermediate host, and Oryza sativa was used for encystment of the metacercariae, while Mus musculus was used as the definitive host for maturation study. Fresh eggs from the gall bladder of water buffaloes fully developed into embryonated ones and hatched out at days 11-12 after incubation at about 29ºC. Free-swimming miracidia rapidly penetrated into the snail host, and gradually developed into the next larval stages; sporocyst, redia, and daughter redia with cercariae. Fully-developed cercariae were separated from the redia and shed from the snails on day 39 post-infection (PI). Free-swimming cercariae were immediately allowed to adhere to rice plants, and capsules were constructed to protect metacercariae on rice plants. Juvenile worms were detected in intestines of mice at days 3 and 6 PI, but they were found in the bile duct from day 9 PI. Juvenile and adult flukes were recovered from 16 mice experimentally infected with metacercariae, with the average recovery rate of 35.8%. Sexually mature adult flukes were recovered from day 42 PI. It could be confirmed that experimentally encysted metacercariae could infect and develop to maturity in the experimental host. The present study reports for the first time the complete life history of F. gigantica by an experimental study in Thailand. The obtained information can be used as a guide for prevention, elimination, and treatment of F. gigantica at environment and in other hosts. PMID:25748710

Spatio-temporal modeling with GIS and remote sensing for schistosomiasis control in Sichuan, China

NASA Astrophysics Data System (ADS)

Xu, Bing

Schistosomiasis is a water-borne parasitic disease endemic in tropical and subtropical areas. Its transmission requires certain kind of snail as the intermediate host. Some efforts have been made to mapping snail habitats with remote sensing and schistosomiasis transmission modeling. However, the modeling is limited to isolated residential groups and does not include spatial interaction among those groups. Remotely sensed data are only used in snail habitat classification, not in estimation of snail abundance that is an important parameter in schistosomiasis transmission modeling. This research overcomes the above two problems using innovative geographic information system (GIS) and remote sensing technology. A mountainous environment near Xichang, China, is chosen as the test site. Environmental and epidemiological data are stored in a GIS to support modeling. Snail abundance is estimated from land-cover and land-use fractions derived from high spatial resolution IKONOS satellite data. Spatial interaction is determined in consideration of neighborhoods, group areas, relative slopes among groups, and natural barriers. Land-cover and land-use information extracted from 4 m high resolution IKONOS data is used as reference in scaling up to the regional level. The scale-up is done with coarser resolution satellite data including Landsat Thematic Mapper (TM), EO-1 Advanced Land Imager (ALI) and Hyperion data all at 30 m resolution. Snail abundance is estimated by regressing snail survey data with land-cover and land-use fractions. An R2 of 0.87 is obtained between the average snail density predicted and that surveyed at the group level. With such a model, a snail density map is generated for all residential groups in the study area. A spatio-temporal model of schistosomiasis transmission is finally built to incorporate the spatial interaction caused by miracidia and cercaria migration. Comparing the model results with and without spatial interaction has revealed a number of advantages of the spatio-temporal model. Particularly, with the inclusion of spatial interaction, more effective control of schistosomiasis transmission over the whole study area can be achieved.

Effects of Coralliophila violacea on tissue loss in the scleractinian corals Porites spp. depend on host response

USGS Publications Warehouse

Raymundo, L.; Work, Thierry M.; Miller, R.L.; Lozada-Misa, P.L.

2016-01-01

We investigated interactions between the corallivorous gastropod Coralliophila violacea and its preferred hosts Porites spp. Our objectives were to experimentally determine whether tissue loss could progress in Porites during or after Coralliophila predation on corals with and without tissue loss and to histologically document snail predation. In 64% of feeding scars, tissue regenerated within 3 wk, leaving no trace of predation. However, in roughly 28% of scars, lesions progressed to subacute tissue loss resembling white syndrome. In feeding experiments, scars from snails previously fed diseased tissue developed progressive tissue loss twice as frequently as scars from snails previously fed healthy tissue. Scars from previously healthy-fed snails were 3 times as likely to heal as those from previously diseased-fed snails. Histology revealed marked differences in host responses to snails; P. cylindrica manifested a robust inflammatory response with fewer secondary colonizing organisms such as algae, sponges, and helminths, whereas P. rus showed no evident inflammation and more secondary colonization. We conclude that lesion progression associated with Coralliophila may be associated with secondary colonization of coral tissues damaged by predator-induced trauma and necrosis. Importantly, variation at the cellular level should be considered when explaining interspecific differences in host responses in corals impacted by phenomena such as predation.

Angiostrongylus cantonensis in the vector snails Pomacea canaliculata and Achatina fulica in China: a meta-analysis.

PubMed

Song, Langui; Wang, Xiaowen; Yang, Zi; Lv, Zhiyue; Wu, Zhongdao

2016-03-01

Angiostrongyliasis is a food-borne parasitic disease induced by the nematode Angiostrongylus cantonensis, and has been recognized as the main cause leading to human eosinophilic meningitis. Humans usually acquire infection by digestion of infected Pomacea canaliculata and Achatina fulica, the most predominant intermediate hosts found in China. This meta-analysis was aimed to assess the prevalence of A. cantonensis infection among these two snails in China in the past 10 years. Data were systematically collected in electronic databases such as PubMed, Web of Science, ScienceDirect, CNKI, SinoMed, VIP, CSCD, and Wanfang from 2005 to 2015. Thirty-eight studies with a total of 41,299 P. canaliculata and 21,138 Ac. fulica were included in the present study. The overall infection rate of A. cantonensis in China was estimated to be 7.6 % (95 % confidential interval (CI) = 0.063 to 0.090) in P. canaliculata and 21.5 % in Ac. fulica (95 % CI = 0.184 to 0.245), respectively. No significant difference was observed in prevalence rates among publication year and sample size for both snails. Also, it was found that the prevalence in Ac. fulica is significantly higher than that in P. canaliculata (odds ratio (OR) = 3.946, 95 % CI = 3.070 to 5.073). The present study reveals that snail infection with A. cantonensis is clearly prevalent in China. Further studies are required to improve strategies for control of infections of snails, particularly those of Ac. fulica, and to detect further factors and conditions such as geographic region, temperatures, and diagnosis method.

Biology of Crassicutis cichlasomae, a parasite of cichlid fishes in Mexico and Central America.

PubMed

Scholz, T; Pech-Ek, M C; Rodriguez-Canul, R

1995-03-01

Field study on the biology of Crassicutis cichlasomae Manter, 1936 (Digenea: Homalometridae) was carried out in a small swamp in a limestone factory near Mérida, Yucatán, Mexico. Aquatic snails, Littorina (Littoridinopis) angulifera, harbouring C. cichlasomae rediae, cercariae and metacercariae, served both as the first and second intermediate hosts. Feeding experiments confirmed the conspecificity of metacercariae from naturally infected snails with adults from naturally infected fish. Gravid C. cichlasomae worms were obtained from experimentally infected fish 19 days post exposure at 22-24 degrees C. Examination of fish from the swamp in Mitza and other localities in the Yucatan Peninsula showed that the cichlids Cichlasoma urophthalmus and C. meeki were definitive hosts of C. cichlasomae. There was no pronounced preference of C. cichlasomae adults for the site of their location in the intestine of the definitive host; a slightly higher proportion (41%) of worms was only found in the anterior third of the gut. The time of miracidium development varied from 18.5 to 27.5 days; different temperature (20.1-35.7 degrees C) or light/darkness regimes influenced only slightly the rate of embryonic development, with shorter development times at higher temperature (34.8-35.7 degrees C) and constant darkness and/or light. With the exception of the sporocyst, all developmental stages are described and figured.

First Record of Transversotrema Witenberg, 1944 (Digenea) from the Americas, with Comments on the Taxonomy of Transversotrema patialense (Soparkar, 1924) Crusz and Sathananthan, 1960, and an Updated List of Its Hosts and Geographic Distribution.

PubMed

Womble, Matthew R; Cox-Gardiner, Stephanie J; Cribb, Thomas H; Bullard, Stephen A

2015-12-01

Specimens of Transversotrema patialense (sensu lato) ( Soparkar, 1924 ) Crusz and Sathananthan, 1960 (Digenea: Transversotrematidae) infected the skin (epidermal spaces beneath scales near pectoral fins) of 4 of 126 (prevalence 3%; mean intensity 1.8) zebrafish ( Danio rerio (Hamilton, 1822) [Cypriniformes: Cyprinidae]) purchased in 2009 and cultured by a California (USA) fish supplier. These fish were sold as "laboratory-reared" and "specific pathogen free," purportedly raised in a recirculating aquaculture system that included zebrafish only. We herein describe the morphological features of this transversotrematid using light and scanning electron microscopy, provide a comprehensive list of hosts (snails and fishes) and geographic locality records for specimens reported as T. patialense, which is perhaps a species complex, and provide a brief historical synopsis of the taxonomic and life history research that has been conducted on this fluke. No species of Transversotrema previously had been reported from the Americas; however, this discovery is not surprising given that: (1) a suitable intermediate host (red-rimmed melania, Melanoides tuberculata (Müller, 1774) [Cerithioidea: Thiaridae]) has been established in California and elsewhere in North America, (2) the zebrafish is a susceptible definitive host, and (3) T. patialense reportedly matures on a broad ecological and phylogenetic spectrum of freshwater fishes. To our knowledge, this is the northern-most geographic locality record for a species of this genus. We suspect this case study represents an example of a parasite that may now be established in North America by the fortuitous co-occurrence of a susceptible, exotic snail host (the red-rimmed melania) and a susceptible, widely distributed, exotic fish host (the zebrafish).

Malacological survey of Biomphalaria snails in municipalities along the Estrada Real in the southeast of the State of Minas Gerais, Brazil.

PubMed

Tibiriçá, Sandra Helena Cerrato; Mitterofhe, Adalberto; Castro, Milton Ferreira de; Lima, Adilson da Costa; Gonçalves, Murilo; Pinheiro, Izabella de Oliveira; Freitas, Corina da Costa; Guimarães, Ricardo José Paula de Souza e; Carvalho, Omar dos Santos; Coimbra, Elaine Soares

2011-01-01

The increasing practice of ecotourism and rural tourism in the State of Minas Gerais, Brazil, highlights the importance of studies concerning the occurrence of potential intermediate hosts of Schistosoma mansoni. This study aimed to identify species of Biomphalaria snails in municipalities along the Estrada Real, an important Brazilian tourism project. The specimens were collected in different water collections of 36 municipalities along the Estrada Real in the southeast of the State of Minas Gerais. Biomphalaria species were characterized using both morphological and molecular approaches. The research was conducted between August 2005 and September 2009 and all the sites visited were georeferenced using GPS. Six Biomphalaria species were found in 30 of the 36 municipalities studied: glabrata, tenagophila, straminea, peregrina, occidentalis and schrammi. The first three species of Biomphalaria, recognized as intermediate hosts of S. mansoni, were present in 33.3%, 47.2% and 8.3% of the municipalities studied, respectively. The mollusks were found in different types of water collections and no infection by S. mansoni was detected. The highest occurrence of Biomphalaria concentration was verified in the area covered by the Caminho Novo route (Diamantina/MG to Rio de Janeiro/RJ). Considering the occurrence of schistosomiasis in the State of Minas Gerais and the socioeconomic repercussions involved in the Estrada Real Project, this work focuses on the vulnerability of water collections due to the presence of Biomphalaria mollusks and emphasizes the need for epidemiological surveillance and sanitary and educational measures integrated with the local community and tourism sectors.

Breeding system and demography shape population genetic structure across ecological and climatic zones in the African freshwater snail, Bulinus forskalii (Gastropoda, Pulmonata), intermediate host for schistosomes.

PubMed

Gow, J L; Noble, L R; Rollinson, D; Mimpfoundi, R; Jones, C S

2004-11-01

The role of breeding system and population bottlenecks in shaping the distribution of neutral genetic variation among populations inhabiting patchily distributed, ephemeral water bodies was examined for the hermaphroditic freshwater snail Bulinus forskalii, intermediate host for the medically important trematode Schistosoma guineensis. Levels of genetic variation at 11 microsatellite loci were assessed for 600 individuals sampled from 19 populations that span three ecological and climatic zones (ecozones) in Cameroon, West Africa. Significant heterozygote deficiencies and linkage disequilibria indicated very high selfing rates in these populations. Despite this and the large genetic differentiation detected between populations, high levels of genetic variation were harboured within these populations. The high level of gene flow inferred from assignment tests may be responsible for this pattern. Indeed, metapopulation dynamics, including high levels of gene flow as well as extinction/contraction and recolonization events, are invoked to account for the observed population structuring, which was not a consequence of isolation-by-distance. Because B. forskalii populations inhabiting the northern, Sahelian area are subject to more pronounced annual cycles of drought and flood than the southern equatorial ones, they were expected to be subject to population bottlenecks of increased frequency and severity and, therefore, show reduced genetic variability and elevated population differentiation. Contrary to predictions, the populations inhabiting the most northerly ecozone exhibited higher genetic diversity and lower genetic differentiation than those in the most southerly one, suggesting that elevated gene flow in this region is counteracting genetic drift.

Endogenous growth factor stimulation of hemocyte proliferation induces resistance to Schistosoma mansoni challenge in the snail host.

PubMed

Pila, Emmanuel A; Gordy, Michelle A; Phillips, Valerie K; Kabore, Alethe L; Rudko, Sydney P; Hanington, Patrick C

2016-05-10

Digenean trematodes are a large, complex group of parasitic flatworms that infect an incredible diversity of organisms, including humans. Larval development of most digeneans takes place within a snail (Gastropoda). Compatibility between snails and digeneans is often very specific, such that suitable snail hosts define the geographical ranges of diseases caused by these worms. The immune cells (hemocytes) of a snail are sentinels that act as a crucial barrier to infection by larval digeneans. Hemocytes coordinate a robust and specific immunological response, participating directly in parasite killing by encapsulating and clearing the infection. Hemocyte proliferation and differentiation are influenced by unknown digenean-specific exogenous factors. However, we know nothing about the endogenous control of hemocyte development in any gastropod model. Here, we identify and functionally characterize a progranulin [Biomphalaria glabrata granulin (BgGRN)] from the snail B. glabrata, a natural host for the human blood fluke Schistosoma mansoni Granulins are growth factors that drive proliferation of immune cells in organisms, spanning the animal kingdom. We demonstrate that BgGRN induces proliferation of B. glabrata hemocytes, and specifically drives the production of an adherent hemocyte subset that participates centrally in the anti-digenean defense response. Additionally, we demonstrate that susceptible B. glabrata snails can be made resistant to infection with S. mansoni by first inducing hemocyte proliferation with BgGRN. This marks the functional characterization of an endogenous growth factor of a gastropod mollusc, and provides direct evidence of gain of resistance in a snail-digenean infection model using a defined factor to induce snail resistance to infection.

The ecology of Australorbis glabratus in Puerto Rico

PubMed Central

Harry, Harold W.; Aldrich, David V.

1958-01-01

Variations in the distribution of the water-snail Australorbis glabratus, intermediate host of Schistosoma mansoni, have been studied in Puerto Rico, and an attempt made to correlate the distribution with environmental factors. The main sources of bilharziasis infection are flowing waters, but the evidence indicates that the snail is not found in fast-flowing, high-gradient reaches with falls of more than 20 meters per kilometre. The influence of physiographical features on stream gradient is examined and these findings correlated with the biota, water chemistry and human use of the stream. The alluvial areas of the island have many habitats favourable to A. glabratus and constitute the major foci for the transmission of bilharziasis. In general, artificial reservoirs and puddles do not appear to be suitable habitats for the snail. The numerous sink ponds in the Tertiary limestone area on the north coast contain the snail, yet the area is relatively free from bilharziasis, possibly because the ponds are little used. Although the size of A. glabratus populations is limited by many natural enemies, no organism has been found which could be deemed useful for artificial control. Some migratory birds, insects and amphibians may aid the dispersal of the snail. There are indications that the ionic composition of the water may be an important factor in limiting the distribution of A. glabratus. It is suggested that large amounts of carbonates and bicarbonates relative to the amounts of chlorides and sulfates may account for the absence of the snail from some habitats (e.g., limestone streams) and that copper and zinc may be limiting agents in some waters containing small amounts of dissolved solids. Concentrations of 0.050-0.100 p.p.m. of zinc, copper, cadmium or silver in distilled water produce a distress syndrome in the snails, and concentrations of more than 1.0 p.p.m. are rapidly fatal in most cases. PMID:13573114

Distribution of freshwater snails in family-based VAC ponds and associated waterbodies with special reference to intermediate hosts of fish-borne zoonotic trematodes in Nam Dinh Province, Vietnam.

PubMed

Dung, Bui Thi; Madsen, Henry; The, Dang Tat

2010-10-01

Fish-borne zoonotic trematodes, such as Clonorchis sinensis, heterophyids and others, constitute a public health concern in parts of northern Vietnam and infections with these trematodes are often thought to be linked to fish culture. One common fish culture system is the integrated fish-livestock (VAC) ponds where individual households have 1 or more ponds. Fish fry, mainly of various carp species, produced in hatcheries, not necessarily local, are introduced into nursery ponds and after approximately 6 weeks, juvenile fishes are transferred to household ponds, referred to as grow-out ponds. Grow-out ponds are usually fertilized with organic debris, including animal excreta, to stimulate algal growth and subsequently fish growth. This paper describes the distribution of freshwater snails and occurrence of trematode infections in these in VAC ponds and associated habitats as part of a major study on risk factors of FZT infections in cultured fish in two communes, Nghia Lac and Nghia Phu, Nghia Hung District, Nam Dinh Province. The area is under intense rice cultivation with an extensive canal network supplying fields and also household VAC ponds. A total of 16 snail species was found and four were widely distributed i.e. Angulyagra polyzonata, Melanoides tuberculata, Bithynia fuchsiana and Pomacea insularum. Snail diversity and counts were higher in nursery ponds than in grow-out ponds. Species of the families Thiaridae and Viviparidae were more abundant than other species in VAC ponds while species of the Bithyniidae, Stenothyridae and Planorbidae dominated in rice fields and small canals. Trematode infections were found in eight snail species and among these M. tuberculata had the highest overall prevalence of infection (13.28%). No trematode infections were found in species of the Viviparidae and Ampullaridae except for metacercariae. Parapleurolophocercous and pleurolophocercous cercariae constituted the most common type of cercariae recovered, contributing 40.6% of all infections followed by echinostome cercariae (35.0%) and xiphidiocercariae (17.3%). Bithynia fuschiana and M. tuberculata had the most diverse trematode fauna. C. sinensis was not recorded in this study. The VAC pond system in this area, is very important for transmission of minute intestinal trematodes while they play little role in transmission of C. sinensis as its intermediate hosts, bithynid snails, rarely occur in these ponds. From a public health perspective this is positive as the effects of infections with intestinal trematodes are considered mild. On the other hand it is possible that even such subtle effects could have importance in public health as transmission is very intense in the area. And this in combination with the aquaculture importance, reduced marketability of fishes with high metacercariae loads, warrants that control efforts against these trematodes are initiated to reduce transmission in this production system. Copyright 2010 Elsevier B.V. All rights reserved.

Introduced cryptic species of parasites exhibit different invasion pathways.

PubMed

Miura, Osamu; Torchin, Mark E; Kuris, Armand M; Hechinger, Ryan F; Chiba, Satoshi

2006-12-26

Sometimes infectious agents invade and become established in new geographic regions. Others may be introduced yet never become established because of the absence of suitable hosts in the new region. This phenomenon may be particularly true for the many parasites with complex life cycles, where various life stages require different host species. Homogenization of the world's biota through human-mediated invasions may reunite hosts and parasites, resulting in disease outbreaks in novel regions. Here we use molecular genetics to differentiate invasion pathways for two digenean trematode parasites and their exotic host, the Asian mud snail, Batillaria attramentaria. All of the snail haplotypes found in introduced populations in North America were identical to haplotypes common in the areas of Japan that provided oysters for cultivation in North America, supporting the hypothesis that the snails were introduced from Japan with seed oysters. Two cryptic trematode species were introduced to North American populations in high frequencies. We found a marked reduction of genetic variation in one of these species, suggesting it experienced a bottleneck or founder event comparable to that of the host snail. In contrast, no genetic variation was lost in the other parasite species. We hypothesize that this parasite was and is dispersed naturally by migratory shorebirds and was able to establish only after the host snail, B. attramentaria, was introduced to North America. Evaluation of the nature of invasion pathways and postinvasion consequences will aid mitigation of spreading diseases of humans, livestock, and wildlife in an increasingly globalized world.

Stephanoprora chasanensis n. sp. (Digenea: Echinochasmidae): Morphology, life cycle, and molecular data.

PubMed

Besprozvannykh, Vladimir V; Rozhkovan, Konstantin V; Ermolenko, Alexey V

2017-02-01

Echinostomatoidea is a large, globally distributed and heterogeneous group of hermaphroditic digeneans that parasite, as adults, vertebrate hosts of all classes. Species of this group have received attention from researchers as they can cause diseases in wildlife and humans. Here we describe the biological and molecular phylogenetic characteristics of Stephanoprora chasanensis n. sp. (Digenea: Echinochasmidae). The life cycle of this fluke was experimentally completed by the use of hosts, i.e. Stenothyra recondite Lindholm, 1929 snail (the 1st intermediate), Rhynchocypris percnurus mantschuricus (Berg, 1907) freshwater fish (the 2nd intermediate) and Gallus gallus chicken (the definitive host). In the adult worms, vitelline follicles were distributed anteriorly to the mid-level of the ventral sucker in our specimens whereas they did not reach the level of anterior testis in other species of Stephanoprora previously reported. Phylogenetic analysis based on 28S rDNA revealed that Stephanoprora and Echinochasmus with 20-22 collar spines grouped together in a single cluster. In addition, we showed that Stephanoprora chasanensis n. sp. was closely related to Echinochasmus milvi Yamaguti, 1939. Cercariae of these two echinostomes commonly have a long tail. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Investigation on the endemic characteristics of Metorchis orientalisin Huainan area, China

PubMed

Zhan, Xiaodong; Li, Chaopin; Wu, Hua; Sun, Entao; Zhu, Yuxia

2017-06-05

To investigate the endemic characteristics of Metorchis orientalis (M. orientalis)in the Huainan area, Anhui province, China. The first-intermediate host, second-intermediate host and reservoir hosts were collected, and the endemic characteristics of M. orientalis were examined through field investigation and artificial infection. Investigation was completed in 89 domestic ducks, 156 domestic chicken, 41 domestic geese, 20 domestic cats and 19 dogs. The infection rate of M. orientaliswas 18.0% (16/89) in ducks, 12.2% (19/156) in chicken, 9. 8% (4/41) in geese, 5.0% (1/20) in cats and 5.3% (1/19) in dogs. Sixty-seven cercariae of M. orientaliswere identified in 1,000 Parafossarulu s striatulus,with a natural infection rate of 6.7%, and 19 cercariae occurred in 300 Pseudorasbora parva, with a natural infection rate of 6.33%. The activity of the cercariae of M. orientaliswas associated with light intensity and temperature. The full life cycle of M. orientalisranged from 120 to 140 days; it occurred approximately in 89 days in snails, 28 days in fish and 20 days in ducks. M. orientalisis prevalent in the Huainan area, and it may complete its life cycle in Parafossarulus striatulus, Pseudorasbora parva and natively rais ed ducks.

Increased surfacing behavior in longnose killifish infected by brain-encysting trematode.

PubMed

Fredensborg, B L; Longoria, A N

2012-10-01

Some parasites modify the behavior of intermediate hosts to increase the probability of transmission to the next host in their life cycle. In habitats where this is common, parasites play an important role in predator-prey links and food web dynamics. In this study we used laboratory observations to investigate the behavior of longnose killifish, Fundulus similis, that were naturally infected with metacercariae of the trematode, Euhaplorchis sp. A, from Laguna Madre, south Texas. In particular, we examined whether there was a relationship between the number of metacercariae lodged on the brain of the infected fish and behaviors that made the fish more conspicuous to avian final hosts. We also quantified the abundance and cercariae production of this parasite in its first intermediate snail host, Cerithidea pliculosa , and examined the seasonal variation of Euhaplorchis sp. A in F. similis . Our data demonstrated that Euhaplorchis sp. A affected the surfacing behavior of F. similis in an intensity-dependent manner. Fish with many infections spent longer time at the surface of the water than fish with few infections. Our data also show that Euhaplorchis sp. A is a common parasite in the first intermediate host and produces close to 4,000 cercariae m(-2) day(-1). Consequently 97% of all fish collected and necropsied were infected, with little seasonal variation in the mean abundance of the parasite. Based on our data, Euhaplorchis sp. A is likely important to predator-prey links in Gulf of Mexico estuary food webs, similar to the closely related Euhaplorchis californiensis in southern California. We expect that other closely related species elsewhere may have similar effects on other fish hosts, emphasizing the need for incorporating trophically transmitted parasites in estuarine food web studies.

Biology, systematics, life cycle, and distribution of Angiostrongylus cantonensis, the cause of rat lungworm disease.

PubMed

Cowie, Robert H

2013-06-01

Angiostrongylus cantonensis is a metastrongyloid nematode in the family Angiostrongylidae. It is the cause of angiostrongyliasis (rat lungworm disease), which manifests as eosinophilic meningitis. First described in 1935 from rats in China, A. cantonensis was placed in the genus Parastrongylus in 1986, but most workers have not adopted this treatment. The taxonomy of A. cantonensis and related worms is largely based on adult morphology, notably of the male bursa. However, identification of infective third stage larvae is more difficult. The natural life cycle involves rats as the definitive host and snails or slugs as the intermediate host. Human infection, as accidental hosts, results in worms maturing in the brain, but dying there instead of moving back into the bloodstream, as in rats, thereby leading to eosinophilic meningitis. The disease is an emerging infectious disease; Angiostrongylus cantonensis continues to be reported in new regions beyond its native range.

Effects of Endosulfan on Predator-Prey Interactions Between Catfish and Schistosoma Host Snails.

PubMed

Monde, Concillia; Syampungani, Stephen; Van den Brink, Paul J

2016-08-01

The effect of the pesticide endosulfan on predator-prey interactions between catfish and Schistosoma host snails was assessed in static tank experiments. Hybrid catfish (Clarias gariepinus × C. ngamensis) and Bulinus globosus were subjected to various endosulfan concentrations including an untreated control. The 48- and 96-h LC50 values for catfish were 1.0 and <0.5 µg/L, respectively, whereas the 48- and 96-h LC50 values for snails were 1137 and 810 µg/L. To assess sublethal effects on the feeding of the catfish on B. globosus, endosulfan concentrations between 0.03 and 1.0 µg/L were used. Predation was significantly greater (p < 0.001) in control tanks than in all other treatments. There was progressively decreasing predation with increasing toxicant concentration. Biological control of Schistosoma host snails using fish may be affected in endosulfan-polluted aquatic systems of Southern Africa because it has been found present at concentrations that are indicated to cause lethal effects on the evaluated hybrid catfish and to inhibit the predation of snails by this hybrid catfish.

Host ploidy, parasitism and immune defence in a coevolutionary snail-trematode system.

PubMed

Osnas, E E; Lively, C M

2006-01-01

We studied the role of host ploidy and parasite exposure on immune defence allocation in a snail-trematode system (Potamopyrgus antipodarum-Microphallus sp.). In the field, haemocyte (the defence cell) concentration was lowest in deep-water habitats where infection is relatively low and highest in shallow-water habitats where infection is common. Because the frequency of asexual triploid snails is positively correlated with depth, we also experimentally studied the role of ploidy by exposing both diploid sexual and triploid asexual snails to Microphallus eggs. We found that triploid snails had lower haemocyte concentrations than did diploids in both parasite-addition and parasite-free treatments. We also found that both triploids and diploids increased their numbers of large granular haemocytes at similar rates after parasite exposure. Because triploid P. antipodarum have been shown to be more resistant to allopatric parasites than diploids, the current results suggest that the increased resistance of triploids is because of intrinsic genetic properties rather than to greater allocation to defence cells. This finding is consistent with recent theory on the advantages of increased ploidy for hosts combating coevolving parasites.

Parasites reduce food web robustness because they are sensitive to secondary extinction as illustrated by an invasive estuarine snail

USGS Publications Warehouse

Lafferty, Kevin D.; Kuris, Armand M.

2009-01-01

A robust food web is one in which few secondary extinctions occur after removing species. We investigated how parasites affected the robustness of the Carpinteria Salt Marsh food web by conducting random species removals and a hypothetical, but plausible, species invasion. Parasites were much more likely than free-living species to suffer secondary extinctions following the removal of a free-living species from the food web. For this reason, the food web was less robust with the inclusion of parasites. Removal of the horn snail, Cerithidea californica, resulted in a disproportionate number of secondary parasite extinctions. The exotic Japanese mud snail, Batillaria attramentaria, is the ecological analogue of the native California horn snail and can completely replace it following invasion. Owing to the similarities between the two snail species, the invasion had no effect on predator–prey interactions. However, because the native snail is host for 17 host-specific parasites, and the invader is host to only one, comparison of a food web that includes parasites showed significant effects of invasion on the native community. The hypothetical invasion also significantly reduced the connectance of the web because the loss of 17 native trematode species eliminated many links.

Road facilitation of trematode infections in snails of northern Alaska.

PubMed

Urban, Mark C

2006-08-01

Road disturbances can influence wildlife health by spreading disease agents and hosts or by generating environmental conditions that sustain these agent and host populations. I evaluated field patterns of trematode infections in snails inhabiting ponds at varying distances from the Dalton Highway, a wilderness road that intersects northern Alaska. I also assessed the relationships between trematode infections and snail densities and six environmental variables: calcium concentration, aquatic vegetative cover canopy cover temperature, pond size, and community structure. Presence of trematode infections and snail density were negatively correlated with distance from the highway. Of the pond characteristics measured, only calcium concentration and vegetation density declined with distance from road. However neither variable was positively associated with snail density or trematode presence. One potential explanation for observed patterns is that vehicles, road maintenance, or vertebrate vectors attracted to the highway facilitate colonization of snails or trematodes. Emerging disease threats to biological diversity in northern ecosystems highlight the importance of understanding how roads affect disease transmission.

Genetic sequence data identifies the cercaria of Drepanocephalus spathans (Digenea: Echinostomatidae), a parasite of the double-crested cormorant (Phalacrocorax auritus), with notes on its pathology in juvenile channel catfish (Ictalurus punctatus).

PubMed

Griffin, Matt J; Khoo, Lester H; Quiniou, Sylvie M; O'Hear, Mary M; Pote, Linda M; Greenway, Terrence E; Wise, David J

2012-10-01

An unidentified xiphidio-type cercaria, previously thought inconsequential to catfish health, was found to be released from marsh rams-horn snails (Planorbella trivolvis) inhabiting ponds on a commercial catfish operation in the Mississippi Delta. A preliminary challenge of cohabiting channel catfish ( Ictalurus punctatus ) with snails actively shedding the unidentified cercariae resulted in death of some fish. A second cohabitation trial yielded similar results, as did a third challenge of 250 cercariae/fish. Histopathology revealed developing metacercariae concentrated in the cranial region, especially within the branchial chamber, with several metacercariae at the base of the branchial arches within, or adjacent to, blood vessels, possibly the proximate cause of death. Genetic sequence analysis of the 18S small subunit ribosomal DNA (ssDNA), 28S large subunit rDNA (lsDNA), and cytochrome oxidase (Cox1) genes all matched the cercariae to Drepanocephalus spathans (Digenea: Echinostomatidae), a parasite of the double-crested cormorant (Phalacrocorax auritus), a piscivorous bird endemic on most catfish farms. This is the first commentary regarding pathology of D. spathans in juvenile channel catfish as well as the first report of the marsh rams-horn snail as an intermediate host in the D. spathans life cycle. The data presented here suggest this parasite could have limiting effects on catfish production, further supporting the need for adequate snail control programs to reduce trematode prevalence on commercial catfish operations.

Molluscicidal and ovicidal activities of plant extracts of the Piperaceae on Biomphalaria glabrata (Say, 1818).

PubMed

Rapado, L N; Nakano, E; Ohlweiler, F P; Kato, M J; Yamaguchi, L F; Pereira, C A B; Kawano, T

2011-03-01

Schistosomiasis is a tropical disease caused by Schistosoma and occurs in 54 countries, mainly in South America, the Caribbean region, Africa and the eastern Mediterranean. Currently, 5 to 6 million Brazilian people are infected and 30,000 are under infection risk. Typical of poor regions, this disease is associated with the lack of basic sanitation and very frequently to the use of contaminated water in agriculture, housework and leisure. One of the most efficient methods of controlling the disease is application of molluscicides to eliminate or to reduce the population of the intermediate host snail Biomphalaria glabrata. Studies on molluscicidal activity of plant extracts have been stimulated by issues such as environmental preservation, high cost and recurrent resistance of snails to synthetic molluscicides. The aim of this study was to determine the molluscicide action of extracts from Piperaceae species on adult and embryonic stages of B. glabrata. Fifteen extracts from 13 Piperaceae species were obtained from stems, leaves and roots. Toxicity of extracts was evaluated against snails at two different concentrations (500 and 100 ppm) and those causing 100% mortality at 100 ppm concentration were selected to obtain the LC₉₀ (lethal concentration of 90% mortality). Piper aduncum, P. crassinervium, P. cuyabanum, P. diospyrifolium and P. hostmannianum gave 100% mortality of adult snails at concentrations ranging from 10 to 60 ppm. These extracts were also assayed on embryonic stages of B. glabrata and those from P. cuyabanum and P. hostmannianum showed 100% ovicidal action at 20 ppm.

Reversing the Resistance Phenotype of the Biomphalaria glabrata Snail Host Schistosoma mansoni Infection by Temperature Modulation

PubMed Central

Ittiprasert, Wannaporn; Knight, Matty

2012-01-01

Biomphalaria glabrata snails that display either resistant or susceptible phenotypes to the parasitic trematode, Schistosoma mansoni provide an invaluable resource towards elucidating the molecular basis of the snail-host/schistosome relationship. Previously, we showed that induction of stress genes either after heat-shock or parasite infection was a major feature distinguishing juvenile susceptible snails from their resistant counterparts. In order to examine this apparent association between heat stress and snail susceptibility, we investigated the effect of temperature modulation in the resistant snail stock, BS-90. Here, we show that, incubated for up to 4 hrs at 32°C prior to infection, these resistant snails became susceptible to infection, i.e. shedding cercariae at 5 weeks post exposure (PE) while unstressed resistant snails, as expected, remained resistant. This suggests that susceptibility to infection by this resistant snail phenotype is temperature-sensitive (ts). Additionally, resistant snails treated with the Hsp 90 specific inhibitor, geldanamycin (GA) after heat stress, were no longer susceptible to infection, retaining their resistant phenotype. Consistently, susceptible snail phenotypes treated with 100 mM GA before parasite exposure also remained uninfected. These results provide direct evidence for the induction of stress genes (heat shock proteins; Hsp 70, Hsp 90 and the reverse transcriptase [RT] domain of the nimbus non-LTR retrotransposon) in B. glabrata susceptibility to S. mansoni infection and characterize the resistant BS-90 snails as a temperature-sensitive phenotype. This study of reversing snail susceptibility phenotypes to S. mansoni provides an opportunity to directly track molecular pathway(s) that underlie the B. glabrata snail's ability to either sustain or destroy the S. mansoni parasite. PMID:22577362

Reversing the resistance phenotype of the Biomphalaria glabrata snail host Schistosoma mansoni infection by temperature modulation.

PubMed

Ittiprasert, Wannaporn; Knight, Matty

2012-01-01

Biomphalaria glabrata snails that display either resistant or susceptible phenotypes to the parasitic trematode, Schistosoma mansoni provide an invaluable resource towards elucidating the molecular basis of the snail-host/schistosome relationship. Previously, we showed that induction of stress genes either after heat-shock or parasite infection was a major feature distinguishing juvenile susceptible snails from their resistant counterparts. In order to examine this apparent association between heat stress and snail susceptibility, we investigated the effect of temperature modulation in the resistant snail stock, BS-90. Here, we show that, incubated for up to 4 hrs at 32°C prior to infection, these resistant snails became susceptible to infection, i.e. shedding cercariae at 5 weeks post exposure (PE) while unstressed resistant snails, as expected, remained resistant. This suggests that susceptibility to infection by this resistant snail phenotype is temperature-sensitive (ts). Additionally, resistant snails treated with the Hsp 90 specific inhibitor, geldanamycin (GA) after heat stress, were no longer susceptible to infection, retaining their resistant phenotype. Consistently, susceptible snail phenotypes treated with 100 mM GA before parasite exposure also remained uninfected. These results provide direct evidence for the induction of stress genes (heat shock proteins; Hsp 70, Hsp 90 and the reverse transcriptase [RT] domain of the nimbus non-LTR retrotransposon) in B. glabrata susceptibility to S. mansoni infection and characterize the resistant BS-90 snails as a temperature-sensitive phenotype. This study of reversing snail susceptibility phenotypes to S. mansoni provides an opportunity to directly track molecular pathway(s) that underlie the B. glabrata snail's ability to either sustain or destroy the S. mansoni parasite.

History of schistosomiasis epidemiology, current status, and challenges in China: on the road to schistosomiasis elimination.

PubMed

Song, Lan-Gui; Wu, Xiao-Ying; Sacko, Moussa; Wu, Zhong-Dao

2016-11-01

Schistosomiasis is a snail-borne disease caused by worms of the genus Schistosoma. Worldwide, human schistosomiasis remains a serious public health problem, threatening ∼800 million people in 78 countries with a loss of 70 million disability-adjusted life years. Schistosoma japonicum is the only human blood fluke that occurs in China. As one of the countries suffering greatly from schistosomiasis, over the past 65 years, China has made great strides in controlling schistosomiasis, blocking the transmission of S. japonicum in five provinces, remarkably reducing transmission intensities in the other seven endemic provinces, and China is currently preparing to move toward the elimination of this disease before 2025. However, while on the road to schistosomiasis elimination, emerging challenges merit attention, including severe advanced cases, increased movements of population and livestock, large-area distribution of intermediate host snails, limitations of new drug developments and no vaccine available, as well as imported schistosomiasis and its potential risk.

Risk analysis for occurrences of schistosomiasis in the coastal area of Porto de Galinhas, Pernambuco, Brazil

PubMed Central

2014-01-01

Background Manson’s schistosomiasis continues to be a severe public health problem in Brazil, where thousands of people live under the risk of contracting this parasitosis. In the Northeast of Brazil, schistosomiasis has expanded from rural areas to the coast of Pernambuco State, where the intermediate host is Biomphalaria glabrata snails. This study aims at presenting situational analyses on schistosomiasis at the coastal locality of Porto de Galinhas, Pernambuco, Brazil, by determining the risk factors relating to its occurrence from the epidemiological and spatial perspectives. Methods In order to gather prevalence data, a parasitological census surveys were conducted in 2010 in the light of the Kato-Katz technique. Furthermore, malacological surveys were also conducted in the same years so as to define the density and infection rates of the intermediate host. Lastly, socioeconomic-behavioral survey was also conducted to determine the odds ratio for infection by Schistosoma mansoni. Based on these data, spatial analyses were done, resulting in maps of the risk of disease transmission. To predict the risk of schistosomiasis occurrence, a multivariate logistic regression was performed using R 2.13 software. Results Based on prevalence, malacological and socioeconomic-behavioural surveys, it was identified a prevalence of 15.7% in the investigated population (2,757 individuals). Due to the malacological survey, 36 breeding sites were identified, of which 11 were classified as foci of schistosomiasis transmission since they pointed out snails which were infected by Schistosoma mansoni. Overall, 11,012 snails (Biomphalaria glabrata) were collected. The multivariate regression model identified six explanatory variables of environmental, socioeconomic and demographic nature. Spatial sweep analysis by means of the Bernoulli method identified one statistically significant cluster in Salinas (RR = 2.2; p-value < 0.000), the district with the highest occurrence of cases. Conclusions Based on the resulting information from this study, the epidemiological dimensions of this disease are significant and severe, within the scenario of schistosomiasis in Pernambuco state. The risk factors which were identified in the predictive model made it clear that the environmental and social conditions influence on the schistosomiasis occurrences. PMID:24559264

Population Genetics of Schistosoma japonicum within the Philippines Suggest High Levels of Transmission between Humans and Dogs

PubMed Central

Rudge, James W.; Carabin, Hélène; Balolong, Ernesto; Tallo, Veronica; Shrivastava, Jaya; Lu, Da-Bing; Basáñez, María-Gloria; Olveda, Remigio; McGarvey, Stephen T.; Webster, Joanne P.

2008-01-01

Background Schistosoma japonicum, which remains a major public health problem in the Philippines and mainland China, is the only schistosome species for which zoonotic transmission is considered important. While bovines are suspected as the main zoonotic reservoir in parts of China, the relative contributions of various non-human mammals to S. japonicum transmission in the Philippines remain to be determined. We examined the population genetics of S. japonicum in the Philippines in order to elucidate transmission patterns across host species and geographic areas. Methodology/Principal Findings S. japonicum miracidia (hatched from eggs within fecal samples) from humans, dogs, pigs and rats, and cercariae shed from snail-intermediate hosts, were collected across two geographic areas of Samar Province. Individual isolates were then genotyped using seven multiplexed microsatellite loci. Wright's FST values and phylogenetic trees calculated for parasite populations suggest a high frequency of parasite gene-flow across definitive host species, particularly between dogs and humans. Parasite genetic differentiation between areas was not evident at the definitive host level, possibly suggesting frequent import and export of infections between villages, although there was some evidence of geographic structuring at the snail–intermediate host level. Conclusions/Significance These results suggest very high levels of transmission across host species, and indicate that the role of dogs should be considered when planning control programs. Furthermore, a regional approach to treatment programs is recommended where human migration is extensive. PMID:19030225

The Scourge of Tropical Water Resources, Schistosomiasis,

DTIC Science & Technology

1980-12-13

penetrate into a suitable gastropod host. The miracidia locate their molluscan hosts by first being brought into range as a result natural taxes and...3). Upon entering a compatible gastropod host, the ciliated epithelium of the miracidium is sloughed and the parasite metamorphoses into a first...particular strain of snail to which the worm is adapted . Soon the infected snail swarms with progeny of the single larva that entered it; in a few weeks

Echinostoma macrorchis in Lao PDR: Metacercariae in Cipangopaludina Snails and Adults from Experimentally Infected Animals

PubMed Central

Sohn, Woon-Mok; Na, Byoung-Kuk; Yong, Tai-Soon; Eom, Keeseon S.; Park, Hansol; Min, Duk-Young; Rim, Han-Jong

2013-01-01

The echinostome metacercariae encysted in Cipangopaludina sp. snails that were purchased from a market in Vientiane Municipality, Lao PDR, were identified as Echinostoma macrorchis (Digenea: Echinostomatidae) through recovery of adult flukes after experimental infection to rats and a cat. The metacercariae were round, 113-128 (121)×113-125 (120) µm, having a thick cyst wall, a head collar armed with collar spines, and excretory granules. The adult flukes recovered from the rats and cat at day 14 and 30 post-infection, respectively, were elongated, ventrally curved, and 3.9-6.3×0.7-1.1 mm in size. The head collar was distinct, bearing 43-45 collar spines with 5 angle spines on each side. Two testes were large (as the name implies), tandem, and slightly constricted at the middle, with irregular margins. Eggs were operculated, ovoid to elliptical, and 88-95×56-60 µm. In scanning electron microscopy, the head collar was prominent, with 43-45 collar spines. Scale-like tegumental spines were densely distributed on the ventral surface between the oral and ventral suckers. Sensory papillae were distributed mainly on the tegument around the 2 suckers. It is confirmed that E. macrorchis is distributed in Lao PDR using Cipangopaludina sp. snails as the second intermediate host. PMID:23710086

A new cercaria and metacercaria of Acanthoparyphium (Echinostomatidae) found in an intertidal snail Zeacumantus subcarinatus (Batillaridae) from New Zealand.

PubMed

Martorelli, Sergio R; Poulin, Robert; Mouritsen, Kim N

2006-09-01

A new 23-collar-spined cercaria and metacercaria are described from intertidal molluscs of the coast of New Zealand. The new cercaria found emerging from the mud snails Zeacumantus subcarinatus (Sowerby) (Prosobranchia: Batillariidae) is characterized mainly by the number and arrangement of the cephalic glands, the size of the suckers, and the size and number of the collar spines. The cercaria encysts in the cockle Austrovenus stutchburyi (Wood) (Bivalvia: Veneridae) which lives in sympatry with the first intermediate host throughout New Zealand. Laboratory infections of cockles by cercariae from naturally infected snails resulted in metacercariae identical to those found in naturally infected cockles. The main features of the cercaria and metacercaria are the presence of a reniform collar with 23 spines, two pairs of small cephalic glands at the oral sucker level, another two pairs of much longer ones posterior to the pharynx, and the excretory vesicle Y-shaped with the main collecting canals extending to the anterior level of the ventral sucker. Each of the main collecting canals had 10-11 pairs of bilateral diverticula between the anterior edge of the ventral sucker and anterior body end. A brief discussion of its possible life cycle and ecology is also provided.

Morphological and ITS2 Molecular Characterization of Ribeiroia Cercariae (Digenea: Psilostomidae) from Biomphalaria spp. (Gastropoda: Planorbidae) in Northern Argentina.

PubMed

Davies, Dora; Davies, Carolina; Lauthier, Juan José; Hamann, Monika; Ostrowski de Núñez, Margarita

2015-10-01

Species of Ribeiroia use planorbid snails as intermediate host. Since there is little information about these digenean parasites in South America, we aimed to assess whether Ribeiroia cercariae from 3 north Argentina locations belonged to the same species and differed from Ribeiroia cercariae described elsewhere. Specimens were obtained from Biomphalaria tenagophila and Biomphalaria orbignyi (Salta Province), and Biomphalaria occidentalis (Corrientes Province). Morphological traits of cercariae were analyzed, as well as their sequence of the ribosomal internal transcribed spacer 2 (ITS2). The ITS2 region consisted of 426 nucleotides identical in all samples, suggesting that all specimens belong to the same species in spite of their morphological differences and first intermediate host species. Comparison of the ITS2 region with GenBank database records showed that specimens from Argentina were different from Ribeiroia ondatrae (0.9% divergence), Ribeiroia marini (0.7% divergence), and Cercaria lileta (0.2% divergence). In summary, morphological, ecological, and ITS2 molecular data suggest that specimens from Argentina belong to a different species.

Handling times and saturating transmission functions in a snail-worm symbiosis.

PubMed

Hopkins, Skylar R; McGregor, Cari M; Belden, Lisa K; Wojdak, Jeremy M

2018-06-16

All dynamic species interaction models contain an assumption that describes how contact rates scale with population density. Choosing an appropriate contact-density function is important, because different functions have different implications for population dynamics and stability. However, this choice can be challenging, because there are many possible functions, and most are phenomenological and thus difficult to relate to underlying ecological processes. Using one such phenomenological function, we described a nonlinear relationship between field transmission rates and host density in a common snail-oligochaete symbiosis. We then used a well-known contact function from predator-prey models, the Holling Type II functional response, to describe and predict host snail contact rates in the laboratory. The Holling Type II functional response accurately described both the nonlinear contact-density relationship and the average contact duration that we observed. Therefore, we suggest that contact rates saturate with host density in this system because each snail contact requires a non-instantaneous handling time, and additional possible contacts do not occur during that handling time. Handling times and nonlinear contact rates might also explain the nonlinear relationship between symbiont transmission and snail density that we observed in the field, which could be confirmed by future work that controls for other potential sources of seasonal variation in transmission rates. Because most animal contacts are not instantaneous, the Holling Type II functional response might be broadly relevant to diverse host-symbiont systems.

Brachylaima ezohelicis sp. nov. (Trematoda: Brachylaimidae) found from the land snail Ezohelix gainesi, with a note of an unidentified Brachylaima species in Hokkaido, Japan.

PubMed

Nakao, Minoru; Waki, Tsukasa; Sasaki, Mizuki; Anders, Jason L; Koga, Daisuke; Asakawa, Mitsuhiko

2017-06-01

In the Japanese Archipelago, Ezohelix gainesi, a member of bradybaenid land snails, is endemic mainly to the island of Hokkaido. During July to August of 2016, a survey to detect trematode infections from E. gainesi was carried out at a forest city park in Asahikawa, Hokkaido. Systemic infections of the snails with sporocysts containing short-tailed cercariae were found in 5.3% of 94 individuals examined. Furthermore, most of them (90.4%) harbored non-encysted metacercariae within their kidneys. A DNA sequence identification revealed that both of the sporocyst and the metacercaria belong to an unknown species of the family Brachylaimidae. The metacercariae showed a genetic diversity with 6 haplotypes of mitochondrial DNA (mtDNA) even in the limited sampling area. A definitive host of the unknown species could not be determined, although 34 field mice (Apodemus speciosus) and 21 voles (Myodes rufocanus) from the city park were examined for intestinal parasites. To examine the adult stage, the metacercariae were perorally administrated to mice, together with anti-inflammatory treatment with methylprednisolone. Fully matured adult worms were recovered from the intestinal ileum 8 and 14days postinfection. The gravid adults showed typical features of the genus Brachylaima. A morphological and biogeographical evaluation prompted us to propose Brachylaima ezohelicis sp. nov. for the parasite from E. gainesi. The autochthony of the first intermediate host and the spatial heterogeneity of mtDNA suggest that the new species found in the city park is not a recently expanded population of immigrant origin. Copyright © 2017 Elsevier B.V. All rights reserved.

The effects of host size and temperature on the emergence of Echinoparyphium recurvatum cercariae from Lymnaea peregra under natural light conditions.

PubMed

Morley, N J; Adam, M E; Lewis, J W

2010-09-01

The production of cercariae from their snail host is a fundamental component of transmission success in trematodes. The emergence of Echinoparyphium recurvatum (Trematoda: Echinostomatidae) cercariae from Lymnaea peregra was studied under natural sunlight conditions, using naturally infected snails of different sizes (10-17 mm) within a temperature range of 10-29 degrees C. There was a single photoperiodic circadian cycle of emergence with one peak, which correlated with the maximum diffuse sunlight irradiation. At 21 degrees C the daily number of emerging cercariae increased with increasing host snail size, but variations in cercarial emergence did occur between both individual snails and different days. There was only limited evidence of cyclic emergence patterns over a 3-week period, probably due to extensive snail mortality, particularly those in the larger size classes. Very few cercariae emerged in all snail size classes at the lowest temperature studied (10 degrees C), but at increasingly higher temperatures elevated numbers of cercariae emerged, reaching an optimum between 17 and 25 degrees C. Above this range emergence was reduced. At all temperatures more cercariae emerged from larger snails. Analysis of emergence using the Q10 value, a measure of physiological processes over temperature ranges, showed that between 10 and 21 degrees C (approximately 15 degrees C) Q10 values exceeded 100 for all snail size classes, indicating a substantially greater emergence than would be expected for normal physiological rates. From 14 to 25 degrees C (approximately 20 degrees C) cercarial emergence in most snail size classes showed little change in Q10, although in the smallest size class emergence was still substantially greater than the typical Q10 increase expected over this temperature range. At the highest range of 21-29 degrees C (approximately 25 degrees C), Q10 was much reduced. The importance of these results for cercarial emergence under global climate change is discussed.

A multidisciplinary, integrated approach for the elimination of schistosomiasis: a longitudinal study in a historically hyper-endemic region in the lower reaches of the Yangtze River, China from 2005 to 2014.

PubMed

Sun, Le-Ping; Wang, Wei; Zuo, Yin-Ping; Hong, Qing-Biao; Du, Guang-Lin; Ma, Yu-Cai; Wang, Jian; Yang, Guo-Jing; Zhu, Dao-Jian; Liang, You-Sheng

2017-03-14

Although great success has been achieved, schistosomiasis remains a major public health concern in China, and the remaining core endemic regions are concentrated along the middle and lower reaches of the Yangtze River. In this longitudinal study, we evaluated the effectiveness of a multidisciplinary, integrated approach for schistosomiasis elimination in a historically hyper-endemic region in the lower reaches of the Yangtze River, China over the 10-year period from 2005 through 2014. A three-step roadmap for schistosomiasis elimination was designed in the study site, and multidisciplinary, integrated interventions were implemented by the health, agriculture, water resources development, land and resources, and forestry sectors from 2005 to 2014, including chemotherapy for infected individuals, health education, management of the source of Schistosoma japonicum infection, and intermediate host snail control. The annual number of schistosomiasis patients, S. japonicum infection in humans, bovines and Oncomelania hupensis snails, and water infectivity were observed to assess the effectiveness of the multidisciplinary, integrated approach for the elimination of schistosomiasis. There was a tendency towards a gradual decline in both the number of schistosomiasis cases and the prevalence of S. japonicum human infection across the study period from 2005 through 2014. No S. japonicum human infection was detected since 2012, and no acute infection was seen since 2006. During the study period, no infection was found in bovines, and a 0.03% overall infection rate was observed in O. hupensis snails. Since 2009, no infected snails were identified, and the area of both snail habitats and infected snail habitats appeared a reduction over the study period. Following the 3-year multidisciplinary, integrated control, infection control was achieved, and transmission control was achieved after 6-year implementation, with all infected snails and water infectivity eliminated; in addition, the 10-year implementation resulted in interruption of schistosomiasis transmission in the study site in 2014. The results of the present 10-year longitudinal study demonstrate that the multidisciplinary, integrated approach is effective for the elimination of schistosomiasis as a public health problem in the lower reaches of the Yangtze River, China.

Trematode diversity in the freshwater snail Bithynia siamensis goniomphalos sensu lato from Thailand and Lao PDR.

PubMed

Kiatsopit, N; Sithithaworn, P; Kopolrat, K; Namsanor, J; Andrews, R H; Petney, T N

2016-05-01

In order to obtain a comprehensive understanding of trematode diversity in Bithynia siamensis goniomphalos sensu lato, the first intermediate host of the liver fluke Opisthorchis viverrini s.l., the prevalence of larval trematode species was investigated in different localities in Thailand and Lao People's Democratic Republic (Lao PDR). In Thailand, snail samples were collected from 29 localities in the nine provinces: Buri Ram, Surin, Chaiya Phum, Maha Sarakham, Khon Kaen, Kalasin, Mukdahan, Sakon Nakhon and Nakhon Phanom. In Lao PDR, snail samples were collected from 21 localities in Vientiane Province and six localities in Savannakhet Province. Snails were identified by standard morphological criteria and then examined for trematode infection using the cercarial shedding method. Twenty different types of cercariae were detected and identified, based on morphological criteria. Virgulate type 1 emerged as the most common cercaria, with an average prevalence of 10.90% (range 0.26-54.22%) in Thailand and 6.58% (range 1.15-89.77%) in Lao PDR. Opisthorchis viverrini s.l. cercariae were the fourth most common in Thailand, with an average prevalence of 1.59% (0.15-6.93), while in Lao PDR their prevalence was 0.96% (0.08-8.37). The high diversity of trematode cercariae observed in this study indicates that B. s. goniomphalos s.l. is highly susceptible to infection with a variety of trematode species. However, the role of non-opisthorchiid trematodes as fish-borne parasites in human health is not fully known and further molecular identification is required.

Dining local: the microbial diet of a snail that grazes microbial communities is geographically structured.

