Creating an "enabling environment" for taking insecticide treated nets to national scale: the Tanzanian experience

PubMed Central

Magesa, Stephen M; Lengeler, Christian; deSavigny, Don; Miller, Jane E; Njau, Ritha JA; Kramer, Karen; Kitua, Andrew; Mwita, Alex

2005-01-01

Introduction Malaria is the largest cause of health services attendance, hospital admissions and child deaths in Tanzania. At the Abuja Summit in April 2000 Tanzania committed itself to protect 60% of its population at high risk of malaria by 2005. The country is, therefore, determined to ensure that sustainable malaria control using insecticide-treated nets is carried out on a national scale. Case description Tanzania has been involved for two decades in the research process for developing insecticide-treated nets as a malaria control tool, from testing insecticides and net types, to assessing their efficacy and effectiveness, and exploring new ways of distribution. Since 2000, the emphasis has changed from a project approach to that of a concerted multi-stakeholder action for taking insecticide-treated nets to national scale (NATNETS). This means creating conditions that make insecticide-treated nets accessible and affordable to all those at risk of malaria in the country. This paper describes Tanzania's experience in (1) creating an enabling environment for insecticide-treated nets scale-up, (2) promoting the development of a commercial sector for insecticide-treated nets, and (3) targeting pregnant women with highly subsidized insecticide-treated nets through a national voucher scheme. As a result, nearly 2 million insecticide-treated nets and 2.2 million re-treatment kits were distributed in 2004. Conclusion National upscaling of insecticide-treated nets is possible when the programme is well designed, coordinated and supported by committed stakeholders; the Abuja target of protecting 60% of those at high risk is feasible, even for large endemic countries. PMID:16042780

Effect of combining mosquito repellent and insecticide treated net on malaria prevalence in Southern Ethiopia: a cluster-randomised trial.

PubMed

Deressa, Wakgari; Yihdego, Yemane Y; Kebede, Zelalem; Batisso, Esey; Tekalegne, Agonafer; Dagne, Getachew A

2014-03-28

A mosquito repellent has the potential to prevent malaria infection, but there has been few studies demonstrating the effectiveness of combining this strategy with the highly effective long-lasting insecticidal nets (LLINs). This study aimed to determine the effect of combining community-based mosquito repellent with LLINs in the reduction of malaria. A community-based clustered-randomised trial was conducted in 16 rural villages with 1,235 households in southern Ethiopia between September and December of 2008. The villages were randomly assigned to intervention (mosquito repellent and LLINs, eight villages) and control (LLINs alone, eight villages) groups. Households in the intervention villages received mosquito repellent (i.e., Buzz-Off petroleum jelly, essential oil blend) applied every evening. The baseline survey was followed by two follow-up surveys, at one month interval. The primary outcome was detection of Plasmodium falciparum, Plasmodium vivax, or both parasites, through microscopic examination of blood slides. Analysis was by intention to treat. Baseline imbalances and clustering at individual, household and village levels were adjusted using a generalized linear mixed model. 3,078 individuals in intervention and 3,004 in control group were enrolled into the study. Compared with the control arm, the combined use of mosquito repellent and LLINs significantly reduced malaria infection of all types over time [adjusted Odds Ratio (aOR) = 0.66; 95% CI = 0.45-0.97]. Similarly, a substantial reduction in P. falciparum malaria infection during the follow-up surveys was observed in the intervention group (aOR = 0.53, 95% CI = 0.31-0.89). The protective efficacy of using mosquito repellent and LLINs against malaria infection of both P. falciparum/P. vivax and P. falciparum was 34% and 47%, respectively. Daily application of mosquito repellent during the evening followed by the use of LLINs during bedtime at community level has significantly

Willingness to pay for insecticide-treated nets in Berehet District, Amhara Region, Northern Ethiopia: implication of social marketing.

PubMed

Aleme, Adisu; Girma, Eshetu; Fentahun, Netsanet

2014-01-01

Understanding the feasibility of achieving widespread coverage with Insecticide-Treated Nets has to be preceded by learning how people value the Insecticide-Treated Nets and estimating the potential demand and willingness to pay so that sustainability of the intervention can be assured. The objective of this study was to determine willingness to pay for Insecticide-Treated Nets among households in Berehet District, Northern Ethiopia. A community-based cross-sectional study was conducted using both quantitative and qualitative methods in five randomly selected Kebeles from January-February 2012. Open ended contingent valuation technique with follow-up method was used. Qualitative data were collected through focus group discussions and observation methods. Binary logistic regression was used to determine the association between dependent and independent variables. The average number of individuals per Insecticide-Treated Nets was 3.83. Nearly 68.5% persons had willingness to buy Insecticide-Treated Nets if they have access to these Nets. The median maximum price a person is willingness to pay for blue rectangular Insecticide-Treated Net was 20 ETB. People had willingness to pay 30 ETB for blue and white conical insecticide-treated nets. Working on knowledge of malaria (OR=0.68, CI (0.47, 0.98; p<0.05), perceived benefit of Insecticide-Treated Nets (OR=0.28, CI (0.2-0.4; p<0.05), perceived susceptibility (OR=0.64(0.44-0.93; p<0.05) and perceived severity of malaria (OR=0.65(0.47-0.91, p<0.05) had significant association with a willingness to pay Insecticide-Treated Nets. Respondents who prefer Kebele/place/ to buy Insecticide-Treated Net for rectangular shape had a significant association with a willingness to pay for Insecticide-Treated Nets (OR=1.92, CI= 1.07-3.92). Promotions, products, price and place had significant association with willingness to pay for Insecticide-Treated Nets. Designing a social marketing strategy helps ensure sustainable supply of

The Impact of Pyrethroid Resistance on the Efficacy of Insecticide-Treated Bed Nets against African Anopheline Mosquitoes: Systematic Review and Meta-Analysis

PubMed Central

Strode, Clare; Donegan, Sarah; Garner, Paul; Enayati, Ahmad Ali; Hemingway, Janet

2014-01-01

Background Pyrethroid insecticide-treated bed nets (ITNs) help contribute to reducing malaria deaths in Africa, but their efficacy is threatened by insecticide resistance in some malaria mosquito vectors. We therefore assessed the evidence that resistance is attenuating the effect of ITNs on entomological outcomes. Methods and Findings We included laboratory and field studies of African malaria vectors that measured resistance at the time of the study and used World Health Organization–recommended impregnation regimens. We reported mosquito mortality, blood feeding, induced exophily (premature exit of mosquitoes from the hut), deterrence, time to 50% or 95% knock-down, and percentage knock-down at 60 min. Publications were searched from 1 January 1980 to 31 December 2013 using MEDLINE, Cochrane Central Register of Controlled Trials, Science Citation Index Expanded, Social Sciences Citation Index, African Index Medicus, and CAB Abstracts. We stratified studies into three levels of insecticide resistance, and ITNs were compared with untreated bed nets (UTNs) using the risk difference (RD). Heterogeneity was explored visually and statistically. Included were 36 laboratory and 24 field studies, reported in 25 records. Studies tested and reported resistance inconsistently. Based on the meta-analytic results, the difference in mosquito mortality risk for ITNs compared to UTNs was lower in higher resistance categories. However, mortality risk was significantly higher for ITNs compared to UTNs regardless of resistance. For cone tests: low resistance, risk difference (RD) 0.86 (95% CI 0.72 to 1.01); moderate resistance, RD 0.71 (95% CI 0.53 to 0.88); high resistance, RD 0.56 (95% CI 0.17 to 0.95). For tunnel tests: low resistance, RD 0.74 (95% CI 0.61 to 0.87); moderate resistance, RD 0.50 (95% CI 0.40 to 0.60); high resistance, RD 0.39 (95% CI 0.24 to 0.54). For hut studies: low resistance, RD 0.56 (95% CI 0.43 to 0.68); moderate resistance, RD 0.39 (95% CI 0.16 to 0

The impact of pyrethroid resistance on the efficacy of insecticide-treated bed nets against African anopheline mosquitoes: systematic review and meta-analysis.

PubMed

Strode, Clare; Donegan, Sarah; Garner, Paul; Enayati, Ahmad Ali; Hemingway, Janet

2014-03-01

Pyrethroid insecticide-treated bed nets (ITNs) help contribute to reducing malaria deaths in Africa, but their efficacy is threatened by insecticide resistance in some malaria mosquito vectors. We therefore assessed the evidence that resistance is attenuating the effect of ITNs on entomological outcomes. We included laboratory and field studies of African malaria vectors that measured resistance at the time of the study and used World Health Organization-recommended impregnation regimens. We reported mosquito mortality, blood feeding, induced exophily (premature exit of mosquitoes from the hut), deterrence, time to 50% or 95% knock-down, and percentage knock-down at 60 min. Publications were searched from 1 January 1980 to 31 December 2013 using MEDLINE, Cochrane Central Register of Controlled Trials, Science Citation Index Expanded, Social Sciences Citation Index, African Index Medicus, and CAB Abstracts. We stratified studies into three levels of insecticide resistance, and ITNs were compared with untreated bed nets (UTNs) using the risk difference (RD). Heterogeneity was explored visually and statistically. Included were 36 laboratory and 24 field studies, reported in 25 records. Studies tested and reported resistance inconsistently. Based on the meta-analytic results, the difference in mosquito mortality risk for ITNs compared to UTNs was lower in higher resistance categories. However, mortality risk was significantly higher for ITNs compared to UTNs regardless of resistance. For cone tests: low resistance, risk difference (RD) 0.86 (95% CI 0.72 to 1.01); moderate resistance, RD 0.71 (95% CI 0.53 to 0.88); high resistance, RD 0.56 (95% CI 0.17 to 0.95). For tunnel tests: low resistance, RD 0.74 (95% CI 0.61 to 0.87); moderate resistance, RD 0.50 (95% CI 0.40 to 0.60); high resistance, RD 0.39 (95% CI 0.24 to 0.54). For hut studies: low resistance, RD 0.56 (95% CI 0.43 to 0.68); moderate resistance, RD 0.39 (95% CI 0.16 to 0.61); high resistance, RD 0.35 (95% CI

First report of the infection of insecticide-resistant malaria vector mosquitoes with an entomopathogenic fungus under field conditions

PubMed Central

2011-01-01

Background Insecticide-resistant mosquitoes are compromising the ability of current mosquito control tools to control malaria vectors. A proposed new approach for mosquito control is to use entomopathogenic fungi. These fungi have been shown to be lethal to both insecticide-susceptible and insecticide-resistant mosquitoes under laboratory conditions. The goal of this study was to see whether entomopathogenic fungi could be used to infect insecticide-resistant malaria vectors under field conditions, and to see whether the virulence and viability of the fungal conidia decreased after exposure to ambient African field conditions. Methods This study used the fungus Beauveria bassiana to infect the insecticide-resistant malaria vector Anopheles gambiae s.s (Diptera: Culicidae) VKPER laboratory colony strain. Fungal conidia were applied to polyester netting and kept under West African field conditions for varying periods of time. The virulence of the fungal-treated netting was tested 1, 3 and 5 days after net application by exposing An. gambiae s.s. VKPER mosquitoes in WHO cone bioassays carried out under field conditions. In addition, the viability of B. bassiana conidia was measured after up to 20 days exposure to field conditions. Results The results show that B. bassiana infection caused significantly increased mortality with the daily risk of dying being increased by 2.5× for the fungus-exposed mosquitoes compared to the control mosquitoes. However, the virulence of the B. bassiana conidia decreased with increasing time spent exposed to the field conditions, the older the treatment on the net, the lower the fungus-induced mortality rate. This is likely to be due to the climate because laboratory trials found no such decline within the same trial time period. Conidial viability also decreased with increasing exposure to the net and natural abiotic environmental conditions. After 20 days field exposure the conidial viability was 30%, but the viability of control

An elaborated feeding cycle model for reductions in vectorial capacity of night-biting mosquitoes by insecticide-treated nets.

PubMed

Le Menach, Arnaud; Takala, Shannon; McKenzie, F Ellis; Perisse, Andre; Harris, Anthony; Flahault, Antoine; Smith, David L

2007-01-25

Insecticide Treated Nets (ITNs) are an important tool for malaria control. ITNs are effective because they work on several parts of the mosquito feeding cycle, including both adult killing and repelling effects. Using an elaborated description of the classic feeding cycle model, simple formulas have been derived to describe how ITNs change mosquito behaviour and the intensity of malaria transmission, as summarized by vectorial capacity and EIR. The predicted changes are illustrated as a function of the frequency of ITN use for four different vector populations using parameter estimates from the literature. The model demonstrates that ITNs simultaneously reduce mosquitoes' lifespans, lengthen the feeding cycle, and by discouraging human biting divert more bites onto non-human hosts. ITNs can substantially reduce vectorial capacity through small changes to all of these quantities. The total reductions in vectorial capacity differ, moreover, depending on baseline behavior in the absence of ITNs. Reductions in lifespan and vectorial capacity are strongest for vector species with high baseline survival. Anthropophilic and zoophilic species are affected differently by ITNs; the feeding cycle is lengthened more for anthrophilic species, and the proportion of bites that are diverted onto non-human hosts is higher for zoophilic species. This model suggests that the efficacy of ITNs should be measured as a total reduction in transmission intensity, and that the quantitative effects will differ by species and by transmission intensity. At very high rates of ITN use, ITNs can generate large reductions in transmission intensity that could provide very large reductions in transmission intensity, and effective malaria control in some areas, especially when used in combination with other control measures. At high EIR, ITNs will probably not substantially reduce the parasite rate, but when transmission intensity is low, reductions in vectorial capacity combine with reductions in

House screening with insecticide-treated netting provides sustained reductions in domestic populations of Aedes aegypti in Merida, Mexico

PubMed Central

Che-Mendoza, Azael; Medina-Barreiro, Anuar; Koyoc-Cardeña, Edgar; Uc-Puc, Valentín; Contreras-Perera, Yamili; Herrera-Bojórquez, Josué; Dzul-Manzanilla, Felipe; Correa-Morales, Fabian; Ranson, Hilary; Lenhart, Audrey; McCall, Philip J.; Kroeger, Axel; Vazquez-Prokopec, Gonzalo

2018-01-01

Background There is a need for effective methods to control Aedes aegypti and prevent the transmission of dengue, chikungunya, yellow fever and Zika viruses. Insecticide treated screening (ITS) is a promising approach, particularly as it targets adult mosquitoes to reduce human-mosquito contact. Methodology/Principal findings A cluster-randomised controlled trial evaluated the entomological efficacy of ITS based intervention, which consisted of the installation of pyrethroid-impregnated long-lasting insecticide-treated netting material fixed as framed screens on external doors and windows. A total of 10 treatment and 10 control clusters (100 houses/cluster) were distributed throughout the city of Merida, Mexico. Cross-sectional entomological surveys quantified indoor adult mosquito infestation at baseline (pre-intervention) and throughout four post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over two years (2012–2014). A total of 844 households from intervention clusters (86% coverage) were protected with ITS at the start of the trial. Significant reductions in the indoor presence and abundance of Ae. aegypti adults (OR = 0.48 and IRR = 0.45, P<0.05 respectively) and the indoor presence and abundance of Ae. aegypti female mosquitoes (OR = 0.47 and IRR = 0.44, P<0.05 respectively) were detected in intervention clusters compared to controls. This high level of protective effect was sustained for up to 24 months PI. Insecticidal activity of the ITS material declined with time, with ~70% mortality being demonstrated in susceptible mosquito cohorts up to 24 months after installation. Conclusions/Significance The strong and sustained entomological impact observed in this study demonstrates the potential of house screening as a feasible, alternative approach to a sustained long-term impact on household infestations of Ae. aegypti. Larger trials quantifying the effectiveness of ITS on epidemiological endpoints are warranted

Investigating mosquito net durability for malaria control in Tanzania - attrition, bioefficacy, chemistry, degradation and insecticide resistance (ABCDR): study protocol.

PubMed

Lorenz, Lena M; Overgaard, Hans J; Massue, Dennis J; Mageni, Zawadi D; Bradley, John; Moore, Jason D; Mandike, Renata; Kramer, Karen; Kisinza, William; Moore, Sarah J

2014-12-13

Long-Lasting Insecticidal Nets (LLINs) are one of the major malaria vector control tools, with most countries adopting free or subsidised universal coverage campaigns of populations at-risk from malaria. It is essential to understand LLIN durability so that public health policy makers can select the most cost effective nets that last for the longest time, and estimate the optimal timing of repeated distribution campaigns. However, there is limited knowledge from few countries of the durability of LLINs under user conditions. This study investigates LLIN durability in eight districts of Tanzania, selected for their demographic, geographic and ecological representativeness of the country as a whole. We use a two-stage approach: First, LLINs from recent national net campaigns will be evaluated retrospectively in 3,420 households. Those households will receive one of three leading LLIN products at random (Olyset®, PermaNet®2.0 or Netprotect®) and will be followed up for three years in a prospective study to compare their performance under user conditions. LLIN durability will be evaluated by measuring Attrition (the rate at which nets are discarded by households), Bioefficacy (the insecticidal efficacy of the nets measured by knock-down and mortality of mosquitoes), Chemical content (g/kg of insecticide available in net fibres) and physical Degradation (size and location of holes). In addition, we will extend the current national mosquito insecticide Resistance monitoring program to additional districts and use these data sets to provide GIS maps for use in health surveillance and decision making by the National Malaria Control Program (NMCP). The data will be of importance to policy makers and vector control specialists both in Tanzania and the SSA region to inform best practice for the maintenance of high and cost-effective coverage and to maximise current health gains in malaria control.

Optimal insecticide-treated bed-net coverage and malaria treatment in a malaria-HIV co-infection model.

PubMed

Mohammed-Awel, Jemal; Numfor, Eric

2017-03-01

We propose and study a mathematical model for malaria-HIV co-infection transmission and control, in which malaria treatment and insecticide-treated nets are incorporated. The existence of a backward bifurcation is established analytically, and the occurrence of such backward bifurcation is influenced by disease-induced mortality, insecticide-treated bed-net coverage and malaria treatment parameters. To further assess the impact of malaria treatment and insecticide-treated bed-net coverage, we formulate an optimal control problem with malaria treatment and insecticide-treated nets as control functions. Using reasonable parameter values, numerical simulations of the optimal control suggest the possibility of eliminating malaria and reducing HIV prevalence significantly, within a short time horizon.

A Meta-Regression Analysis of the Effectiveness of Mosquito Nets for Malaria Control: The Value of Long-Lasting Insecticide Nets

PubMed Central

Yang, Gi-geun; Pham, Anh

2018-01-01

Long-lasting insecticidal nets (LLINs) have been widely used as an effective alternative to conventional insecticide-treated nets (ITNs) for over a decade. Due to the growing number of field trials and interventions reporting the effectiveness of LLINs in controlling malaria, there is a need to systematically review the literature on LLINs and ITNs to examine the relative effectiveness and characteristics of both insecticide nettings. A systematic review of over 2000 scholarly articles published since the year 2000 was conducted. The odds ratios (ORs) of insecticidal net effectiveness in reducing malaria were recorded. The final dataset included 26 articles for meta-regression analysis, with a sample size of 154 subgroup observations. While there is substantial heterogeneity in study characteristics and effect size, we found that the overall OR for reducing malaria by LLIN use was 0.44 (95% CI = 0.41–0.48, p < 0.01) indicating a risk reduction of 56%, while ITNs were slightly less effective with an OR of 0.59 (95% CI = 0.57–0.61, p <0.01). A meta-regression model confirms that LLINs are significantly more effective than ITNs in the prevention of malaria, when controlling for other covariates. For both types of nets, protective efficacy was greater in high transmission areas when nets were used for an extended period. However, cross-sectional studies may overestimate the effect of the nets. The results surprisingly suggest that nets are less effective in protecting children under the age of five, which may be due to differences in child behavior or inadequate coverage. Compared to a previous meta-analysis, insecticide-treated nets appear to have improved their efficacy despite the risks of insecticide resistance. These findings have practical implications for policymakers seeking effective malaria control strategies. PMID:29562673

Residual mosquito barrier treatments on U.S. military camouflage netting in a southern California desert environment.

PubMed

Britch, Seth C; Linthicum, Kenneth J; Wynn, Wayne W; Walker, Todd W; Farooq, Muhammad; Smith, Vincent L; Robinson, Cathy A; Lothrop, Branka B; Snelling, Melissa; Gutierrez, Arturo; Lothrop, Hugh D

2010-08-01

Treating perimeters of vegetation with residual insecticides for protection from mosquito vectors has potential for U.S. military force health protection. However, for current U.S. military operations in hot-arid environments with little or no vegetation, residual applications on portable artificial materials may be a viable alternative. We evaluated bifenthrin residual treatments of U.S. military camouflage netting under hot-arid field conditions in a desert area in southern California exposed to abundant wild Culex tarsalis mosquitoes. We assessed the ability of the treatment to reduce the numbers of mosquitoes penetrating perimeters of netting and reaching CO2-baited mosquito traps. Treated camouflage netting barriers reduced mosquitoes by > or = 50% for 7-14 days and by 20-35% for 21-28 days compared to untreated barriers. Although reductions may be translated into reductions in risk of exposure to mosquito-borne diseases, we emphasize that barrier treatments should be a component in a suite of insect control measures to be effective.

Host-seeking activity of a Tanzanian population of Anopheles arabiensis at an insecticide treated bed net.

PubMed

Parker, Josephine E A; Angarita Jaimes, Natalia C; Gleave, Katherine; Mashauri, Fabian; Abe, Mayumi; Martine, Jackline; Towers, Catherine E; Towers, David; McCall, Philip J

2017-07-04

Understanding how mosquitoes respond to long lasting insecticide treated nets (LLINs) is fundamental to sustaining the effectiveness of this essential control tool. We report on studies with a tracking system to investigate behaviour of wild anophelines at an LLIN, in an experimental hut at a rural site in Mwanza, Tanzania. Groups of adult female mosquitoes (n = 10 per replicate) reared from larvae of a local population, identified as predominantly (95%) Anopheles arabiensis, were released in the hut. An infrared video tracking system recorded flight and net contact activity over 1 h as the mosquitoes attempted to reach a supine human volunteer within a bed net (either a deltamethrin-treated LLIN or an untreated control net). A range of activities, including flight path, position in relation to the bed net and duration of net contact, were quantified and compared between treatments. The total time that female An. arabiensis spent in flight around LLINs was significantly lower than at untreated nets [F(1,10) = 9.26, p = 0.012], primarily due to a substantial reduction in the time mosquitoes spent in persistent 'bouncing' flight [F(1,10) = 18.48, p = 0.002]. Most activity occurred at the net roof but significantly less so with LLINs (56.8% of total) than untreated nets [85.0%; Χ 2 (15) = 234.69, p < 0.001]. Activity levels at the bed net directly above the host torso were significantly higher with untreated nets (74.2%) than LLINs [38.4%; Χ 2 (15) = 33.54, p = 0.004]. 'Visiting' and 'bouncing' rates were highest above the volunteer's chest in untreated nets (39.9 and 50.4%, respectively) and LLINs [29.9 and 42.4%; Χ 2 (13) = 89.91, p < 0.001; Χ 2 (9) = 45.73, p < 0.001]. Highest resting rates were above the torso in untreated nets [77%; Χ 2 (9) = 63.12, p < 0.001], but in LLINs only 33.2% of resting occurred here [Χ 2 (9) = 27.59, p = 0.001], with resting times spread between the short vertical side of the net adjacent to the

Inequalities in purchase of mosquito nets and willingness to pay for insecticide-treated nets in Nigeria: Challenges for malaria control interventions

PubMed Central

Onwujekwe, Obinna; Hanson, Kara; Fox-Rushby, Julia

2004-01-01

Objective To explore the equity implications of insecticide-treated nets (ITN) distribution programmes that are based on user charges. Methods A questionnaire was used to collect information on previous purchase of untreated nets and hypothetical willingness to pay (WTP) for ITNs from a random sample of householders. A second survey was conducted one month later to collect information on actual purchases of ITNs. An economic status index was used for characterizing inequity. Major findings The lower economic status quintiles were less likely to have previously purchased untreated nets and also had a lower hypothetical and actual WTP for ITNs. Conclusion ITN distribution programmes need to take account of the diversity in WTP for ITNs if they are to ensure equity in access to the nets. This could form part of the overall poverty reduction strategy. PMID:15023234

Insecticide-treated nets provide protection against malaria to children in an area of insecticide resistance in Southern Benin.

PubMed

Bradley, John; Ogouyèmi-Hounto, Aurore; Cornélie, Sylvie; Fassinou, Jacob; de Tove, Yolande Sissinto Savi; Adéothy, Adicath Adéola; Tokponnon, Filémon T; Makoutode, Patrick; Adechoubou, Alioun; Legba, Thibaut; Houansou, Telesphore; Kinde-Gazard, Dorothée; Akogbeto, Martin C; Massougbodji, Achille; Knox, Tessa Bellamy; Donnelly, Martin; Kleinschmidt, Immo

2017-05-26

Malaria control is heavily reliant on insecticides, especially pyrethroids. Resistance of mosquitoes to insecticides may threaten the effectiveness of insecticide-based vector control and lead to a resurgence of malaria in Africa. In 21 villages in Southern Benin with high levels of insecticide resistance, the resistance status of local vectors was measured at the same time as the prevalence of malaria infection in resident children. Children who used LLINs had lower levels of malaria infection [odds ratio = 0.76 (95% CI 0.59, 0.98, p = 0.033)]. There was no evidence that the effectiveness of nets was different in high and low resistance locations (p = 0.513). There was no association between village level resistance and village level malaria prevalence (p = 0.999). LLINs continue to offer individual protection against malaria infection in an area of high resistance. Insecticide resistance is not a reason to stop efforts to increase coverage of LLINs in Africa.

Insecticide-treated mosquito nets in rural Burkina Faso: assessment of coverage and equity in the wake of a universal distribution campaign.

PubMed

Zöllner, Caroline; De Allegri, Manuela; Louis, Valérie R; Yé, Maurice; Sié, Ali; Tiendrebéogo, Justin; Jahn, Albrecht; Müller, Olaf

2015-03-01

Insecticide-treated mosquito nets (ITNs) are an essential tool of the Roll Back Malaria strategy. An increasing number of African countries have embarked on mass distribution campaigns of long-lasting insecticide-treated nets (LLINs) with the ultimate goal of universal coverage. Such a national campaign with the goal of one ITN for every two people has been conducted in Burkina Faso in 2010. Our aim was to assess the coverage and equity effect of the universal distribution campaign of LLINs in Burkina Faso and to identify determinants of ITN ownership across households after the campaign. We evaluated its effects through comparison of data from two household surveys conducted in early 2010 (before the campaign) and early 2011 (after the campaign) on a representative rural district in north-western Burkina Faso. Data were collected on household characteristics (including socio-economic status) and ITN ownership. We used concentration curves and indices to compare ITN coverage indicators before and after the campaign and multilevel multivariate logistic regression to estimate factors associated with achievement of the universal coverage target in 2011. The survey included 1106 households in 2010 and 1094 in 2011. We found that the proportion of households with at least one ITN increased from 59% before the campaign to 99% afterwards, whereas the concentration index dropped from 0.087 (standard error (SE): 0.014) to 0.002 (SE: 0.002). Fifty-two per cent of households reached the target of one ITN for every two people per household, with the relevant concentration index at -0.031 (SE: 0.016). Eighty-six per cent of households owned at least one ITN for every three people. The main characteristics significantly associated with the targeted intra-household coverage were family size and distance to the health centre but not socio-economic status. In conclusion, despite not having fully met its target, the national LLIN campaign achieved a high level of coverage and

Efficacy of mosquito netting for sustainable small holders' cabbage production in Africa.

PubMed

Martin, T; Assogba-Komlan, F; Houndete, T; Hougard, J M; Chandre, F

2006-04-01

The efficacy of a mosquito netting to protect cabbages, Brassica oleracea L., against pests was investigated in field trials in Benin, West Africa. A polyester net covered the plants at night by using a wood armature. The net was removed during the day to prevent overheating and excessive shade, both problems of insect-proof screens used under tropical conditions. The number of all lepidopteran larvae with netting protection and foliar insecticide sprays was significantly lower than the unprotected control. The number of diamondback moth, Plutella xylostella (L.), was significantly lower with netting protection compared with foliar insecticide sprays and control. Netting treated with deltamethrin gave total protection of young plants against the aphid Lipaphis erysimi (Kaltenbach). At harvest, the number of marketable cabbages protected with untreated netting was significantly higher compared with the production with foliar insecticide sprays. The protection of cabbages with netting can be an economically viable method. Considering the price of cabbages on local markets (US dollars 1/unit), the net returns per 100 m2 were US dollars 247 by using netting, US dollars 149 by using insecticides, and US dollars 117 for controls. The net returns for using netting are based on replacing the netting each crop cycle. But netting can be reused several times, depending upon conditions, increasing the profit margin. The netting protection may be an alternative to the growing unsustainable practices of vegetable cropping in peri-urban areas of tropical countries.

Combining indoor and outdoor methods for controlling malaria vectors: an ecological model of endectocide-treated livestock and insecticidal bed nets.

PubMed

Yakob, Laith; Cameron, Mary; Lines, Jo

2017-03-13

Malaria is spread by mosquitoes that are increasingly recognised to have diverse biting behaviours. How a mosquito in a specific environment responds to differing availability of blood-host species is largely unknown and yet critical to vector control efficacy. A parsimonious mathematical model is proposed that accounts for a diverse range of host-biting behaviours and assesses their impact on combining long-lasting insecticidal nets (LLINs) with a novel approach to malaria control: livestock treated with insecticidal compounds ('endectocides') that kill biting mosquitoes. Simulations of a malaria control programme showed marked differences across biting ecologies in the efficacy of both LLINs as a stand-alone tool and the combination of LLINs with endectocide-treated cattle. During the intervals between LLIN mass campaigns, concordant use of endectocides is projected to reduce the bounce-back in malaria prevalence that can occur as LLIN efficacy decays over time, especially if replacement campaigns are delayed. Integrating these approaches can also dramatically improve the attainability of local elimination; endectocidal treatment schedules required to achieve this aim are provided for malaria vectors with different biting ecologies. Targeting blood-feeding mosquitoes by treating livestock with endectocides offers a potentially useful complement to existing malaria control programmes centred on LLIN distribution. This approach is likely to be effective against vectors with a wide range of host-preferences and biting behaviours, with the exception of species that are so strictly anthropophilic that most blood meals are taken on humans even when humans are much less available than non-human hosts. Identifying this functional relationship in wild mosquito populations and ascertaining the extent to which it differs, within as well as between species, is a critical next step before targets can be set for employing this novel approach and combination.

The paradigm of eave tubes: scaling up house improvement and optimizing insecticide delivery against disease-transmitting mosquitoes.

PubMed

Okumu, Fredros

2017-05-19

Control of mosquito-borne diseases is greatly compromised by spread of insecticide resistance, high implementation costs and sub-optimal compliance among users. Improved housing has potential to reduce malaria transmission nearly as much as long-lasting insecticide-treated nets (LLINs), while also preventing other arthropod-borne diseases and improving overall well-being. Yet, it is hardly promoted as mainstream intervention, partly because of high costs, minimal communal benefits to people in non-improved houses, and low scalability. By exploiting biological observations of mosquito behaviours around dwellings, scientists have developed a new approach that integrates effective vector control into housing developments. The technique involves blocking eave spaces in local houses, leaving a few cylindrical holes into which plastic tubes with insecticide-laden electrostatic nettings are inserted. Where houses already have blocked eaves, these cylindrical holes are drilled and the tubes inserted. The eave tube technology, as it is called, is an innovative new approach for implementing housing improvements, by creating a new scalable product that can be integrated in houses during or after construction. It takes away insecticides from proximity of users, and instead puts them where mosquitoes are most likely to enter houses, thereby reducing insecticidal exposure among household occupants, while maximizing exposure of mosquitoes. This way, lower quantities of insecticides are used, better house ventilation achieved, intervention costs reduced, and mass communal benefits achieved even were vectors are resistant to similar insecticides when delivered conventionally. There are however still some critical pieces missing, notably epidemiological, social and economic evidence that the above assertions are true and sustainable. Besides, there also some technical limitations to be considered, namely: (1) need for extensive house modifications before eave tubes are inserted, (2

Efficacy of long-lasting insecticidal nets in use in Macha, Zambia, against the local Anopheles arabiensis population.

PubMed

Norris, Laura C; Norris, Douglas E

2011-08-31

The mosquito Anopheles arabiensis is the primary vector of Plasmodium falciparum in Macha, Zambia. A major portion of Zambia's current malaria control programme relies on long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) with insecticides. Currently, the efficacy of these measures against An. arabiensis in Macha is unknown, and previous data has shown that An. arabiensis has continued to feed on human hosts, despite high ITN coverage. It is possible that this could be due to either decreased efficacy of ITNs in used in Macha, or pyrethroid resistance in the vector. F1 offspring of field-collected adult An. arabiensis were tested for insecticide resistance, using CDC bottle bioassays and deltamethrin ITN susceptibility assays. The mosquitoes were characterized for the knock-down resistance (kdr) allele by PCR. LLINs that had been in use for two years in nearby villages were collected and tested for residual deltamethrin concentration and net quality, and were used in bioassays against susceptible colonized Anopheles gambiae s.s. Keele. Additionally, a survey on ITN use and care was conducted among LLIN owners. In the F1 An. arabiensis field population, low levels of resistance to DDT and deltamethrin-treated net material were detected by bioassay, although the knock-down resistance (kdr) allele not present in the population. ITN evaluations revealed high variability in residual deltamethrin concentration, quality of the nets, and mosquito mortality in bioassays. Mortality against An. gambiae s.s. in bioassays was correlated with residual deltamethrin concentration, which was dependent upon the number of washes each net had received. Proper LLIN care was a strong determinant of LLIN efficacy, indicating that education on the importance of LLIN use and care is key when distributing nets. As there is little insecticide resistance in the local vector population, degradation of LLINs most likely allowed for continued human feeding by An

Prevention of malaria with pyrethroid treated bednets.

PubMed

Curtis, C

1997-01-01

Malaria parasites (Plasmodium) are carried from person to person by female mosquitoes of the genus Anopheles. 80-90% of malaria incidence worldwide occurs in Africa. The main Anopheles species in Africa which bite humans are A. gambiae and A. funestus. Since these animals feed upon humans mainly during late night when most people are in bed, the consistent use of bednets can block the transmission of malaria. However, bednets should be treated with synthetic pyrethroid insecticides, for the physical barrier of bednets is often inadequate to prevent the entry of Anopheles. In addition, the mosquitoes are drawn to the bednets by the carbon dioxide and body odor emitted by the occupant. The insecticide-treated nets therefore double as mosquito traps. Bednets are treated by dipping them into an aqueous emulsion of a pyrethroid, wringing them out, then laying them out to dry. A considerable number of mosquitoes can be killed with a relatively small amount of insecticide. A treated net's insecticidal power can be tested by wrapping part of it around a wire frame, then introducing some Anopheles mosquitoes inside the frame. A median mosquito knockdown time of less than 10 minutes inside the net indicates a good pyrethroid deposit. The persistence of a net's insecticidal power is considerably reduced if the net is vigorously washed. People vary in the frequency they wash their nets. Most villagers in Tanzania were found to wash and retreat their nets every 6 months.

Bio-efficacy, physical integrity, community usage and washing practices of mosquito nets treated with ICON MAXX long-lasting insecticidal treatment in India

PubMed Central

Sahu, Sudhansu Sekhar; Gunasekaran, Kasinathan; Vijayakumar, Kilakootil Narayanan; Jambulingam, Purushothaman

2017-01-01

BACKGROUND New brands of potential long lasting insecticide nets (LLINs) and LLIN treatment kits require field evaluation before they are used in a vector control programme. OBJECTIVES The aim of this study was to evaluate the bio-efficacy, usage, washing practice and physical integrity of nets treated with LLIN treatment kit, ICON MAXX in a phase III field trial in Odisha state, India. METHODS A total of 300 polyester nets treated with ICON MAXX and 140 polyester nets treated conventionally with lambda-cyhalothrin CS 2.5% ITNs were distributed. The bio-efficacy was evaluated with WHO cone bioassay. The chemical analysis of netting pieces was done at the beginning, after 12 and 36 months of the trial. FINDINGS After one year of distribution of nets, the bioassay showed 100% mortality on both ITNs and ICON MAXX treated nets. At 36 months, the overall pass rate was 58.8% and the mean lambda-cyhalothrin content of LLINs was 34.5 mg ai/m2, showing a loss of 44.4% of the original concentration. CONCLUSION ICON MAXX treated LLIN was found to retain bio-efficacy causing 97% knockdown of Anopheles stephensi up to 30 months and met the WHOPES criteria. However, the desired bio-efficacy was not sustained up to 36 months. PMID:28125134

Long-term field performance of a polyester-based long-lasting insecticidal mosquito net in rural Uganda

PubMed Central

Kilian, Albert; Byamukama, Wilson; Pigeon, Olivier; Atieli, Francis; Duchon, Stephan; Phan, Chi

2008-01-01

Background In order to evaluate whether criteria for LLIN field performance (phase III) set by the WHO Pesticide Evaluation Scheme are met, first and second generations of one of these products, PermaNet®, a polyester net using the coating technology were tested. Methods A randomized, double blinded study design was used comparing LLIN to conventionally treated nets and following LLIN for three years under regular household use in rural conditions. Primary outcome measures were deltamethrin residue and bioassay performance (60 minute knock-down and 24 hour mortality after a three minute exposure) using a strain of Anopheles gambiae s.s. sensitive to pyrethroid insecticides. Results Baseline concentration of deltamethrin was within targets for all net types but was rapidly lost in conventionally treated nets and first generation PermaNet® with median of 0.7 and 2.5 mg/m2 after six months respectively. In contrast, second generation PermaNet® retained insecticide well and had 41.5% of baseline dose after 36 months (28.7 mg/m2). Similarly, vector mortality and knockdown dropped to 18% and 70% respectively for first generation LLIN after six months but remained high (88.5% and 97.8% respectively) for second generation PermaNet® after 36 months of follow up at which time 90.0% of nets had either a knockdown rate ≥ 95% or mortality rate ≥ 80%. Conclusion Second generation PermaNet® showed excellent results after three years of field use and fulfilled the WHOPES criteria for LLIN. Loss of insecticide on LLIN using coating technology under field conditions was far more influenced by factors associated with handling rather than washing. PMID:18355408

Evaluation of Polyethylene-Based Long Lasting Treated Bed Net Netprotect on Anopheles Mosquitoes, Malaria Incidence, and Net Longivity in Western Kenya

PubMed Central

Odhiambo, M. T. O.; Skovmand, O.; Vulule, J. M.; Kokwaro, E. D.

2013-01-01

We studied the effect on malaria incidence, mosquito abundance, net efficacy, net use rate, chemical analysis, and holes of a long lasting insecticide treated bed net (Netprotect) in western Kenya, 2007–2010. Nets were hung in 150 households 6 months before they were hung in a second, 2 km away. Indoor resting densities were monitored by pyrethrum spray catch and malaria cases by passive detection using clinical manifestations and rapid diagnostic test. The probability of finding An. arabiensis in the control area was 2.6 times higher than that in intervention area during the first 6 months. Human blood feeding index of Anopheles funestus declined 17%. After bed nets were hung in the second area, malaria incidence declined 25% down to the level in the first area. Incidence remained at this low level for 2 years. 90% of collected nets were efficacious after 3-year use. Deltamethrin dosage declined from 1.9 to 0.5 g/kg over 3 years. Attrition rate after 3 years was 21%. WHO hole index changed from 333 to 114 to 381 over the three years. This index summarizes the numbers of holes in size categories and multiplies with the mean hole area per category. It is very sensitive to the impact of big holes in a few nets. PMID:24194770

The use and misuse of mass distributed free insecticide-treated bed nets in a semi-urban community in Rivers State, Nigeria.

PubMed

Ordinioha, Best

2012-01-01

Insecticide-treated bed net (ITN) is currently distributed free of charge to vulnerable groups in Nigeria, for malaria control. Consistent use of the nets is required for maximum effectiveness; but studies indicate that the nets are often jettisoned in periods of low mosquito activity and high night time temperature. The objective of this study has been to assess the use of mass distributed nets in a semi-urban community in Rivers State, south-south Nigeria, during the late dry season, when mosquito activity is at the lowest in the community. The study was carried out in Ishiodu - Emohua, using a cross-sectional study design. The data was collected using a structured, interviewer-administered questionnaire, administered to female head of households in the community, with under-five children. A total of 170 respondents were studied; they had an average age of 34.3 ± 7.6 years, most were married (86.5%), and had secondary school education (68.2%). All the households owned at least one ITN, and an average of 1.7 nets, with 75.3% of the households owning two or more ITNs. Almost all the nets (99.4%) were obtained free of charge. Of the 170 households that received the nets, 71.8% had hanged the nets as at the time of the survey; 83.6% of these hanged the nets over a bed, while 10.7% used the nets as window curtain. Of the 102 ITNs that were properly deployed, only 27.5% were occupied the night before the survey, by an average of 2.5 persons, mainly under-five children (37.7%). The distribution of free ITNs has resulted in universal household ownership, but the use of the nets is still very poor. Proper health education is required to encourage the consistent use of the nets, even in hot night, with low mosquito activity.

Potential benefits of combining transfluthrin-treated sisal products and long-lasting insecticidal nets for controlling indoor-biting malaria vectors.

PubMed

Masalu, John P; Okumu, Fredros O; Mmbando, Arnold S; Sikulu-Lord, Maggy T; Ogoma, Sheila B

2018-04-10

Transfluthrin vapour prevents mosquito bites by disrupting their host-seeking behaviors. We measured the additional benefits of combining transfluthrin-treated sisal decorations and long-lasting insecticidal nets (LLINs) with an aim of extending protection against early evening, indoor-biting malaria vectors when LLINs are ineffective. We investigated the indoor protective efficacy of locally made sisal decorative baskets (0.28 m 2 ) treated with 2.5 ml and 5.0 ml transfluthrin, in terms of mosquito density, exposure to bites and 24 h mortality. Experiments were conducted in experimental huts, located in Lupiro village, Ulanga District, south-eastern Tanzania. Human landing catches (HLC) were used to measure exposure to bites between 19:00-23:00 h. Each morning, at 06:00 h, mosquitoes were collected inside huts and in exit traps and monitored for 24 h mortality. Sisal decorative baskets (0.28 m 2 ) treated with 2.5 ml and 5.0 ml transfluthrin deterred three-quarters of Anopheles arabiensis mosquitoes from entering huts (relative rate, RR = 0.26, 95% confidence interval, CI: 0.20-0.34, P < 0.001 and RR= 0.29, 95% CI: 0.22-0.37, P < 0.001, respectively). Both treatments induced a 10-fold increase in 24 h mortality of An. arabiensis mosquitoes (odds ratio, OR = 12.26, 95% CI: 7.70-19.51, P < 0.001 and OR = 18.42, 95% CI: 11.36-29.90, P < 0.001, respectively). Sisal decorative items treated with spatial repellents provide additional household and personal protection against indoor biting malaria and nuisance mosquitoes in the early evening, when conventional indoor vector control tools, such as LLINs, are not in use. We recommend future studies to investigate the epidemiological relevance of combining LLINs and transfluthrin decorated baskets in terms of their effect on reduction in malaria prevalence.

INSECTICIDE-TREATED BED NETS IN RONDÔNIA, BRAZIL: EVALUATION OF THEIR IMPACT ON MALARIA CONTROL

PubMed Central

Vieira, Gabriel de Deus; Basano, Sergio de Almeida; Katsuragawa, Tony Hiroshi; Camargo, Luís Marcelo Aranha

2014-01-01

Mosquito nets treated with long-lasting insecticide (LLINs), when used in compliance with guidelines of the World Health Organization, may be effective for malaria vector control. In 2012, approximately 150,000 LLINs were installed in nine municipalities in the state of Rondônia. However, no studies have assessed their impact on the reduction of malaria incidence. This study analyzed secondary data of malaria incidence, in order to assess the impact of LLINs on the annual parasite incidence (API). The results showed no statistically significant differences in API one year after LLIN installation when compared to municipalities without LLINs. The adoption of measures for malaria vector control should be associated with epidemiological studies and evaluations of their use and efficiency, with the aim of offering convincing advantages that justify their implementation and limit malaria infection in the Amazon Region. PMID:25351543

Field efficacy of pyrethroid treated plastic sheeting (durable lining) in combination with long lasting insecticidal nets against malaria vectors

PubMed Central

2010-01-01

Background Insecticide treated plastic sheeting (ITPS), sometimes known as durable lining, has potential as a long-lasting insecticidal surface for malaria vector control when used as lining for interior walls and ceilings inside the home. Against a backdrop of increasing long lasting net (LN) coverage, we examined the effect of combining permethrin-treated plastic sheeting (ITPS) with LNs in Burkina Faso. Methods A verandah trap experimental hut trial of ITPS with or without Olyset LN was conducted in the Vallée du Kou near Bobo-Dioulasso, where the two molecular forms of Anopheles gambiae s.s., S (frequency 65%) and M (frequency 35%), occur. The S form is mostly pyrethroid resistant (Fkdr = 92%) owing to the kdr mechanism, and the M form is mostly kdr susceptible (Fkdr = 7%). The treatment arms included ITPS, Olyset, ITPS plus Olyset, ITPS plus untreated net (with or without holes), and untreated control. Results ITPS was significantly inferior to Olyset LN in terms of mortality (37% vs 63%), blood feeding inhibition (20% vs 81%) and deterrence (0 vs 42%) effects, and hence altogether inferior as a means of personal protection (16% vs 89%). The addition of ITPS to Olyset did not improve mortality (62%), blood feeding inhibition (75%), deterrence (50%) or personal protection (88%) over that of Olyset used alone. Use of untreated nets - both holed and intact - with ITPS provided greater protection from blood-feeding. The intact net/ITPS combination killed more mosquitoes than ITPS on its own. Conclusions Although ITPS has a potential role for community control of malaria, at low coverage it is unlikely to be as good as Olyset LNs for household protection. The combination of pyrethroid IRS and pyrethroid LN - as practiced in some countries - is unlikely to be additive except, perhaps, at high levels of IRS coverage. A combination of LN and ITPS treated with an alternative insecticide is likely to be more effective, particularly in areas of pyrethroid resistance

Field efficacy of pyrethroid treated plastic sheeting (durable lining) in combination with long lasting insecticidal nets against malaria vectors.

PubMed

Chandre, Fabrice; Dabire, Roch K; Hougard, Jean-Marc; Djogbenou, Luc S; Irish, Seth R; Rowland, Mark; N'guessan, Raphael

2010-08-03

Insecticide treated plastic sheeting (ITPS), sometimes known as durable lining, has potential as a long-lasting insecticidal surface for malaria vector control when used as lining for interior walls and ceilings inside the home. Against a backdrop of increasing long lasting net (LN) coverage, we examined the effect of combining permethrin-treated plastic sheeting (ITPS) with LNs in Burkina Faso. A verandah trap experimental hut trial of ITPS with or without Olyset LN was conducted in the Vallée du Kou near Bobo-Dioulasso, where the two molecular forms of Anopheles gambiae s.s., S (frequency 65%) and M (frequency 35%), occur. The S form is mostly pyrethroid resistant (Fkdr = 92%) owing to the kdr mechanism, and the M form is mostly kdr susceptible (Fkdr = 7%). The treatment arms included ITPS, Olyset, ITPS plus Olyset, ITPS plus untreated net (with or without holes), and untreated control. ITPS was significantly inferior to Olyset LN in terms of mortality (37% vs 63%), blood feeding inhibition (20% vs 81%) and deterrence (0 vs 42%) effects, and hence altogether inferior as a means of personal protection (16% vs 89%). The addition of ITPS to Olyset did not improve mortality (62%), blood feeding inhibition (75%), deterrence (50%) or personal protection (88%) over that of Olyset used alone. Use of untreated nets - both holed and intact - with ITPS provided greater protection from blood-feeding. The intact net/ITPS combination killed more mosquitoes than ITPS on its own. Although ITPS has a potential role for community control of malaria, at low coverage it is unlikely to be as good as Olyset LNs for household protection. The combination of pyrethroid IRS and pyrethroid LN - as practiced in some countries - is unlikely to be additive except, perhaps, at high levels of IRS coverage. A combination of LN and ITPS treated with an alternative insecticide is likely to be more effective, particularly in areas of pyrethroid resistance.

Heterogeneity and changes in inequality of malaria risk after introduction of insecticide-treated bed nets in Macha, Zambia.