PubMed

O'Rorke, Richard; Cobian, Gerald M; Holland, Brenden S; Price, Melissa R; Costello, Vincent; Amend, Anthony S

2015-05-01

Achatinella mustelina is a critically endangered tree snail that subsists entirely by grazing microbes from leaf surfaces of native trees. Little is known about the fundamental aspects of these microbe assemblages: not taxonomic composition, how this varies with host plant or location, nor whether snails selectively consume microbes. To address these questions, we collected 102 snail faecal samples as a proxy for diet, and 102 matched-leaf samples from four locations. We used Illumina amplicon sequencing to determine bacterial and fungal community composition. Microbial community structure was significantly distinct between snail faeces and leaf samples, but the same microbes occurred in both. We conclude that snails are not 'picky' eaters at the microbial level, but graze the surface of whatever plant they are on. In a second experiment, the gut was dissected from non-endangered native tree snails in the same family as Achatinella to confirm that faecal samples reflect gut contents. Over 60% of fungal reads were shared between faeces, gut and leaf samples. Overall, location, sample type (faeces or leaf) and host plant identity all significantly explained the community composition and variation among samples. Understanding the microbial ecology of microbes grazed by tree snails enables effective management when conservation requires captive breeding or field relocation. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

Whole genome analysis of a schistosomiasis-transmitting freshwater snail

PubMed Central

Adema, Coen M.; Hillier, LaDeana W.; Jones, Catherine S.; Loker, Eric S.; Knight, Matty; Minx, Patrick; Oliveira, Guilherme; Raghavan, Nithya; Shedlock, Andrew; do Amaral, Laurence Rodrigues; Arican-Goktas, Halime D.; Assis, Juliana G.; Baba, Elio Hideo; Baron, Olga L.; Bayne, Christopher J.; Bickham-Wright, Utibe; Biggar, Kyle K.; Blouin, Michael; Bonning, Bryony C.; Botka, Chris; Bridger, Joanna M.; Buckley, Katherine M.; Buddenborg, Sarah K.; Lima Caldeira, Roberta; Carleton, Julia; Carvalho, Omar S.; Castillo, Maria G.; Chalmers, Iain W.; Christensens, Mikkel; Clifton, Sandra; Cosseau, Celine; Coustau, Christine; Cripps, Richard M.; Cuesta-Astroz, Yesid; Cummins, Scott F.; di Stefano, Leon; Dinguirard, Nathalie; Duval, David; Emrich, Scott; Feschotte, Cédric; Feyereisen, Rene; FitzGerald, Peter; Fronick, Catrina; Fulton, Lucinda; Galinier, Richard; Gava, Sandra G.; Geusz, Michael; Geyer, Kathrin K.; Giraldo-Calderón, Gloria I.; de Souza Gomes, Matheus; Gordy, Michelle A.; Gourbal, Benjamin; Grunau, Christoph; Hanington, Patrick C.; Hoffmann, Karl F.; Hughes, Daniel; Humphries, Judith; Jackson, Daniel J.; Jannotti-Passos, Liana K.; de Jesus Jeremias, Wander; Jobling, Susan; Kamel, Bishoy; Kapusta, Aurélie; Kaur, Satwant; Koene, Joris M.; Kohn, Andrea B.; Lawson, Dan; Lawton, Scott P; Liang, Di; Limpanont, Yanin; Liu, Sijun; Lockyer, Anne E.; Lovato, TyAnna L.; Ludolf, Fernanda; Magrini, Vince; McManus, Donald P.; Medina, Monica; Misra, Milind; Mitta, Guillaume; Mkoji, Gerald M.; Montague, Michael J.; Montelongo, Cesar; Moroz, Leonid L.; Munoz-Torres, Monica C.; Niazi, Umar; Noble, Leslie R.; Oliveira, Francislon S.; Pais, Fabiano S.; Papenfuss, Anthony T.; Peace, Rob; Pena, Janeth J.; Pila, Emmanuel A.; Quelais, Titouan; Raney, Brian J.; Rast, Jonathan P.; Rollinson, David; Rosse, Izinara C.; Rotgans, Bronwyn; Routledge, Edwin J.; Ryan, Kathryn M.; Scholte, Larissa L. S.; Storey, Kenneth B.; Swain, Martin; Tennessen, Jacob A.; Tomlinson, Chad; Trujillo, Damian L.; Volpi, Emanuela V.; Walker, Anthony J.; Wang, Tianfang; Wannaporn, Ittiprasert; Warren, Wesley C.; Wu, Xiao-Jun; Yoshino, Timothy P.; Yusuf, Mohammed; Zhang, Si-Ming; Zhao, Min; Wilson, Richard K.

2017-01-01

Biomphalaria snails are instrumental in transmission of the human blood fluke Schistosoma mansoni. With the World Health Organization's goal to eliminate schistosomiasis as a global health problem by 2025, there is now renewed emphasis on snail control. Here, we characterize the genome of Biomphalaria glabrata, a lophotrochozoan protostome, and provide timely and important information on snail biology. We describe aspects of phero-perception, stress responses, immune function and regulation of gene expression that support the persistence of B. glabrata in the field and may define this species as a suitable snail host for S. mansoni. We identify several potential targets for developing novel control measures aimed at reducing snail-mediated transmission of schistosomiasis. PMID:28508897

Study of surface carbohydrates in Galba truncatula tissues before and after infection with Fasciola hepatica

PubMed Central

Georgieva, Katya; Georgieva, Liliya; Mizinska-Boevska, Yana; Stoitsova, Stoyanka R

2016-01-01

The presence and distribution of surface carbohydrates in the tissues of Galba truncatula snails uninfected or after infection with Fasciola hepatica as well as on the surface of the snail-pathogenic larval stages of the parasite were studied by lectin labelling assay. This is an attempt to find similarities that indicate possible mimicry, utilised by the parasite as an evasion strategy in this snail-trematode system. Different binding patterns were identified on head-foot-mantle, hepatopancreas, genital glands, renopericardial complex of the host as well as of the snail-pathogenic larval stages of F. hepatica. The infection with F. hepatica leads to changes of labelling with Glycine max in the head-mantle cells and Arachis hypogaea in the tubular epithelium of the hepatopancreas. The lectin binding on the other snail tissues is not changed by the development of the larvae. Our data clearly demonstrated the similarity in labelling of G. truncatula tissues and the surface of the snail-pathogenic larval stages of F. hepatica. The role of glycosylation of the contact surfaces of both organisms in relation to the host-parasite interactions is also discussed. PMID:27384082

Study of surface carbohydrates in Galba truncatula tissues before and after infection with Fasciola hepatica.

PubMed

Georgieva, Katya; Georgieva, Liliya; Mizinska-Boevska, Yana; Stoitsova, Stoyanka R

2016-07-04

The presence and distribution of surface carbohydrates in the tissues of Galba truncatula snails uninfected or after infection with Fasciola hepatica as well as on the surface of the snail-pathogenic larval stages of the parasite were studied by lectin labelling assay. This is an attempt to find similarities that indicate possible mimicry, utilised by the parasite as an evasion strategy in this snail-trematode system. Different binding patterns were identified on head-foot-mantle, hepatopancreas, genital glands, renopericardial complex of the host as well as of the snail-pathogenic larval stages of F. hepatica. The infection with F. hepatica leads to changes of labelling with Glycine max in the head-mantle cells and Arachis hypogaea in the tubular epithelium of the hepatopancreas. The lectin binding on the other snail tissues is not changed by the development of the larvae. Our data clearly demonstrated the similarity in labelling of G. truncatula tissues and the surface of the snail-pathogenic larval stages of F. hepatica. The role of glycosylation of the contact surfaces of both organisms in relation to the host-parasite interactions is also discussed.

Sociality in Parasitic Flatworms: When Do Soldiers Matter?

NASA Astrophysics Data System (ADS)

Garcia-Vedrenne, A. E.

2016-02-01

Although not traditionally recognized as such, trematode infections in molluscan first intermediate hosts comprise colonies. When two trematode species simultaneously infect a snail host, one generally kills the other. Thus, there can be strong selective pressure for established trematode colonies to protect and defend against new infections. Recent findings demonstrate that some trematode species have a reproductive division of labor involving a reproductive and a soldier caste. Reproductives are larger and filled with offspring, while soldiers lack developing embryos, and are specialized for inter-trematode antagonism. This reproductive division of labor has now been documented for intramolluscan stages of fourteen trematode species from different geographic regions and host species. Further, literature descriptions of the life history of several species suggest that this phenomenon is widespread, although there are important intra- and inter-specific differences in colony structure. It has been predicted that trematode soldier castes would most likely evolve in taxa that are typically dominant in interspecific hierarchies, in situations of invasion risk, and among trematodes that infect longer lived hosts. Here I address these hypotheses and present the extent of evidence for trematode social organization.

Differences in the number of hemocytes in the snail host Biomphalaria tenagophila, resistant and susceptible to Schistosoma mansoni infection.

PubMed

Oliveira, A L D; Levada, P M; Zanotti-Magalhaes, E M; Magalhães, L A; Ribeiro-Paes, J T

2010-12-21

The relationships between schistosomiasis and its intermediate host, mollusks of the genus Biomphalaria, have been a concern for decades. It is known that the vector mollusk shows different susceptibility against parasite infection, whose occurrence depends on the interaction between the forms of trematode larvae and the host defense cells. These cells are called amebocytes or hemocytes and are responsible for the recognition of foreign bodies and for phagocytosis and cytotoxic reactions. The defense cells mediate the modulation of the resistant and susceptible phenotypes of the mollusk. Two main types of hemocytes are found in the Biomphalaria hemolymph: the granulocytes and the hyalinocytes. We studied the variation in the number (kinetics) of hemocytes for 24 h after exposing the parasite to genetically selected and non-selected strains of Biomphalaria tenagophila, susceptible or not to infection by Schistosoma mansoni. The differences were analyzed referred to the variations in the number of hemocytes in mollusks susceptible or not to infection by S. mansoni. The hemolymph of the selected and non-selected snails was collected, and hemocytes were counted using a Neubauer chamber at six designated periods: 0 h (control, non-exposed individuals), 2 h, 6 h, 12 h, 18 h and, 24 h after parasite exposure. Samples of hemolymph of five selected mollusks and five non-selected mollusks were separately used at each counting time. There was a significant variation in the number of hemocytes between the strains, which indicates that defense cells have different behaviors in resistant and susceptible mollusks.

Relationship between the transmission of schistosomiasis japonica and the construction of the Three Gorge Reservoir.

PubMed

Zheng, Jiang; Gu, Xue-guang; Xu, Yong-long; Ge, Ji-hua; Yang, Xian-xiang; He, Chang-hao; Tang, Chao; Cai, Kai-ping; Jiang, Qing-wu; Liang, You-sheng; Wang, Tian-ping; Xu, Xing-jian; Zhong, Jiu-he; Yuan, Hong-chang; Zhou, Xiao-nong

2002-05-01

To study the relationship between the changes of environment and the transmission of Schistosomiasis japonica after the construction of the Three Gorge Reservoir. On the basis of the predictive data on changes of water level and sediment in the middle and lower reaches of the Yangtze River after the dam construction provided by the Yangtze River Committee on Water Conservancy, corresponding data were collected and analyzed. In order to understand the effects of changes of water level and sediment on Oncomelania hupensis, the intermediate host of Schistosoma japonicum, field surveys and ecologically intimated experiments were done. The prevalence status and factors related to transmission were investigated by epidemiology, medical geography and public health. Positive impact on control of schistosomiasis is that floods in the Yangtze River will occur less and will decrease the dispersal of snails and the chances of infection for humans and animals as well. Snail habitats' beach will be reduced in the flushed area along the Yangtze River. Exploitation of beach and elimination of snails will benefit from the beach's uplift in flushed area. The floods ahead of time in autumn will interfere with the development of snails. Negative impact is that the flushed beaches and migratory settlements at certain altitude may become snail habitats. So the reservoir area will be a potential transmission area of schistosomiasis due to dispersal of infectious resources and Oncomelania snails. The uprising of the water body level may cause the expending of the snail habitats in some places of Jianghan plain during the transition of spring to summer. The destruction of the embankments of the Dongting Lake will be put off by its delayed flush, which causes the beach in a situation of growing reed-grass or grass for a long time that benefits the reproduction of the snails. The chances for schistosome infection to humans and animals will be on the increase, because the water regression occurs ahead of time in the Dongting Lake beach in autumn. The distribution of snails will not be affected by the changes of water level in the lower reaches of the Yangtze River after the dam is built, but the flushed section in Anhui in the recent 80 years are suitable for the snails' development. The environmental changes due to dam construction will not obviously affect the development of snails and the transmission of schistosomiasis in the Poyang Lake area. The construction of the huge dam and the formation of the Three Gorge Reservoir on the Yangtze River may have both positive and negative impact on schistosomiasis transmission and control. Great effort must be made to decrease the negative impact to avoid or, at least, to decrease S. japonicum transmission.

[Morphology of III stage larvae of Angiostrongylus cantonensis in Pomacea canaliculata].

PubMed

Zhang, Chao-Wei; Zhou, Xiao-Nong; Lv, Shan; Zhang, Yi; Liu, He-Xiang

2008-06-30

To observe the morphologic characteristics of III stage larvae of Angiostrongylus cantonensis from Pomacea canaliculata. P. canaliculata, the intermediate host snail of A. cantonensis, was infected with I stage larvae of A. cantonensis in laboratory. After 61 days, III stage larvae of A. cantonensis were harvested from snail's lungs and muscle of head-foot, followed by HE stain to observe morphological characteristics. The whole body of III stage larva was curling with obtuse head. Its pharyngeal canal extends from the buccal hole on the top of the head to the intestines at the pharyngeal intestine joint place, with apex cauda and clear anal tube. The tegument of the III stage larva was eosin-stained, with a transparent sheath outside of tegument. Some of the larvae cauda showed in circular cylinder, and some larvae presented ventral gland with two very short uterine which used to be the feature only showed in early IV stage larva. Morphologically characteristics of the III stage larvae is helpful to better understand the life-cycle and the control of A. cantonensis.

Factors affecting laboratory acclimatization of field collected Lymnaea (Bullastra) cumingiana Pfeiffer (Pulmonata: Lymnaeidae).

PubMed

Monzon, R B; Kitikoon, V

1991-12-01

Lymnaea (Bullastra) cumingiana, the newly discovered natural second intermediate host of Echinostoma malayanum in the Philippines, is a sensitive and delicate lymnaeid species which requires certain conditions for successful transport from the field and cultivation in the laboratory. Field collected specimens were found to be best transported in styrofoam containers lined with wet filter paper or containing natural substrate and vegetation instead of Sphagnum moss. The method is convenient and produces a survival rate of 73-86%. However, transport time is crucial and mortality increases the longer the snails are in transit. For optimal results in laboratory acclimatization, snails are best raised in wide-mouthed containers providing a large exposed water surface area. Adequate aeration is advised but vigorous bubbling of the water should be avoided. Water should be replaced with filtered dechlorinated water every 2 to 3 days, depending on water quality. A combination of fresh lettuce leaves and a few flakes of fish food was found to be ideal. Lastly, population density was the most significant factor affecting survival and so overcrowding should be avoided.

Clinical aspects of eosinophilic meningitis and meningoencephalitis caused by Angiostrongylus cantonensis, the rat lungworm.

PubMed

Murphy, Gerald S; Johnson, Stuart

2013-06-01

Angiostrongylus Eosinophilic Meningitis is caused by human infection with larvae of the rat lungworm, Angiostrongylus cantonensis. The clinical presentation includes a spectrum of disease, from meningitis through radiculitis, cranial nerve abnormalities, ataxia, encephalitis, coma, and rarely death. The condition is diagnosed by recognizing the triad of: the clinical syndrome, eosinophils in the cerebrospinal fluid or blood, and exposure history. A history of eating raw or poorly cooked snails is classic, but ingestion of other intermediate hosts or unwashed produce (such as lettuce) harboring hosts is not uncommon. Several serologic tests exist but none has yet been fully validated. There is good evidence that a 2 week course of high dose corticosteroids shortens the duration and severity of symptoms. There is somewhat weaker evidence that albendazole reduces symptoms. The combination of prednisolone and albendazole is being used more commonly for treatment. Some suggestions for future research are given.

Fasciola gigantica: cercarial shedding pattern from Lymnaea natalensis after long-term exposure to cadmium at different temperatures.

PubMed

Soliman, Maha F M

2009-04-01

Little is known about the response of Fasciola spp., inside its snail host to pollutant toxicity. The effect of long-term exposure of Lymnaea natalensis to 0.1 microg/l, 10 microg/l, or 100 microg/l cadmium (Cd) on the infection rates with F. gigantica, percentage of cercariae-shedding snails and cercariae shedding pattern was investigated. The snails were exposed to Cd for 7 days either pre-infection with single Fasciola miracidium or during the late pre-patent period of the infection. The possible interaction between metal exposure and acclimatization temperature was also studied in three ranges; 16-18 degrees C, 23-25 degrees C and 30-32 degrees C. Results clearly showed that host exposure to 100 microg/l Cd significantly affected the pattern of Fasciola development inside its snail host, and that the acclimatization temperature was a key factor affecting the role played by Cd. Pre-infection exposure to Cd caused a significant reduction in the infection rates where the effect was temperature-dependent. Post-infection exposure to Cd significantly increased the percentage of cercariae-shedding snails; the effect was temperature-independent. Interestingly, post-infection exposure significantly altered the differential cercarial output pattern, while no clear impact on the total was found. The alteration in the differential cercarial output was represented as a significantly higher proportion of floating metacercaria as compared to fixed ones and also higher proportion of dead cercariae which may directly reduce the transmission of Fasciola to the final host. The mechanisms of cadmium impact are briefly discussed.

Combining Remotely Sensed Environmental Characteristics with Social and Behavioral Conditions that Affect Surface Water Use in Spatiotemporal Modelling of Schistosomiasis in Ghana

NASA Astrophysics Data System (ADS)

Kulinkina, A. V.; Walz, Y.; Liss, A.; Kosinski, K. C.; Biritwum, N. K.; Naumova, E. N.

2016-06-01

Schistosoma haematobium transmission is influenced by environmental conditions that determine the suitability of the parasite and intermediate host snail habitats, as well as by socioeconomic conditions, access to water and sanitation infrastructure, and human behaviors. Remote sensing is a demonstrated valuable tool to characterize environmental conditions that support schistosomiasis transmission. Socioeconomic and behavioral conditions that propagate repeated domestic and recreational surface water contact are more difficult to quantify at large spatial scales. We present a mixed-methods approach that builds on the remotely sensed ecological variables by exploring water and sanitation related community characteristics as independent risk factors of schistosomiasis transmission.

Occurrence of a Snail Borne Disease, Cercarial Dermatitis (Swimmer Itch) in Doon Valley (Uttarakhand), India

PubMed Central

JAUHARI, Rakesh Kumar; NONGTHOMBAM, Pemola Devi

2014-01-01

Abstract Background ‘Cercarial dermatitis’ also known as swimmers itch (Skin allergies) is caused by a trematode parasite, Schistosoma which has two hosts - an invertebrate (snail) and a vertebrate (livestock, human being). Although the availability of both vector snails and pathogens at the selected site the Doon Valley in northern India has already been confirmed but there was a hazy picture of the disease, whether it is due to entrance of cercariae or due to wild variety of grass (Parthenium hysterophorus). The present study is an attempt to provide a way forward towards the vector snails and snail borne diseases in the study area. Methods Snail sampling and identification was done by applying standard methods / using Keys & Catalogues. Associated parasites and cercariometry in snails has been worked out by cercarial shedding. Human involvement at zo-onotic level has been performed in collaboration with Health centers and socio- economic aspect of inhabitants of study area. Results The snail diversity encountered 19 species including the vector species such as Indoplanorbis exustus, Gyraulus convexiusculus, Melanoides tuberculata and Lymnaea acuminata. The cercarial diversity comprised Furcocercous, Monostome, Amphistome and liver fluke / Xiphidiocercaria. During the study (2009–2010), 0.173% was found with cercarial dermatitis among human population in the selected area. The symptoms of disease recorded were red spots and swellings on effected parts of skin. Frequent visits of livestock to the water body and presence of vector snails provides a clue in completing the life cycle of the parasite of the family Schistosomatidae. Conclusion Cercarial dermatitis has been considered a potential risk at those places where warm blooded and snail’s hosts share a link with aquatic bodies with particular emphasis to temperature and time of year. PMID:26060739

Seasonal dynamics of snail populations in coastal Kenya: Model calibration and snail control

NASA Astrophysics Data System (ADS)

Gurarie, D.; King, C. H.; Yoon, N.; Wang, X.; Alsallaq, R.

2017-10-01

A proper snail population model is important for accurately predicting Schistosoma transmission. Field data shows that the overall snail population and that of shedding snails have a strong pattern of seasonal variation. Because human hosts are infected by the cercariae released from shedding snails, the abundance of the snail population sets ultimate limits on human infection. For developing a predictive dynamic model of schistosome infection and control strategies we need realistic snail population dynamics. Here we propose two such models based on underlying environmental factors and snail population biology. The models consist of two-stage (young-adult) populations with resource-dependent reproduction, survival, maturation. The key input in the system is seasonal rainfall which creates snail habitats and resources (small vegetation). The models were tested, calibrated and validated using dataset collected in Msambweni (coastal Kenya). Seasonal rainfall in Msambweni is highly variable with intermittent wet - dry seasons. Typical snail patterns follow precipitation peaks with 2-4-month time-lag. Our models are able to reproduce such seasonal variability over extended period of time (3-year study). We applied them to explore the optimal seasonal timing for implementing snail control.

Ecological consequences of manipulative parasites: chapter 9

USGS Publications Warehouse

Lafferty, Kevin D.; Kuris, A. M.

2012-01-01

Parasitic "puppet masters", with their twisted, self-serving life history strategies and impressive evolutionary takeovers of host minds, capture the imagination of listeners—even those that might not normally fi nd the topic of parasitism appealing (which includes most everyone). A favorite anecdote concerns the trematode Leucochloridium paradoxum migrating to the eyestalks of its intermediate host snail and pulsating its colored body, presumably to attract the predatory birds that are the final hosts for the worm. Identifying a parasite as “manipulative” infers that a change in host behavior or appearance is a direct consequence of the parasite’s adaptive actions that, on average, will increase the fi tness of the parasite. The list of parasites that manipulate their hosts is long and growing. Holmes and Bethel (1972) presented the earliest comprehensive review and brought the subject to mainstream ecologists. Over two decades ago, Andy Dobson (1988) listed seven cestodes, seven trematodes, ten acanthocephalans, and three nematodes that manipulated host behavior. Fifteen years later, Janice Moore (2002) filled a book with examples. The five infectious trophic strategies, typical parasites (macroparasites), pathogens, trophically transmitted parasites, parasitic castrators, and parasitoids (Kuris and Lafferty 2000; Lafferty and Kuris 2002, 2009) can modify host behavior, but the likelihood that a parasite manipulates behavior differs among strategies. The most studied infectious agents, non-trophically transmitted pathogens and macroparasites, have enormous public health, veterinary, and wildlife disease importance, yet few manipulate host behavior. The beststudied manipulative infectious agents are trophically transmitted parasites in their prey intermediate hosts. Parasitoids and parasitic castrators can also manipulate host behavior, but for different purposes and with different implications. Several studies of manipulative parasites conclude with phrases such as “may ultimately infl uence community structure” (Kiesecker and Blaustein 1999), yet few demonstrate ecological effects. Here, we consider the conditions under which manipulative parasites might have a substantial ecological effect in nature and highlight those for which evidence exists (see also Chapter 10).

Risk profiling of schistosomiasis using remote sensing: approaches, challenges and outlook.

PubMed

Walz, Yvonne; Wegmann, Martin; Dech, Stefan; Raso, Giovanna; Utzinger, Jürg

2015-03-17

Schistosomiasis is a water-based disease that affects an estimated 250 million people, mainly in sub-Saharan Africa. The transmission of schistosomiasis is spatially and temporally restricted to freshwater bodies that contain schistosome cercariae released from specific snails that act as intermediate hosts. Our objective was to assess the contribution of remote sensing applications and to identify remaining challenges in its optimal application for schistosomiasis risk profiling in order to support public health authorities to better target control interventions. We reviewed the literature (i) to deepen our understanding of the ecology and the epidemiology of schistosomiasis, placing particular emphasis on remote sensing; and (ii) to fill an identified gap, namely interdisciplinary research that bridges different strands of scientific inquiry to enhance spatially explicit risk profiling. As a first step, we reviewed key factors that govern schistosomiasis risk. Secondly, we examined remote sensing data and variables that have been used for risk profiling of schistosomiasis. Thirdly, the linkage between the ecological consequence of environmental conditions and the respective measure of remote sensing data were synthesised. We found that the potential of remote sensing data for spatial risk profiling of schistosomiasis is - in principle - far greater than explored thus far. Importantly though, the application of remote sensing data requires a tailored approach that must be optimised by selecting specific remote sensing variables, considering the appropriate scale of observation and modelling within ecozones. Interestingly, prior studies that linked prevalence of Schistosoma infection to remotely sensed data did not reflect that there is a spatial gap between the parasite and intermediate host snail habitats where disease transmission occurs, and the location (community or school) where prevalence measures are usually derived from. Our findings imply that the potential of remote sensing data for risk profiling of schistosomiasis and other neglected tropical diseases has yet to be fully exploited.

DIAGNOSIS AND THERAPY OF LIVER FLUKE (FASCIOLOIDES MAGNA) INFECTION IN FALLOW DEER (DAMA DAMA) IN SERBIA.

PubMed

Trailović, Saša M; Marinković, Darko; Kulišić, Zoran

2016-04-28

Giant liver fluke ( Fascioloides magna ) infection is an important health problem of cervids in southeastern Europe. We measured the prevalence and intensity of infection with F. magna in a fenced area near the Danube River in the South Bačka District of Serbia. Parasitologic, pathomorphologic, and histopathologic examinations were conducted from November 2007 to February 2008, beginning with a population of 127 adult fallow deer ( Dama dama ). After a positive diagnosis, therapy with triclabendazole-medicated corn was applied. Deer were treated at four baiting stations, using medicated feed providing triclabendazole at an estimated dose of 10-14 mg/kg of body weight per deer. Treatment lasted for 7 d in early February 2008 and an additional 7 d 2 wk later. For the complete success of pharmacotherapy it was necessary to prevent any contact of deer with the snail intermediate host ( Galba truncatula ). Intervention in the habitat, removing grass and low vegetation, and draining ponds reduces the possibility of contact. Six months after the treatment, livers of hunted deer were reddish, with fibrous tracks; pigmentation and cysts in the parenchyma were surrounded by a fibrous capsule and their fecal samples contained no eggs of F. magna . Over the following years, livers of hunted deer were negative, and the last control cull in March 2015 confirmed complete absence of infection. We reconfirmed the presence of giant liver flukes in fallow deer in Serbia, apparently the result of natural spread across the Danube from Hungary and Croatia. We also report that the treatment of deer with triclabendazole-medicated corn is an effective method for administration of therapeutic doses of drug in semicaptive deer. Interventions in the environment are necessary to prevent recontact of deer with habitats used by the snail intermediate host, and enable the success of the therapy.

MOLLUSCICIDAL AND LARVICIDAL ACTIVITIES OF Atriplex inflata AERIAL PARTS AGAINST THE MOLLUSK Galba truncatula, INTERMEDIATE HOST OF Fasciola hepatica

PubMed Central

HAMED, Néjia; NJEH, Fatma; DAMAK, Mohamed; AYADI, Ali; MEZGHANI-JARRAYA, Raoudha; HAMMAMI, Hayet

2015-01-01

Fasciolosis is a widespread parasitosis of farm live-stock in many developing countries. For this reason, it is necessary to search for new substances against parasitic diseases caused by flukes. Indeed, a wide variety of terrestrial plants have been subjected to chemical and pharmacological screening in order to discover their potential for human medicinal use. The molluscicidal and larvicidal activities of Atriplex inflata were tested on Galba truncatula and Fasciola hepatica larval stages infecting this snail in Tunisia. Phytochemical tests were conducted on extracts in order to establish a meaningful relationship with molluscicidal and larvicidal activities. The molluscicidal activity was evaluated by subjecting snails to sample aqueous solutions. Accordingly, hexane, ethyl acetate, methanol and methanol-water (8:2, v-v) were used as extraction solvents. As a result, hexane and ethyl acetate extracts showed potent activity, according to the World Health Organization, giving LC50 = 7.59 mg/L and 6.69 mg/L for hexane extracts of leaves and fruits, respectively. Ethyl acetate extracts gave LC50 = 5.90 mg/L and 7.32 mg/L for leaves and fruits, successively. Molluscicidal activities of powders were less potent on snails, but active according to the World Health Organization. Hexane and ethyl acetate extracts from leaves and fruits gave potent larvicidal activities with a delay rate exceeding 45.50% (45.50- 98.92%). Phytochemical tests showed that these activities may be attributed to the presence of triterpenoids and/or sterols. PMID:27049700

Spatio-temporal pattern of schistosomiasis in Anhui Province, East China: Potential effect of the Yangtze River - Huaihe River Water Transfer Project.

PubMed

Cao, Zhi-Guo; Li, Si; Zhao, Ya-E; Wang, Tian-Ping; Bergquist, Robert; Huang, Yin-Yin; Gao, Feng-Hua; Hu, Yi; Zhang, Zhi-Jie

2018-05-09

Anhui Province has been one of typical epidemic areas of schistosomiasis in East China as a wide range of large lake and marshland regions provide an ideal environment for growth and reproduction of the intermediate snail host. With the completion of the Yangtze River-Huaihe River Water Transfer Project (YHWTP), launched by the end of 2016, the epidemic areas are expected to expand and controlling schistosomiasis remains a challenge. Based on annual surveillance data at the county level in Anhui for the period 2006-2015, spatial and temporal cluster analyses were conducted to assess the pattern of risk through spatial (Local Moran's I and flexible scan statistic) and space-time scan statistic (Kulldorff). It was found that schistosomiasis sero-prevalence was dramatically reduced and maintained at a low level. Cluster results showed that spatial extent of schistosomiasis contracted, but snail distribution remained geographically stable across the study area. Clusters, both for schistosomiasis and snail presence, were common along the Yangtze River. Considering the effect of the ongoing YHWTP on the potential spread of schistosomiasis, Zongyang County and Anqing, which will be transected by the new water-transfer route, should be given a priority for strengthened surveillance and control. Attention should also be paid to Guichi since it is close to one of the planned inlets of the YHWTP. Copyright © 2018 Elsevier B.V. All rights reserved.

Factors conditioning the habitat of bilharziasis intermediate hosts of the family Planorbidae

PubMed Central

Abdel Malek, Emile

1958-01-01

In this article, the author examines certain physical, chemical and biological characteristics of water-bodies which make them suitable or unsuitable as habitats for planorbid snails acting as vectors of bilharziasis. The principal conditioning factors appear to be: amount of food available; extent of the growth of aquatic weeds; oxygen content of the water; amount of sunlight able to penetrate the water; strength of the current; nature of the substratum; ionic composition of the water; and presence or absence of parasites and predators. Several of these factors are interdependent. Although there are differences between the various species in their habitat requirements, their ranges of tolerance were found to overlap greatly. The optimum conditions are similar for all species, but extremes are tolerated better by some species than by others. Theoretically, extremes of certain factors should be capable of eliminating snails from a body of water; in practice such extremes rarely occur, and the absence of vectors must be attributed to the combined effect of several factors. Although certain parasites and predators exterminate vectors in the laboratory, the author considers it unlikely that they would do so in nature, as under laboratory conditions the biological balance is disturbed to the disadvantage of the snail. The data available are still too scanty for an exact assessment to be made of the importance of individual environmental factors in controlling the size of vector populations; but this review of present knowledge indicates the lines along which further investigation can be most profitably pursued. PMID:13573113

Systematic Review and Meta-analysis of the Impact of Chemical-Based Mollusciciding for Control of Schistosoma mansoni and S. haematobium Transmission

PubMed Central

King, Charles H.; Sutherland, Laura J.; Bertsch, David

2015-01-01

Background Programs for schistosomiasis control are advancing worldwide, with many benefits noted in terms of disease reduction. Yet risk of reinfection and recurrent disease remain, even in areas with high treatment coverage. In the search for means to better prevent new Schistosoma infections, attention has returned to an older strategy for transmission control, i.e., chemical mollusciciding, to suppress intermediate host snail species responsible for S. mansoni and S. haematobium transmission. The objective of this systematic review and meta-analysis was to summarize prior experience in molluscicide-based control of Bulinus and Biomphalaria spp. snails, and estimate its impact on local human Schistosoma infection. Methodology/Principal Findings The review was registered at inception with PROSPERO (CRD42013006869). Studies were identified by online database searches and hand searches of private archives. Eligible studies included published or unpublished mollusciciding field trials performed before January 2014 involving host snails for S. mansoni or S. haematobium, with a primary focus on the use of niclosamide. Among 63 included papers, there was large variability in terms of molluscicide dosing, and treatment intervals varied from 3–52 weeks depending on location, water source, and type of application. Among 35 studies reporting on prevalence, random effects meta-analysis indicated that, on average, odds of infection were reduced 77% (OR 0.23, CI95% 0.17, 0.31) during the course of mollusciciding, with increased impact if combined with drug therapy, and progressively greater impact over time. In 17 studies reporting local incidence, risk of new infection was reduced 64% (RR 0.36 CI95% 0.25, 0.5), but additional drug treatment did not appear to influence incidence effects. Conclusion/Significance While there are hurdles to implementing molluscicide control, its impact on local transmission is typically strong, albeit incomplete. Based on past experience, regular focal mollusciciding is likely to contribute significantly to the move toward elimination of schistosomiasis in high risk areas. PMID:26709922

Does the trematode Centrocestus formosanus affect the locomotory activity of the mollusc Melanoides tuberculatus?

PubMed Central

2013-01-01

Background Melanoides tuberculatus (Müller, 1774) (Thiaridae), an introduced gastropod mollusc with a wide geographical distribution in the Neotropics, is the intermediate host of the trematode Centrocestus formosanus (Nishigori, 1924) (Heterophyidae). This parasite is considered to be pathogenic to humans. The aim of the present work was to evaluate the locomotory activity of uninfected M. tuberculatus compared with those naturally infected with C. formosanus. Findings The locomotory activity of each mollusc was recorded using an image analysis biomonitoring system, Videomex-V ®, to evaluate and quantify the parameters of ‘Stereotypic’ and ‘Resting time’. The Generalized Estimating Equation analysis of locomotory activity of M. tuberculatus infected with C. formosanus revealed significant differences compared with uninfected molluscs for the parameters ‘Stereotypic time’ and ‘Resting time’ with a reduction of movement. The variations in the values of the monitoring intervals recorded showed a significant difference for the infected molluscs in the case of Stereotypic time, with an irregular locomotory activity pattern, as compared to that of uninfected molluscs. The analysis of the standard length of all molluscs did not exhibit any correlation with locomotory activity, showing that C. formosanus is able to alter the locomotory activity of its snail host regardless of the standard length. Conclusions The trematode C. formosanus affects the locomotory activity of the mollusc M. tuberculatus by reducing its movement and causing it to exhibit an irregular pattern of activity, both of which are independent of the snail's standard length. PMID:23574763

[An activity of nonspecific esterases in homogenates of Lymnaea stagnalis and Lymnaea tumida snails (Gastropoda: Pulmonata) infected by trematode cercariae Echinoparyphium aconiatum and Moliniella anceps (Echinostomatidae)].

PubMed

Vorontsova, Ia L; Iurlova, N I; Vodianitskaia, S N; Glupov, V V

2008-01-01

The comparative analysis of esterase changes in homogenates of the snails Lymnaea stagnalis and L. tumida bodies was carried out. Juvenile snails with shell size 2 mm, 3-4 mm, 5-6 mm and 7-8 mm were exposed to cercariae of the trematodes Echinoparyphium aconiatum and/or Moliniella anceps. The esterase activity was detected spectrofotometrically. The highest level of esterase activity in noninfected L. stagnalis was registered in snails with shell size 3-4 mm. The invasion of snails by trematode cercariae results in a change of esterase activity in the tissues of infected snails. The activity of easterases was increased in the infected L. stagnalis snails with shell size 5-8 mm at 2 days post invasion in comparison with control. The decrease of esterase activity in tissues of infected snails L. stagnalis (3-4 mm) and L. tumida (4 mm) was observed at 26 days post invasion by E. aconiatum only. The host size and parasite species was influenced on esterase activity in the snails.

Helminth parasites of bighorn sheep in Oregon.

PubMed

Kistner, T P; Matlock, S M; Wyse, D; Mason, G E

1977-04-01

The lungs and gastrointestinal tracts from 18 hunter-killed bighorn rams (Ovis canadensis californiana) were examined in total or in part for helminth parasites during a two-year study of three separate herds in Eastern Oregon. Prevalence was 100% with the lungworm Protostrongylus stilesi. The gastrointestinal fauna from 11 rams comprised Cooperia oncophora, Marshallagia marshalli, Nematodirus oiratianus, Oesophagostomum spp., Ostertagia occidentalis, O. ostertagi, Skrjabinema ovis, Trichostrongylus axei and Trichuris spp. Adult Wyominia tetoni and cysticerci of Taenia hydatigena were recovered from two of six livers examined. Additionally, searches for potential molluscan intermediate hosts for P. stilesi were conducted on one bighorn range. Snails identified as belonging to the genera Euconulus, Pupilla and Vallonia were found on both the summer and winter ranges.

Real-time PCR strategy for rapid discrimination among main lymnaeid species from Argentina.

PubMed

Duffy, T; Kleiman, F; Pietrokovsky, S; Issia, L; Schijman, A G; Wisnivesky-Colli, C

2009-01-01

Snails of the Family Lymnaeidae act as an intermediate hosts of Fasciola hepatica worldwide. The taxonomy of lymnaeid species is relevant for epidemiological studies and molecular strategies are increasingly used for that purpose. This work presents the first report of a real-time PCR approach used to identify the most important lymnaeid species in the Southern Cone of South America. Species discrimination is based on the sequence polymorphism located within the helix E10-1 of the variable region V2 of the 18S rRNA genes, which yields amplicons with clearly different melting temperatures. This procedure minimises the risk of carry-over contamination because it does not require post-PCR manipulations, and the whole protocol can be completed in less than 4h with a single snail foot as starting material. This method was successfully carried out in a blind study that included a panel of 20 Galba truncatula, 5 Lymnaea viatrix, 5 Lymnaea diaphana and 5 Pseudosuccinea columella specimens from different endemic areas for fasciolosis. This molecular approach constitutes a key laboratory tool complementing ecological studies that ultimately will promote more efficient control strategies.

The temporal patterns of disease severity and prevalence in schistosomiasis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciddio, Manuela; Gatto, Marino, E-mail: marino.gatto@polimi.it; Casagrandi, Renato, E-mail: renato.casagrandi@polimi.it

2015-03-15

Schistosomiasis is one of the most widespread public health problems in the world. In this work, we introduce an eco-epidemiological model for its transmission and dynamics with the purpose of explaining both intra- and inter-annual fluctuations of disease severity and prevalence. The model takes the form of a system of nonlinear differential equations that incorporate biological complexity associated with schistosome's life cycle, including a prepatent period in snails (i.e., the time between initial infection and onset of infectiousness). Nonlinear analysis is used to explore the parametric conditions that produce different temporal patterns (stationary, endemic, periodic, and chaotic). For the time-invariantmore » model, we identify a transcritical and a Hopf bifurcation in the space of the human and snail infection parameters. The first corresponds to the occurrence of an endemic equilibrium, while the latter marks the transition to interannual periodic oscillations. We then investigate a more realistic time-varying model in which fertility of the intermediate host population is assumed to seasonally vary. We show that seasonality can give rise to a cascade of period-doubling bifurcations leading to chaos for larger, though realistic, values of the amplitude of the seasonal variation of fertility.« less

The temporal patterns of disease severity and prevalence in schistosomiasis

NASA Astrophysics Data System (ADS)

Ciddio, Manuela; Mari, Lorenzo; Gatto, Marino; Rinaldo, Andrea; Casagrandi, Renato

2015-03-01

Schistosomiasis is one of the most widespread public health problems in the world. In this work, we introduce an eco-epidemiological model for its transmission and dynamics with the purpose of explaining both intra- and inter-annual fluctuations of disease severity and prevalence. The model takes the form of a system of nonlinear differential equations that incorporate biological complexity associated with schistosome's life cycle, including a prepatent period in snails (i.e., the time between initial infection and onset of infectiousness). Nonlinear analysis is used to explore the parametric conditions that produce different temporal patterns (stationary, endemic, periodic, and chaotic). For the time-invariant model, we identify a transcritical and a Hopf bifurcation in the space of the human and snail infection parameters. The first corresponds to the occurrence of an endemic equilibrium, while the latter marks the transition to interannual periodic oscillations. We then investigate a more realistic time-varying model in which fertility of the intermediate host population is assumed to seasonally vary. We show that seasonality can give rise to a cascade of period-doubling bifurcations leading to chaos for larger, though realistic, values of the amplitude of the seasonal variation of fertility.

Forest snail diversity and its environmental predictors along a sharp climatic gradient in southern Siberia

NASA Astrophysics Data System (ADS)

Horsák, Michal; Juřičková, Lucie; Horsáková, Veronika; Pokorná, Adéla; Pokorný, Petr; Šizling, Arnošt L.; Chytrý, Milan

2018-04-01

Diversity patterns of forest snail assemblages have been studied mainly in Europe. Siberian snail faunas have different evolutionary history and colonization dynamics than European faunas, but studies of forest snail diversity are almost missing from Siberia. Therefore, we collected snails at 173 forest sites in the Russian Altai and adjacent areas, encompassing broad variation in climate and forest types. We found 51 species, with a maximum of 15 and an average of seven species per site. The main gradient in species composition was related to soil pH, a variable that also positively correlates with snail abundances. The second gradient was associated with climate characteristics of winter. We observed significant differences in both species richness and composition among six forest types defined based on vegetation classification. Hemiboreal continental forests were the poorest of these types but hosted several species characteristic of European full-glacial stages of the Late Pleistocene. A high snow cover in Temperate coniferous and mixed forests, protecting the soil from freezing, allowed the frost-sensitive large-bodied (>10 mm) species to inhabit this forest type. In contrast to most of the European snail assemblages studied so far we found that the factors responsible for the variation in species richness differed from those driving species composition. This may be attributed to the sharp climatic gradient and the presence of the cold-adapted species typical of the Pleistocene cold stages. We suggest that southern Siberian forests hosting these species can serve as modern analogues of full-glacial forests in periglacial Central and Eastern Europe.

Evidence of host-associated divergence from coral-eating snails (genus Coralliophila) in the Coral Triangle

NASA Astrophysics Data System (ADS)

Simmonds, Sara E.; Chou, Vincent; Cheng, Samantha H.; Rachmawati, Rita; Calumpong, Hilconida P.; Ngurah Mahardika, G.; Barber, Paul H.

2018-06-01

We studied how host-associations and geography shape the genetic structure of sister species of marine snails Coralliophila radula (A. Adams, 1853) and C. violacea (Kiener, 1836). These obligate ectoparasites prey upon corals and are sympatric throughout much of their ranges in coral reefs of the tropical and subtropical Indo-Pacific. We tested for population genetic structure of snails in relation to geography and their host corals using mtDNA (COI) sequences in minimum spanning trees and AMOVAs. We also examined the evolutionary relationships of their Porites host coral species using maximum likelihood trees of RAD-seq (restriction site-associated DNA sequencing) loci mapped to a reference transcriptome. A maximum likelihood tree of host corals revealed three distinct clades. Coralliophila radula showed a pronounced genetic break across the Sunda Shelf ( Φ CT = 0.735) but exhibited no genetic structure with respect to host. C. violacea exhibited significant geographic structure ( Φ CT = 0.427), with divergence among Hawaiian populations, the Coral Triangle and the Indian Ocean. Notably, C. violacea showed evidence of ecological divergence; two lineages were associated with different groups of host coral species, one widespread found at all sites, and the other restricted to the Coral Triangle. Sympatric populations of C. violacea found on different suites of coral species were highly divergent ( Φ CT = 0.561, d = 5.13%), suggesting that symbiotic relationships may contribute to lineage diversification in the Coral Triangle.

DNA types of aspermic Fasciola species in Japan.

PubMed

Ichikawa, Madoka; Iwata, Noriyuki; Itagaki, Tadashi

2010-10-01

In order to reveal DNA types of aspermic Fasciola forms in Japan, Fasciola specimens obtained from eight prefectures that had not been previously reported were analyzed for DNA of ribosomal internal transcribed spacer 1 (ITS1) and mitochondrial NADH dehydrogenase 1 (ND1) gene. Five combinations in DNA types of both ITS1 and ND1 were revealed from the results of this study and previous studies. The DNA type Fsp2, which is identical to that of F. gigantica in both ITS1 and ND1, was the most predominant in Japan, followed by Fsp1, which is the same DNA type as that of F. hepatica. Fasciola forms with Fsp1 mainly occurred in the northern region of Japan and those with Fsp2 were mainly in the western region. The founder effect related to migration of definitive host and susceptibility of intermediate host snail might play an important role in both geographical distribution and frequency of DNA types in Japanese Fasciola specimens.

Within-population covariation between sexual reproduction and susceptibility to local parasites.

PubMed

Gibson, Amanda K; Xu, Julie Y; Lively, Curtis M

2016-09-01

Evolutionary biology has yet to reconcile the ubiquity of sex with its costs relative to asexual reproduction. Here, we test the hypothesis that coevolving parasites maintain sex in their hosts. Specifically, we examined the distributions of sexual reproduction and susceptibility to local parasites within a single population of freshwater snails (Potamopyrgus antipodarum). Susceptibility to local trematode parasites (Microphallus sp.) is a relative measure of the strength of coevolutionary selection in this system. Thus, if coevolving parasites maintain sex, sexual snails should be common where susceptibility is high. We tested this prediction in a mixed population of sexual and asexual snails by measuring the susceptibility of snails from multiple sites in a lake. Consistent with the prediction, the frequency of sexual snails was tightly and positively correlated with susceptibility to local parasites. Strikingly, in just two years, asexual females increased in frequency at sites where susceptibility declined. We also found that the frequency of sexual females covaries more strongly with susceptibility than with the prevalence of Microphallus infection in the field. In linking susceptibility to the frequency of sexual hosts, our results directly implicate spatial variation in coevolutionary selection in driving the geographic mosaic of sex. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Biological, biochemical and histological features of Bradybaena similaris (Gastropoda: Pulmonata) infected by Heterorabditis indica (Rhabditida: Heterorhabditidae) strain LPP1.

PubMed

Tunholi, Victor Menezes; Tunholi-Alves, Vinícius Menezes; Monteiro, Caio Oliveira; Silva, Lidiane Cristina da; Dolinski, Cláudia de Melo; Castro, Rosane Nora; Bittencourt, Vânia Rita Elias Pinheiro; Silva, Jairo Pinheiro da; Freire Martins, Isabella Vilhena

2017-08-01

This study investigated the possible biological, biochemical and histological changes in Bradybaena similaris(Gastropoda: Pulmonata) infected by Heterorhabditis indica (Rhabditida: Heterorhabditidae), strain LPP1. Two groups of 16 snails were formed: the control group (unexposed) and the treated group, which was exposed for three weeks to infective juveniles (J 3 ) of H. indica LPP1. The experiment was conducted in duplicate, using a total of 64 snails. After the exposure period, the snails were dissected to collect the hemolymph and tissues, for evaluation of the physiological changes caused by the infection. The number of eggs laid/snail and the viability of these eggs were also assessed as indicators of the reproductive activity of B. similaris. Intense glycogenolysis was accompanied by a significant reduction (p < 0.05) in the glucose content of the hemolymph of the exposed snails, indicating that infection by H. indica induces breakdown of the host's glycemic homeostasis. Significant variations (p < 0.05) in the lactate dehydrogenase activity occurred together with changes in the concentration of pyruvic and lactic acid in the hemolymph of the infected B. similaris snails, corroborating the transition from aerobic to anaerobic metabolism in the hosts. These metabolic alterations reflect the parasitic castration process in this interface. The results suggest that the use of H. indica LPP1 is a potential alternative for biological control of B. similaris. Copyright © 2017 Elsevier Inc. All rights reserved.

Assessment of the FasciMol-ELISA in the detection of the trematode Fasciola hepatica in field-collected Galba cubensis: a novel tool for the malacological survey of fasciolosis transmission.

PubMed

Alba, Annia; Vázquez, Antonio A; Sánchez, Jorge; Fraga, Jorge; Hernández, Hilda; Martínez, Elizabeth; Marcet, Ricardo; Figueredo, Mabel; Sarracent, Jorge

2016-01-16

Fasciolosis is one of the food-borne neglected trematodioses that has reemerged as a human disease while its effects on domestic animal health remains of significant economic consideration. Being snail-borne disease, the accurate and time-saving epidemiological surveillance of the transmission foci where infected lymnaeid snails occur could be essential to effectively focus or redirect control strategies. For this purpose, the first monoclonal antibody-based immunoenzymatic assay to detect Fasciola hepatica-infected snails (FasciMol-ELISA) was recently developed and showed a high sensitivity and specificity when tested in an experimental F. hepatica - Galba cubensis system. Here, we surveyed populations of G. cubensis occurring in western Cuba for the assessment of the FasciMol-ELISA in determining natural F. hepatica infection in this intermediate host. A multiplex PCR, previously developed to detect F. hepatica in G. cubensis, was used for sample classification. Snail dissection method was also employed as screening technique. A Χ(2) test and a Kappa index were calculated to evaluate the positivity and the level of agreement between the FasciMol-ELISA and the snail dissection methods with the multiplex PCR, respectively. Galba cubensis was found in nine out of 12 sampled localities of which four were positive for F. hepatica infection as detected by both immunoenzymatic and PCR-based assays. The overall prevalence was higher than the natural infection rates previously reported for Cuban G. cubensis (range from 4.1 to 7.42% depending on the screening method). No significant differences were found between FasciMol-ELISA and multiplex PCR when determining parasite positivity (Χ(2) = 6.283; P = 0.0981) whereas an excellent agreement was also noted (Kappa = 0.8224). Our results demonstrate the importance of malacological surveys in assessing parasite transmission risk and constitute an alert on the need of accurate measures to control fasciolosis in western Cuba. The sensitivity and specificity of the FasciMol-ELISA as well as its time-saving capacity and the easy of performing the determination of a large number of samples, point at this assay as a novel tool suitable for large-scale monitoring of natural snails populations. To our knowledge, this is the first study that explores natural infection by F. hepatica in field-occurring lymnaeid snails using an immunoenzymatic assay.

Renal trematode infection due to Paratanaisia bragai in zoo housed Columbiformes and a red bird-of-paradise (Paradisaea rubra).

PubMed

Unwin, Steve; Chantrey, Julian; Chatterton, James; Aldhoun, Jitka A; Littlewood, D Timothy J

2013-12-01

Trematode infections affect a diverse range of avian species and the organs that are parasitised are also very varied. The family Eucotylidae contains seven genera of renal flukes that parasitise various birds. In birds, mild to severe lesions have been reported for species of the genus Paratanaisia, which was originally described from columbiform and galliform specimens collected in South America and has been identified in a number of wild avian species. This paper investigates eight cases of renal trematode infection at Chester Zoo in the UK due to Paratanaisia bragai in five previously unreported species: red bird-of-paradise, Socorro dove, Mindanao bleeding heart dove, laughing dove and emerald dove. Pathological changes, which varied between species, are discussed. A known intermediate snail host Allopeas clavulinum was present in the enclosures but there was no direct evidence of trematode infection. The size of the snails, possible low prevalence and the difficulty of visualising sporocysts contributed to this. Thus the development and application of further molecular diagnostic markers that can be applied to snail tissues is warranted. Parasite identification was confirmed utilizing DNA amplification from formalin-fixed paraffin-embedded tissues using PCR and trematode specific primers. Sequencing full ssrDNA and D1-D3 lsrDNA confirmed the identity in all cases as P. bragai. However, the short 310 bp fragment used provides insufficient variation or sequence length for wider application. The epidemiology, pathology and consequences for the management of these endangered species are discussed. Preliminary work on developing an effective ante mortem diagnostic PCR test kit is also highlighted.

Molecular characterization of freshwater snails in the genus Bulinus: a role for barcodes?

PubMed Central

Kane, Richard A; Stothard, J Russell; Emery, Aidan M; Rollinson, David

2008-01-01

Background Reliable and consistent methods are required for the identification and classification of freshwater snails belonging to the genus Bulinus (Gastropoda, Planorbidae) which act as intermediate hosts for schistosomes of both medical and veterinary importance. The current project worked towards two main objectives, the development of a cost effective, simple screening method for the routine identification of Bulinus isolates and the use of resultant sequencing data to produce a model of relationships within the group. Results Phylogenetic analysis of the DNA sequence for a large section (1009 bp) of the mitochondrial gene cytochrome oxidase subunit 1 (cox1) for isolates of Bulinus demonstrated superior resolution over that employing the second internal transcribed spacer (its2) of the ribosomal gene complex. Removal of transitional substitutions within cox1 because of saturation effects still allowed identification of snails at species group level. Within groups, some species could be identified with ease but there were regions where the high degree of molecular diversity meant that clear identification of species was problematic, this was particularly so within the B. africanus group. Conclusion The sequence diversity within cox1 is such that a barcoding approach may offer the best method for characterization of populations and species within the genus from different geographical locations. The study has confirmed the definition of some accepted species within the species groups but additionally has revealed some unrecognized isolates which underlines the need to use molecular markers in addition to more traditional methods of identification. A barcoding approach based on part of the cox1 gene as defined by the Folmer primers is proposed. PMID:18544153

Some facts on south asian schistosomiasis and need for international collaboration.

PubMed

Agrawal, M C; Rao, V G

2018-04-01

In this review, we are discussing South Asian schistosomiasis; more specifically species which are responsible for schistosomiasis in India or South Asia -Schistosoma indicum, S. spindale, S. nasale, S. incognitum, S. gimvicum (S.haematobium), Bivitellobilharzia nairi, Orientobilharzia bomfordi, O. dattai, O. turkestanicum and O.harinasutai, their survival strategies such as mild pathology to the host, producing low egg number and utilizing fresh water snails (Indoplanorbis exustus and Lymnaea luteola) in stagnant water bodies like ponds, lakes, ditches, low laying areas, marshy lands and rice fields. Presently, correct identification of blood fluke species, their immature stages, male schistosomes and their intermediate host details like strain variations, susceptibilities, ecologies are not well studied. Species like B. nairi, O. bomfordi, O. harinasutai (Lymnaea rubiginosa intermediate host for O.harinasutai in Thailand) are also not well studied. Moreover, snail species like Oncomalania spp are not from South Asia, but species of Tricula or Neotricula are reported from this geography, which gives indications of S. mekongi like blood fluke presence in the area. Although in humans, cercarial dermatitis is rampant in rural population with occasional reporting of schistosome eggs in stools, human schistosomiasis is considered absent from this region, despite finding a foci (now dead) of urinary schistosomiasis in Gimvi village of Ratnagiri district, Maharashtra, India. There is great difficulty in diagnosing the infection in man and animals due to low egg production, hence development of a single step antigen detection test is the need of the hour. Interestingly, lethal effect of praziquantel was seen against S.haematobium and S.mansoni. However, this drug failed to cause significant reduction of S. incognitum and S. spindale experimentally suggesting some differences in the biology of two groups of the schistosomes. Triclabendazole showed adulticidal effect at a dose rate of 20 mg/kg body against female schistosome worms, but at lower dose (10 mg/kg body wt) of the drug, a dose that is used in treating bovine fascioliasis, it is providing chances of drug resistance of the persisting schistosomes against triclabendazole. Though the South Asian institutes have all the facilities to tackle issues related to existing schistosomes, it is recommended to develop an international collaboration by establishing an international centre on schistosomiasis in India. Copyright © 2017. Published by Elsevier B.V.

Model approaches for estimating the influence of time-varying socio-environmental factors on macroparasite transmission in two endemic regions

PubMed Central

ZHONG, BO; CARLTON, ELIZABETH J.; SPEAR, ROBERT C.

2009-01-01

The environmental determinants of vector- and host-borne diseases include time-varying components that modify key transmission parameters, resulting in transient couplings between environmental phenomena and transmission processes. While some time-varying drivers are periodic in nature, some are aperiodic, such as those that involve episodic events or complex patterns of human behavior. Understanding these couplings can allow for prediction of periods of peak infection risk, and ultimately presents opportunities for optimizing intervention selection and timing. Schistosome macroparasites of humans exhibit multiple free-living stages as well as intermediate hosts, and are thus model organisms for illustrating the influence of environmental forcing on transmission. Time-varying environmental factors, termed gating functions, for schistosomes include larval response to temperature and rainfall, seasonal water contact patterns and snail population dynamics driven by weather variables. The biological bases for these modifiers are reviewed, and their values are estimated and incorporated into a transmission model that simulates a multi-year period in two schistosomiasis endemic regions. Modeling results combined with a scale dependent correlation analysis indicate the end effect of these site-specific gating functions is to strongly govern worm burden in these communities, in a manner particularly sensitive to the hydrological differences between sites. Two classes of gating functions were identified, those that act in concert to modify human infection (and determine worm acquisition late in the season), and those that act on snail infection (and determine early season worm acquisition). The importance of these factors for control programs and surveillance is discussed. PMID:20454601

Morphological and molecular analyses of larval and adult stages of Echinoparyphium recurvatum von Linstow 1873 (Digenea: Echinostomatidae) from central Mexico.

PubMed

Sereno-Uribe, A L; Pinacho-Pinacho, C D; Sanchéz Cordero, V; García-Varela, M

2015-07-01

In central Mexico, populations of the freshwater snail Physella cubensis were infected with metacercariae from a species of Echinoparyphium (Digenea: Echinostomatidae). In the current study, we describe both larval and adult stages of this species obtained from experimental and natural infections. A total 180 snails were collected from Patzcuaro Lake, Michoacan state in central Mexico in July 2012. In the laboratory snails were placed in individual vials and exposed to light with the aim of observing emergence of cercariae. To obtain metacercariae, uninfected snails (P. cubensis) were exposed to cercariae. Chicks were infected with metacercariae to obtain adults. Nine days post-infection, eggs were recovered and incubated in tap water at room temperature to observe miracidia. Adults obtained from natural and experimentally infected hosts possess a head collar with 45 spines in two alternating rows, confirming the identification as Echinoparyphium recurvatum von Linstow 1873. To test the conspecificity of all stages, sequences of nuclear internal transcribed spacer 1 (ITS1), 5.8S and ITS2 rDNA were obtained from two adult worms recovered from chicks and also a natural avian host, the shoveler duck Anas clypeata, together with five cercarial and four metacercarial isolates from nine snails. The genetic divergence estimated among the 13 isolates was very low, ranging from 0 to 0.6%. Phylogenetic analyses inferred by maximum likelihood and Bayesian methods showed that all isolates of E. recurvatum form a single clade with strong support. The presence of E. recurvatum in P. cubensis and A. clypeata from central Mexico represents new host reports, and extends the distribution range in the Americas.

Small-sized euryhaline fish as intermediate hosts of the digenetic trematode Cryptocotyle concavum

NASA Astrophysics Data System (ADS)

Zander, C. D.; Kollra, H.-G.; Antholz, B.; Meyer, W.; Westphal, D.

1984-03-01

Cercariae of the trematode Cryptocotyle concavum, which encyst in skin and/or kidney of sticklebacks and gobies, were studied in the Schlei Fjord (western Baltic Sea). Mean incidence of dermal cysts was 48 % in Gasterosteus aculeatus and 37 % in Pungitius pungitius. No cysts were found in the kidneys of sticklebacks. While 97 % of Pomatoschistus microps had encysted metacercariae in the kidneys, only 2 % had cysts in the skin. Pomatoschistus minutus, however, showed hardly any cyst infestation of either skin or kidney. In P. microps the intensity of infestation by metacercariae was frequently more than 50 cysts; in contrast, sticklebacks rarely exhibited more than 5 dermal cysts. Infested fish were larger than 10 mm in total length, the incidence rate increasing with growth. Parasitic infestation depends on ambient salinity: C. concavum was not found at salinities below 4 ‰. In contrast to the high incidence in fish, the first hosts — the snails Hydrobia stagnalis and H. neglecta — showed remarkably low infection rates (3 to 5 %). The findings reported are related to the distribution of C. concavum, the mode of life of infested fish, the feeding habits of the final hosts and the infestation of P. microps by other parasites. Evidently, P. microps represents an optimal second host for C. concavum.

High intensity and prevalence of two species of trematode metacercariae in the fathead minnow (Pimephales promelas) with no compromise of minnow anti-predator competence.

PubMed

Wisenden, Brian D; Martinez-Marquez, Jorge Y; Gracia, Emilia S; McEwen, Daniel C

2012-08-01

Opportunity for parasites to manipulate host behavioral phenotype may be influenced by several factors, including the host ecology and the presence of cohabiting parasites in the same host. Metacercariae of Ornithodiplostomum ptychocheilus and "black spot" Crassiphiala bulboglossa have similar life cycles. Each parasite uses a littoral snail as a first intermediate host, fathead minnows as a second intermediate host, and a piscivorous bird as a final host. Metacercariae of black spot encyst in the dermal and epidermal tissues, while metacercariae of O. ptychocheilus encyst on the brain over a region that coordinates optomotor responses. Because of site differences within the host, we predicted that O. ptychocheilus metacercariae might manipulate the behavioral phenotype of minnows to facilitate transmission to the final host, but metacercariae of black spot would not. In our study population, prevalence was 100% for O. ptychocheilus , with an overall median intensity of 105 metacercariae per minnow. Prevalence of black spot was 60%, with a median abundance and intensity of 12 and 20 metacercariae per minnow for the overall sample and for infected fish, respectively. Minnows accumulated both parasites over time, producing significant correlations between intensity and minnow body length and between intensities of the 2 parasites. Minnows infected with black spot had on average twice as many O. ptychocheilus metacercariae as similar-sized minnows without any black spot cercariae. We found no correlation between body condition of minnows and intensity for either parasite. We measured 2 aspects of anti-predator competence to test for effects linked to parasite intensity. We found no correlation between intensity of either species of parasite and latency to behavioral response to attack from a mechanical model heron, nor was there any effect of parasite intensity on a measure of shoaling affinity. The absence of any detectable effect of metacercariae on anti-predator competence in minnows may reflect selection against parasite pathology from predation by non-hosts of the parasites and overwinter mortality due to low dissolved oxygen.

High molecular weight lectin isolated from the mucus of the giant African snail Achatina fulica.

PubMed

Ito, Shigeru; Shimizu, Masahiro; Nagatsuka, Maki; Kitajima, Seiji; Honda, Michiyo; Tsuchiya, Takahide; Kanzawa, Nobuyuki

2011-01-01

To understand better the host defense mechanisms of mollusks against pathogens, we examined the anti-microbial activity of mucus from the giant African snail Achatina fulica. Hemagglutination activity of the mucus secreted by the integument of snails inoculated with Escherichia coli was observed to increase and to cause hemagglutination of rabbit red blood cells. Purification of the snail mucus lectin by sequential column chromatography revealed that the relative molecular mass of the lectin was 350 kDa. The hemagglutination activity of the lectin was Ca(2+)-dependent and was inhibited by galactose. Growth arrest tests showed that the lectin did not inhibit bacterial growth, but did induce agglutination of gram-positive and gram-negative bacteria. Tissue distribution analyses using a polyclonal antibody revealed that the lectin was expressed in the tissues of the mantle collar. The lectin isolated from the mucus of the snail appeared to contribute to its innate immunity.

The potential use of ultrasound to control the trematode bolbophorus confusus by eliminating the ram's horn snail planorbella trivolvis in commercial aquaculture settings

USDA-ARS?s Scientific Manuscript database

One method in the investigation of acoustics to improve aquaculture production is the use of ultrasound to control the trematode, Bolbophorus confuses, in commercial catfish ponds. The trematode population can be controlled by eliminating the host ram’s horn snail, Planorbella trivolvis, which is ty...

Concentration and retention of Toxoplasma gondii surrogates from seawater by red abalone (Haliotis rufescens).

PubMed

Schott, Kristen C; Krusor, Colin; Tinker, M Tim; Moore, James; Conrad, Patricia A; Shapiro, Karen

2016-11-01

Small marine snails and abalone have been identified as high- and low-risk prey items, respectively, for exposure of threatened southern sea otters to Toxoplasma gondii, a zoonotic parasite that can cause fatal encephalitis in animals and humans. While recent work has characterized snails as paratenic hosts for T. gondii, the ability of abalone to vector the parasite has not been evaluated. To further elucidate why abalone predation may be protective against T. gondii exposure, this study aimed to determine whether: (1) abalone are physiologically capable of acquiring T. gondii; and (2) abalone and snails differ in their ability to concentrate and retain the parasite. Abalone were exposed to T. gondii surrogate microspheres for 24 h, and fecal samples were examined for 2 weeks following exposure. Concentration of surrogates was 2-3 orders of magnitude greater in abalone feces than in the spiked seawater, and excretion of surrogates continued for 14 days post-exposure. These results indicate that, physiologically, abalone and snails can equally vector T. gondii as paratenic hosts. Reduced risk of T. gondii infection in abalone-specializing otters may therefore result from abalone's high nutritional value, which implies otters must consume fewer animals to meet their caloric needs.

Molluscicidal activity of Manilkara subsericea (Mart.) dubard on Biomphalaria glabrata (Say, 1818).

PubMed

Faria, Robson Xavier; Rocha, Leandro Machado; Souza, Eloísa Portugal Barros Silva Soares; Almeida, Fernanda Borges; Fernandes, Caio Pinho; Santos, José Augusto Albuquerque

2018-02-01

Schistosomiasis is promoted for species from Schistosoma genus affecting over 200 million people worldwide. Molluscicides are an efficient method to control this disease, being able to reduce intermediate host snail Biomphalaria glabrata number. In function of resistance cases using niclosamide, natural products are promisors to discover new drugs. Manilkara subsericea is endemic to Brazilian sandbanks of Rio de Janeiro State and wide ranges of biological activities. However, there is no studies evaluating its effects as molluscicidal agent. We tested crude extract from leaves of M. subsericea molluscicidal action, as well it ethyl-acetate fraction and isolated substances against B. glabrata. M. subsericea leaves crude extract and ethyl acetate fraction induced 80±4.13% and 86.66±4.59% mortality of adult snails at concentrations of 250ppm after 96h, and their LD 50 values were 118.7±1.62 and 23.41±1.15ppm respectively. Isolated substances from M. subsericea were also considered active. Quercetin, myricetin and ursolic acid, at concentration of 100ppm (96h), were able to induce mortality levels of 100%, 80% and 53.33%, respectively. Our results suggest that M. subsericea can be considered promising as a molluscicide agent. Copyright © 2017. Published by Elsevier B.V.

Molluscicidal action of the latex of Euphorbia splendens var. hislopii N.E.B. ("Christ's Crown") (Euphorbiaceae) against Lymnaea columella (Say, 1817) (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica Linnaeus, 1758 (Trematode: Fasciolidae): 1- test in laboratory.

PubMed

de Vasconcellos, Mauricio Carvalho; de Amorim, Alziro

2003-06-01

The latex action of Euphorbia splendens var. hislopii (Christ's Crown) against snails Lymnaea columella, intermediate host of Fasciola hepatica, derived from irrigation ditches of the Station of Pisciculture at Universidade Federal Rural do Rio de Janeiro, was studied in the laboratory. Lab bioassays, using aqueous solutions of the latex, varying between 0.1 and 10 mg/l, have proven molluscicidal activity of the product collected on the same day the tests were performed, during the four seasons of the year, finding the following lethal concentrations (LC90): 1.51 mg/l in the spring; 0.55 mg/l in the summer; 0.74 mg/l in the fall and 0.93 mg/l in winter, after 24 h exposure of the snails, showing significant differences among the seasons of the year (ANOVA test, F = 11.01, G.L.= 3/33, p < 0.05), as well as among the concentrations (ANOVA test, F = 27.38, G.L.= 11/33, p < 0.05). In the summer, mortality reached 100% from concentration at 0.6 mg/l, the same during fall and in winter as of 1 mg/l, while in spring it only reached 100% mortality as of 2 mg/l. Mortality in the controls was low, reaching 5% in the summer and winter and 10% in the fall and spring. None of the samples died. During the assay, with an aqueous solution of the latex at a concentration of 5 mg/l, in order to check the time of duration of the product effect, in the laboratory, it was observed that the molluscicidal activity remained stable up to the 15th day after the beginning of the test with 100% mortality of L. columella, gradually losing its effect until the 23rd day, when we no longer observed animal mortality. In the control group, there was a random daily variation in mortality rate ranging 0-50% after 48 h of observation for 30 days.

The parasitic castration and gigantism of Lymnaea truncatula infected with the larval stages of Fasciola hepatica.

PubMed

Wilson, R A; Denison, J

1980-01-01

The shells of Lymnaea truncatula infected with the larval stages of Fasciola hepatica were significantly longer than those of comparable uninfected controls. The dry mass (tissue, shell + parasite) of the same infected snails, 56 days after infection, was approximately twice that of the controls (tissue + shell). The increased mass of infected snails was not due to a disproportionate increase in shell weight relative to tissues. Infected snails maintained at 20 degrees C had virtually ceased egg production by 21 days post-infection whereas control snails continued to lay eggs steadily for the duration of the experiment. The dry mass of snail tissue plus the cumulative dry weight of eggs produced was taken as an indication of the ability of control snails to generate biomass. Similarly the tissue mass plus cumulative egg weight and parasite weight was taken as an indication of the ability of the infected snails to generate biomass. The control and infected snails were not significantly different in this respect indicating that the gigantism of infected snails could be the result of a switch in nutrient supply from reproduction to somatic tissue growth and parasite growth. Castration was brought about 17-21 days after infection as a result of the direct consumption of the ovotestis by a proportion of the redial population. In a separate experiment it was demonstrated that a population of infected snails maintained at 20 degrees C survived as long as a similar group of control snails. The findings with this host-parasite system are discussed in relation to possible mechanisms causing castration and gigantism in other digene-snail interactions, and in relation to parasitic castration in other groups. It is concluded that the observed gigantism of infected snails is more likely to have a nutritional rather than endocrine origin.

Cost of resistance to trematodes in freshwater snail populations with low clonal diversity.

PubMed

Dagan, Yael; Kosman, Evsey; Ben-Ami, Frida

2017-12-13

The persistence of high genetic variability in natural populations garners considerable interest among ecologists and evolutionary biologists. One proposed hypothesis for the maintenance of high levels of genetic diversity relies on frequency-dependent selection imposed by parasites on host populations (Red Queen hypothesis). A complementary hypothesis suggests that a trade-off between fitness costs associated with tolerance to stress factors and fitness costs associated with resistance to parasites is responsible for the maintenance of host genetic diversity. The present study investigated whether host resistance to parasites is traded off with tolerance to environmental stress factors (high/low temperatures, high salinity), by comparing populations of the freshwater snail Melanoides tuberculata with low vs. high clonal diversity. Since polyclonal populations were found to be more parasitized than populations with low clonal diversity, we expected them to be tolerant to environmental stress factors. We found that clonal diversity explained most of the variation in snail survival under high temperature, thereby suggesting that tolerance to high temperatures of clonally diverse populations is higher than that of populations with low clonal diversity. Our results suggest that resistance to parasites may come at a cost of reduced tolerance to certain environmental stress factors.

Habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus (Müller, 1774).

PubMed

Giovanelli, Alexandre; da Silva, Cesar Luiz Pinto Ayres Coelho; Leal, Geórgia Borges Eccard; Baptista, Darcílio Fernandes

2005-04-01

Our objective is to evaluate the habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus. In the first phase, snails was collected at 12 sites. This sampling sites presented a degree of organic input. In the second phase 33 sampling sites were chosen, covering a variety of lotic and lentic environments. The snail species found at Guapimirim, state of Rio de Janeiro, displayed a marked habitat preference, specially in relation to the physical characteristics of each environment. Other limiting factors for snail distribution at the studied lotic environments were the water current velocity and the amount of organic matter, mainly to Physa marmorata, M. tuberculatus, and Biomphalaria tenagophila. The absence of interactions between M. tuberculatus and another snails could be associated to the distinct spatial distribution of those species and the instability of habitats. This later factor may favor the coexistence of M. tuberculatus with B. glabrata by reduction of population density. In areas of schistosomiasis transmission some habitat modification may add to the instability of the environment, which would make room for the coexistence of M. tuberculatus and Biomphalaria spp. In this way, some of the usual measures for the control of snail hosts would prevent the extinction of populations of Biomphalaria spp. by M. tuberculatus in particular habitats.

Concentration and retention of Toxoplasma gondii oocysts by marine snails demonstrate a novel mechanism for transmission of terrestrial zoonotic pathogens in coastal ecosystems

USGS Publications Warehouse

Krusor, Colin; Smith, Woutrina A.; Tinker, M. Tim; Silver, Mary; Conrad, Patricia A.; Shapiro, Karen

2015-01-01

The parasite Toxoplasma gondii is an environmentally persistent pathogen that can cause fatal disease in humans, terrestrial warm-blooded animals and aquatic mammals. Although an association between T. gondii exposure and prey specialization on marine snails was identified in threatened California sea otters, the ability of kelp-dwelling snails to transmit terrestrially derived pathogens has not been previously investigated. The objective of this study was to measure concentration and retention of T. gondii by marine snails in laboratory aquaria, and to test for natural T. gondii contamination in field-collected snails. Following exposure to T. gondii-containing seawater, oocysts were detected by microscopy in snail faeces and tissues for 10 and 3 days respectively. Nested polymerase chain reaction was also applied as a method for confirming putative T. gondii oocysts detected in snail faeces and tissues by microscopy. Toxoplasma gondiiwas not detected in field-collected snails. Results suggest that turban snails are competent transport hosts for T. gondii. By concentrating oocysts in faecal pellets, snails may facilitate entry of T. gondii into the nearshore marine food web. This novel mechanism also represents a general pathway by which marine transmission of terrestrially derived microorganisms can be mediated via pathogen concentration and retention by benthic invertebrates.

An experimental heat wave changes immune defense and life history traits in a freshwater snail.

PubMed

Leicht, Katja; Jokela, Jukka; Seppälä, Otto

2013-12-01

The predicted increase in frequency and severity of heat waves due to climate change is expected to alter disease dynamics by reducing hosts' ability to resist infections. This could take place via two different mechanisms: (1) through general reduction in hosts' performance under harsh environmental conditions and/or (2) through altered resource allocation that reduces expression of defense traits in order to maintain other traits. We tested these alternative hypotheses by measuring the effect of an experimental heat wave (25 vs. 15°C) on the constitutive level of immune defense (hemocyte concentration, phenoloxidase [PO]-like activity, antibacterial activity of hemolymph), and life history traits (growth and number of oviposited eggs) of the great pond snail Lymnaea stagnalis. We also manipulated the exposure time to high temperature (1, 3, 5, 7, 9, or 11 days). We found that if the exposure to high temperature lasted <1 week, immune function was not affected. However, when the exposure lasted longer than that, the level of snails' immune function (hemocyte concentration and PO-like activity) was reduced. Snails' growth and reproduction increased within the first week of exposure to high temperature. However, longer exposures did not lead to a further increase in cumulative reproductive output. Our results show that short experimental heat waves do not alter immune function but lead to plastic responses that increase snails' growth and reproduction. Thus, although the relative expression of traits changes, short experimental heat waves do not impair snails' defenses. Negative effects on performance get pronounced when the heat waves are prolonged suggesting that high performance cannot be maintained over long time periods. This ultimately reduces the levels of defense traits.

Renal trematode infection due to Paratanaisia bragai in zoo housed Columbiformes and a red bird-of-paradise (Paradisaea rubra)☆

PubMed Central

Unwin, Steve; Chantrey, Julian; Chatterton, James; Aldhoun, Jitka A.; Littlewood, D. Timothy J.

2012-01-01

Trematode infections affect a diverse range of avian species and the organs that are parasitised are also very varied. The family Eucotylidae contains seven genera of renal flukes that parasitise various birds. In birds, mild to severe lesions have been reported for species of the genus Paratanaisia, which was originally described from columbiform and galliform specimens collected in South America and has been identified in a number of wild avian species. This paper investigates eight cases of renal trematode infection at Chester Zoo in the UK due to Paratanaisia bragai in five previously unreported species: red bird-of-paradise, Socorro dove, Mindanao bleeding heart dove, laughing dove and emerald dove. Pathological changes, which varied between species, are discussed. A known intermediate snail host Allopeas clavulinum was present in the enclosures but there was no direct evidence of trematode infection. The size of the snails, possible low prevalence and the difficulty of visualising sporocysts contributed to this. Thus the development and application of further molecular diagnostic markers that can be applied to snail tissues is warranted. Parasite identification was confirmed utilizing DNA amplification from formalin-fixed paraffin-embedded tissues using PCR and trematode specific primers. Sequencing full ssrDNA and D1-D3 lsrDNA confirmed the identity in all cases as P. bragai. However, the short 310 bp fragment used provides insufficient variation or sequence length for wider application. The epidemiology, pathology and consequences for the management of these endangered species are discussed. Preliminary work on developing an effective ante mortem diagnostic PCR test kit is also highlighted. PMID:24533313

Update on trematode infections in sheep.

PubMed

Rojo-Vázquez, F A; Meana, A; Valcárcel, F; Martínez-Valladares, M

2012-09-30

Trematode parasites live in the liver, fore stomachs or blood vessels of a wide range of animals and humans. Most of them have a special economic and veterinary significance. Liver fluke disease of sheep and other animal species is caused by the common liver fluke Fasciola hepatica. Hepatic fasciolosis occurs throughout the world, where climatic conditions are suitable for the survival of aquatic intermediate host snails. Also of importance for ruminants, in some parts of the world, are Fasciola gigantica and Fascioloides magna. Other trematodes infecting ruminants include Dicrocoelium dendriticum; Eurytrema pancreaticum and Eurytrema coelomaticum. Among the Paramphistomidae, some species can infect sheep and other ruminants. Finally, Schistosoma spp. are found in the blood vessels of ruminants and are of minor importance in temperate regions. The manuscript concentrates on trematode species of veterinary importance for domestic sheep. Published by Elsevier B.V.

The South-American distribution and southernmost record of Biomphalaria peregrina—a potential intermediate host of schistosomiasis

PubMed Central

2017-01-01

Schistosomiasis remains a major parasitic disease, endemic in large parts of South America. Five neotropical species of Biomphalaria have been found to act as intermediate hosts of Schistosoma mansoni in natural populations, while others have been shown to be susceptible in experimental infections, although not found infected in the field. Among these potential intermediate hosts, Biomphalaria peregrina represents the most widespread species in South America, with confirmed occurrence records from Venezuela to northern Patagonia. In this study, we report the southernmost record for the species at the Pinturas River, in southern Patagonia, which finding implies a southward reassessment of the limit for the known species of this genus. The identities of the individuals from this population were confirmed through morphological examination, and by means of two mitochondrial genes, cytochrome oxidase subunit I (COI) and 16S-rRNA. With both markers, phylogenetic analyses were conducted in order to compare the genetic background of individuals from the Pinturas River with previously genetically characterized strains of B. peregrina from various South-American locations. In addition, we produced a potential distribution model of B. peregrina in South America and identified the environmental variables that best predict that distribution. The model was estimated through a maximum entropy algorithm and run with occurrence points obtained from several sources, including the scientific literature and international databases, along with climatic and hydrographic variables. Different phylogenetic analyses with either the COI or 16S-rRNA sequences did not conflict, but rather gave very similar topological organizations. Two major groups were identified, with sequences from the Pinturas River grouping together with haplotypes from subtropical and temperate regions. The model developed had a satisfactory performance for the study area. We observed that the areas with higher habitat suitability were found to be mainly linked to subtropical and temperate regions of South America between 15° and 45° south latitude, with different moderate- and low-suitability areas outside this range. We also identified the coldest temperatures as the main predictors of the potential distribution of this snail. Susceptibility surveys would be required to evaluate if southern populations of B. peregrina still retain their potential as intermediate hosts of S. mansoni. PMID:28584726

Interactions between freshwater snails and tadpoles: competition and facilitation.

PubMed

Brönmark, Christer; Rundle, Simon D; Erlandsson, Ann

1991-06-01

Freshwater snails and anuran tadpoles have been suggested to have their highest population densities in ponds of intermediate size where abiotic disturbance (e.g. desiccation) is low and large predators absent. Both snails and tadpoles feed on periphytic algae and, thus, there should be a large potential for competitive interactions to occur between these two distantly related taxa. In a field experiment we examined the relative strength of competition between two closely related snail species, Lymnaea stagnalis and L. peregra, and between L. stagnalis and tadpoles of the common frog, Rana temporaria. Snail growth and egg production and tadpole size at and time to metamorphosis were determined. Effects on the common food source, periphyton, were monitored with the aid of artificial substrates. Periphyton dry weight was dramatically reduced in the presence of snails and/or tadpoles. There were no competitive effects on growth or egg production of the two snail species when they were coexisting. Mortality of L. peregra was high (95%) after reproduction, but independent of treatment. Growth of L. stagnalis was reduced only at the highest tadpole densities, whereas egg production was reduced both by intraspecific competition and by competition with tadpoles. Differences in egg production were retained after tadpole metamorphosis. Tadpole larval period increased, weight of metamorphosing frogs decreased and growth rate was reduced as a function of increasing tadpole density. However, contrary to expectation, snails had a positive effect on tadpole larval period, weight and growth rate. Further, in experimental containers without snails there was a dense growth of the filamentous green alga Cladophora sp. We suggest that the facilitative effects of snails on tadpoles are due to an "indirect mutualistic" mechanism, involving competition between food sources of different quality (microalgae and Cladophora sp.) and tadpoles being competitively dominant over snails for the preferred food source (microalgae). In the presence of tadpoles snails will be forced to feed on low-quality Cladophora, increasing nutrient turnover rates, which results in enhanced productivity of microalgae, increasing tadpole food resources. Thus, tadpoles have a negative effect on snails through resource depression, while snails facilitate tadpole growth through an indirect enhancement of food availability.

Concentration and retention of Toxoplasma gondii surrogates from seawater by red abalone (Haliotis rufescens)

USGS Publications Warehouse

Schott, Kristen C; Krusor, Colin; Tinker, M. Tim; Moore, James G.; Conrad, Patricia A.; Shapiro, Karen

2016-01-01

Small marine snails and abalone have been identified as high- and low-risk prey items, respectively, for exposure of threatened southern sea otters to Toxoplasma gondii, a zoonotic parasite that can cause fatal encephalitis in animals and humans. While recent work has characterized snails as paratenic hosts for T. gondii, the ability of abalone to vector the parasite has not been evaluated. To further elucidate why abalone predation may be protective against T. gondii exposure, this study aimed to determine whether: (1) abalone are physiologically capable of acquiring T. gondii; and (2) abalone and snails differ in their ability to concentrate and retain the parasite. Abalone were exposed to T. gondii surrogate microspheres for 24 h, and fecal samples were examined for 2 weeks following exposure. Concentration of surrogates was 2–3 orders of magnitude greater in abalone feces than in the spiked seawater, and excretion of surrogates continued for 14 days post-exposure. These results indicate that, physiologically, abalone and snails can equally vector T. gondii as paratenic hosts. Reduced risk of T. gondii infection in abalone-specializing otters may therefore result from abalone's high nutritional value, which implies otters must consume fewer animals to meet their caloric needs.

Spread of the Rat Lungworm (Angiostrongylus cantonensis) in Giant African Land Snails (Lissachatina fulica) in Florida, USA.

PubMed

Iwanowicz, Deborah D; Sanders, Lakyn R; Schill, W Bane; Xayavong, Maniphet V; da Silva, Alexandre J; Qvarnstrom, Yvonne; Smith, Trevor

2015-07-01

The rat lungworm (Angiostrongylus cantonensis) is a parasitic nematode that causes rat lungworm disease. It is the leading cause of eosinophilic meningitis and is a zoonotic health risk. We confirmed the presence of A. cantonensis using species-specific, quantitative PCR in 18 of 50 (36%) giant African land snails (Lissachatina fulica) collected from Miami, Florida, US in May 2013. These snails were collected from seven of 21 core areas that the Florida Department of Agriculture and Consumer Services monitor weekly. Rat lungworms have not previously been identified in these areas. Duplicate DNA extractions of foot muscle tissue from each snail were tested. Of the seven core areas we examined, six were positive for A. cantonensis and prevalence of infection ranged from 27% to 100%. Of the 18 positive snails, only five were positive in both extractions. Our results confirm an increase in the range and prevalence of rat lungworm infection in Miami. We also emphasize the importance of extracting sufficient host tissue to minimize false negatives.

Spread of the Rat Lungworm (Angiostrongylus cantonensis) in Giant African Land Snails (Lissachatina fulica) in Florida, USA

USGS Publications Warehouse

Iwanowicz, Deborah; Sanders, Lakyn R.; Schill, W. Bane; Xayavong, Maniphet V; da Silva, Alexandre J; Qvarnstrom, Yvonne; Smith, Trevor

2015-01-01

The rat lungworm (Angiostrongylus cantonensis) is a parasitic nematode that causes rat lungworm disease. It is the leading cause of eosinophilic meningitis and is a zoonotic health risk. We confirmed the presence of A. cantonensis using species-specific, quantitative PCR in 18 of 50 (36%) giant African land snails (Lissachatina fulica) collected from Miami, Florida in May 2013. These snails were collected from seven of 21 core areas that the Florida Department of Agriculture and Consumer Services monitor weekly. Rat lungworms have not previously been identified in these areas. Duplicate DNA extractions of foot muscle tissue from each snail were tested. Of the seven core areas we examined, six were positive for A. cantonensis and prevalence of infection ranged from 27% to 100%. Of the 18 positive snails, only five were positive in both extractions. Our results confirm an increase in the range and prevalence of rat lungworm infection in Miami. We also emphasize the importance of extracting sufficient host tissue to minimize false negatives.

CCL2 is critical for immunosuppression to promote cancer metastasis.

PubMed

Kudo-Saito, Chie; Shirako, Hiromi; Ohike, Misa; Tsukamoto, Nobuo; Kawakami, Yutaka

2013-04-01

We previously found that cancer metastasis is accelerated by immunosuppression during Snail-induced epithelial-to-mesenchymal transition (EMT). However, the molecular mechanism still remained unclear. Here, we demonstrate that CCL2 is a critical determinant for both tumor metastasis and immunosuppression induced by Snail(+) tumor cells. CCL2 is significantly upregulated in various human tumor cells accompanied by Snail expression induced by snail transduction or TGFβ treatment. The Snail(+) tumor-derived CCL2 amplifies EMT events in other cells including Snail(-) tumor cells and epithelial cells within tumor microenvironment. CCL2 secondarily induces Lipocalin 2 (LCN2) in the Snail(+) tumor cells in an autocrine manner. CCL2 and LCN2 cooperatively generate immunoregulatory dendritic cells (DCreg) having suppressive activity accompanied by lowered expression of costimulatory molecules such as HLA-DR but increased expression of immunosuppressive molecules such as PD-L1 in human PBMCs. The CCL2/LCN2-induced DCreg cells subsequently induce immunosuppressive CD4(+)FOXP3(+) Treg cells, and finally impair tumor-specific CTL induction. In murine established tumor model, however, CCL2 blockade utilizing the specific siRNA or neutralizing mAb significantly inhibits Snail(+) tumor growth and metastasis following systemic induction of anti-tumor immune responses in host. These results suggest that CCL2 is more than a chemoattractant factor that is the significant effector molecule responsible for immune evasion of Snail(+) tumor cells. CCL2 would be an attractive target for treatment to eliminate cancer cells via amelioration of tumor metastasis and immunosuppression.

In vivo efficacy of praziquantel against Echinoparyphium aconiatum (Trematoda: Echinostomatidae) parasitizing the great pond snails Lymnaea stagnalis (Gastropoda: Lymnaeidae).

PubMed

Voutilainen, Ari

2011-09-01

The present study had a practical goal. I aimed to determine whether praziquantel could reduce the production of Echinoparyphium aconiatum (Trematoda: Echinostomatidae) cercariae in infected snails Lymnaea stagnalis (Gastropoda: Lymnaeidae) without killing the hosts. Praziquantel is a broad-spectrum antihelminth agent. It caused a total cessation of cercaria shedding when the praziquantel concentration in the treatment bath was 10 mg/L and the treatment time was 30 h or longer. A next research step which has to be taken before giving detailed recommendations about using praziquantel for ceasing production of E. aconiatum cercariae in parasitized snails is to follow the survivorship and performance of treated snails after a praziquantel exposure for longer than in this medium-term (3 days) experiment. Copyright © 2011 Elsevier Inc. All rights reserved.

The role of the immunological background of mice in the genetic variability of Schistosoma mansoni as detected by random amplification of polymorphic DNA.

PubMed

Cossa-Moiane, I L; Mendes, T; Ferreira, T M; Mauricio, I; Calado, M; Afonso, A; Belo, S

2015-11-01

Schistosomiasis is a parasitic disease caused by flatworms of the genus Schistosoma. Among the Schistosoma species known to infect humans, S. mansoni is the most frequent cause of intestinal schistosomiasis in sub-Saharan Africa and South America: the World Health Organization estimates that about 200,000 deaths per year result from schistosomiasis in sub-Saharan Africa alone. The Schistosoma life cycle requires two different hosts: a snail as intermediate host and a mammal as definitive host. People become infected when they come into contact with water contaminated with free-living larvae (e.g. when swimming, fishing, washing). Although S. mansoni has mechanisms for escaping the host immune system, only a minority of infecting larvae develop into adults, suggesting that strain selection occurs at the host level. To test this hypothesis, we compared the Belo Horizonte (BH) strain of S. mansoni recovered from definitive hosts with different immunological backgrounds using random amplification of polymorphic DNA-polymerase chain reaction (RAPD-PCR). Schistosoma mansoni DNA profiles of worms obtained from wild-type (CD1 and C57BL/6J) and mutant (Jα18- / - and TGFβRIIdn) mice were analysed. Four primers produced polymorphic profiles, which can therefore potentially be used as reference biomarkers. All male worms were genetically distinct from females isolated from the same host, with female worms showing more specific fragments than males. Of the four host-derived schistosome populations, female and male adults recovered from TGFβRIIdn mice showed RAPD-PCR profiles that were most similar to each other. Altogether, these data indicate that host immunological backgrounds can influence the genetic diversity of parasite populations.

First molecular identification of Australapatemon burti (Miller, 1923) (Trematoda: Digenea: Strigeidae) from an intermediate host Radix labiata (Rossmaessler) (Gastropoda: Lymnaeidae) in Europe.

PubMed

Aksenova, Olga V; Bespalaya, Yulia V; Bolotov, Ivan N; Kondakov, Alexander V; Sokolova, Svetlana E

2016-07-01

The strigeid digenean species Australapatemon burti (Miller, 1923) (Trematoda: Digenea: Strigeidae) was originally described from North America, but recorded in the Neotropical region (Drago et al. 2007; Hernández-Mena et al. 2014; Blasco-Costa et al. 2016) and in Central Europe (Faltýnková et al. 2007). In Europe, this species is rare, and there is not much information about its range (Faltýnková et al. 2007; Soldánová et al. 2012). Australapatemon burti has a complex life cycle with three larval stages, two of which (sporocyst and cercaria) use several species of freshwater snails, and the third stage (metacercaria) use non-specific host hirudineans (Dubois 1968; Davies & Ostrowski de Núñez 2012; Blasco-Costa et al. 2016). Adult flukes are parasitic in the intenstines of various waterfowl species, such as ducks and swans (Drago et al. 2007; Hernández-Mena et al. 2014). Currently, the molecular data on this parasite species includes only nucleotide sequences of four adult specimens from Mexico (Hernández-Mena et al. 2014). Their hosts were Mexican duck, Anas diazi Ridgway, American Wigeon, Anas americana Gmelin, Cinnamon Teal, Anas cyanoptera Vieillot, and Ruddy Duck, Oxyura jamaicensis (Gmelin) (Anserformes: Anatidae).

Evidence of a species complex within the food-borne trematode Opisthorchis viverrini and possible co-evolution with their first intermediate hosts.

PubMed

Saijuntha, Weerachai; Sithithaworn, Paiboon; Wongkham, Sopit; Laha, Thewarach; Pipitgool, Vichit; Tesana, Smarn; Chilton, Neil B; Petney, Trevor N; Andrews, Ross H

2007-05-01

The food-borne trematodes, Opisthorchis viverrini, O. felineus and Clonorchis sinensis, have long been recognized as the cause of major human health problems, with an estimated 40 million infected persons. Of the three species of liver fluke, only O. viverrini is classified as a type 1 carcinogen because of its role as an initiator of chronic inflammation and the subsequent development of cholangiocarcinoma. At present, there are no techniques for the early diagnosis of cholangiocarcinoma and it is fatal for most patients. There is considerable variation in parasite prevalence and disease presentation in different geographical areas, the latter of which may be associated with genetic differences among parasites. In the present study, multilocus enzyme electrophoresis was used to provide a comprehensive genetic characterization of O. viverrini from different geographical localities in Thailand and the Peoples' Democratic Republic of Laos. Parasites from different localities were compared genetically at 32 enzyme loci. The results of the genetic analyses are sufficient to reject the null hypothesis that O. viverrini represents a single species. Therefore, O. viverrini consists of at least two genetically distinct, yet morphologically similar (i.e. cryptic) species. Moreover, there was also separation of the different populations of snails (i.e. the first intermediate hosts) into two distinct genetic groups that corresponded with the delineation of O. viverrini into two species. This suggests that there may be a history of co-evolution in this host-parasite lineage. Additionally, five distinct genetic groups of parasites were detected, each of which occurred within a different and independent river wetland system. Our findings have major implications for the implementation of effective control and surveillance programs targeted to these medically important food-borne parasites.

Morphological and molecular characterization of lymnaeid snails and their potential role in transmission of Fasciola spp. in Vietnam.

PubMed

Dung, Bui Thi; Doanh, Pham Ngoc; The, Dang Tat; Loan, Ho Thi; Losson, Bertrand; Caron, Yannick

2013-12-01

Freshwater snails of the family Lymnaeidae play an important role in the transmission of fascioliasis worldwide. In Vietnam, 2 common lymnaeid species, Lymnaea swinhoei and Lymnaea viridis, can be recognized on the basis of morphology, and a third species, Lymnaea sp., is known to exist. Recent studies have raised controversy about their role in transmission of Fasciola spp. because of confusion in identification of the snail hosts. The aim of this study is, therefore, to clarify the identities of lymnaeid snails in Vietnam by a combination of morphological and molecular approaches. The molecular analyses using the second internal transcribed spacer (ITS2) of the nuclear ribosomal DNA clearly showed that lymnaeids in Vietnam include 3 species, Austropeplea viridis (morphologically identified as L. viridis), Radix auricularia (morphologically identified as L. swinhoei) and Radix rubiginosa (morphologically identified as Lymnaea sp.). R. rubiginosa is a new record for Vietnam. Among them, only A. viridis was found to be infected with Fasciola spp. These results provide a new insight into lymnaeid snails in Vietnam. Identification of lymnaeid snails in Vietnam and their role in the liver fluke transmission should be further investigated.

Morphological and Molecular Characterization of Lymnaeid Snails and Their Potential Role in Transmission of Fasciola spp. in Vietnam

PubMed Central

Doanh, Pham Ngoc; The, Dang Tat; Loan, Ho Thi; Losson, Bertrand; Caron, Yannick

2013-01-01

Freshwater snails of the family Lymnaeidae play an important role in the transmission of fascioliasis worldwide. In Vietnam, 2 common lymnaeid species, Lymnaea swinhoei and Lymnaea viridis, can be recognized on the basis of morphology, and a third species, Lymnaea sp., is known to exist. Recent studies have raised controversy about their role in transmission of Fasciola spp. because of confusion in identification of the snail hosts. The aim of this study is, therefore, to clarify the identities of lymnaeid snails in Vietnam by a combination of morphological and molecular approaches. The molecular analyses using the second internal transcribed spacer (ITS2) of the nuclear ribosomal DNA clearly showed that lymnaeids in Vietnam include 3 species, Austropeplea viridis (morphologically identified as L. viridis), Radix auricularia (morphologically identified as L. swinhoei) and Radix rubiginosa (morphologically identified as Lymnaea sp.). R. rubiginosa is a new record for Vietnam. Among them, only A. viridis was found to be infected with Fasciola spp. These results provide a new insight into lymnaeid snails in Vietnam. Identification of lymnaeid snails in Vietnam and their role in the liver fluke transmission should be further investigated. PMID:24516270

Trematode fauna of prosobranch snails of the genus Semisulcospira in Lake Biwa and the connected drainage system.

PubMed

Urabe, Misako

2003-03-01

The parasite fauna of prosobranch snails of the genus Semisulcospira was surveyed in Lake Biwa and the adjacent water system. One aspidogastrean and 28 digenetic trematode taxa were detected in 19209 snails consisting of 10 morphological species. There was no trematode species peculiar to members of the subgenus Biwamelania that is endemic to the Lake Biwa water system. However, one species, Notocotylus magniovatus, was found only in the non-endemic subgenus Semisulcospira. Of 23 digenean taxa detected in more than one host, 13 were distributed in both the lake and the tributaries. Seven of these had host taxa, more than 1% of which were infected with the parasite in both the lake and the tributaries, four had such hosts only in the tributaries, and two had no such hosts. Three species detected only in Lake Biwa were previously reported from other rivers in Japan. In the seven species detected only in the tributaries, two species had life cycles that could be maintained only in rivers. These results indicate that the core areas for the distribution of parasites of Semisulcospira are tributaries, and the lake is a sink for these species. These results contradict the expectation that the parasite fauna should be richer in the lake than in tributaries because the lake is a stable habitat over a geological time scale and has more divergent freshwater animals than the adjacent water system. Copyright 2002 Elsevier Science Ireland Ltd.

Molluscicidal potential of Heterorhabditis baujardi (Rhabditida: Heterorhabditidae), strain LPP7, on Lymnaea columella (Gastropoda: Pulmonata): An alternative for biological control of fasciolosis.

PubMed

Tunholi, Victor Menezes; Lorenzoni, P O; da Silva, Ygor Henrique; Tunholi-Alves, Vinícius Menezes; Boeloni, Jankerle Neves; da Silva, Maria Aparecida; Monteiro, Caio Oliveira; Prata, M C A; Pinheiro, J; Martins, Isabella Vilhena Freire

2017-09-01

This study elucidated for the first time, under laboratory conditions, the susceptibility of Lymnaea columella to infective juveniles of Heterorhabditis baujardi LPP7. Exposure to the nematodes induced an average mortality rate of 66.66% in the population of L. columella, with the highest values attained from the second week after exposure onward. In addition, all the reproductive parameters analyzed (total number of eggs, number of egg masses, number of eggs laid/snail, embryo hatching rate and content of galactogen stored in the albumen gland) changed as a result of the infection. The results indicate the occurrence of the phenomenon of parasitic castration in L. columella infected by H. baujardi LPP7, probably through depletion of energy reserves such as galactogen, necessary to meet the intense metabolic demands of the nematode's larval stages. Finally, histopathological analysis demonstrated an intense process of cell disorganization, characterized by the occurrence of granulomatous inflammatory reactions in tissues of exposed snails, induced by the spoliative action of the bacteria/nematode. The results suggest the use of H. baujardi LPP7 as an alternative for biological control of the population of this intermediate host, and thus of the diseases in whose epidemiological chain it participates, especially fasciolosis, in line with the recommendations of the World Health Organization (WHO). Copyright © 2017. Published by Elsevier B.V.

Agrochemicals increase trematode infections in a declining amphibian species.

PubMed

Rohr, Jason R; Schotthoefer, Anna M; Raffel, Thomas R; Carrick, Hunter J; Halstead, Neal; Hoverman, Jason T; Johnson, Catherine M; Johnson, Lucinda B; Lieske, Camilla; Piwoni, Marvin D; Schoff, Patrick K; Beasley, Val R

2008-10-30

Global amphibian declines have often been attributed to disease, but ignorance of the relative importance and mode of action of potential drivers of infection has made it difficult to develop effective remediation. In a field study, here we show that the widely used herbicide, atrazine, was the best predictor (out of more than 240 plausible candidates) of the abundance of larval trematodes (parasitic flatworms) in the declining northern leopard frog Rana pipiens. The effects of atrazine were consistent across trematode taxa. The combination of atrazine and phosphate--principal agrochemicals in global corn and sorghum production--accounted for 74% of the variation in the abundance of these often debilitating larval trematodes (atrazine alone accounted for 51%). Analysis of field data supported a causal mechanism whereby both agrochemicals increase exposure and susceptibility to larval trematodes by augmenting snail intermediate hosts and suppressing amphibian immunity. A mesocosm experiment demonstrated that, relative to control tanks, atrazine tanks had immunosuppressed tadpoles, had significantly more attached algae and snails, and had tadpoles with elevated trematode loads, further supporting a causal relationship between atrazine and elevated trematode infections in amphibians. These results raise concerns about the role of atrazine and phosphate in amphibian declines, and illustrate the value of quantifying the relative importance of several possible drivers of disease risk while determining the mechanisms by which they facilitate disease emergence.

[Epidemiology of human schistosomiasis in Mauritania. The right bank of the Senegal River as model].

PubMed

Ouldabdallahi, M; Ouldbezeid, M; Diop, C; Dem, E; Lassana, K

2010-12-01

A study was performed to determine the transmission and prevalence of human schistosomiasis in the Mauritanian side of the Senegal River basin. Parasitological investigations by Kato-Katz and urine filtration conducted on 1,259 school children indicated a mean prevalence of S. haematobium--29.0%, 25.9% and 34.3%, respectively, in the children of the lower, middle and high valley. Only the school children of the lower delta valley were infected by S. mansoni with a mean prevalence rate of 21.5%. The malacological investigations carried out in the water points of each visited village highlighted the presence of B. pfeifferi, B. senegalensis, B. globosus, B. umbilicatus, B. truncatus and B. forskalii. The last three species are announced for the first time in the Mauritanian side of the Senegal River. The laboratory snail infection experiments indicate that B. senegalensis and B. globosus are the most important intermediate hosts for S. haematobium in the Mauritanian side of the Senegal River basin. However, an incompatibility between the oasis strains of S. haematobium and the snails of the lower valley was noted. In the middle valley and high valley, the infection of the school children takes place during the rainy season, because of the creation of the temporary water points, in the lower valley; the transmission seems to be continuous.

A Rapid Monitoring and Evaluation Method of Schistosomiasis Based on Spatial Information Technology.

PubMed

Wang, Yong; Zhuang, Dafang

2015-12-12

Thanks to Spatial Information Technologies (SITs) such as Remote Sensing (RS) and Geographical Information System (GIS) that are being quickly developed and updated, SITs are being used more widely in the public health field. The use of SITs to study the characteristics of the temporal and spatial distribution of Schistosoma japonicum and to assess the risk of infection provides methods for the control and prevention of schistosomiasis japonica has gradually become a hot topic in the field. The purpose of the present paper was to use RS and GIS technology to develop an efficient method of prediction and assessment of the risk of schistosomiasis japonica. We choose the Yueyang region, close to the east DongTing Lake (Hunan Province, China), as the study area, where a recent serious outbreak of schistosomiasis japonica took place. We monitored and evaluated the transmission risk of schistosomiasis japonica in the region using SITs. Water distribution data were extracted from RS images. The ground temperature, ground humidity and vegetation index were calculated based on RS images. Additionally, the density of oncomelania snails, which are the Schistosoma japonicum intermediate host, was calculated on the base of RS data and field measurements. The spatial distribution of oncomelania snails was explored using SITs in order to estimate the area surrounding the residents with transmission risk of schistosomiasis japonica. Our research result demonstrated: (1) the risk factors for the transmission of schistosomiasis japonica were closely related to the living environment of oncomelania snails. Key factors such as water distribution, ground temperature, ground humidity and vegetation index can be quickly obtained and calculated from RS images; (2) using GIS technology and a RS deduction technique along with statistical regression models, the density distribution model of oncomelania snails could be quickly built; (3) using SITs and analysis with overlaying population distribution data, the range of transmission risk of schistosomiasis japonica of the study area can be quickly monitored and evaluated. This method will help support the decision making for the control and prevention of schistosomiasis and form a valuable application using SITs for the schistosomiasis research.

Transfection and heat-inducible expression of molluscan promoter-luciferase reporter gene constructs in the Biomphalaria glabrata embryonic snail cell line.

PubMed

Yoshino, T P; Wu, X J; Liu, H D

1998-09-01

Studies were initiated to begin developing a genetic transformation system for cells derived from the freshwater gastropod, Biomphalaria glabrata, an intermediate host of the human blood fluke Schistosoma mansoni. Using a 70-kD heat-shock protein (HSP70) cDNA probe obtained from the B. glabrata embryonic (Bge) cell line, we cloned from Bge cells a complete HSP70 gene including a 1-kb genomic DNA fragment in its 5'-flanking region containing sequences indicative of a HSP promoter. Identified in the 5'-half (416 nucleotides) of this genomic fragment were TATA and CAAT boxes, two putative transcription initiation sites, and a series of palindromic DNA repeats with shared homology to the heat-shock element consensus sequence (Bge HSP70(0.5k) promoter). The 3'-half of this upstream flanking region was comprised of a 508-base intron located immediately 5' of the ATG start codon. To determine the functionality of the putative snail promoter sequence, Bge HSP promoter/luciferase (Luc) reporter gene constructs were introduced into Bge cells by N-(1-(2,3-dioleoyloxy) propyl)-N,N,N-trimethylammonium methylsulfate (DOTAP)-mediated transfection methods, and assayed for Luc activity 48 hr following a 1.5-hr heat-shock treatment (40 degrees C). Compared with control vectors or the Bge HSP70(0.5k/1.0k) promoter constructs at 26 degrees C, a 10- to 300-fold increase in Luc expression was obtained only in the Bge HSP70 promoter/Luc-transfected cells following heat-shock. Results of transfection experiments demonstrate that the Bge HSP70(0.5k) DNA segment contains appropriate promoter sequences for driving temperature-inducible gene expression in the Bge snail cell line. This report represents the first isolation and functional characterization of an inducible promoter from a freshwater gastropod mollusc. Successful transient expression of a foreign reporter gene in Bge cells using a homologous, inducible promoter sequence now paves the way for development of methods for stable integration and expression of snail genes of interest into the Bge cell line.

Impact and cost-effectiveness of snail control to achieve disease control targets for schistosomiasis.

PubMed

Lo, Nathan C; Gurarie, David; Yoon, Nara; Coulibaly, Jean T; Bendavid, Eran; Andrews, Jason R; King, Charles H

2018-01-23

Schistosomiasis is a parasitic disease that affects over 240 million people globally. To improve population-level disease control, there is growing interest in adding chemical-based snail control interventions to interrupt the lifecycle of Schistosoma in its snail host to reduce parasite transmission. However, this approach is not widely implemented, and given environmental concerns, the optimal conditions for when snail control is appropriate are unclear. We assessed the potential impact and cost-effectiveness of various snail control strategies. We extended previously published dynamic, age-structured transmission and cost-effectiveness models to simulate mass drug administration (MDA) and focal snail control interventions against Schistosoma haematobium across a range of low-prevalence (5-20%) and high-prevalence (25-50%) rural Kenyan communities. We simulated strategies over a 10-year period of MDA targeting school children or entire communities, snail control, and combined strategies. We measured incremental cost-effectiveness in 2016 US dollars per disability-adjusted life year and defined a strategy as optimally cost-effective when maximizing health gains (averted disability-adjusted life years) with an incremental cost-effectiveness below a Kenya-specific economic threshold. In both low- and high-prevalence settings, community-wide MDA with additional snail control reduced total disability by an additional 40% compared with school-based MDA alone. The optimally cost-effective scenario included the addition of snail control to MDA in over 95% of simulations. These results support inclusion of snail control in global guidelines and national schistosomiasis control strategies for optimal disease control, especially in settings with high prevalence, "hot spots" of transmission, and noncompliance to MDA. Copyright © 2018 the Author(s). Published by PNAS.

Impact and cost-effectiveness of snail control to achieve disease control targets for schistosomiasis

PubMed Central

Yoon, Nara; Coulibaly, Jean T.; Bendavid, Eran; Andrews, Jason R.; King, Charles H.

2018-01-01

Schistosomiasis is a parasitic disease that affects over 240 million people globally. To improve population-level disease control, there is growing interest in adding chemical-based snail control interventions to interrupt the lifecycle of Schistosoma in its snail host to reduce parasite transmission. However, this approach is not widely implemented, and given environmental concerns, the optimal conditions for when snail control is appropriate are unclear. We assessed the potential impact and cost-effectiveness of various snail control strategies. We extended previously published dynamic, age-structured transmission and cost-effectiveness models to simulate mass drug administration (MDA) and focal snail control interventions against Schistosoma haematobium across a range of low-prevalence (5–20%) and high-prevalence (25–50%) rural Kenyan communities. We simulated strategies over a 10-year period of MDA targeting school children or entire communities, snail control, and combined strategies. We measured incremental cost-effectiveness in 2016 US dollars per disability-adjusted life year and defined a strategy as optimally cost-effective when maximizing health gains (averted disability-adjusted life years) with an incremental cost-effectiveness below a Kenya-specific economic threshold. In both low- and high-prevalence settings, community-wide MDA with additional snail control reduced total disability by an additional 40% compared with school-based MDA alone. The optimally cost-effective scenario included the addition of snail control to MDA in over 95% of simulations. These results support inclusion of snail control in global guidelines and national schistosomiasis control strategies for optimal disease control, especially in settings with high prevalence, “hot spots” of transmission, and noncompliance to MDA. PMID:29301964

Effects of trematode parasitism on the behaviour and ecology of a common marine snail (Littorina littorea (L.)).

PubMed

Davies, M S.; Knowles, A J.

2001-06-01

Cryptocotyle lingua (Creplin) is a digenean trematode parasite of the littoral prosobranch gastropod Littorina littorea (L.). The literature suggests the snails become infected by grazing guano of the final host, the herring gull, Larus argentatus Pontoppidan. The parasite emerges from the snail as free-swimming cercariae. Interactions between the snail and the parasite at cellular and life-history levels are well established, but little is known of the influences the interaction has on the behaviour and the ecology of the snail. We tested the response of the snail to encounters with cercariae, examined the longevity of the guano on-shore and tested the responses of the snail to encounters with guano. Over half the L. littorea tested were able to detect both cercariae and a filtered homogenate of cercariae in conspecific mucus trails, approximately one-third of animals refusing to cross the treatments. Chemoreception by the mouth or foot is considered the most likely means of detection. Guano samples (mean weight 3.22 g) naturally deposited at approximately mid-tide level were completely washed away by one tidal inundation. We consider this period too brief to allow for ingestion of eggs in guano by the snail. Further, snails would not cross guano placed in conspecific trails. Most snails would not cross guano diluted by 10(3)x(10 mg ml(-1)) and some snails could still detect guano diluted by 10(6)x(10 &mgr;g ml(-1)), though all were prepared to cross it. Detection of guano is again believed to be by chemoreception by the mouth or foot. These results are discussed in terms of the mating and aggregating behaviour of L. littorea. Ingestion of the parasite by L. littorea is likely to take place once the guano has washed away as the eggs are negatively buoyant in seawater and may adhere to rock (biofilm) or algal fronds which may be grazed by the snail.

Schistosomiasis: Geospatial Surveillance and Response Systems in Southeast Asia

NASA Astrophysics Data System (ADS)

Malone, John; Bergquist, Robert; Rinaldi, Laura; Xiao-nong, Zhou

2016-10-01

Geographic information system (GIS) and remote sensing (RS) from Earth-observing satellites offer opportunities for rapid assessment of areas endemic for vector-borne diseases including estimates of populations at risk and guidance to intervention strategies. This presentation deals with GIS and RS applications for the control of schistosomiasis in China and the Philippines. It includes large-scale risk mapping including identification of suitable habitats for Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. Predictions of infection risk are discussed with reference to ecological transformations and the potential impact of climate change and the potential for long-term temperature increases in the North as well as the impact on rivers, lakes and water resource developments. Potential integration of geospatial mapping and modeling in schistosomiasis surveillance and response systems in Asia within Global Earth Observation System of Systems (GEOSS) guidelines in the health societal benefit area is discussed.

Indicator Development for Potential Presence of Schistosomiasis Japonicum's Vector in Lake and Marshland Regions- A Case Study of Poyang Lake, Jiangxi Province, P.R. China

NASA Astrophysics Data System (ADS)

Marie, Tiphanie; Yesou, Herve; Huber, Claire; De Fraipont, Paul; Uribe, Carlos; Lacaux, Jean-Pierre; Lafaye, Murielle; Lai, Xijun; Desnos, Yves-Louis

2013-01-01

Earth observation data and bibliography on environmental parameters were used for mapping Oncomelania hupensis distribution, the Schistosomiasis japonicum’s intermediate host snail, within Poyang Lake (Jiangxi Province, P.R. China). Areas suitable for the development of O. hupensis, the vector of schistosomiasis, were derived from submersion time parameters and vegetation community indicators. ENVISAT time series data acquired from 2000 to 2009 were used for submersion times mapping, and 5 Beijing-1 data acquired during the dry season between 2006 and 2008 were used to map suitable vegetation for vector development. Yearly maps obtained indicate four principally potential endemic areas: the Gan Delta, the bank of the Fu He River, the Dalianzi Hu sector and the Poyang Lake Nature Reserve. Monthly maps from December 2005 to December 2008 show the dynamic of potential O. hupensis presence areas.

Unveiling the oxidative metabolism of Achatina fulica (Mollusca: Gastropoda) experimentally infected to Angiostrongylus cantonensis (Nematoda: Metastrongylidae).