PubMed

Norris, Laura C; Norris, Douglas E

2013-04-01

In 2007, the first free mass distribution of insecticide-treated bed nets (ITNs) occurred in southern Zambia. To determine the effect of ITNs on heterogeneity in biting rates, human DNA from Anopheles arabiensis blood meals was genotyped to determine the number of hosts that had contributed to the blood meals. The multiple feeding rate decreased from 18.9% pre-ITN to 9.1% post-ITN, suggesting that mosquito biting had focused onto a smaller fraction of the population. Pre-ITN, 20% of persons in a household provided 40% of blood meals, which increased to 59% post-ITN. To measure heterogeneity over a larger scale, mosquitoes were collected in 90 households in two village areas. Of these households, 25% contributed 78.1% of An. arabiensis, and households with high frequencies of An. arabiensis were significantly spatially clustered. The results indicate that substantial heterogeneity in malaria risk exists at local and household levels, and household-level heterogeneity may be influenced by interventions, such as ITNs.

Cost-effectiveness of social marketing of insecticide-treated nets for malaria control in the United Republic of Tanzania.

PubMed Central

Hanson, Kara; Kikumbih, Nassor; Armstrong Schellenberg, Joanna; Mponda, Haji; Nathan, Rose; Lake, Sally; Mills, Anne; Tanner, Marcel; Lengeler, Christian

2003-01-01

OBJECTIVE: To assess the costs and consequences of a social marketing approach to malaria control in children by means of insecticide-treated nets in two rural districts of the United Republic of Tanzania, compared with no net use. METHODS: Project cost data were collected prospectively from accounting records. Community effectiveness was estimated on the basis of a nested case-control study and a cross-sectional cluster sample survey. FINDINGS: The social marketing approach to the distribution of insecticide-treated nets was estimated to cost 1560 US dollars per death averted and 57 US dollars per disability-adjusted life year averted. These figures fell to 1018 US dollars and 37 US dollars, respectively, when the costs and consequences of untreated nets were taken into account. CONCLUSION: The social marketing of insecticide-treated nets is an attractive intervention for preventing childhood deaths from malaria. PMID:12764493

A qualitative study on the acceptability and preference of three types of long-lasting insecticide-treated bed nets in Solomon Islands: implications for malaria elimination

PubMed Central

Atkinson, Jo-An; Bobogare, Albino; Fitzgerald, Lisa; Boaz, Leonard; Appleyard, Bridget; Toaliu, Hilson; Vallely, Andrew

2009-01-01

Background In March 2008, the Solomon Islands and Vanuatu governments raised the goal of their National Malaria Programmes from control to elimination. Vector control measures, such as indoor residual spraying (IRS) and long-lasting insecticidal bed nets (LLINs) are key integral components of this programme. Compliance with these interventions is dependent on their acceptability and on the socio-cultural context of the local population. These factors need to be investigated locally prior to programme implementation. Method Twelve focus group discussions (FGDs) were carried out in Malaita and Temotu Provinces, Solomon Islands in 2008. These discussions explored user perceptions of acceptability and preference for three brands of long-lasting insecticide-treated bed nets (LLINs) and identified a number of barriers to their proper and consistent use. Results Mosquito nuisance and perceived threat of malaria were the main determinants of bed net use. Knowledge of malaria and the means to prevent it were not sufficient to guarantee compliance with LLIN use. Factors such as climate, work and evening social activities impact on the use of bed nets, particularly in men. LLIN acceptability plays a varying role in compliance with their use in villages involved in this study. Participants in areas of reported high and year round mosquito nuisance and perceived threat of malaria reported LLIN use regardless of any reported unfavourable characteristics. Those in areas of low or seasonal mosquito nuisance were more likely to describe the unfavourable characteristics of LLINs as reasons for their intermittent or non-compliance. The main criterion for LLIN brand acceptability was effectiveness in preventing mosquito bites and malaria. Discussions highlighted considerable confusion around LLIN care and washing which may be impacting on their effectiveness and reducing their acceptability in Solomon Islands. Conclusion Providing LLINs that are acceptable will be more important for

Challenges in universal coverage and utilization of insecticide-treated bed nets in migrant plantation workers in Myanmar

PubMed Central

2014-01-01

Background High coverage of the bed nets can reduce mortality and morbidity of mosquito-borne diseases including malaria. Although the migrant workers are at high risk of malaria, there are many hidden challenges in universal coverage and utilization of the insecticide-treated nets (ITNs) in this populations. Methods Cross sectional study was conducted in 170 migrant workers in palm oil plantation sites in Tanintharyi Region and 175 in rubber plantation sites in Mon State. A multistage stratified cluster sampling was applied to select the participants. During household visit, face-to-face interviews using structured pre-coded, pre tested questionnaires and direct observation on installation of the bed nets was conducted. Two focus group discussions in each site were done by sample stratified purposive sampling method mainly focused on effective utilization of bed nets. Results Among them, 332 (96.2%) had a bed net and 284 (82.3%) had an ITN, while 204 (59.1%) had unused extranets. Among the ITNs users, 28.9% reported problems including insecticide smell (56.9%), dizziness (20.2%), headache (12.8%) and itchiness (9.2%). More than 75% received ITNs from health authorities and NGOs free-of-charge. More than 70% wanted to buy a net but they were unaffordable for 64% of them. On observation, only five families could show no bed net, but 80% showed 1–3 ITNs. Consistent utilization in all seasons was noted in 189 (53.1%), that was higher in palm oil plantation than rubber plantation workers (p = 0.0001) due to the nature of the work at night. Perceived malaria risk was also significantly higher ITNs consistent users than non-users (p = 0.0004) and better willingness to buy an ITN by themselves (p = 0.0005). They said that effectiveness of the ITNs was reduced after 6 months and 2–3 times washing. They wished to receive more durable smooth nets with small holes in lace. Misuses of the ITNs such as use the nets for animals and fishing, were also noted

Mosquito repellents for malaria prevention

PubMed Central

Maia, Marta F; Kliner, Merav; Richardson, Marty; Lengeler, Christian; Moore, Sarah J

2018-01-01

Background Malaria is an important cause of illness and death across endemic regions. Considerable success against malaria has been achieved within the past decade mainly through long-lasting insecticide-treated nets (LLINs). However, elimination of the disease is proving difficult as current control methods do not protect against mosquitoes biting outdoors and when people are active. Repellents may provide a personal protection solution during these times. Objectives To assess the impact of topical repellents, insecticide-treated clothing, and spatial repellents on malaria transmission. Search methods We searched the following databases up to 26 June 2017: the Cochrane Infectious Diseases Group Specialized Register; the Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE; Embase; US AFPMB; CAB Abstracts; and LILACS. We also searched trial registration platforms and conference proceedings; and contacted organizations and companies for ongoing and unpublished trials. Selection criteria We included randomized controlled trials (RCTs) and cluster-randomized controlled trials of topical repellents proven to repel mosquitoes; permethrin-treated clothing; and spatial repellents such as mosquito coils. We included trials that investigated the use of repellents with or without LLINs, referred to as insecticide-treated nets. Data collection and analysis Two review authors independently reviewed trials for inclusion, extracted the data, and assessed the risk of bias. A third review author resolved any discrepancies. We analysed data by conducting meta-analysis and stratified by whether the trials had included LLINs. We combined results from cRCTs with individually RCTs by adjusting for clustering and presented results using forest plots. We used GRADE to assess the certainty of the evidence. Main results Eight cRCTs and two RCTs met the inclusion criteria. Six trials investigated topical repellents, two trials investigated insecticide-treated

How many holes is too many? A prototype tool for estimating mosquito entry risk into damaged bed nets.

PubMed

Sutcliffe, James; Ji, Xin; Yin, Shaoman

2017-08-01

Insecticide-treated bed nets (ITNs) have played an integral role in malaria reduction but how insecticide depletion and accumulating physical damage affect ITN performance is poorly understood. More accurate methods are needed to assess damage to bed nets so that they can be designed, deployed and replaced optimally. Video recordings of female Anopheles gambiae in near approach (1-½ cm) to occupied untreated rectangular bed nets in a laboratory study were used to quantify the amount of mosquito activity (appearances over time) around different parts of the net, the per-appearance probability of a mosquito coming close to holes of different sizes (hole encounter) and the per-encounter probability of mosquitoes passing through holes of different sizes (hole passage). Appearance frequency on different parts of the net reflected previously reported patterns: the area of the net under greatest mosquito pressure was the roof, followed by the bottom 30 cm of the sides, followed by the 30 cm area immediately above this, followed by the upper two-thirds of the sides. The ratio of activity in these areas was (respectively) 250:33:5:1. Per-appearance probability of hole encounter on all parts of the net was strongly predicted by a factor combining hole perimeter and area. Per-encounter probability of hole passage, in turn, was strongly predicted by hole width. For a given width, there was a 20% greater risk of passage through holes on the roof than holes on the sides. Appearance, encounter and passage predictors correspond to various mosquito behaviours that have previously been described and are combined into a prototype mosquito entry risk tool that predicts mosquito entry rates for nets with various amounts of damage. Scenarios that use the entry risk tool to test the recommendations of the WHOPES proportionate hole index (pHI) suggest that the pHI hole size categories and failure to account for hole location likely sometimes lead to incorrect conclusions about net

Clustering of host-seeking activity of Anopheles gambiae mosquitoes at the top surface of a human-baited bed net

PubMed Central

2013-01-01

Background Knowledge of the interactions between mosquitoes and humans, and how vector control interventions affect them, is sparse. A study exploring host-seeking behaviour at a human-occupied bed net, a key event in such interactions, is reported here. Methods Host-seeking female Anopheles gambiae activity was studied using a human-baited ‘sticky-net’ (a bed net without insecticide, coated with non-setting adhesive) to trap mosquitoes. The numbers and distribution of mosquitoes captured on each surface of the bed net were recorded and analysed using non-parametric statistical methods and random effects regression analysis. To confirm sticky-net reliability, the experiment was repeated using a pitched sticky-net (tilted sides converging at apex, i.e., neither horizontal nor vertical). The capture efficiency of horizontal and vertical sticky surfaces were compared, and the potential repellency of the adhesive was investigated. Results In a semi-field experiment, more mosquitoes were caught on the top (74-87%) than on the sides of the net (p < 0.001). In laboratory experiments, more mosquitoes were caught on the top than on the sides in human-baited tests (p < 0.001), significantly different to unbaited controls (p < 0.001) where most mosquitoes were on the sides (p = 0.047). In both experiments, approximately 70% of mosquitoes captured on the top surface were clustered within a 90 × 90 cm (or lesser) area directly above the head and chest (p < 0.001). In pitched net tests, similar clustering occurred over the sleeper’s head and chest in baited tests only (p < 0.001). Capture rates at horizontal and vertical surfaces were not significantly different and the sticky-net was not repellent. Conclusion This study demonstrated that An. gambiae activity occurs predominantly within a limited area of the top surface of bed nets. The results provide support for the two-in-one bed net design for managing pyrethroid-resistant vector populations

The activity of the pyrrole insecticide chlorfenapyr in mosquito bioassay: towards a more rational testing and screening of non-neurotoxic insecticides for malaria vector control.

PubMed

Oxborough, Richard M; N'Guessan, Raphael; Jones, Rebecca; Kitau, Jovin; Ngufor, Corine; Malone, David; Mosha, Franklin W; Rowland, Mark W

2015-03-24

The rapid selection of pyrethroid resistance throughout sub-Saharan Africa is a serious threat to malaria vector control. Chlorfenapyr is a pyrrole insecticide which shows no cross resistance to insecticide classes normally used for vector control and is effective on mosquito nets under experimental hut conditions. Unlike neurotoxic insecticides, chlorfenapyr owes its toxicity to disruption of metabolic pathways in mitochondria that enable cellular respiration. A series of experiments explored whether standard World Health Organization (WHO) guidelines for evaluation of long-lasting insecticidal nets, developed through testing of pyrethroid insecticides, are suitable for evaluation of non-neurotoxic insecticides. The efficacy of WHO recommended cone, cylinder and tunnel tests was compared for pyrethroids and chlorfenapyr. To establish bioassay exposure times predictive of insecticide-treated net (ITN) efficacy in experimental hut trials, standard three-minute bioassays of pyrethroid and chlorfenapyr ITNs were compared with longer exposures. Mosquito behaviour and response to chlorfenapyr ITN in bioassays conducted at night were compared to day and across a range of temperatures representative of highland and lowland transmission. Standard three-minute bioassay of chlorfenapyr produced extremely low levels of mortality compared to pyrethroids. Thirty-minute day-time bioassay produced mortality closer to hut efficacy of chlorfenapyr ITN but still fell short of the WHO threshold. Overnight tunnel test with chlorfenapyr produced 100% mortality and exceeded the WHO threshold of 80%. The endogenous circadian activity rhythm of anophelines results in inactivity by day and raised metabolism and flight activity by night. A model which explains improved toxicity of chlorfenapyr ITN when tested at night, and during the day at higher ambient temperature, is that activation of chlorfenapyr and disruption of respiratory pathways is enhanced when the insect is more metabolically

Push by a net, pull by a cow: can zooprophylaxis enhance the impact of insecticide treated bed nets on malaria control?

PubMed Central

2014-01-01

Background Mass insecticide treated bed net (ITN) deployment, and its associated coverage of populations at risk, had “pushed” a decline in malaria transmission. However, it is unknown whether malaria control is being enhanced by zooprophylaxis, i.e., mosquitoes diverted to feed on hosts different from humans, a phenomenon that could further reduce malaria entomological transmission risk in areas where livestock herding is common. Methods Between May and July 2009, we collected mosquitoes in 104 houses from three neighboring villages with high ITN coverage (over 80%), along Lake Victoria. We also performed a census of livestock in the area and georeferenced tethering points for all herds, as well as, mosquito larval habitats. Bloodmeal contents from sampled mosquitoes were analyzed, and each mosquito was individually tested for malaria sporozoite infections. We then evaluated the association of human density, ITN use, livestock abundance and larval habitats with mosquito abundance, bloodfeeding on humans and malaria sporozoite rate using generalized linear mixed effects models. Results We collected a total of 8123 mosquitoes, of which 1664 were Anopheles spp. malaria vectors over 295 household spray catches. We found that vector household abundance was mainly driven by the number of householders (P < 0.05), goats/sheep tethered around the house (P < 0.05) and ITNs, which halved mosquito abundance (P < 0.05). In general, similar patterns were observed for Anopheles arabiensis, but not An. gambiae s.s. and An. funestus s.s., whose density did not increase with the presence of livestock animals. Feeding on humans significantly increased in all species with the number of householders (P < 0.05), and only significantly decreased for An. arabiensis in the presence of cattle (P < 0.05). Only 26 Anopheles spp. vectors had malaria sporozoites with the sporozoite rate significantly decreasing as the proportion of cattle feeding mosquitoes increased

Wash-resistance of pirimiphos-methyl insecticide treatments of window screens and eave baffles for killing indoor-feeding malaria vector mosquitoes: an experimental hut trial, South East of Zambia.

PubMed

Chinula, Dingani; Sikaala, Chadwick H; Chanda-Kapata, Pascalina; Hamainza, Busiku; Zulu, Reuben; Reimer, Lisa; Chizema, Elizabeth; Kiware, Samson; Okumu, Fredros O; Killeen, Gerry

2018-04-13

The effectiveness of long-lasting insecticidal-treated nets (LLINs) and indoor residual spraying (IRS) for malaria control is threatened by resistance to commonly used pyrethroid insecticides. Rotations, mosaics, combinations, or mixtures of insecticides from different complementary classes are recommended by the World Health Organization (WHO) for mitigating against resistance, but many of the alternatives to pyrethroids are prohibitively expensive to apply in large national IRS campaigns. Recent evaluations of window screens and eave baffles (WSEBs) treated with pirimiphos-methyl (PM), to selectively target insecticides inside houses, demonstrated malaria vector mortality rates equivalent or superior to IRS. However, the durability of efficacy when co-applied with polyacrylate-binding agents (BA) remains to be established. This study evaluated whether WSEBs, co-treated with PM and BA have comparable wash resistance to LLINs and might therefore remain insecticidal for years rather than months. WHO-recommended wire ball assays of insecticidal efficacy were applied to polyester netting treated with or without BA plus 1 or 2 g/sq m PM. They were then tested for insecticidal efficacy using fully susceptible insectary-reared Anopheles gambiae mosquitoes, following 0, 5, 10, 15, then 20 washes as per WHO-recommended protocols for accelerated ageing of LLINs. This was followed by a small-scale field trial in experimental huts to measure malaria vector mortality achieved by polyester netting WSEBs treated with BA and 2 g/sq m PM after 0, 10 and then 20 standardized washes, alongside recently applied IRS using PM. Co-treatment with BA and either dosage of PM remained insecticidal over 20 washes in the laboratory. In experimental huts, WSEBs treated with PM plus BA consistently killed similar proportions of Anopheles arabiensis mosquitoes to PM-IRS (both consistently ≥ 94%), even after 20 washes. Co-treating WSEBs with both PM and BA results in wash

Comparative field evaluation of combinations of long-lasting insecticide treated nets and indoor residual spraying, relative to either method alone, for malaria prevention in an area where the main vector is Anopheles arabiensis

PubMed Central

2013-01-01

Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are commonly used together in the same households to improve malaria control despite inconsistent evidence on whether such combinations actually offer better protection than nets alone or IRS alone. Methods Comparative tests were conducted using experimental huts fitted with LLINs, untreated nets, IRS plus untreated nets, or combinations of LLINs and IRS, in an area where Anopheles arabiensis is the predominant malaria vector species. Three LLIN types, Olyset®, PermaNet 2.0® and Icon Life® nets and three IRS treatments, pirimiphos-methyl, DDT, and lambda cyhalothrin, were used singly or in combinations. We compared, number of mosquitoes entering huts, proportion and number killed, proportions prevented from blood-feeding, time when mosquitoes exited the huts, and proportions caught exiting. The tests were done for four months in dry season and another six months in wet season, each time using new intact nets. Results All the net types, used with or without IRS, prevented >99% of indoor mosquito bites. Adding PermaNet 2.0® and Icon Life®, but not Olyset® nets into huts with any IRS increased mortality of malaria vectors relative to IRS alone. However, of all IRS treatments, only pirimiphos-methyl significantly increased vector mortality relative to LLINs alone, though this increase was modest. Overall, median mortality of An. arabiensis caught in huts with any of the treatments did not exceed 29%. No treatment reduced entry of the vectors into huts, except for marginal reductions due to PermaNet 2.0® nets and DDT. More than 95% of all mosquitoes were caught in exit traps rather than inside huts. Conclusions Where the main malaria vector is An. arabiensis, adding IRS into houses with intact pyrethroid LLINs does not enhance house-hold level protection except where the IRS employs non-pyrethroid insecticides such as pirimiphos-methyl, which can confer modest enhancements. In

Genetic variation associated with increased insecticide resistance in the malaria mosquito, Anopheles coluzzii.

PubMed

Main, Bradley J; Everitt, Amanda; Cornel, Anthony J; Hormozdiari, Fereydoun; Lanzaro, Gregory C

2018-04-04

Malaria mortality rates in sub-Saharan Africa have declined significantly in recent years as a result of increased insecticide-treated bed net (ITN) usage. A major challenge to further progress is the emergence and spread of insecticide resistance alleles in the Anopheles mosquito vectors, like An. coluzzii. A non-synonymous mutation in the para voltage-gated sodium channel gene reduces pyrethroid-binding affinity, resulting in knockdown resistance (kdr). Metabolic mechanisms of insecticide resistance involving detoxification genes like cytochrome P450 genes, carboxylesterases, and glutathione S-transferases are also important. As some gene activity is tissue-specific and/or environmentally induced, gene regulatory variation may be overlooked when comparing expression from whole mosquito bodies under standard rearing conditions. We detected complex insecticide resistance in a 2014 An. coluzzii colony from southern Mali using bottle bioassays. Additional bioassays involving recombinant genotypes from a cross with a relatively susceptible 1995 An. coluzzii colony from Mali confirmed the importance of kdr and associated increased permethrin resistance to the CYP9K1 locus on the X chromosome. Significant differential expression of CYP9K1 was not observed among these colonies in Malpighian tubules. However, the P450 gene CYP6Z1 was overexpressed in resistant individuals following sublethal permethrin exposure and the carboxylesterase gene COEAE5G was constitutively overexpressed. The significant P450-related insecticide resistance observed in the 2014 An. coluzzii colony indicates that ITNs treated with the P450 inhibitor piperonyl butoxide (PBO) would be more effective in this region. The known insecticide resistance gene CYP6Z1 was differentially expressed exclusively in the context of sublethal permethrin exposure, highlighting the importance of tissue-specificity and environmental conditions in gene expression studies. The increased activity of the carboxylesterase

Preventing Childhood Malaria in Africa by Protecting Adults from Mosquitoes with Insecticide-Treated Nets

PubMed Central

Killeen, Gerry F; Smith, Tom A; Ferguson, Heather M; Mshinda, Hassan; Abdulla, Salim; Lengeler, Christian; Kachur, Steven P

2007-01-01

Background Malaria prevention in Africa merits particular attention as the world strives toward a better life for the poorest. Insecticide-treated nets (ITNs) represent a practical means to prevent malaria in Africa, so scaling up coverage to at least 80% of young children and pregnant women by 2010 is integral to the Millennium Development Goals (MDG). Targeting individual protection to vulnerable groups is an accepted priority, but community-level impacts of broader population coverage are largely ignored even though they may be just as important. We therefore estimated coverage thresholds for entire populations at which individual- and community-level protection are equivalent, representing rational targets for ITN coverage beyond vulnerable groups. Methods and Findings Using field-parameterized malaria transmission models, we show that high (80% use) but exclusively targeted coverage of young children and pregnant women (representing <20% of the population) will deliver limited protection and equity for these vulnerable groups. In contrast, relatively modest coverage (35%–65% use, with this threshold depending on ecological scenario and net quality) of all adults and children, rather than just vulnerable groups, can achieve equitable community-wide benefits equivalent to or greater than personal protection. Conclusions Coverage of entire populations will be required to accomplish large reductions of the malaria burden in Africa. While coverage of vulnerable groups should still be prioritized, the equitable and communal benefits of wide-scale ITN use by older children and adults should be explicitly promoted and evaluated by national malaria control programmes. ITN use by the majority of entire populations could protect all children in such communities, even those not actually covered by achieving existing personal protection targets of the MDG, Roll Back Malaria Partnership, or the US President's Malaria Initiative. PMID:17608562

Implications of bio-efficacy and persistence of insecticides when indoor residual spraying and long-lasting insecticide nets are combined for malaria prevention.

PubMed

Okumu, Fredros O; Chipwaza, Beatrice; Madumla, Edith P; Mbeyela, Edgar; Lingamba, Geoffrey; Moore, Jason; Ntamatungro, Alex J; Kavishe, Deo R; Moore, Sarah J

2012-11-19

Bio-efficacy and residual activity of insecticides used for indoor residual spraying (IRS) and long-lasting insecticide nets (LLINs) were assessed against laboratory-reared and wild populations of the malaria vector, Anopheles arabiensis in south eastern Tanzania. Implications of the findings are examined in the context of potential synergies and redundancies where IRS and LLINs are combined. Bioassays were conducted monthly for six months on three LLIN types (Olyset® PermaNet 2.0®,and Icon Life®) and three IRS treatments (2 g/m2 pirimiphos-methyl, 2 g/m2 DDT and 0.03 g/m2 lambda-cyhalothrin, sprayed on mud walls and palm ceilings of experimental huts). Tests used susceptible laboratory-reared An. arabiensis exposed in cones (nets and IRS) or wire balls (nets only). Susceptibility of wild populations was assessed using WHO diagnostic concentrations and PCR for knock-down resistance (kdr) genes. IRS treatments killed ≥ 85% of mosquitoes exposed on palm ceilings and ≥ 90% of those exposed on mud walls, but up to 50% of this toxicity decayed within 1-3 months, except for DDT. By 6th month, only 7.5%, 42.5% and 30.0% of mosquitoes died when exposed to ceilings sprayed with pirimiphos-methyl, DDT or lambda-cyhalothrin respectively, while 12.5%, 36.0% and 27.5% died after exposure to mud walls sprayed with the same insecticides. In wire-ball assays, mortality decreased from 98.1% in 1st month to 92.6% in 6th month in tests on PermaNet 2.0®, from 100% to 61.1% on Icon Life® and from 93.2% to 33.3% on Olyset® nets. In cone bioassays, mortality reduced from 92.8% in 1st month to 83.3% in 6th month on PermaNet 2.0®, from 96.9% to 43.80% on Icon Life® and from 85.6% to 14.6% on Olyset®. Wild An. arabiensis were 100% susceptible to DDT, 95.8% to deltamethrin, 90.2% to lambda cyhalothrin and 95.2% susceptible to permethrin. No kdr gene mutations were detected. In bioassays where sufficient contact with treated surfaces is assured, LLINs and IRS kill high

Investigating a Non-Mesh Mosquito Net among Outdoor Sleeping Nomadic Communities in Kenya

PubMed Central

Gore-Langton, Georgia R.; Mungai, James; Alenwi, Nfornuh; Abagira, Abdullahi; Bicknell, Owen M.; Harrison, Rebecca E.; Hassan, Farah Amin; Munga, Stephen; Eves, Katie; Juma, Elizabeth; Allan, Richard

2015-01-01

Rising reports of exophagic malaria vectors make even more pressing the need for alternatives to traditional, mesh, long-lasting insecticidal nets (LLINs) designed for indoor sleeping and often inadequate in the protection of outdoor-sleeping populations. This study tests and evaluates the retention, utilization, and durability of novel, non-mesh nets designed for outdoor use. Longitudinal, cross-sectional surveys were conducted, the physical condition of nets was assessed, and bio-efficacy and insecticide content were tested. At 22 months, retention was 98.0%; 97.1% of nets fell within the World Health Organization (WHO) category of being in “good” condition; none were in the “torn” category. At 18 months post-distribution, 100% of nets had at least WHO Pesticide Evaluation Scheme (WHOPES)-acceptable levels of insecticide, this proportion was 66.7% at 22 months. This novel mosquito net has the potential to provide a durable and context-specific tool to prevent malaria among traditionally hard-to-protect and highly vulnerable populations. PMID:26416107

Effectiveness of insecticide-treated and untreated nets to prevent malaria in India.

PubMed

Van Remoortel, Hans; De Buck, Emmy; Singhal, Maneesh; Vandekerckhove, Philippe; Agarwal, Satya P

2015-08-01

India is the most malaria-endemic country in South-East Asia, resulting in a high socio-economic burden. Insecticide-treated or untreated nets are effective interventions to prevent malaria. As part of an Indian first-aid guideline project, we aimed to investigate the magnitude of this effect in India. We searched MEDLINE, Embase and Central to systematically review Indian studies on the effectiveness of treated or untreated vs. no nets. Parasite prevalence and annual parasite incidence served as malaria outcomes. The overall effect was investigated by performing meta-analyses and calculating the pooled risk ratios (RR) and incidence rate ratios. Of 479 articles, we finally retained 16 Indian studies. Untreated nets decreased the risk of parasite prevalence compared to no nets [RR 0.69 (95% CI; 0.55, 0.87) in high-endemic areas, RR 0.49 (95% CI; 0.28, 0.84) in low-endemic areas], as was the case but more pronounced for treated nets [RR 0.35 (95% CI; 0.26, 0.47) in high-endemic areas, risk ratio 0.16 (95% CI; 0.06, 0.44) in low-endemic areas]. Incidence rate ratios showed a similar observation: a significantly reduced rate of parasites in the blood for untreated nets vs. no nets, which was more pronounced in low-endemic areas and for those who used treated nets. The average effect of treated nets (vs. no nets) on parasite prevalence was higher in Indian studies (RR 0.16-0.35) than in non-Indian studies (data derived from a Cochrane systematic review; RR 0.58-0.87). Both treated and untreated nets have a clear protective effect against malaria in the Indian context. This effect is more pronounced there than in other countries. © 2015 John Wiley & Sons Ltd.

Status of Insecticide Resistance in Papua New Guinea: An Update from Nation-Wide Monitoring of Anopheles Mosquitoes.

PubMed

Koimbu, Gussy; Czeher, Cyrille; Katusele, Michelle; Sakur, Muker; Kilepak, Lemen; Tandrapah, Anthony; Hetzel, Manuel W; Pulford, Justin; Robinson, Leanne; Karl, Stephan

2018-01-01

Insecticide resistance (IR) monitoring is an important component of vector-borne disease control. The last assessment of IR in Papua New Guinea (PNG) was conducted in 2010. Since then, vector populations have been exposed to higher levels of pyrethroids with the continued nation-wide distribution of insecticide-treated nets. Here, we provide an update on phenotypic IR in four highly malaria-endemic areas of PNG. IR against deltamethrin, lambda-cyhalothrin, and dichlorodiphenyltrichloroethane was assessed using World Health Organization bioassays. A total of 108 bioassays for each insecticide were conducted screening 2,290 adult female anopheline mosquitoes. No phenotypic resistance was observed. Bioassay parameters agreed well with those observed in other studies that used the same assays and insecticides. These results indicate that the three tested insecticides are still universally effective in PNG. Continued IR monitoring (every 1-2 years) in PNG is recommended to detect reduced susceptibility early and adjust guidelines to prevent widespread resistance.

Evaluation of mosquito responses to pyrethroid insecticides topically applied to sheep.

PubMed

Johnson, G D; Goosey, H B; Rolston, M G; Miller, W L; Hokit, D G; Redden, R R; Kott, R W

2013-06-01

A rise in the incidence of mosquito-transmitted Cache Valley virus (CVV) in lambs in 2011 prompted a study to evaluate on-animal pyrethroid insecticides to reduce mosquito attacks on sheep. Using enclosure traps for 1 night per wk for 6 wk, we compared engorgement rates of mosquitoes given the opportunity to feed on untreated sheep and sheep treated with 1 Python insecticide ear tag (containing 10% zeta-cypermethrin and 20% piperonyl butoxide) per animal or 2 synergized permethrin body spray treatments (containing 2.5% permethrin and 2.5% piperonyl butoxide). During the 6-wk study, 18,920 mosquitoes were collected in the animal-baited enclosure traps. Thirteen species were identified from these collections with the floodwater species Aedes increpitus and Ae. idahoensis making up 68% of the total. Potential CVV vector species, making up 25% of the samples, included Ae. vexans, Ae. dorsalis, Culex tarsalis, and Culiseta inornata. Traps baited with untreated sheep collected 9,701 mosquitoes with 65% of these engorged. Traps baited with sheep treated with Python ear tags or permethrin spray collected 4,034 and 4,555, respectively, with engorgement rates of 23% and 35%. Blood feeding on ear-tagged sheep was significantly reduced by as much as 90% compared to the untreated sheep, and protection lasted 4 wk or longer. Permethrin spray treatments were most effective within 24 h after application and provided better protection against Ae. dorsalis than the Python tag. Effectiveness of the permethrin spray diminished 1 wk after the 2nd application was made. The effect of these treatments appeared to be repellency because negligible mosquito mortality was observed at the time of collection. Further evaluation of these insecticides under conditions of natural exposure to a mosquito-borne pathogen is warranted.

Construct validity of the bidding game, binary with follow-up, and a novel structured haggling question format in determining willingness to pay for insecticide-treated mosquito nets.

PubMed

Onwujekwe, Obinna; Fox-Rushby, Julia; Hanson, Kara

2008-01-01

This study examines whether making question formats better fit the cultural context of markets would improve the construct validity of estimates of willingness to pay (WTP). WTP for insecticide-treated mosquito nets was elicited using the bidding game, binary with follow-up (BWFU), and a novel structured haggling technique (SH) that mimicked price taking in market places in the study area. The results show that different question formats generated different distributions of WTP. Following a comparison of alternative models for each question format, construct validity was compared using the most consistently appropriate model across question formats for the positive WTP values, in this case, ordinary least squares. Three criteria (the number of statistically significant explanatory variables that had the anticipated sign, the value of the adjusted R(2), and the proportion that were statistically significant With the anticipated sign) used to assess the relative performance of each question format indicated that SH performed best and BWFU worst. However, differences in the levels of income, education, and percentage of household heads responding to the different question formats across the samples complicate this conclusion. Hence, the results suggest that the SH technique is worthy of further investigation and use.

Anopheles sinensis mosquito insecticide resistance: comparison of three mosquito sample collection and preparation methods and mosquito age in resistance measurements.

PubMed

Xu, Tielong; Zhong, Daibin; Tang, Linhua; Chang, Xuelian; Fu, Fengyang; Yan, Guiyun; Zheng, Bin

2014-01-28

Insecticide resistance monitoring in malaria mosquitoes is essential for guiding the rational use of insecticides in vector control programs. Resistance bioassay is the first step for insecticide monitoring and it lays an important foundation for molecular examination of resistance mechanisms. In the literature, various mosquito sample collection and preparation methods have been used, but how mosquito sample collection and preparation methods affect insecticide susceptibility bioassay results is largely unknown. The objectives of this study were to determine whether mosquito sample collection and preparation methods affected bioassay results, which may cause incorrect classification of mosquito resistance status. The study was conducted in Anopheles sinensis mosquitoes in two study sites in central China. Three mosquito sample collection and preparation methods were compared for insecticide susceptibility, kdr frequencies and metabolic enzyme activities: 1) adult mosquitoes collected from the field; 2) F1 adults from field collected, blood-fed mosquitoes; and 3) adult mosquitoes reared from field collected larvae. Mosquito sample collection and preparation methods significantly affected mortality rates in the standard WHO tube resistance bioassay. Mortality rate of field-collected female adults was 10-15% higher than in mosquitoes reared from field-collected larvae and F1 adults from field collected blood-fed females. This pattern was consistent in mosquitoes from the two study sites. High kdr mutation frequency (85-95%) with L1014F allele as the predominant mutation was found in our study populations. Field-collected female adults consistently exhibited the highest monooxygenase and GST activities. The higher mortality rate observed in the field-collected female mosquitoes may have been caused by a mixture of mosquitoes of different ages, as older mosquitoes were more susceptible to deltamethrin than younger mosquitoes. Female adults reared from field

Implications of bio-efficacy and persistence of insecticides when indoor residual spraying and long-lasting insecticide nets are combined for malaria prevention

PubMed Central

2012-01-01

Background Bio-efficacy and residual activity of insecticides used for indoor residual spraying (IRS) and long-lasting insecticide nets (LLINs) were assessed against laboratory-reared and wild populations of the malaria vector, Anopheles arabiensis in south eastern Tanzania. Implications of the findings are examined in the context of potential synergies and redundancies where IRS and LLINs are combined. Methods Bioassays were conducted monthly for six months on three LLIN types (Olyset® PermaNet 2.0®,and Icon Life®) and three IRS treatments (2 g/m2 pirimiphos-methyl, 2 g/m2 DDT and 0.03 g/m2 lambda-cyhalothrin, sprayed on mud walls and palm ceilings of experimental huts). Tests used susceptible laboratory-reared An. arabiensis exposed in cones (nets and IRS) or wire balls (nets only). Susceptibility of wild populations was assessed using WHO diagnostic concentrations and PCR for knock-down resistance (kdr) genes. Results IRS treatments killed ≥ 85% of mosquitoes exposed on palm ceilings and ≥ 90% of those exposed on mud walls, but up to 50% of this toxicity decayed within 1–3 months, except for DDT. By 6th month, only 7.5%, 42.5% and 30.0% of mosquitoes died when exposed to ceilings sprayed with pirimiphos-methyl, DDT or lambda-cyhalothrin respectively, while 12.5%, 36.0% and 27.5% died after exposure to mud walls sprayed with the same insecticides. In wire-ball assays, mortality decreased from 98.1% in 1st month to 92.6% in 6th month in tests on PermaNet 2.0®, from 100% to 61.1% on Icon Life® and from 93.2% to 33.3% on Olyset® nets. In cone bioassays, mortality reduced from 92.8% in 1st month to 83.3% in 6th month on PermaNet 2.0®, from 96.9% to 43.80% on Icon Life® and from 85.6% to 14.6% on Olyset®. Wild An. arabiensis were 100% susceptible to DDT, 95.8% to deltamethrin, 90.2% to lambda cyhalothrin and 95.2% susceptible to permethrin. No kdr gene mutations were detected. Conclusions In bioassays where sufficient contact with treated surfaces is

Combining indoor residual spraying and insecticide-treated nets for malaria control in Africa: a review of possible outcomes and an outline of suggestions for the future

PubMed Central

2011-01-01

Insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are currently the preferred methods of malaria vector control. In many cases, these methods are used together in the same households, especially to suppress transmission in holoendemic and hyperendemic scenarios. Though widespread, there has been limited evidence suggesting that such co-application confers greater protective benefits than either ITNs or IRS when used alone. Since both methods are insecticide-based and intradomicilliary, this article hypothesises that outcomes of their combination would depend on effects of the candidate active ingredients on mosquitoes that enter or those that attempt to enter houses. It is suggested here that enhanced household level protection can be achieved if the ITNs and IRS have divergent yet complementary properties, e.g. highly deterrent IRS compounds coupled with highly toxic ITNs. To ensure that the problem of insecticide resistance is avoided, the ITNs and IRS products should preferably be of different insecticide classes, e.g. pyrethroid-based nets combined with organophosphate or carbamate based IRS. The overall community benefits would however depend also on other factors such as proportion of people covered by the interventions and the behaviour of vector species. This article concludes by emphasizing the need for basic and operational research, including mathematical modelling to evaluate IRS/ITN combinations in comparison to IRS alone or ITNs alone. PMID:21798053

KINET: a social marketing programme of treated nets and net treatment for malaria control in Tanzania, with evaluation of child health and long-term survival.

PubMed

Schellenberg, J R; Abdulla, S; Minja, H; Nathan, R; Mukasa, O; Marchant, T; Mponda, H; Kikumbih, N; Lyimo, E; Manchester, T; Tanner, M; Lengeler, C

1999-01-01

We present a large-scale social marketing programme of insecticide-treated nets in 2 rural districts in southwestern Tanzania (population 350,000) and describe how the long-term child health and survival impact will be assessed. Formative and market research were conducted in order to understand community perceptions, knowledge, attitudes and practice with respect to the products to be socially marketed. We identified Zuia Mbu (Kiswahili for 'prevent mosquitoes') as a suitable brand name for both treated nets and single-dose insecticide treatment sachets. A mix of public and private sales outlets is used for distribution. In the first stage of a stepped introduction 31 net agents were appointed and trained in 18 villages: 15 were shop owners, 14 were village leaders, 1 was a parish priest and 1 a health worker. For net treatment 37 young people were appointed in the same villages and trained as agents. Further institutions in both districts such as hospitals, development projects and employers were also involved in distribution. Promotion for both products was intense and used a variety of channels. A total of 22,410 nets and 8072 treatments were sold during the first year: 18 months after launching, 46% of 312 families with children aged under 5 years reported that their children were sleeping under treated nets. A strong evaluation component in over 50,000 people allows assessment of the long-term effects of insecticide-treated nets on child health and survival, anaemia in pregnancy, and the costs of the intervention. This evaluation is based on cross-sectional surveys, and case-control and cohort studies.

Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: a WHO-coordinated, prospective, international, observational cohort study.

PubMed

Kleinschmidt, Immo; Bradley, John; Knox, Tessa Bellamy; Mnzava, Abraham Peter; Kafy, Hmooda Toto; Mbogo, Charles; Ismail, Bashir Adam; Bigoga, Jude D; Adechoubou, Alioun; Raghavendra, Kamaraju; Cook, Jackie; Malik, Elfatih M; Nkuni, Zinga José; Macdonald, Michael; Bayoh, Nabie; Ochomo, Eric; Fondjo, Etienne; Awono-Ambene, Herman Parfait; Etang, Josiane; Akogbeto, Martin; Bhatt, Rajendra M; Chourasia, Mehul Kumar; Swain, Dipak K; Kinyari, Teresa; Subramaniam, Krishanthi; Massougbodji, Achille; Okê-Sopoh, Mariam; Ogouyemi-Hounto, Aurore; Kouambeng, Celestin; Abdin, Mujahid Sheikhedin; West, Philippa; Elmardi, Khalid; Cornelie, Sylvie; Corbel, Vincent; Valecha, Neena; Mathenge, Evan; Kamau, Luna; Lines, Jonathan; Donnelly, Martin James

2018-04-09

Scale-up of insecticide-based interventions has averted more than 500 million malaria cases since 2000. Increasing insecticide resistance could herald a rebound in disease and mortality. We aimed to investigate whether insecticide resistance was associated with loss of effectiveness of long-lasting insecticidal nets and increased malaria disease burden. This WHO-coordinated, prospective, observational cohort study was done at 279 clusters (villages or groups of villages in which phenotypic resistance was measurable) in Benin, Cameroon, India, Kenya, and Sudan. Pyrethroid long-lasting insecticidal nets were the principal form of malaria vector control in all study areas; in Sudan this approach was supplemented by indoor residual spraying. Cohorts of children from randomly selected households in each cluster were recruited and followed up by community health workers to measure incidence of clinical malaria and prevalence of infection. Mosquitoes were assessed for susceptibility to pyrethroids using the standard WHO bioassay test. Country-specific results were combined using meta-analysis. Between June 2, 2012, and Nov 4, 2016, 40 000 children were enrolled and assessed for clinical incidence during 1·4 million follow-up visits. 80 000 mosquitoes were assessed for insecticide resistance. Long-lasting insecticidal net users had lower infection prevalence (adjusted odds ratio [OR] 0·63, 95% CI 0·51-0·78) and disease incidence (adjusted rate ratio [RR] 0·62, 0·41-0·94) than did non-users across a range of resistance levels. We found no evidence of an association between insecticide resistance and infection prevalence (adjusted OR 0·86, 0·70-1·06) or incidence (adjusted RR 0·89, 0·72-1·10). Users of nets, although significantly better protected than non-users, were nevertheless subject to high malaria infection risk (ranging from an average incidence in net users of 0·023, [95% CI 0·016-0·033] per person-year in India, to 0·80 [0·65-0·97] per person

Which family members use the best nets? An analysis of the condition of mosquito nets and their distribution within households in Tanzania.

PubMed

Tsuang, Angela; Lines, Jo; Hanson, Kara

2010-07-22

Household ownership of insecticide-treated mosquito nets (ITNs) is increasing, and coverage targets have been revised to address universal coverage with ITNs. However, many households do not have enough nets to cover everyone, and the nets available vary in physical condition and insecticide treatment status. Since 2004, the Government of Tanzania has been implementing the Tanzania National Voucher Scheme (TNVS), which distributes vouchers for ITNs through antenatal clinics to target pregnant women and their infants. This analysis aimed to determine the following: (1) coverage patterns of bed nets within households according to physical condition and treatment status; (2) who might be at risk if mosquitoes were diverted from occupants of untreated nets to those not using nets? (3) the degree to which those at highest risk of malaria use the most protective nets. Data from the 2006 TNVS household survey were analysed to assess within-household distribution of net use. The associations between net characteristics and net user were also evaluated. Multivariate analysis was applied to the relationship between the number of holes per net and user characteristics while adjusting for confounders. In households with a net:person ratio better than 1:4 (one net for every four household members), more than 80% of the people in such households reported using a net the previous night. ITNs were most likely to be used by infants, young children (1-4 y), and women of childbearing age; they were least likely to be used by older women (>or=50 y), older children (5-14 y), and adult men. The nets used by infants and women of childbearing age were in better-than-average physical condition; the nets used by older women and older children were in worse-than-average condition; while young children and adult men used nets in intermediate (average) condition. When adjusted for confounders, the nets used by young and older children had more holes than nets used by infants. Infants and other

Effectiveness of organo-phosphorus insecticides against houseflies and mosquitos

PubMed Central

Lindquist, A. W.

1957-01-01

The paper describes the research being undertaken on organo-phosphorus insecticides for the control of houseflies and mosquitos. The information obtained from laboratory and field tests indicates that these insecticides are at present effective substitutes for DDT and other chlorinated-hydrocarbon insecticides for use against resistant houseflies and culicine mosquitos, but the residual applications are not as long lasting as those of DDT and therefore will probably not be as efficient in anopheline control. PMID:13413645

Comparing insecticide-treated bed net use to Plasmodium falciparum infection among schoolchildren living near Lake Victoria, Kenya.

PubMed

Okoyo, Collins; Mwandawiro, Charles; Kihara, Jimmy; Simiyu, Elses; Gitonga, Caroline W; Noor, Abdisalan M; Njenga, Sammy M; Snow, Robert W

2015-12-22

Under trial conditions insecticide-treated nets have been shown to provide significant clinical and mortality protection under a range of malaria transmission intensity conditions. There are, however, few operational impact data, notably in very intense transmission conditions. This study, reports on malaria infection among Kenyan schoolchildren living in areas of intense malaria transmission and their reported use of insecticide-treated bed nets. 5188 children in 54 schools were randomly sampled from seven counties surrounding Lake Victoria between May and June 2014. A questionnaire was administered to schoolchildren in classes 2-6 on the use of a long-lasting, insecticide-treated net (LLIN) the night before the survey and provided a single blood sample for a rapid diagnostic test for malaria infection. Analysis of the impact of insecticide-treated net use on malaria prevalence was undertaken using a multivariable, mixed effects, logistic regression at 95% confidence interval (CI), taking into account hierarchical nature of the data and results adjusted for school clusters. The overall prevalence of malaria infection was 48.7%, two-thirds (67.9%) of the children reported using LLIN, 91.3% of the children reported that their households own at least one LLIN and the household LLIN coverage was 2.5 persons per one LLIN. The prevalence of infection showed variation across the counties, with prevalence being highest in Busia (66.9%) and Homabay (51.8%) counties, and lowest in Migori County (29.6%). Generally, malaria parasite prevalence differed between age groups and gender with the highest prevalence occurring in children below 7 years (50.6%) and males (52.2%). Adjusting for county and school, there was a significant reduction in odds of malaria infection among the schoolchildren who reported LLIN use the previous night by 14 % (aOR 0.86, 95% CI 0.74-0.98, P < 0.027). Malaria transmission continues to be high around Lake Victoria. Despite evidence of increasing

Ownership and Use of Insecticide-Treated Nets among People Living in Malaria Endemic Areas of Eastern Myanmar.

PubMed

Aung, Tin; Wei, Chongyi; McFarland, Willi; Aung, Ye Kyaw; Khin, Hnin Su Su

2016-01-01

Myanmar has the highest burden of malaria in the Greater Mekong. However, there is limited information on ownership and use of insecticide-treated nets (ITNs) in areas of Myanmar most severely affected by malaria. We describe ownership and use of ITNs among people in the malaria-endemic eastern parts of Myanmar and factors associated with ITN use. A cross-sectional household survey using a multi-stage cluster design was conducted in malaria-endemic townships in eastern Myanmar during the high malaria season of August to September, 2014. An effective ITN was defined as 1) a long-lasting insecticide-treated net obtained within the past three years, or 2) any net treated with insecticide within the past year. In 4,679 households, the average number of ITNs per household was higher in rural compared to urban areas (0.6 vs. 0.4, p <0.001) as well as the proportion of households owning at least one ITN (27.3% vs. 15.5%, p<0.001). The proportion of households in which all members slept under an ITN was also higher in rural compared to urban areas (15.3% vs 6.9%, p<0.001). In multivariate analysis, rural households (adjusted odds ratio [aOR] 1.78, 95% CI: 1.43-2.21, p<0.001), households in which respondents knew malaria is transmitted by mosquitoes (aOR 1.35, 95% CI: 1.10-1.65, p = 0.004), and in which respondents knew malaria can be prevented by ITN use (aOR 1.86, 95% CI: 1.28-2.70, p<0.001) were more likely to have all members sleep under an ITN. Compared to the lowest socio-economic quintile, households in the richest quintile were less likely to have all members sleep under an ITN (aOR 0.47; 95% CI: 0.33-0.66, p<0.001). Households in which the main income earner was a skilled worker or a businessman were less likely to have all members sleep under an ITN (aOR, 0.70, 95% CI: 0.52-0.96, p<0.025) compared to those headed by farmers or fishermen. Households in which all children slept under an ITN were more likely to be in rural areas (aOR 1.58, 95% CI: 1.19-2.09, p = 0

Cost and cost effectiveness of long-lasting insecticide-treated bed nets - a model-based analysis

PubMed Central

2012-01-01

Background The World Health Organization recommends that national malaria programmes universally distribute long-lasting insecticide-treated bed nets (LLINs). LLINs provide effective insecticide protection for at least three years while conventional nets must be retreated every 6-12 months. LLINs may also promise longer physical durability (lifespan), but at a higher unit price. No prospective data currently available is sufficient to calculate the comparative cost effectiveness of different net types. We thus constructed a model to explore the cost effectiveness of LLINs, asking how a longer lifespan affects the relative cost effectiveness of nets, and if, when and why LLINs might be preferred to conventional insecticide-treated nets. An innovation of our model is that we also considered the replenishment need i.e. loss of nets over time. Methods We modelled the choice of net over a 10-year period to facilitate the comparison of nets with different lifespan (and/or price) and replenishment need over time. Our base case represents a large-scale programme which achieves high coverage and usage throughout the population by distributing either LLINs or conventional nets through existing health services, and retreats a large proportion of conventional nets regularly at low cost. We identified the determinants of bed net programme cost effectiveness and parameter values for usage rate, delivery and retreatment cost from the literature. One-way sensitivity analysis was conducted to explicitly compare the differential effect of changing parameters such as price, lifespan, usage and replenishment need. Results If conventional and long-lasting bed nets have the same physical lifespan (3 years), LLINs are more cost effective unless they are priced at more than USD 1.5 above the price of conventional nets. Because a longer lifespan brings delivery cost savings, each one year increase in lifespan can be accompanied by a USD 1 or more increase in price without the cheaper net

Effectiveness of a long-lasting piperonyl butoxide-treated insecticidal net and indoor residual spray interventions, separately and together, against malaria transmitted by pyrethroid-resistant mosquitoes: a cluster, randomised controlled, two-by-two factorial design trial.