PubMed

Tunholi-Alves, Vinícius Menezes; Tunholi, Victor Menezes; Garcia, Juberlan; Mota, Esther Maria; Castro, Rosane Nora; Pontes, Emerson Guedes; Pinheiro, Jairo

2018-06-01

For the first time, alterations in the oxidative metabolism of Achatina fulica experimentally infected with different parasite loads of Angiostrongylus cantonensis were determined. For this, the hemolymph activities of lactate dehydrogenase (LDH) and hexokinase and the glucose concentrations in the hemolymph, as well as the polysaccharide reserves in the digestive gland and cephalopedal mass, were assessed. Additionally, the contents of some carboxylic acids in the hemolymph of infected and uninfected snails were determined by high-performance liquid chromatography (HPLC), permitting a better understanding of the alterations related to the host's oxidative metabolism. As the main results, activation of oxidative pathways, such as the glycolytic pathway, was demonstrated in response to the increase in the activity of hexokinase. This tendency was confirmed by the decrease in the contents of glucose in the hemolymph of parasitized snails, indicating that the infection by A. cantonensis alters the host's metabolism, and that these changes are strongly influenced by the parasite load. This metabolic scenario was accompanied by activation of the anaerobic fermentative metabolism, indicated not only by an increase in the activity of (LDH), but also by a reduction of the content of pyruvic acid and accumulation of lactic acid in the hemolymph of parasitized snails. In this circumstance, maintenance of the host's redox balance occurs through activation of the fermentative pathways, and LDH plays a central role in this process. Together, the results indicate that A. cantonensis infection induces activation of the anaerobic metabolism of A. fulica, characterized not only by the accumulation of lactic acid, but also by a reduction in the pyruvic acid and oxalic acid contents in the hemolymph of the infected snails.

Larval digenean preferences in two sympatric snail species at differing tidal levels off the Atlantic coast of Patagonia.

PubMed

Di Giorgio, G; Gilardoni, C; Bagnato, E; Cremonte, F; Ituarte, C

2017-11-01

Larval stages of the trematodes Maritrema madrynense and Hemiuroidea fam. gen. et sp. differentially parasitized Siphonaria lessonii and S. lateralis, two sympatric pulmonate snail species on the rocky intertidal shore at Puerto Deseado, south-western Atlantic coast of Patagonia, Argentina. Snail specimens were collected at two sampling sites with contrasting physical-chemical characteristics. One site, in the upper intertidal, was exposed to sewage from fish-processing plants, greater hydrodynamic forcing and desiccation, a wider temperature range, longer exposure to ultraviolet radiation and higher abundance of birds. The second site, in the lower intertidal, was generally characterized by less stressful environmental conditions. At both sites, S. lateralis showed a markedly higher density than S. lessonii (55.13 vs. 5.87 snails/m2, respectively). Despite this, the prevalence of both digeneans was higher in S. lessonii (17.37% and 3.52% for M. madrynense and Hemiuroidea, respectively) than in S. lateralis (0.09% and 0% for M. madrynense and Hemiuroidea, respectively). This study demonstrates high parasite specificity for the host. Low densities of S. lessonii are attributed to castration of parasitized hosts and reduction of their physiological condition. The prevalence and intensity of infection of both digenean parasites were higher at the more stressful, upper intertidal site, thus suggesting that a higher abundance of birds and exposure to sewage pollution may promote the transmission of trematodes.

Studies on Schistosoma japonicum infection in the Philippines*

PubMed Central

Pesigan, T. P.; Farooq, M.; Hairston, N. G.; Jauregui, J. J.; Garcia, E. G.; Santos, A. T.; Santos, B. C.; Besa, A. A.

1958-01-01

Among the measures used in attempts to control the snail host of S. japonicum in Leyte Province, Philippines, where the terrain is unsuited to the application of molluscicides, have been removal of vegetation in and around infested streams, drainage of water-logged areas, filling low-lying areas with earth or flooding them, and digging fishponds in sluggish streams. Each of these measures is described in detail. Experiments carried out in rice-fields, which harbour great numbers of snails, have shown that improvements in rice-growing methods will not only markedly reduce the snail population but also double the rice yield. A campaign to promote the use of pit latrines encountered the serious difficulty that such latrines were not acceptable to the people. However, there is evidence that use of pit latrines does bring about a reduction in snail infection rates. No single control measure is recommended for all snail habitats, the choice of method depending on local circumstances; in many areas a combination of methods proved advantageous. It is felt that mass treatment of infected persons would not be fully effective until transmission is more thoroughly under control. PMID:13585073

[Investigations on the pathogenesis of changes in somatic growth of Lymnaea stagnalis (Gastropoda: Pulmonata) experimentally infected with parthenites Opisthioglyphe ranae (Digenea: Plagiorchiida). I. Relative weight of accessory sex organs and synthetic activity of neurosecretory cells].

PubMed

Pokora, Z

1996-01-01

In the paper an attempt to define pathogenesis of changes in somatic growth of juvenile individuals of the popular freshwater snail Lymnaea stagnalis experimentally infected with parthenites of the trematode Opisthioglyphe ranae was undertaken. Significant enlargement of relative wet weight of examined accessory sex organs (albumen gland, oothecal gland, prostate, male copulatory organ) observed in infected snails permits to explain increase of their somatic growth basing on the hypothesis of disturbances in energetistic budget of the host-as a consequence of reduction by the parasite activity of the snail's reproductive system. Pathogenesis of this phenomenon has probably a complicated character, including also effect of parthenites on activity of the neurosecretory cells that control somatic growth in examined species of the snail. An argument for this standpoint is, observed in infected snails, increase of amount of neurosecretory material and RNA in cytoplasm of these cells (the light green cells of cerebral ganglia), as well as amount of the loose fraction of chromatine in their nuclei.

Phylogenetic relationship of the Brazilian isolates of the rat lungworm Angiostrongylus cantonensis (Nematoda: Metastrongylidae) employing mitochondrial COI gene sequence data

PubMed Central

2012-01-01

Background The rat lungworm Angiostrongylus cantonensis can cause eosinophilic meningoencephalitis in humans. This nematode’s main definitive hosts are rodents and its intermediate hosts are snails. This parasite was first described in China and currently is dispersed across several Pacific islands, Asia, Australia, Africa, some Caribbean islands and most recently in the Americas. Here, we report the genetic variability among A. cantonensis isolates from different geographical locations in Brazil using mitochondrial cytochrome c oxidase subunit I (COI) gene sequences. Methods The isolates of A. cantonensis were obtained from distinct geographical locations of Brazil. Genomic DNAs were extracted, amplified by polymerase reaction, purified and sequenced. A partial sequence of COI gene was determined to assess their phylogenetic relationship. Results The sequences of A. cantonensis were monophyletic. We identified a distinct clade that included all isolates of A. cantonensis from Brazil and Asia based on eight distinct haplotypes (ac1, ac2, ac3, ac4, ac5, ac6, ac7 and ac8) from a previous study. Interestingly, the Brazilian haplotype ac5 is clustered with isolates from Japan, and the Brazilian haplotype ac8 from Rio de Janeiro, São Paulo, Pará and Pernambuco states formed a distinct clade. There is a divergent Brazilian haplotype, which we named ac9, closely related to Chinese haplotype ac6 and Japanese haplotype ac7. Conclusion The genetic variation observed among Brazilian isolates supports the hypothesis that the appearance of A. cantonensis in Brazil is likely a result of multiple introductions of parasite-carrying rats, transported on ships due to active commerce with Africa and Asia during the European colonization period. The rapid spread of the intermediate host, Achatina fulica, also seems to have contributed to the dispersion of this parasite and the infection of the definitive host in different Brazilian regions. PMID:23130987

Ultrastructural study on Biomphalaria alexandrina haemocytes infected with Schistosoma mansoni in Egypt and its correlation with nitric oxide level.

PubMed

Helal, Eman G; El-Dafrawy, Shadia M; Mohamed, Amira H; Abou-El-Nour, Basma M; Ibrahim, Samah

2014-04-01

Some snails of Biomphalaria alexandrina can resist the infection of Schistosoma mansoni so this study aimed to clearly this mechanism by using light and electron microscopy (EM) and determine the role of Nitric oxide in this mechanism. B. alexandrina snails used in this study were exposed individually to S. mansoni infection according to their response they were classified into susceptible group (shed cercariae) and resistant group (failed to shed cercariae). Snails not exposed to infection were included in this study as control group. Nitric oxide (NO) level was assayed directly in the soluble fraction of B. alexandrina haemolymph supernatants collected from each group of B. alexandrina snails were subjected to NO assay by the Greiss reaction. The level of NO in haemolymph of infected snails was significantly increased (p < 0.001) than both control and non infected snails groups, however, in non infected snails group had significantly (p < 0.05) compared to control group. This study when correlated the changes recognized by EM with NO level the pro apoptotic effect of high level of NO on the haemocytes. Characterization and identification of cell shape of haemocytes in both haemolymph and tissue were examined by light and electron microscopy. Examination of B. alexandrina snail's haemocytes revealed three types of different cells classified according to their shape and granular contents. These cells are granulocytes, amoebocytes and hyalineocytes. Electron microscope study also revealed the important role of granulocytes and amoebocytes as defense mechanism against snail infection. NO is considered an important anti parasite molecule; intra-molluscan stages of parasites switch off host NO defense response.

Estimating Genetic and Maternal Effects Determining Variation in Immune Function of a Mixed-Mating Snail

PubMed Central

Seppälä, Otto; Langeloh, Laura

2016-01-01

Evolution of host defenses such as immune function requires heritable genetic variation in them. However, also non-genetic maternal effects can contribute to phenotypic variation, thus being an alternative target for natural selection. We investigated the role of individuals’ genetic background and maternal effects in determining immune defense traits (phenoloxidase and antibacterial activity of hemolymph), as well as in survival and growth, in the simultaneously hermaphroditic snail Lymnaea stagnalis. We utilized the mixed mating system of this species by producing full-sib families in which each parental snail had produced offspring as both a dam and as a sire, and tested whether genetic background (family) and non-genetic maternal effects (dam nested within family) explain trait variation. Immune defense traits and growth were affected solely by individuals’ genetic background. Survival of snails did not show family-level variation. Additionally, some snails were produced through self-fertilization. They showed reduced growth and survival suggesting recessive load or overdominance. Immune defense traits did not respond to inbreeding. Our results suggest that the variation in snail immune function and growth was due to genetic differences. Since immune traits did not respond to inbreeding, this variation is most likely due to additive or epistatic genetic variance. PMID:27551822

Morphological and molecular data for three species of the Microphallidae (Trematoda: Digenea) in Australia, including the first descriptions of the cercariae of Maritrema brevisacciferum Shimazu et Pearson, 1991 and Microphallus minutus Johnston, 1948.

PubMed

Kudlai, Olena; Cutmore, Scott C; Cribb, Thomas H

2015-09-16

Cercariae and metacercariae of three species of the Microphallidae Travassos, 1920 were found in snails and crustaceans from tributaries of the Brisbane River, Queensland, Australia. Specimens of Maritrema brevisacciferum Shimazu et Pearson, 1991 and Microphallus minutus Johnston, 1948, which have previously been reported in Queensland, were found as cercariae in the tateid gastropod Posticobia brazieri (Smith) and as metacercariae of M. brevisacciferum in the atyid shrimp Caridina indistincta Calman and of M. minutus in the parastacid crayfish Cherax dispar Reik. Combined analysis of morphological and molecular data, based on newly generated ITS2 and partial 28S rDNA data, linked cercariae and metacercariae for both species. This is the first report of the first intermediate hosts of M. brevisacciferum and M. minutus. Infections of another unidentified microphallid metacercariae, Microphallidae gen. sp., were found in P. brazieri and C. indistincta. The sequences of metacercarial isolates from both hosts were identical. The data on the Microphallidae from Australia and species that develop in freshwater invertebrates were examined in detail.

Spatiotemporal distributions of intestinal helminths in female lesser scaup Aythya affinis during spring migration from the upper Midwest, USA

USGS Publications Warehouse

England, J. C.; Levengood, J.M.; Osborn, J. M.; Yetter, A. P.; Kinsella, J.M.; Cole, Rebecca A.; Cory D. Suski,; Hagy, Heath M.

2017-01-01

We examined the associations between intestinal helminth infracommunity structure and infection parameters and the age, size, and year and region of collection of 130 female lesser scaup (Aythya affinis) during their 2014–2015 spring migrations through the upper Midwest, USA. We identified a total of 647,174 individual helminths from 40 taxa, including 20 trematodes, 14 cestodes, 4 nematodes and 2 acanthocephalans parasitizing lesser scaup within the study area. Lesser scaup were each infected with 2–23 helminth taxa. One digenean, Plenosoma minimum, is reported for the first time in lesser scaup and in the Midwest. Mean trematode abundance and total helminth abundance was significantly less in 2015 than 2014, and we suspect that colder weather late in 2015 impacted the intermediate host fauna and caused the observed differences. Brillouin's species diversity of helminths was greatest in the northernmost region of the study area, which coincides with the range of a non-indigenous snail that indirectly causes annual mortality events of lesser scaup. While host age and size were not determined to be influential factors of helminth infracommunity structure, non-parametric ordination and permutational analysis of co-variance revealed that year and region of collection explained differences in helminth infracommunities. Our results suggest that spatiotemporal variations play an important role in the structure of intestinal helminth infracommunities found in migrating lesser scaup hosts, and may therefore impact host ability to build endogenous reserves at certain stopover locations in the Midwest.

Spatiotemporal distributions of intestinal helminths in female lesser scaup Aythya affinis during spring migration from the upper Midwest, USA.

PubMed

England, J C; Levengood, J M; Osborn, J M; Yetter, A P; Kinsella, J M; Cole, R A; Suski, C D; Hagy, H M

2017-07-01

We examined the associations between intestinal helminth infracommunity structure and infection parameters and the age, size, and year and region of collection of 130 female lesser scaup (Aythya affinis) during their 2014-2015 spring migrations through the upper Midwest, USA. We identified a total of 647,174 individual helminths from 40 taxa, including 20 trematodes, 14 cestodes, 4 nematodes and 2 acanthocephalans parasitizing lesser scaup within the study area. Lesser scaup were each infected with 2-23 helminth taxa. One digenean, Plenosoma minimum, is reported for the first time in lesser scaup and in the Midwest. Mean trematode abundance and total helminth abundance was significantly less in 2015 than 2014, and we suspect that colder weather late in 2015 impacted the intermediate host fauna and caused the observed differences. Brillouin's species diversity of helminths was greatest in the northernmost region of the study area, which coincides with the range of a non-indigenous snail that indirectly causes annual mortality events of lesser scaup. While host age and size were not determined to be influential factors of helminth infracommunity structure, non-parametric ordination and permutational analysis of co-variance revealed that year and region of collection explained differences in helminth infracommunities. Our results suggest that spatiotemporal variations play an important role in the structure of intestinal helminth infracommunities found in migrating lesser scaup hosts, and may therefore impact host ability to build endogenous reserves at certain stopover locations in the Midwest.

Quantify environmental effects in shaping the genetic diversification pattern of Oncomelania hupensis and its implications in surveillance of human susceptibility to Schistosomiasis

NASA Astrophysics Data System (ADS)

Liang, L.; Liao, J. S.; Gong, P.

2012-12-01

The transmission and distribution of schistomiasis, one of the most serious infectious diseases in East and Southeast Asia, tied closely to its unique intermediate snail host Oncomelania hupensis. The coevolved relationships of O. hupensis populations with its parasite Schistosoma japonisum are important in understanding the mechanism of disease spread. The genetic diversification pattern within population is supposed to influence the amount of parasite loads, and the susceptibility of snails determined the chance for human or mammals to get infected. Meanwhile, intervening environmental features had been long suggested to affect snail population dynamics and evolutionary trajectories of species. However, no comprehensive study referring to the above topics has been carried out on O.hupensis populations before. In this study, we reanalyzed published data in mainland China to evaluate whether human infection rate and genetic diversification patterns are related under natural environment. Besides that, we used an array of remotely sensed image derived environmental variables to quantify the amount of variation in population genetic structure that could be explained by those factors by landscape genetic analysis. We found that human schistosomiasis infection rate is positively correlated with intra-population genetic diversification and inter-population genetic exchange, which is contradictory with the Red Queen hypothesis. The patterns of genetic diversification are better revealed when non-Euclidean, environmentally determined distance measures or features are used in large heterogeneous landscape. The impact of stream connectivity on the snail inter-population genetic distances does not so evident unless taking wetlands into calculation, and thus control activities planned solely along river systems may be suboptimal. Climate features have a stronger impact on genetic structure of snails than topology, and precipitation seasonality dominates the highest proportion of explanation in genetic diversification. Different types of genes respond different to landscape effects, and it is suspected to be related with their evolution rate. Our study raises an important opportunity for public health decision making by combining geo-informatics and bio-informatics technology. Since the schistomiasis disease persistence, establishment, and intervention optimization are dependent on the genetic diversification pattern of O.hupensis populations, and that pattern is strongly environmentally determined, then certain key environmental features or landscape distances have the potential to inform public health decisions such as where to focus surveillance efforts, or disrupt the connection to stop the gene exchange. This is especially useful for Yangze River basin region under both extensive anthropogenic activities and climate change.

Divergence of gastropod life history in contrasting thermal environments in a geothermal lake.

PubMed

Johansson, M P; Ermold, F; Kristjánsson, B K; Laurila, A

2016-10-01

Experiments using natural populations have provided mixed support for thermal adaptation models, probably because the conditions are often confounded with additional environmental factors like seasonality. The contrasting geothermal environments within Lake Mývatn, northern Iceland, provide a unique opportunity to evaluate thermal adaptation models using closely located natural populations. We conducted laboratory common garden and field reciprocal transplant experiments to investigate how thermal origin influences the life history of Radix balthica snails originating from stable cold (6 °C), stable warm (23 °C) thermal environments or from areas with seasonal temperature variation. Supporting thermal optimality models, warm-origin snails survived poorly at 6 °C in the common garden experiment and better than cold-origin and seasonal-origin snails in the warm habitat in the reciprocal transplant experiment. Contrary to thermal adaptation models, growth rate in both experiments was highest in the warm populations irrespective of temperature, indicating cogradient variation. The optimal temperatures for growth and reproduction were similar irrespective of origin, but cold-origin snails always had the lowest performance, and seasonal-origin snails often performed at an intermediate level compared to snails originating in either stable environment. Our results indicate that central life-history traits can differ in their mode of evolution, with survival following the predictions of thermal optimality models, whereas ecological constraints have shaped the evolution of growth rates in local populations. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Development and characterization of 17 polymorphic microsatellite loci in the faucet snail, Bithynia tentaculata (Gastroposa: Caenogastropoda; Bithyniidae)

USGS Publications Warehouse

Henningsen, Justin P.; Lance, Stacey L.; Jones, Kenneth L.; Hagen, Chris; Laurila, Joshua; Cole, Rebecca A.; Perez, Kathryn E.

2010-01-01

Bithynia tentaculata (Linnaeus, 1758), a snail native to Europe, was introduced into the US Great Lakes in the 1870's and has spread to rivers throughout the Northeastern US and Upper Mississippi River (UMR). Trematode parasites, for which B. tentaculata is a host, have also been introduced and are causing widespread waterfowl mortality in the UMR. Waterfowl mortality is caused by ingestion of trematode-infected B. tentaculata or insects infected with parasites released from the snails. We isolated and characterized 17 microsatellite loci from the invasive faucet snail, B. tentaculata (Gastropoda: Caenogastropoda: Bithyniidae). Loci were screened in 24 individuals of B. tentaculata. The number of alleles per locus ranged from 2 to 6, observed heterozygosity ranged from 0.050 to 0.783, and the probability of identity values ranged from 0.10 to 0.91. These new loci provide tools for examining the origin and spread of invasive populations in the US and management activities to prevent waterfowl mortality.

Species of Angiostrongylus (Nematoda: Metastrongyloidea) in wildlife: A review

PubMed Central

Spratt, David M.

2015-01-01

Twenty-one species of Angiostrongylus plus Angiostrongylus sp. (Nematoda: Metastrongyloidea) are known currently in wildlife. These occur naturally in rodents, tupaiids, mephitids, mustelids, procyonids, felids, and canids, and aberrantly in a range of avian, marsupial and eutherian hosts including humans. Adults inhabit the pulmonary arteries and right atrium, ventricle and vena cava, bronchioles of the lung or arteries of the caecum and mesentery. All species pass first-stage larvae in the faeces of the host and all utilise slugs and/or aquatic or terrestrial snails as intermediate hosts. Gastropods are infected by ingestion or penetration of first-stage larvae; definitive hosts by ingestion of gastropods or gastropod slime. Transmission of at least one species may involve ingestion of paratenic hosts. Five developmental pathways are identified in these life cycles. Thirteen species, including Angiostrongylus sp., are known primarily from the original descriptions suggesting limited geographic distributions. The remaining species are widespread either globally or regionally, and are continuing to spread. Small experimental doses of infective larvae (ca. 20) given to normal or aberrant hosts are tolerated, although generally eliciting a granulomatous histopathological response; large doses (100–500 larvae) often result in clinical signs and/or death. Two species, A. cantonensis and A. costaricensis, are established zoonoses causing neurological and abdominal angiostrongliasis respectively. The zoonotic potential of A. mackerrasae, A. malaysiensis and A. siamensis particularly warrant investigation. Angiostrongylus cantonensis occurs in domestic animals, mammalian and avian wildlife and humans in the metropolitan areas of Brisbane and Sydney, Australia, where it has been suggested that tawny frogmouths and brushtail possums may serve as biosentinels. A major conservation issue is the devastating role A. cantonensis may play around zoos and fauna parks where captive rearing of endangered species programmes may exist and where Rattus spp. are invariably a problem. PMID:25853051

Transmission of Ehrlichia risticii, the agent of Potomac horse fever, using naturally infected aquatic insects and helminth vectors: preliminary report.

PubMed

Madigan, J E; Pusterla, N; Johnson, E; Chae, J S; Pusterla, J B; Derock, E; Lawler, S P

2000-07-01

Ehrlichia risticii, the agent of Potomac horse fever (PHF), has been recently detected in trematode stages found in snail secretions and in aquatic insects. Based on these findings, horses could conceivably be exposed to E. risticii by skin penetration with infected cercariae, by ingestion of infected cercariae in water or via metacercariae in a second intermediate host, such as an aquatic insect. In order to test this hypothesis, horses were challenged with infectious snail secretions and aquatic insects collected from a PHF endemic region in northern California. Two horses stood with their front feet in water harbouring E. risticii-infected cercariae, 2 horses drank water harbouring E. risticii-infected cercariae, and 6 horses were fed pools of different aquatic insects harbouring E. risticii-infected metacercariae. In this preliminary study, only the one horse infected orally with mature caddisflies (Dicosmoecus gilvipes) developed the clinical and haematological disease syndrome of PHF. The agent was isolated from the blood of the infected horse in a continuous cell line and identified as E. risticii by characterisation of the 16S rRNA gene. Therefore, E. risticii is maintained in nature in a complex aquatic ecosystem and transmission to horses can occur through accidental ingestion of insects such as caddisflies containing infected metacercariae. At present, the small number of horses used in this study does not exclude other insects and free trematode stages as potential sources of infection.

Schistosomiasis Research in the Dongting Lake Region and Its Impact on Local and National Treatment and Control in China

PubMed Central

McManus, Donald P.; Gray, Darren J.; Ross, Allen G.; Williams, Gail M.; He, Hong-Bin; Li, Yue-Sheng

2011-01-01

Schistosomiasis is a chronic and debilitating parasitic disease that has often been neglected because it is a disease of poverty, affecting poor rural communities in the developing world. This is not the case in the People's Republic of China (PRC), where the disease, caused by Schistosoma japonicum, has long captured the attention of the Chinese authorities who have, over the past 50–60 years, undertaken remarkably successful control programs that have substantially reduced the schistosomiasis disease burden. The Dongting Lake region in Hunan province is one of the major schistosome-endemic areas in the PRC due to its vast marshland habitats for the Oncomelania snail intermediate hosts of S. japonicum. Along with social, demographic, and other environmental factors, the recent completion and closure of the Three Gorges dam will most likely increase the range of these snail habitats, with the potential for re-emergence of schistosomiasis and increased transmission in Hunan and other schistosome-endemic provinces being a particular concern. In this paper, we review the history and the current status of schistosomiasis control in the Dongting Lake region. We explore the epidemiological factors contributing to S. japonicum transmission there, and summarise some of the key research findings from studies undertaken on schistosomiasis in Hunan province over the past 10 years. The impact of this research on current and future approaches for sustainable integrated control of schistosomiasis in this and other endemic areas in the PRC is emphasised. PMID:21912706

Ecotourism as a source of infection with Schistosoma mansoni in Minas Gerais, Brazil.

PubMed

Murta, Felipe Leão Gomes; Massara, Cristiano Lara; Nogueira, Joyce Favacho Cardoso; Dos Santos Carvalho, Omar; de Mendonça, Cristiane Lafetá Furtado; Pinheiro, Viviane Aparecida Oliveira; Enk, Martin Johannes

2016-01-01

In recent years, a new pattern of schistosomiasis transmission has been described which is related to recreational activities associated with rural or ecological tourism and migratory flows and accompanying changes in social dynamics in Brazil. The objective of this report is to describe two schistosomiasis outbreaks that occurred during the practice of rural tourism in Minas Gerais, Brazil, and review this pattern of transmission within the wider context of schistosomiasis control. The first outbreak was characterized by its high infection rate, showing that 59 % of the exposed eco-tourists became positive for infection with Schistosoma mansoni . In addition, all three disease transmitting species of intermediate host snails were found in the area. In the second outbreak, all members of one tourist family were infected and reported contact with water in a well-known tourist area. The malacological survey in the region revealed an infection rate with S. mansoni of 8.3 % among the collected snails. Infection of urban dwellers that report contact with contaminated water associated with ecotourism represents a new pattern of disease transmission and dissemination. The infection with the disease at these occasions finds its expression in outbreaks of acute schistosomiasis among internal tourists to rural areas. Therefore, epidemiological surveillance in endemic areas should be aware of this schistosomiasis transmission pattern, and a multidisciplinary approach, most of all sanitation and health education measures, is required in order increase the efficiency of control strategies.

[Schistosomiasis and soil-transmitted helminthiasis among schoolchildren of Nikki and Pèrèrè, two northeastern towns of Benin].

PubMed

Ibikounlé, M; Gbédjissi, L G; Ogouyèmi-Hounto, A; Batcho, W; Kindé-Gazard, D; Massougbodji, A

2014-08-01

Infection with schistosomiasis and soil-transmitted helminthiasis are widespread in sub-Saharan Africa and the burden of disease associated with parasites is enormous. A study was performed to determine the transmission and prevalence of human schistosomiasis and soil-transmitted helminthiasis among school children of Nikki and Perere, two north eastern towns of Benin, bordering Republic of Nigeria. Parasitological investigations by urine filtration and Kato-Katz conducted on 1,344 school children indicated a mean prevalence of S. haematobium and S. mansoni 48.44% and 0%, respectively, in the children of Nikki area and 45.24% and 4.11% in Perere area. Only schoolchildren of Sonon locality were infected by S. mansoni with a mean prevalence rate of 36.24%. KatoKatz tests releaved five species of soil-transmitted helminths: Ankylostoma duodenale (8.16% and 6.73%), Ascaris lumbricoides (6.26% and 2.30%), Enterobius vermicularis (1.09% and 1.97%), Trichuris trichiura (1.97% and 1.90%) and Strongyloides stercoralis (2.04% and 0.99%), respectively, in the schoolchildren of Nikki and Perere areas. The malacological investigations carried out in the freshwater points of each visited locality highlighted the presence of four species of freshwater snails known as intermediate host of schistosome: Biomphalaria pfeifferi, Bulinus forskalii, B. globosus and B. truncatus.Two B. globosus and B. pfeifferi collected in Sonon locality were naturally infected by schistosome, indicated the importance of their two species of snail in schistosome transmission cycle.

Interrupting seasonal transmission of Schistosoma haematobium and control of soil-transmitted helminthiasis in northern and central Côte d'Ivoire: a SCORE study protocol.

PubMed

Tian-Bi, Yves-Nathan T; Ouattara, Mamadou; Knopp, Stefanie; Coulibaly, Jean T; Hürlimann, Eveline; Webster, Bonnie; Allan, Fiona; Rollinson, David; Meïté, Aboulaye; Diakité, Nana R; Konan, Cyrille K; N'Goran, Eliézer K; Utzinger, Jürg

2018-01-29

To achieve a world free of schistosomiasis, the objective is to scale up control and elimination efforts in all endemic countries. Where interruption of transmission is considered feasible, countries are encouraged to implement a comprehensive intervention package, including preventive chemotherapy, information, education and communication (IEC), water, sanitation and hygiene (WASH), and snail control. In northern and central Côte d'Ivoire, transmission of Schistosoma haematobium is seasonal and elimination might be achieved. In a cluster-randomised trial, we will assess different treatment schemes to interrupt S. haematobium transmission and control soil-transmitted helminthiasis over a 3-year period. We will compare the impact of (i) arm A: annual mass drug administration (MDA) with praziquantel and albendazole before the peak schistosomiasis transmission season; (ii) arm B: annual MDA after the peak schistosomiasis transmission season; (iii) arm C: two yearly treatments before and after peak schistosomiasis transmission; and (iv) arm D: annual MDA before peak schistosomiasis transmission, coupled with chemical snail control using niclosamide. The prevalence and intensity of S. haematobium and soil-transmitted helminth infections will be assessed using urine filtration and Kato-Katz thick smears, respectively, in six administrative regions in northern and central parts of Côte d'Ivoire. Once a year, urine and stool samples will be collected and examined from 50 children aged 5-8 years, 100 children aged 9-12 years and 50 adults aged 20-55 years in each of 60 selected villages. Changes in S. haematobium and soil-transmitted helminth prevalence and intensity will be assessed between years and stratified by intervention arm. In the 15 villages randomly assigned to intervention arm D, intermediate host snails will be collected three times per year, before niclosamide is applied to the selected freshwater bodies. The snail abundance and infection rates over time will allow drawing inference on the force of transmission. This cluster-randomised intervention trial will elucidate whether in an area with seasonal transmission, the four different treatment schemes can interrupt S. haematobium transmission and control soil-transmitted helminthiasis. Lessons learned will help to guide schistosomiasis control and elimination programmes elsewhere in Africa. ISRCTN ISRCTN10926858 . Registered 21 December 2016. Retrospectively registered.

Morphological integration and pleiotropy in the adaptive body shape of the snail-feeding carabid beetle Damaster blaptoides.

PubMed

Konuma, Junji; Yamamoto, Satoshi; Sota, Teiji

2014-12-01

The snail-feeding carabid beetle Damaster blaptoides exhibits diverse head and thorax morphologies, and these morphotypes are linked with two alternative feeding behaviours. Stout-shaped beetles feed on snails by crushing the shells, whereas slender-shaped beetles consume snails by inserting their heads into the shells. A trade-off exists between these feeding strategies. Because intermediate-shaped beetles are less proficient in these two behaviours, stout-slender morphological divergence occurs between related species feeding on land snails. To examine the genetic basis of these morphotypes, we conducted morphological analyses and quantitative trait locus (QTL) mapping using backcross offspring between the stout and slender subspecies. The morphological analyses showed that the width and length of the beetle body parts were correlated with each other; in particular, the head width (HW) and thorax length (TL) were strongly negatively correlated. QTL mapping showed that QTLs for HW and TL are located in close proximity to one another on the longest linkage group and that they have positive and negative additive genetic effects. Our results suggest that the adaptive phenotypic sets of a wide head and short thorax and a narrow head and long thorax are based on the closeness of these QTLs. Morphological integration between the head and thorax may play an important role in the adaptive divergence of these beetles. © 2014 John Wiley & Sons Ltd.

Time series analysis of the transcriptional responses of Biomphalaria glabrata throughout the course of intramolluscan development of Schistosoma mansoni and Echinostoma paraensei

PubMed Central

Hanington, Patrick C.; Lun, Cheng-Man; Adema, Coen M; Loker, Eric S

2010-01-01

Successful colonization of a compatible snail host by a digenetic trematode miracidium initiates a complex, proliferative development program requiring weeks to reach culmination in the form of production of cercariae which, once started, may persist for the remainder of the life span of the infected snail. How are such proliferative and invasive parasites able to circumvent host defenses and establish chronic infections? Using a microarray designed to monitor the internal defense and stress-related responses of the freshwater snail Biomphalaria glabrata, we have undertaken a time course study to monitor snail responses following exposure to two different trematode species to which the snail is susceptible: the medically important Schistosoma mansoni, exemplifying sporocyst production in its larval development, or Echinostoma paraensei, representing an emphasis on rediae production in its larval development. We sampled eight time points (0.5, 1, 2, 4, 8, 16 and 32 days p.i.) that cover the period required for cercariae to be produced. Following exposure to S. mansoni, there was a preponderance of up-regulated over down-regulated array features through 2 days p.i. but by 4 days p.i. and thereafter, this pattern was strongly reversed. For E. paraensei, there was a preponderance of down-regulated array features over up-regulated features at even 0.5 days p.i., a pattern that persists throughout the course of infection except for 1 day p.i., when up-regulated array features slightly outnumbered down-regulated features. Examination of particular array features revealed several that were up-regulated by both parasites early in the course of infection and one, fibrinogen related protein 4 (FREP 4), that remained significantly elevated throughout the course of infection with either parasite, effectively serving as a marker of infection. Many defense-related transcripts were persistently down-regulated, including several fibrinogen-containing lectins and homologs of molecules best known from vertebrate phagocytic cells. Our results are consistent with earlier studies suggesting that both parasites are able to interfere with host defense responses, including a tendency for E. paraensei to do so more rapidly and strongly than S. mansoni They further suggest mechanisms for how trematodes are able to establish the chronic infections necessary for their continued success. PMID:20083115

The control of snail hosts of bilharziasis and fascioliasis in Southern Rhodesia.

PubMed

CLARKE, V D; SHIFF, C J; BLAIR, D M

1961-01-01

The authors review the experimental work that has been done since the Second World War on the use of chemical molluscicides in Southern Rhodesia and describe the development of a co-operative snail control campaign involving local landowners and various Government departments. In 1959 and 1960 efforts were concentrated on four large-scale experiments to test the methods of application of copper sulfate, sodium pentachlorophenate and Bayer 73 under a variety of climatic and physiographic conditions.From this work the authors conclude that it would appear possible and practicable to control vector snails in natural water courses and reservoirs in savannah areas of Central Africa to a degree at which it is thought that transmission of bilharziasis from man to man and of fascioliasis from animal to animal does not take place.

The control of snail hosts of bilharziasis and fascioliasis in Southern Rhodesia

PubMed Central

Clarke, V. DE V.; Shiff, C. J.; Blair, D. M.

1961-01-01

The authors review the experimental work that has been done since the Second World War on the use of chemical molluscicides in Southern Rhodesia and describe the development of a co-operative snail control campaign involving local landowners and various Government departments. In 1959 and 1960 efforts were concentrated on four large-scale experiments to test the methods of application of copper sulfate, sodium pentachlorophenate and Bayer 73 under a variety of climatic and physiographic conditions. From this work the authors conclude that it would appear possible and practicable to control vector snails in natural water courses and reservoirs in savannah areas of Central Africa to a degree at which it is thought that transmission of bilharziasis from man to man and of fascioliasis from animal to animal does not take place. PMID:13879773

Exploiting Dragon Envisat Times Series and Other Earth Observation Data

NASA Astrophysics Data System (ADS)

Marie, Tiphanie; Lai, Xijun; Huber, Claire; Chen, Xiaoling; Uribe, Carlos; Huang, Shifeng; Lafaye, Murielle; Yesou, Herve

2010-10-01

Earth Observation data were used for mapping potential Schistosomiasis japonica distribution, within Poyang Lake (Jiangxi Province, PR China). In the first of two steps, areas suitable for the development of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum, were derived from submersion time parameters and vegetation community indicators. Y early maps from 2003 to 2008 indicate five principally potential endemic areas: Poyang Lake National Nature Reserve, Dalianzi Hu, Gan Delta, Po Jiang and Xi He. Monthly maps showing the annual dynamic of potential O. hupensis presence areas were obtained from December 2005 to December 2008. In a second step human potential transmission risk was handled through the mapping of settlements and the identification of some human activities. The urban areas and settlements were mapped all around the lake and fishing net locations in the central part of Poyang Lake were identified. Finally, data crossing of the different parameters highlight the potential risk of transmission in most of the fishing nets areas.

Life cycle of Stephanoprora uruguayense (Digenea: Echinostomatidae) in Argentina.

PubMed

Ostrowski de Núñez, Margarita

2007-10-01

The life cycle of Stephanoprora uruguayense Holcman et Olagüe, 1989, was experimentally resolved. In an artificial pond in the Zoological Garden in Buenos Aires City, Argentina, Heleobia parchappei (Hydrobiidae) was found to be releasing large-tailed cercariae with a prepharyngeal body, but lacking collar spines and corpuscles in the excretory system. Metacercariae, which encysted on the gills of naturally and experimentally infected Cnesterodon decemmaculatus (Poecilidae), developed collar spines and corpuscles in the excretory system in 7 days. Sexually mature adults were recovered from chicks and immature adults from mice fed metacercariae from C. decemmaculatus. Eggs shed in chick feces developed to miracidia within 10 days; sporocysts were found on the gills of snails. Stephanoprora uruguayense and S. denticulata from Europe are similar in adult morphology, but can be distinguished by morphological and behavioral features of larvae. Likewise, although S. denticulata and S. paradenticulata from Venezuela are similar to S. uruguayense in adult morphology, they differ considerably in larval morphology and intermediate hosts.

Effects of parasitism and environment on shell size of the South American intertidal mud snail Heleobia australis (Gastropoda)

NASA Astrophysics Data System (ADS)

Alda, Pilar; Bonel, Nicolás; Cazzaniga, Néstor J.; Martorelli, Sergio R.

2010-04-01

The aim of this work was to evaluate the effects of parasitism and certain environmental factors on the shell size of Heleobia australis (Hydrobiidae, Cochliopinae). We report sporocysts and metacercariae of Microphallus simillimus (Microphallidae, Trematoda) parasitizing the gonad and digestive gland of H. australis specimens from two sites of Bahía Blanca estuary, Argentina. The prevalence of infection was significantly higher (34.17% in winter and 68.14% in late spring) in snails from the outer estuary at Site 2 than in those from the inner estuary at Site 1 (5.88% and 4.71% respectively). The only known definitive host for this digenean is the white-backed stilt Himantopus melanurus (Recurvirostridae, Aves), most abundant in the estuary during winter. Parasitism by M. simillimus causes variations in the shell dimensions of H. australis, the shells of infected snails being narrower than those of uninfected snails. Snails from Site 2 were found in general to be significantly smaller than those at Site 1, possibly as a result of differences in environmental factors such as the degree of exposure to wave energy, the allocation of energy to reproduction rather than growth (induced by predation and/or parasitic castrators) and anthropogenic stressors.

DIFFERENTIATION OF SCHISTOSOMA HAEMATOBIUM FROM RELATED SCHISTOSOMES BY PCR AMPLIFYING AN INTER-REPEAT SEQUENCE

PubMed Central

ABBASI, IBRAHIM; KING, CHARLES H.; STURROCK, ROBERT F.; KARIUKI, CURTIS; MUCHIRI, ERIC; HAMBURGER, JOSEPH

2008-01-01

Schistosoma haematobium infects nearly 150 million people, primarily in Africa, and is transmitted by select species of local bulinid snails. These snails can host other related trematode species as well, so that effective detection and monitoring of snails infected with S. haematobium requires a successful differentiation between S. haematobium and any closely related schistosome species. To enable differential detection of S. haematobium DNA by simple polymerase chain reaction (PCR), we designed and tested primer pairs from numerous newly identified Schistosoma DNA repeat sequences. However, all pairs tested were found unsuitable for this purpose. Differentiation of S. haematobium from S. bovis, S. mattheei, S. curassoni, and S. intercalatum (but not from S. margrebowiei) was ultimately accomplished by PCR using one primer from a newly identified repeat, Sh110, and a second primer from a known schistosomal splice-leader sequence. For evaluation of residual S. haematobium transmission after control interventions, this differentiation tool will enable accurate monitoring of infected snails in areas where S. haematobium is sympatric with the most prevalent other schistosome species. PMID:17488921

The Compatibility Between Biomphalaria glabrata Snails and Schistosoma mansoni: An Increasingly Complex Puzzle.

PubMed

Mitta, G; Gourbal, B; Grunau, C; Knight, M; Bridger, J M; Théron, A

2017-01-01

This review reexamines the results obtained in recent decades regarding the compatibility polymorphism between the snail, Biomphalaria glabrata, and the pathogen, Schistosoma mansoni, which is one of the agents responsible for human schistosomiasis. Some results point to the snail's resistance as explaining the incompatibility, while others support a "matching hypothesis" between the snail's immune receptors and the schistosome's antigens. We propose here that the two hypotheses are not exclusive, and that the compatible/incompatible status of a particular host/parasite couple probably reflects the balance of multiple molecular determinants that support one hypothesis or the other. Because these genes are involved in a coevolutionary arms race, we also propose that the underlying mechanisms can vary. Finally, some recent results show that environmental factors could influence compatibility. Together, these results make the compatibility between B. glabrata and S. mansoni an increasingly complex puzzle. We need to develop more integrative approaches in order to find targets that could potentially be manipulated to control the transmission of schistosomiasis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bovine fasciolosis: control strategies based on the location of Galba truncatula habitats on farms.

PubMed

Knubben-Schweizer, Gabriela; Torgerson, Paul R

2015-02-28

Infection of livestock with Fasciola hepatica is a worldwide, economically important and increasing problem. Even though, bovine fasciolosis can be a disease associated with particular regions, there are usually epidemiological issues on individual farms. For this reason, it is recommended to find the source of infection by examination of definite hosts and pastures on a farm. The following factors which promote the transmission of bovine fasciolosis are usually found: (A) Snail habitats are present on pastures used for young stock (prior to first calving) or dry cows only. Pastures for dairy cows are not affected. (B) Snail habitats are present on all pastures for dairy cows. (C) Snail habitats are present on single pastures used for dairy cows. (D) Snail habitats are present on hayfields. For each of these epidemiological situations an individual control strategy is advised. When a control strategy is tailored according to the specific epidemiology found on the individual farm, egg shedding and F. hepatica-seroprevalence can be reduced significantly. This approach can support the responsible use of the available flukicides. Copyright © 2014 Elsevier B.V. All rights reserved.

Morphological Characteristics and Phylogenetic Trends of Trematode Cercariae in Freshwater Snails from Nakhon Nayok Province, Thailand

PubMed Central

Chontananarth, Thapana; Tejangkura, Thanawan; Wetchasart, Napat; Chimburut, Cherdchay

2017-01-01

The prevalence of cercarial infection in freshwater snails and their evolutionary trends were studied in Nakhon Nayok province, Thailand. A total of 2,869 individual snails were examined for parasitic infections. The results showed that 12 snail species were found to host larval stages of trematodes with an overall prevalence of 4.7%. The infected specimens included 7 types at the cercarial stage; cercariae, megalurous cercariae, echinostome cercariae, furcocercous cercariae, parapleurolophocercous cercariae, virgulate cercariae, and xiphidiocercariae. Regarding molecular identification, ITS2 sequence data of each larval trematode were analyzed, and a dendrogram was constructed using the neighbor-joining method with 10,000 replicates. The dendrogram was separated into 6 clades (order/family), including Echinostomatida/Echinostomatidae, Echinostomatida/Philophthalmidae, Opisthorchiida/Heterophyidae, Plagiorchiida/Prosthogonimidae, Plagiorchiida/Lecithodendriidae, and Strigeatida/Cyathocotylidae. These findings were used to confirm morphological characteristics and evolutionary trends of each type of cercariae discovered in Nakhon Nayok province. Furthermore, this investigation confirmed that the ITS2 data of cercariae could be used to study on phylogenetic relationships or to determine classification of this species at order and/or family level when possible. PMID:28285506

Natural selection on immune defense: A field experiment.

PubMed

Langeloh, Laura; Behrmann-Godel, Jasminca; Seppälä, Otto

2017-02-01

Predicting the evolution of phenotypic traits requires an understanding of natural selection on them. Despite its indispensability in the fight against parasites, selection on host immune defense has remained understudied. Theory predicts immune traits to be under stabilizing selection due to associated trade-offs with other fitness-related traits. Empirical studies, however, report mainly positive directional selection. This discrepancy could be caused by low phenotypic variation in the examined individuals and/or variation in host resource level that confounds trade-offs in empirical studies. In a field experiment where we maintained Lymnaea stagnalis snails individually in cages in a lake, we investigated phenotypic selection on two immune defense traits, phenoloxidase (PO)-like activity and antibacterial activity, in hemolymph. We used a diverse laboratory population and manipulated snail resource level by limiting their food supply. For six weeks, we followed immune activity, growth, and two fitness components, survival and fecundity of snails. We found that PO-like activity and growth were under stabilizing selection, while antibacterial activity was under positive directional selection. Selection on immune traits was mainly driven by variation in survival. The form of selection on immune defense apparently depends on the particular trait, possibly due to its importance for countering the present parasite community. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Morphologic, Pathologic, and Genetic Investigations of Bolbophorus Species Affecting Cultured Channel Catfish in the Mississippi Delta.

PubMed

Levy, M G; Flowers, J R; Poore, M F; Mullen, J E; Khoo, L H; Pote, L M; Paperna, I; Dzikowski, R; Litaker, R W

2006-12-01

Trematodes belonging to the genus Bolbophorus have recently been reported as the cause of substantial morbidity and mortality in cultured channel catfish Ictalurus punctatus in Mississippi and Louisiana. Previous investigators identified only a single species, B. confusus. In this investigation, genetic techniques were used to identify all stages of the parasite in all of its hosts. The 18s rRNA genes from specimens collected in Mississippi were sequenced and compared; this analysis revealed that there are two distinct species, B. damnificus (previously identified as B. confusus) and another, undescribed species. (Phylogenetic analysis indicated that a third species, B. levantinus, is also closely related to the Mississippi species.) Species-specific polymerase chain reaction assays capable of identifying and differentiating between these two parasites were developed. Both species were found to infect the first intermediate host (the ram's horn snail Planorbella trivolvis) in commercial channel catfish ponds, but only B. damnificus was recovered from the fish themselves. The new, unidentified Bolbophorus species was determined to be highly pathogenic to a number of fish species. The contribution of B. damnificus to disease in cultured channel catfish remains undetermined. Future investigations of these parasites must now take into account the presence of two distinct species.

Morphologic, Pathologic, and Genetic Investigations of Bolbophorus Species Affecting Cultured Channel Catfish in the Mississippi Delta.

PubMed

Levy, M G; Flowers, J R; Poore, M F; Mullen, J E; Khoo, L H; Pote, L M; Paperna, I; Dzikowski, R; Litaker, R W

2002-12-01

Trematodes belonging to the genus Bolbophorus have recently been reported as the cause of substantial morbidity and mortality in cultured channel catfish Ictalurus punctatus in Mississippi and Louisiana. Previous investigators identified only a single species, B. confusus. In this investigation, genetic techniques were used to identify all stages of the parasite in all of its hosts. The 18s rRNA genes from specimens collected in Mississippi were sequenced and compared; this analysis revealed that there are two distinct species, B. damnificus (previously identified as B. confusus) and another, undescribed species. (Phylogenetic analysis indicated that a third species, B. levantinus, is also closely related to the Mississippi species.) Species-specific polymerase chain reaction assays capable of identifying and differentiating between these two parasites were developed. Both species were found to infect the first intermediate host (the ram's horn snail Planorbella trivolvis) in commercial channel catfish ponds, but only B. damnificus was recovered from the fish themselves. The new, unidentified Bolbophorus species was determined to be highly pathogenic to a number of fish species. The contribution of B. damnificus to disease in cultured channel catfish remains undetermined. Future investigations of these parasites must now take into account the presence of two distinct species.

Adaptation of Lymnaea fuscus and Radix balthica to Fasciola hepatica through the experimental infection of several successive snail generations

PubMed Central

2014-01-01

Background High prevalence of Fasciola hepatica infection (>70%) was noted during several outbreaks before the 2000s in several French farms where Galba truncatula is lacking. Other lymnaeids such as Lymnaea fuscus, L. glabra and/or Radix balthica are living in meadows around these farms but only juvenile snails can sustain complete larval development of F. hepatica while older snails were resistant. The low prevalence of infection (<20%) and limited cercarial production (<50 cercariae per infected snail) noted with these juveniles could not explain the high values noted in these cattle herds. As paramphistomosis due to Calicophoron daubneyi was not still noted in these farms, the existence of another mode of infection was hypothesized. Experimental infection of several successive generations of L. glabra, originating from eggs laid by their parents already infected with this parasite resulted in a progressive increase in prevalence of snail infection and the number of shed cercariae. The aim of this paper was to determine if this mode of snail infection was specific to L. glabra, or it might occur in other lymnaeid species such as L. fuscus and R. balthica. Methods Five successive generations of L. fuscus and R. balthica were subjected to individual bimiracidial infections in the laboratory. Resulting rediae and cercariae in the first four generations were counted after snail dissection at day 50 p.e. (20°C), while the dynamics of cercarial shedding was followed in the F5 generation. Results In the first experiment, prevalence and intensity of F. hepatica infection in snails progressively increased from the F1 (R. balthica) or F2 (L. fuscus) generation. In the second experiment, the prevalence of F. hepatica infection and the number of shed cercariae were significantly lower in L. fuscus and R. balthica (without significant differences between both lymnaeids) than in G. truncatula. Conclusion The F. hepatica infection of several successive snail generations, coming from parents infected with this parasite, resulted in a progressive increase in prevalence and intensity of snail infection. This may explain high prevalence of fasciolosis noted in several cattle-breeding farms when the common snail host of this digenean, G. truncatula, is lacking. PMID:24986589

Multiple paternity in the freshwater snail, Potamopyrgus antipodarum

PubMed Central

Soper, Deanna M; Delph, Lynda F; Lively, Curt M

2012-01-01

Mating multiply may incur costs, such as exposure to predators and to sexually transmitted diseases. Nevertheless, it may be favored, in spite of these costs, as a way to increase the genetic diversity of offspring through fertilization by multiple males. Here, we tested for multiple paternity in a freshwater snail (Potamopyrgus antipodarum), which is host to several species of sterilizing trematode worms. Using microsatellites markers, we found multiple paternity in two different snail populations, with as many as seven males fertilizing a single female. In addition, high evenness of sire fertilization was found within individual broods. Multiple paternity can occur for a variety of reasons; however, given that these populations experience high risk of infection by a sterilizing trematode, one potential explanation may be that multiple paternity and high evenness of sire fertilizations increase the chances of the production of parasite-resistant offspring. PMID:23301182

Elimination of urogenital schistosomiasis in Iran: past history and the current situation.

PubMed

Khademvatan, Shahram; Salmanzadeh, Shokrollah; Foroutan-Rad, Masoud; Ghomeshi, Mohammad

2016-09-01

In recent years, through a national programme for schistosomiasis control, this infection has been eliminated from Iran. The aim of this study was to report the process of significant decrease of urogenital schistosomiasis in southwestern Iran. During national programme surveillance for urogenital schistosomiasis control which was implemented by Centres for Disease Control and Prevention (CDC) of Khuzestan province from 1975 to 2013, more than 1·3 million urine samples were taken from inhabitants of high risk foci. All urine samples were gathered between 10:00 a.m and 02:00 p.m and, after centrifuging, specimens were tested under optical microscope in order to detect Schistosoma haematobium eggs. Data analysis was performed using SPSS 18 software. In this retrospective study significant reduction was seen in number of infections between 1975 and 2013. During the years 1975-1980, 1981-1990 and 1991-2000 there were 1582, 761 and 79 cases of S. haematobium, respectively. In 2001 only one case was reported from Ahvaz and indeed this was the last case of urogenital schistosomiasis in Khuzestan and of course, in Iran. Prevalence from 1·064% between 1975 and 1980 slumped to 0% in 2012-2013. During several projects for surveillance of urogenital schistosomiasis, selective population chemotherapy, snail control, population education, environmental improvement, etc were carried out throughout the surveillance period. According to elimination of S. haematobium in Khuzestan province, the only endemic region of Iran, control of disease, especially the campaign with intermediate host snails should be continued. Iran can be a successful model for countries suffering from this disease.

Environmental determinants of the spatial distribution of Angiostrongylus vasorum, Crenosoma vulpis and Eucoleus aerophilus in Hungary.

PubMed

Tolnai, Z; Széll, Z; Sréter, T

2015-01-30

Angiostrongylus vasorum, Crenosoma vulpis and Eucoleus aerophilus (syn. Capillaria aerophila) are the most important lungworm species infecting wild and domesticated canids in Europe. To investigate the spatial distribution of these parasites and the factors influencing their circulation in the fox populations, 937 red foxes (Vulpes vulpes) were tested for lungworm infection in Hungary. The prevalence of A. vasorum, C. vulpis and E. aerophilus infection was high (17.9, 24.6 and 61.7%). The distribution pattern of infection in foxes and the relationship of this pattern with landscape and climate was analyzed by geographic information system. Based on the analysis, the annual precipitation was the major determinant of the spatial distribution of A. vasorum and C. vulpis and E. aerophilus. Nevertheless, the mean annual temperature also influenced the distribution of A. vasorum and E. aerophilus. The positive relationship with annual precipitation and the negative relationship with mean annual temperature can be attributed to the sensitivity of larvae, eggs and intermediate hosts (snails and slugs) of lungworms for desiccation. Based on the highly clumped distribution of A. vasorum and C. vulpis, the indirect life cycle (larvae, slugs and snails) of these parasites seems to be particularly sensitive for environmental effects. The distribution of E. aerophilus was considerably less clumped indicating a lower sensitivity of the direct life cycle (eggs) of this parasite for environmental factors. Based on these results, lungworm infections in canids including dogs can be expected mainly in relatively wet and cool areas. Copyright © 2014 Elsevier B.V. All rights reserved.

Parasitic castration: the evolution and ecology of body snatchers

USGS Publications Warehouse

Lafferty, Kevin D.; Kuris, Armand M.

2009-01-01

Castration is a response to the tradeoff between consumption and longevity faced by parasites. Common parasitic castrators include larval trematodes in snails, and isopod and barnacle parasites of crustaceans. The infected host (with its many unique properties) is the extended phenotype of the parasitic castrator. Because an individual parasitic castrator can usurp all the reproductive energy from a host, and that energy is limited, intra- and interspecific competition among castrators is generally intense. These parasites can be abundant and can substantially depress host density. Host populations subject to high rates of parasitic castration appear to respond by maturing more rapidly.

A Targeted Capture Linkage Map Anchors the Genome of the Schistosomiasis Vector Snail, Biomphalaria glabrata.

PubMed

Tennessen, Jacob A; Bollmann, Stephanie R; Blouin, Michael S

2017-07-05

The aquatic planorbid snail Biomphalaria glabrata is one of the most intensively-studied mollusks due to its role in the transmission of schistosomiasis. Its 916 Mb genome has recently been sequenced and annotated, but it remains poorly assembled. Here, we used targeted capture markers to map over 10,000 B. glabrata scaffolds in a linkage cross of 94 F1 offspring, generating 24 linkage groups (LGs). We added additional scaffolds to these LGs based on linkage disequilibrium (LD) analysis of targeted capture and whole-genome sequences of 96 unrelated snails. Our final linkage map consists of 18,613 scaffolds comprising 515 Mb, representing 56% of the genome and 75% of genic and nonrepetitive regions. There are 18 large (> 10 Mb) LGs, likely representing the expected 18 haploid chromosomes, and > 50% of the genome has been assigned to LGs of at least 17 Mb. Comparisons with other gastropod genomes reveal patterns of synteny and chromosomal rearrangements. Linkage relationships of key immune-relevant genes may help clarify snail-schistosome interactions. By focusing on linkage among genic and nonrepetitive regions, we have generated a useful resource for associating snail phenotypes with causal genes, even in the absence of a complete genome assembly. A similar approach could potentially improve numerous poorly-assembled genomes in other taxa. This map will facilitate future work on this host of a serious human parasite. Copyright © 2017 Tennessen et al.