PubMed

Protopopoff, Natacha; Mosha, Jacklin F; Lukole, Eliud; Charlwood, Jacques D; Wright, Alexandra; Mwalimu, Charles D; Manjurano, Alphaxard; Mosha, Franklin W; Kisinza, William; Kleinschmidt, Immo; Rowland, Mark

2018-04-21

Progress in malaria control is under threat by wide-scale insecticide resistance in malaria vectors. Two recent vector control products have been developed: a long-lasting insecticidal net that incorporates a synergist piperonyl butoxide (PBO) and a long-lasting indoor residual spraying formulation of the insecticide pirimiphos-methyl. We evaluated the effectiveness of PBO long-lasting insecticidal nets versus standard long-lasting insecticidal nets as single interventions and in combination with the indoor residual spraying of pirimiphos-methyl. We did a four-group cluster randomised controlled trial using a two-by-two factorial design of 48 clusters derived from 40 villages in Muleba (Kagera, Tanzania). We randomly assigned these clusters using restricted randomisation to four groups: standard long-lasting insecticidal nets, PBO long-lasting insecticidal nets, standard long-lasting insecticidal nets plus indoor residual spraying, or PBO long-lasting insecticidal nets plus indoor residual spraying. Both standard and PBO nets were distributed in 2015. Indoor residual spraying was applied only once in 2015. We masked the inhabitants of each cluster to the type of nets received, as well as field staff who took blood samples. Neither the investigators nor the participants were masked to indoor residual spraying. The primary outcome was the prevalence of malaria infection in children aged 6 months to 14 years assessed by cross-sectional surveys at 4, 9, 16, and 21 months after intervention. The endpoint for assessment of indoor residual spraying was 9 months and PBO long-lasting insecticidal nets was 21 months. This trial is registered with ClinicalTrials.gov, number NCT02288637. 7184 (68·0%) of 10 560 households were selected for post-intervention survey, and 15 469 (89·0%) of 17 377 eligible children from the four surveys were included in the intention-to-treat analysis. Of the 878 households visited in the two indoor residual spraying groups, 827 (94%) had

Challenges for malaria elimination in Zanzibar: pyrethroid resistance in malaria vectors and poor performance of long-lasting insecticide nets

PubMed Central

2013-01-01

Background Long-lasting insecticide treated nets (LLINs) and indoor residual house spraying (IRS) are the main interventions for the control of malaria vectors in Zanzibar. The aim of the present study was to assess the susceptibility status of malaria vectors against the insecticides used for LLINs and IRS and to determine the durability and efficacy of LLINs on the island. Methods Mosquitoes were sampled from Pemba and Unguja islands in 2010–2011 for use in WHO susceptibility tests. One hundred and fifty LLINs were collected from households on Unguja, their physical state was recorded and then tested for efficacy as well as total insecticide content. Results Species identification revealed that over 90% of the Anopheles gambiae complex was An. arabiensis with a small number of An. gambiae s.s. and An. merus being present. Susceptibility tests showed that An. arabiensis on Pemba was resistant to the pyrethroids used for LLINs and IRS. Mosquitoes from Unguja Island, however, were fully susceptible to all pyrethroids tested. A physical examination of 150 LLINs showed that two thirds were damaged after only three years in use. All used nets had a significantly lower (p < 0.001) mean permethrin concentration of 791.6 mg/m2 compared with 944.2 mg/m2 for new ones. Their efficacy decreased significantly against both susceptible An. gambiae s.s. colony mosquitoes and wild-type mosquitoes from Pemba after just six washes (p < 0.001). Conclusion The sustainability of the gains achieved in malaria control in Zanzibar is seriously threatened by the resistance of malaria vectors to pyrethroids and the short-lived efficacy of LLINs. This study has revealed that even in relatively well-resourced and logistically manageable places like Zanzibar, malaria elimination is going to be difficult to achieve with the current control measures. PMID:23537463

Validation of a multi-residue method to determine deltamethrin and alpha-cypermethrin in mosquito nets by gas chromatography with electron capture detection (GC-μECD)

PubMed Central

2013-01-01

Background Nowadays long-lasting insecticidal mosquito nets (LNs) are frequently used around the world to protect people against malaria vectors. As they contain insecticide, laboratory control is needed to check whether the content of the active ingredient follows the conditions of the manufacturer and also if the active ingredient is still present after some time of use. For this purpose, an analytical method had to be developed. The fact that LNs include a range of polymers for the yarn and use coated or incorporated technologies for the active ingredient, it is a challenge to find only one analytical method determining the active ingredient in LNs, which takes into account both impregnation technologies. Some methods are provided by international organizations but are limited by the determination of only one pesticide per method. The aim of this study was to optimize a short time extraction method for deltamethrin and alpha-cypermethrin from coated and incorporated mosquito nets and also to detect both insecticides in one analytical run, using gas chromatography with electron capture detection (GC-μECD). Methods Based on the literature, the most suitable solvent and the adequate extraction process for the insecticides used for net making were identified and adapted for the new multi-residue method. Results The validation data of the multi-residue method to determine deltamethrin and alpha-cypermethrin in mosquito nets by GC-μECD are given. Depending on the concentration of the active ingredient spiked on the nets, the mean recovery for alpha-cypermethrin ranged between 86% and 107% with a relative standard deviation below 3.5%. For deltamethrin it ranged between 90% and 108% with a relative standard deviation also below 3.5%. The limit of detection is 0.009 g.a.i/kg of net (0.3 mg a.i./m2 of net) both for alpha-cypermethrin and deltamethrin. Conclusions Data obtained are excellent. A 30 minutes reflux extraction method with xylene was developed to determine

Widespread mosquito net fishing in the Barotse floodplain: Evidence from qualitative interviews.

PubMed

Larsen, David A; Welsh, Rick; Mulenga, Angela; Reid, Robert

2018-01-01

The insecticide-treated mosquito net (ITN) is a crucial component of malaria control programs, and has prevented many malaria cases and deaths due to scale up. ITNs also serve effectively as fishing nets and various sources have reported use of ITNs for fishing. This article examines how widespread the practice of mosquito net fishing with ITNs is. We conducted in-depth interviews with fishery personnel and traditional leadership from the Barotse Royal Establishment in Western Province, Zambia, to better understand the presence or absence of the use of ITNs as fishing nets. We then coded the interviews for themes through content analysis. Additionally we conducted a desk review of survey data to show trends in malaria indicators, nutritional status of the population and fish consumption. All those interviewed reported that ITNs are regularly used for fishing in Western Zambia and the misuse is widespread. Concurrently those interviewed reported declines in fish catches both in terms of quantity and quality leading to threatened food security in the area. In addition to unsustainable fishing practices those interviewed referenced drought and population pressure as reasons for fishery decline. Malaria indicators do not show a trend in declining malaria transmission, fish consumption has dropped dramatically and nutritional status has not improved over time. Despite the misuse of the ITNs for fishing all those interviewed maintained that ITN distribution should continue. Donors, control programs and scientists should realize that misuse of ITNs as fishing nets is a current problem for malaria control and potentially for food security that needs to be addressed.

Widespread mosquito net fishing in the Barotse floodplain: Evidence from qualitative interviews

PubMed Central

Mulenga, Angela; Reid, Robert

2018-01-01

Background The insecticide-treated mosquito net (ITN) is a crucial component of malaria control programs, and has prevented many malaria cases and deaths due to scale up. ITNs also serve effectively as fishing nets and various sources have reported use of ITNs for fishing. This article examines how widespread the practice of mosquito net fishing with ITNs is. Methods We conducted in-depth interviews with fishery personnel and traditional leadership from the Barotse Royal Establishment in Western Province, Zambia, to better understand the presence or absence of the use of ITNs as fishing nets. We then coded the interviews for themes through content analysis. Additionally we conducted a desk review of survey data to show trends in malaria indicators, nutritional status of the population and fish consumption. Results All those interviewed reported that ITNs are regularly used for fishing in Western Zambia and the misuse is widespread. Concurrently those interviewed reported declines in fish catches both in terms of quantity and quality leading to threatened food security in the area. In addition to unsustainable fishing practices those interviewed referenced drought and population pressure as reasons for fishery decline. Malaria indicators do not show a trend in declining malaria transmission, fish consumption has dropped dramatically and nutritional status has not improved over time. Conclusions Despite the misuse of the ITNs for fishing all those interviewed maintained that ITN distribution should continue. Donors, control programs and scientists should realize that misuse of ITNs as fishing nets is a current problem for malaria control and potentially for food security that needs to be addressed. PMID:29719003

Efficacy of PermaNet® 3.0 and PermaNet® 2.0 nets against laboratory-reared and wild Anopheles gambiae sensu lato populations in northern Tanzania.

PubMed

Kweka, Eliningaya J; Lyaruu, Lucile J; Mahande, Aneth M

2017-01-18

Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet® 3.0 LLIN versus the pyrethroid-only PermaNet® 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania. In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes. Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An. arabiensis mosquitoes. All nets used were subjected to cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition and personal protection rate were compared between untreated nets, unwashed LLINs and LLINs that were washed 20 times. Both washed and unwashed PermaNet® 2.0 and PermaNet® 3.0 LLINs had knockdown and mortality rates of 100% against a susceptible strain of An. gambiae sensu stricto. The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet® 3.0 and PermaNet® 2.0 nets was found to be higher than after use of the washed PermaNet® 2.0 and PermaNet® 3.0 nets. Given the increasing incidence of pyrethroid resistance in An. gambiae mosquitoes in Tanzania, we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.

Disrupting Mosquito Reproduction and Parasite Development for Malaria Control

PubMed Central

Gabrieli, Paolo; Buckee, Caroline O.; Catteruccia, Flaminia

2016-01-01

The control of mosquito populations with insecticide treated bed nets and indoor residual sprays remains the cornerstone of malaria reduction and elimination programs. In light of widespread insecticide resistance in mosquitoes, however, alternative strategies for reducing transmission by the mosquito vector are urgently needed, including the identification of safe compounds that affect vectorial capacity via mechanisms that differ from fast-acting insecticides. Here, we show that compounds targeting steroid hormone signaling disrupt multiple biological processes that are key to the ability of mosquitoes to transmit malaria. When an agonist of the steroid hormone 20-hydroxyecdysone (20E) is applied to Anopheles gambiae females, which are the dominant malaria mosquito vector in Sub Saharan Africa, it substantially shortens lifespan, prevents insemination and egg production, and significantly blocks Plasmodium falciparum development, three components that are crucial to malaria transmission. Modeling the impact of these effects on Anopheles population dynamics and Plasmodium transmission predicts that disrupting steroid hormone signaling using 20E agonists would affect malaria transmission to a similar extent as insecticides. Manipulating 20E pathways therefore provides a powerful new approach to tackle malaria transmission by the mosquito vector, particularly in areas affected by the spread of insecticide resistance. PMID:27977810

The economics of social marketing: the case of mosquito nets in Tanzania.

PubMed

Kikumbih, Nassor; Hanson, Kara; Mills, Anne; Mponda, Hadji; Schellenberg, Joanna Armstrong

2005-01-01

There is a growing appreciation of the role of the private sector in expanding the use of key health interventions. At the policy level, this has raised questions about how public sector resources can best be used to encourage the private sector in order to achieve public health impact. Social marketing has increasingly been used to distribute public health products in developing countries. The Kilombero and Ulanga Insecticide-Treated Net Project (KINET) project used a social marketing approach in two districts of Tanzania to stimulate the development of the market for insecticide-treated mosquito nets (ITNs) for malaria control. Using evidence from household surveys, focus group discussions and a costing study in the intervention area and a control area, this paper examines two issues: (1) How does social marketing affect the market for ITNs, where this is described in terms of price and coverage levels; and (2) What does the added cost of social marketing "buy" in terms of coverage and equity, compared with an unassisted commercial sector model? It appears that supply improved in both areas, although there was a greater increase in supply in the intervention area. However, the main impact of social marketing on the market for nets was to shift demand in the intervention district, leading to a higher coverage market outcome. While social marketing was more costly per net distributed than the unassisted commercial sector, higher overall levels of coverage were achieved in the social marketing area together with higher coverage of the lowest socioeconomic group, of pregnant women and children under 5 years, and of those living on the periphery of their villages. These findings are interpreted in the context of Tanzania's national plan for scaling up ITNs.

Larval application of sodium channel homologous dsRNA restores pyrethroid insecticide susceptibility in a resistant adult mosquito population.

PubMed

Bona, Ana Caroline Dalla; Chitolina, Rodrigo Faitta; Fermino, Marise Lopes; de Castro Poncio, Lisiane; Weiss, Avital; Lima, José Bento Pereira; Paldi, Nitzan; Bernardes, Emerson Soares; Henen, Jonathan; Maori, Eyal

2016-07-14

Mosquitoes host and pass on to humans a variety of disease-causing pathogens such as infectious viruses and other parasitic microorganisms. The emergence and spread of insecticide resistance is threatening the effectiveness of current control measures for common mosquito vector borne diseases, such as malaria, dengue and Zika. Therefore, the emerging resistance to the widely used pyrethroid insecticides is an alarming problem for public health. Herein we demonstrated the use of RNA interference (RNAi) to increase susceptibility of adult mosquitoes to a widely used pyrethroid insecticide. Experiments were performed on a field-collected pyrethroid resistant strain of Ae. aegypti (Rio de Janeiro; RJ). Larvae from the resistant Ae. aegypti population were soaked with double-stranded RNAs (dsRNAs) that correspond either to voltage-gate sodium channel (VGSC), P-glycoprotein, or P450 detoxification genes and reared to adulthood. Adult mortality rates in the presence of various Deltamethrin pyrethroid concentrations were used to assess mosquito insecticide susceptibility. We characterized the RJ Ae. aegypti strain with regard to its level of resistance to a pyrethroid insecticide and found that it was approximately 6 times more resistant to Deltamethrin compared to the laboratory Rockefeller strain. The RJ strain displayed a higher frequency of Val1016Ile and Phe1534Cys substitutions of the VGSC gene. The resistant strain also displayed a higher basal expression level of VGSC compared to the Rockefeller strain. When dsRNA-treated mosquitoes were subjected to a standard pyrethroid contact bioassay, only dsRNA targeting VGSC increased the adult mortality of the pyrethroid resistant strain. The dsRNA treatment proved effective in increasing adult mosquito susceptibility over a range of pyrethroid concentrations and these results were associated with dsRNA-specific small interfering RNAs in treated adults, and the corresponding specific down regulation of VGSC gene expression

Efficacy of topical mosquito repellent (picaridin) plus long-lasting insecticidal nets versus long-lasting insecticidal nets alone for control of malaria: a cluster randomised controlled trial.

PubMed

Sluydts, Vincent; Durnez, Lies; Heng, Somony; Gryseels, Charlotte; Canier, Lydie; Kim, Saorin; Van Roey, Karel; Kerkhof, Karen; Khim, Nimol; Mao, Sokny; Uk, Sambunny; Sovannaroth, Siv; Grietens, Koen Peeters; Sochantha, Tho; Menard, Didier; Coosemans, Marc

2016-10-01

Although effective topical repellents provide personal protection against malaria, whether mass use of topical repellents in addition to long-lasting insecticidal nets can contribute to a further decline of malaria is not known, particularly in areas where outdoor transmission occurs. We aimed to assess the epidemiological efficacy of a highly effective topical repellent in addition to long-lasting insecticidal nets in reducing malaria prevalence in this setting. A cluster randomised controlled trial was done in the 117 most endemic villages in Ratanakiri province, Cambodia, to assess the efficacy of topical repellents in addition to long-lasting insecticidal nets in controlling malaria in a low-endemic setting. We did a pre-trial assessment of village accessibility and excluded four villages because of their inaccessibility during the rainy season. Another 25 villages were grouped because of their proximity to each other, resulting in 98 study clusters (comprising either a single village or multiple neighbouring villages). Clusters were randomly assigned (1:1) to either a control (long-lasting insecticidal nets) or intervention (long-lasting insecticidal nets plus topical repellent) study group after a restricted randomisation. All clusters received one long-lasting insecticidal net per individual, whereas those in the intervention group also received safe and effective topical repellents (picaridin KBR3023, SC Johnson, Racine, WI, USA), along with instruction and promotion of its daily use. Cross-sectional surveys of 65 randomly selected individuals per cluster were done at the beginning and end of the malaria transmission season in 2012 and 2013. The primary outcome was Plasmodium species-specific prevalence in participants obtained by real-time PCR, assessed in the intention-to-treat population. Complete safety analysis data will be published seperately; any ad-hoc adverse events are reported here. This trial is registered with ClinicalTrials.gov, number NCT

Insecticide-treated nets and treatment service: a trial using public and private sector channels in rural United Republic of Tanzania.

PubMed Central

Fraser-Hurt, N.; Lyimo, E. O.

1998-01-01

The Rotary Net Initiative, implemented in Kilombero District, southern United Republic of Tanzania, allowed us to explore different sales channels for the distribution of insecticide-treated nets (ITNs) and the insecticide treatment service in a rural area of very high malaria transmission. Several types of ITNs were promoted and sold through different channels in the public and private sector, i.e. hospital pharmacy, mother and child health (MCH) clinic, net committee, village health workers and retail shops. The ITNs were sold for US$ 5.0-9.2, with profit margins of 9-16%. Net treatment cost US$ 0.33, with commission fees of 75%. Net transport and treatment were partially subsidized. Some outlets established their own fund by ITN sales. Sales of nets and treatments were seasonal, and certain net types were preferred. Demand for insecticide treatment was generally low. Changes in net coverage were assessed in two villages. A range of outlet features were compared qualitatively. Our experience supports suggestions that ITN technology should be delivered through MCH care services and demonstrates that specific promotion and innovation are necessary to achieve substantial net treatment levels. A large-scale ITN project in the same area and other ITN studies should lead to better understanding of ITN implementation at the population level. PMID:10191557

Discovery of Rigidified α,β-Unsaturated Imines as New Resistance-breaking Insecticides for Malaria Vector Control.

PubMed

Arlt, Alexander; Böhnke, Niels; Horstmann, Sebastian; Vermeer, Arnoldus W P; Werner, Stefan; Velten, Robert

2016-10-01

During our continuous search for new resistance-breaking insecticides applicable to malaria vector control, a new class of α,β-unsaturated imines was identified by applying the principle of conformational rigidification as a powerful tool for compound optimisation. Herein we describe the successful synthesis of these compounds and their biological test results. Our lead compound 16 from this insecticidal class outperforms market standards, notably for the control of mosquito strains that exhibit either metabolic or target-site resistance to these established insecticides. In our model system for insecticide-treated mosquito nets the compound reveals long-lasting efficacy for up to several months.

Insecticide susceptibility of Anopheles mosquitoes changes in response to variations in the larval environment.

PubMed

Owusu, Henry F; Chitnis, Nakul; Müller, Pie

2017-06-16

Insecticide resistance threatens the success achieved through vector control in reducing the burden of malaria. An understanding of insecticide resistance mechanisms would help to develop novel tools and strategies to restore the efficacy of insecticides. Although we have substantially improved our understanding of the genetic basis of insecticide resistance over the last decade, we still know little of how environmental variations influence the mosquito phenotype. Here, we measured how variations in larval rearing conditions change the insecticide susceptibility phenotype of adult Anopheles mosquitoes. Anopheles gambiae and A. stephensi larvae were bred under different combinations of temperature, population density and nutrition, and the emerging adults were exposed to permethrin. Mosquitoes bred under different conditions showed considerable changes in mortality rates and body weight, with nutrition being the major factor. Weight is a strong predictor of insecticide susceptibility and bigger mosquitoes are more likely to survive insecticide treatment. The changes can be substantial, such that the same mosquito colony may be considered fully susceptible or highly resistant when judged by World Health Organization discriminatory concentrations. The results shown here emphasise the importance of the environmental background in developing insecticide resistance phenotypes, and caution for the interpretation of data generated by insecticide susceptibility assays.

The Effect of Early Mosquito Insecticides Exposure on Spraque Dawley Rat Testis: A Histopathological Feature Towards Malignancy?

NASA Astrophysics Data System (ADS)

Indah Winarni, Tri; Auzan Aziman, Milzam; Abshar Andar, Anindyo; Pawitra, Ika

2017-02-01

The incidence of health problems associated with endocrine-disruption have increased. Many studies suggesting that endocrine disruptor chemicals (EDC) do contribute to cancer through estrogen-related receptors. Many chemicals have EDCs properties including insecticides. Early life exposure to EDCs can increased the risk of testicular cancer have been reported in the last decade. This study was aimed to determine the effect of insecticides exposure on histopathological tumor cell development of germ and Leydig cell. True experiment research design with posttest only control group design was applied. Sprague Dawley (SD) rat (n = 25) were randomly divided into 5 groups (control group, 25 mg β estradiol 3-benzoate, spiral mosquito coil repellent, 3 ml of liquid mosquito repellent, and 4 ml of liquid mosquito repellent). The exposure were administered for 20 days started at aged 3 days. At the age of 100 days (older adult), testis was stained using Hematoxyllin Eosin (HE) and histological features predicting malignancy were observed. The number of tumor cell development in both testicular germ cells and Leydig cells significantly increased in all treated group compared to those of control and the changes towards malignancy were also observed in all treated group. Exposure to mosquito insecticides causes significant changes in testicular germ and Leydig cell histological features that leads to malignancy.

Physical condition and maintenance of mosquito bed nets in Kwale County, coastal Kenya

PubMed Central

2013-01-01

Background Despite the extensive ownership and use of insecticide-treated nets (ITNs) over the last decade, the effective lifespan of these nets, especially their physical integrity, under true operational conditions is not well-understood. Usefulness of nets declines primarily due to physical damage or loss of insecticidal activity. Methods A community based cross-sectional survey was used to determine the physical condition and to identify predictors of poor physical condition for bed nets owned by individuals from communities in Kwale County, coastal Kenya. A proportionate hole index (pHI) was used as a standard measure, and the cut-offs for an ‘effective net’ (offer substantial protection against mosquito bites) and ‘ineffective nets’ (offer little or no protection against mosquito bites) were determined (pHI ≤88 (about ≤500 cm2 of holes surface area) and pHI of >88 (≥500 cm2 of holes surface area), respectively). Results The vast majority (78%) of the surveyed nets had some holes. The median pHI was 92 (range: 1–2,980). Overall, half of the nets were categorized as ‘effective nets’ or ‘serviceable nets’. Physical deterioration of nets was associated with higher use and washing frequency. Young children and older children were found to use ineffective bed nets significantly more often than infants, while the physical integrity of nets owned by pregnant women was similar to those owned by infants. Estuarine environment inhabitants owned nets with the worst physical condition, while nets owned by the coastal slope inhabitants were in fairly good physical condition. The results suggest that bed nets are optimally utilized when they are new and physically intact. Thereafter, bed net utilization decreases gradually with increasing physical deterioration, with most net owners withdrawing physically damaged nets from routine use. This withdrawal commonly happens following 1.5 years of use, making bed net use the most important predictor of

Permethrin induction of multiple cytochrome P450 genes in insecticide resistant mosquitoes, Culex quinquefasciatus.

PubMed

Gong, Youhui; Li, Ting; Zhang, Lee; Gao, Xiwu; Liu, Nannan

2013-01-01

The expression of some insect P450 genes can be induced by both exogenous and endogenous compounds and there is evidence to suggest that multiple constitutively overexpressed P450 genes are co-responsible for the development of resistance to permethrin in resistant mosquitoes. This study characterized the permethrin induction profiles of P450 genes known to be constitutively overexpressed in resistant mosquitoes, Culex quinquefasciatus. The gene expression in 7 of the 19 P450 genes CYP325K3v1, CYP4D42v2, CYP9J45, (CYP) CPIJ000926, CYP325G4, CYP4C38, CYP4H40 in the HAmCqG8 strain, increased more than 2-fold after exposure to permethrin at an LC50 concentration (10 ppm) compared to their acetone treated counterpart; no significant differences in the expression of these P450 genes in susceptible S-Lab mosquitoes were observed after permethrin treatment. Eleven of the fourteen P450 genes overexpressed in the MAmCqG6 strain, CYP9M10, CYP6Z12, CYP9J33, CYP9J43, CYP9J34, CYP306A1, CYP6Z15, CYP9J45, CYPPAL1, CYP4C52v1, CYP9J39, were also induced more than doubled after exposure to an LC50 (0.7 ppm) dose of permethrin. No significant induction in P450 gene expression was observed in the susceptible S-Lab mosquitoes after permethrin treatment except for CYP6Z15 and CYP9J39, suggesting that permethrin induction of these two P450 genes are common to both susceptible and resistant mosquitoes while the induction of the others are specific to insecticide resistant mosquitoes. These results demonstrate that multiple P450 genes are co-up-regulated in insecticide resistant mosquitoes through both constitutive overexpression and induction mechanisms, providing additional support for their involvement in the detoxification of insecticides and the development of insecticide resistance.

Evaluation of an automatic-timed insecticide application system for backyard mosquito control.

PubMed

Cilek, J E; Hallmon, C F; Johnson, R

2008-12-01

Several manufacturers and pest management companies have begun to market and install outdoor automatically timed insecticide application systems that claim to provide an envelope of protection against host-seeking mosquitoes within a defined area, e.g., residential backyards. A typical system consists of a multi-gallon reservoir attached to a continuous loop of plastic tubing with multiple single spray head nozzles. Nozzles are usually placed along the perimeter of a backyard in landscaping or other areas suitable for mosquito harborage. This array is then connected to a programmable electric pump set to automatically apply an insecticide at predetermined intervals. An operational field study was conducted to evaluate this technology using previously installed MistAway systems at.3 residences in northwestern Florida. This system applied a mist-like application of 0.05% AI synergized pyrethrins for 45 sec at dawn and again at dusk in each backyard. Twice-weekly collections from ABC suction light traps, baited with carbon dioxide, were used as the evaluation tool. Female mosquitoes from treatment backyards were compared with trap collections from 3 backyards without automatic misting systems used as controls. We found that weekly mosquito reduction was highly variable and ranged from 98% to 14% during the 35-wk study. Because the primary method of reduction by these application systems was not well understood, a MistAway system was installed in an outdoor simulated residential backyard to determine exposure pathway under controlled conditions with field cage and excised-leaf bioassays. Using laboratory-reared females of Aedes albopictus and Culex quinquefasciatus in those assays, we found that reduction by the MistAway system was primarily achieved by direct exposure of the mosquitoes to the insecticide application and not from residual deposits on treated vegetation.

Mass distribution of free insecticide-treated nets do not interfere with continuous net distribution in Tanzania

PubMed Central

2014-01-01

Background To protect the most vulnerable groups from malaria (pregnant women and infants) the Tanzanian Government introduced a subsidy (voucher) scheme in 2004, on the basis of a public-private partnership. These vouchers are provided to pregnant women at their first antenatal care visit and mothers of infants at first vaccination. The vouchers are redeemed at registered retailers for a long-lasting insecticidal net against the payment of a modest top-up price. The present work analysed a large body of data from the Tanzanian National Voucher Scheme, focusing on interactions with concurrent mass distribution campaigns of free nets. Methods In an ecologic study involving all regions of Tanzania, voucher redemption data for the period 2007 2011, as well as data on potential determinants of voucher redemption were analysed. The four outcome variables were: pregnant woman and infant voucher redemption rates, use of treated bed nets by all household members and by under- five children. Each of the outcomes was regressed with selected determinants, using a generalized estimating equation model and accounting for regional data clustering. Results There was a consistent improvement in voucher redemption rates over the selected time period, with rates >80% in 2011. The major determinants of redemption rates were the top-up price paid by the voucher beneficiary, the retailer- clinic ratio, and socio-economic status. Improved redemption rates after 2009 were most likely due to reduced top-up prices (following a change in policy). Redemption rates were not affected by two major free net distribution campaigns. During this period, there was a consistent improvement in net use across all the regions, with rates of up to 75% in 2011. Conclusion The key components of the National Treated Nets Programme (NATNETS) seem to work harmoniously, leading to a high level of net use in the entire population. This calls for the continuation of this effort in Tanzania and for emulation by

Mass distribution of free insecticide-treated nets do not interfere with continuous net distribution in Tanzania.

PubMed

Eze, Ikenna C; Kramer, Karen; Msengwa, Amina; Mandike, Renata; Lengeler, Christian

2014-05-27

To protect the most vulnerable groups from malaria (pregnant women and infants) the Tanzanian Government introduced a subsidy (voucher) scheme in 2004, on the basis of a public-private partnership. These vouchers are provided to pregnant women at their first antenatal care visit and mothers of infants at first vaccination. The vouchers are redeemed at registered retailers for a long-lasting insecticidal net against the payment of a modest top-up price. The present work analysed a large body of data from the Tanzanian National Voucher Scheme, focusing on interactions with concurrent mass distribution campaigns of free nets. In an ecologic study involving all regions of Tanzania, voucher redemption data for the period 2007-2011, as well as data on potential determinants of voucher redemption were analysed. The four outcome variables were: pregnant woman and infant voucher redemption rates, use of treated bed nets by all household members and by under- five children. Each of the outcomes was regressed with selected determinants, using a generalized estimating equation model and accounting for regional data clustering. There was a consistent improvement in voucher redemption rates over the selected time period, with rates >80% in 2011. The major determinants of redemption rates were the top-up price paid by the voucher beneficiary, the retailer- clinic ratio, and socio-economic status. Improved redemption rates after 2009 were most likely due to reduced top-up prices (following a change in policy). Redemption rates were not affected by two major free net distribution campaigns. During this period, there was a consistent improvement in net use across all the regions, with rates of up to 75% in 2011. The key components of the National Treated Nets Programme (NATNETS) seem to work harmoniously, leading to a high level of net use in the entire population. This calls for the continuation of this effort in Tanzania and for emulation by other countries with endemic malaria.

Role of cytochrome P450s in insecticide resistance: impact on the control of mosquito-borne diseases and use of insecticides on Earth.

PubMed

David, Jean-Philippe; Ismail, Hanafy Mahmoud; Chandor-Proust, Alexia; Paine, Mark John Ingraham

2013-02-19

The fight against diseases spread by mosquitoes and other insects has enormous environmental, economic and social consequences. Chemical insecticides remain the first line of defence but the control of diseases, especially malaria and dengue fever, is being increasingly undermined by insecticide resistance. Mosquitoes have a large repertoire of P450s (over 100 genes). By pinpointing the key enzymes associated with insecticide resistance we can begin to develop new tools to aid the implementation of control interventions and reduce their environmental impact on Earth. Recent technological advances are helping us to build a functional profile of the P450 determinants of insecticide metabolic resistance in mosquitoes. Alongside, the cross-responses of mosquito P450s to insecticides and pollutants are also being investigated. Such research will provide the means to produce diagnostic tools for early detection of P450s linked to resistance. It will also enable the design of new insecticides with optimized efficacy in different environments.

Role of cytochrome P450s in insecticide resistance: impact on the control of mosquito-borne diseases and use of insecticides on Earth

PubMed Central

David, Jean-Philippe; Ismail, Hanafy Mahmoud; Chandor-Proust, Alexia; Paine, Mark John Ingraham

2013-01-01

The fight against diseases spread by mosquitoes and other insects has enormous environmental, economic and social consequences. Chemical insecticides remain the first line of defence but the control of diseases, especially malaria and dengue fever, is being increasingly undermined by insecticide resistance. Mosquitoes have a large repertoire of P450s (over 100 genes). By pinpointing the key enzymes associated with insecticide resistance we can begin to develop new tools to aid the implementation of control interventions and reduce their environmental impact on Earth. Recent technological advances are helping us to build a functional profile of the P450 determinants of insecticide metabolic resistance in mosquitoes. Alongside, the cross-responses of mosquito P450s to insecticides and pollutants are also being investigated. Such research will provide the means to produce diagnostic tools for early detection of P450s linked to resistance. It will also enable the design of new insecticides with optimized efficacy in different environments. PMID:23297352

Pyrethroid resistance alters the blood-feeding behavior in Puerto Rican Aedes aegypti mosquitoes exposed to treated fabric

PubMed Central

Bloomquist, Jeffrey R.; Bernier, Ulrich R.

2017-01-01

Emerging insecticide resistance is a major issue for vector control. It decreases the effectiveness of insecticides, thereby requiring greater quantities for comparable control with a net increase in risk of disease resurgence, product cost, and damage risk to the ecosystem. Pyrethroid resistance has been documented in Puerto Rican populations of Aedes aegypti (L.) mosquitoes. In this study, topical toxicity of five insecticides (permethrin, etofenprox, deltamethrin, DDT, transfluthrin) was determined for susceptible (Orlando—ORL) and resistant (Puerto Rico—PR) strains of Ae. aegypti. Resistance ratios were calculated using LD50 values, and high resistance ratios for permethrin (112) and etofenprox (228) were observed for the Puerto Rico strain. Behavioral differences in blood-feeding activity for pyrethroid-resistant and pyrethroid-susceptible strains of Ae. aegypti when exposed to pyrethroid-treated cloth were also explored. Strains were exposed for 15 min to a range of concentrations of pyrethroid-treated uniform fabric in a cage that contained 60 female Ae. aegypti mosquitoes. Interestingly, the resistance ratios for blood-feeding were similar for permethrin (61) and etofenprox (70), but were lower than their respective resistance ratios for topical toxicity, suggesting that knockdown resistance was the primary mechanism of resistance in the blood feeding assays. Results showed a rightward shift in the dose-response curves for blood-feeding that indicated higher concentrations of pyrethroids were necessary to deter blood-feeding behavior in the pyrethroid-resistant Puerto Rican strain of Ae. aegypti. PMID:28931018

Africa's largest long-lasting insecticide-treated net producer: lessons from A to Z Textiles.

PubMed

Masum, Hassan; Shah, Ronak; Schroeder, Karl; Daar, Abdallah S; Singer, Peter A

2010-12-13

Field trials have demonstrated the efficacy of insecticide-treated nets, and the WHO has recently endorsed a shift toward Long-Lasting Insecticide Treated nets (LLINs) due to factors such as reduced distribution costs. However, the need for LLINs poses several challenges. Is it possible to manufacture LLINs in large quantities in the African continent, where malaria is most endemic? When production is located in low-income countries, what role is played by local funding and employment, scaling up manufacturing, and partnerships? What factors influence availability and pricing? A case study of A to Z Textiles was undertaken to answer the question of how large-scale production of LLINs can occur in a low income setting. One of the largest sources of bed nets for Africa, A to Z Textiles is Africa-based, and its Tanzanian operations have a production capacity of 30 million LLINs per year, along with full WHO recommendation for its nets. Our analysis is based on semi-structured interviews with key informants familiar with A to Z, site visits in Tanzania, and literature reviews.This paper discusses the history and current status of A to Z Textiles, identifies the factors that led to its success, and suggests policy considerations that could support similar initiatives in the future. Local funding, scaling up manufacturing, technology transfer, and partnerships all played important roles in A to Z's ascent, as did perceived benefits of local employment and capacity-building. Regulatory issues and procurement rules acted as barriers. A to Z cost-effectively manufactures high-quality LLINs where malaria is most endemic. With a production capacity of 30 million LLINs per year, and full WHOPES (WHO Pesticide Evaluation Scheme) certification, A to Z Textiles demonstrates how key health goods can be successfully produced in the low-income countries that use them. Its example may be instructive and of high interest to readers in the malaria community, especially in developing

Evaluating the efficacy of biological and conventional insecticides with the new 'MCD bottle' bioassay.

PubMed

Sternberg, Eleanore D; Waite, Jessica L; Thomas, Matthew B

2014-12-16

Control of mosquitoes requires the ability to evaluate new insecticides and to monitor resistance to existing insecticides. Monitoring tools should be flexible and low cost so that they can be deployed in remote, resource poor areas. Ideally, a bioassay should be able to simulate transient contact between mosquitoes and insecticides, and it should allow for excito-repellency and avoidance behaviour in mosquitoes. Presented here is a new bioassay, which has been designed to meet these criteria. This bioassay was developed as part of the Mosquito Contamination Device (MCD) project and, therefore, is referred to as the MCD bottle bioassay. Presented here are two experiments that serve as a proof-of-concept for the MCD bottle bioassay. The experiments used four insecticide products, ranging from fast-acting, permethrin-treated, long-lasting insecticide nets (LLINs) that are already widely used for malaria vector control, to the slower acting entomopathogenic fungus, Beauveria bassiana, that is currently being evaluated as a prospective biological insecticide. The first experiment used the MCD bottle to test the effect of four different insecticides on Anopheles stephensi with a range of exposure times (1 minute, 3 minutes, 1 hour). The second experiment is a direct comparison of the MCD bottle and World Health Organization (WHO) cone bioassay that tests a subset of the insecticides (a piece of LLIN and a piece of netting coated with B. bassiana spores) and a further reduced exposure time (5 seconds) against both An. stephensi and Anopheles gambiae. Immediate knockdown and mortality after 24 hours were assessed using logistic regression and daily survival was assessed using Cox proportional hazards models. Across both experiments, fungus performed much more consistently than the chemical insecticides but measuring the effect of fungus required monitoring of mosquito mortality over several days to a week. Qualitatively, the MCD bottle and WHO cone performed comparably

Factors associated with the use of mosquito bed nets: results from two cross-sectional household surveys in Zambézia Province, Mozambique.

PubMed

Moon, Troy D; Hayes, Caleb B; Blevins, Meridith; Lopez, Melanie L; Green, Ann F; González-Calvo, Lazaro; Olupona, Omo

2016-04-11

Malaria remains a major threat to some 3.2 billion persons globally. Malaria contributes heavily to the overall disease burden in Mozambique and is considered endemic. A cornerstone of Mozambique's vector control strategy has been to strive for universal coverage of insecticide-treated nets (ITN). The study is a population-based cross-sectional survey of female heads-of-household in Zambézia Province, Mozambique conducted during August-September, 2010 and April-May, 2014. Analyses accounted for a stratified two-stage cluster sample design. Outcomes of interest included sleeping under a mosquito net during the previous night. Descriptive statistics were calculated for three oversampled districts and for the entire province. Multivariable logistic regression analysis was used to estimate factors associated with both changes over time and increased mosquito bed net usage. Of the 3916 households interviewed in 2010 and 3906 households in 2014, 64.3% were in possession of at least one mosquito bed net. A higher proportion of households in Namacurra (90%) reported possession of a mosquito net, compared to Alto Molócuè (77%) and Morrumbala (34%), respectively in 2014. Of pregnant respondents, 58.6% reported sleeping under a mosquito net the previous night in 2010 compared to 68.4% in 2014. Fifty percent of children 0-59 months slept under a mosquito net the previous night in 2010 compared to 60% in 2014. Factors associated with use of a mosquito net for female head-of-household respondents were higher education, understanding Portuguese, larger household size, having electricity in the household, and larger household monthly income. As travel time to a health facility increased (per 1 h), respondents had 13% lower odds of sleeping under a mosquito net (OR 0.87; 95% CI 0.74-1.01, p = 0.07). Pregnant women in 2014 had a 2.4 times higher odds of sleeping under a bed net if they lived in Namacurra compared to Alto Molócuè (95% CI 0.91-6.32, p = 0.002 for district

Comparison of the Laboratory Standard Washing Using CIPAC Washing Agent and the Domestic Washing on Three Recommended Types of Long-Lasting Insecticidal Mosquito Nets

PubMed Central

Ouattara, Jean Pierre Nabléni; Louwagie, Johanna; Pigeon, Olivier; Spanoghe, Pieter

2013-01-01

Background One of the best ways to prevent malaria is the use of insecticide-treated bed nets. Manufacturers pursue easier, safer and more efficient nets. Hence, many studies on the efficacy and wash resistance using World Health Organization standards have been reported. The commonly used detergent is “Savon de Marseille”, because it closely resembles actually used soaps. At the 54th Collaborative International Pesticides Analytical Council (CIPAC) Technical Meeting in 2010, it was suggested to replace it by a standardized “CIPAC washing agent”. The aim of this study was to investigate the difference between a laboratory hand washing simulation using the CIPAC washing agent (method-1) and a domestic washing (method-2) on different bed nets, as well as the effect of the drying process on the release of active ingredient. Methods Interceptor®, Permanet®2.0 and Netprotect® nets were used in three treatments, each repeated 20 times. The first treatment included method-1 washing and indoor drying. The second treatment included method-2 washing and indoor drying. The third treatment used method-2 washing and UV-drying. The residual insecticide contents were determined using gas chromatography. Results The washing procedure and the number of washes have a significant effect on the release of active ingredient. Statistically, the two washing methods have the same effect on removing the active ingredient from the Interceptor® and Permanet®2.0 net, but a significantly different influence on the Netprotect® nets. The drying process has no significant effect on the insecticide. Conclusion Both washing procedures affected the amount of insecticide remaining on nets independently of the impregnation technology. The active ingredient decreases with the number of washing cycles following an exponential or logarithmic model for coated nets. The laboratory hand washing simulation had more impact on the decrease of active ingredient content of the Netprotect® nets

Synergism between permethrin and propoxur against Culex quinquefasciatus mosquito larvae.

PubMed

Corbel, V; Chandre, F; Darriet, F; Lardeux, F; Hougard, J-M

2003-06-01

To see if synergism occurs between carbamate and pyrethroid insecticides, we tested permethrin and propoxur as representatives of these two classes of compounds used for mosquito control. Larvicidal activity of both insecticides was assessed separately and together on a susceptible strain of the mosquito Culex quinquefasciatus (Diptera: Culicidae) by two methods. When mixed at a constant ratio (permethrin : propoxur 1 : 60 based on LC50) and tested at serial concentrations to plot dose/mortality regression, significant synergy occurred between them (co-toxicity coefficient = 2.2), not just an additive effect. For example, when the mixture gave 50% mortality, the same concentrations of permethrin and propoxur alone would have given merely 2 x 1% mortality. When a sublethal dose (LC0) of permethrin or propoxur was added to the other (range LC10-LC95), synergism occurred up to the LC80 level. Synergistic effects were attributed to the complementary modes of action by these two insecticide classes acting on different components of nerve impulse transmission. Apart from raising new possibilities for Culex control, it seems appropriate to consider using such mixtures or combinations for insecticide-treated mosquito nets in situations with insecticide-resistant Anopheles malaria vectors.

Impact of insecticide-treated bed nets on malaria transmission indices on the south coast of Kenya

PubMed Central

2011-01-01

Background Besides significantly reducing malaria vector densities, prolonged usage of bed nets has been linked to decline of Anopheles gambiae s.s. relative to Anopheles arabiensis, changes in host feeding preference of malaria vectors, and behavioural shifts to exophagy (outdoor biting) for the two important malaria vectors in Africa, An. gambiae s.l. and Anopheles funestus. In southern coastal Kenya, bed net use was negligible in 1997-1998 when Anopheles funestus and An. gambiae s.s. were the primary malaria vectors, with An. arabiensis and Anopheles merus playing a secondary role. Since 2001, bed net use has increased progressively and reached high levels by 2009-2010 with corresponding decline in malaria transmission. Methods To evaluate the impact of the substantial increase in household bed net use within this area on vector density, vector composition, and human-vector contact, indoor and outdoor resting mosquitoes were collected in the same region during 2009-2010 using pyrethrum spray catches and clay pots for indoor and outdoor collections respectively. Information on bed net use per sleeping spaces and factors influencing mosquito density were determined in the same houses using Poisson regression analysis. Species distribution was determined, and number of mosquitoes per house, human-biting rates (HBR), and entomological inoculation rate (EIR) were compared to those reported for the same area during 1997-1998, when bed net coverage had been minimal. Results Compared to 1997-1998, a significant decline in the relative proportion of An. gambiae s.s. among collected mosquitoes was noted, coupled with a proportionate increase of An. arabiensis. Following > 5 years of 60-86% coverage with bed nets, the density, human biting rate and EIR of indoor resting mosquitoes were reduced by more than 92% for An. funestus and by 75% for An. gambiae s.l. In addition, the host feeding choice of both vectors shifted more toward non-human vertebrates. Besides bed net use

Pyrethroid insecticides maintain repellent effect on knock-down resistant populations of Aedes aegypti mosquitoes.

PubMed

Bowman, Natalie M; Akialis, Kristin; Cave, Grayson; Barrera, Roberto; Apperson, Charles S; Meshnick, Steven R

2018-01-01

Pyrethroid-treated clothing is commonly worn for protection against mosquitoes; pyrethroids are both insecticides and repellents. Pyrethroid resistance has become increasingly common in Aedes aegypti, the vector of dengue, Zika, and other arboviruses, but it is not clear whether resistance is associated with reductions in repellency. In order to determine whether long-lasting permethrin impregnated (LLPI) clothing is protective, we used Aedes aegypti from New Orleans, LA (pyrethroid-sensitive) and San Juan, PR (resistant) to measure both lethality and repellency. PCR and Sanger sequencing were used to confirm resistance status by detecting mutations in the kdr gene at positions 1016 and 1534. Arm-in-cage trials of 100 Aedes aegypti females from both populations were performed for 10 minutes to bare arm or an arm clothed in untreated military camouflage or military camouflage impregnated with deltamethrin, permethrin, or etofenprox. Trials were repeated 4-5 times on different days. Number of landings, number of blood meals, and immediate and 24-hour mortality were recorded. Mortality was extremely low in all trials. Compared to untreated cloth, mosquitoes demonstrated a trend towards a 2%-63% reduction in landings and a statistically significant 78-100% reduction in blood feeding on pyrethroid-treated cloth for most insecticides. Effects were observed in both pyrethroid-sensitive and pyrethroid-resistant mosquito populations. Our data show that kdr mutations are associated with pyrethroid resistance but are likely not the only contributors. Pyrethroids appear to maintain repellent effect against resistant mosquitoes. This finding suggests that even in places where pyrethroid resistance is widespread, permethrin still has a role for use as a repellent on clothing to protect against mosquito bites.

Plant based insect repellent and insecticide treated bed nets to protect against malaria in areas of early evening biting vectors: double blind randomised placebo controlled clinical trial in the Bolivian Amazon.

PubMed

Hill, N; Lenglet, A; Arnéz, A M; Carneiro, I

2007-11-17

To determine the effectiveness in reducing malaria of combining an insect repellent with insecticide treated bed nets compared with the nets alone in an area where vector mosquitoes feed in the early evening. A double blind, placebo controlled cluster-randomised clinical study. Rural villages and peri-urban districts in the Bolivian Amazon. 4008 individuals in 860 households. All individuals slept under treated nets; one group also used a plant based insect repellent each evening, a second group used placebo. Episodes of Plasmodium falciparum or P vivax malaria confirmed by rapid diagnostic test or blood slide, respectively. We analysed 15,174 person months at risk and found a highly significant 80% reduction in episodes of P vivax in the group that used treated nets and repellent (incidence rate ratio 0.20, 95% confidence interval 0.11 to 0.38, P<0.001). Numbers of P falciparum cases during the study were small and, after adjustment for age, an 82% protective effect was observed, although this was not significant (0.18, 0.02 to 1.40, P=0.10). Reported episodes of fever with any cause were reduced by 58% in the group that used repellent (0.42, 0.31 to 0.56, P<0.001). Insect repellents can provide protection against malaria. In areas where vectors feed in the early evening, effectiveness of treated nets can be significantly increased by using repellent between dusk and bedtime. This has important implications in malaria vector control programmes outside Africa and shows that the combined use of treated nets and insect repellents, as advocated for most tourists travelling to high risk areas, is fully justified. NCT 00144716.

Repellent and insecticidal efficacy of a new combination of fipronil and permethrin against three mosquito species (Aedes albopictus, Aedes aegypti and Culex pipiens) on dogs.

PubMed

Fankhauser, Becky; Dumont, Pascal; Hunter, James S; McCall, John W; Kaufmann, Christian; Mathis, Alexander; Young, David R; Carroll, Scott P; McCall, Scott; Chester, S Theodore; Soll, Mark D

2015-01-30

Three laboratory studies were conducted to assess the repellent and insecticidal efficacy of a combination of fipronil and permethrin (Frontline Tri- Act/Frontect) against three mosquito species (Aedes albopictus, Aedes aegypti and Culex pipiens) on dogs. In each study, 16 healthy adult dogs were allocated to two groups. Eight dogs were treated with the new topical spot-on combination of fipronil and permethrin on Day 0 and the other eight dogs served as untreated controls. Each dog was exposed to mosquitoes on Days 1, 7, 14, 21 and 28 (and also on Day 35 in the A. aegypti study). After a 1-h exposure period, all mosquitoes were counted and categorized as live or dead and fed or non-fed. Live mosquitoes were kept in an insectary and observed for mortality counts 4, 24 and 48 h post-exposure (PE) for Aedes spp. and 24 and 48 h PE for C. pipiens. Repellency and insecticidal efficacies were defined as the percent reduction in the number of fed and live mosquitoes, respectively, in the treated group as compared to the untreated control group. Repellency against A. albopictus was ≥93.4% through Day 21 and 86.9% on Day 28. It was ≥91.0% through Day 35 against A. aegypti and ≥90.4% through Day 28 against C. pipiens. Insecticidal efficacy against A. albopictus was ≥97.1% at 24 h PE from Day 7 to Day 28. It was ≥98.0% for the first 3 weeks and still 75.7% on Day 35 against A. aegypti at 24 h PE. For C. pipiens, insecticidal efficacy ranged from 93.8% (Day 7) to 30.9% (Day 28) at 48 h PE. A single topical administration of the combination of fipronil and permethrin provides repellency against mosquitoes on dogs for at least 4 weeks. The product may therefore significantly reduce the potential for the transmission of vector-borne pathogens through the inhibition of mosquito feeding, as well as the discomfort associated with mosquito bites. Moreover, mosquito mortality was induced by contact with the treated dogs, which could aid in the control of mosquitoes, and

The costs and effects of a nationwide insecticide-treated net programme: the case of Malawi

PubMed Central

Stevens, Warren; Wiseman, Virginia; Ortiz, Juan; Chavasse, Desmond

2005-01-01

Background Insecticide-treated nets (ITNs) are a proven intervention to reduce the burden of malaria, yet there remains a debate as to the best method of ensuring they are universally utilized. This study is a cost-effectiveness analysis of an intervention in Malawi that started in 1998, in Blantyre district, before expanding nationwide. Over the 5-year period, 1.5 million ITNs were sold. Methods The costs were calculated retrospectively through analysis of expenditure data. Costs and effects were measured as cost per treated-net year (cost/TNY) and cost per net distributed. Results The mean cost/TNY was calculated at $4.41, and the mean cost/ITN distributed at $2.63. It also shows evidence of economies of scale, with the cost/TNY falling from $7.69 in year one (72,196 ITN) to $3.44 in year five (720,577 ITN). Cost/ITN distributed dropped from $5.04 to $1.92. Conclusion Combining targeting and social marketing has the potential of being both cost-effective and capable of achieving high levels of coverage, and it is possible that increasing returns to scale can be achieved. PMID:15885143

Reduced Insecticide Susceptibility in Aedes vexans (Diptera: Culicidae) Where Agricultural Pest Management Overlaps With Mosquito Abatement.

PubMed

Dunbar, Mike W; Bachmann, Amanda; Varenhorst, Adam J

2018-05-04

Mosquito abatement programs in Midwestern communities frequently exist within landscapes dominated by agriculture. Although separately managed, both agricultural pests and mosquitoes are targeted by similar classes of insecticides. As a result, there is the potential for unintended insecticide exposure to mosquito populations from agricultural pest management. To determine the impact that agricultural management practices have on mosquito insecticide susceptibility we compared the mortality of Aedes vexans (Meigen; Diptera: Culicidae) between populations sampled from locations with and without mosquito abatement in South Dakota, a region dominated by agricultural production. Collection locations were either within towns with mosquito abatement programs (n = 2; Brookings and Sioux Falls, SD) or located > 16 km from towns with mosquito abatement programs (n = 2; areas near Harrold and Willow Lake, SD). WHO bioassays were used to test susceptibly of adults to differing insecticide classes relative to their respective controls; 1) an organochlorine (dieldrin 4%), 2) an organophosphate (malathion 5%), and 3) a pyrethroid (lambda-cyhalothrin 0.05%). Corrected mortality did not significantly differ between locations with or without abatement; however, when locations were analized by proportion of developed land within the surrounding landscape pyrethroid mortality was significantly lower where crop production dominated the surrounding landscape and mosquito abatement was present. These data suggest that agricultural pest management may incidentally contribute to reduced mosquito susceptibility where overlap between agricultural pest management and mosquito abatement exists. Decoupling insecticide classes used by both agricultural and public health pest management programs may be necessary to ensure continued efficacy of pest management tools.

Planning long lasting insecticide treated net campaigns: should households’ existing nets be taken into account?

PubMed Central

2013-01-01

Background Mass distribution of long-lasting insecticide treated bed nets (LLINs) has led to large increases in LLIN coverage in many African countries. As LLIN ownership levels increase, planners of future mass distributions face the challenge of deciding whether to ignore the nets already owned by households or to take these into account and attempt to target individuals or households without nets. Taking existing nets into account would reduce commodity costs but require more sophisticated, and potentially more costly, distribution procedures. The decision may also have implications for the average age of nets in use and therefore on the maintenance of universal LLIN coverage over time. Methods A stochastic simulation model based on the NetCALC algorithm was used to determine the scenarios under which it would be cost saving to take existing nets into account, and the potential effects of doing so on the age profile of LLINs owned. The model accounted for variability in timing of distributions, concomitant use of continuous distribution systems, population growth, sampling error in pre-campaign coverage surveys, variable net ‘decay’ parameters and other factors including the feasibility and accuracy of identifying existing nets in the field. Results Results indicate that (i) where pre-campaign coverage is around 40% (of households owning at least 1 LLIN), accounting for existing nets in the campaign will have little effect on the mean age of the net population and (ii) even at pre-campaign coverage levels above 40%, an approach that reduces LLIN distribution requirements by taking existing nets into account may have only a small chance of being cost-saving overall, depending largely on the feasibility of identifying nets in the field. Based on existing literature the epidemiological implications of such a strategy is likely to vary by transmission setting, and the risks of leaving older nets in the field when accounting for existing nets must be considered

Planning long lasting insecticide treated net campaigns: should households' existing nets be taken into account?

PubMed

Yukich, Joshua; Bennett, Adam; Keating, Joseph; Yukich, Rudy K; Lynch, Matt; Eisele, Thomas P; Kolaczinski, Kate

2013-06-14

Mass distribution of long-lasting insecticide treated bed nets (LLINs) has led to large increases in LLIN coverage in many African countries. As LLIN ownership levels increase, planners of future mass distributions face the challenge of deciding whether to ignore the nets already owned by households or to take these into account and attempt to target individuals or households without nets. Taking existing nets into account would reduce commodity costs but require more sophisticated, and potentially more costly, distribution procedures. The decision may also have implications for the average age of nets in use and therefore on the maintenance of universal LLIN coverage over time. A stochastic simulation model based on the NetCALC algorithm was used to determine the scenarios under which it would be cost saving to take existing nets into account, and the potential effects of doing so on the age profile of LLINs owned. The model accounted for variability in timing of distributions, concomitant use of continuous distribution systems, population growth, sampling error in pre-campaign coverage surveys, variable net 'decay' parameters and other factors including the feasibility and accuracy of identifying existing nets in the field. Results indicate that (i) where pre-campaign coverage is around 40% (of households owning at least 1 LLIN), accounting for existing nets in the campaign will have little effect on the mean age of the net population and (ii) even at pre-campaign coverage levels above 40%, an approach that reduces LLIN distribution requirements by taking existing nets into account may have only a small chance of being cost-saving overall, depending largely on the feasibility of identifying nets in the field. Based on existing literature the epidemiological implications of such a strategy is likely to vary by transmission setting, and the risks of leaving older nets in the field when accounting for existing nets must be considered. Where pre-campaign coverage

Africa's largest long-lasting insecticide-treated net producer: lessons from A to Z Textiles

PubMed Central

2010-01-01

Background Field trials have demonstrated the efficacy of insecticide-treated nets, and the WHO has recently endorsed a shift toward Long-Lasting Insecticide Treated nets (LLINs) due to factors such as reduced distribution costs. However, the need for LLINs poses several challenges. Is it possible to manufacture LLINs in large quantities in the African continent, where malaria is most endemic? When production is located in low-income countries, what role is played by local funding and employment, scaling up manufacturing, and partnerships? What factors influence availability and pricing? Discussion A case study of A to Z Textiles was undertaken to answer the question of how large-scale production of LLINs can occur in a low income setting. One of the largest sources of bed nets for Africa, A to Z Textiles is Africa-based, and its Tanzanian operations have a production capacity of 30 million LLINs per year, along with full WHO recommendation for its nets. Our analysis is based on semi-structured interviews with key informants familiar with A to Z, site visits in Tanzania, and literature reviews. This paper discusses the history and current status of A to Z Textiles, identifies the factors that led to its success, and suggests policy considerations that could support similar initiatives in the future. Local funding, scaling up manufacturing, technology transfer, and partnerships all played important roles in A to Z’s ascent, as did perceived benefits of local employment and capacity-building. Regulatory issues and procurement rules acted as barriers. A to Z cost-effectively manufactures high-quality LLINs where malaria is most endemic. Summary With a production capacity of 30 million LLINs per year, and full WHOPES (WHO Pesticide Evaluation Scheme) certification, A to Z Textiles demonstrates how key health goods can be successfully produced in the low-income countries that use them. Its example may be instructive and of high interest to readers in the malaria

Use and effectiveness of commercial flit-spray insecticides in control of mosquito population in Sagamu, Southwest Nigeria.

PubMed

Adedeji, A A; Ahmed, I A; Akinwunmi, M; Aina, S A; Tikare, O; Adeboye, A F; Badmos, S O; Adedeji, K A; Fehintola, F A; Amoo, A O J

2012-06-01

Control of mosquito vector is crucial to reducing the burden of malaria in endemic region. In the present study, we investigated the use of commercial insecticides in families and their effectiveness in control of mosquito population in Sagamu, southwest Nigeria. A pretested structured questionnaire was used to determine mosquito adulticides techniques employed in the community and most commonly used adulticides were evaluated for effectiveness by exposing adult mosquitoes to varying concentrations of the insecticides and responses monitored. Families differ in methods adopted to prevent mosquito and use of flit-spray insecticide was commoner. Although parents constitute 64% of those applying the insecticide, 22.2% were children. Household pyrethroid insecticide products of Baygon (Imiprothrin, Prallethrin plus Cyfluthrin), Mobil (Neopynamin, Prallethrin plus Cyphenothrin) and Raid (Pynamin forte, Neopynamin plus Deltimethrin) were three commonly used in the community. The exposure tie interval for eath of osquitoes was shorter with Raid (100% at 8 minutes) when compared with Mobil (80%) and Baygon (85%) at 10 minutes (p = 0.005). Kaplan-Meier survival curve of cumulative probability of surviving exposure to insecticide was lowest with Raid (log rank 2 = 14.56, P = 0.001). Although flit-spray insecticides are affordable with simple application tool, inexplicit use-instruction on labels may cause discrepancies in application. Monitoring responses of mosquitoes to commercial flit-spray insecticide may support effective control technique and prevention of vector resistance in poor resource communities.

Patterns of phenoloxidase activity in insecticide resistant and susceptible mosquitoes differ between laboratory-selected and wild-caught individuals.

PubMed

Cornet, Stéphane; Gandon, Sylvain; Rivero, Ana

2013-10-31

Insecticide resistance has the potential to alter vector immune competence and consequently affect the transmission of diseases. Using both laboratory isogenic strains and field-caught Culex pipiens mosquitoes, we investigated the effects of insecticide resistance on an important component of the mosquito immune system: the phenoloxidase (PO) activity. As infection risk varies dramatically with the age and sex of mosquitoes, allocation to PO immunity was quantified across different stages of the mosquito life cycle. Our results were consistent in showing that larvae have a higher PO activity than adults, females have a higher PO activity than males, and PO activity declines with adult age. We obtained, however, a marked discrepancy between laboratory and field-collected mosquitoes on the effect of insecticide resistance on PO activity. In the laboratory selected strains we found evidence of strong interactions between insecticide resistance and the age and sex of mosquitoes. In particular, 7 and 14 day old esterase-resistant adult females and acetylcholine-esterase resistant males had significantly higher PO activities than their susceptible counterparts. No such effects were, however, apparent in field-caught mosquitoes. Combined, the field and laboratory-based approaches employed in this study provide a powerful test of the effect of insecticide resistance on PO-mediated immunity. The use of laboratory-selected insecticide-resistant strains is still the most widely used method to investigate the pleiotropic effects of insecticide resistance. Our results suggest that the outcome of these laboratory-selected mosquitoes must be interpreted with caution and, whenever possible, compared with mosquitoes captured from the field.

Insecticidal, acaricidal and repellent effects of DEET- and IR3535-impregnated bed nets using a novel long-lasting polymer-coating technique.

PubMed

Faulde, Michael K; Albiez, Gunther; Nehring, Oliver

2010-03-01

A novel long-lasting repellent-treated net (LLRTN) has been designed by binding the skin repellents N,N-diethyl-m-toluamide (DEET), or IR3535, onto the fibres of bed net fabric using a new polymer-coating technique. The repellent toxicological effectiveness and residual activity of a factory-based repellent-impregnated fabric has been evaluated by laboratory testing against adult Aedes aegypti mosquitoes and nymphal Ixodes ricinus ticks. By using this repellent-embedding impregnation technique, concentrations exceeding 10 g/m(2) could be achieved with one single polymer layer. Both DEET- and IR3535-impregnated fabrics revealed a dose-dependent insecticidal as well as acaricidal activity. One hundred percent knockdown times of DEET-treated bed nets ranged from 187.5 +/- 31.8 to 27.5 +/- 3.5 min against A. aegypti, and between 214 +/- 47 and 22.6 +/- 5 min against nymphal I. ricinus, linked to a DEET concentration of 1.08 and 10.58 g/m(2), respectively. With IR3535, A. aegypti produced dose-dependent 100% knockdown times varying from 87.5 +/- 10.6 to 57.5 +/- 3.5 min and between 131.4 +/- 6.5 and 33.8 +/- 5 min against nymphal I. ricinus, respectively, linked to concentrations between 1.59 and 10.02 g/m(2). One hundred percent repellency measured by complete landing and biting protection of impregnated fabric by using the arm-in-cage test could be achieved at DEET concentrations exceeding 3.7 to 3.9 g/m(2), and for IR3535 concentrations over 10 g/m(2). One hundred percent landing and biting protection could be preserved with DEET-treated fabrics for 29 weeks at an initial concentration of 4.66 g/m(2), 54 weeks at 8.8 g/m(2), 58 weeks at 9.96 g/m(2) and 61 weeks at 10.48 g/m(2) for DEET, and 23 weeks for IR3535-treated fabric at a concentration of 10.02 g/m(2). Unlike repellent-treated fabric, a brand of a commercially available long-lasting insecticide-treated net tested containing 500 mg permethrin/m(2) did not protect from mosquito bites. First results on

Using adult mosquitoes to transfer insecticides to Aedes aegypti larval habitats

PubMed Central

Devine, Gregor J.; Perea, Elvira Zamora; Killeen, Gerry F.; Stancil, Jeffrey D.; Clark, Suzanne J.; Morrison, Amy C.

2009-01-01

Vector control is a key means of combating mosquito-borne diseases and the only tool available for tackling the transmission of dengue, a disease for which no vaccine, prophylaxis, or therapeutant currently exists. The most effective mosquito control methods include a variety of insecticidal tools that target adults or juveniles. Their successful implementation depends on impacting the largest proportion of the vector population possible. We demonstrate a control strategy that dramatically improves the efficiency with which high coverage of aquatic mosquito habitats can be achieved. The method exploits adult mosquitoes as vehicles of insecticide transfer by harnessing their fundamental behaviors to disseminate a juvenile hormone analogue (JHA) between resting and oviposition sites. A series of field trials undertaken in an Amazon city (Iquitos, Peru) showed that the placement of JHA dissemination stations in just 3–5% of the available resting area resulted in almost complete coverage of sentinel aquatic habitats. More than control mortality occurred in 95–100% of the larval cohorts of Aedes aegypti developing at those sites. Overall reductions in adult emergence of 42–98% were achieved during the trials. A deterministic simulation model predicts amplifications in coverage consistent with our observations and highlights the importance of the residual activity of the insecticide for this technique. PMID:19561295

Field efficacy of a new mosaic long-lasting mosquito net (PermaNet® 3.0) against pyrethroid-resistant malaria vectors: a multi centre study in Western and Central Africa

PubMed Central

2010-01-01

Background Due to the spread of pyrethroid-resistance in malaria vectors in Africa, new strategies and tools are urgently needed to better control malaria transmission. The aim of this study was to evaluate the performances of a new mosaic long-lasting insecticidal net (LLIN), i.e. PermaNet® 3.0, against wild pyrethroid-resistant Anopheles gambiae s.l. in West and Central Africa. Methods A multi centre experimental hut trial was conducted in Malanville (Benin), Vallée du Kou (Burkina Faso) and Pitoa (Cameroon) to investigate the exophily, blood feeding inhibition and mortality induced by PermaNet® 3.0 (i.e. a mosaic net containing piperonyl butoxide and deltamethrin on the roof) comparatively to the WHO recommended PermaNet® 2.0 (unwashed and washed 20-times) and a conventionally deltamethrin-treated net (CTN). Results The personal protection and insecticidal activity of PermaNet 3.0 and PermaNet® 2.0 were excellent (>80%) in the "pyrethroid-tolerant" area of Malanville. In the pyrethroid-resistance areas of Pitoa (metabolic resistance) and Vallée du Kou (presence of the L1014F kdr mutation), PermaNet® 3.0 showed equal or better performances than PermaNet® 2.0. It should be noted however that the deltamethrin content on PermaNet® 3.0 was up to twice higher than that of PermaNet® 2.0. Significant reduction of efficacy of both LLIN was noted after 20 washes although PermaNet® 3.0 still fulfilled the WHO requirement for LLIN. Conclusion The use of combination nets for malaria control offers promising prospects. However, further investigations are needed to demonstrate the benefits of using PermaNet® 3.0 for the control of pyrethroid resistant mosquito populations in Africa. PMID:20423479

Can insecticide-treated netting provide protection for Equids from Culicoides biting midges in the United Kingdom?

PubMed

Baker, Tiffany; Carpenter, Simon; Gubbins, Simon; Newton, Richard; Lo Iacono, Giovanni; Wood, James; Harrup, Lara Ellen

2015-11-25

Biting midges of the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae) cause a significant biting nuisance to equines and are responsible for the biological transmission of African horse sickness virus (AHSV). While currently restricted in distribution to sub-Saharan Africa, AHSV has a history of emergence into southern Europe and causes one of the most lethal diseases of horses and other species of Equidae. In the event of an outbreak of AHSV, the use of insecticide treated nets (ITNs) to screen equine accomodation is recommended by competent authorities including the Office International des Épizooties (OIE) in order to reduce vector-host contact. Seven commercially avaliable pyrethroid insecticides and three repellent compounds, all of which are licensed for amateur use, were assessed in modified World Health Organization (WHO) cone bioassay trials in the laboratory using a colony line of Culicoides nubeculosus (Meigen), 1830. Two field trials were subsequently conducted to test the efficiency of treated net screens in preventing entry of Culicoides. A formulation of cypermethrin (0.15 % w/w) and pyrethrins (0.2 % w/w) (Tri-Tec 14®, LS Sales (Farnham) Ltd, Bloxham, UK) applied to black polyvinyl-coated polyester insect screen (1.6 mm aperture; 1.6 mm thickness) inflicted 100 % mortality on batches of C. nubeculosus following a three minute exposure in the WHO cone bioassays at 1, 7 and 14 days post-treatment. Tri-Tec 14® outperformed all other treatments tested and was subsequently selected for use in field trials. The first trial demonstrated that treated screens placed around an ultraviolet light-suction trap entirely prevented Culicoides being collected, despite their collection in identical traps with untreated screening or no screening. The second field trial examined entry of Culicoides into stables containing horses and found that while the insecticide treated screens reduced entry substantially, there was still a small risk of exposure

Combining Synthetic Human Odours and Low-Cost Electrocuting Grids to Attract and Kill Outdoor-Biting Mosquitoes: Field and Semi-Field Evaluation of an Improved Mosquito Landing Box

PubMed Central

Matowo, Nancy S.; Koekemoer, Lizette L.; Moore, Sarah J.; Mmbando, Arnold S.; Mapua, Salum A.; Coetzee, Maureen; Okumu, Fredros O.

2016-01-01

Background On-going malaria transmission is increasingly mediated by outdoor-biting vectors, especially where indoor insecticidal interventions such as long-lasting insecticide treated nets (LLINs) are widespread. Often, the vectors are also physiologically resistant to insecticides, presenting major obstacles for elimination. We tested a combination of electrocuting grids with synthetic odours as an alternative killing mechanism against outdoor-biting mosquitoes. Methods An odour-baited device, the Mosquito Landing Box (MLB), was improved by fitting it with low-cost electrocuting grids to instantly kill mosquitoes attracted to the odour lure, and automated photo switch to activate attractant-dispensing and mosquito-killing systems between dusk and dawn. MLBs fitted with one, two or three electrocuting grids were compared outdoors in a malaria endemic village in Tanzania, where vectors had lost susceptibility to pyrethroids. MLBs with three grids were also tested in a large semi-field cage (9.6×9.6×4.5m), to assess effects on biting-densities of laboratory-reared Anopheles arabiensis on volunteers sitting near MLBs. Results Significantly more mosquitoes were killed when MLBs had two or three grids, than one grid in wet and dry seasons (P<0.05). The MLBs were highly efficient against Mansonia species and malaria vector, An. arabiensis. Of all mosquitoes, 99% were non-blood fed, suggesting host-seeking status. In the semi-field, the MLBs reduced mean number of malaria mosquitoes attempting to bite humans fourfold. Conclusion The improved odour-baited MLBs effectively kill outdoor-biting malaria vector mosquitoes that are behaviourally and physiologically resistant to insecticidal interventions e.g. LLINs. The MLBs reduce human-biting vector densities even when used close to humans, and are insecticide-free, hence potentially antiresistance. The devices could either be used as surveillance tools or complementary mosquito control interventions to accelerate malaria

Residual mosquito barrier treatments on U.S. military camouflage netting in a southern California desert environment

USDA-ARS?s Scientific Manuscript database

Treating perimeters of vegetation with residual insecticides for protection from mosquito vectors has potential for U.S. military force health protection. However, for current U.S. military operations in hot-arid environments with little or no vegetation, residual applications on portable artificial...

An experimental hut evaluation of Olyset Plus, a long-lasting insecticidal net treated with a mixture of permethrin and piperonyl butoxide, against Anopheles fluviatilis in Odisha State, India.

PubMed

Gunasekaran, Kasinathan; Sahu, Sudhansu Sekhar; Vijayakumar, Tharmalingam; Subramanian, Swaminathan; Yadav, Rajpal Singh; Pigeon, Olivier; Jambulingam, Purushothaman

2016-07-21

Fast development of pyrethroid resistance in malaria vectors prompted the development of new vector control tools including combination of insecticides with different modes of action as part of resistance management strategies. Olyset Plus® is a new long-lasting insecticidal net, in which, permethrin and a synergist, piperonyl butoxide (PBO), are incorporated into filaments. Mixture nets such as this may have application against resistant mosquitoes, particularly those whose resistance is based on oxidative metabolism. There may also be enhanced activity against susceptible mosquitoes since mixed function oxidases are involved in a many metabolic activities including activation to form bioactive compounds. Bio-efficacy of Olyset Plus was evaluated against susceptible malaria vector, Anopheles fluviatilis in experimental huts. Deterrence, blood feeding inhibition, induced exophily and killing effect were measured to assess the bio-efficacy. The results were compared with Olyset Net®, a polyethylene permethrin-incorporated LLIN and a conventionally treated polyester net (with permethrin) washed to just before exhaustion. Results showed significant reduction in entry (treatment: 0.4-0.8; control: 4.2 per trap-night) and increase in exit (56.3-82.9 % and 44.2 %) rates of Anopheles fluviatilis in the treatment arms compared to control (P < 0.05). While blood feeding rates declined in treatment arms (18.8-30.6 %), it increased in control (77.6 %) (P < 0.05). This was further evident from the blood-feeding inhibition rates in treatment arms (60.6-90.6 %). Total mortality was significantly higher in all treatment arms (96.3-100 %) compared to control arm (2 %) (P < 0.05). Chemical analysis for active ingredient (AI) showed retention of 75 and 88 % in Olyset plus and Olyset net respectively after 20 washes. Performance of Olyset Plus washed 20 times was equal to the CTN and Olyset Net against the susceptible malaria vector An. fluviatilis, fulfilling the

Impact of lambdacyhalothrin capsule suspension treated bed nets on malaria in tribal villages of Malkangiri district, Orissa, India.

PubMed

Sahu, S S; Vijayakumar, T; Kalyanasundaram, M; Subramanian, S; Jambulingam, P

2008-09-01

Insecticide treated mosquito nets are increasingly being used in malaria control programmes. One of the problems with the treatment of bed nets with conventional formulations of insecticides was that regular washing of treated nets diminish insecticidal effect. Lambdacyhalothrin 2.5 capsule suspension (CS) (2.5% a.i., w/v), a new water-based microencapsulated formulation is reported to have wash-resistant property and longer persistence on the netting material than other formulations. We evaluated the impact of the use of nylon bed nets treated with lambdacyhalothrin 2.5 CS at 10 mg (a.i.)/m(2) in comparison to untreated nets and no nets on malaria in tribal villages in Orissa. Nine foothill villages, highly endemic for falciparum malaria, from the Primary Health Centre (PHC) areas of Khairput and Kudumulugumma of Malkangiri district, Orissa, were divided into three groups, each with a population of about 500 and allocated randomly for treated (TN) and untreated nets (UN) and no nets (NN). Bed nets were distributed in September 2001 and retreatment was done in June 2002. The impact was assessed based on the changes in vector density, parous rate, malaria incidence and parasite rates. Indoor-resting collections of Anopheles fluviatilis and An. culicifacies were made at fortnightly intervals from fixed human dwellings. Mass blood surveys before and after distribution of nets and fortnightly active surveillance were carried out to assess the change in parasite rates and malaria incidence. Bioassays were conducted at fortnightly intervals on the bed nets supplied to the villagers. The reductions in indoor resting catches of An. fluviatilis and An. culicifacies were 96 and 38 per cent in villages with treated nets and 2.6 and 23 per cent in villages with untreated nets respectively compared to no net villages. For six months following treatment, 100 per cent mortality of An. fluviatilis was observed on the unwashed nets and on the nets washed once or twice. After re

Social marketing of insecticide-treated bednets: the case for Pakistan.

PubMed

Qazi, S; Shaikh, B T

2007-01-01

With an estimated half a million cases of malaria annually in Pakistan, and drug resistant cases on the increase, more practical preventive measures such as insecticide-treated bednets are essential. Social marketing through commercial channels has become an important cost-effective means to deliver health products and services to low income people and to motivate them to use these services. It has been demonstrated that social marketing of insecticide-treated bednets has saved the lives of millions of people in malaria-endemic regions at a cost as low as U.S. $2 per person. Social marketing could be an effective strategy for getting insecticide-treated nets to poor communities in Pakistan who are most vulnerable to malaria.

Use of insecticide-treated house screens to reduce infestations of dengue virus vectors, Mexico.

PubMed

Manrique-Saide, Pablo; Che-Mendoza, Azael; Barrera-Perez, Mario; Guillermo-May, Guillermo; Herrera-Bojorquez, Josue; Dzul-Manzanilla, Felipe; Gutierrez-Castro, Cipriano; Lenhart, Audrey; Vazquez-Prokopec, Gonzalo; Sommerfeld, Johannes; McCall, Philip J; Kroeger, Axel; Arredondo-Jimenez, Juan I

2015-02-01

Dengue prevention efforts rely on control of virus vectors. We investigated use of insecticide-treated screens permanently affixed to windows and doors in Mexico and found that the screens significantly reduced infestations of Aedes aegypti mosquitoes in treated houses. Our findings demonstrate the value of this method for dengue virus vector control.

Long-Lasting Insecticidal Nets Are Synergistic with Mass Drug Administration for Interruption of Lymphatic Filariasis Transmission in Nigeria

PubMed Central

Eigege, Abel; Miri, Emmanuel; Sallau, Adamu; Umaru, John; Mafuyai, Hayward; Chuwang, Yohanna S.; Danjuma, Goshit; Danboyi, Jacob; Adelamo, Solomon E.; Mancha, Bulus S.; Okoeguale, Bridget; Patterson, Amy E.; Rakers, Lindsay; Richards, Frank O.

2013-01-01

In central Nigeria Anopheles mosquitoes transmit malaria and lymphatic filariasis (LF). The strategy used for interrupting LF transmission in this area is annual mass drug administration (MDA) with albendazole and ivermectin, but after 8 years of MDA, entomological evaluations in sentinel villages showed continued low-grade mosquito infection rates of 0.32%. After long-lasting insecticidal net (LLIN) distribution by the national malaria program in late 2010, however, we were no longer able to detect infected vectors over a 24-month period. This is evidence that LLINs are synergistic with MDA in interrupting LF transmission. PMID:24205421

Implementation of an insecticide-treated net subsidy scheme under a public-private partnership for malaria control in Tanzania--challenges in implementation.

PubMed

Njau, Ritha J A; de Savigny, Don; Gilson, Lucy; Mwageni, Eleuther; Mosha, Franklin W

2009-08-21

In the past decade there has been increasing visibility of malaria control efforts at the national and international levels. The factors that have enhanced this scenario are the availability of proven interventions such as artemisinin-based combination therapy, the wide scale use of insecticide-treated nets (ITNs) and a renewed emphasis in indoor residual house-spraying. Concurrently, there has been a window of opportunity of financial commitments from organizations such as the Global Fund for HIV/AIDS, Tuberculosis and Malaria (GFATM), the President's Malaria Initiative and the World Bank Booster programme. The case study uses the health policy analysis framework to analyse the implementation of a public-private partnership approach embarked upon by the government of Tanzania in malaria control - 'The Tanzania National Voucher Scheme'- and in this synthesis, emphasis is on the challenges faced by the scheme during the pre-implementation (2001 - 2004) and implementation phases (2004 - 2005). Qualitative research tools used include: document review, interview with key informants, stakeholder's analysis, force-field analysis, time line of events, policy characteristic analysis and focus group discussions. The study is also complemented by a cross-sectional survey, which was conducted at the Rufiji Health Demographic Surveillance Site, where a cohort of women of child-bearing age were followed up regarding access and use of ITNs. The major challenges observed include: the re-introduction of taxes on mosquito nets and related products, procurement and tendering procedures in the implementation of the GFATM, and organizational arrangements and free delivery of mosquito nets through a Presidential initiative. The lessons gleaned from this synthesis include: (a) the consistency of the stakeholders with a common vision, was an important strength in overcoming obstacles, (b) senior politicians often steered the policy agenda when the policy in question was a 'crisis event

Pilot study on the combination of an organophosphate-based insecticide paint and pyrethroid-treated long lasting nets against pyrethroid resistant malaria vectors in Burkina Faso.

PubMed

Mosqueira, Beatriz; Soma, Dieudonné D; Namountougou, Moussa; Poda, Serge; Diabaté, Abdoulaye; Ali, Ouari; Fournet, Florence; Baldet, Thierry; Carnevale, Pierre; Dabiré, Roch K; Mas-Coma, Santiago

2015-08-01

A pilot study to test the efficacy of combining an organophosphate-based insecticide paint and pyrethroid-treated Long Lasting Insecticide Treated Nets (LLINs) against pyrethroid-resistant malaria vector mosquitoes was performed in a real village setting in Burkina Faso. Paint Inesfly 5A IGR™, comprised of two organophosphates (OPs) and an Insect Growth Regulator (IGR), was tested in combination with pyrethroid-treated LLINs. Efficacy was assessed in terms of mortality for 12 months using Early Morning Collections of malaria vectors and 30-minute WHO bioassays. Resistance to pyrethroids and OPs was assessed by detecting the frequency of L1014F and L1014S kdr mutations and Ace-1(R)G119S mutation, respectively. Blood meal origin was identified using a direct enzyme-linked immunosorbent assay (ELISA). The combination of Inesfly 5A IGR™ and LLINs was effective in killing 99.9-100% of malaria vector populations for 6 months regardless of the dose and volume treated. After 12 months, mortality rates decreased to 69.5-82.2%. The highest mortality rates observed in houses treated with 2 layers of insecticide paint and a larger volume. WHO bioassays supported these results: mortalities were 98.8-100% for 6 months and decreased after 12 months to 81.7-97.0%. Mortality rates in control houses with LLINs were low. Collected malaria vectors consisted exclusively of Anopheles coluzzii and were resistant to pyrethroids, with a L1014 kdr mutation frequency ranging from 60 to 98% through the study. About 58% of An. coluzzii collected inside houses had bloodfed on non-human animals. Combining Inesfly 5A IGR™ and LLINs yielded a one year killing efficacy against An. coluzzii highly resistant to pyrethroids but susceptible to OPs that exhibited an anthropo-zoophilic behaviour in the study area. The results obtained in a real setting supported previous work performed in experimental huts and underscore the need to study the impact that this novel strategy may have on clinical

Evaluation of the effects of repeated hand washing, sunlight, smoke and dirt on the persistence of deltamethrin on insecticide-treated nets.

PubMed

Kayedi, M H; Lines, J D; Haghdoost, A A; Vatandoost, M H; Rassi, Y; Khamisabady, K

2008-08-01

Field studies were carried out in Iran to evaluate the effect of various factors (washing, sun, smoke, dust and dirt) on the residual insecticidal activity of PermaNet (a brand of long-lasting insecticidal net), and on nets conventionally treated with deltamethrin (K-O Tab), using bioassay tests. Thirty-two nets were washed five or 15 times, and eight nets were not washed at all. Nets were washed vigorously in cold tap water (17 degrees C, pH 8.9) with a detergent. Hand rubbing continued for 3min. After washing, some nets were exposed to dense smoke from a dung-hay fire for 3min and were also left exposed to the dusty wind between washes. One group of nets was exposed to the sunlight for the full 3-d interval between washes; another was exposed to sunlight for just 3h after each wash; two other groups were kept in the shade. There was a significantly greater loss of activity in nets exposed to the sun throughout the 3-d interval between washes: that is, for a total of 15 to 45 d. However, short sunlight exposure (maximum 3h between washes) during drying did not have any effect. We did not find any significant effect of exposure to dirt, dust and smoke after washing. It is concluded that the effect of sun is much smaller than that of washing, and that drying nets for a few hours in the sun is not harmful.

The effect of long-lasting insecticidal water container covers on field populations of Aedes aegypti (L.) mosquitoes in Cambodia.

PubMed

Seng, Chang Moh; Setha, To; Nealon, Joshua; Chantha, Ngan; Socheat, Doung; Nathan, Michael B

2008-12-01

Dengue in Cambodia is mainly transmitted by Aedes aegypti (L.) mosquitoes that primarily breed in large, concrete jars (> or =200 liters) used for the storage of water for domestic use. Following a preliminary risk assessment, long-lasting insecticidal netting (LN) treated with deltamethrin was incorporated into the design of the covers for these jars. Their effect on immature and adult female populations of Ae. aegypti in six villages in a peri-urban area of Cambodia were compared with populations in six nearby control villages before and for 22 weeks after distribution of the jar covers. There were significantly fewer pupae per house in intervention villages than in control villages (6.6 and 31.9, respectively, p<0.01). Fewer pupae were recovered from intervention houses than from control houses at every post-intervention assessment. Two weeks after the intervention, the average number of indoor resting female Ae. aegypti per house in the intervention villages had declined approximately three-fold, whereas in the controls there was only a slight reduction (16%). The magnitude of the difference between the two areas diminished over time, which contact bioassays confirmed was likely due to a gradual reduction of insecticidal effect of the jar covers. In the study area, insecticide-treated covers for large concrete water storage jars were efficacious for controlling Ae. aegypti in the protected water jars and with a demonstrable effect on adult densities and survival. Further studies of this targeted container strategy in Cambodia, and elsewhere, are recommended. However, improvements in technology that would extend the duration of insecticidal effectiveness of LN materials may be needed for the development of cost-effective public health applications.

"When I sleep under the net, nothing bothers me; I sleep well and I'm happy": Senegal's culture of net use and how inconveniences to net use do not translate to net abandonment.

PubMed

Berthe, Sara; Loll, Dana; Faye, Sylvain L; Wone, Issa; Koenker, Hannah; Arnold, Bethany; Weber, Rachel

2014-09-12

Despite recent advances in the fight against the disease, malaria remains a serious threat to the health and well-being of populations in endemic countries. The use of long-lasting insecticidal nets (LLIN) reduces contact between the vector and humans, thereby reducing transmission of the disease. LLINs have become an essential component of malaria control programmes worldwide. The Culture of Net Use study used qualitative and quantitative methods in a longitudinal and iterative design over two phases, in order to capture changes in net use over a year and a half period and covering both dry and rainy seasons. Data were collected from a total of 56 households in eight regions to understand variations due to geographical, cultural, and universal coverage differences. At the time of the data collection, the universal coverage campaign had been completed in six of the eight regions (Dakar and Thies excluded). Perceived barriers to use were primarily related to the characteristics of the net itself, include shape, insecticide, and a variety of minority responses, such as perceived lack of mosquito density and being unaccustomed to using nets. Insecticide-related complaints found that insecticide did not present a significant barrier to use, but was cited as a nuisance. Feelings of suffocation continued to be the most commonly cited nuisance. Respondents who favoured the use of insecticide on nets appeared to be more aware of the health and malaria prevention benefits of the insecticide than those who perceived it negatively. Despite prior evidence that barriers such as heat, shape, insecticide and perceived mosquito density contribute to non-use of LLINs in other countries, this study has shown that these factors are considered more as nuisances and that they do not consistently prevent the use of nets among respondents in Senegal. Of those who cited inconveniences with their nets, few were moved to stop using a net. Respondents from this study overcame these barriers

Implementation of an insecticide-treated net subsidy scheme under a public-private partnership for malaria control in Tanzania – challenges in implementation

PubMed Central

2009-01-01

Background In the past decade there has been increasing visibility of malaria control efforts at the national and international levels. The factors that have enhanced this scenario are the availability of proven interventions such as artemisinin-based combination therapy, the wide scale use of insecticide-treated nets (ITNs) and a renewed emphasis in indoor residual house-spraying. Concurrently, there has been a window of opportunity of financial commitments from organizations such as the Global Fund for HIV/AIDS, Tuberculosis and Malaria (GFATM), the President's Malaria Initiative and the World Bank Booster programme. Methods The case study uses the health policy analysis framework to analyse the implementation of a public-private partnership approach embarked upon by the government of Tanzania in malaria control – 'The Tanzania National Voucher Scheme'- and in this synthesis, emphasis is on the challenges faced by the scheme during the pre-implementation (2001 – 2004) and implementation phases (2004 – 2005). Qualitative research tools used include: document review, interview with key informants, stakeholder's analysis, force-field analysis, time line of events, policy characteristic analysis and focus group discussions. The study is also complemented by a cross-sectional survey, which was conducted at the Rufiji Health Demographic Surveillance Site, where a cohort of women of child-bearing age were followed up regarding access and use of ITNs. Results The major challenges observed include: the re-introduction of taxes on mosquito nets and related products, procurement and tendering procedures in the implementation of the GFATM, and organizational arrangements and free delivery of mosquito nets through a Presidential initiative. Conclusion The lessons gleaned from this synthesis include: (a) the consistency of the stakeholders with a common vision, was an important strength in overcoming obstacles, (b) senior politicians often steered the policy agenda when

Insecticide-treated nets mass distribution campaign: benefits and lessons in Zambia.

PubMed

Masaninga, Freddie; Mukumbuta, Nawa; Ndhlovu, Ketty; Hamainza, Busiku; Wamulume, Pauline; Chanda, Emmanuel; Banda, John; Mwanza-Ingwe, Mercy; Miller, John M; Ameneshewa, Birkinesh; Mnzava, Abraham; Kawesha-Chizema, Elizabeth

2018-04-24

Zambia was an early adopter of insecticide-treated nets strategy in 2001, and policy for mass distribution with long-lasting insecticidal nets (LLINs) in 2005. Since then, the country has implemented mass distribution supplemented with routine delivery through antenatal care and under five clinics in health facilities. The national targets of universal (100%) coverage and 80% utilization of LLINs have not been attained. Free mass LLIN distribution campaign in Zambia offers important lessons to inform future campaigns in the African region. This study reviewed LLIN free mass distribution campaign information derived from Zambia's national and World Health Organization Global Malaria Programme annual reports and strategic plans published between 2001 and 2016. In 2014, a nationwide mass distribution campaign in Zambia delivered all the 6.0 million LLINs in 6 out of 10 provinces in 4 months between June and September before the onset of the rainy season. Compared with 235,800 LLINs and 2.9 million LLINs distributed on a rolling basis in 2008 and 2013, respectively, the 2014 mass campaign, which distributed 6 million LLINs represented the largest one-time-nationwide LLIN distribution in Zambia. The province (Luapula) with highest malaria transmission, mostly with rural settings recorded 98-100% sleeping spaces in homes covered with LLINs. The percentage of households owning at least 1 LLIN increased from 50.9% in 2006 to 77.7% in 2015. The 2014 mass campaign involved a coordinated response with substantial investments into macro (central) and micro (district) level planning, capacity building, tracking and logistics management supported by a new non-health sector partnership landscape. Coordination of LLIN distribution and logistics benefited from the mobile phone technology to transmit "real time" data on commodity tracking that facilitated timely delivery to districts. Free mass distribution of LLINs policy was adopted in 2005 in Zambia. Consistently implemented

Use of insecticide treated nets by pregnant women and associated factors in a pre-dominantly rural population in northern Ethiopia.

PubMed

Belay, Mebrahtom; Deressa, Wakgari

2008-10-01

To describe the use of insecticide treated nets (ITNs) among pregnant women and examine factors associated with its access and use. Community-based cross-sectional study of 815 pregnant women in eight malarious kebeles in northern Ethiopia based on two-stage cluster design from May to June 2006. Knowledge on malaria, its cause and preventive measures; treatment seeking behaviour; possession and use of ITNs by pregnant women and under-five children were ascertained through interview and observation. Logistic regression was used to determine factors associated with ITNs use. Knowledge about the cause, transmission and preventive measures of malaria was relatively good; 90.2% of women associated malaria with mosquito bites and 94.2% with living near water ponds. Ten per cent reported malaria illness within the 14 days before the survey, and sought treatment mainly from public health facilities (56.5%) and community health workers (37.6%). Of 815 households surveyed, 59% owned at least one non-long lasting or long-lasting ITN (59.5% rural vs. 54.5% urban; P = 0.401). Lack of access to ITNs (68.3%) and the perception that nets could not prevent malaria (27%) were the main reasons for non-ownership of nets. A total of 58.4% of 481 pregnant women from households owning at least one ITN had slept under it during the previous night. Fewer rural (56.7%) than urban women (76.2%) used ITNs (P = 0.001). In 57.6% of households with at least one ITN, under-five children had used it the night before. Higher educational attainment was an important predictor of ITNs use (OR = 3.1, 95% CI = 2.1, 4.6). Household ownership of ITNs and their use by pregnant women is promising with the current efforts to scale-up ITNs implementation, but the gap between ownership and use remains high. Consistent and proper use of nets by pregnant women should be ensured through information campaigns. Rapid expansion of access to long lasting ITNs requires that government and NGOs supply them in adequate

3D mosquito screens to create window double screen traps for mosquito control.

PubMed

Khattab, Ayman; Jylhä, Kaisa; Hakala, Tomi; Aalto, Mikko; Malima, Robert; Kisinza, William; Honkala, Markku; Nousiainen, Pertti; Meri, Seppo

2017-08-29

Mosquitoes are vectors for many diseases such as malaria. Insecticide-treated bed nets and indoor residual spraying of insecticides are the principal malaria vector control tools used to prevent malaria in the tropics. Other interventions aim at reducing man-vector contact. For example, house screening provides additive or synergistic effects to other implemented measures. We used commercial screen materials made of polyester, polyethylene or polypropylene to design novel mosquito screens that provide remarkable additional benefits to those commonly used in house screening. The novel design is based on a double screen setup made of a screen with 3D geometric structures parallel to a commercial mosquito screen creating a trap between the two screens. Owing to the design of the 3D screen, mosquitoes can penetrate the 3D screen from one side but cannot return through the other side, making it a unidirectional mosquito screen. Therefore, the mosquitoes are trapped inside the double screen system. The permissiveness of both sides of the 3D screens for mosquitoes to pass through was tested in a wind tunnel using the insectary strain of Anopheles stephensi. Among twenty-five tested 3D screen designs, three designs from the cone, prism, or cylinder design groups were the most efficient in acting as unidirectional mosquito screens. The three cone-, prism-, and cylinder-based screens allowed, on average, 92, 75 and 64% of Anopheles stephensi mosquitoes released into the wind tunnel to penetrate the permissive side and 0, 0 and 6% of mosquitoes to escape through the non-permissive side, respectively. A cone-based 3D screen fulfilled the study objective. It allowed capturing 92% of mosquitoes within the double screen setup inside the wind tunnel and blocked 100% from escaping. Thus, the cone-based screen effectively acted as a unidirectional mosquito screen. This 3D screen-based trap design could therefore be used in house screening as a means of avoiding infective bites and

Mosquito Bite Prevention For Travelers

MedlinePlus

... is an insecticide that kills mosquitoes and other insects. - Do not wash bed nets or expose them ... for extra protection. Use only an EPA-registered insect repellent Š Consider bringing insect repellent with you. Š Always ...

Assessment on the ownership and use of mosquito nets in Mozambique

PubMed Central

Arroz, Jorge Alexandre Harrison; Chirrute, Francisco; Mendis, Chandana; e, Marta Honesta Chande; Kollhoff, Veronique

2016-01-01

ABSTRACT OBJECTIVE To assess the ownership and use of mosquito nets in 2014, in Mozambique. METHODS This observational and cross-sectional study assessed, in February and March 2015, 69 districts (nine of 11 provinces of Mozambique) that have benefited from the mass distribution of mosquito nets. The Lot Quality Assurance Sampling methodology was used. Each locality was denominated supervision area. The Lot Quality Assurance Sampling opts for a minimum of 19 households (in this case, we decided for a minimum of 100 households per district) from each supervision area to assess an indicator (in this case, two indicators were assessed: ownership and use of mosquito nets). Two questions guided the research: a) received a mosquito net; b) used a mosquito net the night before. RESULTS A total of 6,725 households were assessed. Eighty three percent of them had received mosquito nets in the campaign. Of the 6,232 respondents, 82.0% said they used mosquito nets the night before. The districts of the provinces with low coverage of ownership and use were Tete (69.5% and 60.0%, respectively), Zambezia (79.0% and 60.0%, respectively), and Gaza (81.6% and 70.7%, respectively). The largest coverage of ownership and use were observed in the districts of Nampula (96.7% and 93.8%, respectively) and Niassa (86.0% and 85.4% respectively). CONCLUSIONS In the districts assessed, the progression of ownership and use of mosquito nets is satisfactory. Nampula and Niassa are the only provinces where ownership and use are at desired levels. PMID:28099655

Mathematical evaluation of community level impact of combining bed nets and indoor residual spraying upon malaria transmission in areas where the main vectors are Anopheles arabiensis mosquitoes

PubMed Central

2013-01-01

Background Indoor residual insecticide spraying (IRS) and long-lasting insecticide treated nets (LLINs) are commonly used together even though evidence that such combinations confer greater protection against malaria than either method alone is inconsistent. Methods A deterministic model of mosquito life cycle processes was adapted to allow parameterization with results from experimental hut trials of various combinations of untreated nets or LLINs (Olyset®, PermaNet 2.0®, Icon Life® nets) with IRS (pirimiphos methyl, lambda cyhalothrin, DDT), in a setting where vector populations are dominated by Anopheles arabiensis, so that community level impact upon malaria transmission at high coverage could be predicted. Results Intact untreated nets alone provide equivalent personal protection to all three LLINs. Relative to IRS plus untreated nets, community level protection is slightly higher when Olyset® or PermaNet 2.0® nets are added onto IRS with pirimiphos methyl or lambda cyhalothrin but not DDT, and when Icon Life® nets supplement any of the IRS insecticides. Adding IRS onto any net modestly enhances communal protection when pirimiphos methyl is sprayed, while spraying lambda cyhalothrin enhances protection for untreated nets but not LLINs. Addition of DDT reduces communal protection when added to LLINs. Conclusions Where transmission is mediated primarily by An. arabiensis, adding IRS to high LLIN coverage provides only modest incremental benefit (e.g. when an organophosphate like pirimiphos methyl is used), but can be redundant (e.g. when a pyrethroid like lambda cyhalothin is used) or even regressive (e.g. when DDT is used for the IRS). Relative to IRS plus untreated nets, supplementing IRS with LLINs will only modestly improve community protection. Beyond the physical protection that intact nets provide, additional protection against transmission by An. arabiensis conferred by insecticides will be remarkably small, regardless of whether they are delivered

Mathematical evaluation of community level impact of combining bed nets and indoor residual spraying upon malaria transmission in areas where the main vectors are Anopheles arabiensis mosquitoes.