The Value of the Freshwater Snail Dip Scoop Sampling Method in Macroinvertebrates Bioassessment of Sugar Mill Wastewater Pollution in Mbandjock, Cameroon

PubMed Central

Takougang, Innocent; Barbazan, Phillipe; Tchounwou, Paul B.; Noumi, Emmanuel

2008-01-01

Macroinvertebrates identification and enumeration may be used as a simple and affordable alternative to chemical analysis in water pollution monitoring. However, the ecological responses of various taxa to pollution are poorly known in resources-limited tropical countries. While freshwater macroinvertebrates have been used in the assessment of water quality in Europe and the Americas, investigations in Africa have mainly focused on snail hosts of human parasites. There is a need for sampling methods that can be used to assess both snails and other macroinvertebrates. The present study was designed to evaluate the usefulness of the freshwater snail dip scoop method in the study of macroinvertebrates for the assessment of the SOSUCAM sugar mill effluents pollution. Standard snail dip scoop samples were collected upstream and downstream of the factory effluent inputs, on the Mokona and Mengoala rivers. The analysis of the macroinvertebrate communities revealed the absence of Ephemeroptera and Trichoptera, and the thriving of Syrphidae in the sections of the rivers under high effluent load. The Shannon & Weaver diversity index was lower in these areas. The dip scoop sampling protocol was found to be a useful method for macroinvertebrates collection. Hence, this method is recommended as a simple, cost-effective and efficient tool for the bio-assessment of freshwater pollution in developing countries with limited research resources. PMID:18441407

The value of the freshwater snail dip scoop sampling method in macroinvertebrates bioassessment of sugar mill wastewater pollution in Mbandjock, Cameroon.

PubMed

Takougang, Innocent; Barbazan, Phillipe; Tchounwou, Paul B; Noumi, Emmanuel

2008-03-01

Macroinvertebrates identification and enumeration may be used as a simple and affordable alternative to chemical analysis in water pollution monitoring. However, the ecological responses of various taxa to pollution are poorly known in resources-limited tropical countries. While freshwater macroinvertebrates have been used in the assessment of water quality in Europe and the Americas, investigations in Africa have mainly focused on snail hosts of human parasites. There is a need for sampling methods that can be used to assess both snails and other macroinvertebrates. The present study was designed to evaluate the usefulness of the freshwater snail dip scoop method in the study of macroinvertebrates for the assessment of the SOSUCAM sugar mill effluents pollution. Standard snail dip scoop samples were collected upstream and downstream of the factory effluent inputs, on the Mokona and Mengoala rivers. The analysis of the macroinvertebrate communities revealed the absence of Ephemeroptera and Trichoptera, and the thriving of Syrphidae in the sections of the rivers under high effluent load. The Shannon & Weaver diversity index was lower in these areas. The dip scoop sampling protocol was found to be a useful method for macroinvertebrates collection. Hence, this method is recommended as a simple, cost-effective and efficient tool for the bio-assessment of freshwater pollution in developing countries with limited research resources.

Circulating Biomphalaria glabrata hemocyte subpopulations possess shared schistosome glycans and receptors capable of binding larval glycoconjugates

PubMed Central

Yoshino, Timothy P.; Wu, Xiao-Jun; Gonzalez, Laura A.; Hokke, Cornelis H.

2013-01-01

Host lectin-like recognition molecules may play an important role in innate resistance in Biomphalaria glabrata snails to larval schistosome infection, thus implicating parasite-expressed glycans as putative ligands for these lectin receptors. While host lectins may utilize specific glycan structures for parasite recognition, it also has been hypothesized that the parasite may use this system to evade immune detection by mimicking naturally-expressed host glycans, resulting in reduced immunorecognition capacity. By employing immunocytochemical (ICC) and Western blot assays using schistosome glycan-specific monoclonal antibodies (mABs) we sought to identify specific glycan epitopes (glycotopes) shared in common between larval S. mansoni and B. glabrata hemocytes, the primary immune effector cells in snails. Results confirmed the presence of selected larval glycotopes on subpopulations of hemocytes by ICC and association with numerous hemocyte proteins by Western blot analyses, including a trimannosyl core N-glycan (TriMan), and two fucosylated lacdiNAc (LDN) variants, F-LDN and F-LDN-F. Snail strain differences were seen in the prevalence of constitutively expressed F-LDN on hemocytes, and in the patterns of protein immunoreactivity with these mABs. In contrast, there was little to no hemocyte reactivity with mABs for Lewis X (LeX), LDN, LDN-F or LDN-DF. When intact hemocytes were exposed to larval transformation products (LTPs), distinct cell subpopulations displayed weak (LeX, LDN-DF) to moderate (LDN, LDN-F) glycotope reactivity by ICC, including snail strain differences in the prevalence of LDN-reactive cellular subsets. Far-Western blot analyses of the hemocytes following exposure to larval transformation proteins (LTPs) also revealed multiple mAB-reactive hemocyte protein bands for LeX, LDN, LDN-F, and LDN-DF. These results demonstrate the existence of complex patterns of shared larval glycan constitutively expressed on hemocytes and their proteins, as well as the ability or hemocytes to acquire shared glycans by the selective binding of parasite-released LTP. Unraveling the functional significance of these naturally expressed and acquired shared glycans on specific hemocyte populations represents an important challenge for future investigations. PMID:23085445

aPKC-ι/P-Sp1/Snail signaling induces epithelial-mesenchymal transition and immunosuppression in cholangiocarcinoma.

PubMed

Qian, Yawei; Yao, Wei; Yang, Tao; Yang, Yan; Liu, Yan; Shen, Qi; Zhang, Jian; Qi, Weipeng; Wang, Jianming

2017-10-01

Cholangiocarcinoma (CCA) is a highly malignant bile duct cancer that tends to invade and metastasize early. The epithelial-mesenchymal transition (EMT) has been implicated in cancer cell invasion and metastasis, as well as in cancer cell evasion of host immunity. In this study, we investigated the interaction between atypical protein kinase C-iota (aPKC-ι) and Snail in the regulation of EMT and its relationship to CCA immunosuppression. Our results demonstrated that aPKC-ι, Snail, and infiltrated immunosuppressive cells were significantly up-regulated in CCA tumor tissues and linked to poor prognosis. aPKC-ι induced EMT and immunosuppression by regulating Snail in vitro and in vivo, although aPKC-ι did not directly interact with Snail in coimmunoprecipitation experiments. To further clarify the molecular interaction between aPKC-ι and Snail in relation to EMT, quantitative iTRAQ-based phosphoproteomic analysis and liquid chromatography-tandem mass spectrometry were conducted to identify the substrates of aPKC-ι-dependent phosphorylation. Combined with coimmunoprecipitation, we showed that specificity protein 1 (Sp1) was directly phosphorylated by aPKC-ι on Ser59 (P-Sp1). Both Sp1 and P-Sp1 were up-regulated in CCA tumor tissues and associated with clinicopathological features and poor prognosis in CCA patients. Moreover, using chromatin immunoprecipitation assays, we found that P-Sp1 regulated Snail expression by increasing Sp1 binding to the Snail promoter. P-Sp1 also regulated aPKC-ι/Snail-induced EMT-like changes and immunosuppression in CCA cells. Our findings further indicated that CCA cells with EMT-like features appear to generate immunosuppressive natural T regulatory-like cluster of differentiation 4-positive (CD4 + )CD25 - cells rather than to increase CD4 + CD25 + natural T regulatory cells, in part by mediating T regulatory-inducible cytokines such as transforming growth factor β1 and interleukin 2. These results demonstrate that aPKC-ι promotes EMT and induces immunosuppression through the aPKC-ι/P-Sp1/Snail signaling pathway and may be a potential therapeutic target for CCA. (Hepatology 2017;66:1165-1182). © 2017 by the American Association for the Study of Liver Diseases.

Effect of Intermediate Hosts on Emerging Zoonoses.

PubMed

Cui, Jing-An; Chen, Fangyuan; Fan, Shengjie

2017-08-01

Most emerging zoonotic pathogens originate from animals. They can directly infect humans through natural reservoirs or indirectly through intermediate hosts. As a bridge, an intermediate host plays different roles in the transmission of zoonotic pathogens. In this study, we present three types of pathogen transmission to evaluate the effect of intermediate hosts on emerging zoonotic diseases in human epidemics. These types are identified as follows: TYPE 1, pathogen transmission without an intermediate host for comparison; TYPE 2, pathogen transmission with an intermediate host as an amplifier; and TYPE 3, pathogen transmission with an intermediate host as a vessel for genetic variation. In addition, we established three mathematical models to elucidate the mechanisms underlying zoonotic disease transmission according to these three types. Stability analysis indicated that the existence of intermediate hosts increased the difficulty of controlling zoonotic diseases because of more difficult conditions to satisfy for the disease to die out. The human epidemic would die out under the following conditions: TYPE 1: [Formula: see text] and [Formula: see text]; TYPE 2: [Formula: see text], [Formula: see text], and [Formula: see text]; and TYPE 3: [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] Simulation with similar parameters demonstrated that intermediate hosts could change the peak time and number of infected humans during a human epidemic; intermediate hosts also exerted different effects on controlling the prevalence of a human epidemic with natural reservoirs in different periods, which is important in addressing problems in public health. Monitoring and controlling the number of natural reservoirs and intermediate hosts at the right time would successfully manage and prevent the prevalence of emerging zoonoses in humans.

Long-term impact of the World Bank Loan Project for schistosomiasis control: a comparison of the spatial distribution of schistosomiasis risk in China.

PubMed

Zhang, Zhijie; Zhu, Rong; Ward, Michael P; Xu, Wanghong; Zhang, Lijuan; Guo, Jiagang; Zhao, Fei; Jiang, Qingwu

2012-01-01

The World Bank Loan Project (WBLP) for controlling schistosomiasis in China was implemented during 1992-2001. Its short-term impact has been assessed from non-spatial perspective, but its long-term impact remains unclear and a spatial evaluation has not previously been conducted. Here we compared the spatial distribution of schistosomiasis risk using national datasets in the lake and marshland regions from 1999-2001 and 2007-2008 to evaluate the long-term impact of WBLP strategy on China's schistosomiasis burden. A hierarchical Poisson regression model was developed in a Bayesian framework with spatially correlated and uncorrelated heterogeneities at the county-level, modeled using a conditional autoregressive prior structure and a spatially unstructured Gaussian distribution, respectively. There were two important findings from this study. The WBLP strategy was found to have a good short-term impact on schistosomiasis control, but its long-term impact was not ideal. It has successfully reduced the morbidity of schistosomiasis to a low level, but can not contribute further to China's schistosomiasis control because of the current low endemic level. A second finding is that the WBLP strategy could not effectively compress the spatial distribution of schistosomiasis risk. To achieve further reductions in schistosomiasis-affected areas, and for sustainable control, focusing on the intermediate host snail should become the next step to interrupt schistosomiasis transmission within the two most affected regions surrounding the Dongting and Poyang Lakes. Furthermore, in the lower reaches of the Yangtze River, the WBLP's morbidity control strategy may need to continue for some time until snails in the upriver provinces have been well controlled. It is difficult to further reduce morbidity due to schistosomiasis using a chemotherapy-based control strategy in the lake and marshland regions of China because of the current low endemic levels of infection. The future control strategy for schistosomiasis should instead focus on a snail-based integrated control strategy to maintain the program achievements and sustainably reduce the burden of schistosomiasis in China.

Elimination of Schistosomiasis Transmission in Zanzibar: Baseline Findings before the Onset of a Randomized Intervention Trial

PubMed Central

Knopp, Stefanie; Person, Bobbie; Ame, Shaali M.; Mohammed, Khalfan A.; Ali, Said M.; Khamis, I. Simba; Rabone, Muriel; Allan, Fiona; Gouvras, Anouk; Blair, Lynsey; Fenwick, Alan; Utzinger, Jürg; Rollinson, David

2013-01-01

Background Gaining and sustaining control of schistosomiasis and, whenever feasible, achieving local elimination are the year 2020 targets set by the World Health Organization. In Zanzibar, various institutions and stakeholders have joined forces to eliminate urogenital schistosomiasis within 5 years. We report baseline findings before the onset of a randomized intervention trial designed to assess the differential impact of community-based praziquantel administration, snail control, and behavior change interventions. Methodology In early 2012, a baseline parasitological survey was conducted in ∼20,000 people from 90 communities in Unguja and Pemba. Risk factors for schistosomiasis were assessed by administering a questionnaire to adults. In selected communities, local knowledge about schistosomiasis transmission and prevention was determined in focus group discussions and in-depths interviews. Intermediate host snails were collected and examined for shedding of cercariae. Principal Findings The baseline Schistosoma haematobium prevalence in school children and adults was 4.3% (range: 0–19.7%) and 2.7% (range: 0–26.5%) in Unguja, and 8.9% (range: 0–31.8%) and 5.5% (range: 0–23.4%) in Pemba, respectively. Heavy infections were detected in 15.1% and 35.6% of the positive school children in Unguja and Pemba, respectively. Males were at higher risk than females (odds ratio (OR): 1.45; 95% confidence interval (CI): 1.03–2.03). Decreasing adult age (OR: 1.04; CI: 1.02–1.06), being born in Pemba (OR: 1.48; CI: 1.02–2.13) or Tanzania (OR: 2.36; CI: 1.16–4.78), and use of freshwater (OR: 2.15; CI: 1.53–3.03) showed higher odds of infection. Community knowledge about schistosomiasis was low. Only few infected Bulinus snails were found. Conclusions/Significance The relatively low S. haematobium prevalence in Zanzibar is a promising starting point for elimination. However, there is a need to improve community knowledge about disease transmission and prevention. Control measures tailored to the local context, placing particular attention to hot-spot areas, high-risk groups, and individuals, will be necessary if elimination is to be achieved. PMID:24147165

Life cycle of Renylaima capensis, a brachylaimid trematode of shrews and slugs in South Africa: two-host and three-host transmission modalities suggested by epizootiology and DNA sequencing

PubMed Central

2012-01-01

Background The life cycle of the brachylaimid trematode species Renylaima capensis, infecting the urinary system of the shrew Myosorex varius (Mammalia: Soricidae: Crocidosoricinae) in the Hottentots Holland Nature Reserve, South Africa, has been elucidated by a study of its larval stages, epizootiological data in local snails and mammals during a 34-year period, and its verification with mtDNA sequencing. Methods Parasites obtained from dissected animals were mounted in microscope slides for the parasitological study and measured according to standardized methods. The mitochondrial DNA cox1 gene was sequenced by the dideoxy chain-termination method. Results The slugs Ariostralis nebulosa and Ariopelta capensis (Gastropoda: Arionidae) act as specific first and second intermediate hosts, respectively. Branched sporocysts massively develop in A. nebulosa. Intrasporocystic mature cercariae show differentiated gonads, male terminal duct, ventral genital pore, and usually no tail, opposite to Brachylaimidae in which mature cercariae show a germinal primordium and small tail. Unencysted metacercariae, usually brevicaudate, infect the kidney of A. capensis and differ from mature cercariae by only a slightly greater size. The final microhabitats are the kidneys and ureters of the shrews, kidney pelvis and calyces in light infections and also kidney medulla and cortex in heavy infections. Sporocysts, cercariae, metacercariae and adults proved to belong to R. capensis by analysis of a 437-bp-long cox1 fragment, which was identical except for three mutations in metacercariae, of which only one silent. Epizootiological studies showed usual sporocyst infection in A. nebulosa and very rare metacercarial infection in A. capensis, which does not agree with high prevalences and intensities in the shrews. Conclusions The presence of monotesticular adult forms and larval prevalences and intensities observed suggest that R. capensis may use two transmission strategies, a two-host life cycle by predation of A. nebulosa harbouring intrasporocystic cercariae may be the normal pattern, whereas a second mollusc host is just starting to be introduced. In shrews, a tissue-traversing, intraorganic migration followed by an interorganic migration to reach and penetrate the outer surface of either of both kidneys should occur. For first slug infection, the fluke takes advantage of the phenomenon that M. varius always urinate during defaecation. Consequently, in Brachylaimidae, the second intermediate mollusc host should evolutionarily be seen as a last addition to the cycle and their present adult stage microhabitat restricted to digestive tract and related organs as a loss of the tissue-traversing capacity of the metacercaria. PMID:22889081

Stunting of the penis in Heleobia parchappii (Mollusca: Cochliopidae) and its relationship with parasitism.

PubMed

Merlo, Matías J; Parietti, Manuela; Etchegoin, Jorge A

2017-02-08

Penis anatomy is used to discriminate species of gastropods belonging to the family Cochliopidae; however, this characteristic may be affected by the presence of parasites. To evaluate the possible effect of parasites on penis length and number of papillae in Heleobia parchappii, 195 males were collected from the Nahuel Rucá Lagoon, Argentina. Male snails were only infected by trematode digeneans (total prevalence 45.13%). Three out of 9 species of digeneans registered showed prevalence values higher than 10%: Microphallus szidati, M. simillimus, and Notocotylidae sp. 1. The penis length of non-parasitized males and those parasitized by M. szidati and M. similimus increased with increased snail length; however, this increase was lower in infected snails. In the case of snails infected with Notocotylidae sp. 1, no relationship between shell length and penis length was apparent. Differences in the life cycles of these 3 digeneans could explain the null or lower penis growth rate in relation to host body growth. In contrast, no change was observed in the number of penial papillae of H. parchappii when these snails were infected by larval digeneans compared to those that were not infected. This indicates that penial papillae may be a more stable characteristic than penis length to discriminate between species within the Cochliopidae. The study of penial papillae should be central in the taxonomy and identification of new species within the Cochliopidae, as well as in previously described species.

Advances in the Diagnosis of Human Schistosomiasis

PubMed Central

Weerakoon, Kosala G. A. D.; Gobert, Geoffrey N.; Cai, Pengfei

2015-01-01

SUMMARY Schistosomiasis is a major neglected tropical disease that afflicts more than 240 million people, including many children and young adults, in the tropics and subtropics. The disease is characterized by chronic infections with significant residual morbidity and is of considerable public health importance, with substantial socioeconomic impacts on impoverished communities. Morbidity reduction and eventual elimination through integrated intervention measures are the focuses of current schistosomiasis control programs. Precise diagnosis of schistosome infections, in both mammalian and snail intermediate hosts, will play a pivotal role in achieving these goals. Nevertheless, despite extensive efforts over several decades, the search for sensitive and specific diagnostics for schistosomiasis is ongoing. Here we review the area, paying attention to earlier approaches but emphasizing recent developments in the search for new diagnostics for schistosomiasis with practical applications in the research laboratory, the clinic, and the field. Careful and rigorous validation of these assays and their cost-effectiveness will be needed, however, prior to their adoption in support of policy decisions for national public health programs aimed at the control and elimination of schistosomiasis. PMID:26224883

[Hygiene practices and contamination risks of surface waters by schistosome eggs: the case of an infested village in Northern Senegal].

PubMed

Sow, S; de Vlas, S J; Polman, K; Gryseels, B

2004-02-01

The transmission of intestinal schistosomiasis presumes that faecal materials containing viable schistosome eggs reach natural water bodies infested with snail intermediate host. So far there is little knowledge about the contamination dynamics of streams with schistosome eggs. We conducted a pilot study on defecating behaviour and hygienic practices in an Schistosoma mansoni endemic focus in Northern Senegal. Questionnaires were used to obtain quantitative data on hygienic practices and the use of latrines in 59 children. Although the community was well endowed with pit latrines, most of the children declared that they usually defecated somewhere else, in particular near the streams where the vegetation offers hideouts. Observations based on mapping of defecation sites showed that a considerable number of stools were left just a few meters from the riverbank, thus bearing a high risk of being washed off into the water. All these practices can easily lead to contamination of water bodies with schistosomae eggs. In order to improve hygienic practices and reduce fecal pollution of the environment, a health education model respecting local beliefs and customs would be indispensable.

Transcriptomic responses of Biomphalaria pfeifferi to Schistosoma mansoni: Investigation of a neglected African snail that supports more S. mansoni transmission than any other snail species

PubMed Central

Bu, Lijing; Zhang, Si-Ming; Schilkey, Faye D.; Mkoji, Gerald M.; Loker, Eric S.

2017-01-01

Background Biomphalaria pfeifferi is highly compatible with the widespread human-infecting blood fluke Schistosoma mansoni and transmits more cases of this parasite to people than any other snail species. For these reasons, B. pfeifferi is the world’s most important vector snail for S. mansoni, yet we know relatively little at the molecular level regarding the interactions between B. pfeifferi and S. mansoni from early-stage sporocyst transformation to the development of cercariae. Methodology/Principal findings We sought to capture a portrait of the response of B. pfeifferi to S. mansoni as it occurs in nature by undertaking Illumina dual RNA-Seq on uninfected control B. pfeifferi and three intramolluscan developmental stages (1- and 3-days post infection and patent, cercariae-producing infections) using field-derived west Kenyan specimens. A high-quality, well-annotated de novo B. pfeifferi transcriptome was assembled from over a half billion non-S. mansoni paired-end reads. Reads associated with potential symbionts were noted. Some infected snails yielded fewer normalized S. mansoni reads and showed different patterns of transcriptional response than others, an indication that the ability of field-derived snails to support and respond to infection is variable. Alterations in transcripts associated with reproduction were noted, including for the oviposition-related hormone ovipostatin and enzymes involved in metabolism of bioactive amines like dopamine or serotonin. Shedding snails exhibited responses consistent with the need for tissue repair. Both generalized stress and immune factors immune factors (VIgLs, PGRPs, BGBPs, complement C1q-like, chitinases) exhibited complex transcriptional responses in this compatible host-parasite system. Significance This study provides for the first time a large sequence data set to help in interpreting the important vector role of the neglected snail B. pfeifferi in transmission of S. mansoni, including with an emphasis on more natural, field-derived specimens. We have identified B. pfeifferi targets particularly responsive during infection that enable further dissection of the functional role of these candidate molecules. PMID:29045404

Self-fertilization, long-distance flash invasion and biogeography shape the population structure of Pseudosuccinea columella at the worldwide scale.

PubMed

Lounnas, M; Correa, A C; Vázquez, A A; Dia, A; Escobar, J S; Nicot, A; Arenas, J; Ayaqui, R; Dubois, M P; Gimenez, T; Gutiérrez, A; González-Ramírez, C; Noya, O; Prepelitchi, L; Uribe, N; Wisnivesky-Colli, C; Yong, M; David, P; Loker, E S; Jarne, P; Pointier, J P; Hurtrez-Boussès, S

2017-02-01

Population genetic studies are efficient for inferring the invasion history based on a comparison of native and invasive populations, especially when conducted at species scale. An expected outcome in invasive populations is variability loss, and this is especially true in self-fertilizing species. We here focus on the self-fertilizing Pseudosuccinea columella, an invasive hermaphroditic freshwater snail that has greatly expanded its geographic distribution and that acts as intermediate host of Fasciola hepatica, the causative agent of human and veterinary fasciolosis. We evaluated the distribution of genetic diversity at the largest geographic scale analysed to date in this species by surveying 80 populations collected during 16 years from 14 countries, using eight nuclear microsatellites and two mitochondrial genes. As expected, populations from North America, the putative origin area, were strongly structured by selfing and history and harboured much more genetic variability than invasive populations. We found high selfing rates (when it was possible to infer it), none-to-low genetic variability and strong population structure in most invasive populations. Strikingly, we found a unique genotype/haplotype in populations from eight invaded regions sampled all over the world. Moreover, snail populations resistant to infection by the parasite are genetically distinct from susceptible populations. Our results are compatible with repeated introductions in South America and flash worldwide invasion by this unique genotype/haplotype. Our study illustrates the population genetic consequences of biological invasion in a highly selfing species at very large geographic scale. We discuss how such a large-scale flash invasion may affect the spread of fasciolosis. © 2016 John Wiley & Sons Ltd.

Green garden snail, Cantareus apertus, as biomonitor and sentinel for integrative metal pollution assessment in roadside soils.

PubMed

Mleiki, Anwar; Marigómez, Ionan; El Menif, Najoua Trigui

2017-11-01

The present investigation was conceived to study, in a small scale field study, the potential of the green garden snail, Cantareus apertus, as biomonitor and sentinel for integrative metal pollution assessment in soils. For this purpose, we investigated the association between the trace metal (Cd, Pb, As, Fe, Cr, Cu, Ni, and Zn) concentrations in soil, plants (Trifolium repens), and C. apertus depending on the distance (20, 150, and 700 m) from a main roadside in Tunisia as well as between metal concentrations and biomarkers of oxidative stress, oxidative damage, and neurotoxicity in C. apertus. Results revealed a clear association between the concentration of metals such as Ni, Cu, and Zn in snail digestive gland, both amongst them and with oxidative stress and neurotoxicity biomarkers recorded in the same organ. Interestingly, Ni, Pb, and Zn occurred at the highest concentration in soil, plant, and snails and the association appeared related to the immediacy of the roadside and the concentration of these three metals tended to decrease with distance from the roadside in the soil-plant-snail system. Conversely, Cd and Cu were bioaccumulated in plants and snails but their concentrations in soil were not high and did not show a decline in concentration with distance from the roadside. After PCA analysis, PC-01 (56% of the variance) represented metal bioaccumulation and associated toxic effects in snails in the presence of high levels of metal pollution (nearby the roadside) while PC-02 (35% of the variance) represented stress induced by moderate levels of metal pollution (at intermediate distances from the roadside). The four studied sites were clearly discriminated one from each other, depending on how they are affected by traffic pollution. In summary, this field study reveals that (a) C. apertus can be used as biomonitor for metal pollution in roadside soils and as sentinel for pollution effects assessment based on biochemical biomarkers; and (b) that oxidative stress and neurotoxicity biomarkers endow with a powerful biological tool for metal pollution biomonitoring in soils, especially in combination with chemical analysis of the soil-plant-snail transfer system. Moreover, this study provides some baseline data for future impact assessments concerning trace metal pollution in Tunisia.

Presumable incipient hybrid speciation of door snails in previously glaciated areas in the Caucasus.

PubMed

Koch, Eva L; Neiber, Marco T; Walther, Frank; Hausdorf, Bernhard

2016-04-01

Homoploid hybrid speciation, speciation by hybridization without a change in chromosome number, may be the result of an encounter of closely related species in a habitat that is different from that usually occupied by these species. In the northwestern Caucasus the land snail species Micropontica caucasica and M. circassica form two distinct entities with little admixture at low and intermediate altitudes. However, at higher altitudes in the Lagonaki plateau, which were repeatedly glaciated, Micropontica populations with intermediate characters occur. Admixture analyses based on AFLP data demonstrated that the populations from the Lagonaki plateau are homoploid hybrids that now form a cluster separate from the parental species. The Lagonaki populations are characterized by a mtDNA haplotype clade that has been found in the parental species only once. The fixation of this haplotype clade in most hybrid populations suggests that these haplotypes are better adapted to the cooler conditions in high altitude habitats and have replaced the haplotypes of the parental species in a selective sweep. The fixation of a presumably adaptive mitochondrial haplotype clade in the Lagonaki populations is an important step towards speciation under the differential fitness species concept. Copyright © 2015 Elsevier Inc. All rights reserved.

Allying with armored snails: the complete genome of gammaproteobacterial endosymbiont.

PubMed

Nakagawa, Satoshi; Shimamura, Shigeru; Takaki, Yoshihiro; Suzuki, Yohey; Murakami, Shun-ichi; Watanabe, Tamaki; Fujiyoshi, So; Mino, Sayaka; Sawabe, Tomoo; Maeda, Takahiro; Makita, Hiroko; Nemoto, Suguru; Nishimura, Shin-Ichiro; Watanabe, Hiromi; Watsuji, Tomo-o; Takai, Ken

2014-01-01

Deep-sea vents harbor dense populations of various animals that have their specific symbiotic bacteria. Scaly-foot gastropods, which are snails with mineralized scales covering the sides of its foot, have a gammaproteobacterial endosymbiont in their enlarged esophageal glands and diverse epibionts on the surface of their scales. In this study, we report the complete genome sequencing of gammaproteobacterial endosymbiont. The endosymbiont genome displays features consistent with ongoing genome reduction such as large proportions of pseudogenes and insertion elements. The genome encodes functions commonly found in deep-sea vent chemoautotrophs such as sulfur oxidation and carbon fixation. Stable carbon isotope ((13)C)-labeling experiments confirmed the endosymbiont chemoautotrophy. The genome also includes an intact hydrogenase gene cluster that potentially has been horizontally transferred from phylogenetically distant bacteria. Notable findings include the presence and transcription of genes for flagellar assembly, through which proteins are potentially exported from bacterium to the host. Symbionts of snail individuals exhibited extreme genetic homogeneity, showing only two synonymous changes in 19 different genes (13 810 positions in total) determined for 32 individual gastropods collected from a single colony at one time. The extremely low genetic individuality in endosymbionts probably reflects that the stringent symbiont selection by host prevents the random genetic drift in the small population of horizontally transmitted symbiont. This study is the first complete genome analysis of gastropod endosymbiont and offers an opportunity to study genome evolution in a recently evolved endosymbiont.

Hosts and parasites as aliens.

PubMed

Taraschewski, H

2006-06-01

Over the past decades, various free-living animals (hosts) and their parasites have invaded recipient areas in which they had not previously occurred, thus gaining the status of aliens or exotics. In general this happened to a low extent for hundreds of years. With variable frequency, invasions have been followed by the dispersal and establishment of non-indigenous species, whether host or parasite. In the literature thus far, colonizations by both hosts and parasites have not been treated and reviewed together, although both are usually interwoven in various ways. As to those factors permitting invasive success and colonization strength, various hypotheses have been put forward depending on the scientific background of respective authors and on the conspicuousness of certain invasions. Researchers who have tried to analyse characteristic developmental patterns, the speed of dispersal or the degree of genetic divergence in populations of alien species have come to different conclusions. Among parasitologists, the applied aspects of parasite invasions, such as the negative effects on economically important hosts, have long been at the centre of interest. In this contribution, invasions by hosts as well as parasites are considered comparatively, revealing many similarities and a few differences. Two helminths, the liver fluke, Fasciola hepatica, of cattle and sheep and the swimbladder nematode, Anguillicola crassus, of eels are shown to be useful as model parasites for the study of animal invasions and environmental global change. Introductions of F. hepatica have been associated with imports of cattle or other grazing animals. In various target areas, susceptible lymnaeid snails serving as intermediate hosts were either naturally present and/or were introduced from the donor continent of the parasite (Europe) and/or from other regions which were not within the original range of the parasite, partly reflecting progressive stages of a global biota change. In several introduced areas, F. hepatica co-occurs with native or exotic populations of the congeneric F. gigantica, with thus far unknown implications. Over the fluke's extended range, in addition to domestic stock animals, wild native or naturalized mammals can also serve as final hosts. Indigenous and displaced populations of F. hepatica, however, have not yet been studied comparatively from an evolutionary perspective. A. crassus, from the Far East, has invaded three continents, without the previous naturalization of its natural host Anguilla japonica, by switching to the respective indigenous eel species. Local entomostrac crustaceans serve as susceptible intermediate hosts. The novel final hosts turned out to be naive in respect to the introduced nematode with far reaching consequences for the parasite's morphology (size), abundance and pathogenicity. Comparative infection experiments with Japanese and European eels yielded many differences in the hosts' immune defence, mirroring coevolution versus an abrupt host switch associated with the introduction of the helminth. In other associations of native hosts and invasive parasites, the elevated pathogenicity of the parasite seems to result from other deficiencies such as a lack of anti-parasitic behaviour of the naïve host compared to the donor host which displays distinct behavioural patterns, keeping the abundance of the parasite low. From the small amount of available literature, it can be concluded that the adaptation of certain populations of the novel host to the alien parasite takes several decades to a century or more. Summarizing all we know about hosts and parasites as aliens, tentative patterns and principles can be figured out, but individual case studies teach us that generalizations should be avoided.

Productivity and fishing pressure drive variability in fish parasite assemblages of the Line Islands, equatorial Pacific.

PubMed

Wood, Chelsea L; Baum, Julia K; Reddy, Sheila M W; Trebilco, Rowan; Sandin, Stuart A; Zgliczynski, Brian J; Briggs, Amy A; Micheli, Fiorenza

2015-05-01

Variability in primary productivity and fishing pressure can shape the abundance, species composition, and diversity of marine life. Though parasites comprise nearly half of marine species, their responses to these important forces remain little explored. We quantified parasite assemblages at two spatial scales, across a gradient in productivity and fishing pressure that spans six coral islands of the Line Islands archipelago and within the largest Line Island, Kiritimati, which experiences a west-to-east gradient in fishing pressure and upwelling-driven productivity. In the across-islands data set, we found that increasing productivity was correlated with increased parasite abundance overall, but that the effects of productivity differed among parasite groups. Trophically transmitted parasites increased in abundance with increasing productivity, but directly transmitted parasites did not exhibit significant changes. This probably arises because productivity has stronger effects on the abundance of the planktonic crustaceans and herbivorous snails that serve as the intermediate hosts of trophically transmitted parasites than on the higher-trophic level fishes that are the sole hosts of directly transmitted parasites. We also found that specialist parasites increased in response to increasing productivity, while generalists did not, possibly because specialist parasites tend to be more strongly limited by host availability than are generalist parasites. After the effect of productivity was controlled for, fishing was correlated with decreases in the abundance of trophically transmitted parasites, while directly transmitted parasites appeared to track host density; we observed increases in the abundance of parasites using hosts that experienced fishing-driven compensatory increases in abundance. The within-island data set confirmed these patterns for the combined effects of productivity and fishing on parasite abundance, suggesting that our conclusions are robust across a span of spatial scales. Overall, these results indicate that there are strong and variable effects of anthropogenic and natural drivers on parasite abundance and taxonomic richness. These effects are likely to be mediated by parasite traits, particularly by parasite transmission strategies.

TREMATODES IN SNAILS NEAR RACCOON LATRINES SUGGEST A FINAL HOST ROLE FOR THIS MAMMAL IN CALIFORNIA SALT MARSHES. (R828676C001)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Manipulative parasites may not alter intermediate host distribution but still enhance their transmission: field evidence for increased vulnerability to definitive hosts and non-host predator avoidance.

PubMed

Lagrue, C; Güvenatam, A; Bollache, L

2013-02-01

Behavioural alterations induced by parasites in their intermediate hosts can spatially structure host populations, possibly resulting in enhanced trophic transmission to definitive hosts. However, such alterations may also increase intermediate host vulnerability to non-host predators. Parasite-induced behavioural alterations may thus vary between parasite species and depend on each parasite definitive host species. We studied the influence of infection with 2 acanthocephalan parasites (Echinorhynchus truttae and Polymorphus minutus) on the distribution of the amphipod Gammarus pulex in the field. Predator presence or absence and predator species, whether suitable definitive host or dead-end predator, had no effect on the micro-distribution of infected or uninfected G. pulex amphipods. Although neither parasite species seem to influence intermediate host distribution, E. truttae infected G. pulex were still significantly more vulnerable to predation by fish (Cottus gobio), the parasite's definitive hosts. In contrast, G. pulex infected with P. minutus, a bird acanthocephalan, did not suffer from increased predation by C. gobio, a predator unsuitable as host for P. minutus. These results suggest that effects of behavioural changes associated with parasite infections might not be detectable until intermediate hosts actually come in contact with predators. However, parasite-induced changes in host spatial distribution may still be adaptive if they drive hosts into areas of high transmission probabilities.

Lipids analysis in hemolymph of African giant Achatina fulica (Bowdich, 1822) exposed to different photoperiods.

PubMed

Lustrino, D; Tunholi-Alves, V M; Tunholi, V M; Marassi, M P; Pinheiro, J

2010-02-01

The influence of different photophases (0, 6, 12, 18 and 24 hours) on the triglycerides and total cholesterol contents in the hemolymph of A. fulica was evaluated, since there is no information in the literature about the influence of this factor on lipids metabolism in mollusks. After 2 and 4 weeks of exposure the snails were dissected. The cholesterol content at the 2nd and 4th weeks post exposure only varied significantly in the groups exposed at 24 hours and 0 hour of photophase, respectively. Probably, such increase may be a result of a rise in cholesterol biosynthesis and/or remodelling of cell membranes. There were no significant differences among the content of triglycerides in the snails exposed to 6, 12, 18 and 24 hours of photophase during two weeks. The snails exposed to intermediate photophase (6 and 12 hours) had the triglycerides content increased, ranging over values near to those observed in the group exposed to 0 hour. Results showed that triglycerides metabolism in A. fulica are more influenced by photoperiod than cholesterol metabolism. A negative relation is maintained between the triglycerides content in the hemolymph and the different photophases, with lower mobilisation of triglycerides under shorter photophases.

The basic reproductive ratio of Barbour's two-host schistosomiasis model with seasonal fluctuations.

PubMed

Gao, Shu-Jing; Cao, Hua-Hua; He, Yu-Ying; Liu, Yu-Jiang; Zhang, Xiang-Yu; Yang, Guo-Jing; Zhou, Xiao-Nong

2017-01-25

Motivated by the first mathematical model for schistosomiasis proposed by Macdonald and Barbour's classical schistosomiasis model tracking the dynamics of infected human population and infected snail hosts in a community, in our previous study, we incorporated seasonal fluctuations into Barbour's model, but ignored the effect of bovine reservoir host in the transmission of schistosomiasis. Inspired by the findings from our previous work, the model was further improved by integrating two definitive hosts (human and bovine) and seasonal fluctuations, so as to understand the transmission dynamics of schistosomiasis japonica and evaluate the ongoing control measures in Liaonan village, Xingzi County, Jiangxi Province. The basic reproductive ratio R 0 and its computation formulae were derived by using the operator theory in functional analysis and the monodromy matrix theory. The mathematical methods for global dynamics of periodic systems were used in order to show that R 0 serves as a threshold value that determines whether there was disease outbreak or not. The parameter fitting and the ratio calculation were performed with surveillance data obtained from the village of Liaonan using numerical simulation. Sensitivity analysis was carried out in order to understand the impact of R 0 on seasonal fluctuations and snail host control. The modified basic reproductive ratios were compared with known results to illustrate the infection risk. The Barbour's two-host model with seasonal fluctuations was proposed. The implicit expression of R 0 for the model was given by the spectral radius of next infection operator. The R 0 s for the model ranged between 1.030 and 1.097 from 2003 to 2010 in the village of Liaonan, Xingzi County, China, with 1.097 recorded as the maximum value in 2005 but declined dramatically afterwards. In addition, we proved that the disease goes into extinction when R 0 is less than one and persists when R 0 is greater than one. Comparisons of the different improved models were also made. Based on the mechanism and characteristics of schistosomiasis transmission, Barbour's model was improved by considering seasonality. The implicit formula of R 0 for the model and its calculation were given. Theoretical results showed that R 0 gave a sharp threshold that determines whether the disease dies out or not. Simulations concluded that: (i) ignoring seasonality would overestimate the transmission risk of schistosomiasis, and (ii) mollusiciding is an effective control measure to curtail schistosomiasis transmission in Xingzi County when the removal rate of infected snails is small.

Low susceptibility of Achatina fulica from Brazil to infection with AngioIylus costaricensis and A. cantonensis.

PubMed

Neuhauss, Erli; Fitarelli, Monaliza; Romanzini, Juliano; Graeff-Teixeira, Carlos

2007-02-01

Introduction of Achatina fulica in Brazil has led to serious concerns about its role as vector for metaIylid worms: AngioIylus costaricensis and A. cantonensis. Experimental infection with both parasites was performed to evaluate the potential risk for their transmission by the giant African snail. Groups of 5 animals, both wild and bred at captivity were exposed at different inocula: 1, 5, and 10 x 10(3) L1 of A. costaricensis and A. cantonensis. In all groups, few snails got infected and parasitic burden was low. Two different ways of infection were tested: ingestion produced higher numbers of L3 than the inoculation through an artificial hole in the shell. We also report the parasitological examination of 6 batches of wild A. fulica from Florianópolis, state of Santa Catarina, Brazil: only 1 out of 244 animals were infected with metaIylid larvae. Taken together these data indicate that the giant African snail occurring in Southern Brazil is not a permissive host for both AngioIylus species and does not represent a significant risk for transmission of these parasites.

A global network for the control of snail-borne disease using satellite surveillance and geographic information systems.

PubMed

Malone, J B; Bergquist, N R; Huh, O K; Bavia, M E; Bernardi, M; El Bahy, M M; Fuentes, M V; Kristensen, T K; McCarroll, J C; Yilma, J M; Zhou, X N

2001-04-27

At a team residency sponsored by the Rockefeller Foundation in Bellagio, Italy, 10-14 April 2000 an organizational plan was conceived to create a global network of collaborating health workers and earth scientists dedicated to the development of computer-based models that can be used for improved control programs for schistosomiasis and other snail-borne diseases of medical and veterinary importance. The models will be assembled using GIS methods, global climate model data, sensor data from earth observing satellites, disease prevalence data, the distribution and abundance of snail hosts, and digital maps of key environmental factors that affect development and propagation of snail-borne disease agents. A work plan was developed for research collaboration and data sharing, recruitment of new contributing researchers, and means of access of other medical scientists and national control program managers to GIS models that may be used for more effective control of snail-borne disease. Agreement was reached on the use of compatible GIS formats, software, methods and data resources, including the definition of a 'minimum medical database' to enable seamless incorporation of results from each regional GIS project into a global model. The collaboration plan calls for linking a 'central resource group' at the World Health Organization, the Food and Agriculture Organization, Louisiana State University and the Danish Bilharziasis Laboratory with regional GIS networks to be initiated in Eastern Africa, Southern Africa, West Africa, Latin America and Southern Asia. An Internet site, www.gnosisGIS.org, (GIS Network On Snail-borne Infections with special reference to Schistosomiasis), has been initiated to allow interaction of team members as a 'virtual research group'. When completed, the site will point users to a toolbox of common resources resident on computers at member organizations, provide assistance on routine use of GIS health maps in selected national disease control programs and provide a forum for development of GIS models to predict the health impacts of water development projects and climate variation.

Molecular Analysis of Echinostome Metacercariae from Their Second Intermediate Host Found in a Localised Geographic Region Reveals Genetic Heterogeneity and Possible Cryptic Speciation

PubMed Central

Noikong, Waraporn; Wongsawad, Chalobol; Chai, Jong-Yil; Saenphet, Supap; Trudgett, Alan

2014-01-01

Echinostome metacercariae are the infective stage for humans and animals. The identification of echinostomes has been based until recently on morphology but molecular techniques using sequences of ribosomal RNA and mitochondrial DNA have indicated major clades within the group. In this study we have used the ITS2 region of ribosomal RNA and the ND1 region of mitochondrial DNA to identify metacercariae from snails collected from eight well-separated sites from an area of 4000 km2 in Lamphun Province, Thailand. The derived sequences have been compared to those collected from elsewhere and have been deposited in the nucleotide databases. There were two aims of this study; firstly, to determine the species of echinostome present in an endemic area, and secondly, to assess the intra-specific genetic diversity, as this may be informative with regard to the potential for the development of anthelmintic resistance and with regard to the spread of infection by the definitive hosts. Our results indicate that the most prevalent species are most closely related to E. revolutum, E. trivolvis, E. robustum, E. malayanum and Euparyphium albuferensis. Some sites harbour several species and within a site there could be considerable intra-species genetic diversity. There is no significant geographical structuring within this area. Although the molecular techniques used in this study allowed the assignment of the samples to clades within defined species, however, within these groupings there were significant differences indicating that cryptic speciation may have occurred. The degree of genetic diversity present would suggest the use of targeted regimes designed to minimise the selection of anthelmintic resistance. The apparent lack of geographic structuring is consistent with the transmission of the parasites by the avian hosts. PMID:24699358

The importance of wild fish in the epidemiology of Clonorchis sinensis in Vietnam.

PubMed

Bui, Thanh Ngoc; Pham, Thanh Thi; Nguyen, Nguyen Thi; Nguyen, Ha Van; Murrell, Darwin; Phan, Van Thi

2016-09-01

Preliminary findings of a high prevalence of Clonorchis sinensis in wild-caught fish in a North Vietnam reservoir (Thac Ba reservoir, Yen Bai Province) prompted a longitudinal epidemiological study of fish infections. Monthly collections of fish from September 2014 to August 2015 were processed for recovery of metacercariae; 1219 fish, representing 22 species, were examined. Seven species were infected with C. sinensis metacercariae. Four species, Toxabramis houdemeri, Hemiculter leucisculus, Cultrichthys erythropterus, and Culter recurvirostris, had high prevalence (31.1 to 76.7 %); metacercarial intensities ranged from 3.9 to 65.7 metacercariae/fish. A seasonal variation of C. sinensis prevalence was observed in T. houdemeri. Variation in intensity of infection occurred in C. erythropterus and H. leucisculus. Intensity and prevalence of C. sinensis in the most highly infected species, T. houdemeri, varied by fish size; prevalence was higher in fish weighing more than 3 g, and intensity was higher in fish weighing more than 5 g. The distribution of metacercariae in the body region of T. houdemeri was significantly higher in the caudal fin (14.7 metacercariae/g), compared to the body and head regions (0.7 and 1.4 metacercariae/g, respectively). Further epidemiological investigations on C. sinensis in this reservoir region should include assessing the relative risk of the different fish species for humans based on the latter's food preferences, and the prevalence of C. sinensis in the community. The snail intermediate host(s) in the reservoir should also be identified along with the ecological factors influencing its exposure to C. sinensis eggs and its subsequent transmission of cercariae to fish. Also needed are investigations on the relative importance of wild and domestic reservoir hosts as sources of egg contamination of the reservoir.

Gastropod-derived haemocyte extracellular traps entrap metastrongyloid larval stages of Angiostrongylus vasorum, Aelurostrongylus abstrusus and Troglostrongylus brevior.

PubMed

Lange, Malin K; Penagos-Tabares, Felipe; Muñoz-Caro, Tamara; Gärtner, Ulrich; Mejer, Helena; Schaper, Roland; Hermosilla, Carlos; Taubert, Anja

2017-01-31

Phagocyte-derived extracellular traps (ETs) were recently demonstrated mainly in vertebrate hosts as an important effector mechanism against invading parasites. In the present study we aimed to characterize gastropod-derived invertebrate extracellular phagocyte trap (InEPT) formation in response to larval stages of important canine and feline metastrongyloid lungworms. Gastropod haemocytes were isolated from the slug species Arion lusitanicus and Limax maximus, and the snail Achatina fulica, and exposed to larval stages of Angiostrongylus vasorum, Aelurostrongylus abstrusus and Troglostrongylus brevior and investigated for gastropod-derived InEPT formation. Phase contrast as well as scanning electron microscopy (SEM) analyses of lungworm larvae-exposed haemocytes revealed ET-like structures to be extruded by haemocytes thereby contacting and ensnaring the parasites. Co-localization studies of haemocyte-derived extracellular DNA with histones and myeloperoxidase in larvae-entrapping structures confirmed classical characteristics of ETs. In vivo exposure of slugs to A. vasorum larvae resulted in InEPTs being extruded from haemocytes in the slug mucous extrapallial space emphasizing the pivotal role of this effector mechanism against invasive larvae. Functional larval entrapment assays demonstrated that almost half of the haemocyte-exposed larvae were contacted or even immobilized by released InEPTs. Overall, as reported for mammalian-derived ETs, different types of InEPTs were here observed, i.e. aggregated, spread and diffused InEPTs. To our knowledge, this study represents the first report on metastrongyloid lungworm-triggered ETosis in gastropods thereby providing evidence of early mollusc host innate immune reactions against invading larvae. These findings will contribute to the better understanding on complex parasite-intermediate host interactions since different gastropod species bear different transmitting capacities for metastrongyloid infections.

Snail phenotypic variation and stress proteins: do different heat response strategies contribute to Waddington's widget in field populations?

PubMed

Köhler, Heinz-R; Lazzara, Raimondo; Dittbrenner, Nils; Capowiez, Yvan; Mazzia, Christophe; Triebskorn, Rita

2009-03-15

On the basis of studies with laboratory strains of Drosophila and Arabidopsis, it has been hypothesized that potential buffers to the expression of phenotypic morphological variation, such as Hsp90 and possibly Hsp70, represent important components of Waddington's widget, which may confer capacitive evolution. As studies on field populations of living organisms to test this hypothesis are lacking, we tested whether a heat response strategy involving high stress protein levels is associated with low morphological variation and vice versa, using four natural populations of Mediterranean pulmonate snails. In response to 8 hr of elevated temperatures, a population of Xeropicta derbentina with uniform shell pigmentation pattern showed remarkably high Hsp70 but low Hsp90 levels. In contrast, a highly variable population of Cernuella virgata kept both Hsp90 and Hsp70 levels low when held at diverse though environmentally relevant temperatures. Two other populations (Theba pisana and another X. derbentina population) with intermediate variation in shell pigmentation pattern were also intermediate in inducing Hsp70, though Hsp90 was maintained at a low level. The observed correlation of stress protein levels and coloration pattern variation provide the first indirect evidence for an association of stress proteins with Waddington's widget under natural conditions.

Molluscicidal activity and mechanism of toxicity of a novel salicylanilide ester derivative against Biomphalaria species.

PubMed

He, Ping; Wang, Weisi; Sanogo, Benjamin; Zeng, Xin; Sun, Xi; Lv, Zhiyue; Yuan, Dongjuan; Duan, Liping; Wu, Zhongdao

2017-08-10

Schistosomiasis mansoni is one of the most important, but often neglected, tropical diseases transmitted by snails of the genus Biomphalaria. Control of the intermediate host snail plays a crucial role in preventing the spread of schistosomiasis. However, there is only one molluscicide, niclosamide, recommended by the World Health Organization. Niclosamide has been used for several decades but is toxic to non-target organisms. Therefore, it is necessary to optimize the scaffold of niclosamide and develop novel molluscicides with enhanced potency and decreased toxicity to non-target organisms. In this study, a candidate compound was analyzed by nuclear magnetic resonance and mass spectrometry. The molluscicidal potential against Biomphalaria species and cercaricidal potential against S. mansoni were evaluated using the immersion method. Furthermore, the preliminary mechanism was studied through cellular enzyme tests and electron microscopy. 5-chloro-2-[(2-chloro-4-nitrophenyl)carbamoyl]phenyl-4-methoxybenzoate (salicylanilidate), a novel salicylanilide ester derivative, was derived from niclosamide. The 50% lethal concentration to B. glabrata, B. straminea and B. pfeifferi was 0.261 mg/l, 0.172 mg/l and 0.241 mg/l, respectively. The effective dose required to completely kill S. mansoni cercariae was 0.625 mg/l for salicylanilidate and 0.125 mg/l for niclosamide. However, salicylanilidate was approximately 100-fold less toxic to the fish Danio rerio than niclosamide. Furthermore, salicylanilidate reduced the enzymatic activities of nitric oxide synthase (NOS), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE) in the snail, demonstrating that it could affect neurohypophysis transmission and energy metabolism. Severe swelling in the tentacle and deformation of cilia in the tentacle and mantle were observed through scanning electron microscopy. The results of transmission electron microscopy showed that salicylanilidate could damage critical organelles in hepatopancreas tissues, including degeneration of the endoplasmic reticulum and vacuolization in mitochondria. In addition, transcriptional levels of superoxide dismutase (SOD), acid phosphatase (ACP) and NOS in the hepatopancreas were significantly downregulated as shown by real-time quantitative polymerase chain reaction (RT-PCR). These results indicated that the hepatopancreas is a primary target organ of salicylanilidate. Salicylanilidate not only had deleterious effects on Biomphalaria species and S. mansoni cercariae but also showed very low toxicity to D. rerio, suggesting that it has broad potential applications.

Potential interactions between metazoan parasites of the Mayan catfish Ariopsis assimilis and chemical pollution in Chetumal Bay, Mexico.

PubMed

Vidal-Martínez, V M; Aguirre-Macedo, M L; Noreña-Barroso, E; Gold-Bouchot, G; Caballero-Pinzón, P I

2003-06-01

The effect of pollutants on the intensity of infection of metazoan parasites in the Mayan catfish, Ariopsis assimilis was investigated. Data were collected on pollutants and metazoan parasites from 76 catfish from five localities in Chetumal Bay in October, 1996. Nineteen pollutants (pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs)) were found in the catfish livers. Heavy metal content was not determined. Nineteen metazoan parasite species were recovered. After controlling for fish length and sampling station, there was a significant negative linear relationship between the intensity of the larval digenean Mesostephanus appendiculatoides and 1,1,1,-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) concentrations. This negative relationship may be explained either by the effect of the pesticide on the mortality of (i) free-living larval forms, (ii) metacercariae in the fish, (iii) infected fish or (iv) intermediate host snails. There were significant differences between fish parasitized and not parasitized with M. appendiculatoides with respect to their DDT concentrations. There were also significant differences between the variances of the mean Clark's coefficient of condition values between catfish parasitized and not parasitized by M. appendiculatoides, with the variance of non-parasitized catfish being significantly larger. The results provided statistical evidence that DDT has a detrimental effect on M. appendiculatoides infection intensity. Furthermore, the significantly larger variance value of Clark's coefficient for non-parasitized fish suggested that DDT affects both the parasite and general host condition.

Safe, Effective Use of Pesticides, A Manual for Commercial Applicators: Public Health Pest Control.

ERIC Educational Resources Information Center

Extension Service (USDA), Washington, DC.

This manual is designed to assist public health pest control officials in meeting the certification required under the Michigan Pesticide Control Act of 1976. The four sections included describe: (1) Insects of public health significance in Michigan; (2) Other arthropods that affect man; (3) Swimmers' itch parasite and snail host; and (4)…

Metagenomic Analysis of the Microbiota from the Crop of an Invasive Snail Reveals a Rich Reservoir of Novel Genes

PubMed Central

Cardoso, Alexander M.; Cavalcante, Janaína J. V.; Cantão, Maurício E.; Thompson, Claudia E.; Flatschart, Roberto B.; Glogauer, Arnaldo; Scapin, Sandra M. N.; Sade, Youssef B.; Beltrão, Paulo J. M. S. I.; Gerber, Alexandra L.; Martins, Orlando B.; Garcia, Eloi S.; de Souza, Wanderley; Vasconcelos, Ana Tereza R.

2012-01-01

The shortage of petroleum reserves and the increase in CO2 emissions have raised global concerns and highlighted the importance of adopting sustainable energy sources. Second-generation ethanol made from lignocellulosic materials is considered to be one of the most promising fuels for vehicles. The giant snail Achatina fulica is an agricultural pest whose biotechnological potential has been largely untested. Here, the composition of the microbial population within the crop of this invasive land snail, as well as key genes involved in various biochemical pathways, have been explored for the first time. In a high-throughput approach, 318 Mbp of 454-Titanium shotgun metagenomic sequencing data were obtained. The predominant bacterial phylum found was Proteobacteria, followed by Bacteroidetes and Firmicutes. Viruses, Fungi, and Archaea were present to lesser extents. The functional analysis reveals a variety of microbial genes that could assist the host in the degradation of recalcitrant lignocellulose, detoxification of xenobiotics, and synthesis of essential amino acids and vitamins, contributing to the adaptability and wide-ranging diet of this snail. More than 2,700 genes encoding glycoside hydrolase (GH) domains and carbohydrate-binding modules were detected. When we compared GH profiles, we found an abundance of sequences coding for oligosaccharide-degrading enzymes (36%), very similar to those from wallabies and giant pandas, as well as many novel cellulase and hemicellulase coding sequences, which points to this model as a remarkable potential source of enzymes for the biofuel industry. Furthermore, this work is a major step toward the understanding of the unique genetic profile of the land snail holobiont. PMID:23133637

Differential transcriptomic responses of Biomphalaria glabrata (Gastropoda, Mollusca) to bacteria and metazoan parasites, Schistosoma mansoni and Echinostoma paraensei (Digenea, Platyhelminthes)

PubMed Central

Adema, Coen M; Hanington, Patrick C.; Lun, Cheng-Man; Rosenberg, George H.; Aragon, Anthony D; Stout, Barbara A; Richard, Mara L. Lennard; Gross, Paul S.; Loker, Eric S

2009-01-01

A 70-mer oligonucleotide-based microarray (1152 features) that emphasizes stress and immune responses factors was constructed to study transcriptomic responses of the snail Biomphalaria glabrata to different immune challenges. In addition to sequences with relevant putative ID and Gene Ontology (GO) annotation, the array features non-immune factors and unknown B. glabrata ESTs for functional gene discovery. The transcription profiles of B. glabrata (3 biological replicates, each a pool of 5 snails) were recorded at 12 hours post wounding, exposure to Gram negative or Gram positive bacteria (Escherichia coli and Micrococcus luteus, respectively), or infection with compatible trematode parasites (S. mansoni or E. paraensei, 20 miracidia/snail), relative to controls, using universal reference RNA. The data were subjected to Significance Analysis for Microarrays (SAM), with a false positive rate (FPR) ≤10%. Wounding yielded a modest differential expression profile (27 up/21 down) with affected features mostly dissimilar from other treatments. Partially overlapping, yet distinct expression profiles were recorded from snails challenged with E. coli (83 up/20 down) or M. luteus (120 up/42 down), mostly showing up-regulation of defense and stress-related features. Significantly altered expression of selected immune features indicates that B. glabrata detects and responds differently to compatible trematodes. Echinostoma paraensei infection was associated mostly with down regulation of many (immune-) transcripts (42 up/68 down), whereas S. mansoni exposure yielded a preponderance of up-regulated features (140 up/23 down), with only few known immune genes affected. These observations may reflect the divergent strategies developed by trematodes during their evolution as specialized pathogens of snails to negate host defense responses. Clearly, the immune defenses of B. glabrata distinguish and respond differently to various immune challenges. PMID:19962194

Sarcocystis jamaicensis, n. sp. from red-tailed hawks (Buteo jamaicensis) definitive host and IFN-Gamma gene knockout mice as experimental intermediate host

USDA-ARS?s Scientific Manuscript database

Sarcocystis species have 2-host life cycles with the sexual cycle in the definitive hosts and an asexual cycle in the intermediate hosts. The common buzzard (Buteo buteo) is the definitive host for 2 species of Sarcocystis; Sarcocystis (Frenkelia) microti (forms macroscopic, lobulated sarcocysts) an...