PubMed

Okumu, Fredros O; Kiware, Samson S; Moore, Sarah J; Killeen, Gerry F

2013-01-16

Indoor residual insecticide spraying (IRS) and long-lasting insecticide treated nets (LLINs) are commonly used together even though evidence that such combinations confer greater protection against malaria than either method alone is inconsistent. A deterministic model of mosquito life cycle processes was adapted to allow parameterization with results from experimental hut trials of various combinations of untreated nets or LLINs (Olyset, PermaNet 2.0, Icon Life nets) with IRS (pirimiphos methyl, lambda cyhalothrin, DDT), in a setting where vector populations are dominated by Anopheles arabiensis, so that community level impact upon malaria transmission at high coverage could be predicted. Intact untreated nets alone provide equivalent personal protection to all three LLINs. Relative to IRS plus untreated nets, community level protection is slightly higher when Olyset or PermaNet 2.0 nets are added onto IRS with pirimiphos methyl or lambda cyhalothrin but not DDT, and when Icon Life nets supplement any of the IRS insecticides. Adding IRS onto any net modestly enhances communal protection when pirimiphos methyl is sprayed, while spraying lambda cyhalothrin enhances protection for untreated nets but not LLINs. Addition of DDT reduces communal protection when added to LLINs. Where transmission is mediated primarily by An. arabiensis, adding IRS to high LLIN coverage provides only modest incremental benefit (e.g. when an organophosphate like pirimiphos methyl is used), but can be redundant (e.g. when a pyrethroid like lambda cyhalothin is used) or even regressive (e.g. when DDT is used for the IRS). Relative to IRS plus untreated nets, supplementing IRS with LLINs will only modestly improve community protection. Beyond the physical protection that intact nets provide, additional protection against transmission by An. arabiensis conferred by insecticides will be remarkably small, regardless of whether they are delivered as LLINs or IRS. The insecticidal action of LLINs

Experience of targeting subsidies on insecticide-treated nets: what do we know and what are the knowledge gaps?

PubMed

Worrall, Eve; Hill, Jenny; Webster, Jayne; Mortimer, Julia

2005-01-01

Widespread coverage of vulnerable populations with insecticide-treated nets (ITNs) constitutes an important component of the Roll Back Malaria (RBM) strategy to control malaria. The Abuja Targets call for 60% coverage of children under 5 years of age and pregnant women by 2005; but current coverage in Africa is unacceptably low. The RBM 'Strategic Framework for Coordinated National Action in Scaling-up Insecticide-Treated Netting Programmes in Africa' promotes coordinated national action and advocates sustained public provision of targeted subsidies to maximise public health benefits, alongside support and stimulation of the private sector. Several countries have already planned or initiated targeted subsidy schemes either on a pilot scale or on a national scale, and have valuable experience which can inform future interventions. The WHO RBM 'Workshop on mapping models for delivering ITNs through targeted subsidies' held in Zambia in 2003 provided an opportunity to share and document these country experiences. This paper brings together experiences presented at the workshop with other information on experiences of targeting subsidies on ITNs, net treatment kits and retreatment services (ITN products) in order to describe alternative approaches, highlight their similarities and differences, outline lessons learnt, and identify gaps in knowledge. We find that while there is a growing body of knowledge on different approaches to targeting ITN subsidies, there are significant gaps in knowledge in crucial areas. Key questions regarding how best to target, how much it will cost and what outcomes (levels of coverage) to expect remain unanswered. High quality, well-funded monitoring and evaluation of alternative approaches to targeting ITN subsidies is vital to develop a knowledge base so that countries can design and implement effective strategies to target ITN subsidies.

Costs and effects of the Tanzanian national voucher scheme for insecticide-treated nets

PubMed Central

Mulligan, Jo-Ann; Yukich, Joshua; Hanson, Kara

2008-01-01

Background The cost-effectiveness of insecticide-treated nets (ITNs) in reducing morbidity and mortality is well established. International focus has now moved on to how best to scale up coverage and what financing mechanisms might be used to achieve this. The approach in Tanzania has been to deliver a targeted subsidy for those most vulnerable to the effects of malaria while at the same time providing support to the development of the commercial ITN distribution system. In October 2004, with funds from the Global Fund to Fight AIDS Tuberculosis and Malaria, the government launched the Tanzania National Voucher Scheme (TNVS), a nationwide discounted voucher scheme for ITNs for pregnant women and their infants. This paper analyses the costs and effects of the scheme and compares it with other approaches to distribution. Methods Economic costs were estimated using the ingredients approach whereby all resources required in the delivery of the intervention (including the user contribution) are quantified and valued. Effects were measured in terms of number of vouchers used (and therefore nets delivered) and treated nets years. Estimates were also made for the cost per malaria case and death averted. Results and Conclusion The total financial cost of the programme represents around 5% of the Ministry of Health's total budget. The average economic cost of delivering an ITN using the voucher scheme, including the user contribution, was $7.57. The cost-effectiveness results are within the benchmarks set by other malaria prevention studies. The Government of Tanzania's approach to scaling up ITNs uses both the public and private sectors in order to achieve and sustain the level of coverage required to meet the Abuja targets. The results presented here suggest that the TNVS is a cost-effective strategy for delivering subsidized ITNs to targeted vulnerable groups. PMID:18279509

Evaluation of sunlight-exposed pyrethroid-treated netting for the control of face fly and housefly (Diptera: Muscidae).

PubMed

Peck, George W; Ferguson, Holly J; LePage, Jane T; Hebert, Vincent R; O'Neal, Sally D; Walsh, Douglas B

2014-01-01

Face flies, Musca autumnalis De Geer (Diptera: Muscidae), and houseflies, Musca domestica L. (Diptera: Muscidae), have a significant impact on livestock and dairy production throughout North America. Pyrethroid insecticide efficacy can be affected by exposure to direct sunlight, and the rate of photodegradation is substrate and formulation dependent. Insecticide-treated netting (ITN) is finding new applications in crop and livestock production systems. A baseline study using long-duration no-choice assays has been carried out to gauge the effectiveness of ITN treated with β-cyfluthrin, λ-cyhalothrin and bifenthrin on face flies and houseflies. After 12 weeks in direct sunlight, ITN treated with β-cyfluthrin was still highly insecticidal to face flies and houseflies, producing 100% mortality in petri dish assays. However, sunlight reduced the insecticidal activity of λ-cyhalothrin, with 3% of face flies and 50% of houseflies surviving after exposure to ITN that had been deployed for 10 weeks. Insecticidal activity was greatly reduced on bifenthrin-treated netting, with 20% of face flies and 50% of houseflies surviving in assays with netting deployed for only 3 weeks. With careful choice of the pyrethroid applied, treated netting could be an important component of livestock integrated pest management programs focused on sustainable practices. © 2013 Society of Chemical Industry.

Effects of educational intervention on long-lasting insecticidal nets use in a malarious area, southeast Iran.

PubMed

Soleimani Ahmadi, Mussa; Vatandoost, Hassan; Shaeghi, Mansoreh; Raeisi, Ahmad; Abedi, Farshid; Eshraghian, Mohammad Reza; Aghamolaei, Teimur; Madani, Abdol Hossein; Safari, Reza; Jamshidi, Mahin; Alimorad, Abbas

2012-01-01

Long-lasting insecticidal nets (LLINs) have been advocated as an effective tool against malaria transmission. However, success of this community based intervention largely depends on the knowledge and practice regarding malaria and its prevention. According to the national strategy plan on evaluation of LLINs (Olyset nets), this study was conducted to determine the perceptions and practices about malaria and to improve use of LLINs in Bashagard district, one of the important foci of malaria in southeast Iran. The study area comprised 14 villages that were randomized in two clusters and designated as LLINs and untreated nets. Each of households in both clusters received two bed nets by the free distribution and delivery. After one month quantitative data collection method was used to collect information regarding the objectives of the study. On the basis of this information, an educational program was carried out in both areas to increase motivation for use of bed nets. Community knowledge and practice regarding malaria and LLIN use assessed pre- and post-educational program. The data were analyzed using SPSS ver.16 software. At baseline, 77.5% of respondents in intervention and 69.4 % in control area mentioned mosquito bite as the cause of malaria, this awareness increased significantly in intervention (90.3%) and control areas (87.9%), following the educational program. A significant increase also was seen in the proportion of households who used LLINs the previous night (92.5%) compared with untreated nets (87.1%). Educational status was an important predictor of LLINs use. Regular use of LLIN was considerably higher than the targeted coverage (80%) which recommended by World Heaths Organization. About 81.1% and 85.3% of respondents from LLIN and control areas reported that mosquito nuisance and subsequent malaria transmission were the main determinants of bed net use. These findings highlight a need for educational intervention in implementation of long

When intensity of deltamethrin resistance in Anopheles gambiae s.l. leads to loss of Long Lasting Insecticidal Nets bio-efficacy: a case study in north Cameroon.

PubMed

Etang, Josiane; Pennetier, Cédric; Piameu, Michael; Bouraima, Aziz; Chandre, Fabrice; Awono-Ambene, Parfait; Marc, Coosemans; Corbel, Vincent

2016-03-08

In Cameroon, insecticide resistance in Anopheles (An.) gambiae s.l. has been reported in several foci, prompting further investigations on associated patterns of Long-Lasting Insecticidal Nets (LLINs) bio-efficacy. The current study, conducted from June to August 2011, explored the intensity of deltamethrin resistance in An. gambiae s.l. from Pitoa and its impact on the residual bio-efficacy of LifeNet, a LLIN with deltamethrin incorporated into polypropylene nets (PND). Two-four days old females An. gambiae s.l. reared from larval collections in Pitoa were tested for susceptibility to DDT, permethrin and deltamethrin, using standard World Health Organization (WHO) tube assays. Intensity of deltamethrin resistance was explored using WHO tube assays, but across six working concentrations from 0.001 % to 0.5 %. Bio-efficacy of unwashed and washed PND was assessed using WHO cone test. Species identification and kdr 1014 genotyping were performed on mosquito samples that were not exposed to insecticides, using PCR-RFLP and HOLA methods respectively. The Kisumu reference susceptible strain of An. gambiae s.s. was used for comparisons. A total of 1895 An. gambiae s.l. specimens from Pitoa were used for resistance and PND bio-efficacy testing. This mosquito population was resistant to DDT, permethrin and deltamethrin, with 18-40 min knockdown times for 50 % of tested mosquitoes and 59-77 % mortality. Deltamethrin Resistance Ratio compared with the Kisumu strain was estimated at ≥500 fold. LifeNets were effective against the susceptible Kisumu (100 % knockdown (KD60min) and mortality) and the resistant Pitoa samples (95 % KD60min, 83-95 % mortality). However, the bio-efficacy gradually dropped against the Pitoa samples when nets were washed (X (2) = 35.887, df = 8, p < 0.001), and fell under the WHO efficacy threshold (80 % mortality and/or 95 % KD60min) between 10 and 15 washes. The Pitoa samples were composed of three sibling species: An. arabiensis (132

Explaining variation in adult Anopheles indoor resting abundance: the relative effects of larval habitat proximity and insecticide-treated bed net use.

PubMed

McCann, Robert S; Messina, Joseph P; MacFarlane, David W; Bayoh, M Nabie; Gimnig, John E; Giorgi, Emanuele; Walker, Edward D

2017-07-17

Spatial determinants of malaria risk within communities are associated with heterogeneity of exposure to vector mosquitoes. The abundance of adult malaria vectors inside people's houses, where most transmission takes place, should be associated with several factors: proximity of houses to larval habitats, structural characteristics of houses, indoor use of vector control tools containing insecticides, and human behavioural and environmental factors in and near houses. While most previous studies have assessed the association of larval habitat proximity in landscapes with relatively low densities of larval habitats, in this study these relationships were analysed in a region of rural, lowland western Kenya with high larval habitat density. 525 houses were sampled for indoor-resting mosquitoes across an 8 by 8 km study area using the pyrethrum spray catch method. A predictive model of larval habitat location in this landscape, previously verified, provided derivations of indices of larval habitat proximity to houses. Using geostatistical regression models, the association of larval habitat proximity, long-lasting insecticidal nets (LLIN) use, house structural characteristics (wall type, roof type), and peridomestic variables (cooking in the house, cattle near the house, number of people sleeping in the house) with mosquito abundance in houses was quantified. Vector abundance was low (mean, 1.1 adult Anopheles per house). Proximity of larval habitats was a strong predictor of Anopheles abundance. Houses without an LLIN had more female Anopheles gambiae s.s., Anopheles arabiensis and Anopheles funestus than houses where some people used an LLIN (rate ratios, 95% CI 0.87, 0.85-0.89; 0.84, 0.82-0.86; 0.38, 0.37-0.40) and houses where everyone used an LLIN (RR, 95% CI 0.49, 0.48-0.50; 0.39, 0.39-0.40; 0.60, 0.58-0.61). Cooking in the house also reduced Anopheles abundance across all species. The number of people sleeping in the house, presence of cattle near the house

"Before we used to get sick all the time": perceptions of malaria and use of long-lasting insecticide-treated bed nets (LLINs) in a rural Kenyan community

PubMed Central

2010-01-01

Background Malaria is a leading global cause of preventable morbidity and mortality, especially in sub-Saharan Africa, despite recent advances in treatment and prevention technologies. Scale-up and wide distribution of long-lasting insecticide-treated nets (LLINs) could rapidly decrease malarial disease in endemic areas, if used properly and continuously. Studies have shown that effective use of LLINs depends, in part, upon understanding causal factors associated with malaria. This study examined malaria beliefs, attitudes, and practices toward LLINs assessed during a large-scale integrated prevention campaign (IPC) in rural Kenya. Methods Qualitative interviews were conducted with 34 IPC participants who received LLINs as part of a comprehensive prevention package of goods and services. One month after distribution, interviewers asked these individuals about their attitudes and beliefs regarding malaria, and about their use of LLINs. Results Virtually all participants noted that mosquitoes were involved in causing malaria, though a substantial proportion of participants (47 percent) also mentioned an incorrect cause in addition to mosquitoes. For example, participants commonly noted that the weather (rain, cold) or consumption of bad food and water caused malaria. Regardless, most participants used the LLINs they were given and most mentioned positive benefits from their use, namely reductions in malarial illness and in the costs associated with its diagnosis and treatment. Conclusions Attitudes toward LLINs were positive in this rural community in Western Kenya, and respondents noted benefits with LLIN use. With improved understanding and clarification of the direct (mosquitoes) and indirect (e.g., standing water) causes of malaria, it is likely that LLIN use can be sustained, offering effective household-level protection against malaria. PMID:21118550

Laboratory evaluation of lambda-cyhalothrin a microencapsulated formulation on mosquito nets for control of vector mosquitos.

PubMed

Vythilingam, I; Zainal, A R; Hamidah, T

1999-03-01

Two formulations of lambda-cyhalothrin (EC-Emulsion concentrate and MC-Microencapsulated) were impregnated into bednets made of polyethylene and polyester. The nets were treated at a dosage of 15 mg/m2. For bioassay of insecticidal efficacy, female Anopheles maculatus and Aedes aegypti were exposed to the nets for two minutes and mortality was scored 24 hours later. The nets were also tested after repeated washings with water and with soap and water. Microencapsulated (2.5CS) formulation was more effective than emulsion concentrate (2.5EC) formulation on both net materials--polyethylene and polyester. Repeated washing with water and soap reduces the efficacy of all bednet treatment combinations. Microencapsulated formulation on polyethylene gave best results; it could sustain up to five washes with water and two with soap and water.

Survival and swimming behavior of insecticide-exposed larvae and pupae of the yellow fever mosquito Aedes aegypti.

PubMed

Tomé, Hudson Vv; Pascini, Tales V; Dângelo, Rômulo Ac; Guedes, Raul Nc; Martins, Gustavo F

2014-04-24

The yellow fever mosquito Aedes aegypti is essentially a container-inhabiting species that is closely associated with urban areas. This species is a vector of human pathogens, including dengue and yellow fever viruses, and its control is of paramount importance for disease prevention. Insecticide use against mosquito juvenile stages (i.e. larvae and pupae) is growing in importance, particularly due to the ever-growing problems of resistance to adult-targeted insecticides and human safety concerns regarding such use in human dwellings. However, insecticide effects on insects in general and mosquitoes in particular primarily focus on their lethal effects. Thus, sublethal effects of such compounds in mosquito juveniles may have important effects on their environmental prevalence. In this study, we assessed the survival and swimming behavior of A. aegypti 4th instar larvae (L4) and pupae exposed to increasing concentrations of insecticides. We also assessed cell death in the neuromuscular system of juveniles. Third instar larvae of A. aegypti were exposed to different concentrations of azadirachtin, deltamethrin, imidacloprid and spinosad. Insect survival was assessed for 10 days. The distance swam, the resting time and the time spent in slow swimming were assessed in 4th instar larvae (L4) and pupae. Muscular and nervous cells of L4 and pupae exposed to insecticides were marked with the TUNEL reaction. The results from the survival bioassays were subjected to survival analysis while the swimming behavioral data were subjected to analyses of covariance, complemented with a regression analysis. All insecticides exhibited concentration-dependent effects on survival of larvae and pupae of the yellow fever mosquito. The pyrethroid deltamethrin was the most toxic insecticide followed by spinosad, imidacloprid, and azadirachtin, which exhibited low potency against the juveniles. All insecticides except azadirachtin reduced L4 swimming speed and wriggling movements. A

Survival and swimming behavior of insecticide-exposed larvae and pupae of the yellow fever mosquito Aedes aegypti

PubMed Central

2014-01-01

Background The yellow fever mosquito Aedes aegypti is essentially a container-inhabiting species that is closely associated with urban areas. This species is a vector of human pathogens, including dengue and yellow fever viruses, and its control is of paramount importance for disease prevention. Insecticide use against mosquito juvenile stages (i.e. larvae and pupae) is growing in importance, particularly due to the ever-growing problems of resistance to adult-targeted insecticides and human safety concerns regarding such use in human dwellings. However, insecticide effects on insects in general and mosquitoes in particular primarily focus on their lethal effects. Thus, sublethal effects of such compounds in mosquito juveniles may have important effects on their environmental prevalence. In this study, we assessed the survival and swimming behavior of A. aegypti 4th instar larvae (L4) and pupae exposed to increasing concentrations of insecticides. We also assessed cell death in the neuromuscular system of juveniles. Methods Third instar larvae of A. aegypti were exposed to different concentrations of azadirachtin, deltamethrin, imidacloprid and spinosad. Insect survival was assessed for 10 days. The distance swam, the resting time and the time spent in slow swimming were assessed in 4th instar larvae (L4) and pupae. Muscular and nervous cells of L4 and pupae exposed to insecticides were marked with the TUNEL reaction. The results from the survival bioassays were subjected to survival analysis while the swimming behavioral data were subjected to analyses of covariance, complemented with a regression analysis. Results All insecticides exhibited concentration-dependent effects on survival of larvae and pupae of the yellow fever mosquito. The pyrethroid deltamethrin was the most toxic insecticide followed by spinosad, imidacloprid, and azadirachtin, which exhibited low potency against the juveniles. All insecticides except azadirachtin reduced L4 swimming speed and

A household randomized, controlled trial of the efficacy of 0.03% transfluthrin coils alone and in combination with long-lasting insecticidal nets on the incidence of Plasmodium falciparum and Plasmodium vivax malaria in Western Yunnan Province, China.

PubMed

Hill, Nigel; Zhou, Hong Ning; Wang, Piyu; Guo, Xiaofang; Carneiro, Ilona; Moore, Sarah J

2014-05-31

Mosquito coils are the most commonly used household insecticidal product in the world with sales exceeding 50 billion coils, used by two billion people worldwide annually. Despite strong evidence that coils prevent mosquito bites a systematic review concluded that there is no evidence that burning mosquito coils prevents malaria acquisition. Therefore, the current trial was designed to measure and compare prevention of malaria infection by mosquito coils or long-lasting insecticidal net (LLIN) or a combination of the two in Yunnan, China in the Greater Mekong sub-region. A four-arm single blind household-randomized design was chosen as coils emanate insecticide throughout the household. Households enrolled at baseline were randomly allocated by the lottery method to one of the four intervention arms: (i) nothing, (ii) 0.03% transfluthrin coils alone, (iii) deltamethrin long-lasting insecticide treated nets, (LLINs) alone or (iv) a combination of transfluthrin coils and deltamethrin LLINs. All household members were recruited to the study, with only those households excluded with pregnant or breastfeeding mothers, members with chest complaints or allergies or members that regularly slept away from home. The main outcome of interest was Plasmodium falciparum malaria prevalence detected by rapid diagnostic tests (RDTs) during six repeated monthly cross-sectional surveys. The secondary outcome of interest was the effect on Plasmodium vivax prevalence detected in the same way. A total of 2,052 households were recruited into the study, comprising 7,341 individuals The odds ratios of testing positive by RDT with P. falciparum or P. vivax were >75% lower for all intervention arms compared with the control arm. Coils alone provided 77% protection (95% CI: 50%-89%), LLINs provided 91% protection (95% CI: 72%-97%) and the combination of coils and LLINs provided 94% protection (95% CI: 77%-99%) against P. falciparum compared with the control arm. There was no statistically

Traditional nets interfere with the uptake of long-lasting insecticidal nets in the Peruvian Amazon: the relevance of net preference for achieving high coverage and use.

PubMed

Grietens, Koen Peeters; Muela Ribera, Joan; Soto, Veronica; Tenorio, Alex; Hoibak, Sarah; Aguirre, Angel Rosas; Toomer, Elizabeth; Rodriguez, Hugo; Llanos Cuentas, Alejandro; D'Alessandro, Umberto; Gamboa, Dionicia; Erhart, Annette

2013-01-01

While coverage of long-lasting insecticide-treated nets (LLIN) has steadily increased, a growing number of studies report gaps between net ownership and use. We conducted a mixed-methods social science study assessing the importance of net preference and use after Olyset® LLINs were distributed through a mass campaign in rural communities surrounding Iquitos, the capital city of the Amazonian region of Peru. The study was conducted in the catchment area of the Paujil and Cahuide Health Centres (San Juan district) between July 2007 and November 2008. During a first qualitative phase, participant observation and in-depth interviews collected information on key determinants for net preference and use. In a second quantitative phase, a survey among recently confirmed malaria patients evaluated the acceptability and use of both LLINs and traditional nets, and a case control study assessed the association between net preference/use and housing structure (open vs. closed houses). A total of 10 communities were selected for the anthropological fieldwork and 228 households participated in the quantitative studies. In the study area, bed nets are considered part of the housing structure and are therefore required to fulfil specific architectural and social functions, such as providing privacy and shelter, which the newly distributed Olyset® LLINs ultimately did not. The LLINs' failure to meet these criteria could mainly be attributed to their large mesh size, transparency and perceived ineffectiveness to protect against mosquitoes and other insects, resulting in 63.3% of households not using any of the distributed LLINs. Notably, LLIN usage was significantly lower in houses with no interior or exterior walls (35.2%) than in those with walls (73.8%) (OR = 5.2, 95CI [2.2; 12.3], p<0.001). Net preference can interfere with optimal LLIN use. In order to improve the number of effective days of LLIN protection per dollar spent, appropriate quantitative and qualitative methods

Traditional Nets Interfere with the Uptake of Long-Lasting Insecticidal Nets in the Peruvian Amazon: The Relevance of Net Preference for Achieving High Coverage and Use

PubMed Central

Grietens, Koen Peeters; Muela Ribera, Joan; Soto, Veronica; Tenorio, Alex; Hoibak, Sarah; Aguirre, Angel Rosas; Toomer, Elizabeth; Rodriguez, Hugo; Llanos Cuentas, Alejandro; D'Alessandro, Umberto; Gamboa, Dionicia; Erhart, Annette

2013-01-01

Background While coverage of long-lasting insecticide-treated nets (LLIN) has steadily increased, a growing number of studies report gaps between net ownership and use. We conducted a mixed-methods social science study assessing the importance of net preference and use after Olyset® LLINs were distributed through a mass campaign in rural communities surrounding Iquitos, the capital city of the Amazonian region of Peru. Methods The study was conducted in the catchment area of the Paujil and Cahuide Health Centres (San Juan district) between July 2007 and November 2008. During a first qualitative phase, participant observation and in-depth interviews collected information on key determinants for net preference and use. In a second quantitative phase, a survey among recently confirmed malaria patients evaluated the acceptability and use of both LLINs and traditional nets, and a case control study assessed the association between net preference/use and housing structure (open vs. closed houses). Results A total of 10 communities were selected for the anthropological fieldwork and 228 households participated in the quantitative studies. In the study area, bed nets are considered part of the housing structure and are therefore required to fulfil specific architectural and social functions, such as providing privacy and shelter, which the newly distributed Olyset® LLINs ultimately did not. The LLINs' failure to meet these criteria could mainly be attributed to their large mesh size, transparency and perceived ineffectiveness to protect against mosquitoes and other insects, resulting in 63.3% of households not using any of the distributed LLINs. Notably, LLIN usage was significantly lower in houses with no interior or exterior walls (35.2%) than in those with walls (73.8%) (OR = 5.2, 95CI [2.2; 12.3], p<0.001). Conclusion Net preference can interfere with optimal LLIN use. In order to improve the number of effective days of LLIN protection per dollar spent

Comparative analysis of response to selection with three insecticides in the dengue mosquito Aedes aegypti using mRNA sequencing.

PubMed

David, Jean-Philippe; Faucon, Frédéric; Chandor-Proust, Alexia; Poupardin, Rodolphe; Riaz, Muhammad Asam; Bonin, Aurélie; Navratil, Vincent; Reynaud, Stéphane

2014-03-05

Mosquito control programmes using chemical insecticides are increasingly threatened by the development of resistance. Such resistance can be the consequence of changes in proteins targeted by insecticides (target site mediated resistance), increased insecticide biodegradation (metabolic resistance), altered transport, sequestration or other mechanisms. As opposed to target site resistance, other mechanisms are far from being fully understood. Indeed, insecticide selection often affects a large number of genes and various biological processes can hypothetically confer resistance. In this context, the aim of the present study was to use RNA sequencing (RNA-seq) for comparing transcription level and polymorphism variations associated with adaptation to chemical insecticides in the mosquito Aedes aegypti. Biological materials consisted of a parental susceptible strain together with three child strains selected across multiple generations with three insecticides from different classes: the pyrethroid permethrin, the neonicotinoid imidacloprid and the carbamate propoxur. After ten generations, insecticide-selected strains showed elevated resistance levels to the insecticides used for selection. RNA-seq data allowed detecting over 13,000 transcripts, of which 413 were differentially transcribed in insecticide-selected strains as compared to the susceptible strain. Among them, a significant enrichment of transcripts encoding cuticle proteins, transporters and enzymes was observed. Polymorphism analysis revealed over 2500 SNPs showing > 50% allele frequency variations in insecticide-selected strains as compared to the susceptible strain, affecting over 1000 transcripts. Comparing gene transcription and polymorphism patterns revealed marked differences among strains. While imidacloprid selection was linked to the over transcription of many genes, permethrin selection was rather linked to polymorphism variations. Focusing on detoxification enzymes revealed that permethrin

Costs and cost-effectiveness of vector control in Eritrea using insecticide-treated bed nets.

PubMed

Yukich, Joshua O; Zerom, Mehari; Ghebremeskel, Tewolde; Tediosi, Fabrizio; Lengeler, Christian

2009-03-30

While insecticide-treated nets (ITNs) are a recognized effective method for preventing malaria, there has been an extensive debate in recent years about the best large-scale implementation strategy. Implementation costs and cost-effectiveness are important elements to consider when planning ITN programmes, but so far little information on these aspects is available from national programmes. This study uses a standardized methodology, as part of a larger comparative study, to collect cost data and cost-effectiveness estimates from a large programme providing ITNs at the community level and ante-natal care facilities in Eritrea. This is a unique model of ITN implementation fully integrated into the public health system. Base case analysis results indicated that the average annual cost of ITN delivery (2005 USD 3.98) was very attractive when compared with past ITN delivery studies at different scales. Financing was largely from donor sources though the Eritrean government and net users also contributed funding. The intervention's cost-effectiveness was in a highly attractive range for sub-Saharan Africa. The cost per DALY averted was USD 13 - 44. The cost per death averted was USD 438-1449. Distribution of nets coincided with significant increases in coverage and usage of nets nationwide, approaching or exceeding international targets in some areas. ITNs can be cost-effectively delivered at a large scale in sub-Saharan Africa through a distribution system that is highly integrated into the health system. Operating and sustaining such a system still requires strong donor funding and support as well as a functional and extensive system of health facilities and community health workers already in place.

Monitoring Malaria Vector Control Interventions: Effectiveness of Five Different Adult Mosquito Sampling Methods

PubMed Central

Onyango, Shirley A.; Kitron, Uriel; Mungai, Peter; Muchiri, Eric M.; Kokwaro, Elizabeth; King, Charles H.; Mutuku, Francis M.

2014-01-01

Long-term success of ongoing malaria control efforts based on mosquito bed nets (long-lasting insecticidal net) and indoor residual spraying is dependent on continuous monitoring of mosquito vectors, and thus on effective mosquito sampling tools. The objective of our study was to identify the most efficient mosquito sampling tool(s) for routine vector surveillance for malaria and lymphatic filariasis transmission in coastal Kenya. We evaluated relative efficacy of five collection methods—light traps associated with a person sleeping under a net, pyrethrum spray catches, Prokopack aspirator, clay pots, and urine-baited traps—in four villages representing three ecological settings along the south coast of Kenya. Of the five methods, light traps were the most efficient for collecting female Anopheles gambiae s.l. (Giles) (Diptera: Culicidae) and Anopheles funestus (Giles) (Diptera: Culicidae) mosquitoes, whereas the Prokopack aspirator was most efficient in collecting Culex quinquefasciatus (Say) (Diptera: Culicidae) and other culicines. With the low vector densities here, and across much of sub-Saharan Africa, wherever malaria interventions, long-lasting insecticidal nets, and/or indoor residual spraying are in place, the use of a single mosquito collection method will not be sufficient to achieve a representative sample of mosquito population structure. Light traps will remain a relevant tool for host-seeking mosquitoes, especially in the absence of human landing catches. For a fair representation of the indoor mosquito population, light traps will have to be supplemented with aspirator use, which has potential for routine monitoring of indoor resting mosquitoes, and can substitute the more labor-intensive and intrusive pyrethrum spray catches. There are still no sufficiently efficient mosquito collection methods for sampling outdoor mosquitoes, particularly those that are bloodfed. PMID:24180120

Ownership and utilisation of long lasting insecticide treated nets following free distribution campaign in South West Nigeria.

PubMed

Aderibigbe, Sunday Adedeji; Olatona, Foluke Adenike; Sogunro, Oluremi; Alawode, Gafar; Babatunde, Oluwole Adeyemi; Onipe, Ambrose Itopa; Bolarinwa, Oladimeji Akeem; Ameen, Hafsat Abolore; Osagbemi, Gordon Kayode; Sanya, Emmanuel Olatunde; Olarinoye, Adebunmi Oyeladun; Akande, Tanimola Makanjuola

2014-01-01

Malaria has proven to be the most horrendous and intractable amongst the health problems confronting countries in the sub-Saharan Africa. This study aims to determine the ownership and utilisation of long lasting insecticide treated nets following free distribution campaign in a state in South West Nigeria. Multi-stage sampling technique was used to recruit 2560 households spread across the 16 LGAs of the state. Interviewer administered standardized questionnaire was used for the survey. Data analysis was done using Stata 10 software. Sixty eight point six percent (68.6%) of the households had at least one under-five child living in the household while 32.6% had at least one pregnant woman living in the household. A total of 2440 (95.3%) households received LLIN during the campaign. Overall, the utilization rate for all respondents was 58.5%. Despite the fact that 2440 households received LLINs during the campaign, only 84.3% of them were seen to have hung theirs during the survey. Coverage and ownership of LLINs increased significantly following the free distribution campaign. There was a discrepancy between net possession and net use with rate of use lower than possession. Post distribution educational campaign should be incorporated into future distribution campaigns to help increase net utilisation.

Prevalence of malaria across Papua New Guinea after initial roll-out of insecticide-treated mosquito nets.

PubMed

Hetzel, Manuel W; Morris, Hector; Tarongka, Nandao; Barnadas, Céline; Pulford, Justin; Makita, Leo; Siba, Peter M; Mueller, Ivo

2015-12-01

To assess the population prevalence of malaria in villages across Papua New Guinea (PNG) following the first roll-out of free long-lasting insecticidal nets (LLIN). Between October 2008 and August 2009, a household survey was conducted in 49 random villages in districts covered by the LLIN distribution campaign. The survey extended to 19 villages in sentinel sites that had not yet been covered by the campaign. In each village, 30 households were randomly sampled, household heads were interviewed and capillary blood samples were collected from all consenting household members for microscopic diagnosis of malaria. Malaria prevalence ranged from 0% to 49.7% with a weighted average of 12.1% (95% CI 9.5, 15.3) in the national sample. More people were infected with Plasmodium falciparum (7.0%; 95% CI 5.4, 9.1) than with P. vivax (3.8%; 95% CI 2.4, 5.7) or P. malariae (0.3%; 95% CI 0.1, 0.6). Parasitaemia was strongly age-dependent with a P. falciparum peak at age 5-9 years and a P. vivax peak at age 1-4 years, yet with differences between geographical regions. Individual LLIN use and high community coverage were associated with reduced odds of infection (OR = 0.64 and 0.07, respectively; both P < 0.001). Splenomegaly in children and anaemia were common morbidities attributable to malaria. Malaria prevalence across PNG is again at levels comparable to the 1970s. The strong association of LLIN use with reduced parasitaemia supports efforts to achieve and maintain high country-wide coverage. P. vivax infections will require special targeted approaches across PNG. © 2015 The Authors. Tropical Medicine & International Health Published by John Wiley & Sons Ltd.

Improving estimates of insecticide-treated mosquito net coverage from household surveys: using geographic coordinates to account for endemicity

PubMed Central

2014-01-01

Background Coverage estimates of insecticide-treated nets (ITNs) are often calculated at the national level, but are intended to be a proxy for coverage among the population at risk of malaria. The analysis uses data for surveyed households, linking survey enumeration areas (clusters) with levels of malaria endemicity and adjusting coverage estimates based on the population at risk. This analysis proposes an approach that is not dependent on being able to identify malaria risk in a location during the survey design (since survey samples are typically selected on the basis of census sampling frames that do not include information on malaria zones), but rather being able to assign risk zones after a survey has already been completed. Methods The analysis uses data from 20 recent nationally representative Demographic and Health Survey (DHS), Malaria Indicator Surveys (MIS), an AIDS Indicator Survey (AIS), and an Anemia and Malaria Prevalence Survey (AMP). The malaria endemicity classification was assigned from the Malaria Atlas Project (MAP) 2010 interpolated data layers, using the Geographic Positioning System (GPS) location of the survey clusters. National ITN coverage estimates were compared with coverage estimates in intermediate/high endemicity zones (i.e., the population at risk of malaria) to determine whether the difference between estimates was statistically different from zero (p-value <0.5). Results Endemicity varies substantially in eight of the 20 studied countries. In these countries with heterogeneous transmission of malaria, stratification of households by endemicity zones shows that ITN coverage in intermediate/high endemicity zones is significantly higher than ITN coverage at the national level (Burundi, Kenya, Namibia, Rwanda, Tanzania, Senegal, Zambia, and Zimbabwe.). For example in Zimbabwe, the national ownership of ITNs is 28%, but ownership in the intermediate/high endemicity zone is 46%. Conclusion Incorporating this study’s basic and easily

Factors Associated with Correct and Consistent Insecticide Treated Curtain Use in Iquitos, Peru

PubMed Central

Scott, Thomas W.; Elder, John P.; Alexander, Neal; Halsey, Eric S.; McCall, Philip J.

2016-01-01

Dengue is an arthropod-borne virus of great public health importance, and control of its mosquito vectors is currently the only available method for prevention. Previous research has suggested that insecticide treated curtains (ITCs) can lower dengue vector infestations in houses. This observational study investigated individual and household-level socio-demographic factors associated with correct and consistent use of ITCs in Iquitos, Peru. A baseline knowledge, attitudes, and practices (KAP) survey was administered to 1,333 study participants, and ITCs were then distributed to 593 households as part of a cluster-randomized trial. Follow up KAP surveys and ITC-monitoring checklists were conducted at 9, 18, and 27 months post-ITC distribution. At 9 months post-distribution, almost 70% of ITCs were hanging properly (e.g. hanging fully extended or tied up), particularly those hung on walls compared to other locations. Proper ITC hanging dropped at 18 months to 45.7%. The odds of hanging ITCs correctly and consistently were significantly greater among those participants who were housewives, knew three or more correct symptoms of dengue and at least one correct treatment for dengue, knew a relative or close friend who had had dengue, had children sleeping under a mosquito net, or perceived a change in the amount of mosquitoes in the home. Additionally, the odds of recommending ITCs in the future were significantly greater among those who perceived a change in the amount of mosquitoes in the home (e.g. perceived the ITCs to be effective). Despite various challenges associated with the sustained effectiveness of the selected ITCs, almost half of the ITCs were still hanging at 18 months, suggesting a feasible vector control strategy for sustained community use. PMID:26967157

Identification of insecticidal principals from cucumber seed oil against the yellow fever mosquito, Aedes aegypti

USDA-ARS?s Scientific Manuscript database

The yellow fever mosquito, Aedes aegypti, is one of the most medically important mosquito species due to its ability to spread viruses of yellow fever, dengue fever and Zika in humans. In this study, the insecticidal activity of seventeen plant essential oils were evaluated to toxicity by topical a...

Equity trends in ownership of insecticide-treated nets in 19 sub-Saharan African countries.

PubMed

Taylor, Cameron; Florey, Lia; Ye, Yazoume

2017-05-01

To examine the change in equity of insecticide-treated net (ITN) ownership among 19 malaria-endemic countries in sub-Saharan Africa before and after the launch of the Cover The Bed Net Gap initiative. To assess change in equity in ownership of at least one ITN by households from different wealth quintiles, we used data from Demographic and Health Surveys and Malaria Indicator Surveys. We assigned surveys conducted before the launch (2003-2008) as baseline surveys and surveys conducted between 2009-2014 as endpoint surveys. We did country-level and pooled multicountry analyses. Pooled analyses based on malaria transmission risk, were done by dividing geographical zones into either low- and intermediate-risk or high-risk. To assess changes in equity, we calculated the Lorenz concentration curve and concentration index (C-index). Out of the 19 countries we assessed, 13 countries showed improved equity between baseline and endpoint surveys and two countries showed no changes. Four countries displayed worsened equity, two favouring the poorer households and two favouring the richer. The multicountry pooled analysis showed an improvement in equity (baseline survey C-index: 0.11; 95% confidence interval, CI: 0.10 to 0.11; and endpoint survey C-index: 0.00; 95% CI: -0.01 to 0.00). Similar trends were seen in both low- and intermediate-risk and high-risk zones. The mass ITN distribution campaigns to increase coverage, linked to the launch of the Cover The Bed Net Gap initiative, have led to improvement in coverage of ITN ownership across sub-Saharan Africa with significant reduction in inequity among wealth quintiles.

'Repel all biters': an enhanced collection of endophilic Anopheles gambiae and Anopheles arabiensis in CDC light-traps, from the Kagera Region of Tanzania, in the presence of a combination mosquito net impregnated with piperonyl butoxide and permethrin.

PubMed

LeClair, Corey; Cronery, Judith; Kessy, Enock; Tomás, Elsa V E; Kulwa, Yohannes; Mosha, Franklin W; Rowland, Mark; Protopopoff, Natacha; Derek Charlwood, J

2017-08-15

Mosquito nets containing synergists designed to overcome metabolic resistance mechanisms in vectors have been developed. These may enhance excitability in the mosquitoes and affect how they respond to CDC light-traps. Investigating the behaviour of vectors of disease in relation to novel mosquito nets is, therefore, essential for the design of sampling and surveillance systems. In an initial experiment in Muleba, Tanzania, nine bedrooms from three housing clusters were sampled. CDC light-traps were operated indoors next to occupied untreated nets (UTN), Olyset ® long lasting insecticidal net (LLIN) and Olyset Plus ® LLIN containing piperonyl butoxide (PBO) synergist. Nets were rotated daily between the nine rooms over nine nights. A further series of experiments using the nets on alternate nights in a single room was undertaken during the short rains. Anopheles gambiae s.l. were collected in CDC light-traps, a window-trap and Furvela tent-trap. Anopheles gambiae s.l. were identified to species by polymerase chain reaction (PCR). In the initial experiment 97.7% of the 310 An. gambiae s.l. were An. gambiae s.s., the remainder being Anopheles arabiensis. The number of mosquitoes collected from 81 light-trap collections was greater in the presence of an Olyset [density rate ratio 1.81, 95% CI (1.22-2.67), p = 0.003] relative to an UTN. In a second experiment, in the wet season 84% of the 180 An. gambiae s.l. identified were An. arabiensis. The number of An. gambiae s.l. collected from a light-trap compared to a tent-trap was significantly higher when an Olyset Plus net was used compared to an UTN. Survival of the mosquitoes in the window trap was not reduced by the use of an Olyset Plus net in the bedroom relative to an Olyset net. Mosquitoes entering bedrooms, even those susceptible to pyrethroids, were not killed by contact with an Olyset Plus LLIN. The enhanced numbers of An. gambiae or An. arabiensis collected in light-traps when a treated net is used requires

Evaluation of the efficacy of DDT indoor residual spraying and long-lasting insecticidal nets against insecticide resistant populations of Anopheles arabiensis Patton (Diptera: Culicidae) from Ethiopia using experimental huts

PubMed Central

2014-01-01

Background Indoor Residual Spraying (IRS) and Long-Lasting Insecticidal nets (LLINs) are major malaria vector control tools in Ethiopia. However, recent reports from different parts of the country showed that populations of Anopheles arabiensis, the principal malaria vector, have developed resistance to most families of insecticides recommended for public health use which may compromise the efficacy of both of these key vector control interventions. Thus, this study evaluated the efficacy of DDT IRS and LLINs against resistant populations of An. arabiensis using experimental huts in Asendabo area, southwestern Ethiopia. Methods The susceptibility status of populations of An. arabiensis was assessed using WHO test kits to DDT, deltamethrin, malathion, lambda-cyhalothrin, fenitrothion and bendiocarb. The efficacy of LLIN (PermaNet® 2.0), was evaluated using the WHO cone bioassay. Moreover, the effect of the observed resistance against malaria vector control interventions (DDT IRS and LLINs) were assessed using experimental huts. Results The findings of this study revealed that populations of An. arabiensis were resistant to DDT, deltamethrin, lambda-cyhalothrin and malathion with mortality rates of 1.3%, 18.8%, 36.3% and 72.5%, respectively but susceptible to fenitrothion and bendiocarb with mortality rates of 98.81% and 97.5%, respectively. The bio-efficacy test of LLIN (PermaNet® 2.0) against An. arabiensis revealed that the mosquito population showed moderate knockdown (64%) and mortality (78%). Moreover, mosquito mortalities in DDT sprayed huts and in huts with LLINs were not significantly different (p > 0.05) from their respective controls. Conclusion The evaluation of the efficacy of DDT IRS and LLINs using experimental huts showed that both vector control tools had only low to moderate efficacy against An. arabiensis populations from Ethiopia. Despite DDT being replaced by carbamates for IRS, the low efficacy of LLINs against the resistant population of An

Insecticidal activity of Leptodactylus knudseni and Phyllomedusa vaillantii crude skin secretions against the mosquitoes Anopheles darlingi and Aedes aegypti

PubMed Central

2014-01-01

Background Mosquitoes are important vectors of several diseases, including malaria and dengue, and control measures are mostly performed using chemical insecticides. Unfortunately, mosquito resistance to commonly applied insecticides is widespread. Therefore, a prospection for new molecules with insecticidal activity based on Amazon biodiversity using the anurans Leptodactylus knudseni and Phyllomedusa vaillantii was performed against the mosquito species Anopheles darlingi and Aedes aegypti. Methods The granular secretion from anuran skin was obtained by manual stimulation, and lethal concentrations (LCs) for larvicidal and adulticidal tests were calculated using concentrations from 1-100 ppm. The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species. Results The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species. The calculated LC50 of L. knudseni skin secretions against An. darlingi was 0.15 and 0.2 ppm for adults and larvae, respectively, but much higher for Ae. aegypti, i.e., 19 and 38 ppm, respectively. Interestingly, the calculated LCs50 of P. vaillantii against both mosquito species in adults were similar, 1.8 and 2.1 ppm, respectively, but the LC50 for An. darlingi larvae was much lower (0.4 ppm) than for Ae aegypti (2.1 ppm). Conclusions The present experiments indicate that skin secretions from L. knudseni and P. vaillantii contain bioactive molecules with potent insecticide activity. The isolation and characterization of skin secretions components will provide new insights for potential insecticidal molecules. PMID:25165469

Efficacy of permethrin treated long-lasting insecticidal nets on malaria transmission and observations on the perceived side effects, collateral benefits and human safety in a hyperendemic tribal area of Orissa, India.

PubMed

Sharma, Surya K; Tyagi, Prajesh K; Upadhyay, Ashok K; Haque, Mohammed A; Mohanty, Suman S; Raghavendra, Kamaraju; Dash, Aditya P

2009-11-01

Studies were conducted on the efficacy of Olyset nets-a long-lasting insecticidal net (LLIN) factory treated with 2% (w/w) permethrin on malaria transmission in an area under the influence of pyrethroid susceptible vector species Anopheles culicifacies and A. fluviatilis in Sundargarh District, Orissa, India. The study area comprised 22 villages that were randomized into three clusters and designated as Olyset net, untreated net, and no net area. Malaria incidence in the study population was measured through longitudinal active surveillance at fortnightly intervals. There was a reduction of 65-70% in malaria incidence in Olyset net area as compared to the control areas. The attack rate of Plasmodium falciparum or number of episodes per person per year in different age groups also showed significant reduction in Olyset net area as compared to untreated net and no net areas. Cross-sectional point prevalence surveys showed 45.7% reduction of malaria prevalence in Olyset net users, whereas there was an increase of 33.3% and 51% in untreated net and no net villages respectively. The compliance rate of Olyset net usage in the study population was 80-98% during different months, whereas it was between 70% and 90% for untreated nets. There were minimal complains of skin irritation (4%), itching (8%) and eye irritation (1.2%). However, these effects were only transitory in nature lasting for few hours of the first usage. Olyset nets also provided collateral benefits in terms of relief not only from mosquitoes and malaria but also from other household pests such as head lice, bed bugs, cockroaches, ants and houseflies. The Olyset nets were found to be safe to humans as no adverse event was recorded in the net users that can be attributed to the use of net. The study showed that Olyset nets are effective personal protection tool that can be used in a community based intervention programme.

Lantos-Hyde United States Government Malaria Strategy, 2009-2014

DTIC Science & Technology

2010-04-25

Long lasting insecticide -treated nets (LLINs); • Indoor residual spraying (IRS) with insecticides ; • Intermittent preventive treatment of...measures: insecticide -treated mosquito nets (ITNs); indoor residual spraying (IRS) of insecticides ; artemisinin-based combination therapy (ACTs); and...is national policy. Indoor residual spraying : Between 2005 and 2009, PMI supported the introduction or

Comparative analysis of response to selection with three insecticides in the dengue mosquito Aedes aegypti using mRNA sequencing

PubMed Central

2014-01-01

Background Mosquito control programmes using chemical insecticides are increasingly threatened by the development of resistance. Such resistance can be the consequence of changes in proteins targeted by insecticides (target site mediated resistance), increased insecticide biodegradation (metabolic resistance), altered transport, sequestration or other mechanisms. As opposed to target site resistance, other mechanisms are far from being fully understood. Indeed, insecticide selection often affects a large number of genes and various biological processes can hypothetically confer resistance. In this context, the aim of the present study was to use RNA sequencing (RNA-seq) for comparing transcription level and polymorphism variations associated with adaptation to chemical insecticides in the mosquito Aedes aegypti. Biological materials consisted of a parental susceptible strain together with three child strains selected across multiple generations with three insecticides from different classes: the pyrethroid permethrin, the neonicotinoid imidacloprid and the carbamate propoxur. Results After ten generations, insecticide-selected strains showed elevated resistance levels to the insecticides used for selection. RNA-seq data allowed detecting over 13,000 transcripts, of which 413 were differentially transcribed in insecticide-selected strains as compared to the susceptible strain. Among them, a significant enrichment of transcripts encoding cuticle proteins, transporters and enzymes was observed. Polymorphism analysis revealed over 2500 SNPs showing > 50% allele frequency variations in insecticide-selected strains as compared to the susceptible strain, affecting over 1000 transcripts. Comparing gene transcription and polymorphism patterns revealed marked differences among strains. While imidacloprid selection was linked to the over transcription of many genes, permethrin selection was rather linked to polymorphism variations. Focusing on detoxification enzymes

Impact of malaria related messages on insecticide-treated net (ITN) use for malaria prevention in Ghana.

PubMed

Owusu Adjah, Ebenezer S; Panayiotou, Andrie G

2014-03-28

Media messages have been used in Ghana to promote insecticide-treated net (ITN)/bed net usage in an effort to impact on malaria prevention. The aim of this study was to assess the effect of such malaria-related messages delivered through electronic/print media and by volunteers/health workers on the use of ITNs by children living in a household. Data was collected from September to November of 2008 using a structured, interviewer-administered questionnaire by the Ghana Statistical Service as part of a national demographic and health survey (DHS). Secondary data analysis was performed on the collected data using multivariate logistic regression for both individual messages and a composite (any of) message variable. From the 11,788 households surveyed, 45% had at least one net. Households with male heads were more likely to have a child sleeping under a bed net the previous night (p = 0.0001). Individual Messages delivered by a health worker or a dedicated radio programme, had the highest effect for one or more children sleeping under a net the night before (OR(adjusted) = 1.65; 95% CI = 1.44 to 1.88 and OR(adjusted) = 1.26; 95% CI =1.12 to 1.42 respectively) while hearing any of the eight messages (composite score) resulted in the highest odds for one or more children (OR(adjusted) = 3.06; 95% CI = 2.27 to 4.12) sleeping under a bed net. Efforts to relate ITN messages to the public are very useful in increasing use of bed nets and having multiple ways of reaching the public increases their effect, with the biggest effect seen when health workers and volunteers were used to deliver malaria-related messages to the public.

A systematic review of mosquito coils and passive emanators: defining recommendations for spatial repellency testing methodologies.

PubMed

Ogoma, Sheila B; Moore, Sarah J; Maia, Marta F

2012-12-07

Mosquito coils, vaporizer mats and emanators confer protection against mosquito bites through the spatial action of emanated vapor or airborne pyrethroid particles. These products dominate the pest control market; therefore, it is vital to characterize mosquito responses elicited by the chemical actives and their potential for disease prevention. The aim of this review was to determine effects of mosquito coils and emanators on mosquito responses that reduce human-vector contact and to propose scientific consensus on terminologies and methodologies used for evaluation of product formats that could contain spatial chemical actives, including indoor residual spraying (IRS), long lasting insecticide treated nets (LLINs) and insecticide treated materials (ITMs). PubMed, (National Centre for Biotechnology Information (NCBI), U.S. National Library of Medicine, NIH), MEDLINE, LILAC, Cochrane library, IBECS and Armed Forces Pest Management Board Literature Retrieval System search engines were used to identify studies of pyrethroid based coils and emanators with key-words "Mosquito coils" "Mosquito emanators" and "Spatial repellents". It was concluded that there is need to improve statistical reporting of studies, and reach consensus in the methodologies and terminologies used through standardized testing guidelines. Despite differing evaluation methodologies, data showed that coils and emanators induce mortality, deterrence, repellency as well as reduce the ability of mosquitoes to feed on humans. Available data on efficacy outdoors, dose-response relationships and effective distance of coils and emanators is inadequate for developing a target product profile (TPP), which will be required for such chemicals before optimized implementation can occur for maximum benefits in disease control.

Cross-induction of detoxification genes by environmental xenobiotics and insecticides in the mosquito Aedes aegypti: impact on larval tolerance to chemical insecticides.

PubMed

Poupardin, Rodolphe; Reynaud, Stéphane; Strode, Clare; Ranson, Hilary; Vontas, John; David, Jean-Philippe

2008-05-01

The effect of exposure of Aedes aegypti larvae to sub-lethal doses of the pyrethroid insecticide permethrin, the organophosphate temephos, the herbicide atrazine, the polycyclic aromatic hydrocarbon fluoranthene and the heavy metal copper on their subsequent tolerance to insecticides, detoxification enzyme activities and expression of detoxification genes was investigated. Bioassays revealed a moderate increase in larval tolerance to permethrin following exposure to fluoranthene and copper while larval tolerance to temephos increased moderately after exposure to atrazine, copper and permethrin. Cytochrome P450 monooxygenases activities were induced in larvae exposed to permethrin, fluoranthene and copper while glutathione S-transferase activities were induced after exposure to fluoranthene and repressed after exposure to copper. Microarray screening of the expression patterns of all detoxification genes following exposure to each xenobiotic with the Aedes Detox Chip identified multiple genes induced by xenobiotics and insecticides. Further expression studies using real-time quantitative PCR confirmed the induction of multiple CYP genes and one carboxylesterase gene by insecticides and xenobiotics. Overall, this study reveals the potential of xenobiotics found in polluted mosquito breeding sites to affect their tolerance to insecticides, possibly through the cross-induction of particular detoxification genes. Molecular mechanisms involved and impact on mosquito control strategies are discussed.

Role of G-protein-coupled receptor-related genes in insecticide resistance of the mosquito, Culex quinquefasciatus.

PubMed

Li, Ting; Liu, Lena; Zhang, Lee; Liu, Nannan

2014-09-29

G-protein-coupled receptors regulate signal transduction pathways and play diverse and pivotal roles in the physiology of insects, however, the precise function of GPCRs in insecticide resistance remains unclear. Using quantitative RT-PCR and functional genomic methods, we, for the first time, explored the function of GPCRs and GPCR-related genes in insecticide resistance of mosquitoes, Culex quinquefasciatus. A comparison of the expression of 115 GPCR-related genes at a whole genome level between resistant and susceptible Culex mosquitoes identified one and three GPCR-related genes that were up-regulated in highly resistant Culex mosquito strains, HAmCq(G8) and MAmCq(G6), respectively. To characterize the function of these up-regulated GPCR-related genes in resistance, the up-regulated GPCR-related genes were knockdown in HAmCq(G8) and MAmCq(G6) using RNAi technique. Knockdown of these four GPCR-related genes not only decreased resistance of the mosquitoes to permethrin but also repressed the expression of four insecticide resistance-related P450 genes, suggesting the role of GPCR-related genes in resistance is involved in the regulation of resistance P450 gene expression. This results help in understanding of molecular regulation of resistance development in Cx. quinquefasciatus.

Annotated differentially expressed salivary proteins of susceptible and insecticide-resistant mosquitoes of Anopheles stephensi.

PubMed

Vijay, Sonam; Rawal, Ritu; Kadian, Kavita; Raghavendra, Kamaraju; Sharma, Arun

2015-01-01

Vector control is one of the major global strategies for control of malaria. However, the major obstacle for vector control is the development of multiple resistances to organochlorine, organophosphorus insecticides and pyrethroids that are currently being used in public health for spraying and in bednets. Salivary glands of vectors are the first target organ for human-vector contact during biting and parasite-vector contact prior to parasite development in the mosquito midguts. The salivary glands secrete anti-haemostatic, anti-inflammatory biologically active molecules to facilitate blood feeding from the host and also inadvertently inject malaria parasites into the vertebrate host. The Anopheles stephensi mosquito, an urban vector of malaria to both human and rodent species has been identified as a reference laboratory model to study mosquito-parasite interactions. In this study, we adopted a conventional proteomic approach of 2D-electrophoresis coupled with MALDI-TOF mass spectrometry and bioinformatics to identify putative differentially expressed annotated functional salivary proteins between An. stephensi susceptible and multiresistant strains with same genetic background. Our results show 2D gel profile and MALDI-TOF comparisons that identified 31 differentially expressed putative modulated proteins in deltamethrin/DDT resistant strains of An. stephensi. Among these 15 proteins were found to be upregulated and 16 proteins were downregulated. Our studies interpret that An. stephensi (multiresistant) caused an upregulated expression of proteins and enzymes like cytochrome 450, short chain dehyrdogenase reductase, phosphodiesterase etc that may have an impact in insecticide resistance and xenobiotic detoxification. Our study elucidates a proteomic response of salivary glands differentially regulated proteins in response to insecticide resistance development which include structural, redox and regulatory enzymes of several pathways. These identified proteins

Equity trends in ownership of insecticide-treated nets in 19 sub-Saharan African countries

PubMed Central

Florey, Lia; Ye, Yazoume

2017-01-01

Abstract Objective To examine the change in equity of insecticide-treated net (ITN) ownership among 19 malaria-endemic countries in sub-Saharan Africa before and after the launch of the Cover The Bed Net Gap initiative. Methods To assess change in equity in ownership of at least one ITN by households from different wealth quintiles, we used data from Demographic and Health Surveys and Malaria Indicator Surveys. We assigned surveys conducted before the launch (2003–2008) as baseline surveys and surveys conducted between 2009–2014 as endpoint surveys. We did country-level and pooled multicountry analyses. Pooled analyses based on malaria transmission risk, were done by dividing geographical zones into either low- and intermediate-risk or high-risk. To assess changes in equity, we calculated the Lorenz concentration curve and concentration index (C-index). Findings Out of the 19 countries we assessed, 13 countries showed improved equity between baseline and endpoint surveys and two countries showed no changes. Four countries displayed worsened equity, two favouring the poorer households and two favouring the richer. The multicountry pooled analysis showed an improvement in equity (baseline survey C-index: 0.11; 95% confidence interval, CI: 0.10 to 0.11; and endpoint survey C-index: 0.00; 95% CI: −0.01 to 0.00). Similar trends were seen in both low- and intermediate-risk and high-risk zones. Conclusion The mass ITN distribution campaigns to increase coverage, linked to the launch of the Cover The Bed Net Gap initiative, have led to improvement in coverage of ITN ownership across sub-Saharan Africa with significant reduction in inequity among wealth quintiles. PMID:28479633

Insecticide resistance status in Anopheles gambiae in southern Benin

PubMed Central

2010-01-01

Background The emergence of pyrethroid resistance in Anopheles gambiae has become a serious concern to the future success of malaria control. In Benin, the National Malaria Control Programme has recently planned to scaling up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) for malaria prevention. It is, therefore, crucial to monitor the level and type of insecticide resistance in An. gambiae, particularly in southern Benin where reduced efficacy of insecticide-treated nets (ITNs) and IRS has previously been reported. Methods The protocol was based on mosquito collection during both dry and rainy seasons across forty districts selected in southern Benin. Bioassay were performed on adults collected from the field to assess the susceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. The species within An. gambiae complex, molecular form and presence of kdr and ace-1 mutations were determined by PCR. Results Strong resistance to permethrin and DDT was found in An. gambiae populations from southern Benin, except in Aglangandan where mosquitoes were fully susceptible (mortality 100%) to all insecticides tested. PCR showed the presence of two sub-species of An. gambiae, namely An. gambiae s.s, and Anopheles melas, with a predominance for An. gambiae s.s (98%). The molecular M form of An. gambiae was predominant in southern Benin (97%). The kdr mutation was detected in all districts at various frequency (1% to 95%) whereas the Ace-1 mutation was found at a very low frequency (≤ 5%). Conclusion This study showed a widespread resistance to permethrin in An. gambiae populations from southern Benin, with a significant increase of kdr frequency compared to what was observed previously in Benin. The low frequency of Ace-1 recorded in all populations is encouraging for the use of bendiocarb as an alternative insecticide to pyrethroids for IRS

Evaluation of the 2011 long-lasting, insecticide-treated net distribution for universal coverage in Togo.

PubMed

Stevens, Elizabeth R; Aldridge, Abigail; Degbey, Yawo; Pignandi, Akou; Dorkenoo, Monique A; Hugelen-Padin, Justin

2013-05-16

Malaria remains a substantial public health problem in Togo. An integrated child health campaign was conducted in Togo in October 2011. This campaign included a component of free distribution of 2,799,800 long-lasting, insecticide-treated nets (LLINs) to households throughout Togo. This distribution marked the first effort in Togo at universal LLIN coverage and was not targeted specifically to children under five years and pregnant women, but to all household members. This study reports the results of the LLIN distribution campaign in terms of bed net possession and utilization. A representative household survey was implemented during the rainy season nine months after the LLIN distribution component of the campaign. Some 6,015 households selected through two stages of probability proportion to size stratified random sampling were interviewed using a brief questionnaire that included a demographic section with questions on the number of household members and sleeping spaces, and a campaign participation section with questions used to evaluate non-LLIN aspects of the campaign. A net roster listed all nets and their characteristics, and a household roster listed all members and visitors with information about bed net use. The questions addressed different aspects of bed net and LLIN possession and utilization. Crude weighted frequencies, percentages, and t- tests of association were calculated using the Stata 12.0 Survey features. Possession of at least one bed net and/or LLIN increased from 41.3% to 96.7% (P <0.001). Household possession of at least one campaign LLIN was 93.3%. Report LLIN among pregnant women was 77.5% and 79.3% for children under five. For the general population LLIN use was 68.3%. Due to the gap in LLIN possession and use and the significant number of individuals reporting a lack of nets as a reason for non-use, additional national LLIN distribution campaigns with a stronger educational component need to be implemented in order increase the use

Cost-Effectiveness of Long-Lasting Insecticide-Treated Hammocks in Preventing Malaria in South-Central Vietnam

PubMed Central

Morel, Chantal M.; Thang, Ngo Duc; Erhart, Annette; Xa, Nguyen Xuan; Peeters Grietens, Koen; Xuan Hung, Le; Thuan, Le Khan; Van Ky, Pham; Hung, Nguyen Manh; Coosemans, Marc; D'Alessandro, Umberto; Mills, Anne

2013-01-01

Background Despite much success in reducing the burden of malaria in Vietnam, pockets of malaria persist and eliminating them remains an important development goal. In central Vietnam, insecticide-treated hammocks have recently been introduced to help counter the disease in the highly forested, mountainous areas, where other measures have so far been unsuccessful. This study assesses the cost-effectiveness of using long-lasting insecticide-treated hammocks in this area. Methods and Findings This cost-effectiveness study was run alongside a randomized control trial testing the efficacy of the long-lasting insecticide-treated hammocks. Data were collected through an exit survey, a household survey, expenditure records and key informant interviews. The study estimates that under normal (non-trial) conditions the total net societal cost per malaria episode averted in using long-lasting insecticide-treated hammocks in this area was 126 USD. Cost per hammock, including insecticidal netting, sewing, transport, and distribution was found to be approximately 11.76 USD per hammock. Average savings per episode averted were estimated to be $14.60 USD for the health system and 14.37 USD for households (including both direct and indirect cost savings). The study estimates that the annual financial outlay required of government to implement this type of programme to be 3.40 USD per person covered per year. Conclusion The study finds that the use of a hammock intervention could represent good value for money to help prevent malaria in more remote areas, where traditional control measures such as insecticide-treated bednets and indoor residual spraying are insufficient or inappropriate to control malaria. However, the life span of the hammock–the number of years over which it effectively deters mosquitoes–has a significant impact on the cost-effectiveness of the intervention and study results should be interpreted in light of the evidence on effectiveness gathered in the years

A Modified Experimental Hut Design for Studying Responses of Disease-Transmitting Mosquitoes to Indoor Interventions: The Ifakara Experimental Huts

PubMed Central

Okumu, Fredros O.; Moore, Jason; Mbeyela, Edgar; Sherlock, Mark; Sangusangu, Robert; Ligamba, Godfrey; Russell, Tanya; Moore, Sarah J.

2012-01-01

Differences between individual human houses can confound results of studies aimed at evaluating indoor vector control interventions such as insecticide treated nets (ITNs) and indoor residual insecticide spraying (IRS). Specially designed and standardised experimental huts have historically provided a solution to this challenge, with an added advantage that they can be fitted with special interception traps to sample entering or exiting mosquitoes. However, many of these experimental hut designs have a number of limitations, for example: 1) inability to sample mosquitoes on all sides of huts, 2) increased likelihood of live mosquitoes flying out of the huts, leaving mainly dead ones, 3) difficulties of cleaning the huts when a new insecticide is to be tested, and 4) the generally small size of the experimental huts, which can misrepresent actual local house sizes or airflow dynamics in the local houses. Here, we describe a modified experimental hut design - The Ifakara Experimental Huts- and explain how these huts can be used to more realistically monitor behavioural and physiological responses of wild, free-flying disease-transmitting mosquitoes, including the African malaria vectors of the species complexes Anopheles gambiae and Anopheles funestus, to indoor vector control-technologies including ITNs and IRS. Important characteristics of the Ifakara experimental huts include: 1) interception traps fitted onto eave spaces and windows, 2) use of eave baffles (panels that direct mosquito movement) to control exit of live mosquitoes through the eave spaces, 3) use of replaceable wall panels and ceilings, which allow safe insecticide disposal and reuse of the huts to test different insecticides in successive periods, 4) the kit format of the huts allowing portability and 5) an improved suite of entomological procedures to maximise data quality. PMID:22347415

Environmentally friendly tool to control mosquito populations without risk of insecticide resistance: the Lehmann’s funnel entry trap

PubMed Central

2013-01-01

Background Current malaria control strategies have cut down the malaria burden in many endemic areas, however the emergence and rapid spread of insecticide and drug resistance undermine the success of these efforts. There is growing concern that malaria eradication will not be achieved without the introduction of novel control tools. One approach that has been developed in the last few years is based on house screening to reduce indoor mosquito vector densities and consequently decrease malaria transmission. Here screening and trapping were combined in one tool to control mosquito populations. The trap does not require an insecticide or even an attractant, yet it effectively collects incoming resistant and susceptible mosquitoes and kills them. Results Performance of the funnel entry trap was tested in low and high malaria vector density areas. An overall reduction of 70 to 80% of mosquito density was seen in both. Species and molecular forms of Anopheles gambiae identification indicated no variation in the number of Anopheles arabiensis and the molecular forms of An. gambiae between houses and traps. Mosquitoes collected in the traps and in houses were highly resistant to pyrethroids (0.9 kdr-based mechanism). Conclusion There is a global consensus that new intervention tools are needed to cross the last miles in malaria elimination/eradication. The funnel entry trap showed excellent promise in suppressing mosquito densities even in area of high insecticide resistance. It requires no chemicals and is self-operated. PMID:23758904

Factors associated with mosquito net use by individuals in households owning nets in Ethiopia

PubMed Central

2011-01-01

Background Ownership of insecticidal mosquito nets has dramatically increased in Ethiopia since 2006, but the proportion of persons with access to such nets who use them has declined. It is important to understand individual level net use factors in the context of the home to modify programmes so as to maximize net use. Methods Generalized linear latent and mixed models (GLLAMM) were used to investigate net use using individual level data from people living in net-owning households from two surveys in Ethiopia: baseline 2006 included 12,678 individuals from 2,468 households and a sub-sample of the Malaria Indicator Survey (MIS) in 2007 included 14,663 individuals from 3,353 households. Individual factors (age, sex, pregnancy); net factors (condition, age, net density); household factors (number of rooms [2006] or sleeping spaces [2007], IRS, women's knowledge and school attendance [2007 only], wealth, altitude); and cluster level factors (rural or urban) were investigated in univariate and multi-variable models for each survey. Results In 2006, increased net use was associated with: age 25-49 years (adjusted (a) OR = 1.4, 95% confidence interval (CI) 1.2-1.7) compared to children U5; female gender (aOR = 1.4; 95% CI 1.2-1.5); fewer nets with holes (Ptrend = 0.002); and increasing net density (Ptrend < 0.001). Reduced net use was associated with: age 5-24 years (aOR = 0.2; 95% CI 0.2-0.3). In 2007, increased net use was associated with: female gender (aOR = 1.3; 95% CI 1.1-1.6); fewer nets with holes (aOR [all nets in HH good] = 1.6; 95% CI 1.2-2.1); increasing net density (Ptrend < 0.001); increased women's malaria knowledge (Ptrend < 0.001); and urban clusters (aOR = 2.5; 95% CI 1.5-4.1). Reduced net use was associated with: age 5-24 years (aOR = 0.3; 95% CI 0.2-0.4); number of sleeping spaces (aOR [per additional space] = 0.6, 95% CI 0.5-0.7); more old nets (aOR [all nets in HH older than 12 months] = 0.5; 95% CI 0.3-0.7); and increasing household altitude

Navy Entomologists Assist CDC’s Fight Against Malaria

DTIC Science & Technology

2013-01-01

long - lasting insec- ticide treated bed nets (LLINs): 2) indoor residual spraying (IRS) of living quarters using long - lasting residual ... insecticide susceptible malaria mosquitoes for residual insecticide testing of IRS sprayed walls and long lasting insecticide -treated bed nets . which is...the Navy Entomology Center of Excellence sprays panels, made of materials

The central role of mosquito cytochrome P450 CYP6Zs in insecticide detoxification revealed by functional expression and structural modelling.

PubMed

Chandor-Proust, Alexia; Bibby, Jaclyn; Régent-Kloeckner, Myriam; Roux, Jessica; Guittard-Crilat, Emilie; Poupardin, Rodolphe; Riaz, Muhammad Asam; Paine, Mark; Dauphin-Villemant, Chantal; Reynaud, Stéphane; David, Jean-Philippe

2013-10-01

The resistance of mosquitoes to chemical insecticides is threatening vector control programmes worldwide. Cytochrome P450 monooxygenases (CYPs) are known to play a major role in insecticide resistance, allowing resistant insects to metabolize insecticides at a higher rate. Among them, members of the mosquito CYP6Z subfamily, like Aedes aegypti CYP6Z8 and its Anopheles gambiae orthologue CYP6Z2, have been frequently associated with pyrethroid resistance. However, their role in the pyrethroid degradation pathway remains unclear. In the present study, we created a genetically modified yeast strain overexpressing Ae. aegypti cytochrome P450 reductase and CYP6Z8, thereby producing the first mosquito P450-CPR (NADPH-cytochrome P450-reductase) complex in a yeast recombinant system. The results of the present study show that: (i) CYP6Z8 metabolizes PBAlc (3-phenoxybenzoic alcohol) and PBAld (3-phenoxybenzaldehyde), common pyrethroid metabolites produced by carboxylesterases, producing PBA (3-phenoxybenzoic acid); (ii) CYP6Z8 transcription is induced by PBAlc, PBAld and PBA; (iii) An. gambiae CYP6Z2 metabolizes PBAlc and PBAld in the same way; (iv) PBA is the major metabolite produced in vivo and is excreted without further modification; and (v) in silico modelling of substrate-enzyme interactions supports a similar role of other mosquito CYP6Zs in pyrethroid degradation. By playing a pivotal role in the degradation of pyrethroid insecticides, mosquito CYP6Zs thus represent good targets for mosquito-resistance management strategies.

Environmental fate model for ultra-low-volume insecticide applications used for adult mosquito management

USGS Publications Warehouse

Schleier, Jerome J.; Peterson, Robert K.D.; Irvine, Kathryn M.; Marshall, Lucy M.; Weaver, David K.; Preftakes, Collin J.

2012-01-01

One of the more effective ways of managing high densities of adult mosquitoes that vector human and animal pathogens is ultra-low-volume (ULV) aerosol applications of insecticides. The U.S. Environmental Protection Agency uses models that are not validated for ULV insecticide applications and exposure assumptions to perform their human and ecological risk assessments. Currently, there is no validated model that can accurately predict deposition of insecticides applied using ULV technology for adult mosquito management. In addition, little is known about the deposition and drift of small droplets like those used under conditions encountered during ULV applications. The objective of this study was to perform field studies to measure environmental concentrations of insecticides and to develop a validated model to predict the deposition of ULV insecticides. The final regression model was selected by minimizing the Bayesian Information Criterion and its prediction performance was evaluated using k-fold cross validation. Density of the formulation and the density and CMD interaction coefficients were the largest in the model. The results showed that as density of the formulation decreases, deposition increases. The interaction of density and CMD showed that higher density formulations and larger droplets resulted in greater deposition. These results are supported by the aerosol physics literature. A k-fold cross validation demonstrated that the mean square error of the selected regression model is not biased, and the mean square error and mean square prediction error indicated good predictive ability.

A comparative cost analysis of insecticide-treated nets and indoor residual spraying in highland Kenya.

PubMed

Guyatt, H L; Kinnear, J; Burini, M; Snow, R W

2002-06-01

The relative cost of indoor residual house-spraying (IRS) versus insecticide-treated bednets (ITNs) forms part of decisions regarding selective malaria prevention. This paper presents a cost comparison of these two approaches as recently implemented by Merlin, a UK emergency relief organization funded through international donor support and working in the highland districts of Gucha and Kisii in Kenya. The financial costs (cash expenditures) and the economic costs (including the opportunity costs of using existing staff and volunteers, and an annualized cost for capital items) were assessed. The financial cost for IRS was US dollars 0.86 per person protected, compared with 4.21 dollars for ITNs (reducing to 3.42 dollars to the provider assuming cost recovery). The economic cost per person protected for IRS was 0.88 dollars, compared with 2.34 dollars for ITNs. The costs for ITNs were sensitive to the number of nets sold per community group ('efficiency'), as the delivery costs constituted upwards of 40% of the total cost. However, even marked increases in efficiency of these groups could not reduce the costs of ITNs to that comparable with IRS, except if more than one cycle of IRS was needed. The implications of predicted reductions in the cost of insecticide for both IRS and ITNs are also explored. The provision of itemized cost data allows predictions to be made on changes in the design of these programmes. Under almost all design scenarios, IRS would appear to be a more cost-efficient means of vector control in the Kenyan highlands.

Comparative performance of three experimental hut designs for measuring malaria vector responses to insecticides in Tanzania.

PubMed

Massue, Dennis J; Kisinza, William N; Malongo, Bernard B; Mgaya, Charles S; Bradley, John; Moore, Jason D; Tenu, Filemoni F; Moore, Sarah J

2016-03-15

Experimental huts are simplified, standardized representations of human habitations that provide model systems to evaluate insecticides used in indoor residual spray (IRS) and long-lasting insecticidal nets (LLINs) to kill disease vectors. Hut volume, construction materials and size of entry points impact mosquito entry and exposure to insecticides. The performance of three standard experimental hut designs was compared to evaluate insecticide used in LLINs. Field studies were conducted at the World Health Organization Pesticide Evaluation Scheme (WHOPES) testing site in Muheza, Tanzania. Three East African huts, three West African huts, and three Ifakara huts were compared using Olyset(®) and Permanet 2.0(®) versus untreated nets as a control. Outcomes measured were mortality, induced exophily (exit rate), blood feeding inhibition and deterrence (entry rate). Data were analysed using linear mixed effect regression and Bland-Altman comparison of paired differences. A total of 613 mosquitoes were collected in 36 nights, of which 13.5% were Anopheles gambiae sensu lato, 21% Anopheles funestus sensu stricto, 38% Mansonia species and 28% Culex species. Ifakara huts caught three times more mosquitoes than the East African and West African huts, while the West African huts caught significantly fewer mosquitoes than the other hut types. Mosquito densities were low, very little mosquito exit was measured in any of the huts with no measurable exophily caused by the use of either Olyset or Permanet. When the huts were directly compared, the West African huts measured greater exophily than other huts. As unholed nets were used in the experiments and few mosquitoes were captured, it was not possible to measure difference in feeding success either between treatments or hut types. In each of the hut types there was increased mortality when Permanet or Olyset were present inside the huts compared to the control, however this did not vary between the hut types. Both East African

Increasing Coverage and Decreasing Inequity in Insecticide-Treated Bed Net Use among Rural Kenyan Children

PubMed Central

Noor, Abdisalan M; Amin, Abdinasir A; Akhwale, Willis S; Snow, Robert W

2007-01-01

Background Inexpensive and efficacious interventions that avert childhood deaths in sub-Saharan Africa have failed to reach effective coverage, especially among the poorest rural sectors. One particular example is insecticide-treated bed nets (ITNs). In this study, we present repeat observations of ITN coverage among rural Kenyan homesteads exposed at different times to a range of delivery models, and assess changes in coverage across socioeconomic groups. Methods and Findings We undertook a study of annual changes in ITN coverage among a cohort of 3,700 children aged 0–4 y in four districts of Kenya (Bondo, Greater Kisii, Kwale, and Makueni) annually between 2004 and 2006. Cross-sectional surveys of ITN coverage were undertaken coincidentally with the incremental availability of commercial sector nets (2004), the introduction of heavily subsidized nets through clinics (2005), and the introduction of free mass distributed ITNs (2006). The changing prevalence of ITN coverage was examined with special reference to the degree of equity in each delivery approach. ITN coverage was only 7.1% in 2004 when the predominant source of nets was the commercial retail sector. By the end of 2005, following the expansion of heavily subsidized clinic distribution system, ITN coverage rose to 23.5%. In 2006 a large-scale mass distribution of ITNs was mounted providing nets free of charge to children, resulting in a dramatic increase in ITN coverage to 67.3%. With each subsequent survey socioeconomic inequity in net coverage sequentially decreased: 2004 (most poor [2.9%] versus least poor [15.6%]; concentration index 0.281); 2005 (most poor [17.5%] versus least poor [37.9%]; concentration index 0.131), and 2006 with near-perfect equality (most poor [66.3%] versus least poor [66.6%]; concentration index 0.000). The free mass distribution method achieved highest coverage among the poorest children, the highly subsidised clinic nets programme was marginally in favour of the least poor

Annotated Differentially Expressed Salivary Proteins of Susceptible and Insecticide-Resistant Mosquitoes of Anopheles stephensi

PubMed Central

Vijay, Sonam; Rawal, Ritu; Kadian, Kavita; Raghavendra, Kamaraju; Sharma, Arun

2015-01-01

Vector control is one of the major global strategies for control of malaria. However, the major obstacle for vector control is the development of multiple resistances to organochlorine, organophosphorus insecticides and pyrethroids that are currently being used in public health for spraying and in bednets. Salivary glands of vectors are the first target organ for human-vector contact during biting and parasite-vector contact prior to parasite development in the mosquito midguts. The salivary glands secrete anti-haemostatic, anti-inflammatory biologically active molecules to facilitate blood feeding from the host and also inadvertently inject malaria parasites into the vertebrate host. The Anopheles stephensi mosquito, an urban vector of malaria to both human and rodent species has been identified as a reference laboratory model to study mosquito—parasite interactions. In this study, we adopted a conventional proteomic approach of 2D-electrophoresis coupled with MALDI-TOF mass spectrometry and bioinformatics to identify putative differentially expressed annotated functional salivary proteins between An. stephensi susceptible and multiresistant strains with same genetic background. Our results show 2D gel profile and MALDI-TOF comparisons that identified 31 differentially expressed putative modulated proteins in deltamethrin/DDT resistant strains of An. stephensi. Among these 15 proteins were found to be upregulated and 16 proteins were downregulated. Our studies interpret that An. stephensi (multiresistant) caused an upregulated expression of proteins and enzymes like cytochrome 450, short chain dehyrdogenase reductase, phosphodiesterase etc that may have an impact in insecticide resistance and xenobiotic detoxification. Our study elucidates a proteomic response of salivary glands differentially regulated proteins in response to insecticide resistance development which include structural, redox and regulatory enzymes of several pathways. These identified proteins

Indoor Residual Spraying in Combination with Insecticide-Treated Nets Compared to Insecticide-Treated Nets Alone for Protection against Malaria: A Cluster Randomised Trial in Tanzania

PubMed Central

West, Philippa A.; Protopopoff, Natacha; Wright, Alexandra; Kivaju, Zuhura; Tigererwa, Robinson; Mosha, Franklin W.; Kisinza, William; Rowland, Mark; Kleinschmidt, Immo

2014-01-01

Background Insecticide-treated nets (ITNs) and indoor residual spraying (IRS) of houses provide effective malaria transmission control. There is conflicting evidence about whether it is more beneficial to provide both interventions in combination. A cluster randomised controlled trial was conducted to investigate whether the combination provides added protection compared to ITNs alone. Methods and Findings In northwest Tanzania, 50 clusters (village areas) were randomly allocated to ITNs only or ITNs and IRS. Dwellings in the ITN+IRS arm were sprayed with two rounds of bendiocarb in 2012. Plasmodium falciparum prevalence rate (PfPR) in children 0.5–14 y old (primary outcome) and anaemia in children <5 y old (secondary outcome) were compared between study arms using three cross-sectional household surveys in 2012. Entomological inoculation rate (secondary outcome) was compared between study arms. IRS coverage was approximately 90%. ITN use ranged from 36% to 50%. In intention-to-treat analysis, mean PfPR was 13% in the ITN+IRS arm and 26% in the ITN only arm, odds ratio = 0.43 (95% CI 0.19–0.97, n = 13,146). The strongest effect was observed in the peak transmission season, 6 mo after the first IRS. Subgroup analysis showed that ITN users were additionally protected if their houses were sprayed. Mean monthly entomological inoculation rate was non-significantly lower in the ITN+IRS arm than in the ITN only arm, rate ratio = 0.17 (95% CI 0.03–1.08). Conclusions This is the first randomised trial to our knowledge that reports significant added protection from combining IRS and ITNs compared to ITNs alone. The effect is likely to be attributable to IRS providing added protection to ITN users as well as compensating for inadequate ITN use. Policy makers should consider deploying IRS in combination with ITNs to control transmission if local ITN strategies on their own are insufficiently effective. Given the uncertain generalisability of these findings

The central role of mosquito cytochrome P450 CYP6Zs in insecticide detoxification revealed by functional expression and structural modelling

PubMed Central

Chandor-Proust, Alexia; Bibby, Jaclyn; Régent-Kloeckner, Myriam; Roux, Jessica; Guittard-Crilat, Emilie; Poupardin, Rodolphe; Riaz, Muhammad Asam; Paine, Mark; Dauphin-Villemant, Chantal; Reynaud, Stéphane; David, Jean-Philippe

2013-01-01

The resistance of mosquitoes to chemical insecticides is threatening vector control programmes worldwide. Cytochrome P450 monooxygenases (CYPs) are known to play a major role in insecticide resistance, allowing resistant insects to metabolize insecticides at a higher rate. Among them, members of the mosquito CYP6Z subfamily, like Aedes aegypti CYP6Z8 and its Anopheles gambiae orthologue CYP6Z2, have been frequently associated with pyrethroid resistance. However, their role in the pyrethroid degradation pathway remains unclear. In the present study, we created a genetically modified yeast strain overexpressing Ae. aegypti cytochrome P450 reductase and CYP6Z8, thereby producing the first mosquito P450–CPR (NADPH-cytochrome P450-reductase) complex in a yeast recombinant system. The results of the present study show that: (i) CYP6Z8 metabolizes PBAlc (3-phenoxybenzoic alcohol) and PBAld (3-phenoxybenzaldehyde), common pyrethroid metabolites produced by carboxylesterases, producing PBA (3-phenoxybenzoic acid); (ii) CYP6Z8 transcription is induced by PBAlc, PBAld and PBA; (iii) An. gambiae CYP6Z2 metabolizes PBAlc and PBAld in the same way; (iv) PBA is the major metabolite produced in vivo and is excreted without further modification; and (v) in silico modelling of substrate–enzyme interactions supports a similar role of other mosquito CYP6Zs in pyrethroid degradation. By playing a pivotal role in the degradation of pyrethroid insecticides, mosquito CYP6Zs thus represent good targets for mosquito-resistance management strategies. PMID:23844938

Decline in frequency of the 2La chromosomal inversion in Anopheles gambiae (s.s.) in Western Kenya: correlation with increase in ownership of insecticide-treated bed nets.

PubMed

Matoke-Muhia, Damaris; Gimnig, John E; Kamau, Luna; Shililu, Josephat; Bayoh, M Nabie; Walker, Edward D

2016-06-10

The 2La chromosomal inversion, a genetic polymorphism in An. gambiae (sensu stricto) (s.s.), is associated with adaptation to microclimatic differences in humidity and desiccation resistance and mosquito behaviors. Ownership of insecticide-treated bed nets (ITNs) for malaria control has increased markedly in western Kenya in the last 20 years. An increase in the frequency of ITNs indoors could select against house entering or indoor resting of Anopheles mosquitoes. Thus, the frequency of the 2La inversion is postulated to change in An. gambiae (s.s.) with the increase of ITN ownership over time. Anopheles gambiae mosquitoes were sampled between 1994 and 2011 using pyrethrum knockdown, bednet traps and human landing catches (HLC) from Asembo and Seme, western Kenya. The 2La inversion was detected by a PCR assay with primers designed for proximal breakpoints of the 2La/a and 2L+(a)/+(a) chromosomal conformation. Mosquitoes were tested for malaria parasite infection by sporozoite ELISA. The frequency of the 2La chromosomal inversion declined from 100 % of all chromosomes in 1994 to 17 % in 2005 and remained low through 2011 (21 %). ITN ownership increased from 0 to > 90 % of houses in the study area during this interval. The decline in the frequency of the 2La chromosomal inversion was significantly, negatively correlated with year (r = -0.93) and with increase in ITN ownership (r = -0.96). The frequency of the homo- and heterokaryotypes departed significantly from Hardy-Weinberg equilibrium, suggesting that 2La/a karyotype was under selection, earlier in its favor and later, against it. Precipitation and maximum monthly temperature did not vary over time, therefore there was no trend in climate that could account for the decline. There was no significant difference in frequency of the 2La inversion in An. gambiae (s.s.) females sampled indoors or outdoors in HCL in 2011, nor was there an association between the 2La inversion and infection with Plasmodium

Entomological evaluation of PermaNet 2.0® and K-O Tab 1-2-3® treated nets in comparison to nets conventionally treated with deltamethrin, after repeated washing.

PubMed

Kayedi, Mohammad Hassan; Khamisabadi, Kiumars; Dehghani, Nader; Haghdoost, Ali Akbar

2015-06-01

The residual insecticidal power of two types of ITNs (PermaNet 2.0® (PN2) and K-O Tab 1-2-3® (KO 123)), compared to K-O Tab® (KO) treated nets, was assessed. The nets were tested unwashed, and after being washed, by hand 5, 15 and 21 times, respectively. After each wash, the nets were dried vertically on a line, in the shade. Two types of bioassays (mean median knock down times (MMKDT) and mortality 24 hours after a 3-minute exposure (%mortality)) were used, along with reared female Anopheles stephensi. The number of washes had a great impact on MMKDT and %mortality of all types of nets. This impact was greater for conventionally treated nets, indicating that PN2 and KO 123 nets are significantly more wash resistant than KO nets after 21 washes. There was no significant difference between PN2 and KO 123 with respect to %mortality 24 hours after a 3-minute exposure at 0, 15 and 21 washes. Similarly, the same results were obtained for MMKDT, and the differences between PN2 and KO 123 were not statistically significant. This study demonstrates that the efficacy of KO 123 nets is as beneficial as the efficacy of PN2 nets up to 21 washes.

The impact of insecticide-treated material to reduce flies among pork outlets in Kampala, Uganda.

PubMed

Heilmann, Martin; Roesel, Kristina; Grace, Delia; Bauer, Burkhard; Clausen, Peter-Henning

2017-06-01

Synanthropic flies have adapted to the mass of decaying organic matter near human settlements. As such, they feed and breed on food, faeces and other organic material and are known vectors for various diseases. Many of these diseases are associated with food, and foodborne diseases are of growing concern in developing countries where human population and food consumption increase. This pilot study aims at investigating the impact of a novel application of insecticide-treated material (ZeroFly®) to reduce flies among pork outlets in Kampala, Uganda. A cross-sectional survey randomly selected 60 of 179 pork outlets in Kampala. A controlled longitudinal trial followed in which 23 out of the 60 pork outlets were recruited for an intervention with insecticide-treated material. The pork outlets were randomly allocated to a group of 18 netted pork outlets (intervention) and five non-netted pork outlets (control). Monitoring took place over 15 weeks including 2 weeks as the baseline survey. The units were monitored for fly abundance using non-attractant sticky traps, which were placed within the pork outlet once per week for 48 consecutive hours. Medians of fly numbers before and after the intervention indicated a decrease of fly numbers of 48% (p = 0.002). Fly bioassays showed that the insecticidal activity of the netting remained active over the entire intervention period and led to a total paralysis of flies within at least 6 h after exposure. Insecticide-treated material provides a practical and sustainable solution in controlling flies and is therefore recommended as a complementary strategy for an integrated vector control and hygiene management.

Enhanced Protection against Malaria by Indoor Residual Spraying in Addition to Insecticide Treated Nets: Is It Dependent on Transmission Intensity or Net Usage?

PubMed Central

West, Philippa A.; Protopopoff, Natacha; Wright, Alexandra; Kivaju, Zuhura; Tigererwa, Robinson; Mosha, Franklin W.; Kisinza, William; Rowland, Mark; Kleinschmidt, Immo

2015-01-01

Background Insecticide treated nets (ITNs) and indoor residual spraying (IRS) are effective vector control tools that protect against malaria. There is conflicting evidence regarding whether using ITNs and IRS in combination provides additional benefit over using either of these methods alone. This study investigated factors that may modify the effect of the combined use of IRS and ITNs compared to using ITNs alone on malaria infection prevalence. Methods Secondary analysis was carried out on data from a cluster randomised trial in north-west Tanzania. 50 clusters received ITNs from a universal coverage campaign; of these 25 were randomly allocated to additionally receive two rounds of IRS in 2012. In cross-sectional household surveys children 0.5–14 years old were tested for Plasmodium falciparum infections (PfPR) two, six and ten months after the first IRS round. Results IRS protected those sleeping under nets (OR = 0.38, 95%CI 0.26–0.57) and those who did not (OR = 0.43, 95%CI 0.29–0.63). The protective effect of IRS was not modified by community level ITN use (ITN use<50%, OR = 0.39, 95%CI 0.26–0.59; ITN use> = 50%, OR = 0.46, 95%CI 0.28–0.74). The additional protection from IRS was similar in low (<10% PfPR, OR = 0.38, 95%CI 0.19–0.75) and high transmission areas (≥10% PfPR, OR = 0.34, 95%CI 0.18–0.67). ITN use was protective at the individual-level regardless of whether the village had been sprayed (OR = 0.83, 95%CI 0.70–0.98). Living in a sprayed village was protective regardless of whether the individual slept under an ITN last night (OR = 0.41, 95%CI 0.29–0.58). Interpretation Implementing IRS in addition to ITNs was beneficial for individuals from villages with a wide range of transmission intensities and net utilisation levels. Net users received additional protection from IRS. ITNs were providing some individual protection, even in this area with high levels of pyrethroid insecticide resistance. These results demonstrate that there

An exploratory qualitative study on perceptions about mosquito bed nets in the Niger Delta: what are the barriers to sustained use?

PubMed Central

Galvin, Kathleen T; Petford, Nick; Ajose, Frances; Davies, Dai

2011-01-01

Background: The effectiveness of malaria control programs is determined by an array of complex factors, including the acceptability and sustained use of preventative measures such as the bed net. A small-scale exploratory study was conducted in several locations in the Niger Delta region, Nigeria, to discover barriers against the use of bed nets, in the context of a current drive to scale up net use in Nigeria. Methods: A qualitative approach with a convenience sample was used. One to one interviews with mostly male adult volunteers were undertaken which explored typical living and sleeping arrangements, and perceptions about and barriers against the use of the mosquito prevention bed net. Results: Several key issues emerged from the qualitative data. Bed nets were not reported as widely used in this small sample. The reasons reported for lack of use included issues of convenience, especially net set up and dismantling; potential hazard and safety concerns; issues related to typical family composition and nature of accommodation; humid weather conditions; and perceptions of cost and effectiveness. Most barriers to net use concerned issues about everyday practical living and sleeping arrangements and perceptions about comfort. Interviewees identified were aware of malaria infection risks, but several also indicated certain beliefs that were barriers to net use. Conclusions: Successful control of malaria and scale up of insecticide-treated net coverage relies on community perceptions and practice. This small study has illuminated a number of important everyday life issues, which remain barriers to sustained net use, and has clarified further questions to be considered in net design and in future research studies. The study highlights the need for further research on the human concerns that contribute to sustained use of nets or, conversely, present significant barriers to their use. PMID:21544249

Insecticide-treated clothes for the control of vector-borne diseases: a review on effectiveness and safety.

PubMed

Banks, S D; Murray, N; Wilder-Smith, A; Logan, J G

2014-08-01

Insecticide-treated clothing has been used for many years by the military and in recreational activities as personal protection against bites from a variety of arthropods including ticks, chigger mites, sandflies and mosquitoes. Permethrin is the most commonly used active ingredient, but others, including bifenthrin, deltamethrin, cyfluthrin, DEET (N,N-diethyl-3-methylbenz-amide) and KBR3023, have also been trialled. Treatment is usually carried out by home or factory dipping. However, new microencapsulation technologies which may prolong the activity of insecticides on clothing are now available and may help to overcome the inevitable reduction in efficacy over time that occurs as a result of washing, ultraviolet light exposure, and the normal wear and tear of the fabric. The aim of this article is to review the evidence base for the use of insecticide-treated clothing for protection against bites from arthropods and its effect on arthropod-borne pathogen transmission. Although some studies do demonstrate protection against pathogen transmission, there are surprisingly few, and the level of protection provided varies according to the disease and the type of study conducted. For example, insecticide-treated clothing has been reported to give between 0% and 75% protection against malaria and between 0% and 79% protection against leishmaniasis. Studies vary in the type of treatment used, the age group of participants, the geographical location of the study, and the pathogen transmission potential. This makes it difficult to compare and assess intervention trials. Overall, there is substantial evidence that insecticide-treated clothing can provide protection against arthropod bites. Bite protection evidence suggests that insecticide-treated clothing may be useful in the prevention of pathogen transmission, but further investigations are required to accurately demonstrate transmission reduction. © 2014 The Royal Entomological Society.

Assessment on the ownership and use of mosquito nets in Mozambique.

PubMed

Arroz, Jorge Alexandre Harrison; Chirrute, Francisco; Mendis, Chandana; Chande, Marta Honesta; Kollhoff, Veronique

2016-12-22

To assess the ownership and use of mosquito nets in 2014, in Mozambique. This observational and cross-sectional study assessed, in February and March 2015, 69 districts (nine of 11 provinces of Mozambique) that have benefited from the mass distribution of mosquito nets. The Lot Quality Assurance Sampling methodology was used. Each locality was denominated supervision area. The Lot Quality Assurance Sampling opts for a minimum of 19 households (in this case, we decided for a minimum of 100 households per district) from each supervision area to assess an indicator (in this case, two indicators were assessed: ownership and use of mosquito nets). Two questions guided the research: a) received a mosquito net; b) used a mosquito net the night before. A total of 6,725 households were assessed. Eighty three percent of them had received mosquito nets in the campaign. Of the 6,232 respondents, 82.0% said they used mosquito nets the night before. The districts of the provinces with low coverage of ownership and use were Tete (69.5% and 60.0%, respectively), Zambezia (79.0% and 60.0%, respectively), and Gaza (81.6% and 70.7%, respectively). The largest coverage of ownership and use were observed in the districts of Nampula (96.7% and 93.8%, respectively) and Niassa (86.0% and 85.4% respectively). In the districts assessed, the progression of ownership and use of mosquito nets is satisfactory. Nampula and Niassa are the only provinces where ownership and use are at desired levels. Avaliar a posse e o uso das redes mosquiteiras no ano de 2014 em Moçambique. Este estudo observacional transversal avaliou, em fevereiro e março de 2015, 68 distritos (nove das 11 províncias de Moçambique) que se beneficiaram da distribuição de redes em massa. Usou-se a metodologia Lot Quality Assurance Sampling. Cada localidade foi designada de área de supervisão. O Lot Quality Assurance Sampling opta por um mínimo de 19 agregados familiares (neste caso decidiu-se um mínimo de 100 agregados

Multiple Cytochrome P450 genes: their constitutive overexpression and permethrin induction in insecticide resistant mosquitoes, Culex quinquefasciatus.