Rapid identification and differentiation of Fasciola hepatica and Fasciola gigantica by a loop-mediated isothermal amplification (LAMP) assay.

PubMed

Ai, L; Li, C; Elsheikha, H M; Hong, S J; Chen, J X; Chen, S H; Li, X; Cai, X Q; Chen, M X; Zhu, X Q

2010-12-15

The present study developed and validated a species-specific loop-mediated isothermal amplification (LAMP) assay for the rapid detection and discrimination of Fasciola hepatica and Fasciola gigantica. The LAMP assay is inexpensive, easy to perform and shows rapid reaction, wherein the amplification can be obtained in 45 min under isothermal conditions of 61 °C or 62 °C by employing a set of four species-specific primer mixtures and results can be checked through naked-eye visualization. The optimal assay conditions with no cross-reaction with other closely related trematodes (Clonorchis sinensis, Opisthorchis viverrini, Orientobilharzia turkestanicum and Schistosoma japonicum) as well as within the two Fasciola species were established. The assay was validated by examining F. gigantica DNA in the intermediate host snails and in faecal samples. The results indicated that the LAMP assay is approximately 10(4) times more sensitive than the conventional specific PCR assays. These findings indicate that this Fasciola species-specific LAMP assay may have a potential clinical application for detection and differentiation of Fasciola species, especially in endemic countries. Copyright © 2010 Elsevier B.V. All rights reserved.

Sarcocystis strixi, n. sp. from barred owls (Strix varia) definitive hosts and gamma interferon gene knockout mice as experimental intermediate host

USDA-ARS?s Scientific Manuscript database

Sarcocystis species have 2-host life cycles with the sexual cycle in the definitive hosts and an asexual cycle in the intermediate hosts. Raptors are definitive hosts for several species of Sarcocystis but intestinal infection with Sarcocystis has not been reported from Barred owls (Strix varia). He...

Does interspecies hybridization affect the host specificity of parasites in cyprinid fish?

PubMed

Simková, Andrea; Dávidová, Martina; Papoušek, Ivo; Vetešník, Lukáš

2013-04-12

Host specificity varies among parasite species. Some parasites are strictly host-specific, others show a specificity for congeneric or non-congeneric phylogenetically related host species, whilst some others are non-specific (generalists). Two cyprinids, Cyprinus carpio and Carassius gibelio, plus their respective hybrids were investigated for metazoan parasites. The aim of this study was to analyze whether interspecies hybridization affects host specificity. The different degrees of host specificity within a phylogenetic framework were taken into consideration (i.e. strict specialist, intermediate specialist, and intermediate generalist). Fish were collected during harvesting the pond and identified using meristic traits and molecular markers. Metazoan parasite species were collected. Host specificity of parasites was determined using the following classification: strict specialist, intermediate specialist, intermediate generalist and generalist. Parasite species richness was compared between parental species and their hybrids. The effect of host species on abundance of parasites differing in host specificity was tested. Hybrids harbored more different parasite species but their total parasite abundance was lower in comparison with parental species. Interspecies hybridization affected the host specificity of ecto- and endoparasites. Parasite species exhibiting different degrees of host specificity for C. carpio and C. gibelio were also present in hybrids. The abundance of strict specialists of C. carpio was significantly higher in parental species than in hybrids. Intermediate generalists parasitizing C. carpio and C. gibelio as two phylogenetically closely related host species preferentially infected C. gibelio when compared to C. carpio, based on prevalence and maximum intensity of infection. Hybrids were less infected by intermediate generalists when compared to C. gibelio. This finding does not support strict co-adaptation between host and parasite genotypes resulting in narrow host specificity, and showed that hybrid genotypes are susceptible to parasites exhibiting host specificity. The immune mechanisms specific to parental species might represent potential mechanisms explaining the low abundance of parasites in C. gibelio x C. carpio hybrids.

Evolution of complex life cycles in trophically transmitted helminths. I. Host incorporation and trophic ascent.

PubMed

Parker, G A; Ball, M A; Chubb, J C

2015-02-01

Links between parasites and food webs are evolutionarily ancient but dynamic: life history theory provides insights into helminth complex life cycle origins. Most adult helminths benefit by sexual reproduction in vertebrates, often high up food chains, but direct infection is commonly constrained by a trophic vacuum between free-living propagules and definitive hosts. Intermediate hosts fill this vacuum, facilitating transmission to definitive hosts. The central question concerns why sexual reproduction, and sometimes even larval growth, is suppressed in intermediate hosts, favouring growth arrest at larval maturity in intermediate hosts and reproductive suppression until transmission to definitive hosts? Increased longevity and higher growth in definitive hosts can generate selection for larger parasite body size and higher fecundity at sexual maturity. Life cycle length is increased by two evolutionary mechanisms, upward and downward incorporation, allowing simple (one-host) cycles to become complex (multihost). In downward incorporation, an intermediate host is added below the definitive host: models suggest that downward incorporation probably evolves only after ecological or evolutionary perturbations create a trophic vacuum. In upward incorporation, a new definitive host is added above the original definitive host, which subsequently becomes an intermediate host, again maintained by the trophic vacuum: theory suggests that this is plausible even under constant ecological/evolutionary conditions. The final cycle is similar irrespective of its origin (upward or downward). Insights about host incorporation are best gained by linking comparative phylogenetic analyses (describing evolutionary history) with evolutionary models (examining selective forces). Ascent of host trophic levels and evolution of optimal host taxa ranges are discussed. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

The development of quick, robust, quantitative phenotypic assays for describing the host–nonhost landscape to stripe rust

PubMed Central

Dawson, Andrew M.; Bettgenhaeuser, Jan; Gardiner, Matthew; Green, Phon; Hernández-Pinzón, Inmaculada; Hubbard, Amelia; Moscou, Matthew J.

2015-01-01

Nonhost resistance is often conceptualized as a qualitative separation from host resistance. Classification into these two states is generally facile, as they fail to fully describe the range of states that exist in the transition from host to nonhost. This poses a problem when studying pathosystems that cannot be classified as either host or nonhost due to their intermediate status relative to these two extremes. In this study, we investigate the efficacy of the Poaceae-stripe rust (Puccinia striiformis Westend.) interaction for describing the host–nonhost landscape. First, using barley (Hordeum vulgare L.) and Brachypodium distachyon (L.) P. Beauv. We observed that macroscopic symptoms of chlorosis and leaf browning were associated with hyphal colonization by P. striiformis f. sp. tritici, respectively. This prompted us to adapt a protocol for visualizing fungal structures into a phenotypic assay that estimates the percent of leaf colonized. Use of this assay in intermediate host and intermediate nonhost systems found the frequency of infection decreases with evolutionary divergence from the host species. Similarly, we observed that the pathogen’s ability to complete its life cycle decreased faster than its ability to colonize leaf tissue, with no incidence of pustules observed in the intermediate nonhost system and significantly reduced pustule formation in the intermediate host system as compared to the host system, barley-P. striiformis f. sp. hordei. By leveraging the stripe rust pathosystem in conjunction with macroscopic and microscopic phenotypic assays, we now hope to dissect the genetic architecture of intermediate host and intermediate nonhost resistance using structured populations in barley and B. distachyon. PMID:26579142

Why do larval helminths avoid the gut of intermediate hosts?

PubMed

Parker, G A; Ball, M A; Chubb, J C

2009-10-07

In complex life cycles, larval helminths typically migrate from the gut to exploit the tissues of their intermediate hosts. Yet the definitive host's gut is overwhelmingly the most favoured site for adult helminths to release eggs. Vertebrate nematodes with one-host cycles commonly migrate to a site in the host away from the gut before returning to the gut for reproduction; those with complex cycles occupy sites exclusively in the intermediate host's tissues or body spaces, and may or may not show tissue migration before (typically) returning to the gut in the definitive host. We develop models to explain the patterns of exploitation of different host sites, and in particular why larval helminths avoid the intermediate host's gut, and adult helminths favour it. Our models include the survival costs of migration between sites, and maximise fitness (=expected lifetime number of eggs produced by a given helminth propagule) in seeking the optimal strategy (host gut versus host tissue exploitation) under different growth, mortality, transmission and reproductive rates in the gut and tissues (i.e. sites away from the gut). We consider the relative merits of the gut and tissues, and conclude that (i) growth rates are likely to be higher in the tissues, (ii) mortality rates possibly higher in the gut (despite the immunological inertness of the gut lumen), and (iii) that there are very high benefits to egg release in the gut. The models show that these growth and mortality relativities would account for the common life history pattern of avoidance of the intermediate host's gut because the tissues offer a higher growth rate/mortality rate ratio (discounted by the costs of migration), and make a number of testable predictions. Though nematode larvae in paratenic hosts usually migrate to the tissues, unlike larvae in intermediates, they sometimes remain in the gut, which is predicted since in paratenics mortality rate and migration costs alone determine the site to be exploited.

The social and economic context and determinants of schistosomiasis japonica.

PubMed

Huang, Yi-Xin; Manderson, Lenore

2005-01-01

A variety of biological and social factors govern schistosomiasis japonica in China. Social factors include those at a national and regional level, such as policies and patterns of development, which impact on local economic activities, and affect community, household and personal risk factors of infection. Drawing on research conducted in China, we illustrate how social structural and related factors influence individual risk and prevalence of infection. At a macro-level, political changes have occurred resulting in the shift from collective to family-based production, leading to clustering of infection in families. Industrialization and urbanization, and associated increased population mobility, have also influenced patterns of transmission and infection. Types of activities and local production patterns determine the exposure of individuals to schistosome-infested water sources. Fishermen have the most frequent water contact, aquatic workers the second and farmers the third; the relative risk of Schistosoma japonicum infection follows the same order. Among farmers, human infection is significantly related to agricultural production in rice fields infested with the intermediate host snail, and to rates of the infection in livestock. Risk of S. japonicum infection is also influenced by the domestic environment, including both the location of the house in relation to snail-colonized water sources, access to safe water, and improved sanitation. Household wealth and income determine family ability to provide and maintain safe water and sanitation, while determining or interacting with other variables. At an individual level, sex, age, educational level and ethnicity are all associated with different patterns of water use and water contact behaviour thereby affecting infection rates. Schistosomiasis impairs the growth and nutrition of children and the physical work capacity of adults, and so affects economic development. Given this, we note the importance of further research and social and contextual aspects of schistosomiasis infection in order to develop and sustain sound control strategies.

Species associations among larval helminths in an amphipod intermediate host.

PubMed

Dezfuli, B S; Giari, L; Poulin, R

2000-10-01

Larval helminths that share the same intermediate host may or may not also share the same definitive hosts. If one or more of these helminth species can manipulate the phenotype of the intermediate host, there can be great advantages or severe costs for other helminths resulting from co-occurring with a manipulator, depending on whether they have the same definitive host or not. Among 2372 specimens of the amphipod Echinogammarus stammeri collected from the river Brenta, northern Italy, there was a positive association between two acanthocephalan species with the same fish definitive hosts, the relatively common Pomphorhynchus laevis and the much less prevalent Acanthocephalus clavula. The number of cystacanths of P. laevis per infected amphipod, which ranged from one to five, did not influence the likelihood that the amphipod would also host A. clavula. A third acanthocephalan species, Polymorphus minutus,which matures in birds, showed no association with either of the two other species. These results show that associations among helminth species in intermediate hosts are not random, and are instead the product of selection favouring certain pathways of transmission.

Developmental stages of fish blood flukes, Cardicola forsteri and Cardicola opisthorchis (Trematoda: Aporocotylidae), in their polychaete intermediate hosts collected at Pacific bluefin tuna culture sites in Japan.

PubMed

Ogawa, Kazuo; Shirakashi, Sho; Tani, Kazuki; Shin, Sang Phil; Ishimaru, Katsuya; Honryo, Tomoki; Sugihara, Yukitaka; Uchida, Hiro'omi

2017-02-01

Farming of Pacific bluefin tuna (PBT), Thunnus orientalis, is a rapidly growing industry in Japan. Aporocotylid blood flukes of the genus Cardicola comprising C. orientalis, C. opisthorchis and C. forsteri are parasites of economic importance for PBT farming. Recently, terebellid polychaetes have been identified as the intermediate hosts for all these parasites. We collected infected polychaetes, Terebella sp., the intermediate host of C. opisthorchis, from ropes and floats attached to tuna cages in Tsushima, Nagasaki Prefecture, Japan. Also, Neoamphitrite vigintipes (formerly as Amphitrite sp. sensu Shirakashi et al., 2016), the intermediate host of C. forsteri, were collected from culture cages in Kushimoto, Wakayama Prefecture, Japan. The terebellid intermediate hosts harbored the sporocysts and cercariae in their body cavity. Developmental stages of these blood flukes were molecularly identified using species specific PCR primers. In this paper, we describe the cercaria and sporocyst stages of C. opisthorchis and C. forsteri and compare their morphological characteristics among three Cardicola blood flukes infecting PBT. We also discuss phylogenetic relations of the six genera of the terebellid intermediate hosts (Artacama, Lanassa, Longicarpus, Terebella, Nicolea and Neoamphitrite) of blood flukes infecting marine fishes, based on their morphological characters. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

An artificial perch to help Snail Kites handle an exotic Apple Snail

USGS Publications Warehouse

Pias, Kyle E.; Welch, Zach C.; Kitchens, Wiley M.

2012-01-01

In the United States, the Snail Kite (Rostrhamus sociabilis plumbeus) is a federally endangered species and restricted to the wetlands of south-central Florida where the current population numbers less than 1,500. The Snail Kite is an extreme dietary specialist, previously feeding almost exclusively on one species of snail, the Florida Apple Snail (Pomacea paludosa). Within the past decade, an exotic species of apple snail, the Island Apple Snail (Pomacea insularum), has become established on lakes in central Florida. Island Apple Snails are larger than the native Florida Apple Snails, and Snail Kites handle the exotic snails less efficiently. Juvenile Snail Kites, in particular, have lower daily energy balances while feeding on Island Apple Snails. An inexpensive, easy-to-construct platform was developed that would provide Snail Kites with a flat, stable surface on which to extract snails. The platform has the potential to reduce the difficulties Snail Kites experience when handling exotic snails, and may benefit the Snail Kite population as a whole. Initial observations indicate that Snail Kites use the platforms frequently, and snails extracted at the platforms are larger than snails extracted at other perches.

Evolution of trophic transmission in parasites: Why add intermediate hosts?

USGS Publications Warehouse

Choisy, Marc; Brown, Sam P.; Lafferty, Kevin D.; Thomas, Frédéric

2003-01-01

Although multihost complex life cycles (CLCs) are common in several distantly related groups of parasites, their evolution remains poorly understood. In this article, we argue that under particular circumstances, adding a second host to a single-host life cycle is likely to enhance transmission (i.e., reaching the target host). For instance, in several situations, the propagules of a parasite exploiting a predator species will achieve a higher host-finding success by encysting in a prey of the target predator than by other dispersal modes. In such a case, selection should favor the transition from a singleto a two-host life cycle that includes the prey species as an intermediate host. We use an optimality model to explore this idea, and we discuss it in relation to dispersal strategies known among free-living species, especially animal dispersal. The model found that selection favored a complex life cycle only if intermediate hosts were more abundant than definitive hosts. The selective value of a complex life cycle increased with predation rates by definitive hosts on intermediate hosts. In exploring trade-offs between transmission strategies, we found that more costly trade-offs made it more difficult to evolve a CLC while less costly trade-offs between traits could favor a mixed strategy.

Transmission rates of the bacterial endosymbiont, Neorickettsia risticii, during the asexual reproduction phase of its digenean host, Plagiorchis elegans, within naturally infected lymnaeid snails.

PubMed

Greiman, Stephen E; Tkach, Vasyl V; Vaughan, Jefferson A

2013-10-22

Neorickettsia are obligate intracellular bacterial endosymbionts of digenean parasites present in all lifestages of digeneans. Quantitative information on the transmission of neorickettsial endosymbionts throughout the complex life cycles of digeneans is lacking. This study quantified the transmission of Neorickettsia during the asexual reproductive phase of a digenean parasite, Plagiorchis elegans, developing within naturally parasitized lymnaeid pond snails. Lymnaea stagnalis snails were collected from 3 ponds in Nelson County, North Dakota and screened for the presence of digenean cercariae. Cercariae were identified to species by PCR and sequencing of the 28S rRNA gene. Neorickettsia infections were initially detected using nested PCR and sequencing of a partial 16S rRNA gene of pooled cercariae shed from each parasitized snail. Fifty to 100 single cercariae or sporocysts were isolated from each of six parasitized snails and tested for the presence of Neorickettsia using nested PCR to estimate the efficiency at which Neorickettsia were transmitted to cercariae during asexual development of the digenean. A total of 616 L. stagnalis were collected and 240 (39%) shed digenean cercariae. Of these, 18 (8%) were Neorickettsia-positive. Six Neorickettsia infections were selected to determine the transmission efficiency of Neorickettsia from mother to daughter sporocyst and from daughter sporocyst to cercaria. The prevalence of neorickettsiae in cercariae varied from 11 to 91%. The prevalence of neorickettsiae in sporocysts from one snail was 100%. Prevalence of Neorickettsia infection in cercariae of Plagiorchis elegans was variable and never reached 100%. Reasons for this are speculative, however, the low prevalence of Neorickettsia observed in some of our samples (11 to 52%) differs from the high prevalence of other, related bacterial endosymbionts, e.g. Wolbachia in Wolbachia-dependent filariid nematodes, where the prevalence among progeny is universally 100%. This suggests that, unlike the Wolbachia-filaria relationship, the Neorickettsia-digenean relationship is not obligatory mutualism. Our study represents the first quantitative estimate of the Neorickettsia transmission through the asexual phase of the digenean life cycle.

MOLECULAR SYSTEMATICS OF THE AVIAN SCHISTOSOME GENUS TRICHOBILHARZIA (TREMATODA: SCHISTOSOMATIDAE) IN NORTH AMERICA

PubMed Central

Brant, Sara V.; Loker, Eric S.

2010-01-01

Trichobilharzia is a genus of thread-like schistosomes with a cosmopolitan distribution in birds. Species of Trichobilharzia achieve notoriety as major etiological agents of cercarial dermatitis, or swimmer’s itch. There are 40 species described in the literature, for which the majority lacks molecular sequence information. To better understand the phylogenetic relationships, diversity, species boundaries, host use, and geographic distribution of this genus, we surveyed 378 birds and over 10,000 snails from North America. The phylogenetic analysis was based on nuclear 18S, 28S rDNA, internal transcribed spacer region and mitochondrial cytochrome oxidase I sequence data. Specimens were recovered that could be related to 6 of the 14 described species of Trichobilharzia from North America (T. physellae, T. querquedulae, T. szidati, T. stagnicolae, T. franki, and T. brantae). An additional 5 lineages were found that could not be related directly to previously described species. Trichobilharzia brantae, transmitted by Gyraulus parvus, grouped outside the clade containing the recognized species of Trichobilharzia. A subgroup of the Trichobilharzia clade designated Clade Q was comprised of closely related species whose adults and eggs are similar, yet the European species use lymnaeids whereas the North American species use physids as snail hosts. This molecular phylogeny provides a useful framework to: 1) facilitate identification of worms, including those involved in dermatitis outbreaks; 2) test hypotheses about the evolution, diversification, host-parasite interactions and character evolution of Trichobilharzia; and 3) guide future taxonomic revision of Trichobilharzia. PMID:20049999

Foodborne Intestinal Flukes in Southeast Asia

PubMed Central

Shin, Eun-Hee; Lee, Soon-Hyung; Rim, Han-Jong

2009-01-01

In Southeast Asia, a total of 59 species of foodborne intestinal flukes have been known to occur in humans. The largest group is the family Heterophyidae, which constitutes 22 species belonging to 9 genera (Centrocestus, Haplorchis, Heterophyes, Heterophyopsis, Metagonimus, Procerovum, Pygidiopsis, Stellantchasmus, and Stictodora). The next is the family Echinostomatidae, which includes 20 species in 8 genera (Artyfechinostomum, Acanthoparyphium, Echinochasmus, Echinoparyphium, Echinostoma, Episthmium, Euparyphium, and Hypoderaeum). The family Plagiorchiidae follows the next containing 5 species in 1 genus (Plagiorchis). The family Lecithodendriidae includes 3 species in 2 genera (Phaneropsolus and Prosthodendrium). In 9 other families, 1 species in 1 genus each is involved; Cathaemaciidae (Cathaemacia), Fasciolidae (Fasciolopsis), Gastrodiscidae (Gastrodiscoides), Gymnophallidae (Gymnophalloides), Microphallidae (Spelotrema), Neodiplostomidae (Neodiplostomum), Paramphistomatidae (Fischoederius), Psilostomidae (Psilorchis), and Strigeidae (Cotylurus). Various types of foods are sources of human infections. They include freshwater fish, brackish water fish, fresh water snails, brackish water snails (including the oyster), amphibians, terrestrial snakes, aquatic insects, and aquatic plants. The reservoir hosts include various species of mammals or birds.The host-parasite relationships have been studied in Metagonimus yokogawai, Echinostoma hortense, Fasciolopsis buski, Neodiplostomum seoulense, and Gymnophalloides seoi; however, the pathogenicity of each parasite species and host mucosal defense mechanisms are yet poorly understood. Clinical aspects of each parasite infection need more clarification. Differential diagnosis by fecal examination is difficult because of morphological similarity of eggs. Praziquantel is effective for most intestinal fluke infections. Continued efforts to understand epidemiological significance of intestinal fluke infections, with detection of further human cases, are required. PMID:19885337

Sarcocystis pantherophis, n. sp. from eastern rat snakes (Pantherophis alleghaniensis) definitive hosts and interferongamma gene knockout mice as experimental intermediate hosts

USDA-ARS?s Scientific Manuscript database

Here we report a new species, Sarcocystis pantherophisi with the Eastern rat snake (Pantherophis alleghaniensis) as natural definitive host and the interferon gamma gene knockout (KO) mouse as the experimental intermediate host. Sporocysts (n=15) from intestinal contents of the snake were 17.3 x 10....

Sarcocystis caninum and Sarcocystis svanai n. spp. (Apicomplexa: Sarcocystidae) associated with severe myositis and hepatitis in the domestic dog (Canis familiaris)

USDA-ARS?s Scientific Manuscript database

Sarcocystis species have a 2-host life cycle with carnivores as definitive hosts and herbivores as intermediate hosts. Occasionally dogs are definitive as well as intermediate hosts for Sarcocystis species. There are several reports of Sarcocystis sarcocysts in muscles of dogs but these species have...

Spatial distribution of Echinococcus multilocularis, Svalbard, Norway.

PubMed

Fuglei, Eva; Stien, Audun; Yoccoz, Nigel G; Ims, Rolf A; Eide, Nina E; Prestrud, Pål; Deplazes, Peter; Oksanen, Antti

2008-01-01

In Svalbard, Norway, the only intermediate host for Echinococcus multilocularis, the sibling vole, has restricted spatial distribution. A survey of feces from the main host, the arctic fox, showed that only the area occupied by the intermediate host is associated with increased risk for human infection.

Optoelectronic properties analysis of Ti-substituted GaP.

PubMed

Tablero, C

2005-11-08

A study using first principles of the electronic and optical properties of materials derived from a GaP host semiconductor where one Ti atom is substituted for one of the eight P atoms is presented. This material has a metallic intermediate band sandwiched between the valence and conduction bands of the host semiconductor for 0 < or = U < or = 8 eV where U is the Hubbard parameter. The potential of these materials is that when they are used as an absorber of photons in solar cells, the efficiency is increased significantly with respect to that of the host semiconductor. The results show that the main contribution to the intermediate band is the Ti atom and that this material can absorb photons of lower energy than that of the host semiconductor. The efficiency is increased with respect to that of the host semiconductor mainly because of the absorption from the intermediate to conduction band. As U increases, the contribution of the Ti-d orbitals to the intermediate band varies, increasing the d(z2) character at the bottom of the intermediate band.

Integrated multi-omic analyses in Biomphalaria-Schistosoma dialogue reveal the immunobiological significance of FREP-SmPoMuc interaction.

PubMed

Portet, Anaïs; Pinaud, Silvain; Tetreau, Guillaume; Galinier, Richard; Cosseau, Céline; Duval, David; Grunau, Christoph; Mitta, Guillaume; Gourbal, Benjamin

2017-10-01

The fresh water snail Biomphalaria glabrata is one of the vectors of the trematode pathogen Schistosoma mansoni, which is one of the agents responsible of human schistosomiasis. In this host-parasite interaction, co-evolutionary dynamic results into an infectivity mosaic known as compatibility polymorphism. Integrative approaches including large scale molecular approaches have been conducted in recent years to improve our understanding of the mechanisms underlying compatibility. This review presents the combination of integrated Multi-Omic approaches leading to the discovery of two repertoires of polymorphic and/or diversified interacting molecules: the parasite antigens S. mansoni polymorphic mucins (SmPoMucs) and the B. glabrata immune receptors fibrinogen-related proteins (FREPs). We argue that their interactions may be major components for defining the compatible/incompatible status of a specific snail/schistosome combination. Copyright © 2017 Elsevier Ltd. All rights reserved.

Salicylic acid, a plant defense hormone, is specifically secreted by a molluscan herbivore.

PubMed

Kästner, Julia; von Knorre, Dietrich; Himanshu, Himanshu; Erb, Matthias; Baldwin, Ian T; Meldau, Stefan

2014-01-01

Slugs and snails are important herbivores in many ecosystems. They differ from other herbivores by their characteristic mucus trail. As the mucus is secreted at the interface between the plants and the herbivores, its chemical composition may play an essential role in plant responses to slug and snail attack. Based on our current knowledge about host-manipulation strategies employed by pathogens and insects, we hypothesized that mollusks may excrete phytohormone-like substances into their mucus. We therefore screened locomotion mucus from thirteen molluscan herbivores for the presence of the plant defense hormones jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA). We found that the locomotion mucus of one slug, Deroceras reticulatum, contained significant amounts of SA, a plant hormone that is known to induce resistance to pathogens and to suppress plant immunity against herbivores. None of the other slugs and snails contained SA or any other hormone in their locomotion mucus. When the mucus of D. reticulatum was applied to wounded leaves of A. thaliana, the promotor of the SA-responsive gene pathogenesis related 1 (PR1) was activated, demonstrating the potential of the mucus to regulate plant defenses. We discuss the potential ecological, agricultural and medical implications of this finding.

Salicylic Acid, a Plant Defense Hormone, Is Specifically Secreted by a Molluscan Herbivore

PubMed Central

Kästner, Julia; von Knorre, Dietrich; Himanshu, Himanshu; Erb, Matthias; Baldwin, Ian T.; Meldau, Stefan

2014-01-01

Slugs and snails are important herbivores in many ecosystems. They differ from other herbivores by their characteristic mucus trail. As the mucus is secreted at the interface between the plants and the herbivores, its chemical composition may play an essential role in plant responses to slug and snail attack. Based on our current knowledge about host-manipulation strategies employed by pathogens and insects, we hypothesized that mollusks may excrete phytohormone-like substances into their mucus. We therefore screened locomotion mucus from thirteen molluscan herbivores for the presence of the plant defense hormones jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA). We found that the locomotion mucus of one slug, Deroceras reticulatum, contained significant amounts of SA, a plant hormone that is known to induce resistance to pathogens and to suppress plant immunity against herbivores. None of the other slugs and snails contained SA or any other hormone in their locomotion mucus. When the mucus of D. reticulatum was applied to wounded leaves of A. thaliana, the promotor of the SA-responsive gene pathogenesis related 1 (PR1) was activated, demonstrating the potential of the mucus to regulate plant defenses. We discuss the potential ecological, agricultural and medical implications of this finding. PMID:24466122

Application of geo-spatial technology in schistosomiasis modelling in Africa: a review.

PubMed

Manyangadze, Tawanda; Chimbari, Moses John; Gebreslasie, Michael; Mukaratirwa, Samson

2015-11-04

Schistosomiasis continues to impact socio-economic development negatively in sub-Saharan Africa. The advent of spatial technologies, including geographic information systems (GIS), Earth observation (EO) and global positioning systems (GPS) assist modelling efforts. However, there is increasing concern regarding the accuracy and precision of the current spatial models. This paper reviews the literature regarding the progress and challenges in the development and utilization of spatial technology with special reference to predictive models for schistosomiasis in Africa. Peer-reviewed papers identified through a PubMed search using the following keywords: geo-spatial analysis OR remote sensing OR modelling OR earth observation OR geographic information systems OR prediction OR mapping AND schistosomiasis AND Africa were used. Statistical uncertainty, low spatial and temporal resolution satellite data and poor validation were identified as some of the factors that compromise the precision and accuracy of the existing predictive models. The need for high spatial resolution of remote sensing data in conjunction with ancillary data viz. ground-measured climatic and environmental information, local presence/absence intermediate host snail surveys as well as prevalence and intensity of human infection for model calibration and validation are discussed. The importance of a multidisciplinary approach in developing robust, spatial data capturing, modelling techniques and products applicable in epidemiology is highlighted.

Necropsy findings in 62 opportunistically collected free-ranging moose (Alces alces) from Minnesota, USA (2003-13).

PubMed

Wünschmann, Arno; Armien, Anibal G; Butler, Erika; Schrage, Mike; Stromberg, Bert; Bender, Jeff B; Firshman, Anna M; Carstensen, Michelle

2015-01-01

The Minnesota, US moose population has declined dramatically since the 1990s. All 54 carcasses of moose that died of unknown cause or were euthanized by gun shot by tribal or Department of Natural Resources personnel because of perceived signs of illness between 2003 and 2013 and eight carcasses of moose that died from vehicular accidents between 2009 and 2013 were submitted to the Minnesota Veterinary Diagnostic Laboratory and included in our study. The majority of the animals were underweight or cachectic (n = 53; 85%). Neural migration presumably by Parelaphostrongylus tenuis was a common finding (n = 28; 45%). Moderate to marked Dermacentor albipictus ("winter tick") ectoparasitism with widespread alopecia was the cause or a contributing cause of death in 14 (23%) cases in which grossly apparent anemia was associated with exhaustion of hepatic iron stores. Hepatic lesions associated with Fascioloides magna were common (n = 37; 60%) but were unlikely to be the cause of death. Environmental factors favoring winter tick survival, habitat expansion of white-tailed deer (Odocoileus virginianus), and the survival of terrestrial and aquatic snails (serving as intermediate hosts for P. tenuis and F. magna), might contribute to the seemingly severe parasitic burden in Minnesota's moose population.

Fatal trematodiasis in research turtles.

PubMed

Johnson, C A; Griffith, J W; Tenorio, P; Hytrek, S; Lang, C M

1998-08-01

During a 5-year period, 16 freshwater turtles (Trachemys scripta elegans and Chrysemys picta) that were purchased for research purposes died spontaneously. Clinical signs of disease included lethargy, constant swimming, swimming sideways, hemiplegia, and ulcerative lesions on the carapace. At necropsy, subcutaneous edema, hepatic necrosis, pancreatic necrosis, splenic necrosis, and intestinal parasites were identified. Histologically, trematode eggs were seen within the liver, brain, spleen, kidney, myocardium, lung, pancreas, testes, and bladder, and were associated with granulomatous reactions. The size and distribution of the eggs were consistent with Spirorchis sp. infection, although adults could not be found to confirm the species. Spirorchid flukes are 1 to 2 mm long and inhabit the heart and blood vessels where they produce eggs. Spirorchis parvus are capable of invading various tissues, including pancreas and the central nervous system. The pathogenicity of the flukes seems to be related to widespread deposition of the eggs, which may block small blood vessels within the intestines, causing necrosis and bacteremia. Antemortem diagnosis is made by direct examination of fecal smears for eggs. Postmortem diagnosis is accomplished by examination of tissues for adult parasites and microgranulomas associated with the fluke eggs. The parasite requires a snail intermediate host to complete its life cycle. Intramuscular or oral administration of praziquantel is reported to be an effective treatment.

The epidemiology and control of urinary schistosomiasis and soil-transmitted helminthiasis in schoolchildren on Unguja Island, Zanzibar.

PubMed

Stothard, J Russell; French, Michael D; Khamis, I Simba; Basáñez, María-Gloria; Rollinson, David

2009-10-01

As part of a 4-year control programme beginning in 2003 and entitled Piga Vita Kichocho, around 140,000 school-aged children on Unguja Island, Zanzibar were treated annually with a combination of praziquantel and albendazole. To provide information on the impact of this intervention, a subset of children, originating from 24 sentinel schools, were monitored in 2004, 2005 and 2006 using both parasitological and behavioural questionnaire methods. Overall, prevalence of urinary schistosomiasis fell by 52%, intensity by 55% and gross haematuria by 82%. There was a positive and statistically significant correlation between areas of elevated disease prevalence and areas of predicted high transmission based upon local occurrence of the permissive intermediate snail host. In areas of low transmission, urinary schistosomiasis was greatly reduced, but, by contrast, other intervention strategies are needed to complement and synergise with chemotherapy in high transmission areas. Whereas significant reductions were documented in the prevalence of both Trichuris trichiura and hookworm, prevalence of Ascaris lumbricoides significantly increased over the monitoring period. Through a detailed analysis of named child records, evidence of predisposition to helminth (re)infection and individual bias towards polyparasitism was detected, highlighting the often overlapping distribution of these parasites within the school-aged child.

Spatial heterogeneity in parasite infections at different spatial scales in an intertidal bivalve.

PubMed

Thieltges, David W; Reise, Karsten

2007-01-01

Spatial heterogeneities in the abundance of free-living organisms as well as in infection levels of their parasites are a common phenomenon, but knowledge on parasitism in invertebrate intermediate hosts in this respect is scarce. We investigated the spatial pattern of four dominant trematode species which utilize a common intertidal bivalve, the cockle Cerastoderma edule, as second intermediate host in their life cycles. Sampling of cockles from the same cohort at 15 sites in the northern Wadden Sea (North Sea) over a distance of 50 km revealed a conspicuous spatial heterogeneity in infection levels in all four species over the total sample as well as among and within sampling sites. Whereas multiple regression analyses indicated the density of first intermediate upstream hosts to be the strongest determinant of infection levels in cockles, the situation within sites was more complex with no single strong predictor variable. However, host size was positively and host density negatively correlated with infection levels and there was an indication of differential susceptibility of cockle hosts. Small-scale differences in physical properties of the habitat in the form of residual water at low tide resulted in increased infection levels of cockles which we experimentally transferred into pools. A complex interplay of these factors may be responsible for within-site heterogeneities. At larger spatial scales, these factors may be overridden by the strong effect of upstream hosts. In contrast to first intermediate trematode hosts, there was no indication for inter-specific interactions. In other terms, the recruitment of trematodes in second intermediate hosts seems to be largely controlled by pre-settlement processes both among and within host populations.

Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size.

PubMed

Rodríguez, Sara M; Valdivia, Nelson

2017-01-01

Parasites are essential components of natural communities, but the factors that generate skewed distributions of parasite occurrences and abundances across host populations are not well understood. Here, we analyse at a seascape scale the spatiotemporal relationships of parasite exposure and host body-size with the proportion of infected hosts (i.e., prevalence) and aggregation of parasite burden across ca. 150 km of the coast and over 22 months. We predicted that the effects of parasite exposure on prevalence and aggregation are dependent on host body-sizes. We used an indirect host-parasite interaction in which migratory seagulls, sandy-shore molecrabs, and an acanthocephalan worm constitute the definitive hosts, intermediate hosts, and endoparasite, respectively. In such complex systems, increments in the abundance of definitive hosts imply increments in intermediate hosts' exposure to the parasite's dispersive stages. Linear mixed-effects models showed a significant, albeit highly variable, positive relationship between seagull density and prevalence. This relationship was stronger for small (cephalothorax length >15 mm) than large molecrabs (<15 mm). Independently of seagull density, large molecrabs carried significantly more parasites than small molecrabs. The analysis of the variance-to-mean ratio of per capita parasite burden showed no relationship between seagull density and mean parasite aggregation across host populations. However, the amount of unexplained variability in aggregation was strikingly higher in larger than smaller intermediate hosts. This unexplained variability was driven by a decrease in the mean-variance scaling in heavily infected large molecrabs. These results show complex interdependencies between extrinsic and intrinsic population attributes on the structure of host-parasite interactions. We suggest that parasite accumulation-a characteristic of indirect host-parasite interactions-and subsequent increasing mortality rates over ontogeny underpin size-dependent host-parasite dynamics.

Abandoning the ship: spontaneous mass exodus of Clinostomum complanatum (Rudolphi, 1814) progenetic metecercariae from the dying intermediate host Trichogaster fasciatus (Bloch & Schneider, 1801).

PubMed

Rizvi, Asim; Alam, Md Maroof; Parveen, Saltanat; Saleemuddin, M; Abidi, S M A

2012-04-01

The dramatic and spontaneous exodus of live Clinostomum complanatum progenetic metacercaria from the gill slits of the dying intermediate host, Trichogaster fasciatus is reported. Basic water parameter tests for dissolved oxygen, pH and temperature revealed slightly lower level of dissolved oxygen in tank water used for water change. To the best of our knowledge, it is the first report of a digenean metacercariae, en mass leaving their intermediate host, upon its death in search of an alternative host to support their survival and help in continuing their life cycle.

Intestinal parasites of the Arctic fox in relation to the abundance and distribution of intermediate hosts.

PubMed

Stien, A; Voutilainen, L; Haukisalmi, V; Fuglei, E; Mørk, T; Yoccoz, N G; Ims, R A; Henttonen, H

2010-01-01

The intestinal parasite community of Arctic foxes (Vulpes lagopus) on the Svalbard archipelago in the High Arctic was investigated in relation to the abundance and distribution of intermediate hosts. Five species of cestodes (Echinococcus multilocularis, Taenia crassiceps, Taenia polyacantha, Taenia krabbei and Diphyllobothrium sp.), ascaridoid nematodes and one unidentified acanthocephalan species were found. The cestodes E. multilocularis, T. crassiceps and T. polyacantha all showed a decreasing prevalence in the fox population with increasing distance from their spatially restricted intermediate host population of sibling voles (Microtus levis). In addition, the prevalence of E. multilocularis in a sample from the vole population was directly related to the local vole abundance. The cestode T. krabbei uses reindeer as intermediate host, and its prevalence in female foxes was positively related to the density of reindeer (Rangifer tarandus platyrhyncus). Finally, the prevalence of the ascaridoid nematodes also decreased with increasing distance from the vole population, a finding that is consistent with the idea that voles are involved in transmission, most likely as paratenic hosts. The prevalence of the remaining species (Diphyllobothrium sp. and an unidentified acanthocephalan) was very low. We conclude that the distribution and abundance of intermediate host structure the gastrointestinal parasite community of the Arctic fox on the Svalbard archipelago.

Intermediate hosts of the trematode Collyriclum faba (Plagiochiida: Collyriclidae) identified by an integrated morphological and genetic approach.

PubMed

Heneberg, Petr; Faltýnková, Anna; Bizos, Jiří; Malá, Milena; Žiak, Juraj; Literák, Ivan

2015-02-08

The cutaneous monostome trematode Collyriclum faba (Bremser in Schmalz, 1831) is a bird parasite with a hitherto unknown life cycle and highly focal occurrence across the Holarctic and Neotropic ecozones. Representative specimens of benthic organisms were sampled at multiple sites and dates within the known foci of C. faba occurrence in Slovakia. A combined approach involving detailed morphological examination and sequencing of two independent DNA loci was used for their analysis. We elucidated the complete life cycle of C. faba, which we determined to include the aquatic gastropod mollusk Bythinella austriaca (Frauenfeld, 1857) as the first intermediate host, the mayflies of the family Heptageniidae, Ecdyonurus venosus (Fabricius, 1775) and Rhithrogena picteti Sowa, 1971 x iridina (Kolenati, 1839), as the second intermediate hosts, and birds (primarily but not exclusively passeriform birds) as the definitive hosts. Bythinella austriaca occurs focally in the springs of tributaries of the Danube in the Alpine-Carpathian region. The restricted distribution of B. austriaca explains the highly focal distribution of C. faba noticed previously in spite of the broad distribution of its second intermediate and definitive host species. Utilization of both larval and adult Ephemeroptera spp. as the second intermediate hosts explains the known spectrum of the definitive host species, with the highest prevalence in species feeding on larvae of Ephemeroptera, such as Cinclus cinclus (Linnaeus, 1758) and Motacilla cinerea Tunstall, 1771, or adults of Ephemeroptera, such as Sylvia atricapilla (Linnaeus, 1758) and Regulus regulus (Linnaeus, 1758). In this study, we also determine the prevalence and DNA sequences of other immature trematode specimens found in the examined benthic organisms (particularly the families Microphallidae, Troglotrematidae and Nanophyetidae and Euryhelmis zelleri Grabda-Kazubska, 1980, Heterophyidae), and describe cercariae of C. faba. We determined the full life cycle of the Central European populations of C. faba. We speculate that other species of Bythinella and the closely related genus Amnicola may serve as first intermediate hosts in other parts of the distribution range of C. faba. Similarly, other Ephemeroptera of the family Heptageniidae may serve as the second intermediate hosts of C. faba in the Americas.

Mancae of the parasitic cymothoid isopod, Anilocra apogonae: early life history, host-specificity, and effect on growth and survival of preferred young cardinal fishes

NASA Astrophysics Data System (ADS)

Fogelman, R. M.; Grutter, A. S.

2008-09-01

Juvenile parasitic cymothoid isopods (mancae) can injure or kill fishes, yet few studies have investigated their biology. While the definitive host of the adult cymothoids is usually a single host from a particular fish species, mancae may use so-called optional intermediate hosts before settling on the definitive host. Little, however, is known about these early interactions. The cymothoid isopod, Anilocra apogonae, infests the definitive host, Cheilodipterus quinquelineatus. This study examined their host preference among potential optional intermediate hosts. Their effect on the growth and mortality of the young of three apogonid fishes, including the definitive host, was investigated. The number of mancae produced per brood was positively correlated with female length. When given a choice of intermediate hosts, significantly more mancae attached to Apogon trimaculatus (Apogonidae) than to Apogon nigrofasciatus. When presented with Ap. trimaculatus and Pomacentrus amboinensis (Pomacentridae), mancae only attached to Ap. trimaculatus suggesting that mancae may show a taxonomic affiliation with preferred hosts. Mancae fed on all three apogonid species, with C. quinquelineatus being fed on earlier than Ap. trimaculatus and Ap. nigrofasciatus. Mancae feeding frequency, adjusted for fish survival, was lowest on C. quinquelineatus and highest on Ap. trimaculatus. Infested apogonids had reduced growth and increased mortality compared with uninfested fish. A. apogonae mancae can use several species of young apogonid fishes as optional intermediate hosts. Via reduced growth and increased mortality, mancae have the potential to negatively influence definitive host populations and also other young species of apogonid fishes.

Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size

PubMed Central

2017-01-01

Background Parasites are essential components of natural communities, but the factors that generate skewed distributions of parasite occurrences and abundances across host populations are not well understood. Methods Here, we analyse at a seascape scale the spatiotemporal relationships of parasite exposure and host body-size with the proportion of infected hosts (i.e., prevalence) and aggregation of parasite burden across ca. 150 km of the coast and over 22 months. We predicted that the effects of parasite exposure on prevalence and aggregation are dependent on host body-sizes. We used an indirect host-parasite interaction in which migratory seagulls, sandy-shore molecrabs, and an acanthocephalan worm constitute the definitive hosts, intermediate hosts, and endoparasite, respectively. In such complex systems, increments in the abundance of definitive hosts imply increments in intermediate hosts’ exposure to the parasite’s dispersive stages. Results Linear mixed-effects models showed a significant, albeit highly variable, positive relationship between seagull density and prevalence. This relationship was stronger for small (cephalothorax length >15 mm) than large molecrabs (<15 mm). Independently of seagull density, large molecrabs carried significantly more parasites than small molecrabs. The analysis of the variance-to-mean ratio of per capita parasite burden showed no relationship between seagull density and mean parasite aggregation across host populations. However, the amount of unexplained variability in aggregation was strikingly higher in larger than smaller intermediate hosts. This unexplained variability was driven by a decrease in the mean-variance scaling in heavily infected large molecrabs. Conclusions These results show complex interdependencies between extrinsic and intrinsic population attributes on the structure of host-parasite interactions. We suggest that parasite accumulation—a characteristic of indirect host-parasite interactions—and subsequent increasing mortality rates over ontogeny underpin size-dependent host-parasite dynamics. PMID:28828270

[Analysis of trend of Oncomelania snail status in Yangtze River valley of Anhui Province, 1998-2009].

PubMed

He, Jia-Chang; Wang, Jia-Sheng; Lu, Jin-You; Li, Ting-Ting; Gao, Feng-Hu; Zhou, Ping; Zhu, Chuan-Ming; He, Long-Zhu; Yu, Bei-Bei; Zhang, Shi-Qing

2011-04-01

To understand the trend of Oncomelania hupensis snail distribution in Yangtze River valley of Anhui Province so as to provide an evidence for making out schistosomiasis prevention and control strategies in the future. The snail data from 1998 to 2009 of the Yangtze River valley in Anhui Province were collected including the snail area, newly occurred and re-occurred snail areas, densities of snails and infected snails, etc., and the trend and influence factors were analyzed. With several fluctuations, the snail area showed a trend of declining in general after the devastating summer flooding in 1998. From 1998 to 2009, 3 peaks of newly occurred snail areas appeared in 1998, 2004 and 2006 and 2 peaks of reoccurred snail areas appeared in 1998 and 2004. The densities of living snails and infected snails were more severe in banks of the Yangtze River than in islets of the Yangtze River. During 12 years, 1 peak of living snail density appeared in 2003, and 3 peaks of infected snail density appeared in 1999, 2003-2004 and 2006 in the islets of the Yangtze River. The densities of living snails and infected snails in banks of the Yangtze both appeared 1 peak in 1998. The distribution of snails in the Yangtze River valley is related to nature, society and financial circumstances, and it is hard to completely perform the snail control in a short-term. Therefore, at the same time of strengthening snail control, we should also strengthen infectious source control.

Parasites, info-disruption, and the ecology of fear.

PubMed

Rohr, Jason R; Swan, Autumn; Raffel, Thomas R; Hudson, Peter J

2009-03-01

There is growing interest in the ecological consequences of fear, as evidenced by the numerous studies on the nonconsumptive, trait-mediated effects of predators. Parasitism, however, has yet to be fully integrated into research on the ecology of fear, despite it having direct negative and often lethal effects on hosts and being the most common life history strategy on the planet. This might at least be partly due to the traditional, but untested, assumption that anti-parasite responses are weak relative to anti-predator responses. To test this hypothesis, we quantified the activity and location responses of Bufo americanus tadpoles to one of six chemical cues: water; cercariae of Echinostoma trivolvis, a trematode which infects and can kill amphibians; a snail releasing E. trivolvis cercariae; an uninfected snail; food; or conspecific alarm chemicals signaling predation. There is also literature encouraging research on the context dependency and pollution-induced disruption of fear responses. Consequently, before quantifying responses to the chemical cues, half of the B. americanus were exposed to the herbicide atrazine (201 microg/l for 4 days), a reported inhibitor of fear responses in fish. Tadpoles were attracted to food, were indifferent to an uninfected snail, avoided alarm chemicals, and exhibited avoidance and elevated activity in response to a snail shedding cercariae and cercariae alone. Atrazine had no detectable effects on B. americanus' responses to the tested cues despite the use of a higher concentration and longer exposure duration than has been repeatedly shown to inhibit chemical cue detection in fish. The magnitude of anti-parasite and anti-predator responses were qualitatively similar, suggesting that the fear of disease and its ecological consequences could be comparable to that of predation. Consequently, we call for a greater integration of parasites into research on the ecology of fear and trait-mediated indirect effects.

Analysis of snail genes in the crustacean Parhyale hawaiensis: insight into snail gene family evolution.

PubMed

Hannibal, Roberta L; Price, Alivia L; Parchem, Ronald J; Patel, Nipam H

2012-05-01

The transcriptional repressor snail was first discovered in Drosophila melanogaster, where it initially plays a role in gastrulation and mesoderm formation, and later plays a role in neurogenesis. Among arthropods, this role of snail appears to be conserved in the insects Tribolium and Anopheles gambiae, but not in the chelicerates Cupiennius salei and Achaearanea tepidariorum, the myriapod Glomeris marginata, or the Branchiopod crustacean Daphnia magna. These data imply that within arthropoda, snail acquired its role in gastrulation and mesoderm formation in the insect lineage. However, crustaceans are a diverse group with several major taxa, making analysis of more crustaceans necessary to potentially understand the ancestral role of snail in Pancrustacea (crustaceans + insects) and thus in the ancestor of insects as well. To address these questions, we examined the snail family in the Malacostracan crustacean Parhyale hawaiensis. We found three snail homologs, Ph-snail1, Ph-snail2 and Ph-snail3, and one scratch homolog, Ph-scratch. Parhyale snail genes are expressed after gastrulation, during germband formation and elongation. Ph-snail1, Ph-snail2, and Ph-snail3 are expressed in distinct patterns in the neuroectoderm. Ph-snail1 is the only Parhyale snail gene expressed in the mesoderm, where its expression cycles in the mesodermal stem cells, called mesoteloblasts. The mesoteloblasts go through a series of cycles, where each cycle is composed of a migration phase and a division phase. Ph-snail1 is expressed during the migration phase, but not during the division phase. We found that as each mesoteloblast division produces one segment's worth of mesoderm, Ph-snail1 expression is linked to both the cell cycle and the segmental production of mesoderm.

Reproductive Ecology of the Giant African Snail in South Florida: Implications for Eradication Programs.

PubMed

Roda, Amy; Nachman, Gösta; Weihman, Scott; Yong Cong, Mary; Zimmerman, Fredrick

2016-01-01

Giant African snail (Achatina fulica (Bowdich, 1822)), an important invasive snail, was recently found in South Florida, USA. An extensive eradication effort was initiated consisting of pesticide applications, debris removal and hand collections. We studied the reproduction capacity and population dynamics of snails collected from 22 populations for two years to help evaluate the likely success of the eradication program. A total of 23,890 snails, ranging from 25-131 mm, were measured, dissected and the number of eggs in each snail counted. Gravid snails ranged from 48-128 mm. Only 5% of snails had eggs, which were found year round. As the snails increased in size, they were more likely to include reproducing individuals. However, the percentage of gravid snails peaked when snails were approximately 90 mm. Although more prevalent, small (<65 mm) adults contributed fewer eggs to the population than the larger snails. We evaluated the effect of control measures on six populations having >1000 adult snails and used data from the two largest populations to investigate how environmental factors (temperature, humidity, and rainfall) interacted with population dynamics and control measures. More snails were collected in weeks with high humidity and more gravid snails were collected when the temperature was higher. The addition of metaldehyde pesticides had the greatest impact on population dynamics by reducing snail numbers. In populations with fewer snails, their numbers were already declining before the use of metaldehyde, although the new treatment accelerated the process. As a consequence of the eradication program, egg-producing snails were no longer collected from most populations by the end of the study. The aggressive and persistent control efforts apparently lead to reduced populations of egg producing snails, eventually resulting in local extinctions of this important pest.

Reproductive Ecology of the Giant African Snail in South Florida: Implications for Eradication Programs

PubMed Central

2016-01-01

Giant African snail (Achatina fulica (Bowdich, 1822)), an important invasive snail, was recently found in South Florida, USA. An extensive eradication effort was initiated consisting of pesticide applications, debris removal and hand collections. We studied the reproduction capacity and population dynamics of snails collected from 22 populations for two years to help evaluate the likely success of the eradication program. A total of 23,890 snails, ranging from 25–131 mm, were measured, dissected and the number of eggs in each snail counted. Gravid snails ranged from 48–128 mm. Only 5% of snails had eggs, which were found year round. As the snails increased in size, they were more likely to include reproducing individuals. However, the percentage of gravid snails peaked when snails were approximately 90 mm. Although more prevalent, small (<65 mm) adults contributed fewer eggs to the population than the larger snails. We evaluated the effect of control measures on six populations having >1000 adult snails and used data from the two largest populations to investigate how environmental factors (temperature, humidity, and rainfall) interacted with population dynamics and control measures. More snails were collected in weeks with high humidity and more gravid snails were collected when the temperature was higher. The addition of metaldehyde pesticides had the greatest impact on population dynamics by reducing snail numbers. In populations with fewer snails, their numbers were already declining before the use of metaldehyde, although the new treatment accelerated the process. As a consequence of the eradication program, egg-producing snails were no longer collected from most populations by the end of the study. The aggressive and persistent control efforts apparently lead to reduced populations of egg producing snails, eventually resulting in local extinctions of this important pest. PMID:27861504

Host sharing and host manipulation by larval helminths in shore crabs: cooperation or conflict?

PubMed

Poulin, Robert; Nichol, Katherine; Latham, A David M

2003-04-01

Larval helminths of different species that share the same intermediate host and are transmitted by predation to the same definitive host may cooperate in their attempts to manipulate the behaviour of the intermediate host, while at the same time having conflicts of interests over the use of host resources. A few studies have indicated that intermediate hosts harbouring larval helminths have altered concentrations of neurotransmitters in their nervous system, and thus measuring levels of neurotransmitters in host brains could serve to assess the respective and combined effect of different helminth species on host behaviour. Here, we investigate potential cooperation and conflict among three helminths in two species of crab intermediate hosts. The acanthocephalan Profilicollis spp., the trematode Maritrema sp. and an acuariid nematode, all use Macrophthalmus hirtipes (Ocypodidae) as intermediate host, whereas Profilicollis and Maritrema also use Hemigrapsus crenulatus (Grapsidae). All three helminths mature inside gulls or other shore birds. There was a significant decrease in the mean volume of Profilicollis cystacanths as the intensity of infection by this parasite increased in H. crenulatus, the only host in which this was investigated; however, there was no measurable effect of other helminth species on the size of acanthocephalans, suggesting no interspecific conflict over resource use within crabs. There was, in contrast, evidence of a positive interspecific association between the two most common helminth species: numbers of Profilicollis and Maritrema were positively correlated among crabs, independently of crab size, in M. hirtipes but not H. crenulatus. More importantly, we found that the total number of larval helminths per crab correlated significantly, and negatively, with concentrations of serotonin in crab brains, again only in M. hirtipes; numbers of each parasite species separately did not covary in either crab species with serotonin or dopamine, the other neurotransmitter investigated in this study. The relationship with serotonin appears due mainly to numbers of Profilicollis and Maritrema and not to nematodes. This is the first demonstration of a potentially synergistic manipulation of host behaviour by different helminth species, one that appears host-specific; our results also point toward the neurobiological mechanism underlying this phenomenon.

Discovery-based studies of schistosome diversity stimulate new hypotheses about parasite biology

PubMed Central

Brant, Sara V.; Loker, Eric S.

2013-01-01

This review provides an update of ongoing efforts to expand our understanding of the diversity inherent within the Schistosomatidae, the parasites responsible for causing schistosomiasis and cercarial dermatitis. By revealing more of the species present, particularly among under-studied avian schistosomes, we gain increased understanding of patterns of schistosome diversification, and their abilities to colonize new hosts and habitats. Schistosomes reveal a surprising ability to switch into new snail and vertebrate host species, into new intra-host habitats, and may adopt novel body forms in the process. Often these changes are not associated with deep splits or long branches in their phylogeny, suggesting they are of relatively recent origin. Several hypotheses prompted by the new observations are discussed, helping to focus thinking on processes influencing not only schistosome diversification, but also their pathogenicity and abundance. PMID:23849836

North American paragonimiasis (Caused by Paragonimus kellicotti) in the context of global paragonimiasis.