PubMed

Liu, Nannan; Li, Ting; Reid, William R; Yang, Ting; Zhang, Lee

2011-01-01

Four cytochrome P450 cDNAs, CYP6AA7, CYP9J40, CYP9J34, and CYP9M10, were isolated from mosquitoes, Culex quinquefasciatus. The P450 gene expression and induction by permethrin were compared for three different mosquito populations bearing different resistance phenotypes, ranging from susceptible (S-Lab), through intermediate (HAmCq(G0), the field parental population) to highly resistant (HAmCq(G8), the 8(th) generation of permethrin selected offspring of HAmCq(G0)). A strong correlation was found for P450 gene expression with the levels of resistance and following permethrin selection at the larval stage of mosquitoes, with the highest expression levels identified in HAmCq(G8), suggesting the importance of CYP6AA7, CYP9J40, CYP9J34, and CYP9M10 in the permethrin resistance of larva mosquitoes. Only CYP6AA7 showed a significant overexpression in HAmCq(G8) adult mosquitoes. Other P450 genes had similar expression levels among the mosquito populations tested, suggesting different P450 genes may be involved in the response to insecticide pressure in different developmental stages. The expression of CYP6AA7, CYP9J34, and CYP9M10 was further induced by permethrin in resistant mosquitoes. Taken together, these results indicate that multiple P450 genes are up-regulated in insecticide resistant mosquitoes through both constitutive overexpression and induction mechanisms, thus increasing the overall expression levels of P450 genes.

Strategies for delivering insecticide-treated nets at scale for malaria control: a systematic review

PubMed Central

Paintain, Lucy Smith; Mangham, Lindsay; Car, Josip; Schellenberg, Joanna Armstrong

2012-01-01

Abstract Objective To synthesize findings from recent studies of strategies to deliver insecticide-treated nets (ITNs) at scale in malaria-endemic areas. Methods Databases were searched for studies published between January 2000 and December 2010 in which: subjects resided in areas with endemicity for Plasmodium falciparum and Plasmodium vivax malaria; ITN delivery at scale was evaluated; ITN ownership among households, receipt by pregnant women and/or use among children aged < 5 years was evaluated; and the study design was an individual or cluster-randomized controlled design, nonrandomized, quasi-experimental, before-and-after, interrupted time series or cross-sectional without temporal or geographical controls. Papers describing qualitative studies, case studies, process evaluations and cost-effectiveness studies linked to an eligible paper were also included. Study quality was assessed using the Cochrane risk of bias checklist and GRADE criteria. Important influences on scaling up were identified and assessed across delivery strategies. Findings A total of 32 papers describing 20 African studies were reviewed. Many delivery strategies involved health sectors and retail outlets (partial subsidy), antenatal care clinics (full subsidy) and campaigns (full subsidy). Strategies achieving high ownership among households and use among children < 5 delivered ITNs free through campaigns. Costs were largely comparable across strategies; ITNs were the main cost. Cost-effectiveness estimates were most sensitive to the assumed net lifespan and leakage. Common barriers to delivery included cost, stock-outs and poor logistics. Common facilitators were staff training and supervision, cooperation across departments or ministries and stakeholder involvement. Conclusion There is a broad taxonomy of strategies for delivering ITNs at scale. PMID:22984312

Caretakers' understanding of malaria, use of insecticide treated net and care seeking-behavior for febrile illness of their children in Ethiopia.

PubMed

Birhanu, Zewdie; Yihdego, Yemane Ye-Ebiyo; Yewhalaw, Delenasaw

2017-09-18

Local understandings of malaria and use of preventive measures-are critical factors in sustained control of malaria. This study assessed caretakers' knowledge on malaria, use of Long Lasting Insecticide Treated Nets (LLINs) and care-seeking behavior for their children's illness in different malaria transmission settings of Ethiopia. Data were collected from 709 caretakers of children of 2-9 years of age during in 2016. A standard questionnaire was used to assess caretakers' perceptions of malaria, use of LLIN and care seeking behavior for febrile illness of children aged 2-9 years. The caretakers recognized malaria mostly by chills (70.4%, 499/709), fever (45.7%, 324/709) and headache (39.8%, 282/709). Overall, only 66.4% (471) of the caretakers knew that mosquito bite caused malaria and that it was quite heterogeneous by localities (ranging from 26.1% to 89.4%) and altitude (p < 0.05). Majority, 72.2% (512), of the caretakers knew that sleeping under LLIN could prevent malaria. Overall knowledge on malaria (mean = 51.2%) was very low with significant variations by localities, altitude and levels of malaria transmission, being low in high altitude and low in transmission areas (p < 0.05). Four hundred ninety-one (69.3%, 491/709) of the children slept under LLIN in the previous night. Of malaria related knowledge items, only knowledge of LLIN was associated with net use; non-use of LLN was higher among caretakers who did not know the role of LLIN (AOR = 0.47, 95%CI: 0.28-0.77, p = 0.003). Of course, attributing causation of malaria to stagnant water discouraged use of net (p = 0.021). Of febrile children (n = 122), only 50 (41.0%) sought care with only 17 (34.0%) seeking the care promptly. There was no significant link between knowledge of malaria and care seeking behavior (p > 0.05). However, knowledge of malaria had some level of influence on treatment source preference where caretakers with greater knowledge preferred pharmacy as

Economic aspects of the use of impregnated mosquito nets for malaria control.

PubMed Central

Brinkmann, U.; Brinkmann, A.

1995-01-01

The use of pyrethroids to impregnate mosquito nets has had a good impact on the incidence of morbidity and mortality from malaria. These nets are therefore likely to be used on a large scale as an important strategy of malaria control in the future. Published information on the cost and effectiveness of mosquito nets is presented and analysed. In two examples, from Malawi and Cameroon, the per household expenditure to purchase and use impregnated mosquito nets compares favourably with the costs of malaria. Thus, we expect that the economic losses from malaria would be reduced by 37.3% over a 3-year period in Malawi. Even if the impact of malaria on productivity is not taken into account, the introduction of nets will result in gains, as shown in Cameroon; savings of 9.3% and 11.2% in two places resulted as a consequence of a diminished need for case treatment. The role of government programmes in the promotion of bednets is indirect and concerned mainly with facilitation and the dissemination of information. Much depends on the capability of the private sector and the willingness of the target population to buy the nets for a programme to be effective. Specific studies by health economists on this subject are lacking. PMID:8846491

The comparative toxicity of phosphoramidothionates and phosphoramidates to susceptible and insecticide-resistant houseflies and mosquitos*

PubMed Central

March, R. B.; Georghiou, G. P.; Metcalf, R. L.; Printy, G. E.

1964-01-01

Studies of the comparative toxicity of a number of homologous X-chlorophenyl phosphoramidothionates and phosphoramidates and related analogues to susceptible and insecticide-resistant houseflies (Musca domestica L.) and mosquitos (Culex pipiens quinquefasciatus Say and Anopheles albimanus Wied.) have shown that the 2,4,5-trichlorophenyl series is the most active and the 4-chlorophenyl series the least active. Toxicity decreases in general with increasing chain length of the alkoxy and alkylamido moieties, maximum toxicity residing in methoxy, ethoxy, amido, methylamido, and ethylamido homologues. Toxicity is greatest to the susceptible strain but the alkylamido and X-chlorophenyl structures confer toxicological advantages from the standpoint of relative effectiveness against organophosphorus-resistance and organophosphorus vigour-tolerance. Many of the phosphoramidates are less toxic than their phosphoramidothionate analogues, probably due to less favourable physical properties. Certain of these compounds show promise against both susceptible and insecticide-resistant housefly adults and it is suggested that they be further evaluated in broad-spectrum field trials. Although some show promise as mosquito larvicides, in general the introduction of an alkyl-amido group markedly decreases residual toxicity from a filter-paper residue to mosquito adults in comparison with the corresponding dialkoxy analogues. PMID:14122443

Costing the distribution of insecticide-treated nets: a review of cost and cost-effectiveness studies to provide guidance on standardization of costing methodology

PubMed Central

Kolaczinski, Jan; Hanson, Kara

2006-01-01

Background Insecticide-treated nets (ITNs) are an effective and cost-effective means of malaria control. Scaling-up coverage of ITNs is challenging. It requires substantial resources and there are a number of strategies to choose from. Information on the cost of different strategies is still scarce. To guide the choice of a delivery strategy (or combination of strategies), reliable and standardized cost information for the different options is required. Methods The electronic online database PubMed was used for a systematic search of the published English literature on costing and economic evaluations of ITN distribution programmes. The keywords used were: net, bednet, insecticide, treated, ITN, cost, effectiveness, economic and evaluation. Identified papers were analysed to determine and evaluate the costing methods used. Methods were judged against existing standards of cost analysis to arrive at proposed standards for undertaking and presenting cost analyses. Results Cost estimates were often not readily comparable or could not be adjusted to a different context. This resulted from the wide range of methods applied and measures of output chosen. Most common shortcomings were the omission of certain costs and failure to adjust financial costs to generate economic costs. Generalisability was hampered by authors not reporting quantities and prices of resources separately and not examining the sensitivity of their results to variations in underlying assumptions. Conclusion The observed shortcomings have arisen despite the abundance of literature and guidelines on costing of health care interventions. This paper provides ITN specific recommendations in the hope that these will help to standardize future cost estimates. PMID:16681856

Costing the distribution of insecticide-treated nets: a review of cost and cost-effectiveness studies to provide guidance on standardization of costing methodology.

PubMed

Kolaczinski, Jan; Hanson, Kara

2006-05-08

Insecticide-treated nets (ITNs) are an effective and cost-effective means of malaria control. Scaling-up coverage of ITNs is challenging. It requires substantial resources and there are a number of strategies to choose from. Information on the cost of different strategies is still scarce. To guide the choice of a delivery strategy (or combination of strategies), reliable and standardized cost information for the different options is required. The electronic online database PubMed was used for a systematic search of the published English literature on costing and economic evaluations of ITN distribution programmes. The keywords used were: net, bednet, insecticide, treated, ITN, cost, effectiveness, economic and evaluation. Identified papers were analysed to determine and evaluate the costing methods used. Methods were judged against existing standards of cost analysis to arrive at proposed standards for undertaking and presenting cost analyses. Cost estimates were often not readily comparable or could not be adjusted to a different context. This resulted from the wide range of methods applied and measures of output chosen. Most common shortcomings were the omission of certain costs and failure to adjust financial costs to generate economic costs. Generalisability was hampered by authors not reporting quantities and prices of resources separately and not examining the sensitivity of their results to variations in underlying assumptions. The observed shortcomings have arisen despite the abundance of literature and guidelines on costing of health care interventions. This paper provides ITN specific recommendations in the hope that these will help to standardize future cost estimates.

Dopamine receptor antagonists as new mode-of-action insecticide leads for control of Aedes and Culex mosquito vectors.

PubMed

Nuss, Andrew B; Ejendal, Karin F K; Doyle, Trevor B; Meyer, Jason M; Lang, Emma G; Watts, Val J; Hill, Catherine A

2015-03-01

New mode-of-action insecticides are sought to provide continued control of pesticide resistant arthropod vectors of neglected tropical diseases (NTDs). We previously identified antagonists of the AaDOP2 D1-like dopamine receptor (DAR) from the yellow fever mosquito, Aedes aegypti, with toxicity to Ae. aegypti larvae as leads for novel insecticides. To extend DAR-based insecticide discovery, we evaluated the molecular and pharmacological characteristics of an orthologous DAR target, CqDOP2, from Culex quinquefasciatus, the vector of lymphatic filariasis and West Nile virus. CqDOP2 has 94.7% amino acid identity to AaDOP2 and 28.3% identity to the human D1-like DAR, hD1. CqDOP2 and AaDOP2 exhibited similar pharmacological responses to biogenic amines and DAR antagonists in cell-based assays. The antagonists amitriptyline, amperozide, asenapine, chlorpromazine and doxepin were between 35 to 227-fold more selective at inhibiting the response of CqDOP2 and AaDOP2 in comparison to hD1. Antagonists were toxic to both C. quinquefasciatus and Ae. aegypti larvae, with LC50 values ranging from 41 to 208 μM 72 h post-exposure. Orthologous DOP2 receptors identified from the African malaria mosquito, Anopheles gambiae, the sand fly, Phlebotomus papatasi and the tsetse fly, Glossina morsitans, had high sequence similarity to CqDOP2 and AaDOP2. DAR antagonists represent a putative new insecticide class with activity against C. quinquefasciatus and Ae. aegypti, the two most important mosquito vectors of NTDs. There has been limited change in the sequence and pharmacological properties of the DOP2 DARs of these species since divergence of the tribes Culicini and Aedini. We identified antagonists selective for mosquito versus human DARs and observed a correlation between DAR pharmacology and the in vivo larval toxicity of antagonists. These data demonstrate that sequence similarity can be predictive of target potential. On this basis, we propose expanded insecticide discovery around

Assessment of coverage of preventive treatment and insecticide-treated mosquito nets in pregnant women attending antenatal care services in 11 districts in Mozambique in 2011: the critical role of supply chain.

PubMed

Salomão, Cristolde; Sacarlal, Jahit; Gudo, Eduardo Samo

2017-05-25

Malaria during pregnancy is associated with poor maternal and pregnancy outcome and the World Health Organization recommends the administration of intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine (SP) and distribution of insecticide-treated mosquito nets (ITNs) to all pregnant women attending antenatal care (ANC) services. This study was conducted with the aim to assess the uptake of IPTp and ITNs in pregnant women attending ANC services and correlate with ANC attendance and frequency of stock-outs in 22 health facilities Mozambique. A cross-sectional study was conducted between July and December 2011 in 22 health units in 11 districts situated in 11 provinces in Mozambique. Two health facilities were selected per district (one urban and one rural). Data were collected by reviewing logbooks of antenatal consultations as well as from monthly district reports. During the period under investigation, a total of 23,524 pregnant women attended their 1st antenatal care visits, of which 12,775 (54.3%) and 7581 (32.2%) received one and two doses of IPTp, respectively. In regard to ITNs, a total of 16,436 (69.9%) pregnant women received ITNs. Uptake of IPTp and ITNs by pregnant women at ANC services was higher in southern Mozambique and lower in districts situated in the northern part of the country. Stock-outs of SP and ITNs were reported in 50.0% (11/22) and 54.5% (12/22) of the health facilities, respectively. Coverage of IPTp and ITN in health facilities with stock-outs of SP and ITNs was much lower as compared to health facilities with no stock-outs. Altogether, data from this study shows that coverage of the 2nd dose of IPTp, as well as ITNs, was low in pregnant women attending ANC services in Mozambique. In addition, this data also shows that stock-outs of SP and ITNs were frequent and led to lower coverage of IPTp and ITN, representing a serious barrier for the accomplishment of targets. In conclusion, this study recommends that

Lay perceptions of kala-azar, mosquitoes and bed nets in Bihar, India.

PubMed

Mishra, Rabindra N; Singh, S P; Vanlerberghe, Veerle; Sundar, Shyam; Boelaert, Marleen; Lefèvre, Pierre

2010-07-01

To describe the lay perception of kala-azar (KA) in an endemic area of Muzaffarpur District, Bihar, India: local names, symptoms, affected persons, perceived severity and modes of transmission, as well as perceived mosquito nuisance, modes of protection and use of bed nets. We held 16 focus group discussions (FGD) in eight remote villages with altogether 157 participants in March 2008. Separate FGDs were held according to gender, socio-economic status (SES) and with key informants. Kala-azar is most commonly named pilahi. Poor people were said to be the most affected. Knowledge about symptoms was satisfactory. Fever and prolonged fever were the most stated symptoms. KA was perceived as a life-threatening disease with a heavy economic burden. Mosquito bites were perceived as the main mode of transmission but in lower socio-economic groups, non-vector-related explanations were also provided. The main modes of protection from mosquitoes mentioned were the use of fumes and bed nets. Season was the strongest factor influencing the use of bed nets and non-affordability for not owning them. Although the sand fly is not recognised as the vector, the relatively good awareness of disease transmission by mosquitoes and the nuisance caused by their high density might be an entry point for adopting preventive measures to protect from mosquito bite and thereby indirectly preventing from KA. Educational campaigns targeted to the poorer segments of society are needed to enhance knowledge about KA, its mode of transmission, risks of getting infected and to increase bed net use.

Mass mosquito trapping for malaria control in western Kenya: study protocol for a stepped wedge cluster-randomised trial.

PubMed

Hiscox, Alexandra; Homan, Tobias; Mweresa, Collins K; Maire, Nicolas; Di Pasquale, Aurelio; Masiga, Daniel; Oria, Prisca A; Alaii, Jane; Leeuwis, Cees; Mukabana, Wolfgang R; Takken, Willem; Smith, Thomas A

2016-07-26

Increasing levels of insecticide resistance as well as outdoor, residual transmission of malaria threaten the efficacy of existing vector control tools used against malaria mosquitoes. The development of odour-baited mosquito traps has led to the possibility of controlling malaria through mass trapping of malaria vectors. Through daily removal trapping against a background of continued bed net use it is anticipated that vector populations could be suppressed to a level where continued transmission of malaria will no longer be possible. A stepped wedge cluster-randomised trial design was used for the implementation of mass mosquito trapping on Rusinga Island, western Kenya (the SolarMal project). Over the course of 2 years (2013-2015) all households on the island were provided with a solar-powered mosquito trapping system. A continuous health and demographic surveillance system combined with parasitological surveys three times a year, successive rounds of mosquito monitoring and regular sociological studies allowed measurement of intervention outcomes before, during and at completion of the rollout of traps. Data collection continued after achieving mass coverage with traps in order to estimate the longer term effectiveness of this novel intervention. Solar energy was exploited to provide electric light and mobile phone charging for each household, and the impacts of these immediate tangible benefits upon acceptability of and adherence to the use of the intervention are being measured. This study will be the first to evaluate whether the principle of solar-powered mass mosquito trapping could be an effective tool for elimination of malaria. If proven to be effective, this novel approach to malaria control would be a valuable addition to the existing strategies of long-lasting insecticide-treated nets and case management. Sociological studies provide a knowledge base for understanding the usage of this novel tool. Trialregister.nl: NTR3496 - SolarMal. Registered on

Comparison of Insecticide-Treated Nets and Indoor Residual Spraying to Control the Vector of Visceral Leishmaniasis in Mymensingh District, Bangladesh

PubMed Central

Chowdhury, Rajib; Dotson, Ellen; Blackstock, Anna J.; McClintock, Shannon; Maheswary, Narayan P.; Faria, Shyla; Islam, Saiful; Akter, Tangin; Kroeger, Axel; Akhter, Shireen; Bern, Caryn

2011-01-01

Integrated vector management is a pillar of the South Asian visceral leishmaniasis (VL) elimination program, but the best approach remains a matter of debate. Sand fly seasonality was determined in 40 houses sampled monthly. The impact of interventions on Phlebotomus argentipes density was tested from 2006–2007 in a cluster-randomized trial with four arms: indoor residual spraying (IRS), insecticide-treated nets (ITNs), environmental management (EVM), and no intervention. Phlebotomus argentipes density peaked in March with the highest proportion of gravid females in May. The EVM (mud plastering of wall and floor cracks) showed no impact. The IRS and ITNs were associated with a 70–80% decrease in male and female P. argentipes density up to 5 months post intervention. Vector density rebounded by 11 months post-IRS, whereas ITN-treated households continued to show significantly lower density compared with households without intervention. Our data suggest that both IRS and ITNs may help to improve VL control in Bangladesh. PMID:21540372

Insecticidal and repellent activity of Hiptage benghalensis L. Kruz (Malpighiaceae) against mosquito vectors.

PubMed

Lalrotluanga; Ngente, Lalchawimawii; Nachimuthu, Senthil Kumar; Guruswami, Gurusubramanian

2012-09-01

Plant-based insecticides for vector control are urgently needed for Anopheles barbirostris, Culex quinquefasciatus, and Aedes albopictus which are the primary vectors of malaria, lymphatic filariasis, and dengue, respectively, in India and other South East Asian countries. In the present study, larvicidal, adulticidal, and repellent activities of acetone root bark extract of Hiptage benghalensis were tested against the larvae and adults of the three mosquito vectors. The acetone root bark extracts of H. benghalensis was more effective as larvicides with low LC(50) (11.15-16.78 ppm) and LT50 (1.25-4.84 h at 200 and 400 ppm) values. Results of log probit analysis (at 95 % confidence level) and regression analysis of crude acetone root bark extract of H. benghalensis revealed that lethal concentration (LC(50)) values gradually decreased with the exposure periods; lethal time (LT(50)) decreased with the concentration, and the mortality is positively correlated with the concentration. The order of susceptibility of the three mosquito species was as follows: A. albopictus > A. barbirostris > C. quinquefascitus. Biochemical changes were also evidenced in third instar larvae of three mosquito species following a sublethal exposure for 24 h. The level of sugar, glycogen, lipids, and proteins was significantly (P < 0.05) reduced in larvae treated with H. benghalensis. The acetone root bark extracts of H. benghalensis is less toxic to adults and repelled laboratory-reared female A. barbirostris, A. albopictus, and C. quinquefascitus with the short median protection times of 57.66-135, 72.41-134.16, and 47.66-93 min, respectively. The present investigation proves it as a potent larvicide against A. albopictus, A. barbirostris, and C. quinquefascitus, which can be recommended to control these mosquito species on its breeding site. However, further investigations are needed to confirm the lethal effects of H. benghalensis in field conditions and its impact on the nontarget

[Preliminary evaluation of the insecticide susceptibility in Anopheles gambiae and Culex quinquefasciatus from Lobito (Angola), using WHO standard assay].

PubMed

Toto, J C; Besnard, P; Le Mire, J; Almeida, D S I; Dos Santos, M A; Fortes, F; Foumane, V; Simard, F; Awono-Ambene, H P; Carnevale, P

2011-10-01

Field collections of the most common urban mosquito vectors Anopheles gambiae and Culex quinquefasciatus were carried out in June 2003, March 2004 and November 2005 to gather preliminary data on the insecticide susceptibility in mosquitoes from Lobito (Angola) using the WHO standard bioassays. Bioassays were performed on F0 adults emerging from the field larval collections and on unfed adults from landing catches on volunteers. Batches of mosquitoes from three selected locations (Alto Liro, San Jao and Bela Vista) were exposed for 1 hour to several insecticides such as DDT 4%, carbosulfan 0.4%, permethrin 1%, deltamethrin 0.05% and cyfluthrin 0.15%, in order to estimate the immediate knockdown times (kdT50 and kdT95) and the mortality rate after exposure. The results revealed that mosquito susceptibility to insecticides varied depending on the insecticide, the site and the period of collection. The main local malaria vector A. gambiae (both M and S forms) was basically resistant to DDT and susceptible to all pyrethoids, regardless of the period and the site of collections. The overall mortality rate due to DDT was 73% in Alto Liro, 89% in San Jao and varied depending on the period in Bela Vista between 95% in March 2004 and 100% in November 2005. The mortality due to pyrethoids was 100% at all locations, with the kdT50 and KdT95 times ranging between 9 and 16 minutes and between 18 and 29 minutes, respectively. Concerning the C. quinquefasciatus, populations from Yard and Caponte were resistant to all insecticides tested; the mortality rate was 40% with deltamethrin and 70% with permethrin, while no lethal effect was observed with DDT or carbosulfan. In conclusion, despite its probable high resistance to DDT, the main local malaria vector A. gambiae remained fully susceptible to pyrethroids. This could forecast a good biological efficacy of the scheduled vector control interventions in Angola, based on a large-scale distribution of long-lasting, insecticide-treated

Repellent action of neem cream against mosquitoes.

PubMed

Dua, V K; Nagpal, B N; Sharma, V P

1995-06-01

Neem cream was used as mosquito repellent to provide protection against Aedes albopictus, Ae. aegypti, Culex quinquefasciatus, Anopheles culicifacies and An. subpictus mosquitoes. The application of neem cream on exposed body parts @2.0 gm/person showed 78 (range 65-95), 89 (range 66-100) and 94.4 (range 66-100) per cent protection against Aedes, Culex and Anopheles mosquitoes respectively. Significant difference was observed between neem cream treated and untreated group of population for Aedes mosquitoes (p < 0.001). Application of neem cream was found to be a safe and suitable alternative to insecticide impregnated coils for personal protection against mosquitoes and one application was 68% effective for four hours.

Multicentre studies of insecticide-treated durable wall lining in Africa and South-East Asia: entomological efficacy and household acceptability during one year of field use

PubMed Central

2012-01-01

Background Indoor residual spraying (IRS) is a primary method of malaria vector control, but its potential impact is constrained by several inherent limitations: spraying must be repeated when insecticide residues decay, householders can tire of the annual imposition and campaign costs are recurrent. Durable lining (DL) can be considered an advanced form of long-lasting IRS where insecticide is gradually released from an aesthetically attractive wall lining material to provide vector control for several years. A multicentre trial was carried out in Equatorial Guinea, Ghana, Mali, South Africa and Vietnam to assess the feasibility, durability, bioefficacy and household acceptability of DL, compared to conventional IRS or insecticide-treated curtains (LLITCs), in a variety of operational settings. Methods This study was conducted in 220 households in traditional rural villages over 12-15 months. In all sites, rolls of DL were cut to fit house dimensions and fixed to interior wall surfaces (usually with nails and caps) by trained teams. Acceptability was assessed using a standardized questionnaire covering such topics as installation, exposure reactions, entomology, indoor environment, aesthetics and durability. Bioefficacy of interventions was evaluated using WHO cone bioassay tests at regular intervals throughout the year. Results The deltamethrin DL demonstrated little to no decline in bioefficacy over 12-15 months, supported by minimal loss of insecticide content. By contrast, IRS displayed a significant decrease in bioactivity by 6 months and full loss after 12 months. The majority of participants in DL households perceived reductions in mosquito density (93%) and biting (82%), but no changes in indoor temperature (83%). Among those households that wanted to retain the DL, 73% cited protective reasons, 20% expressed a desire to keep theirs for decoration and 7% valued both qualities equally. In Equatorial Guinea, when offered a choice of vector control product at

Deltamethrin-mediated survival, behavior, and oenocyte morphology of insecticide-susceptible and resistant yellow fever mosquitos (Aedes aegypti).

PubMed

Marriel, Nadja Biondine; Tomé, Hudson Vaner Ventura; Guedes, Raul Carvalho Narciso; Martins, Gustavo Ferreira

2016-06-01

Insecticide use is the prevailing control tactic for the mosquito Aedes aegypti, a vector of several human viruses, which leads to ever-increasing problems of insecticide resistance in populations of this insect pest species. The underlying mechanisms of insecticide resistance may be linked to the metabolism of insecticides by various cells, including oenocytes. Oenocytes are ectodermal cells responsible for lipid metabolism and detoxification. The goal of this study was to evaluate the sublethal effects of deltamethrin on survival, behavior, and oenocyte structure in the immature mosquitoes of insecticide-susceptible and resistant strains of A. aegypti. Fourth instar larvae (L4) of both strains were exposed to different concentrations of deltamethrin (i.e., 0.001, 0.003, 0.005, and 0.007 ppm). After exposure, L4 were subjected to behavioral bioassays. Insecticide effects on cell integrity after deltamethrin exposure (at 0.003 or 0.005 ppm) were assessed by processing pupal oenocytes for transmission electron microscopy or TUNEL reaction. The insecticide resistant L4 survived all the tested concentrations, whereas the 0.007-ppm deltamethrin concentration had lethal effects on susceptible L4. Susceptible L4 were lethargic and exhibited less swimming activity than unexposed larvae, whereas the resistant L4 were hyperexcited following exposure to 0.005 ppm deltamethrin. No sublethal effects and no significant cell death were observed in the oenocytes of either susceptible or resistant insects exposed to deltamethrin. The present study illustrated the different responses of susceptible and resistant strains of A. aegypti following exposure to sublethal concentration of deltamethrin, and demonstrated how the behavior of the immature stage of the two strains varied, as well as oenocyte structure following insecticide exposure. Copyright © 2016 Elsevier B.V. All rights reserved.

Insecticide-impregnated netting as a potential tool for long-lasting control of the leishmaniasis vector Lutzomyia longipalpis in animal shelters

PubMed Central

2013-01-01

with insecticide impregnated netting material may provide a longer-lasting solution for killing sand flies than residual spraying. Field trials are needed to identify the feasibility of treating surfaces with netting or similar impregnated materials as part of a control program. In targeting L. longipalpis, the greatest benefits may be seen in treating animal sheds with netting, where these sand flies aggregate in large numbers, and which can be difficult to treat repeatedly by conventional spraying. PMID:23642213

Synergistic action of octopamine receptor agonists on the activity of selected novel insecticides for control of dengue vector Aedes aegypti (Diptera: Culicidae) mosquito.

PubMed

Ahmed, Mohamed Ahmed Ibrahim; Vogel, Christoph Franz Adam

2015-05-01

Studying insecticide resistance in mosquitoes has attracted the attention of many scientists to elucidate the pathways of resistance development and to design novel strategies in order to prevent or minimize the spread and evolution of resistance. Here, we tested the synergistic action of piperonyl butoxide (PBO) and two octopamine receptor (OR) agonists, amitraz (AMZ) and chlordimeform (CDM) on selected novel insecticides to increase their lethal action on the fourth instar larvae of Aedes aegypti L. However, chlorfenapyr was the most toxic insecticide (LC50 = 193, 102, and 48 ng/ml, after 24, 48, and 72 h exposure, respectively) tested. Further, PBO synergized all insecticides and the most toxic combinatorial insecticide was nitenpyram even after 48 and 72 h exposure. In addition, OR agonists significantly synergized most of the selected insecticides especially after 48 and 72 h exposure. The results imply that the synergistic effects of amitraz are a promising approach in increasing the potency of certain insecticides in controlling the dengue vector Ae. aegypti mosquito. Copyright © 2015 Elsevier Inc. All rights reserved.

Insecticide exposure impacts vector-parasite interactions in insecticide-resistant malaria vectors.

PubMed

Alout, Haoues; Djègbè, Innocent; Chandre, Fabrice; Djogbénou, Luc Salako; Dabiré, Roch Kounbobr; Corbel, Vincent; Cohuet, Anna

2014-07-07

Currently, there is a strong trend towards increasing insecticide-based vector control coverage in malaria endemic countries. The ecological consequence of insecticide applications has been mainly studied regarding the selection of resistance mechanisms; however, little is known about their impact on vector competence in mosquitoes responsible for malaria transmission. As they have limited toxicity to mosquitoes owing to the selection of resistance mechanisms, insecticides may also interact with pathogens developing in mosquitoes. In this study, we explored the impact of insecticide exposure on Plasmodium falciparum development in insecticide-resistant colonies of Anopheles gambiae s.s., homozygous for the ace-1 G119S mutation (Acerkis) or the kdr L1014F mutation (Kdrkis). Exposure to bendiocarb insecticide reduced the prevalence and intensity of P. falciparum oocysts developing in the infected midgut of the Acerkis strain, whereas exposure to dichlorodiphenyltrichloroethane reduced only the prevalence of P. falciparum infection in the Kdrkis strain. Thus, insecticide resistance leads to a selective pressure of insecticides on Plasmodium parasites, providing, to our knowledge, the first evidence of genotype by environment interactions on vector competence in a natural Anopheles-Plasmodium combination. Insecticide applications would affect the transmission of malaria in spite of resistance and would reduce to some degree the impact of insecticide resistance on malaria control interventions. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Combining fungal biopesticides and insecticide-treated bednets to enhance malaria control.

PubMed

Hancock, Penelope A

2009-10-01

In developing strategies to control malaria vectors, there is increased interest in biological methods that do not cause instant vector mortality, but have sublethal and lethal effects at different ages and stages in the mosquito life cycle. These techniques, particularly if integrated with other vector control interventions, may produce substantial reductions in malaria transmission due to the total effect of alterations to multiple life history parameters at relevant points in the life-cycle and transmission-cycle of the vector. To quantify this effect, an analytically tractable gonotrophic cycle model of mosquito-malaria interactions is developed that unites existing continuous and discrete feeding cycle approaches. As a case study, the combined use of fungal biopesticides and insecticide treated bednets (ITNs) is considered. Low values of the equilibrium EIR and human prevalence were obtained when fungal biopesticides and ITNs were combined, even for scenarios where each intervention acting alone had relatively little impact. The effect of the combined interventions on the equilibrium EIR was at least as strong as the multiplicative effect of both interventions. For scenarios representing difficult conditions for malaria control, due to high transmission intensity and widespread insecticide resistance, the effect of the combined interventions on the equilibrium EIR was greater than the multiplicative effect, as a result of synergistic interactions between the interventions. Fungal biopesticide application was found to be most effective when ITN coverage was high, producing significant reductions in equilibrium prevalence for low levels of biopesticide coverage. By incorporating biological mechanisms relevant to vectorial capacity, continuous-time vector population models can increase their applicability to integrated vector management.

Light manipulation of mosquito behaviour: acute and sustained photic suppression of biting activity in the Anopheles gambiae malaria mosquito.

PubMed

Sheppard, Aaron D; Rund, Samuel S C; George, Gary F; Clark, Erin; Acri, Dominic J; Duffield, Giles E

2017-06-16

Host-seeking behaviours in anopheline mosquitoes are time-of-day specific, with a greater propensity for nocturnal biting. We investigated how a short exposure to light presented during the night or late day can inhibit biting activity and modulate flight activity behaviour. Anopheles gambiae (s.s.), maintained on a 12:12 LD cycle, were exposed transiently to white light for 10-min at the onset of night and the proportion taking a blood meal in a human biting assay was recorded every 2 h over an 8-h duration. The pulse significantly reduced biting propensity in mosquitoes 2 h following administration, in some trials for 4 h, and with no differences detected after 6 h. Conversely, biting levels were significantly elevated when mosquitoes were exposed to a dark treatment during the late day, suggesting that light suppresses biting behaviour even during the late daytime. These data reveal a potent effect of a discrete light pulse on biting behaviour that is both immediate and sustained. We expanded this approach to develop a method to reduce biting propensity throughout the night by exposing mosquitoes to a series of 6- or 10-min pulses presented every 2 h. We reveal both an immediate suppressive effect of light during the exposure period and 2 h after the pulse. This response was found to be effective during most times of the night: however, differential responses that were time-of-day specific suggest an underlying circadian property of the mosquito physiology that results in an altered treatment efficacy. Finally, we examined the immediate and sustained effects of light on mosquito flight activity behaviour following exposure to a 30-min pulse, and observed activity suppression during early night, and elevated activity during the late night. As mosquitoes and malaria parasites are becoming increasingly resistant to insecticide and drug treatment respectively, there is a necessity for the development of innovative control strategies beyond insecticide-treated

Success of Senegal's first nationwide distribution of long-lasting insecticide-treated nets to children under five - contribution toward universal coverage

PubMed Central

2011-01-01

Background In 2009, the first national long-lasting insecticide-treated net (LLIN) distribution campaign in Senegal resulted in the distribution of 2.2 million LLINs in two phases to children aged 6-59 months. Door-to-door teams visited all households to administer vitamin A and mebendazole, and to give a coupon to redeem later for an LLIN. Methods A nationwide community-based two-stage cluster survey was conducted, with clusters selected within regions by probability proportional to size sampling, followed by GPS-assisted mapping, simple random selection of households in each cluster, and administration of a questionnaire using personal digital assistants (PDAs). The questionnaire followed the Malaria Indicator Survey format, with rosters of household members and bed nets, and questions on campaign participation. Results There were 3,280 households in 112 clusters representing 33,993 people. Most (92.1%) guardians of eligible children had heard about the campaign, the primary sources being health workers (33.7%), neighbours (26.2%), and radio (22.0%). Of eligible children, 82.4% received mebendazole, 83.8% received vitamin A, and 75.4% received LLINs. Almost all (91.4%) LLINs received during the campaign remained in the household; of those not remaining, 74.4% had been given away and none were reported sold. At least one insecticide-treated net (ITN) was present in 82.3% of all households, 89.2% of households with a child < 5 years and 57.5% of households without a child < 5 years. Just over half (52.4%) of ITNs had been received during the campaign. Considering possible indicators of universal coverage, 39.8% of households owned at least one ITN per two people, 21.6% owned at least one ITN per sleeping space and 34.7% of the general population slept under an ITN the night before the survey. In addition, 45.6% of children < 5 years, and 49.2% of pregnant women had slept under an ITN. Conclusions The nationwide integrated LLIN distribution campaign allowed

Repellent and mosquitocidal effects of leaf extracts of Clausena anisata against the Aedes aegypti mosquito (Diptera: Culicidae).

PubMed

Mukandiwa, Lillian; Eloff, Jacobus Nicolaas; Naidoo, Vinny

2016-06-01

Mosquitoes are rapidly developing resistance to insecticides that millions of people relied on to protect themselves from the diseases they carry, thereby creating a need to develop new insecticides. Clausena anisata is used traditionally as an insect repellent by various communities in Africa and Asia. For this study, the repellency and adulticidal activities of leaf extracts and compounds isolated from this plant species were evaluated against the yellow fever mosquito, Aedes aegypti. In the topical application assays, using total bites as an indicator, repellency was dose dependent, with the acetone crude extract (15 %) having 93 % repellence and the hexane fraction (7.5 %) 67 % repellence after 3 h. Fractionation resulted in a loss of total repellence. As mosquito-net treating agents, the acetone and hexane extracts of C. anisata, both at 15 %, had average repellences of 46.89 ± 2.95 and 50.13 ± 2.02 %, respectively, 3 h after exposure. The C. anisata acetone extract and its hexane fraction caused mosquito knockdown and eventually death when nebulised into the testing chamber, with an EC50 of 78.9 mg/ml (7.89 %) and 71.6 mg/ml (7.16 %) in the first 15 min after spraying. C. anisata leaf extracts have potential to be included in protection products against mosquitoes due to the repellent and cidal compounds contained therein.

Impact of operational effectiveness of long-lasting insecticidal nets (LLINs) on malaria transmission in pyrethroid-resistant areas

PubMed Central

2013-01-01

Background A dynamic study on the transmission of malaria was conducted in two areas (R+ area: Low resistance area; R+++ area: High resistance area) in the department of Plateau in South Eastern Benin, where the population is protected by Long Lasting Insecticidal Nets (LLINs). The aim of this study was to determine if the resistance of malaria vectors to insecticides has an impact on their behavior and on the effectiveness of LLINs in the reduction of malaria transmission. Methods Populations of Anopheles gambiae s.l. were sampled monthly by human landing catch in the two areas to evaluate human biting rates (HBR). Collected mosquitoes were identified morphologically and female Anopheles mosquitoes were tested for the presence of Plasmodium falciparum antigen as assessed using ELISA. The entomological inoculation rate (EIR) was also calculated (EIR = HBR x sporozoitic index [S]). We estimated the parity rate by dissecting the females of An. gambiae. Finally, window catch and spray catch were conducted in order to assess the blood feeding rate and the exophily rate of vectors. Results After 6 months of tracking the mosquito's behavior in contact with the LLINs (Olyset) in R+++ and R+ areas, the entomological indicators of the transmission of malaria (parity rate and sporozoitic index) were similar in the two areas. Also, An. gambiae populations showed the same susceptibility to P. falciparum in both R+ and R+++ areas. The EIR and the exophily rate are higher in R+ area than in R+++ area. But the blood-feeding rate is lower in R+ area comparing to R+++. Conclusion The highest entomological inoculation rate observed in R+ area is mostly due to the strong aggressive density of An. gambiae recorded in one of the study localities. On the other hand, the highest exophily rate and the low blood-feeding rate recorded in R+ area compared to R+++ area are not due to the resistance status of An. gambiae, but due to the differences in distribution and availability of

Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana.

PubMed

Mnyone, Ladslaus L; Koenraadt, Constantianus Jm; Lyimo, Issa N; Mpingwa, Monica W; Takken, Willem; Russell, Tanya L

2010-08-27

Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi.

Discovery of Species-selective and Resistance-breaking Anticholinesterase Insecticides for the Malaria Mosquito

PubMed Central

Carlier, Paul R.; Bloomquist, Jeffrey R.; Totrov, Max; Li, Jianyong

2017-01-01

Great reductions in malaria mortality have been accomplished in the last 15 years, in part due to the widespread roll-out of insecticide-treated bednets across sub-Saharan Africa. To date, these nets only employ pyrethroids, insecticides that target the voltage-gated sodium ion channel of the malaria vector, Anopheles gambiae. Due to the growing emergence of An. gambiae strains that are resistant to pyrethroids, there is an urgent need to develop new public health insecticides that engage a different target and possess low mammalian toxicity. In this review, we will describe efforts to develop highly species-specific and resistance-breaking inhibitors of An. gambiae acetylcholinesterase (AgAChE). These efforts have been greatly aided by advances in knowledge of the structure of the enzyme, and two major inhibitor design strategies have been explored. Since AgAChE possesses an unpaired Cys residue not present in mammalian AChE, a logical strategy to achieve selective inhibition involves design of compounds that could ligate that Cys. A second strategy involves the design of new molecules to target the catalytic serine of the enzyme. Here the challenge is not only to achieve high inhibition selectivity vs human AChE, but also to demonstrate toxicity to An. gambiae that carry the G119S resistance mutation of AgAChE. The advances made and challenges remaining will be presented. This review is part of the special issue “Insecticide Mode of Action: From Insect to Mammalian Toxicity. PMID:28176636

Status of insecticide resistance in high-risk malaria provinces in Afghanistan.

PubMed

Ahmad, Mushtaq; Buhler, Cyril; Pignatelli, Patricia; Ranson, Hilary; Nahzat, Sami Mohammad; Naseem, Mohammad; Sabawoon, Muhammad Farooq; Siddiqi, Abdul Majeed; Vink, Martijn

2016-02-18

Insecticide resistance seriously threatens the efficacy of vector control interventions in malaria endemic countries. In Afghanistan, the status of insecticide resistance is largely unknown while distribution of long-lasting insecticidal nets has intensified in recent years. The main objective of this study was thus to measure the level of resistance to four classes of insecticides in provinces with medium to high risk of malaria transmission. Adult female mosquitoes were reared from larvae successively collected in the provinces of Nangarhar, Kunar, Badakhshan, Ghazni and Laghman from August to October 2014. WHO insecticide susceptibility tests were performed with DDT (4 %), malathion (5 %), bendiocarb (0.1 %), permethrin (0.75 %) and deltamethrin (0.05 %). In addition, the presence of kdr mutations was investigated in deltamethrin resistant and susceptible Anopheles stephensi mosquitoes collected in the eastern provinces of Nangarhar and Kunar. Analyses of mortality rates revealed emerging resistance against all four classes of insecticides in the provinces located east and south of the Hindu Kush mountain range. Resistance is observed in both An. stephensi and Anopheles culicifacies, the two dominant malaria vectors in these provinces. Anopheles superpictus in the northern province of Badakhshan shows a different pattern of susceptibility with suspected resistance observed only for deltamethrin and bendiocarb. Genotype analysis of knock down resistance (kdr) mutations at the voltage-gated channel gene from An. stephensi mosquitoes shows the presence of the known resistant alleles L1014S and L1014F. However, a significant fraction of deltamethrin-resistant mosquitoes were homozygous for the 1014L wild type allele indicating that other mechanisms must be considered to account for the observed pyrethroid resistance. This study confirms the importance of monitoring insecticide resistance for the development of an integrated vector management in Afghanistan. The

MosquitoNet: investigating the use of UAV and artificial neural networks for integrated mosquito management

NASA Astrophysics Data System (ADS)

Case, E.; Ren, Y.; Shragai, T.; Erickson, D.

2017-12-01

Integrated mosquito control is expensive and resource intensive, and changing climatic factors are predicted to expand the habitable range of disease-carrying mosquitoes into new regions in the United States. Of particular concern in the northeastern United States are aedes albopictus, an aggressive, invasive species of mosquito that can transmit both native and exotic disease. Ae. albopictus prefer to live near human populations and breed in artificial containers with as little as two millimeters of standing water, exponentially increasing the difficulty of source control in suburban and urban areas. However, low-cost unmanned aerial vehicles (UAVs) can be used to photograph large regions at centimeter-resolution, and can image containers of interest in suburban neighborhoods. While proofs-of-concepts have been shown using UAVs to identify naturally occurring bodies of water, they have not been used to identify mosquito habitat in more populated areas. One of the primary challenges is that post-processing high-resolution aerial imagery is still time intensive, often labelled by hand or with programs built for satellite imagery. Artificial neural networks have been highly successful at image recognition tasks; in the past five years, convolutional neural networks (CNN) have surpassed or aided trained humans in identification of skin cancer, agricultural crops, and poverty levels from satellite imagery. MosquitoNet, a dual classifier built from the Single Shot Multibox Detector and VGG16 architectures, was trained on UAV­­­­­ aerial imagery taken during a larval study in Westchester County in southern New York State in July and August 2017. MosquitoNet was designed to assess the habitat risk of suburban properties by automating the identification and counting of containers like tires, toys, garbage bins, flower pots, etc. The SSD-based architecture marked small containers and other habitat indicators while the VGG16-based architecture classified the type of

Insecticide resistance to permethrin and malathion and associated mechanisms in Aedes aegypti mosquitoes from St. Andrew Jamaica

PubMed Central

Francis, Sheena; Saavedra-Rodriguez, Karla; Perera, Rushika; Paine, Mark; Black, William C.

2017-01-01

The emergence of novel diseases spread by the Aedes aegypti mosquito in Jamaica and the Caribbean, has prompted studies on insecticide resistance towards effective management of the vector. Though Jamaica has been using the organophosphate insecticide malathion in its vector control program for more than 30 years, resistance to the pesticide has not been tested in over a decade. We analyzed resistance to malathion and the pyrethroid insecticide, permethrin on mosquitoes collected across St. Andrew, Jamaica, and analyzed the molecular basis of resistance. The Center for Disease Control (CDC) bioassay revealed that Ae. aegypti mosquitoes from St. Andrew, Jamaica were resistant to permethrin (15 μg/bottle) with mortalities at 0–8% at 30 minute exposure time, while contact with malathion (50 μg/bottle) revealed ≤ 50% mortality at 15 minutes, which increased to 100% at 45 minutes. The standard susceptible New Orleans (NO) strain exhibited 100% mortality within15 minutes. The activities of multifunction oxidases and p-nitro phenyl-acetate esterases were significantly greater in most Jamaican populations in comparison to the NO strain, while activities of glutathione-S-transferase, acetylcholinesterase, α-esterase and ß-esterase activity were relatively equal, or lower than that of the control strain. The frequency of knockdown resistance mutations in the voltage dependent sodium channel gene were measured. All collections were fixed for Cys1,534 while 56% of mosquitoes were Ile1,016/Val1,016 heterozygotes, and 33% were Ile1,016 homozygotes. Aedes aegypti from St. Andrew Jamaica are resistant to permethrin with variations in the mode of mechanism, and possibly developing resistance to malathion. Continued monitoring of resistance is critically important to manage the spread of the vector in the country. PMID:28650966

Insecticidal and repellent activity of Clausena dentata (Rutaceae) plant extracts against Aedes aegypti and Culex quinquefasciatus mosquitoes (Diptera: Culicidae).

PubMed

Ramkumar, Govindaraju; Karthi, Sengodan; Muthusamy, Ranganathan; Natarajan, Devarajan; Shivakumar, Muthugounder Subramanian

2015-03-01

Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol agents. The present study is to evaluate adulticidal activity of Clausena dentata plant extract against Aedes aegypti and Culex quinquefasciatus mosquitoes. The adult mortality was observed after 24 h of exposure. The highest mortality was found in acetone extracts against Ae. aegypti and Cx. quinquefasciatus with the LC50 and LC90 4.1783 mg/ml (3.8201-7.1026), 9.3884 mg/ml (7. 8258-13.1820) and 4.2451 mg/ml (3.8547-8.0254), 12.3214 mg/ml (10.9287-16.2220), respectively. Smoke toxicity was observed at 10-min interval for 40 min, and the mortality data were recorded. Result shows that Ae. aegypti and Cx. quinquefasciatus are 85 ± 2 and 89 ± 1.5, respectively. A mortality of 100 % was recorded in the commercial mosquito control. These results suggest that the leaf extracts of C. dentata have a potential to be used as an ideal eco-friendly approach for the control of mosquitoes.