PubMed

Procop, Gary W

2009-07-01

Paragonimus species are highly evolved parasites with a complex life cycle that involves at least three different hosts, i.e., snails, crustaceans, and mammals. The adult forms of Paragonimus species reside and mate in the lungs of a variety of permissive mammalian hosts, including humans. Although human paragonimiasis is uncommonly encountered in North America, both autochthonous and imported disease may be encountered. Paragonimus kellicotti, the species endemic to North America, is a well-known pathogen in wild and domestic animals. Five patients with North American paragonimiasis have been reported in the recent medical literature. The biologic, clinical, radiologic, and laboratory features of paragonimiasis are reviewed, with emphasis on North American paragonimiasis whenever possible.

Classification and prediction of river network ephemerality and its relevance for waterborne disease epidemiology

NASA Astrophysics Data System (ADS)

Perez-Saez, Javier; Mande, Theophile; Larsen, Joshua; Ceperley, Natalie; Rinaldo, Andrea

2017-12-01

The transmission of waterborne diseases hinges on the interactions between hydrology and ecology of hosts, vectors and parasites, with the long-term absence of water constituting a strict lower bound. However, the link between spatio-temporal patterns of hydrological ephemerality and waterborne disease transmission is poorly understood and difficult to account for. The use of limited biophysical and hydroclimate information from otherwise data scarce regions is therefore needed to characterize, classify, and predict river network ephemerality in a spatially explicit framework. Here, we develop a novel large-scale ephemerality classification and prediction methodology based on monthly discharge data, water and energy availability, and remote-sensing measures of vegetation, that is relevant to epidemiology, and maintains a mechanistic link to catchment hydrologic processes. Specifically, with reference to the context of Burkina Faso in sub-Saharan Africa, we extract a relevant set of catchment covariates that include the aridity index, annual runoff estimation using the Budyko framework, and hysteretical relations between precipitation and vegetation. Five ephemerality classes, from permanent to strongly ephemeral, are defined from the duration of 0-flow periods that also accounts for the sensitivity of river discharge to the long-lasting drought of the 70's-80's in West Africa. Using such classes, a gradient-boosted tree-based prediction yielded three distinct geographic regions of ephemerality. Importantly, we observe a strong epidemiological association between our predictions of hydrologic ephemerality and the known spatial patterns of schistosomiasis, an endemic parasitic waterborne disease in which infection occurs with human-water contact, and requires aquatic snails as an intermediate host. The general nature of our approach and its relevance for predicting the hydrologic controls on schistosomiasis occurrence provides a pathway for the explicit inclusion of hydrologic drivers within epidemiological models of waterborne disease transmission.

Sarcocystis cymruensis: Discovery in Western hemisphere in the Brown rat (Rattus norvegicus) from Grenada, West Indies: Redescription, molecular characterization, transmission to IFN-gamma gene knockout mice via sporocysts

USDA-ARS?s Scientific Manuscript database

Rodents are intermediate hosts for many species of Sarcocystis. Little is known of Sarcocystis cymruensis that uses the Brown rat (Rattus norvegicus) as intermediate hosts and the domestic cat (Felis catus) as experimental definitive host. Here, we identified and described Sarcocystis cymruensis in ...

Survival and passage of ingested New Zealand mudsnails through the intestinal tract of rainbow trout

USGS Publications Warehouse

Bruce, R. Louise; Moffitt, Christine M.; Dennis, Brian

2009-01-01

We conducted laboratory trials to determine the transit time and survival of New Zealand mudsnails Potamopyrgus antipodarum in the gastrointestinal tract of rainbow trout Oncorhynchus mykiss. To assess the rate of snail passage, we force-fed groups of fish a known quantity of snails and then held them in tanks. At selected intervals we removed individual fish from the test tanks and recorded the number of snails, their condition (live or dead), and their location in the gastrointestinal tract (stomach, anterior intestine, and posterior intestine). Feces were removed from tanks and examined for live snails. We repeated evaluations of passage rate and snail survival to determine the effects of varying the number of snails ingested, fish size, snail size, and feeding a commercial diet to fish after snail ingestion. We plotted and modeled gut evacuation using a stochastic model for ordinal data to consider each test variable. Snail passage rates were faster in fish that were fed smaller snails. Surprisingly, fish fed snails and then administered rations of commercial fish feed retained the snails longer in their stomach than did fish that were not administered fish feeds after being fed snails. Increased retention time of snails in the stomach decreased the probability of snail survival when voided in fecal material. Snails that passed through the gastrointestinal tract within 12–24 h of ingestion were often recovered live in fecal samples. However, no live snails were recovered from the posterior intestine or fecal material collected 24 h after ingestion. Using our results we propose potential management options that could reduce the risks of introducing live snails into new locations when stocking fish from infested hatcheries.

Experimental Test of Preferences for an Invasive Prey by an Endangered Predator: Implications for Conservation.

PubMed

Wilcox, Rebecca C; Fletcher, Robert J

2016-01-01

Identifying impacts of exotic species on native populations is central to ecology and conservation. Although the effects of exotic predators on native prey have received much attention, the role of exotic prey on native predators is poorly understood. Determining if native predators actively prefer invasive prey over native prey has implications for interpreting invasion impacts, identifying the presence of evolutionary traps, and predator persistence. One of the world's most invasive species, Pomacea maculata, has recently established in portions of the endangered Everglade snail kite's (Rostrhamus sociabilis plumbeus) geographic range. Although these exotic snails could provide additional prey resources, they are typically much larger than the native snail, which can lead to lower foraging success and the potential for diminished energetic benefits in comparison to native snails. Nonetheless, snail kites frequently forage on exotic snails. We used choice experiments to evaluate snail kite foraging preference in relation to exotic species and snail size. We found that snail kites do not show a preference for native or exotic snails. Rather, snail kites generally showed a preference for medium-sized snails, the sizes reflective of large native snails. These results suggest that while snail kites frequently forage on exotic snails in the wild, this behavior is likely driven simply by the abundance of exotic snails rather than snail kites preferring exotics. This lack of preference offers insights to hypotheses regarding effects of exotic species, guidance regarding habitat and invasive species management, and illustrates how native-exotic relationships can be misleading in the absence of experimental tests of such interactions.

[Effect evaluation of water conservancy project with ditches managed against Oncomelania hupensis in Yunnan Province].

PubMed

Ning-Bo, Huang; Peng, Huang; Zong-Ti, Shao; Xi-Guang, Feng; Yi, Dong; Guang-Huai, Yang; Jin-Song, Li; Yan-Hong, Zhang; Shao-Yun, Chen; Shou-Ju, Nie; Wen, Li

2016-03-11

To evaluate the effect of hydraulic schistosomiasis control project with ditches managed on Oncomelania hupensis snail control. From 2009 to 2011, the snail investigations and schistosomiasis surveillance were carried out in Dali City and Yongsheng County, two sites of national schistosomiasis surveillance. The history data of schistosomiasis control were collected and analyzed. At the harden sections of the water conservancy project with ditches managed in Shajing Village of Dali City, only one snail was found in 2010 with the density of living snails of 0.004 snails/0.1 m 2 , while the densities of living snails were respectively 0.080, 0.002 snails/0.1 m 2 and 0.007 snails/0.1 m2 in unhardened sections of the project from 2009 to 2011. No snails were found in the harden sections of the water conservancy project with ditches managed in Gaojiacun Village of Yongsheng County, while the densities of living snails were respectively 0.040, 0.030 snails/0.1 m2 and 0.040 snails/0.1 m2 in unhardened sections of the project from 2009 to 2011. After the ditches were hardened, no infected snails were found from 2009 to 2011, and the appearance rate of frames with snails and density of living snails were both decreased, while they were both higher in unhardened ditches. The hydraulic schistosomiasis control project has obvious effect on control snails, but the maintain work should be strengthened after the project is completed.

[Simulation experiment of survival and reproduction of artificially imported Oncomelania snails in Qingpu District, Shanghai].

PubMed

Tian, Jian-Guo; Li, Gui-Fu; Li, Jun; Zhang, Xiao-Ping; Jin, Yan-Jun; Cai, Li; Peng, Li-Xia; Xu, Hai-Yan; Xu, Rui-Fang

2013-06-01

To understand the survival of imported Oncomelania snails in new environments with different densities in waterway net region, Qingpu District, Shanghai. The snails collected from Guichi, Anhui Province were put into the ponds of 4 square meters and each had 25, 50, 100, 200, 400 and 800 pairs of snails, respectively. During the next 2 years, the temperature, humidity, the activities of snails and their second birth snails were investigated each day. All the data were analyzed statistically. The highest number of snails appeared from May to June on the surface of soils in different densities. The average numbers of snails were 2.0%-12.7% of whole put in snails, and the numbers of offspring were less than 2% of the whole put in snails. The survival and reproduction of artificially imported Oncomelania snails from Guichi, Anhui Province is not good in Qingpu District, Shanghai.

Field Studies Reveal Strong Postmating Isolation between Ecologically Divergent Butterfly Populations

PubMed Central

McBride, Carolyn S.; Singer, Michael C.

2010-01-01

Gene flow between populations that are adapting to distinct environments may be restricted if hybrids inherit maladaptive, intermediate phenotypes. This phenomenon, called extrinsic postzygotic isolation (EPI), is thought to play a critical role in the early stages of speciation. However, despite its intuitive appeal, we know surprisingly little about the strength and prevalence of EPI in nature, and even less about the specific phenotypes that tend to cause problems for hybrids. In this study, we searched for EPI among allopatric populations of the butterfly Euphydryas editha that have specialized on alternative host plants. These populations recall a situation thought typical of the very early stages of speciation. They lack consistent host-associated genetic differentiation at random nuclear loci and show no signs of reproductive incompatibility in the laboratory. However, they do differ consistently in diverse host-related traits. For each of these traits, we first asked whether hybrids between populations that use different hosts (different-host hybrids) were intermediate to parental populations and to hybrids between populations that use the same host (same-host hybrids). We then conducted field experiments to estimate the effects of intermediacy on fitness in nature. Our results revealed strong EPI under field conditions. Different-host hybrids exhibited an array of intermediate traits that were significantly maladaptive, including four behaviors. Intermediate foraging height slowed the growth of larvae, while intermediate oviposition preference, oviposition site height, and clutch size severely reduced the growth and survival of the offspring of adult females. We used our empirical data to construct a fitness surface on which different-host hybrids can be seen to fall in an adaptive valley between two peaks occupied by same-host hybrids. These findings demonstrate how ecological selection against hybrids can create a strong barrier to gene flow at the early stages of adaptive divergence. PMID:21048982

Defeating diplostomoid dangers in USA catfish aquaculture.

PubMed

Overstreet, Robin M; Curran, Stephen S

2004-06-01

Diplostomoid digenean metacercariae have caused widescale mortalities of channel catfish, Ictalurus punctatus (Rafinesque), at aquaculture farms in Louisiana, Mississippi and Arkansas, USA. Originally, based on a tentative diagnosis, the industry considered the primary harmful agent to be an introduced species from Europe, Bolbophorus confusus (Krause, 1914), frequently reported from the American white pelican, Pelecanus erythrorhynchos Gmelin. Our group has now shown, using ITS 1-2 plus three more-conservative gene fragments, that two sympatric species of Bolbophorus exist in the American white pelican. One, B. damnificus Overstreet et Curran, 2002, infects the musculature of catfish, and the other, probably not B. confusus, does not infect catfish. However, at least four other pathogenic diplostomoids and a clinostomoid infect the catfish, and they use at least four different snail hosts, including the planorbids Planorbella trivolvis (Say) and Gyraulus parvus (Say), the physid Physella gyrina (Say) and a lymnaeid. Two metacercariae, B. damnificus and Bursacetabulus pelecanus Dronen, Tehrany et Wardle, 1999, infect the catfish and mature in the pelican; two others, Austrodiplostomum compactum (Lutz, 1928) and Hysteromorpha cf. triloba (Rudolphi, 1819), mature in cormorants; one, Diplostomum sp., matures in seagulls and at least one, Clinostomum marginatum (Rudolphi, 1819), matures in herons, egrets and other wading birds. Consequently, management of catfish ponds relative to digenean infections requires considerable biological information on the fish, bird, and snail hosts as well as the parasites.

Multiple mechanisms of transmission of the Caribbean coral disease white plague

NASA Astrophysics Data System (ADS)

Clemens, E.; Brandt, M. E.

2015-12-01

White plague is one of the most devastating coral diseases in the Caribbean, and yet important aspects of its epidemiology, including how the disease transmits, remain unknown. This study tested potential mechanisms and rates of transmission of white plague in a laboratory setting. Transmission mechanisms including the transport of water, contact with macroalgae, and predation via corallivorous worms and snails were tested on the host species Orbicella annularis. Two of the tested mechanisms were shown to transmit disease: water transport and the corallivorous snail Coralliophila abbreviata. Between these transmission mechanisms, transport of water between a diseased coral and a healthy coral resulted in disease incidence significantly more frequently in exposed healthy corals. Transmission via water transport also occurred more quickly and was associated with higher rates of tissue loss (up to 3.5 cm d-1) than with the corallivorous snail treatment. In addition, water that was in contact with diseased corals but was filtered with a 0.22-μm filter prior to being introduced to apparently healthy corals also resulted in the transmission of disease signs, but at a much lower rate than when water was not filtered. This study has provided important information on the transmission potential of Caribbean white plague disease and highlights the need for a greater understanding of how these processes operate in the natural environment.

Linking neuroethology to the chemical biology of natural products: interactions between cone snails and their fish prey, a case study.

PubMed

Olivera, Baldomero M; Raghuraman, Shrinivasan; Schmidt, Eric W; Safavi-Hemami, Helena

2017-09-01

From a biological perspective, a natural product can be defined as a compound evolved by an organism for chemical interactions with another organism including prey, predator, competitor, pathogen, symbiont or host. Natural products hold tremendous potential as drug leads and have been extensively studied by chemists and biochemists in the pharmaceutical industry. However, the biological purpose for which a natural product evolved is rarely addressed. By focusing on a well-studied group of natural products-venom components from predatory marine cone snails-this review provides a rationale for why a better understanding of the evolution, biology and biochemistry of natural products will facilitate both neuroscience and the potential for drug leads. The larger goal is to establish a new sub-discipline in the broader field of neuroethology that we refer to as "Chemical Neuroethology", linking the substantial work carried out by chemists on natural products with accelerating advances in neuroethology.

Mortality affects adaptive allocation to growth and reproduction: field evidence from a guild of body snatchers

PubMed Central

2010-01-01

Background The probability of being killed by external factors (extrinsic mortality) should influence how individuals allocate limited resources to the competing processes of growth and reproduction. Increased extrinsic mortality should select for decreased allocation to growth and for increased reproductive effort. This study presents perhaps the first clear cross-species test of this hypothesis, capitalizing on the unique properties offered by a diverse guild of parasitic castrators (body snatchers). I quantify growth, reproductive effort, and expected extrinsic mortality for several species that, despite being different species, use the same species' phenotype for growth and survival. These are eight trematode parasitic castrators—the individuals of which infect and take over the bodies of the same host species—and their uninfected host, the California horn snail. Results As predicted, across species, growth decreased with increased extrinsic mortality, while reproductive effort increased with increased extrinsic mortality. The trematode parasitic castrator species (operating stolen host bodies) that were more likely to be killed by dominant species allocated less to growth and relatively more to current reproduction than did species with greater life expectancies. Both genders of uninfected snails fit into the patterns observed for the parasitic castrator species, allocating as much to growth and to current reproduction as expected given their probability of reproductive death (castration by trematode parasites). Additionally, species differences appeared to represent species-specific adaptations, not general plastic responses to local mortality risk. Conclusions Broadly, this research illustrates that parasitic castrator guilds can allow unique comparative tests discerning the forces promoting adaptive evolution. The specific findings of this study support the hypothesis that extrinsic mortality influences species differences in growth and reproduction. PMID:20459643

Transient SNAIL1 expression is necessary for metastatic competence in breast cancer.

PubMed

Tran, Hung D; Luitel, Krishna; Kim, Michael; Zhang, Kun; Longmore, Gregory D; Tran, David D

2014-11-01

SNAIL1 has been suggested to regulate breast cancer metastasis based on analyses of human breast tumor transcriptomes and experiments using cancer cell lines and xenografts. However, in vivo genetic experimental support for a role for SNAIL1 in breast cancer metastasis that develops in an immunocompetent tumor microenvironment has not been determined. To address this question, we created a genetic SNAIL1 model by coupling an endogenous SNAIL1 reporter with an inducible SNAIL1 transgene. Using multiple genetic models of breast cancer, we demonstrated that endogenous SNAIL1 expression was restricted to primary tumors that ultimately disseminate. SNAIL1 gene deletion either during the premalignant phase or after primary tumors have reached a palpable size blunted metastasis, indicating that late metastasis was the main driver of metastasis and that this was dependent on SNAIL1. Importantly, SNAIL1 expression during breast cancer metastasis was transient and forced transient, but not continuous. SNAIL1 expression in breast tumors was sufficient to increase metastasis. ©2014 American Association for Cancer Research.

[Establishment of Oncomelania hupensis snail database based on smartphone and Google Earth].

PubMed

Wang, Wei-chun; Zhan, Ti; Zhu, Ying-fu

2015-02-01

To establish an Oncomelania hupensis snail database based on smartphone and Google Earth. The HEAD GPS software was loaded in the smartphone first. The GPS data of the snails were collected by the smartphone. The original data were exported to the computer with the format of KMIUKMZ. Then the data were converted into Excel file format by using some software. Finally, the results based on laboratory were filled, and the digital snail data were established. The data were converted into KML, and then were showed by Google Earth visually. The snail data of a 5 hm2-beach along the Yangtze River were collected and the distribution of the snails based on Google Earth was obtained. The database of the snails was built. The query function was implemented about the number of the total snails, the living snails and the schistosome infected snails of each survey frame. The digital management of the snail data is realized by using the smartphone and Google Earth.

[Implementation of Oncomelania hupensis monitoring system based on Baidu Map].

PubMed

Zhi-Hua, Chen; Yi-Sheng, Zhu; Zhi-Qiang, Xue; Xue-Bing, Li; Yi-Min, Ding; Li-Jun, Bi; Kai-Min, Gao; You, Zhang

2017-10-25

To construct the Oncomelania hupensis snail monitoring system based on the Baidu Map. The environmental basic information about historical snail environment and existing snail environment, etc. was collected with the monitoring data about different kinds of O. hupensis snails, and then the O. hupensis snail monitoring system was built. Geographic Information System (GIS) and the electronic fence technology and Application Program Interface (API) were applied to set up the electronic fence of the snail surveillance environments, and the electronic fence was connected to the database of the snail surveillance. The O. hupensis snail monitoring system based on the Baidu Map were built up, including three modules of O. hupensis Snail Monitoring Environmental Database, Dynamic Monitoring Platform and Electronic Map. The information about monitoring O. hupensis snails could be obtained through the computer and smartphone simultaneously. The O. hupensis snail monitoring system, which is based on Baidu Map, is a visible platform to follow the process of snailsearching and molluscaciding.

Infection rate of Ehrlichia risticii, the agent of Potomac horse fever, in freshwater stream snails (Juga yrekaensis) from northern California.

PubMed

Pusterla, N; Johnson, E; Chae, J; Pusterla, J B; DeRock, E; Madigan, J E

2000-09-20

Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac horse fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (<15mm). The highest trematode infection rate for large and small snails was recorded in September and the lowest infection rate for large snails was recorded in June (Weed) and October (Montague). The E. risticii PCR infection rate among small snails from both sites was similar and varied monthly between 0 and 3.3%. The PCR infection rate for large snails from Weed was high in May (20.0%) and decreased progressively until November (10.0%). The PCR infection rate for large snails from Montague was 5.0% in May, 26.3% in August and 16. 7% in October. PCR-positive snails were always related to the microscopic detection of trematode stages (virgulate cercariae). This study provides evidence that J. yrekaensis are infected with trematode cercariae that harbor E. risticii. The number of snails harboring trematode stages and the number of PCR positive snails varied with the size of the snails, the month of collection, and the geographic origin.

BHC80 is Critical in Suppression of Snail-LSD1 Interaction and Breast Cancer Metastasis

DTIC Science & Technology

2014-04-01

Epithelial-mesenchymal transitions in development and disease . Cell 2009; 139:871-90. 9. Wu Y, Zhou BP. Snail: More than EMT. Cell Adh Migr 2010; 4:199...Huang RY, Nieto MA. Epithelial-mesenchymal transitions in development and disease . Cell 2009; 139:871-90. 9. Wu Y, Zhou BP. Snail: More than EMT. Cell...QSRKAFNCKYC Snail ( Canine ) QTRKAFNCKYC Snail (Monkey) QSRKAFNCKYC Snail (Opossum) QPRKAFICKVC A D E F CHX 0 1 3 5 7 0 1 3 5 7 WT Snail

External and internal shell formation in the ramshorn snail Marisa cornuarietis are extremes in a continuum of gradual variation in development

PubMed Central

2013-01-01

Background Toxic substances like heavy metals can inhibit and disrupt the normal embryonic development of organisms. Exposure to platinum during embryogenesis has been shown to lead to a “one fell swoop” internalization of the shell in the ramshorn snail Marisa cornuarietis, an event which has been discussed to be possibly indicative of processes in evolution which may result in dramatic changes in body plans. Results Whereas at usual cultivation temperature, 26°C, platinum inhibits the growth of both shell gland and mantle edge during embryogenesis leading to an internalization of the mantle and, thus, also of the shell, higher temperatures induce a re-start of the differential growth of the mantle edge and the shell gland after a period of inactivity. Here, developing embryos exhibit a broad spectrum of shell forms: in some individuals only the ventral part of the visceral sac is covered while others develop almost “normal” shells. Histological studies and scanning electron microscopy images revealed platinum to inhibit the differential growth of the shell gland and the mantle edge, and elevated temperature (28 - 30°C) to mitigate this platinum effect with varying efficiency. Conclusion We could show that the formation of internal, external, and intermediate shells is realized within the continuum of a developmental gradient defined by the degree of differential growth of the embryonic mantle edge and shell gland. The artificially induced internal and intermediate shells are first external and then partly internalized, similar to internal shells found in other molluscan groups. PMID:23682742

Laboratory assessment of molluscicidal and cercariacidal effects of Glinus lotoides fruits

PubMed Central

2014-01-01

Background The negative impact of synthetic molluscicides on the environment and their high cost necessitated search for an alternative approach of using plant extracts for the control of schistosomiasis. The objective of this study was, therefore, to evaluate aqueous and ethyl acetate crude extracts of Glinus lotoides fruits for their cercariacidal activity and molluscicidal effect against schistosome snail intermediate hosts. Methods Assessment of the molluscicidal activity against Biomphalaria pfeifferi was made by immersion method in accordance with WHO guideline. The results of mortality were statistically analyzed using probit analysis. The attenuating effect of the plant on Schistosoma mansoni cercariae was determined using establishment of adult worms as a parasitological parameter post exposure. Results The 24 and 48 hour-LC50 values for the aqueous extract of G. lotoides fruits were 47.1 and 44.1 mg/L, respectively, whereas that of ethyl acetate were 66.1 and 59.6 mg/L, respectively. The 24 and 48 hour LC90 values for the aqueous extract of G. lotoides fruits were 56.96 and 51.0 mg/L, respectively, while that of ethyl acetate were 77.2 and 70.0 mg/L, respectively. The in vitro cercariacidal activity was determined after 2 hrs of exposure to the aqueous plant extract. It was found out that the LC50 and LC90 values were 18.7 and 41.7 mg/L, respectively. Besides, infectivity of Schistosoma mansoni cercariae to mice was determined by exposing mice to cercariae pre-treated with the sub-lethal concentrations (3.7, 11.6 and 18.7 mg/L) of the aqueous extract. A significant reduction in worm burden in mice was obtained at 11.6 mg/L (p < 0.05). Moreover, the reduction in number of worms recovered was highly significant at 18.7 mg/L (p < 0.001). Conclusions The results showed that G. lotoides has molluscicidal activity against B. pfeifferi snails and cercariacidal activity against S. mansoni. Yet, further comprehensive evaluation is recommended for the possible use of G. lotoides against B. pfeifferi and the schistosome parasite. PMID:24713133

Altered dopamine levels induced by the parasite Profilicollis antarcticus on its intermediate host, the crab Hemigrapsus crenulatus.

PubMed

Rojas, José Miguel; Ojeda, F Patricio

2005-01-01

A serotonergic pathway is apparently involved in parasite-host interactions. Previous studies conducted in our laboratory showed increased rates in oxygen consumption and alterations in body posture in the crab Hemigrapsus crenulatus parasitized by the acanthocephalan, Profilicollis antarcticus. Such changes may be related to the functions described for biogenic amines in crustaceans. During the infective stage the acanthocephalans live freely in the hemocelomic cavity, suggesting that the possible alteration induced by biogenic amines may be related to their neurohormonal function in crustaceans. To test whether the presence of P. antarcticus produced neurohormonal changes in its intermediate host, H. crenulatus, we analyzed serotonin and dopamine levels in the host using HPLC with electrochemical detection. Two groups of 11 female crabs were studied; one group was artificially inoculated with two cystacanths while the other was used as the control. Our results show a dramatic increase in hemolymph dopamine, but not serotonin in H. crenulatus parasitized by the acanthocephalan P. antarcticus. Our results, along with those reported by Maynard (1996), suggest a parasite-specific strategy involved in the behavior alteration caused by the acanthocephalans on their intermediate host. The use of a biogenic amine as a mechanism of interaction by the parasites gives them an endless number of alternative potential actions on their intermediate hosts.

The evolution of complex life cycles when parasite mortality is size- or time-dependent.

PubMed

Ball, M A; Parker, G A; Chubb, J C

2008-07-07

In complex cycles, helminth larvae in their intermediate hosts typically grow to a fixed size. We define this cessation of growth before transmission to the next host as growth arrest at larval maturity (GALM). Where the larval parasite controls its own growth in the intermediate host, in order that growth eventually arrests, some form of size- or time-dependent increase in its death rate must apply. In contrast, the switch from growth to sexual reproduction in the definitive host can be regulated by constant (time-independent) mortality as in standard life history theory. We here develop a step-wise model for the evolution of complex helminth life cycles through trophic transmission, based on the approach of Parker et al. [2003a. Evolution of complex life cycles in helminth parasites. Nature London 425, 480-484], but which includes size- or time-dependent increase in mortality rate. We assume that the growing larval parasite has two components to its death rate: (i) a constant, size- or time-independent component, and (ii) a component that increases with size or time in the intermediate host. When growth stops at larval maturity, there is a discontinuous change in mortality to a constant (time-independent) rate. This model generates the same optimal size for the parasite larva at GALM in the intermediate host whether the evolutionary approach to the complex life cycle is by adding a new host above the original definitive host (upward incorporation), or below the original definitive host (downward incorporation). We discuss some unexplored problems for cases where complex life cycles evolve through trophic transmission.

Microbiological quality of raw and processed wild and cultured edible snails.

PubMed

Parlapani, Foteini F; Neofitou, Christos; Boziaris, Ioannis S

2014-03-15

An increasing interest in snail farming in Greece and other European countries has been observed. Despite the fact that edible snails have been involved with problems of Salmonella spp. contamination, there are to our knowledge only limited studies regarding microbiological safety and hygiene of such products. Enumeration of microbial populations and presence/absence of Salmonella spp. in snail meat and intestines of wild Cornu aspersum, Helix lucorum and cultured Cornu aspersum snails from indoor/outdoor type farms was conducted. Furthermore, snail-processing steps were simulated in the laboratory and the population reduction in snail meat was determined. Microbial populations were higher in intestines than snail meat in almost all cases. Escherichia coli/coliforms and Enterococcus spp. populations were lower in the intestines and snail meat of cultured C. aspersum. Salmonella spp. were detected in the intestines and snail meat of wild snails only. The high levels of bacterial populations were considerably reduced after the appropriate processing. The lower populations of E. coli/coliforms, Enterococcus spp. and especially the absence of Salmonella spp. in cultured snails show that the controlled conditions decrease the possibility of pathogen presence and contribute to food safety and public health. © 2013 Society of Chemical Industry.

North American Paragonimiasis (Caused by Paragonimus kellicotti) in the Context of Global Paragonimiasis

PubMed Central

Procop, Gary W.

2009-01-01

Summary: Paragonimus species are highly evolved parasites with a complex life cycle that involves at least three different hosts, i.e., snails, crustaceans, and mammals. The adult forms of Paragonimus species reside and mate in the lungs of a variety of permissive mammalian hosts, including humans. Although human paragonimiasis is uncommonly encountered in North America, both autochthonous and imported disease may be encountered. Paragonimus kellicotti, the species endemic to North America, is a well-known pathogen in wild and domestic animals. Five patients with North American paragonimiasis have been reported in the recent medical literature. The biologic, clinical, radiologic, and laboratory features of paragonimiasis are reviewed, with emphasis on North American paragonimiasis whenever possible. PMID:19597007

Landscape genetics of Schistocephalus solidus parasites in threespine stickleback (Gasterosteus aculeatus) from Alaska.

PubMed

Sprehn, C Grace; Blum, Michael J; Quinn, Thomas P; Heins, David C

2015-01-01

The nature of gene flow in parasites with complex life cycles is poorly understood, particularly when intermediate and definitive hosts have contrasting movement potential. We examined whether the fine-scale population genetic structure of the diphyllobothriidean cestode Schistocephalus solidus reflects the habits of intermediate threespine stickleback hosts or those of its definitive hosts, semi-aquatic piscivorous birds, to better understand complex host-parasite interactions. Seventeen lakes in the Cook Inlet region of south-central Alaska were sampled, including ten in the Matanuska-Susitna Valley, five on the Kenai Peninsula, and two in the Bristol Bay drainage. We analyzed sequence variation across a 759 bp region of the mitochondrial DNA (mtDNA) cytochrome oxidase I region for 1,026 S. solidus individuals sampled from 2009-2012. We also analyzed allelic variation at 8 microsatellite loci for 1,243 individuals. Analysis of mtDNA haplotype and microsatellite genotype variation recovered evidence of significant population genetic structure within S. solidus. Host, location, and year were factors in structuring observed genetic variation. Pairwise measures revealed significant differentiation among lakes, including a pattern of isolation-by-distance. Bayesian analysis identified three distinct genotypic clusters in the study region, little admixture within hosts and lakes, and a shift in genotype frequencies over time. Evidence of fine-scale population structure in S. solidus indicates that movement of its vagile, definitive avian hosts has less influence on gene flow than expected based solely on movement potential. Observed patterns of genetic variation may reflect genetic drift, behaviors of definitive hosts that constrain dispersal, life history of intermediate hosts, and adaptive specificity of S. solidus to intermediate host genotype.

Trials with a new molluscicide, Bayer 73, in Southern Rhodesia.

PubMed

SHIFF, C J

1961-01-01

The molluscicide Bayer 73 has been tested widely in laboratories and in small field experiments. It was decided in Southern Rhodesia, where mollusciciding is an important weapon in the control of bilharziasis, that the chemical should be tested against the local host snails both in the laboratory and on a large field scale. The results have been most encouraging and have led to the conclusion that Bayer 73 is one of the most effective molluscicides produced to date.

Seasonal feeding specialization on snails by river darters (Percina shumardi) with a review of snail feeding by other darter species

Treesearch

Wendell R. Haag; Melvin L. Warren

2006-01-01

We report food habits of River Darters (Percina shumardi) in Brushy Creek and the Sipsey Fork Black Warrior River, Alabama. River Darters preyed heavily on pleurocerid snails in both streams. Snail feeding varied widely among sample dates and was highest in October when snails represented nearly 100% of darter food items. Snail feeding declined...

A review of geographic information system and remote sensing with applications to the epidemiology and control of schistosomiasis in China.

PubMed

Yang, Guo-Jing; Vounatsou, Penelope; Zhou, Xiao-Nong; Utzinger, Jürg; Tanner, Marcel

2005-01-01

Geographic information system (GIS) and remote sensing (RS) technologies offer new opportunities for rapid assessment of endemic areas, provision of reliable estimates of populations at risk, prediction of disease distributions in areas that lack baseline data and are difficult to access, and guidance of intervention strategies, so that scarce resources can be allocated in a cost-effective manner. Here, we focus on the epidemiology and control of schistosomiasis in China and review GIS and RS applications to date. These include mapping prevalence and intensity data of Schistosoma japonicum at a large scale, and identifying and predicting suitable habitats for Oncomelania hupensis, the intermediate host snail of S. japonicum, at a small scale. Other prominent applications have been the prediction of infection risk due to ecological transformations, particularly those induced by floods and water resource developments, and the potential impact of climate change. We also discuss the limitations of the previous work, and outline potential new applications of GIS and RS techniques, namely quantitative GIS, WebGIS, and utilization of emerging satellite information, as they hold promise to further enhance infection risk mapping and disease prediction. Finally, we stress current research needs to overcome some of the remaining challenges of GIS and RS applications for schistosomiasis, so that further and sustained progress can be made to control this disease in China and elsewhere.

[Species composition and distribution of medical mollusca in Shanghai City].

PubMed

Guo, Yun-hai; Lv, Shan; Gu, Wen-biao; Liu, He-xiang; Wu, Ying; Zhang, Yi

2015-02-01

To investigate the species diversity and distribution of medical mollusca in Shanghai City. From August 2012 to October 2013, all kinds of habitats in 8 districts and counties in Shanghai City, namely Jiading, Qingpu, Baoshan, Minhang, Songjiang, Jinshan, Chongming, Pudong, were selected for the field survey according to the distribution characteristics of the river system, and all the specimens of medical mollusca in the investigation sites were collected and classified by morphological identification. Meanwhile, the species composition, habitats as well as the fauna of the medical mollusca collected were analyzed. A total of 5,211 specimens were collected, which belonged to 2 classes, 14 families, 18 genera and 25 species, including Oncomelania hupensis hupensis, Pomacea canaliculata, Parafossarulus striatulus, Alocinma longicornis, Physa acuta, Galba pervia, Hippeutis cantori, etc. The species numbers of medical mollusca in Chongming, Jinshan, Pudong new area and Qingpu districts (counties) were 22, 22, 21 and 20, respectively, which were more than those of other areas. The habitat analysis suggested that the species numbers in the river and wetland were the most, both of which were 14 species. The main faunas of the medical mollusca in Shanghai were the cosmopolitan and oriental species. The freshwater gastropod species are paucity in Shanghai City, but almost of them can be served as the intermediate hosts of certain parasites to transmit snail-related parasitic diseases, so the surveillance of medical mollusca should be strengthened.

Epidemiology and control of schistosomiasis: present situation and priorities for further research. Scientific Working Group on Schistosomiasis.

PubMed

1978-01-01

The article highlights specific aspects of the epidemiology of schistosomiasis where insufficient data are available on which to base appropriate control strategies. Emphasis is placed on the part that immunological techniques might play in improving the baseline epidemiological data. A study of acquired resistance to the disease is also important in relation to epidemiology and control. The clinical manifestations of the disease vary in different areas and further study of the relation between the clinical and pathological manifestations are therefore required. In relation to the intermediate host, the main priority for research concerns the definition of the location and time-patterns of transmission foci within any particular area: variations in transmission are of particular importance in relation to man-made water resources. Although chemotherapy will play an increasing role in control, its importance will depend on local conditions: coordinated and standardized trials are required of chemotherapeutic agents in different regions and in various defined groups of subjects. The effects of chemotherapy on immunity to reinfection and on immunopathology also require study. With all types of snail control-chemical, ecological, and biological-cost-effectiveness aspects are important. With chemicals, it is important to bear in mind other possible effects on the environment. In the field of water supplies and sanitation, several aspects are important in relation to schistosomiasis transmission and community involvement should be encouraged.

Associations of intestinal helminth infections with health parameters of spring-migrating female lesser scaup (Aythya affinis) in the upper Midwest, USA.

PubMed

Conner England, J; Levengood, Jeffrey M; Osborn, Josh M; Yetter, Aaron P; Suski, Cory D; Cole, Rebecca A; Hagy, Heath M

2018-06-01

Thousands of lesser scaup (Aythya affinis) die during spring and fall migrations through the upper Midwest, USA, from infections with Cyathocotyle bushiensis and Sphaeridiotrema spp. (Class: Trematoda) after ingesting infected intermediate hosts, such as non-native faucet snails (Bithynia tentaculata). The lesser scaup is a species of conservation concern and is highly susceptible to these infections. We collected female lesser scaup from spring migratory stopover locations throughout Illinois and Wisconsin and assessed biochemical and morphological indicators of health in relation to intestinal helminth loads. Helminth species diversity, total trematode abundance, and the infection intensities of the trematodes C. bushiensis and Sphaeridiotrema spp. were associated with percent body fat, blood metabolites, hematological measures, and an index of foraging habitat quality. Helminth diversity was negatively associated with percent body fat, albumin concentrations, and monocytes, whereas glucose concentrations displayed a slight, positive association. Total trematode abundance was negatively associated with blood concentrations of non-esterified fatty acids and albumin. Infections of C. bushiensis were positively related to basophil levels, whereas Sphaeridiotrema spp. infection intensity was negatively associated with packed cell volume and foraging habitat quality. Thus, commonly measured health metrics may indicate intestinal parasite infections and help waterfowl managers understand overall habitat quality. Intestinal parasitic loads offer another plausible mechanism underlying the spring condition hypothesis.

GABA-like immunoreactivity in Biomphalaria: Colocalization with tyrosine hydroxylase-like immunoreactivity in the feeding motor systems of panpulmonate snails.

PubMed

Vaasjo, Lee O; Quintana, Alexandra M; Habib, Mohamed R; Mendez de Jesus, Paola A; Croll, Roger P; Miller, Mark W

2018-08-01

The simpler nervous systems of certain invertebrates provide opportunities to examine colocalized classical neurotransmitters in the context of identified neurons and well defined neural circuits. This study examined the distribution of γ-aminobutyric acid-like immunoreactivity (GABAli) in the nervous system of the panpulmonates Biomphalaria glabrata and Biomphalaria alexandrina, major intermediate hosts for intestinal schistosomiasis. GABAli neurons were localized in the cerebral, pedal, and buccal ganglia of each species. With the exception of a projection to the base of the tentacle, GABAli fibers were confined to the CNS. As GABAli was previously reported to be colocalized with markers for dopamine (DA) in five neurons in the feeding network of the euopisthobranch gastropod Aplysia californica (Díaz-Ríos, Oyola, & Miller, 2002), double-labeling protocols were used to compare the distribution of GABAli with tyrosine hydroxylase immunoreactivity (THli). As in Aplysia, GABAli-THli colocalization was limited to five neurons, all of which were located in the buccal ganglion. Five GABAli-THli cells were also observed in the buccal ganglia of two other intensively studied panpulmonate species, Lymnaea stagnalis and Helisoma trivolvis. These findings indicate that colocalization of the classical neurotransmitters GABA and DA in feeding central pattern generator (CPG) interneurons preceded the divergence of euopisthobranch and panpulmonate taxa. These observations also support the hypothesis that heterogastropod feeding CPG networks exhibit a common universal design. © 2018 Wiley Periodicals, Inc.

From innovation to application: social-ecological context, diagnostics, drugs and integrated control of schistosomiasis.

PubMed

Utzinger, Jürg; N'goran, Eliézer K; Caffrey, Conor R; Keiser, Jennifer

2011-09-01

Compared to malaria, tuberculosis and HIV/AIDS, schistosomiasis remains a truly neglected tropical disease. Schistosomiasis, perhaps more than any other disease, is entrenched in prevailing social-ecological systems, since transmission is governed by human behaviour (e.g. open defecation and patterns of unprotected surface water contacts) and ecological features (e.g. living in close proximity to suitable freshwater bodies in which intermediate host snails proliferate). Moreover, schistosomiasis is intimately linked with poverty and the disease has spread to previously non-endemic areas as a result of demographic, ecological and engineering transformations. Importantly though, thanks to increased advocacy there is growing awareness, financial and technical support to control and eventually eliminate schistosomiasis as a public health problem at local, regional and global scales. The purpose of this review is to highlight recent progress made in innovation, validation and application of new tools and strategies for research and integrated control of schistosomiasis. First, we explain that schistosomiasis is deeply embedded in social-ecological systems and explore linkages with poverty. We then summarize and challenge global statistics, risk maps and burden estimates of human schistosomiasis. Discovery and development research pertaining to novel diagnostics and drugs forms the centrepiece of our review. We discuss unresolved issues and emerging opportunities for integrated and sustainable control of schistosomiasis and conclude with a series of research needs. Copyright © 2010 Elsevier B.V. All rights reserved.

Developing a climate-based risk map of fascioliasis outbreaks in Iran.

PubMed

Halimi, Mansour; Farajzadeh, Manuchehr; Delavari, Mahdi; Arbabi, Mohsen

2015-01-01

The strong relationship between climate and fascioliasis outbreaks enables the development of climate-based models to estimate the potential risk of fascioliasis outbreaks. This work aims to develop a climate-based risk map of fascioliasis outbreaks in Iran using Ollerenshaw's fascioliasis risk index incorporating geographical information system (GIS). Using this index, a risk map of fascioliasis outbreaks for the entire country was developed. We determined that the country can be divided into 4 fascioliasis outbreak risk categories. Class 1, in which the Mt value is less than 100, includes more than 0.91 of the country's area. The climate in this class is not conducive to fascioliasis outbreaks in any month. Dryness and low temperature in the wet season (December to April) are the key barriers against fascioliasis outbreaks in this class. The risk map developed based on climatic factors indicated that only 0.03 of the country's area, including Gilan province in the northern region of Iran, is highly suitable to fascioliasis outbreaks during September to January. The Mt value is greater than 500 in this class. Heavy rainfall in the summer and fall, especially in Rasht, Astara and Bandar Anzaly (≥ 1000 mm/year), creates more suitable breeding places for snail intermediate hosts. Copyright © 2015 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

Schistosome Materials for Vaccine Development.

DTIC Science & Technology

1981-09-01

snail/day; 100 or more adult worms/mouse; snail infection rates of 90% or more; death rates of in- fected snails 10% or less biweekly. Exposure...Recorded cercarial output, miracidial infectivity and snail death rates from 1976 to present as base line information for our snail-schistosome model

Inheritance of Schistosoma mansoni infection incompatibility in Biomphalaria alexandrina snails.

PubMed

El Naga, Iman F Abou; Eissa, Maha M; Mossallam, Shereen F; El-Halim, Safaa I Abd

2010-03-01

In this study, we looked at the inheritance of susceptibility and resistance to Schistosoma mansoni infection in the first generation of crossbred Biomphalaria alexandrina snails. Our ultimate goal is to use such information to develop a biological method of controlling schistosomiasis. We infected laboratory-bred snails with S. mansoni miracidia and examined cercarial shedding to determine susceptibility and resistance. Five parental groups were used: Group I contained 30 susceptible snails, Group II contained 30 resistant snails, Group III contained 15 susceptible and 15 resistant snails, Group IV contained 27 susceptible and three resistant snails and Group V contained three susceptible and 27 resistant snails. The percentage of resistant snails in the resulting progeny varied according to the ratio of susceptible and resistant parents per group; they are 7%, 100%, 68%, 45% and 97% from Groups I, II, III, IV and V, respectively. On increasing the percentage of resistant parent snails, the percentage of resistant progeny increased, while cercarial production in their susceptible progeny decreased.

An analysis of suppressing migratory effect on human urinary bladder cancer cell line by silencing of snail-1.

PubMed

Salehi, Shima; Mansoori, Behzad; Mohammadi, Ali; Davoudian, Sadaf; Musavi Shenas, Seyed Mohammad Hossein; Shajari, Neda; Majidi, Jafar; Baradaran, Behzad

2017-12-01

Snail-1 actively participates in tumor progression, invasion, and migration. Targeting snail-1 expression can suppress the EMT process in cancer. The aim of this study was to investigate the effect of snail1 silencing on urinary bladder cancer. Quantitative RT-PCR was used to detect snail-1 and other related metastatic genes expression following siRNA knockdown in urinary bladder cancer EJ-138 cells. The protein level of snail1 was assessed by Western blot. MTT and TUNEL assays were assessed to understand if snail-1 had survival effects on EJ-138 cells. Scratch wound healing assay measured cell motility effects after snail1 suppression. The significant silencing of snail-1 reached 60pmol siRNA in a 48-h post-transfection. The result of scratch assay showed that snail-1 silencing significantly decreased Vimentin, MMPs, and CXCR4 expression; however, expression of E-cadherin was induced. The cell death assay indicated that snail-1 played the crucial role in bladder cancer survival rate. These results propose that snail-1 plays a major role in the progression and migration of urinary bladder cancer, and can be a potential therapeutic target for target therapy of invasive urinary bladder cancer. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Intraguild predation by shore crabs affects mortality, behavior, growth, and densities of California horn snails

USGS Publications Warehouse

Lorda, J.; Hechinger, R.F.; Cooper, S. D.; Kuris, A. M.; Lafferty, Kevin D.

2016-01-01

The California horn snail, Cerithideopsis californica, and the shore crabs, Pachygrapsus crassipesand Hemigrapsus oregonensis, compete for epibenthic microalgae, but the crabs also eat snails. Such intraguild predation is common in nature, despite models predicting instability. Using a series of manipulations and field surveys, we examined intraguild predation from several angles, including the effects of stage-dependent predation along with direct consumptive and nonconsumptive predator effects on intraguild prey. In the laboratory, we found that crabs fed on macroalgae, snail eggs, and snails, and the size of consumed snails increased with predator crab size. In field experiments, snails grew less in the presence of crabs partially because snails behaved differently and were buried in the sediment (nonconsumptive effects). Consistent with these results, crab and snail abundances were negatively correlated in three field surveys conducted at three different spatial scales in estuaries of California, Baja California, and Baja California Sur: (1) among 61 sites spanning multiple habitat types in three estuaries, (2) among the habitats of 13 estuaries, and (3) among 34 tidal creek sites in one estuary. These results indicate that shore crabs are intraguild predators on California horn snails that affect snail populations via predation and by influencing snail behavior and performance.

Movements of florida apple snails in relation to water levels and drying events

USGS Publications Warehouse

Darby, P.C.; Bennetts, R.E.; Miller, S.J.; Percival, H.F.

2002-01-01

Florida apple snails (Pomacea Paludosa) apparently have only a limited tolerance to wetland drying events (although little direct evidence exists), but their populations routinely face dry downs under natural and managed water regimes. In this paper, we address speculation that apple snails respond to decreasing water levels and potential drying events by moving toward refugia that remain inundated. We monitored the movements of apple snails in central Florida, USA during drying events at the Blue Cypress Marsh (BC) and at Lake Kissimmee (LK). We monitored the weekly movements of 47 BC snails and 31 LK snails using radio-telemetry. Snails tended to stop moving when water depths were 10 cm. Snails moved along the greatest positive depth gradient (i.e., towards deeper water) when they encountered water depths between 10 and 20 cm. Snails tended to move toward shallower water in water depths ???50 cm, suggesting that snails were avoiding deep water areas such as canals and sloughs. Of the 11 BC snails originally located in the area that eventually went dry, three (27%) were found in deep water refugia by the end of the study. Only one of the 31 LK snails escaped the drying event by moving to deeper water. Our results indicate that some snails may opportunistically escape drying events through movement. The tendency to move toward deeper water was statistically significant and indicates that this behavioral trait might enhance survival when the spatial extent of a dry down is limited. However, as water level falls below 10 cm, snails stop moving and become stranded. As the spatial extent of a dry down increases, we predict that the number of snails stranded would increase proportionally. Stranded Pomacea paludosa must contend with dry marsh conditions, possibly by aestivation. Little more than anecdotal information has been published on P. paludosa aestivation, but it is a common adaptation among other apple snails (Caenogastropoda: Ampullaridae). ?? 2002, The Society of Wetland Scientists.

[Evaluation on cost-effectiveness of snail control project by environmental modification in hilly regions].

PubMed

Li, Shui-Ming; Chen, Shi-Jun; Wu, Xiao-Jun; Chen, Xi-Qing; Zhang, Rong-Ping; Zhang, Jian-Rong

2011-02-01

To evaluate the cost-effectiveness of the snail control project by environmental modification in order to provide the evidence for quickly interrupting the transmission of schistosomiasis in hilly regions. Field investigations were carried out. The changes of the snail habitat areas were compared before and after the snail control project. The direct costs of the snail control were calculated. The reduction rates of snail area and snail density were regarded as the evaluation indexes of the effectiveness. The costs for reduction of 1% of snail area and 1% of snail density were used as the unit for cost-effectiveness analysis. After the 15 projects were implemented, there were no snails in 12 areas. The reduction rates of snail areas were 72.22% to 100%. The reduction rates of the snail area and density were both 100% in the areas with digging new ditches to fill up the old ones and building reservoirs. The total cost of 15 projects was 1 450 800 Yuan. The average cost per unit was 0.56 Yuan/m2. After the snail control project by digging new ditches to fill up the old ones was implemented, the costs of snail area and density decreased by one unit were 300 -700 Yuan, by building reservoirs, the costs were 600 -2 600 Yuan, by building fishpond, the costs were 1 200 - 1 500 Yuan, by watershed comprehensive measures, the costs were 900 - 2 700 Yuan. The cost of digging new ditches to fill up the old ones was significantly lower than that of building reservoirs or watershed comprehensive measures, but there was no significant difference between building reservoirs and watershed comprehensive measures. In hilly regions, the implementation of snail control project by environmental modification combined with construction of water conservancy is effective, and the cost-effectiveness of the snail control with digging new ditches to fill up the old ones is excellent.

Modeling snail breeding in a bioregenerative life support system

NASA Astrophysics Data System (ADS)

Kovalev, V. S.; Manukovsky, N. S.; Tikhomirov, A. A.; Kolmakova, A. A.

2015-07-01

The discrete-time model of snail breeding consists of two sequentially linked submodels: "Stoichiometry" and "Population". In both submodels, a snail population is split up into twelve age groups within one year of age. The first submodel is used to simulate the metabolism of a single snail in each age group via the stoichiometric equation; the second submodel is used to optimize the age structure and the size of the snail population. Daily intake of snail meat by crewmen is a guideline which specifies the population productivity. The mass exchange of the snail unit inhabited by land snails of Achatina fulica is given as an outcome of step-by-step modeling. All simulations are performed using Solver Add-In of Excel 2007.

Tolerance of Oncomelania hupensis quadrasi to varying concentrations of dissolved oxygen and organic pollution*

PubMed Central

Garcia, Rolando G.

1972-01-01

Ecological investigations were made of habitats containing natural populations of the snail Oncomelania hupensis quadrasi and of habitats free from the snail in the island of Leyte, Philippines. This species of snail is a vector of Schistosoma japonicum in the Philippines. Snail-infested habitats had dissolved oxygen levels of 3.8-9.85 ppm but snail-free habitats had levels of only 0.08-3.6 ppm. Snail-infested habitats were less polluted by organic matter than habitats that were snail-free. Larger numbers of chlorophyll-bearing algae were present in both the water and the soil of snail-infested habitats. Other factors, including temperature, pH, hydrogen carbonate alkalinity, and relative humidity, were also investigated. PMID:4538906

Effects of pollution on land snail abundance, size and diversity as resources for pied flycatcher, Ficedula hypoleuca.

PubMed

Eeva, Tapio; Rainio, Kalle; Suominen, Otso

2010-09-01

Passerine birds need extra calcium during their breeding for developing egg shells and proper growth of nestling skeleton. Land snails are an important calcium source for many passerines and human-induced changes in snail populations may pose a severe problem for breeding birds. We studied from the bird's viewpoint how air pollution affects the shell mass, abundance and diversity of land snail communities along a pollution gradient of a copper smelter. We sampled remnant snail shells from the nests of an insectivorous passerine, the pied flycatcher, Ficedula hypoleuca, to find out how the availability of land snails varies along the pollution gradient. The total snail shell mass increased towards the pollution source but declined abruptly in the vicinity of the smelter. This spatial variation in shell mass was evident also within a single snail species and could not be wholly explained by spatially varying snail numbers or species composition. Instead, the total shell mass was related to their shell size, individuals being largest at the moderately polluted areas. Smaller shell size suggests inferior growth of snails in the most heavily polluted area. Our study shows that pollution affects the diversity, abundance (available shell mass) and individual quality of land snails, posing reproductive problems for birds that rely on snails as calcium sources during breeding. There are probably both direct pollution-related (heavy metal and calcium levels) and indirect (habitat change) effects behind the observed changes in snail populations. Copyright 2010 Elsevier B.V. All rights reserved.

Occurrence of Mesocestoides canislagopodis (Rudolphi, 1810) (Krabbe, 1865) in mammals and birds in Iceland and its molecular discrimination within the Mesocestoides species complex.

PubMed

Skirnisson, Karl; Jouet, Damien; Ferté, Hubert; Nielsen, Ólafur K

2016-07-01

The life cycle of Mesocestoides tapeworms (Cestoda: Cyclophyllidea: Mesocestoididae) requires three hosts. The first intermediate host is unknown but believed to be an arthropod. The second intermediate host is a vertebrate. The primary definitive host is a carnivore mammal, or a bird of prey, that eats the tetrathyridium-infected second intermediate host. One representative of the genus, Mesocestoides canislagopodis, has been reported from Iceland. It is common in the arctic fox (Vulpes lagopus) and has also been detected in domestic dogs (Canis familiaris) and cats (Felis domestica). Recently, scolices of a non-maturing Mesocestoides sp. have also been detected in gyrfalcon (Falco rusticolus) intestines, and tetrathyridia in the body cavity of rock ptarmigan (Lagopus muta). We examined the taxonomic relationship of Mesocestoides from arctic fox, gyrfalcon, and rock ptarmigan using molecular methods, both at the generic level (D1 domain LSU ribosomal DNA) and at the specific level (cytochrome c oxidase subunit I (COI) and 12S mitochondrial DNA). All stages belonged to Mesocestoides canislagopodis. Phylogenetic analysis of the combined 12S-COI at the specific level confirmed that M. canislagopodis forms a distinct clade, well separated from three other recognized representatives of the genus, M. litteratus, M. lineatus, and M. corti/vogae. This is the first molecular description of this species. The rock ptarmigan is a new second intermediate host record, and the gyrfalcon a new primary definitive host record. However, the adult stage seemed not to be able to mature in the gyrfalcon, and successful development is probably restricted to mammalian hosts.

Regulation of Msx genes by a Bmp gradient is essential for neural crest specification.

PubMed

Tribulo, Celeste; Aybar, Manuel J; Nguyen, Vu H; Mullins, Mary C; Mayor, Roberto

2003-12-01

There is evidence in Xenopus and zebrafish embryos that the neural crest/neural folds are specified at the border of the neural plate by a precise threshold concentration of a Bmp gradient. In order to understand the molecular mechanism by which a gradient of Bmp is able to specify the neural crest, we analyzed how the expression of Bmp targets, the Msx genes, is regulated and the role that Msx genes has in neural crest specification. As Msx genes are directly downstream of Bmp, we analyzed Msx gene expression after experimental modification in the level of Bmp activity by grafting a bead soaked with noggin into Xenopus embryos, by expressing in the ectoderm a dominant-negative Bmp4 or Bmp receptor in Xenopus and zebrafish embryos, and also through Bmp pathway component mutants in the zebrafish. All the results show that a reduction in the level of Bmp activity leads to an increase in the expression of Msx genes in the neural plate border. Interestingly, by reaching different levels of Bmp activity in animal cap ectoderm, we show that a specific concentration of Bmp induces msx1 expression to a level similar to that required to induce neural crest. Our results indicate that an intermediate level of Bmp activity specifies the expression of Msx genes in the neural fold region. In addition, we have analyzed the role that msx1 plays on neural crest specification. As msx1 has a role in dorsoventral pattering, we have carried out conditional gain- and loss-of-function experiments using different msx1 constructs fused to a glucocorticoid receptor element to avoid an early effect of this factor. We show that msx1 expression is able to induce all other early neural crest markers tested (snail, slug, foxd3) at the time of neural crest specification. Furthermore, the expression of a dominant negative of Msx genes leads to the inhibition of all the neural crest markers analyzed. It has been previously shown that snail is one of the earliest genes acting in the neural crest genetic cascade. In order to study the hierarchical relationship between msx1 and snail/slug we performed several rescue experiments using dominant negatives for these genes. The rescuing activity by snail and slug on neural crest development of the msx1 dominant negative, together with the inability of msx1 to rescue the dominant negatives of slug and snail strongly argue that msx1 is upstream of snail and slug in the genetic cascade that specifies the neural crest in the ectoderm. We propose a model where a gradient of Bmp activity specifies the expression of Msx genes in the neural folds, and that this expression is essential for the early specification of the neural crest.

Overexpression of Snail in retinal pigment epithelial triggered epithelial–mesenchymal transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hui; Li, Min; Xu, Ding

2014-03-28

Highlights: • First reported overexpression of Snail in RPE cells could directly trigger EMT. • Further confirmed the regulator role of Snail in RPE cells EMT in vitro. • Snail may be a potential therapeutic target to prevent the fibrosis of PVR. - Abstract: Snail transcription factor has been implicated as an important regulator in epithelial–mesenchymal transition (EMT) during tumourigenesis and fibrogenesis. Our previous work showed that Snail transcription factor was activated in transforming growth factor β1 (TGF-β1) induced EMT in retinal pigment epithelial (RPE) cells and may contribute to the development of retinal fibrotic disease such as proliferative vitreoretinopathymore » (PVR). However, whether Snail alone has a direct role on retinal pigment epithelial–mesenchymal transition has not been investigated. Here, we analyzed the capacity of Snail to drive EMT in human RPE cells. A vector encoding Snail gene or an empty vector were transfected into human RPE cell lines ARPE-19 respectively. Snail overexpression in ARPE-19 cells resulted in EMT, which was characterized by the expected phenotypic transition from a typical epithelial morphology to mesenchymal spindle-shaped. The expression of epithelial markers E-cadherin and Zona occludin-1 (ZO-1) were down-regulated, whereas mesenchymal markers a-smooth muscle actin (a-SMA) and fibronectin were up-regulated in Snail expression vector transfected cells. In addition, ectopic expression of Snail significantly enhanced ARPE-19 cell motility and migration. The present data suggest that overexpression of Snail in ARPE-19 cells could directly trigger EMT. These results may provide novel insight into understanding the regulator role of Snail in the development of retinal pigment epithelial–mesenchymal transition.« less

Infection with an acanthocephalan manipulates an amphipod's reaction to a fish predator's odours.

PubMed

Baldauf, Sebastian A; Thünken, Timo; Frommen, Joachim G; Bakker, Theo C M; Heupel, Oliver; Kullmann, Harald

2007-01-01

Many parasites with complex life cycles increase the chances of reaching a final host by adapting strategies to manipulate their intermediate host's appearance, condition or behaviour. The acanthocephalan parasite Pomphorhynchus laevis uses freshwater amphipods as intermediate hosts before reaching sexual maturity in predatory fish. We performed a series of choice experiments with infected and uninfected Gammarus pulex in order to distinguish between the effects of visual and olfactory predator cues on parasite-induced changes in host behaviour. When both visual and olfactory cues, as well as only olfactory cues were offered, infected and uninfected G. pulex showed significantly different preferences for the predator or the non-predator side. Uninfected individuals significantly avoided predator odours while infected individuals significantly preferred the side with predator odours. When only visual contact with a predator was allowed, infected and uninfected gammarids behaved similarly and had no significant preference. Thus, we believe we show for the first time that P. laevis increases its chance to reach a final host by olfactory-triggered manipulation of the anti-predator behaviour of its intermediate host.

Molecular analyses reveal high species diversity of trematodes in a sub-Arctic lake

USGS Publications Warehouse

Soldánová, Miroslava; Georgieva, Simona; Roháčováa, Jana; Knudsen, Rune; Kuhn, Jesper A.; Henriksen, Eirik H.; Siwertsson, Anna; Shaw, Jenny C.; Kuris, Armand M.; Amundsen, Per-Arne; Scholz, Tomáš; Lafferty, Kevin D.; Kostadinova, Aneta

2017-01-01

To identify trematode diversity and life-cycles in the sub-Arctic Lake Takvatn, Norway, we characterised 120 trematode isolates from mollusc first intermediate hosts, metacercariae from second intermediate host fishes and invertebrates, and adults from fish and invertebrate definitive hosts, using molecular techniques. Phylogenies based on nuclear and/or mtDNA revealed high species richness (24 species or species-level genetic lineages), and uncovered trematode diversity (16 putative new species) from five families typical in lake ecosystems (Allocreadiidae, Diplostomidae, Plagiorchiidae, Schistosomatidae and Strigeidae). Sampling potential invertebrate hosts allowed matching of sequence data for different stages, thus achieving molecular elucidation of trematode life-cycles and exploration of host-parasite interactions. Phylogenetic analyses also helped identify three major mollusc intermediate hosts (Radix balthica, Pisidium casertanum and Sphaerium sp.) in the lake. Our findings increase the known trematode diversity at the sub-Arctic Lake Takvatn, showing that digenean diversity is high in this otherwise depauperate sub-Arctic freshwater ecosystem, and indicating that sub-Arctic and Arctic ecosystems may be characterised by unique trematode assemblages.

[Preliminary observation on survival and reproduction of imported Oncomelania snails in water network regions: a simulated experiment].

PubMed

Tian, Jian-Guo; Zhong, Wen-Jiang; Li, Gui-Fu; Peng, Li-Xia; Xiang, Xiao-Ping

2011-04-01

To observe the survival and reproduction of exotic imported Oncomelania snails in water network regions. During a period between May 22, 2008 and August 7, 2009, a study pilot was established in a historical snail habitat in Qingpu District of Shanghai City. A total of 12 soil samples were collected from Qingpu, Jinshan and Songjiang districts and placed in the study area. Active marked adults snails without infections (with a female/male ratio of 1) were placed on soil surface, and the activity, survival and reproduction of snails on soil surface were observed. The temperature during the period of the study was recorded. During the experiment period, the highest temperature was 39 degrees C, the lowest was -3 degrees C, and the average was 20 degrees C. The activity of snails reduced significantly on the soil surface at high temperature in summer and low temperature in winter. There were 91 old snails (5.2%) that moved on soil surface in March and 73 (12.2% ) in June, 2009. A total of 26 and 59 offspring snails were found respectively in April and June, 2009, with average density of 2.17 snails/m2 (26/12) and 4.92 snails/m2 (59/12) respectively. The exotic imported snails can survive and reproduce in water network regions. Further monitoring should be strengthened on the imported snails in these regions.

Analysis of Snail1 function and regulation by Twist1 in palatal fusion.

PubMed

Yu, Wenli; Zhang, Yanping; Ruest, L Bruno; Svoboda, Kathy K H

2013-01-01

Palatal fusion is a tightly controlled process which comprises multiple cellular events, including cell movement and differentiation. Midline epithelial seam (MES) degradation is essential to palatal fusion. In this study, we analyzed the function of Snail1 during the degradation of the MES. We also analyzed the mechanism regulating the expression of the Snail1 gene in palatal shelves. Palatal explants treated with Snail1 siRNA did not degrade the MES and E-cadherin was not repressed leading to failure of palatal fusion. Transforming growth factor beta 3 (Tgfβ3) regulated Snail1 mRNA, as Snail1 expression decreased in response to Tgfβ3 neutralizing antibody and a PI-3 kinase (PI3K) inhibitor. Twist1, in collaboration with E2A factors, regulated the expression of Snail1. Twist1/E47 dimers bond to the Snail1 promoter to activate expression. Without E47, Twist1 repressed Snail1 expression. These results support the hypothesis that Tgfβ3 may signal through Twist1 and then Snail1 to downregulate E-cadherin expression during palatal fusion.

[Effect of water conservancy schistosomiasis control projects combined with molluscicide to control Oncomelania hupensis snails in rivers connecting with Yangtze River in Pukou District, Nanjing City].

PubMed

Qiang, Zhou; Li-Xin, Wan; De-Rong, Hang; Qi-Hui, You; Jun, You; Yu-Lin, Zhang; Zhao-Feng, Zhu; Yi-Xin, Huang

2017-12-07

To evaluate the effect of the water conservancy schistosomiasis control projects combined with molluscicide to control Oncomelania hupensis snails in the rivers connecting with the Yangtze River. The water conservancy schistosomiasis control projects of Zhujiashan River, Qili River and Gaowang River were chosen as the study objects in Pukou District, Nanjing City. The data review method and field investigation were used to evaluate the effect of the water conservancy schistosomiasis control projects combined with molluscicide to control O. hupensis snails. After the projects of the water level control and concrete slope protection and mollusciciding were implemented, the snails in the project river sections were completely eliminated. The snail diffusion did not happen in the inland irrigation area too. In the outside of the river beach, though the snails still existed, the snail densities plunged below 1.0 snail per 1.0 m 2 . The comprehensive measures of the combination of water level control, concrete slope protection and mollusciciding can effectively control and eliminate the snails, and prevent the snails from spreading.

Echinococcus multilocularis on Svalbard: introduction of an intermediate host has enabled the local life-cycle.

PubMed

Henttonen, H; Fuglei, E; Gower, C N; Haukisalmi, V; Ims, R A; Niemimaa, J; Yoccoz, N G

2001-12-01

The taeniid tapeworm Echinococcus multilocularis is here reported for the first time at the Svalbard Archipelago in the Norwegian Arctic. This new finding is interesting because the establishment of E. multilocularis is due to a recent anthropogenic introduction of its intermediate host--the sibling vole Microtus rossiaemeridionalis at Svalbard. The parasite itself has probably become naturally transferred to Svalbard due to migratory movements of its final host--the arctic fox Alopex lagopus between source areas for E. multilocularis in Siberia and Svalbard. We report macroscopically determined prevalence of E. multilocularis from a sample of 224 voles trapped in August in 1999 and 2000. The prevalence was among the highest ever recorded in intermediate hosts and was dependent on age and sex of the hosts approaching 100% in overwintered males. The high prevalence and the simplicity of the vole-arctic fox-E. multilocularis system at Svalbard makes it an eminent model system for further epidemiological studies.

Evolution of complex life cycles in trophically transmitted helminths. II. How do life-history stages adapt to their hosts?

PubMed

Parker, G A; Ball, M A; Chubb, J C

2015-02-01

We review how trophically transmitted helminths adapt to the special problems associated with successive hosts in complex cycles. In intermediate hosts, larvae typically show growth arrest at larval maturity (GALM). Theoretical models indicate that optimization of size at GALM requires larval mortality rate to increase with time between infection and GALM: low larval growth or paratenicity (no growth) arises from unfavourable growth and mortality rates in the intermediate host and low transmission rates to the definitive host. Reverse conditions favour high GALM size or continuous growth. Some support is found for these predictions. Intermediate host manipulation involves predation suppression (which decreases host vulnerability before the larva can establish in its next host) and predation enhancement (which increases host vulnerability after the larva can establish in its next host). Switches between suppression and enhancement suggest adaptive manipulation. Manipulation conflicts can occur between larvae of different ages/species a host individual. Larvae must usually develop to GALM before becoming infective to the next host, possibly due to trade-offs, e.g. between growth/survival in the present host and infection ability for the next host. In definitive hosts, if mortality rate is constant, optimal growth before switching to reproduction is set by the growth/morality rate ratio. Rarely, no growth occurs in definitive hosts, predicted (with empirical support) when larval size on infection exceeds growth/mortality rate. Tissue migration patterns and residence sites may be explained by variations in growth/mortality rates between host gut and soma, migration costs and benefits of releasing eggs in the gut. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Direct and ecological costs of resistance and tolerance in the stinging nettle.

PubMed

Puustinen, Susanna; Koskela, Tanja; Mutikainen, Pia

2004-03-01

Plant resistance and tolerance to herbivores, parasites, pathogens, and abiotic factors may involve two types of costs. First, resistance and tolerance may be costly in terms of plant fitness. Second, resistance and tolerance to multiple enemies may involve ecological trade-offs. Our study species, the stinging nettle ( Urtica dioicaL.) has significant variation among seed families in resistance and tolerance as well as costs of resistance and tolerance to the holoparasitic plant Cuscuta europaea L. Here we report on variation among seed families (i.e. genetic) in tolerance to nutrient limitation and in resistance to both mammalian herbivores (i.e. number of stinging trichomes) and an invertebrate herbivore (i.e. inverse of the performance of a generalist snail, Arianta arbustorum). Our results indicate direct fitness costs of snail resistance in terms of host reproduction whereas we did not detect fitness costs of mammalian resistance or tolerance to nutrient limitation. We further tested for ecological trade-offs among tolerance or resistance to the parasitic plant, herbivore resistance, and tolerance to nutrient limitation in the stinging nettle. Tolerance of nettles to nutrient limitation and resistance to mammalian herbivores tended to correlate negatively. However, there were no significant correlations among resistance and tolerance to the different natural enemies (i.e. parasitic plants, snails, and mammals). The results of this greenhouse study thus suggest that resistance and tolerance of nettles to diverse enemies are free to evolve independently of each other but not completely without direct costs in terms of plant fitness.

Schistosoma haematobium detection in snails by DraI PCR and Sh110/Sm-Sl PCR: further evidence of the interruption of schistosomiasis transmission in Morocco

PubMed Central

2014-01-01

Background This is the first study in Morocco to estimate snail infection rates at the last historic transmission sites of schistosomiasis, known to be free from new infection among humans since 2004. Screening of large numbers of snails for infection is one way to confirm that Schistosoma haematobium transmission has stopped and does not resurge. Methods A total of 2703 Bulinus truncatus snails were collected from 24 snail habitats in five provinces of Morocco: Errachidia, El Kelaa des Sraghna, Tata, Beni Mellal, and Chtouka Ait Baha. All visible snails were collected with a scoop net or by hand. We used waders and gloves as simple precautions. Snails were morphologically identified according to Moroccan Health Ministry guide of schistosomiasis (1982). All snails were analyzed in pools by molecular tool, using primers from the newly identified repeated DNA sequence, termed DraI, in the S. haematobium group. To distinguish S. bovis and S. haematobium, the snails were analyzed by Sh110/Sm-Sl PCR that was specific of S. haematobium. Results The results showed that snails from Errachidia, Chtouka Ait Baha, sector of Agoujgal in Tata and sector of Mbarkiya in El kelaa des Sraghna were negative for DraI PCR; but, snails from remaining snail habitats of El Kelaa des Sraghna, Tata and Beni Mellal were positive. This led to suggest the presence of circulating schistosome species (S. haematobium, S. bovis or others) within these positive snail habitats. Subsequently, confirmation with S. haematobium species specific molecular assay, Sh110/Sm-Sl PCR, showed that none of the collected snails were infected by S. haematobium in all historic endemic areas. Conclusion The absence of S. haematobium infection in snails supports the argument of S. haematobium transmission interruption in Morocco. PMID:24962624

Formation of RNA Granule-Derived Capsid Assembly Intermediates Appears To Be Conserved between Human Immunodeficiency Virus Type 1 and the Nonprimate Lentivirus Feline Immunodeficiency Virus.

PubMed

Reed, Jonathan C; Westergreen, Nick; Barajas, Brook C; Ressler, Dylan T B; Phuong, Daryl J; Swain, John V; Lingappa, Vishwanath R; Lingappa, Jaisri R

2018-05-01

During immature capsid assembly in cells, human immunodeficiency virus type 1 (HIV-1) Gag co-opts a host RNA granule, forming a pathway of intracellular assembly intermediates containing host components, including two cellular facilitators of assembly, ABCE1 and DDX6. A similar assembly pathway has been observed for other primate lentiviruses. Here we asked whether feline immunodeficiency virus (FIV), a nonprimate lentivirus, also forms RNA granule-derived capsid assembly intermediates. First, we showed that the released FIV immature capsid and a large FIV Gag-containing intracellular complex are unstable during analysis, unlike for HIV-1. We identified harvest conditions, including in situ cross-linking, that overcame this problem, revealing a series of FIV Gag-containing complexes corresponding in size to HIV-1 assembly intermediates. Previously, we showed that assembly-defective HIV-1 Gag mutants are arrested at specific assembly intermediates; here we identified four assembly-defective FIV Gag mutants, including three not previously studied, and demonstrated that they appear to be arrested at the same intermediate as the cognate HIV-1 mutants. Further evidence that these FIV Gag-containing complexes correspond to assembly intermediates came from coimmunoprecipitations demonstrating that endogenous ABCE1 and the RNA granule protein DDX6 are associated with FIV Gag, as shown previously for HIV-1 Gag, but are not associated with a ribosomal protein, at steady state. Additionally, we showed that FIV Gag associates with another RNA granule protein, DCP2. Finally, we validated the FIV Gag-ABCE1 and FIV Gag-DCP2 interactions with proximity ligation assays demonstrating colocalization in situ Together, these data support a model in which primate and nonprimate lentiviruses form intracellular capsid assembly intermediates derived from nontranslating host RNA granules. IMPORTANCE Like HIV-1 Gag, FIV Gag assembles into immature capsids; however, it is not known whether FIV Gag progresses through a pathway of immature capsid assembly intermediates derived from host RNA granules, as shown for HIV-1 Gag. Here we showed that FIV Gag forms complexes that resemble HIV-1 capsid assembly intermediates in size and in their association with ABCE1 and DDX6, two host facilitators of HIV-1 immature capsid assembly that are found in HIV-1 assembly intermediates. Our studies also showed that known and novel assembly-defective FIV Gag mutants fail to progress past putative intermediates in a pattern resembling that observed for HIV-1 Gag mutants. Finally, we used imaging to demonstrate colocalization of FIV Gag with ABCE1 and with the RNA granule protein DCP2. Thus, we conclude that formation of assembly intermediates derived from host RNA granules is likely conserved between primate and nonprimate lentiviruses and could provide targets for future antiviral strategies. Copyright © 2018 American Society for Microbiology.

Socioenvironmental factors associated with Schistosoma mansoni infection and intermediate hosts in an urban area of northeastern Brazil

PubMed Central

Souza, Geza Thais Rangel; Melo, Claudia Moura; Madi, Rubens Riscala; Jeraldo, Verónica de Lourdes Sierpe

2018-01-01

Schistosomiasis, which is caused by trematodes of the genus Schistosoma and by the species Schistosoma mansoni in Brazil, is transmitted primarily by Biomphalaria glabrata mollusks. Infections occur in humans and mollusks in freshwater environments contaminated with feces from infected humans. This study aimed to evaluate potential foci of schistosomiasis based on the identification of infection sites for the snails, factors that increased the human infection probability of S. mansoni infection, and the relationship of the disease with abiotic, biotic, and sociocultural factors. The study was conducted in an urban area on the northeast coast of Brazil; this location was chosen based on the following factors: the presence of B. glabrata, nearby freshwater, and the absence of sewer treatment. A parasitological analysis was performed to evaluate infections of the mollusks and residents inside the perimeter defined by the collection points. Questionnaires were applied to obtain demographic data and to identify behaviors that led to human infection. To verify the contamination of freshwater by human feces, a microbiological analysis of the water was performed at the mollusk collection points to determine the rate of contamination with fecal coliforms. A total of 10,270 B. glabrata mollusks were collected between August 2013 and August 2014, of which 8.8% were positive for S. mansoni; the prevalence ranged from 0 to 34.5% over the study period. A total of 232 coprological samples from the residents were analyzed. The S. mansoni infection prevalence rate was 16.4%, and the S. mansoni parasitic load in the infected residents was 54.9 eggs per gram of feces on average. Males were more affected by the parasite, especially in the 8-17-year-old age range. Thermotolerant coliforms were observed at the mollusk collection sites, which indicated that freshwater and sewage were in continuous contact. This contamination indicated poor sanitary conditions, as was previously observed, which could be combined with detrimental behavior due to the residents' habits. These conditions cause a predisposition for both intermediate and definitive infections of the hosts by creating a socioenvironmental scenario that is conducive to the formation and maintenance of potential schistosomiasis foci. This and similar areas deserve special attention from the government with an aim of improving sanitation services and local resident knowledge to prevent future contamination. PMID:29718924

The numbers game: quantitative analysis of Neorickettsia sp. propagation through complex life cycle of its digenean host using real-time qPCR.

PubMed

Greiman, Stephen E; Tkach, Vasyl V

2016-07-01

Bacteria of the genus Neorickettsia are obligate intracellular endosymbionts of parasitic flukes (Digenea) and are passed through the entire complex life cycle of the parasite by vertical transmission. Several species of Neorickettsia are known to cause diseases in domestic animals, wildlife, and humans. Quantitative data on the transmission of the bacteria through the digenean life cycle is almost completely lacking. This study quantified for the first time the abundance of Neorickettsia within multiple stages of the life cycle of the digenean Plagiorchis elegans. Snails Lymnaea stagnalis collected from a pond in North Dakota were screened for the presence of digenean cercariae, which were subsequently tested for the presence of Neorickettsia. Three L. stagnalis were found shedding P. elegans cercariae infected with Neorickettsia. These snails were used to initiate three separate laboratory life cycles and obtain all life cycle stages for bacterial quantification. A quantitative real-time PCR assay targeting the GroEL gene was developed to enumerate Neorickettsia sp. within different stages of the digenean life cycle. The number of bacteria significantly increased throughout all stages, from eggs to adults. The two largest increases in number of bacteria occurred during the period from eggs to cercariae and from 6-day metacercariae to 48-h juvenile worms. These two periods seem to be the most important for Neorickettsia propagation through the complex digenean life cycle and maturation in the definitive host.

Modeling apple snail population dynamics on the Everglades landscape

USGS Publications Warehouse

Darby, Phil; DeAngelis, Donald L.; Romañach, Stephanie; Suir, Kevin J.; Bridevaux, Joshua L.

2015-01-01

Comparisons of model output to empirical data indicate the need for more data to better understand, and eventually parameterize, several aspects of snail ecology in support of EverSnail. A primary value of EverSnail is its capacity to describe the relative response of snail abundance to alternative hydrologic scenarios considered for Everglades water management and restoration.

Nearly 400 million people are at higher risk of schistosomiasis because dams block the migration of snail-eating river prawns

USGS Publications Warehouse

Sokolow, Susanne H.; Jones, Isabel J.; Jocque, Merlijn M. T.; La, Diana; Cords, Olivia; Knight, Anika; Lund, Andrea; Wood, Chelsea L.; Lafferty, Kevin D.; Hoover, Christopher M.; Collender, Phillip A.; Remais, Justin V.; Lopez-Carr, David; Fisk, Jonathan; Kuris, Armand M.; De Leo, Giulio A.

2017-01-01

Dams have long been associated with elevated burdens of human schistosomiasis, but how dams increase disease is not always clear, in part because dams have many ecological and socio-economic effects. A recent hypothesis argues that dams block reproduction of the migratory river prawns that eat the snail hosts of schistosomiasis. In the Senegal River Basin, there is evidence that prawn populations declined and schistosomiasis increased after completion of the Diama Dam. Restoring prawns to a water-access site upstream of the dam reduced snail density and reinfection rates in people. However, whether a similar cascade of effects (from dams to prawns to snails to human schistosomiasis) occurs elsewhere is unknown. Here, we examine large dams worldwide and identify where their catchments intersect with endemic schistosomiasis and the historical habitat ranges of large, migratory Macrobrachium spp. prawns. River prawn habitats are widespread, and we estimate that 277–385 million people live within schistosomiasis-endemic regions where river prawns are or were present (out of the 800 million people who are at risk of schistosomiasis). Using a published repository of schistosomiasis studies in sub-Saharan Africa, we compared infection before and after the construction of 14 large dams for people living in: (i) upstream catchments within historical habitats of native prawns, (ii) comparable undammed watersheds, and (iii) dammed catchments beyond the historical reach of migratory prawns. Damming was followed by greater increases in schistosomiasis within prawn habitats than outside prawn habitats. We estimate that one third to one half of the global population-at-risk of schistosomiasis could benefit from restoration of native prawns. Because dams block prawn migrations, our results suggest that prawn extirpation contributes to the sharp increase of schistosomiasis after damming, and points to prawn restoration as an ecological solution for reducing human disease.

Nearly 400 million people are at higher risk of schistosomiasis because dams block the migration of snail-eating river prawns

NASA Astrophysics Data System (ADS)

Sokolow, S. H.; Jones, I. J.; La, D.; Cords, O.; Knight, A.; Lund, A.; Wood, C. L.; Lafferty, K. D.; Kuris, A. M.; Hoover, C.; Collender, P. A.; Remais, J.; Lopez-Carr, D.; De Leo, G.

2016-12-01

Dams have long been associated with elevated burdens of human schistosomiasis, but how dams increase disease is not always clear, in part because dams have many ecological and socioeconomic effects. A recent hypothesis argues that dams block reproduction of the migratory river prawns that eat the snail hosts of schistosomiasis. In the Senegal River Basin, there is evidence that prawn populations declined and schistosomiasis increased after completion of the Diama Dam. Restoring prawns to a water-access site upstream of the dam reduced snail density and reinfection rates in people. However, whether a similar cascade of effects (from dams to prawns to snails to human schistosomiasis) occurs elsewhere is unknown. Here, we examine large dams worldwide and identify where their catchments intersect with endemic schistosomiasis and the historical habitat ranges of large, migratory Macrobrachium spp. prawns. River prawn habitats are widespread, and we estimate that 277 to 385 million people live within schistosomiasis-endemic regions where river prawns are or were present (out of the 800 million people who are at risk of schistosomiasis). Using a published repository of schistosomiasis studies in sub-Saharan Africa, we compared infection before and after the construction of 14 large dams for people living in: (1) upstream catchments within historical habitats of native prawns, (2) comparable undammed watersheds, and (3) dammed catchments beyond the historical reach of migratory prawns. Damming was followed by greater increases in schistosomiasis within prawn habitats than outside prawn habitats. We estimate that one third to one half of the global population-at-risk of schistosomiasis could benefit from restoring native prawns. Because dams block prawn migrations, our results suggest that prawn extirpation contributes to the sharp increase of schistosomiasis after damming, and points to prawn restoration as an ecological solution for reducing human disease.

Nearly 400 million people are at higher risk of schistosomiasis because dams block the migration of snail-eating river prawns.

PubMed

Sokolow, Susanne H; Jones, Isabel J; Jocque, Merlijn; La, Diana; Cords, Olivia; Knight, Anika; Lund, Andrea; Wood, Chelsea L; Lafferty, Kevin D; Hoover, Christopher M; Collender, Phillip A; Remais, Justin V; Lopez-Carr, David; Fisk, Jonathan; Kuris, Armand M; De Leo, Giulio A

2017-06-05

Dams have long been associated with elevated burdens of human schistosomiasis, but how dams increase disease is not always clear, in part because dams have many ecological and socio-economic effects. A recent hypothesis argues that dams block reproduction of the migratory river prawns that eat the snail hosts of schistosomiasis. In the Senegal River Basin, there is evidence that prawn populations declined and schistosomiasis increased after completion of the Diama Dam. Restoring prawns to a water-access site upstream of the dam reduced snail density and reinfection rates in people. However, whether a similar cascade of effects (from dams to prawns to snails to human schistosomiasis) occurs elsewhere is unknown. Here, we examine large dams worldwide and identify where their catchments intersect with endemic schistosomiasis and the historical habitat ranges of large, migratory Macrobrachium spp. prawns. River prawn habitats are widespread, and we estimate that 277-385 million people live within schistosomiasis-endemic regions where river prawns are or were present (out of the 800 million people who are at risk of schistosomiasis). Using a published repository of schistosomiasis studies in sub-Saharan Africa, we compared infection before and after the construction of 14 large dams for people living in: (i) upstream catchments within historical habitats of native prawns, (ii) comparable undammed watersheds, and (iii) dammed catchments beyond the historical reach of migratory prawns. Damming was followed by greater increases in schistosomiasis within prawn habitats than outside prawn habitats. We estimate that one third to one half of the global population-at-risk of schistosomiasis could benefit from restoration of native prawns. Because dams block prawn migrations, our results suggest that prawn extirpation contributes to the sharp increase of schistosomiasis after damming, and points to prawn restoration as an ecological solution for reducing human disease.This article is part of the themed issue 'Conservation, biodiversity and infectious disease: scientific evidence and policy implications'. © 2017 The Authors.

Nearly 400 million people are at higher risk of schistosomiasis because dams block the migration of snail-eating river prawns

PubMed Central

Jones, Isabel J.; Jocque, Merlijn; La, Diana; Cords, Olivia; Knight, Anika; Lund, Andrea; Lafferty, Kevin D.; Hoover, Christopher M.; Collender, Phillip A.; Remais, Justin V.; Lopez-Carr, David; Kuris, Armand M.; De Leo, Giulio A.

2017-01-01

Dams have long been associated with elevated burdens of human schistosomiasis, but how dams increase disease is not always clear, in part because dams have many ecological and socio-economic effects. A recent hypothesis argues that dams block reproduction of the migratory river prawns that eat the snail hosts of schistosomiasis. In the Senegal River Basin, there is evidence that prawn populations declined and schistosomiasis increased after completion of the Diama Dam. Restoring prawns to a water-access site upstream of the dam reduced snail density and reinfection rates in people. However, whether a similar cascade of effects (from dams to prawns to snails to human schistosomiasis) occurs elsewhere is unknown. Here, we examine large dams worldwide and identify where their catchments intersect with endemic schistosomiasis and the historical habitat ranges of large, migratory Macrobrachium spp. prawns. River prawn habitats are widespread, and we estimate that 277–385 million people live within schistosomiasis-endemic regions where river prawns are or were present (out of the 800 million people who are at risk of schistosomiasis). Using a published repository of schistosomiasis studies in sub-Saharan Africa, we compared infection before and after the construction of 14 large dams for people living in: (i) upstream catchments within historical habitats of native prawns, (ii) comparable undammed watersheds, and (iii) dammed catchments beyond the historical reach of migratory prawns. Damming was followed by greater increases in schistosomiasis within prawn habitats than outside prawn habitats. We estimate that one third to one half of the global population-at-risk of schistosomiasis could benefit from restoration of native prawns. Because dams block prawn migrations, our results suggest that prawn extirpation contributes to the sharp increase of schistosomiasis after damming, and points to prawn restoration as an ecological solution for reducing human disease. This article is part of the themed issue ‘Conservation, biodiversity and infectious disease: scientific evidence and policy implications’. PMID:28438916

[Application of electronic fence technology based on GIS in Oncomelania hupensis snail monitoring].

PubMed

Zhi-Hua, Chen; Yi-Sheng, Zhu; Zhi-Qiang, Xue; Xue-Bing, Li; Yi-Min, Ding; Li-Jun, Bi; Kai-Min, Gao; You, Zhang

2017-07-27

To study the application of Geographic Information System (GIS) electronic fence technique in Oncomelania hupensis snail monitoring. The electronic fence was set around the history and existing snail environments in the electronic map, the information about snail monitoring and controlling was linked to the electronic fence, and the snail monitoring information system was established on these bases. The monitoring information was input through the computer and smart phone. The electronic fence around the history and existing snail environments was set in the electronic map (Baidu map), and the snail monitoring information system and smart phone APP were established. The monitoring information was input and upload real-time, and the snail monitoring information was demonstrated in real time on Baidu map. By using the electronic fence technology based on GIS, the unique "environment electronic archives" for each snail monitoring environment can be established in the electronic map, and real-time, dynamic monitoring and visual management can be realized.

[Study on distribution and countermeasures of Oncomelania snails in beach wetlands of Runzhou section of lower reaches of Yangtze River].

PubMed

Xia, Ai; Huang, Yixin; Jiang, Jun; Zhou, Ya-Min; Hang, De-rong; Tao, Heng-ye

2014-04-01

To understand the distribution of the river beach wetlands and Oncomelania snails in the lower reaches of the Yangtze River, and explore the countermeasures of snail control. The river beach wetlands outside the Yangtze River levee were investigated and classified according to the hierarchical and classification system of wetlands of China. The snail survey was carried out in the beach wetlands of Runzhou section of lower reaches of the Yangtze River from 2004 to 2013. The change trend of snail areas and the densities was analyzed in the wetlands. The river beach of Runzhou section of lower reaches of the Yangtze River belongs to the riverine wetland. There was Oncomelania snail breeding except the permanent water area. At present, there were natural wetlands of 1303.0 hm2, human-made wetlands of 1479.0 hmb2 and wetland function changes of 1059.0 hm2 in the river beach of Runzhou section. There was the snail area of 181.4 hm2 in the natural wetland in 2013. The area of snail control by the molluscicide and environmental modification was 4624.55 hm2 from 2004 to 2013. The decline rates of snail areas and densities were 66.53% and 77.66% respectively. The existing Oncomelania snails were distributed in the natural wetlands. The human-made wetland is helpful to snail control. The snail control in the river beach wetlands should attach a great importance to the protection of wetland ecology.

Density- and trait-mediated effects of a parasite and a predator in a tri-trophic food web

PubMed Central

Banerji, Aabir; Duncan, Alison B; Griffin, Joanne S; Humphries, Stuart; Petchey, Owen L; Kaltz, Oliver

2015-01-01

1. Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long-term population dynamics of non-host species or about whether such effects are density or trait mediated. 2. We studied a tri-trophic food chain comprised of (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium caudatum), (iii) a top predator (Didinium nasutum) and (iv) a parasite of the intermediate consumer (Holospora undulata). A fully factorial experimental manipulation of predator and parasite presence/absence was combined with analyses of population dynamics, modelling and analyses of host (Paramecium) morphology and behaviour. 3. Predation and parasitism each reduced the abundance of the intermediate consumer (Paramecium), and parasitism indirectly reduced the abundance of the basal resource (Serratia). However, in combination, predation and parasitism had non-additive effects on the abundance of the intermediate consumer, as well as on that of the basal resource. In both cases, the negative effect of parasitism seemed to be effaced by predation. 4. Infection of the intermediate consumer reduced predator abundance. Modelling and additional experimentation revealed that this was most likely due to parasite reduction of intermediate host abundance (a density-mediated effect), as opposed to changes in predator functional or numerical response. 5. Parasitism altered morphological and behavioural traits, by reducing host cell length and increasing the swimming speed of cells with moderate parasite loads. Additional tests showed no significant difference in Didinium feeding rate on infected and uninfected hosts, suggesting that the combination of these modifications does not affect host vulnerability to predation. However, estimated rates of encounter with Serratia based on these modifications were higher for infected Paramecium than for uninfected Paramecium. 6. A mixture of density-mediated and trait-mediated indirect effects of parasitism on non-host species creates rich and complex possibilities for effects of parasites in food webs that should be included in assessments of possible impacts of parasite eradication or introduction. PMID:25382389

Stable and clumped isotopes in shell carbonates of land snails Cathaica sp. and Bradybaena sp. in north China and implications for ecophysiological characteristics and paleoclimate studies

NASA Astrophysics Data System (ADS)

Wang, Xu; Cui, Linlin; Zhai, Jixuan; Ding, Zhongli

2016-01-01

Knowledge of ecophysiological characteristics of different land snail species is crucial for defining climatic significance of snail faunal assemblages. However, little work has been done in this aspect, hindering our obtaining unambiguous paleoclimatic information using these proxy indicators. Here we document for the first time the different ecophysiological characteristics of Cathaica sp. and Bradybaena sp. land snails using the stable isotopes and clumped isotope (Δ47) of the shell carbonates. The Δ47-derived temperatures for both species revealed a robust correlation with environmental temperatures. Moreover, the temperatures for Cathaica sp. are 3-5°C higher than those for Bradybaena sp. land snails, indicating different ecophysiological adaptations or growing seasons of the two species. Specifically, Cathaica sp. snails prefer living in a warm-humid summer, whereas Bradybaena sp. snails are active in the relatively cool-arid spring and/or autumn. The result testifies to the Δ47 in snail shell carbonates as a promising paleothermometer in monsoonal region and presents new insight into paleoclimatic explanation of these land snail species. This finding highlights the importance of climatic seasonality in the changes of the faunal assemblages of land snails.

Snail1 is required for the maintenance of the pancreatic acinar phenotype

PubMed Central

Loubat-Casanovas, Jordina; Peña, Raúl; Gonzàlez, Núria; Alba-Castellón, Lorena; Rosell, Santi; Francí, Clara; Navarro, Pilar; de Herreros, Antonio García

2016-01-01

The Snail1 transcriptional factor is required for correct embryonic development, yet its expression in adult animals is very limited and its functional roles are not evident. We have now conditionally inactivated Snail1 in adult mice and analyzed the phenotype of these animals. Snail1 ablation rapidly altered pancreas structure: one month after Snail1 depletion, acinar cells were markedly depleted, and pancreas accumulated adipose tissue. Snail1 expression was not detected in the epithelium but was in pancreatic mesenchymal cells (PMCs). Snail1 ablation in cultured PMCs downregulated the expression of several β-catenin/Tcf-4 target genes, modified the secretome of these cells and decreased their ability to maintain acinar markers in cultured pancreas cells. Finally, Snail1 deficiency modified the phenotype of pancreatic tumors generated in transgenic mice expressing c-myc under the control of the elastase promoter. Specifically, Snail1 depletion did not significantly alter the size of the tumors but accelerated acinar-ductal metaplasia. These results demonstrate that Snail1 is expressed in PMCs and plays a pivotal role in maintaining acinar cells within the pancreas in normal and pathological conditions. PMID:26735179

Modeling snail breeding in Bioregenerative Life Support System

NASA Astrophysics Data System (ADS)

Kovalev, Vladimir; Tikhomirov, Alexander A.; Nickolay Manukovsky, D..

It is known that snail meat is a high quality food that is rich in protein. Hence, heliciculture or land snail farming spreads worldwide because it is a profitable business. The possibility to use the snails of Helix pomatia in Biological Life Support System (BLSS) was studied by Japanese Researches. In that study land snails were considered to be producers of animal protein. Also, snail breeding was an important part of waste processing, because snails were capable to eat the inedible plant biomass. As opposed to the agricultural snail farming, heliciculture in BLSS should be more carefully planned. The purpose of our work was to develop a model for snail breeding in BLSS that can predict mass flow rates in and out of snail facility. There are three linked parts in the model called “Stoichiometry”, “Population” and “Mass balance”, which are used in turn. Snail population is divided into 12 age groups from oviposition to one year. In the submodel “Stoichiometry” the individual snail growth and metabolism in each of 12 age groups are described with stoichiometry equations. Reactants are written on the left side of the equations, while products are written on the right side. Stoichiometry formulas of reactants and products consist of four chemical elements: C, H, O, N. The reactants are feed and oxygen, products are carbon dioxide, metabolic water, snail meat, shell, feces, slime and eggs. If formulas of substances in the stoichiometry equations are substituted with their molar masses, then stoichiometry equations are transformed to the equations of molar mass balance. To get the real mass balance of individual snail growth and metabolism one should multiply the value of each molar mass in the equations on the scale parameter, which is the ratio between mass of monthly consumed feed and molar mass of feed. Mass of monthly consumed feed and stoichiometry coefficients of formulas of meat, shell, feces, slime and eggs should be determined experimentally. An age structure and size of snail population are optimized on the base of individual growth and metabolic characteristics with the help of the second submodel "Population". In this simulation a daily amount of snail meat consumed by crewmembers is a guideline which specifies population productivity. Also, the daily amount of snail meat may have an optional value. Prescribed population characteristics are used in the third submodel "Mass balance" to equalize input and output mass flow rates of snail facility. In this submodel we add a water and ash to the organic masses of feed, meat, feces, shell and eggs. Moreover, masses of calcium carbonate and potable water are added to the left side of mass balance equations. Mass of calcium carbonate is distributed among shell, feces and eggs. Summarizing the twelve equations for each snail age, we get the mass balance equation for the snail facility. All simulations are performed by using Solver Add-In for Excel 2007.

Natural infection of trematodes in Lymnaea (Radix) auricularia rubiginosa in water reservoirs in Amphoe Muang, Khon Kaen Province.

PubMed

Charoenchai, A; Tesana, S; Pholpark, M

1997-01-01

Lymnaea (Radix) auricularia rubiginosa (Michelin, 1831) was surveyed in 54 reservoirs of 18 districts in Amphoe Muang, Khon Kaen Province during February to May 1994. Lymnaeid snails were found in the water of 20 reservoirs, of which 16 reservoirs contained clear water and 4 turbid water. Two of the four turbid water reservoirs received drainage water from Khon Kaen Town. Two thousand four hundred and eight L. auricularia rubiginosa were collected and examined by shedding and crushing. Trematode infection occurred in 163 (6.77%) of 2,408 L. auricularia rubiginosa and some snails were infected with more than one cercarial species. Ninety-nine snails (4.11%) were infected with echinostomes, while mixed infection of echinostomes with Fasciola gigantica and with schistosomes was found in 5 snails (0.21%) and 2 snails (0.08%), respectively. Only 1 snail (0.04%), 19 snails (0.79%) and 37 snails (1.54%) were infected with F. gigantica, schistosomes and unidentified species, respectively. The mean size of infected snails was 6.89 +/- 2.02 mm (6.20-22.36) while the mean of sampled snails was 13.46 +/- 3.64 mm (4.00-26.55). The water plants which were found in reservoirs and presented with snails, were creeping water primose (Jusstaea repens), water lily (Nymphaea sp), water hyacinths (Eichornia crassipes) and grass.

Paratenic hosts as regular transmission route in the acanthocephalan Pomphorhynchus laevis: potential implications for food webs

NASA Astrophysics Data System (ADS)

Médoc, Vincent; Rigaud, Thierry; Motreuil, Sébastien; Perrot-Minnot, Marie-Jeanne; Bollache, Loïc

2011-10-01

Although trophically transmitted parasites are recognized to strongly influence food-web dynamics through their ability to manipulate host phenotype, our knowledge of their host spectrum is often imperfect. This is particularly true for the facultative paratenic hosts, which receive little interest. We investigated the occurrence and significance both in terms of ecology and evolution of paratenic hosts in the life cycle of the fish acanthocephalan Pomphorhynchus laevis. This freshwater parasite uses amphipods as intermediate hosts and cyprinids and salmonids as definitive hosts. Within a cohort of parasite larvae, usually reported in amphipod intermediate hosts, more than 90% were actually hosted by small-sized fish. We demonstrated experimentally, using one of these fish, that they get infected through the consumption of parasitized amphipods and contribute to the parasite's transmission to a definitive host, hence confirming their paratenic host status. A better knowledge of paratenic host spectrums could help us to understand the fine tuning of transmission strategies, to better estimate parasite biomass, and could improve our perception of parasite subwebs in terms of host-parasite and predator-parasite links.

Physiological response to low temperature in the freshwater apple snail, Pomacea canaliculata (Gastropoda: Ampullariidae).

PubMed

Matsukura, Keiichiro; Tsumuki, Hisaaki; Izumi, Yohei; Wada, Takashi

2009-08-01

Cold hardiness of the freshwater apple snail, Pomacea canaliculata, varies seasonally. We investigated lethal factors and physiological changes arising from exposure of P. canaliculata to low temperatures. Snails did not survive freezing. The supercooling point of cold-acclimated (cold tolerant) snails (-6.6+/-0.8 degrees C) did not differ significantly from that of non-acclimated ones (-7.1+/-1.5 degrees C) under laboratory conditions. Furthermore, snails died even under more moderately low temperatures approaching 0 degrees C. These results indicate that indirect chilling injury is a factor in the death of P. canaliculata at low temperatures. Regardless of whether the snails were acclimated to low temperatures, all of the dead, and even some of the snails still alive at 0 degrees C, had injured mantles, indicating that the mantle may be the organ most susceptible to the effects of low temperatures. The concentration of glucose in the posterior chamber of the kidney and concentration of glycerol in the digestive gland were significantly higher in cold-acclimated snails than in non-acclimated ones, suggesting carbohydrate metabolic pathways are altered in snails during cold acclimation.

Characteristics of the larval Echinococcus vogeli Rausch and Bernstein, 1972 in the natural intermediate host, the paca, Cuniculus paca L. (Rodentia: Dasyproctidae).

PubMed

Rausch, R L; D'Alessandro, A; Rausch, V R

1981-09-01

In Colombia, the natural intermediate host of Echinococcus vogeli Rausch and Bernstein, 1972 is the paca, Cuniculus paca L. (Rodentia: Dasyproctidae). The larval cestode develops in the liver of the host, where it usually is situated superficially, partly exposed beneath Glisson's capsule. The infective larva consists of a subspherical to asymmetrical, fluid-filled vesicle, up to 30 mm in diameter, enclosed by a thick laminated membrane. It typically contains numerous chambers, often interconnected, produced by endogenous proliferation of germinal and laminated tissue, within which brood capsules arise in an irregular pattern from the germinal layer. Invasive growth by means of exogenous proliferation, typical of infections in man, was not observed in the natural intermediate host. The development of the larval cestode is described on the basis of material from pacas, supplemented by observations on early-stage lesions in experimentally infected nutrias, Myocastor coypus (Molina) (Rodentia: Capromyidae). The tissue response is characterized for early-stage, mature (infective), and degenerating larvae in the comparatively long-lived intermediate host. In addition to previously reported differences in size and form of rostellar hooks, other morphologic characteristics are defined by which the larval stage of E. vogeli is distinguished from that of E. oligarthrus (Diesing, 1863). Pathogenesis by the larval E. vogeli in man, like that by the larval E. multilocularis Leuckart, 1863, is the consequence of atypical proliferation of vesicles attributable to parasite-host incompatibility.

Behavioural and physiological effects of the trophically transmitted cestode parasite, Cyathocephalus truncatus, on its intermediate host, Gammarus pulex.

PubMed

Franceschi, N; Rigaud, T; Moret, Y; Hervant, F; Bollache, L

2007-11-01

Some parasites with complex life-cycles are able to manipulate the behaviour of their intermediate hosts in a way that increases their transmission to the next host. Gammarids infected by the tapeworm Cyathocephalus truncatus (Cestoda: Spathebothriidea) are known to be more predated by fish than uninfected ones, but potential behavioural manipulation by the parasite has never been investigated. In this study, we tested the hypothesis that C. truncatus is able to manipulate the behaviour of one of its intermediate hosts, Gammarus pulex (Crustacea: Amphipoda). To assess if any behavioural change was linked to other phenotypic alterations, we also measured the immunity of infected and uninfected individuals and investigated the pathogenic effects of the parasite. Infected gammarids were significantly less photophobic than uninfected ones, but no effect of infection on the level of immune defence was found. The results on survival, swimming activity and oxygen consumption suggest that the parasite also has various pathogenic effects. However, the alteration in host phototaxis was not correlated to some of these pathogenic effects. Therefore, we propose that the modification in host reaction to light is a behavioural manipulation, explaining the previously observed increase of gammarid predation rate.

The phylogeny and life cycle of two species of Profilicollis (Acanthocephala: Polymorphidae) in marine hosts off the Pacific coast of Chile.

PubMed

Rodríguez, S M; D'Elía, G; Valdivia, N

2017-09-01

Resolving complex life cycles of parasites is a major goal of parasitological research. The aim of this study was to analyse the life cycle of two species of the genus Profilicollis, the taxonomy of which is still unstable and life cycles unclear. We extracted individuals of Profilicollis from two species of crustaceans (intermediate hosts) and four species of seagulls (definitive hosts) from sandy-shore and estuarine habitats along the south-east Pacific coast of Chile. Mitochondrial DNA analyses showed that two species of Profilicollis infected intermediate hosts from segregated habitats: while P. altmani larvae infected exclusively molecrabs of the genus Emerita from fully marine habitats, P. antarcticus larvae infected the crab Hemigrapsus crenulatus from estuarine habitats. Moreover, P. altmani completed its life cycle in four seagulls, Chroicocephalus maculipennis, Leucopheus pipixcan, Larus modestus and L. dominicanus, while P. antarcticus, on the other hand, completed its life cycle in the kelp gull L. dominicanus. Accordingly, our results show that two congeneric parasites use different and spatially segregated species as intermediate hosts, and both are capable of infecting one species of definitive hosts. As such, our analyses allow us to shed light on a complex interaction network.

Establishment of first engineering specifications for environmental modification to eliminate schistosomiasis epidemic foci in urban areas.

PubMed

Kong, Shibo; Tan, Xiaodong; Deng, Zhiqing; Xie, Yaofei; Yang, Fen; Zheng, Zengwang

2017-08-01

Snail control is a key link in schistosomiasis control, but no unified methods for eliminating snails have been produced to date. This study was conducted to explore an engineering method for eliminating Oncomelania hupensis applicable to urban areas. The engineering specifications were established using the Delphi method. An engineering project based on these specifications was conducted in Hankou marshland to eliminate snails, including the transformation of the beach surface and ditches. Molluscicide was used as a supplement. The snail control effect was evaluated by field investigation. The engineering results fulfilled the requirements of the design. The snail density decreased to 0/0.11m 2 , and the snail area dropped to 0m 2 after the project. There was a statistically significant difference in the number of frames with snails before and after the project (P<0.05). Snails were completely eliminated through one year of continuous monitoring, and no new snails were found after a flood disaster. This study demonstrates that engineering specifications for environmental modification were successfully established. Environmental modification, mainly through beach and ditch remediation, can completely change the environment of Oncomelania breeding. This method of environmental modification combined with mollusciciding was highly effective at eliminating snails. Copyright © 2017 Elsevier B.V. All rights reserved.

Activity of the mangrove snail Cerithidea decollata (Gastropoda: Potamididae) in a warm temperate South African estuary

NASA Astrophysics Data System (ADS)

Hodgson, Alan N.; Dickens, John

2012-08-01

A population of Cerithidea decollata, an intertidal marine gastropod usually found within mangroves, was studied within an area of Juncus kraussii in the upper reaches of the warm temperate Knysna estuary, which is at the southern-most limit of the recorded distribution of this snail. Activity (migratory and homing behaviour, distances travelled during foraging) of the snails was monitored over spring and neap tides in four seasons. Migratory patterns of the snails were affected by season, time of low tide (day vs night), tidal magnitude (spring vs neap) and zonation. In the summer and spring, a greater proportion of snails migrated from J. kraussii leaves onto the mud during the day at spring low tide. During neap tides in these two seasons, most snails did not climb J. kraussii leaves and remained on the mud, which was nearly always exposed. In autumn a few snails only were active and in winter snails were almost completely inactive, probably due to low air temperatures. Snails travelled greater distances on the mud on spring tides, during the diurnal low tides, and in the summer. No snails were found to home to individual J. kraussii leaves; however, homing behaviour was recorded to wooden poles within the Juncus wetland.

Population estimate of Chinese mystery snail (Bellamya chinensis) in a Nebraska reservoir

USGS Publications Warehouse

Chaine, Noelle M.; Allen, Craig R.; Fricke, Kent A.; Haak, Danielle M.; Hellman, Michelle L.; Kill, Robert A.; Nemec, Kristine T.; Pope, Kevin L.; Smeenk, Nicholas A.; Stephen, Bruce J.; Uden, Daniel R.; Unstad, Kody M.; VanderHam, Ashley E.

2012-01-01

The Chinese mystery snail (Bellamya chinensis) is an aquatic invasive species in North America. Little is known regarding this species' impacts on freshwater ecosystems. It is be lieved that population densities can be high, yet no population estimates have been reported. We utilized a mark-recapture approach to generate a population estimate for Chinese mystery snail in Wild Plum Lake, a 6.47-ha reservoir in southeast Nebraska. We calculated, using bias-adjusted Lincoln-Petersen estimation, that there were approximately 664 adult snails within a 127 m2 transect (5.2 snails/m2). If this density was consistent throughout the littoral zone (<3 m in depth) of the reservoir, then the total adult population in this impoundment is estimated to be 253,570 snails, and the total Chinese mystery snail wet biomass is estimated to be 3,119 kg (643 kg/ha). If this density is confined to the depth sampled in this study (1.46 m), then the adult population is estimated to be 169,400 snails, and wet biomass is estimated to be 2,084 kg (643 kg/ha). Additional research is warranted to further test the utility of mark-recapture methods for aquatic snails and to better understand Chinese mystery snail distributions within reservoirs.

The development of Neoechinorhynchus buttnerae (Eoacanthocephala: Neoechinorhynchidae) in its intermediate host Cypridopsis vidua in Brazil.

PubMed

Lourenço, Felipe de Sousa; Morey, Germán Augusto Murrieta; Malta, José Celso de Oliveira

2018-06-26

The family Neoechinorhynchidae includes seven species of Neoechinorhynchus from freshwater fishes of Brazil. Although several Neoechinorhynchus species are cited infecting different fish species in Brazil, there is a lack of information concerning to their life cycle and the identification of the intermediate hosts. Thus, the aim of the present study was to describe the development of Neoechinorhynchus buttnerae in its intermediate host collected in a fish farm located in Rio Preto da Eva, Amazonas, Brazil. To verify the presence of N. buttnerae in the fish pond, twenty Colossoma macropomum were captured and analyzed, being corroborated the presence of this parasite species. Samples of plankton were also collected, finding the ostracod Cypridopsis vidua as the intermediate host. For the description of the larvae development, a laboratory experimental procedure was conducted by feeding the collected ostracods with the eggs of the adult specimens taken from the sampled fish. To observe the stages of development an artificial hatch was performed. Every stage of development was photographed, measured, drawn and described. The time of development of the immature stages of N. buttnerae was 29 days, reporting the stages: acanthor, acanthella (with eight developmental changes) and cystacanth. As high infections by N. buttnerae causes morphological damages to the intestine and may compromise the quality of C. macropomum and in consequence the production of fish farmers in the Brazilian Amazon region, the knowledge of its intermediate host and the understanding of its life cycle represents a useful information to prevent and combat infections by this parasite.

Micro-evolutionary implications of allozymic and morphometric variations in sealworms Pseudoterranova sp. (Ascaridoidea: Anisakidae) among sympatric hosts from the southeastern Pacific Ocean.

PubMed

George-Nascimento, M; Llanos, A

1995-10-01

We found significant morphometric and electrophoretic differences between sealworm larvae collected from four sympatric fish host species off the central coast of Chile. The South American sea lion, Otaria byronia, is a suitable host and most likely the only definitive host species in the study area. Morphological patterns of caudal papillae in adult males collected from sea lions and electrophoretic evidence from larvae and adults substantiate our conclusion that they belong to just one, new species yet to be described. The genetic and morphometric differences found between sealworm larvae from sympatric fish hosts may be due to selective pressures arising from the internal environment of the intermediate hosts, although they may serve only for passing sequential filters along the life cycle. The discussion deals with the roles that definitive and intermediate hosts may play in the micro-evolutionary processes of sealworms.

Snails home

NASA Astrophysics Data System (ADS)

Dunstan, D. J.; Hodgson, D. J.

2014-06-01

Many gardeners and horticulturalists seek non-chemical methods to control populations of snails. It has frequently been reported that snails that are marked and removed from a garden are later found in the garden again. This phenomenon is often cited as evidence for a homing instinct. We report a systematic study of the snail population in a small suburban garden, in which large numbers of snails were marked and removed over a period of about 6 months. While many returned, inferring a homing instinct from this evidence requires statistical modelling. Monte Carlo techniques demonstrate that movements of snails are better explained by drift under the influence of a homing instinct than by random diffusion. Maximum likelihood techniques infer the existence of two groups of snails in the garden: members of a larger population that show little affinity to the garden itself, and core members of a local garden population that regularly return to their home if removed. The data are strongly suggestive of a homing instinct, but also reveal that snail-throwing can work as a pest management strategy.

Sarcocystosis of animals and humans

USDA-ARS?s Scientific Manuscript database

Species of Sarcocystosis, single-celled protozoan parasites in the Phylum Apicomplexa, are widespread in warm-blooded animals. Completion of the life cycle requires two host species: an intermediate (or prey) host and a definitive (or predator) host. Hosts can harbor more than one species of Sarcocy...

Survival and growth of freshwater pulmonate and nonpulmonate snails in 28-day exposures to copper, ammonia, and pentachlorophenol

USGS Publications Warehouse

Besser, John M.; Dorman, Rebecca A.; Hardesty, Douglas K.; Ingersoll, Christopher G.

2016-01-01

We performed toxicity tests with two species of pulmonate snails (Lymnaea stagnalis and Physa gyrina) and four taxa of nonpulmonate snails in the family Hydrobiidae (Pyrgulopsis robusta,Taylorconcha serpenticola, Fluminicola sp., and Fontigens aldrichi). Snails were maintained in static-renewal or recirculating culture systems with adults removed periodically to isolate cohorts of offspring for toxicity testing. This method successfully produced offspring for both species of pulmonate snails and for two hydrobiid species, P. robusta and Fluminicola sp. Toxicity tests were performed for 28 days with copper, ammonia, and pentachlorophenol in hard reconstituted water with endpoints of survival and growth. Tests were started with 1-week-old L. stagnalis, 2-week-old P. gyrina, 5- to 13-week-old P. robusta and Fluminicola sp., and older juveniles and adults of several hydrobiid species. For all three chemicals, chronic toxicity values for pulmonate snails were consistently greater than those for hydrobiid snails, and hydrobiids were among the most sensitive taxa in species sensitivity distributions for all three chemicals. These results suggest that the toxicant sensitivity of nonpulmonate snails in the family Hydrobiidae would not be adequately represented by results of toxicity testing with pulmonate snails.