Are Long-Lasting Insecticidal Nets Effective for Preventing Childhood Deaths among Non-Net Users? A Community-Based Cohort Study in Western Kenya

PubMed Central

Komazawa, Osuke; Kaneko, Satoshi; K’Opiyo, James; Kiche, Ibrahim; Wanyua, Sheru; Shimada, Masaaki; Karama, Mohamed

2012-01-01

Background Increasing the distribution and use of insecticide-treated nets (ITNs) in Sub-Saharan Africa has made controlling malaria with ITNs more practical. We evaluated community effects induced by ITNs, specifically long-lasting insecticidal nets (LLINs), under ordinary conditions in an endemic malaria area of Western Kenya. Methods Using the database from Mbita Health and Demographic Surveillance System (HDSS), children younger than 5 years old were assessed over four survey periods. We analyzed the effect of bed net usage, LLIN density and population density of young people around a child on all-cause child mortality (ACCM) rates using Cox PH models. Results During the study, 14,554 children were followed and 250 deaths were recorded. The adjusted hazard ratios (HRs) for LLIN usage compared with no net usage were not significant among the models: 1.08 (95%CI 0.76–1.52), 1.19 (95%CI 0.69–2.08) and 0.92 (95%CI 0.42–2.02) for LLIN users, untreated net users, and any net users, respectively. A significant increasing linear trend in risk across LLIN density quartiles (HR = 1.25; 95%CI 1.03–1.51) and a decreasing linear trend in risk across young population density quartiles among non-net user children (HR = 0.77; 95%CI 0.63–0.94) were observed. Conclusions Although our data showed that current LLIN coverage level (about 35%) could induce a community effect to protect children sleeping without bed nets even in a malaria-endemic area, it appears that a better system is needed to monitor the current malaria situation globally in order to optimize malaria control programs with limited resources. PMID:23185378

Malaria in Dielmo, a Senegal village: Is its elimination possible after seven years of implementation of long-lasting insecticide-treated nets?

PubMed

Wotodjo, Amélé Nyedzie; Doucoure, Souleymane; Gaudart, Jean; Diagne, Nafissatou; Diene Sarr, Fatoumata; Faye, Ngor; Tall, Adama; Raoult, Didier; Sokhna, Cheikh

2017-01-01

The malaria burden has decreased significantly in recent years in Africa through the widespread use of artemisinin-based combination therapy (ACT) and long-lasting insecticide-treated nets (LLINs). However, the occurrence of malaria resurgences, the loss of immunity of exposed populations constitute among other factors, serious concerns about the future of malaria elimination efforts. This study investigated the evolution of malaria morbidity in Dielmo (Senegal) before and after the implementation of LLINs. A longitudinal study was carried out in Dielmo over eight years, from July 2007 to July 2015. In July 2008, LLINs were offered to all villagers, and in July 2011 and August 2014 the LLINs were renewed. A survey on LLINs use was done each quarter of the year. Thick smears stained with Giemsa, a rapid diagnostic test (RDT) and quantitative polymerase chain reaction (PCR) methods were performed for all cases of fever to assess malaria clinical attacks. Malaria cases were treated with ACT since June 2006. Malaria morbidity has decreased significantly since the implementation of LLINs in Dielmo, together with ACT. However, malaria resurgences have occurred twice during the seven years of LLINs use. These resurgences occurred the first time during the third year after the introduction of LLINs (aIRR (adjusted incidence-rate ratio) [95%CI] = 5.90 [3.53; 9.88] p< 0.001) and a second time during the third year after the renewal of LLINs (aIRR [95%CI] = 5.60 [3.34; 9.39] p< 0.001). Sixty-nine percent (69%) of the nets tested for their long-lasting insecticidal activity remained effective after 3 years of use. Good management of malaria cases by the use of ACT as first-line treatment against malaria in addition to the use of LLINs has significantly reduced malaria in Dielmo and allowed to reach the phase of pre-elimination of the disease. However, the occurrence of malaria resurgences raised serious concerns about malaria elimination, which would require additional tools

Analysis of population structure and insecticide resistance in mosquitoes of the genus Culex, Anopheles and Aedes from different environments of Greece with a history of mosquito borne disease transmission.

PubMed

Fotakis, Emmanouil A; Chaskopoulou, Alexandra; Grigoraki, Linda; Tsiamantas, Alexandros; Kounadi, Stella; Georgiou, Loukas; Vontas, John

2017-10-01

Greece has been recently affected by several mosquito borne diseases with the West Nile Virus (WNV) outbreak in 2010 being one of the largest reported in Europe. Currently at the epicenter of an economic and refugee crisis and visited by over 16 million tourists a year the integrated management of diseases transmitted by mosquitoes is a public health and economic priority. Vector control programs rely mainly on insecticides, however data on insecticide resistance and the mosquito fauna is essential for successful applications. We determined the mosquito species composition and population dynamics in areas of increased vulnerability to vector borne disease transmission, as well as investigated the resistance status of major nuisance and disease vectors to insecticides. High mosquito densities were recorded in Thessaloniki and Evros, with Aedes caspius, a nuisance species, Culex pipiens, a known vector of WNV and Anopheles hyrcanus a potential vector of malaria being among the most prevalent species. Both vector species populations reached their peak in late summer. Aedes albopictus was recorded at high densities in Thessaloniki, but not in Evros. Notably, Cx. pipiens hybrids, which show an opportunistic biting behavior and are suspected to be involved in the transmission of the WNV, were recorded in considerable numbers in Thessaloniki and Attica. Culex pipiens and An. hyrcanus, but not Ae. caspius mosquitoes, showed moderate levels of resistance to deltamethrin. The presence of resistance in areas not exposed to vector control indicates that other factors could be selecting for resistance, i.e. pesticide applications for agriculture. Both L1014F and L101C kdr mutations were detected in Cx. pipiens populations. Anopheles hyrcanus resistance was not associated with mutations at the L1014 site. The Ace-1 mutations conferring insensitivity to organophosphates and carbamates were detected at low frequencies in all Cx. pipiens populations. Increased activity of P450s and

Long-term trends in Anopheles gambiae insecticide resistance in Côte d'Ivoire.

PubMed

Edi, Constant A V; Koudou, Benjamin G; Bellai, Louise; Adja, Akre M; Chouaibou, Mouhamadou; Bonfoh, Bassirou; Barry, Sarah J E; Johnson, Paul C D; Müller, Pie; Dongus, Stefan; N'Goran, Eliezer K; Ranson, Hilary; Weetman, David

2014-11-28

Malaria control is heavily dependent on the use of insecticides that target adult mosquito vectors via insecticide treated nets (ITNs) or indoor residual spraying (IRS). Four classes of insecticide are approved for IRS but only pyrethroids are available for ITNs. The rapid rise in insecticide resistance in African malaria vectors has raised alarms about the sustainability of existing malaria control activities. This problem might be particularly acute in Côte d'Ivoire where resistance to all four insecticide classes has recently been recorded. Here we investigate temporal trends in insecticide resistance across the ecological zones of Côte d'Ivoire to determine whether apparent pan-African patterns of increasing resistance are detectable and consistent across insecticides and areas. We combined data on insecticide resistance from a literature review, and bioassays conducted on field-caught Anopheles gambiae mosquitoes for the four WHO-approved insecticide classes for ITN/IRS. The data were then mapped using Geographical Information Systems (GIS) and the IR mapper tool to provide spatial and temporal distribution data on insecticide resistance in An. gambiae sensu lato from Côte d'Ivoire between 1993 and 2014. Bioassay mortality decreased over time for all insecticide classes, though with significant spatiotemporal variation, such that stronger declines were observed in the southern ecological zone for DDT and pyrethroids than in the central zone, but with an apparently opposite effect for the carbamate and organophosphate. Variation in relative abundance of the molecular forms, coupled with dramatic increase in kdr 1014F frequency in M forms (An. coluzzii) seems likely to be a contributory factor to these patterns. Although records of resistance across insecticide classes have become more common, the number of classes tested in studies has also increased, precluding a conclusion that multiple resistance has also increased. Our analyses attempted synthesis of 22�

Maintenance and sustained use of insecticide-treated bednets and curtains three years after a controlled trial in western Kenya.

PubMed

Kachur, S P; Phillips-Howard, P A; Odhacha, A M; Ruebush, T K; Oloo, A J; Nahlen, B L

1999-11-01

In large experimental trials throughout Africa, insecticide-treated bednets and curtains have reduced child mortality in malaria-endemic communities by 15%-30%. While few questions remain about the efficacy of this intervention, operational issues around how to implement and sustain insecticide-treated materials (ITM) projects need attention. We revisited the site of a small-scale ITM intervention trial, 3 years after the project ended, to assess how local attitudes and practices had changed. Qualitative and quantitative methods, including 16 focus group discussions and a household survey (n = 60), were employed to assess use, maintenance, retreatment and perceptions of ITM and the insecticide in former study communities. Families that had been issued bednets were more likely to have kept and maintained them and valued bednets more highly than those who had been issued curtains. While most households retained their original bednets, none had treated them with insecticide since the intervention trial was completed 3 years earlier. Most of those who had been issued bednets repaired them, but none acquired new or replacement nets. In contrast, households that had been issued insecticide-treated curtains often removed them. Three (15%) of the households issued curtains had purchased one or more bednets since the study ended. In households where bednets had been issued, children 10 years of age and younger were a third as likely to sleep under a net as were adults (relative risk (RR) = 0. 32; 95% confidence interval (95%CI) = 0.19, 0.53). Understanding how and why optimal ITM use declined following this small-scale intervention trial can suggest measures that may improve the sustainability of current and future ITM efforts.

Repeated mass distributions and continuous distribution of long-lasting insecticidal nets: modelling sustainability of health benefits from mosquito nets, depending on case management.

PubMed

Briët, Olivier Jt; Penny, Melissa A

2013-11-07

Stagnating funds for malaria control have spurred interest in the question of how to sustain the gains of recent successes with long-lasting insecticidal nets (LLINs) and improved case management (CM). This simulation study examined the malaria transmission and disease dynamics in scenarios with sustained LLINs and CM interventions and tried to determine optimal LLIN distribution rates. The effects of abruptly halting LLIN distribution were also examined. Dynamic simulations of malaria in humans and mosquitoes were run on the OpenMalaria platform, using stochastic individual-based simulation models. LLINs were distributed in a range of transmission settings, with varying CM coverage levels. In the short-term, LLINs were beneficial over the entire transmission spectrum, reducing both transmission and disease burden. In the long-term, repeated distributions sustainably reduced transmission in all settings. However, because of the resulting reduction in acquired immunity in the population, the malaria disease burden, after initially being reduced, gradually increased and eventually stabilized at a new level. This new level was higher than the pre-intervention level in previously high transmission settings, if there is a maximum disease burden in the relationship between transmission and disease burden at intermediate transmission levels. This result could lead one to conclude that sustained LLIN distribution might not be cost-effective in high transmission settings in the long term. However, improved CM rendered LLINs more cost-effective in higher transmission settings than in those without improved CM and the majority of the African population lives in areas where CM and LLINs are sustainably combined. The effects of changes in LLIN distribution rate on cost-effectiveness were relatively small compared to the effects of changes in transmission setting and CM. Abruptly halting LLIN distribution led to temporary morbidity peaks, which were particularly large in low to

MIRO and IRbase: IT Tools for the Epidemiological Monitoring of Insecticide Resistance in Mosquito Disease Vectors

PubMed Central

Dialynas, Emmanuel; Topalis, Pantelis; Vontas, John; Louis, Christos

2009-01-01

Background Monitoring of insect vector populations with respect to their susceptibility to one or more insecticides is a crucial element of the strategies used for the control of arthropod-borne diseases. This management task can nowadays be achieved more efficiently when assisted by IT (Information Technology) tools, ranging from modern integrated databases to GIS (Geographic Information System). Here we describe an application ontology that we developed de novo, and a specially designed database that, based on this ontology, can be used for the purpose of controlling mosquitoes and, thus, the diseases that they transmit. Methodology/Principal Findings The ontology, named MIRO for Mosquito Insecticide Resistance Ontology, developed using the OBO-Edit software, describes all pertinent aspects of insecticide resistance, including specific methodology and mode of action. MIRO, then, forms the basis for the design and development of a dedicated database, IRbase, constructed using open source software, which can be used to retrieve data on mosquito populations in a temporally and spatially separate way, as well as to map the output using a Google Earth interface. The dependency of the database on the MIRO allows for a rational and efficient hierarchical search possibility. Conclusions/Significance The fact that the MIRO complies with the rules set forward by the OBO (Open Biomedical Ontologies) Foundry introduces cross-referencing with other biomedical ontologies and, thus, both MIRO and IRbase are suitable as parts of future comprehensive surveillance tools and decision support systems that will be used for the control of vector-borne diseases. MIRO is downloadable from and IRbase is accessible at VectorBase, the NIAID-sponsored open access database for arthropod vectors of disease. PMID:19547750

Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana

PubMed Central

2010-01-01

Background Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Methods Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Results Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Conclusion Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi. PMID:20799937

Video studies of passage by Anopheles gambiae mosquitoes through holes in a simulated bed net: effects of hole size, hole orientation and net environment.

PubMed

Sutcliffe, James; Colborn, Kathryn L

2015-05-13

Holes in netting provide potential routes for mosquitoes to enter ITNs. Despite this, there is little information on how mosquitoes respond to holes in bed nets and how their responses are affected by hole size, shape and orientation or by ambient conditions around the net. Female Anopheles gambiae (G3) were recorded in a simulated bed net consisting of two sizes of untreated netting-covered behavioural arenas placed above and beside (to simulate the bed net roof and sides respectively) the experimenter who was a source of host cues from 'inside' the net. A round hole of 9 mm or 13 mm diameter was cut into the centre of the netting of each arena. Videos of unfed female mosquitoes in arenas were analysed for time spent flying, walking and standing still and for exit through the hole. The effects of the experimenter on temperature and relative humidity around the simulated net were also measured. Mosquitoes were significantly more active in overhead arenas than in arenas to the side. Hole passage was significantly more likely in smaller arenas than larger ones and for larger holes than smaller ones. In arenas to the side, hole passage rate through small holes was about 50% less likely than what could be explained by area alone. Passage rate through holes in overhead arenas was consistent with hole area. Temperature in arenas did not strongly reflect the experimenter's presence in the simulated net. Relative humidity and absolute humidity in overhead arenas, but not in arenas to the side, were immediately affected by experimenter presence. Higher levels of activity in overhead arenas than in arenas to the side were likely due to the rising heat and humidity plume from the experimenter. Lower than expected passage rates through smaller vertically oriented holes may have been be due to an edge effect that does not apply to horizontally oriented holes. Results suggest that current methods of assessing the importance of physical damage to ITNs may not accurately reflect

Combination of Insecticide Treated Nets and Indoor Residual Spraying in Northern Tanzania Provides Additional Reduction in Vector Population Density and Malaria Transmission Rates Compared to Insecticide Treated Nets Alone: A Randomised Control Trial.

PubMed

Protopopoff, Natacha; Wright, Alexandra; West, Philippa A; Tigererwa, Robinson; Mosha, Franklin W; Kisinza, William; Kleinschmidt, Immo; Rowland, Mark

2015-01-01

Indoor residual spraying (IRS) combined with insecticide treated nets (ITN) has been implemented together in several sub-Saharan countries with inconclusive evidence that the combined intervention provides added benefit. The impact on malaria transmission was evaluated in a cluster randomised trial comparing two rounds of IRS with bendiocarb plus universal coverage ITNs, with ITNs alone in northern Tanzania. From April 2011 to December 2012, eight houses in 20 clusters per study arm were sampled monthly for one night with CDC light trap collections. Anopheles gambiae s.l. were identified to species using real time PCR Taq Man and tested for the presence of Plasmodium falciparum circumsporozoite protein. ITN and IRS coverage was estimated from household surveys. IRS coverage was more than 85% in two rounds of spraying in January and April 2012. Household coverage with at least one ITN per house was 94.7% after the universal coverage net campaign in the baseline year and the proportion of household with all sleeping places covered by LLIN was 50.1% decreasing to 39.1% by the end of the intervention year. An.gambiae s.s. comprised 80% and An.arabiensis 18.3% of the anopheline collection in the baseline year. Mean An.gambiae s.l. density in the ITN+IRS arm was reduced by 84% (95%CI: 56%-94%, p = 0.001) relative to the ITN arm. In the stratum of clusters categorised as high anopheline density at baseline EIR was lower in the ITN+IRS arm compared to the ITN arm (0.5 versus 5.4 per house per month, Incidence Rate Ratio: 0.10, 95%CI: 0.01-0.66, p-value for interaction <0.001). This trial provides conclusive evidence that combining carbamate IRS and ITNs produces major reduction in Anopheles density and entomological inoculation rate compared to ITN alone in an area of moderate coverage of LLIN and high pyrethroid resistance in An.gambiae s.s.

Ownership and use of insecticide-treated nets during pregnancy in sub-Saharan Africa: a review

PubMed Central

2013-01-01

Over the past decade, significant gains have been made in the implementation of malaria prevention measures in pregnancy in sub-Saharan Africa, including the distribution of insecticide-treated nets (ITNs). These have been shown to cause a reduction in the incidence of malaria and its consequences such as maternal anaemia, stillbirths and intrauterine growth restriction. Currently most nations in Africa have policies for distributing ITNs to pregnant women through various mechanisms, however coverage remains well below the targets. This review summarizes recent evidence regarding the correlation between ownership and use of ITNs and the determinants of both, in pregnancy in sub-Saharan Africa, and reviews interventions directed at improving coverage. A review of the literature using Pubmed, CINAHL and scanning of reference lists was conducted in October 2012 and 59 articles were selected for final review. The research obtained was a mixture of national and district level surveys, and a narrative synthesis of the data was undertaken. Ownership of ITNs varied from as low as 3% to greater than 80%, and the main determinants were found to be education level, knowledge of malaria, community involvement, socio-economic status and parity, although the significance of each varied between the different settings and studies reviewed. In more than half the settings where data were available, the combination of lack of availability and lack of use of an available net meant that less than half of all pregnancies received the recommended intervention. Supply and cost remain major barriers to achieving optimal coverage, but the additional important contributor to reduced efficiency of intervention was the clear discrepancy between ownership and use, with available ITN use below 60% in several settings. Cited reasons for not using an ITN, where one was available, included discomfort, problems with hanging up nets and lack of space, low awareness of need, and seasonal variations in

Clinical malaria among pregnant women on combined insecticide treated nets (ITNs) and intermittent preventive treatment (IPTp) with sulphadoxine-pyrimethamine in Yaounde, Cameroon.

PubMed

Mbu, Robinson Enow; Takang, William Ako; Fouedjio, Hortence Jeanne; Fouelifack, Florent Ymele; Tumasang, Florence Ndikum; Tonye, Rebecca

2014-05-16

Malaria remains a burden for pregnant women and the under 5. Intermittent preventive treatment of pregnant women (IPTp) for malaria with sulfadoxine - pyrimethamine (SP) has since replaced prophylaxis and legislation has been reinforced in the area of insecticide treated mosquito nets (ITNs) in Cameroon. Clinical malaria despite all these measures remains a problem. We compared the socio-obstetrical characteristics of women who developed clinical malaria and those who did not though in the same regimen. A 5 - year nested cohort study (2007 - 2011 inclusive) at the tertiary level hospitals in Yaounde. Pregnant women who willingly accepted to participate in the study were enrolled at booking and three doses of SP were administered between 18 - 20 weeks of gestation, between 26-28 weeks and between 32 - 34 weeks. Those who developed clinical malaria were considered as cases and were compared for socio - obstetrical characteristics with those who did not. Venous blood was drawn from the women in both arms for parasite density estimation and identification and all the clinical cases were treated conventionally. Each arm had 166 cases and many women who developed clinical malaria were between 15 and 19 years (OR 5.5, 95% CI 3.9 - 5.3, p < 0.001). They were of low gravidity (OR 6.5, 95% CI 3.8 - 11.3, p < 0.001) as well as low parity (OR 4.6, 95% CI 2.7 - 7.9, p < 0.001). The cases were single women (OR 4.58, 95% CI 2.54 - 8.26, p < 0.001) and had attained only primary level of education (OR 4.6, 95% CI 2.8 - 7.9, p < 0.001). Gestational ages were between 20 to 30 weeks during clinical malaria (OR 6.8, 95% CI 4.1 - 11.7, p < 0.001). The time between the first and second dose of SP was longer than ten weeks in the cases (OR 5.5, 95% CI 3.2 - 9.3, p < 0.001) and parasite density was higher also among the cases (OR 6.9, 95% CI 5.9 - 12.1, p < 0.001). Long spacing between the first and second dose of SP seemed to be responsible for clinical

Insecticide treated bednet strategy in rural settings: can we exploit women's decision making power?

PubMed

Tilak, Rina; Tilak, V W; Bhalwar, R

2007-01-01

Use of insecticide treated bednets in prevention of malaria is a widely propagated global strategy, however, its use has been reported to be influenced and limited by many variables especially gender bias. A cross sectional field epidemiological study was conducted in a rural setting with two outcome variables, 'Bednet use'(primary outcome variable) and 'Women's Decision Making Power' which were studied in reference to various predictor variables. Analysis reveals a significant effect on the primary outcome variable 'Bednet use' of the predictor variables- age, occupation, bednet purchase decision, women's decision making power, husband's education and knowledge about malaria and its prevention. The study recommends IEC on treated bednets to be disseminated through TV targeting the elderly women who have better decision making power and mobilizing younger women who were found to prefer bednets for prevention of mosquito bites for optimizing the use of treated bednets in similar settings.

Longevity and efficacy of bifenthrin treatment on desert-pattern US military camouflage netting against mosquitoes in a hot-arid environment.

PubMed

Britch, Seth C; Linthicum, Kenneth J; Wynn, Willard W; Aldridge, Robert L; Walker, Todd W; Farooq, Muhammad; Dunford, James C; Smith, Vincent L; Robinson, Cathy A; Lothrop, Branka B; Snelling, Melissa; Gutierrez, Arturo; Wittie, Jeremy; White, Gregory

2011-09-01

The current Department of Defense pest management system does not provide adequate protection from arthropod disease vectors to personnel deployed in support of US military operations. We hypothesized that military camouflage netting, ubiquitous around living and working areas in current US military operations in Africa and the Middle East, treated with a residual pesticide such as bifenthrin may reduce the presence of biting insects and improve the military pest management system. In this study, we examined the longevity and efficacy of bifenthrin applied to camouflage netting material at the maximum label rate of 0.03 liter formulation (7.9% AI) per 92.9 m2 against field populations of mosquitoes in southern California in a hot-arid environment similar to regions of Iraq, Afghanistan, and the Horn of Africa. We showed that bifenthrin treatment of camouflage netting was effective at reducing mosquito populations, predominantly Psorophora columbiae and Aedes vexans, by an average of up to 46% for 56 days, and could cause as much as 40% mortality in Culex quinquefasciatus in laboratory bioassays for nearly 2 months postapplication. These population reductions could translate to commensurate reductions in risk of exposure to mosquito-borne pathogens, and could potentially be effective against sand flies and filth flies.

An examination of the effect of aerosolized permanone insecticide on zebra finch susceptibility to West Nile virus

USGS Publications Warehouse

Jankowski, Mark D.; Murray, E. Moore; Hofmeister, Erik K.

2017-01-01

West Nile virus is primarily maintained cryptically primarily in avian (Passerine) populations where it is transmitted by Culex spp. mosquitoes. Mosquito control measures currently include physical activities to reduce mosquito breeding sites, the application of mosquito larvicides, or aerosolized insecticides to kill adults (adulticides) when arboviral diseases such as West Nile virus (WNV) or Zika virus are detected in mosquito populations. Organochlorine, organohosphorus, carbamate and pyrethroid insecticides are often used. Previous work suggests an effect of pyrethroids on the immune system in a variety of vertebrates. We examined the effects of exposure to aerosolized Permanone® 30:30 insecticide (permethrin and piperonyl butoxide in soy oil vehicle) at ∼103−106x potential environmental concentrations on the response of captive zebra finches (Taeniopygia guttata) to experimental challenge with WNV. Compared to vehicle control birds, WNV outcome was unchanged (65% of birds produced a viremia) in the ‘low’ exposure (9.52 mg/m3±3.13 SD permethrin) group, but reduced in the ‘high’ exposure (mean 376.5 mg/m3±27.9 SD permethrin) group (30% were viremic) (p < 0.05). After clearing WNV infection, birds treated with Permanone regained less body mass than vehicle treated birds (p < 0.001). Our study suggests that exposure to aerosolized Permanone insecticide at levels exceeding typical application rates has the potential to not change or mildly enhance a bird's resistance to WNV.

Evidence of carbamate resistance in urban populations of Anopheles gambiae s.s. mosquitoes resistant to DDT and deltamethrin insecticides in Lagos, South-Western Nigeria

PubMed Central

2012-01-01

Background Resistance monitoring is essential in ensuring the success of insecticide based vector control programmes. This study was carried out to assess the susceptibility status of urban populations of Anopheles gambiae to carbamate insecticide being considered for vector control in mosquito populations previously reported to be resistant to DDT and permethrin. Methods Two – three day old adult female Anopheles mosquitoes reared from larval collections in 11 study sites from Local Government Areas of Lagos were exposed to test papers impregnated with DDT 4%, deltamethrin 0.05% and propoxur 0.1% insecticides. Additional tests were carried out to determine the susceptibility status of the Anopheles gambiae population to bendiocarb insecticide. Members of the A. gambiae complex, the molecular forms, were identified by PCR assays. The involvement of metabolic enzymes in carbamate resistance was assessed using Piperonyl butoxide (PBO) synergist assays. The presence of kdr-w/e and ace-1R point mutations responsible for DDT-pyrethroid and carbamate resistance mechanisms was also investigated by PCR. Results Propoxur resistance was found in 10 out of the 11 study sites. Resistance to three classes of insecticides was observed in five urban localities. Mortality rates in mosquitoes exposed to deltamethrin and propoxur did not show any significant difference (P > 0.05) but was significantly higher (P < 0.05) in populations exposed to DDT. All mosquitoes tested were identified as A. gambiae s.s (M form). The kdr -w point mutation at allelic frequencies between 45%-77% was identified as one of the resistant mechanisms responsible for DDT and pyrethroid resistance. Ace-1R point mutation was absent in the carbamate resistant population. However, the possible involvement of metabolic resistance was confirmed by synergistic assays conducted. Conclusion Evidence of carbamate resistance in A. gambiae populations already harbouring resistance to DDT and permethrin is a

The use of mosquito nets in fisheries: A global perspective

PubMed Central

Gurung, Rajina; Rowcliffe, Marcus; Hill, Nicholas; Milner-Gulland, E. J.

2018-01-01

Free or subsidised mosquito net (MN) distribution has been an increasingly important tool in efforts to combat malaria in recent decades throughout the developing world, making great strides towards eradicating this hugely detrimental disease. However, there has been increasing concern in the natural resource management and healthcare communities over alternative use of MNs, particularly in artisanal fisheries where it has been suggested they pose a threat to sustainability of fish stocks. So far, little evidence has been presented as to the global prevalence and characteristics of MN fishing, limiting global management initiatives and incentives for action across disciplines. We conducted a rapid global assessment of mosquito net fishing (MNF) observations from expert witnesses living and/or working in malarial zones using an internet survey. MNF was found to be a broadly pan-tropical activity, particularly prevalent in sub-Saharan Africa. MNF is conducted using a variety of deployment methods and scales including seine nets, scoop/dip nets, set nets and traps. MNF was witnessed in a broad range of marine and freshwater habitats and was seen to exploit a wide range of taxa, with capture of juvenile fish reported in more than half of responses. Perceived drivers of MNF were closely related to poverty, revealing potentially complex and arguably detrimental livelihood and food security implications which we discuss in light of current literature and management paradigms. The key policies likely to influence future impacts of MNF are in health, regarding net distribution, and natural resource management regarding restrictions on use. We outline critical directions for research and highlight the need for a collaborative, interdisciplinary approach to development of both localised and broad-scale policy. PMID:29385189

Tips to Prevent Mosquito Bites

MedlinePlus

... mosquitoes using insecticides. Use Structural Barriers Cover all gaps in walls, doors, and windows to prevent mosquitoes ... into pants and pants into socks to cover gaps in your clothing where mosquitoes can get to ...

CYP6 P450 enzymes and ACE-1 duplication produce extreme and multiple insecticide resistance in the malaria mosquito Anopheles gambiae.

PubMed

Edi, Constant V; Djogbénou, Luc; Jenkins, Adam M; Regna, Kimberly; Muskavitch, Marc A T; Poupardin, Rodolphe; Jones, Christopher M; Essandoh, John; Kétoh, Guillaume K; Paine, Mark J I; Koudou, Benjamin G; Donnelly, Martin J; Ranson, Hilary; Weetman, David

2014-03-01

Malaria control relies heavily on pyrethroid insecticides, to which susceptibility is declining in Anopheles mosquitoes. To combat pyrethroid resistance, application of alternative insecticides is advocated for indoor residual spraying (IRS), and carbamates are increasingly important. Emergence of a very strong carbamate resistance phenotype in Anopheles gambiae from Tiassalé, Côte d'Ivoire, West Africa, is therefore a potentially major operational challenge, particularly because these malaria vectors now exhibit resistance to multiple insecticide classes. We investigated the genetic basis of resistance to the most commonly-applied carbamate, bendiocarb, in An. gambiae from Tiassalé. Geographically-replicated whole genome microarray experiments identified elevated P450 enzyme expression as associated with bendiocarb resistance, most notably genes from the CYP6 subfamily. P450s were further implicated in resistance phenotypes by induction of significantly elevated mortality to bendiocarb by the synergist piperonyl butoxide (PBO), which also enhanced the action of pyrethroids and an organophosphate. CYP6P3 and especially CYP6M2 produced bendiocarb resistance via transgenic expression in Drosophila in addition to pyrethroid resistance for both genes, and DDT resistance for CYP6M2 expression. CYP6M2 can thus cause resistance to three distinct classes of insecticide although the biochemical mechanism for carbamates is unclear because, in contrast to CYP6P3, recombinant CYP6M2 did not metabolise bendiocarb in vitro. Strongly bendiocarb resistant mosquitoes also displayed elevated expression of the acetylcholinesterase ACE-1 gene, arising at least in part from gene duplication, which confers a survival advantage to carriers of additional copies of resistant ACE-1 G119S alleles. Our results are alarming for vector-based malaria control. Extreme carbamate resistance in Tiassalé An. gambiae results from coupling of over-expressed target site allelic variants with

A Longitudinal Analysis of Mosquito Net Ownership and Use in an Indigenous Batwa Population after a Targeted Distribution

PubMed Central

Clark, Sierra; Berrang-Ford, Lea; Lwasa, Shuaib; Namanya, Didacus; Twesigomwe, Sabastian; Kulkarni, Manisha

2016-01-01

Major efforts for malaria prevention programs have gone into scaling up ownership and use of insecticidal mosquito nets, particularly in sub-Saharan Africa where the malaria burden is high. Socioeconomic inequities in access to long lasting insecticidal nets (LLINs) are reduced with free distributions of nets. However, the relationship between social factors and retention of nets after a free distribution has been less studied, particularly using a longitudinal approach. Our research aimed to estimate the ownership and use of LLINs, and examine the determinants of LLIN retention, within an Indigenous Batwa population after a free LLIN distribution. Two LLINs were given free of charge to each Batwa household in Kanungu District, Uganda in November 2012. Surveyors collected data on LLIN ownership and use through six cross-sectional surveys pre- and post-distribution. Household retention, within household access, and individual use of LLINs were assessed over an 18-month period. Socioeconomic determinants of household retention of LLINs post-distribution were modelled longitudinally using logistic regression with random effects. Direct house-to-house distribution of free LLINs did not result in sustainable increases in the ownership and use of LLINs. Three months post-distribution, only 73% of households owned at least one LLIN and this period also saw the greatest reduction in ownership compared to other study periods. Eighteen-months post distribution, only a third of households still owned a LLIN. Self-reported age-specific use of LLINs was generally higher for children under five, declined for children aged 6–12, and was highest for older adults aged over 35. In the model, household wealth was a significant predictor of LLIN retention, controlling for time and other variables. This research highlights on-going socioeconomic inequities in access to malaria prevention measures among the Batwa in southwestern Uganda, even after free distribution of LLINs, and

A Longitudinal Analysis of Mosquito Net Ownership and Use in an Indigenous Batwa Population after a Targeted Distribution.

PubMed

Clark, Sierra; Berrang-Ford, Lea; Lwasa, Shuaib; Namanya, Didacus; Twesigomwe, Sabastian; Kulkarni, Manisha

2016-01-01

Major efforts for malaria prevention programs have gone into scaling up ownership and use of insecticidal mosquito nets, particularly in sub-Saharan Africa where the malaria burden is high. Socioeconomic inequities in access to long lasting insecticidal nets (LLINs) are reduced with free distributions of nets. However, the relationship between social factors and retention of nets after a free distribution has been less studied, particularly using a longitudinal approach. Our research aimed to estimate the ownership and use of LLINs, and examine the determinants of LLIN retention, within an Indigenous Batwa population after a free LLIN distribution. Two LLINs were given free of charge to each Batwa household in Kanungu District, Uganda in November 2012. Surveyors collected data on LLIN ownership and use through six cross-sectional surveys pre- and post-distribution. Household retention, within household access, and individual use of LLINs were assessed over an 18-month period. Socioeconomic determinants of household retention of LLINs post-distribution were modelled longitudinally using logistic regression with random effects. Direct house-to-house distribution of free LLINs did not result in sustainable increases in the ownership and use of LLINs. Three months post-distribution, only 73% of households owned at least one LLIN and this period also saw the greatest reduction in ownership compared to other study periods. Eighteen-months post distribution, only a third of households still owned a LLIN. Self-reported age-specific use of LLINs was generally higher for children under five, declined for children aged 6-12, and was highest for older adults aged over 35. In the model, household wealth was a significant predictor of LLIN retention, controlling for time and other variables. This research highlights on-going socioeconomic inequities in access to malaria prevention measures among the Batwa in southwestern Uganda, even after free distribution of LLINs, and

Public-private delivery of insecticide-treated nets: a voucher scheme in Volta Region, Ghana

PubMed Central

Kweku, Margaret; Webster, Jayne; Taylor, Ian; Burns, Susan; Dedzo, McDamien

2007-01-01

Background Coverage of vulnerable groups with insecticide-treated nets (ITNs) in Ghana, as in the majority of countries of sub-Saharan Africa is currently low. A voucher scheme was introduced in Volta Region as a possible sustainable delivery system for increasing this coverage through scale-up to other regions. Successful scale-up of public health interventions depends upon optimal delivery processes but operational research for delivery processes in large-scale implementation has been inadequate. Methods A simple tool was developed to monitor numbers of vouchers given to each health facility, numbers issued to pregnant women by the health staff, and numbers redeemed by the distributors back to the management agent. Three rounds of interviews were undertaken with health facility staff, retailers and pregnant women who had attended antenatal clinic (ANC). Results During the one year pilot 25,926 vouchers were issued to eligible women from clinics, which equates to 50.7% of the 51,658 ANC registrants during this time period. Of the vouchers issued 66.7% were redeemed by distributors back to the management agent. Initially, non-issuing of vouchers to pregnant women was mainly due to eligibility criteria imposed by the midwives; later in the year it was due to decisions of the pregnant women, and supply constraints. These in turn were heavily influenced by factors external to the programme: current household ownership of nets, competing ITN delivery strategies, and competition for the limited number of ITNs available in the country from major urban areas of other regions. Conclusion Both issuing and redemption of vouchers should be monitored as factors assumed to influence voucher redemption had an influence on issuing, and vice versa. More evidence is needed on how specific contextual factors influence the success of voucher schemes and other models of delivery of ITNs. Such an evidence base will facilitate optimal strategic decision making so that the delivery model

Malaria control under the Taliban regime: insecticide-treated net purchasing, coverage, and usage among men and women in eastern Afghanistan.

PubMed

Howard, Natasha; Shafi, Ahmad; Jones, Caroline; Rowland, Mark

2010-01-06

Scaling up insecticide-treated mosquito net (ITN) coverage is a key malaria control strategy even in conflict-affected countries 12. Socio-economic factors influence access to ITNs whether subsidized or provided free to users. This study examines reported ITN purchasing, coverage, and usage in eastern Afghanistan and explores women's access to health information during the Taliban regime (1996-2001). This strengthens the knowledge base on household-level health choices in complex-emergency settings. Fifteen focus group discussions (FGDs) and thirty in-depth interviews were conducted with men and women from ITN-owning and non-owning households. FGDs included rank ordering, pile sorting and focused discussion of malaria knowledge and ITN purchasing. Interviews explored general health issues, prevention and treatment practices, and women's malaria knowledge and concerns. Seven key informant interviews with health-related workers and a concurrent survey of 200 ITN-owning and 214 non-owning households were used to clarify or quantify findings. Malaria knowledge was similar among men and women and ITN owners and non-owners. Women reported obtaining health information through a variety of sources including clinic staff, their husbands who had easier access to information, and particularly female peers. Most participants considered ITNs very desirable, though not usually household necessities. ITN owners reported more household assets than non-owners. Male ITN owners and non-owners ranked rugs and ITNs as most desired, while women ranked personal assets such as jewellery highest. While men were primarily responsible for household decision-making and purchasing, older women exerted considerable influence. Widow-led and landless households reported most difficulties purchasing ITNs. Most participants wanted to buy ITNs only if they could cover all household members. When not possible, preferential usage was given to women and children. Despite restricted access to health

Malaria control under the Taliban regime: insecticide-treated net purchasing, coverage, and usage among men and women in eastern Afghanistan

PubMed Central

2010-01-01

Background Scaling up insecticide-treated mosquito net (ITN) coverage is a key malaria control strategy even in conflict-affected countries [1,2]. Socio-economic factors influence access to ITNs whether subsidized or provided free to users. This study examines reported ITN purchasing, coverage, and usage in eastern Afghanistan and explores women's access to health information during the Taliban regime (1996-2001). This strengthens the knowledge base on household-level health choices in complex-emergency settings. Methods Fifteen focus group discussions (FGDs) and thirty in-depth interviews were conducted with men and women from ITN-owning and non-owning households. FGDs included rank ordering, pile sorting and focused discussion of malaria knowledge and ITN purchasing. Interviews explored general health issues, prevention and treatment practices, and women's malaria knowledge and concerns. Seven key informant interviews with health-related workers and a concurrent survey of 200 ITN-owning and 214 non-owning households were used to clarify or quantify findings. Results Malaria knowledge was similar among men and women and ITN owners and non-owners. Women reported obtaining health information through a variety of sources including clinic staff, their husbands who had easier access to information, and particularly female peers. Most participants considered ITNs very desirable, though not usually household necessities. ITN owners reported more household assets than non-owners. Male ITN owners and non-owners ranked rugs and ITNs as most desired, while women ranked personal assets such as jewellery highest. While men were primarily responsible for household decision-making and purchasing, older women exerted considerable influence. Widow-led and landless households reported most difficulties purchasing ITNs. Most participants wanted to buy ITNs only if they could cover all household members. When not possible, preferential usage was given to women and children

Species Identification and Resistance Status of Anopheles gambiae s.l. (Diptera: Culicidae) Mosquitoes in Guinea.

PubMed

Keita, K; Camara, D; Barry, Y; Ossè, R; Wang, L; Sylla, M; Miller, D; Leite, L; Schopp, P; Lawrence, G G; Akogbéto, M; Dotson, E M; Guilavogui, T; Keita, M; Irish, S R

2017-05-01

Insecticide resistance is one of the primary threats to the recent gains in malaria control. This is especially true in Guinea, where long-lasting insecticidal nets are currently the primary vector control intervention. To better inform the national malaria control program on the current status of insecticide resistance in Guinea, resistance bioassays were conducted, using Anopheles gambiae s.l. Giles, in three sites. Molecular analyses were also done on An. gambiae s.l. to determine the species and find whether the target-site mutations kdr and Ace1R were present. Susceptibility tests revealed resistance to DDT and pyrethroids, although mosquitoes were susceptible to deltamethrin in two of the three sites tested. Mosquitoes were susceptible to bendiocarb, except in Kissidougou, Guinea. The kdr-west mutation was widespread and the frequency was 60% or more in all sites. However, the Ace1R mutation was present in low levels. Insecticide susceptibility should continue to be monitored in Guinea to ensure insecticide-based vector control methods remain effective. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Efficiency Evaluation of Nozawa-Style Black Light Trap for Control of Anopheline Mosquitoes

PubMed Central

Lee, Hee Il; Seo, Bo Youl; Shin, E-Hyun; Burkett, Douglas A.; Lee, Jong-Koo

2009-01-01

House-residual spraying and insecticide-treated bed nets have achieved some success in controlling anthropophilic and endophagic vectors. However, these methods have relatively low efficacy in Korea because Anopheles sinensis, the primary malaria vector, is highly zoophilic and exophilic. So, we focused our vector control efforts within livestock enclosures using ultraviolet black light traps as a mechanical control measure. We found that black light traps captured significantly more mosquitoes at 2 and 2.5 m above the ground (P < 0.05). We also evaluated the effectiveness of trap spacing within the livestock enclosure. In general, traps spaced between 4 and 7 m apart captured mosquitoes more efficiently than those spaced closer together (P > 0.05). Based on these findings, we concluded that each black light trap in the livestock enclosures killed 7,586 female mosquitoes per trap per night during the peak mosquito season (July-August). In May-August 2003, additional concurrent field trials were conducted in Ganghwa county. We got 74.9% reduction (P < 0.05) of An. sinensis in human dwellings and 61.5% reduction (P > 0.05) in the livestock enclosures. The black light trap operation in the livestock enclosures proved to be an effective control method and should be incorporated into existing control strategies in developed countries. PMID:19488423

Multiple Resistances and Complex Mechanisms of Anopheles sinensis Mosquito: A Major Obstacle to Mosquito-Borne Diseases Control and Elimination in China

PubMed Central

Fang, Qiang; Hartsel, Joshua; Zhou, Guofa; Shi, Linna; Fang, Fujin; Zhu, Changliang; Yan, Guiyun

2014-01-01

Malaria, dengue fever, and filariasis are three of the most common mosquito-borne diseases worldwide. Malaria and lymphatic filariasis can occur as concomitant human infections while also sharing common mosquito vectors. The overall prevalence and health significance of malaria and filariasis have made them top priorities for global elimination and control programmes. Pyrethroid resistance in anopheline mosquito vectors represents a highly significant problem to malaria control worldwide. Several methods have been proposed to mitigate insecticide resistance, including rotational use of insecticides with different modes of action. Anopheles sinensis, an important malaria and filariasis vector in Southeast Asia, represents an interesting mosquito species for examining the consequences of long-term insecticide rotation use on resistance. We examined insecticide resistance in two An. Sinensis populations from central and southern China against pyrethroids, organochlorines, organophosphates, and carbamates, which are the major classes of insecticides recommended for indoor residual spray. We found that the mosquito populations were highly resistant to the four classes of insecticides. High frequency of kdr mutation was revealed in the central population, whereas no kdr mutation was detected in the southern population. The frequency of G119S mutation in the ace-1 gene was moderate in both populations. The classification and regression trees (CART) statistical analysis found that metabolic detoxification was the most important resistance mechanism, whereas target site insensitivity of L1014 kdr mutation played a less important role. Our results indicate that metabolic detoxification was the dominant mechanism of resistance compared to target site insensitivity, and suggests that long-term rotational use of various insecticides has led An. sinensis to evolve a high insecticide resistance. This study highlights the complex network of mechanisms conferring multiple

Patterns of insecticide resistance and knock down resistance (kdr) in malaria vectors An. arabiensis, An. coluzzii and An. gambiae from sympatric areas in Senegal.

PubMed

Niang, El Hadji Amadou; Konaté, Lassana; Diallo, Mawlouth; Faye, Ousmane; Dia, Ibrahima

2016-02-05

Malaria vector control in Africa relies on insecticides targeting adult mosquito vectors via insecticide treated nets or indoor residual spraying. Despite the proven efficacy of these strategies, the emergence and rapid rise in insecticide resistance in malaria vectors raises many concerns about their sustainability. Therefore, the monitoring of insecticide resistance is essential for resistance management strategies implementation. We investigated the kdr mutation frequencies in 20 sympatric sites of An. arabiensis Patton, An. coluzzii Coetzee & Wilkerson and An. gambiae Giles and its importance in malaria vector control by evaluating the susceptibility to insecticides in four representative sites in Senegal. Sibling species identification and kdr mutation detection were determined using polymerase chain reaction on mosquitoes collected using pyrethrum sprays collection in 20 sites belonging to two transects with differential insecticide selection pressure. The World Health Organization (WHO) tube test was used to determine phenotypic resistance of An. gambiae s.l. to DDT, deltamethrin, lambdacyholothrin, permethrin, bendiocarb and malathion in four representative sites. The L1014F kdr mutation was widely distributed and was predominant in An. gambiae in comparison to An. arabiensis and An. coluzzii. The bioassay tests showed a general trend with a resistance to DDT and pyrethroids and a susceptibility to organophosphate and carbamate according to WHO thresholds. For deltamethrin and permethrin, the two most used insecticides, no significant difference were observed either between the two transects or between mortality rates suggesting no differential selection pressures on malaria vectors. The study of the KD times showed similar trends as comparable levels of resistance were observed, the effect being more pronounced for permethrin. Our study showed a widespread resistance of malaria vectors to DDT and pyrethroids and a widespread distribution of the 1014F kdr

Importance of factors determining the effective lifetime of a mass, long-lasting, insecticidal net distribution: a sensitivity analysis

PubMed Central

2012-01-01

Background Long-lasting insecticidal nets (LLINs) reduce malaria transmission by protecting individuals from infectious bites, and by reducing mosquito survival. In recent years, millions of LLINs have been distributed across sub-Saharan Africa (SSA). Over time, LLINs decay physically and chemically and are destroyed, making repeated interventions necessary to prevent a resurgence of malaria. Because its effects on transmission are important (more so than the effects of individual protection), estimates of the lifetime of mass distribution rounds should be based on the effective length of epidemiological protection. Methods Simulation models, parameterised using available field data, were used to analyse how the distribution's effective lifetime depends on the transmission setting and on LLIN characteristics. Factors considered were the pre-intervention transmission level, initial coverage, net attrition, and both physical and chemical decay. An ensemble of 14 stochastic individual-based model variants for malaria in humans was used, combined with a deterministic model for malaria in mosquitoes. Results The effective lifetime was most sensitive to the pre-intervention transmission level, with a lifetime of almost 10 years at an entomological inoculation rate of two infectious bites per adult per annum (ibpapa), but of little more than 2 years at 256 ibpapa. The LLIN attrition rate and the insecticide decay rate were the next most important parameters. The lifetime was surprisingly insensitive to physical decay parameters, but this could change as physical integrity gains importance with the emergence and spread of pyrethroid resistance. Conclusions The strong dependency of the effective lifetime on the pre-intervention transmission level indicated that the required distribution frequency may vary more with the local entomological situation than with LLIN quality or the characteristics of the distribution system. This highlights the need for malaria monitoring both

Importance of factors determining the effective lifetime of a mass, long-lasting, insecticidal net distribution: a sensitivity analysis.

PubMed

Briët, Olivier J T; Hardy, Diggory; Smith, Thomas A

2012-01-13

Long-lasting insecticidal nets (LLINs) reduce malaria transmission by protecting individuals from infectious bites, and by reducing mosquito survival. In recent years, millions of LLINs have been distributed across sub-Saharan Africa (SSA). Over time, LLINs decay physically and chemically and are destroyed, making repeated interventions necessary to prevent a resurgence of malaria. Because its effects on transmission are important (more so than the effects of individual protection), estimates of the lifetime of mass distribution rounds should be based on the effective length of epidemiological protection. Simulation models, parameterised using available field data, were used to analyse how the distribution's effective lifetime depends on the transmission setting and on LLIN characteristics. Factors considered were the pre-intervention transmission level, initial coverage, net attrition, and both physical and chemical decay. An ensemble of 14 stochastic individual-based model variants for malaria in humans was used, combined with a deterministic model for malaria in mosquitoes. The effective lifetime was most sensitive to the pre-intervention transmission level, with a lifetime of almost 10 years at an entomological inoculation rate of two infectious bites per adult per annum (ibpapa), but of little more than 2 years at 256 ibpapa. The LLIN attrition rate and the insecticide decay rate were the next most important parameters. The lifetime was surprisingly insensitive to physical decay parameters, but this could change as physical integrity gains importance with the emergence and spread of pyrethroid resistance. The strong dependency of the effective lifetime on the pre-intervention transmission level indicated that the required distribution frequency may vary more with the local entomological situation than with LLIN quality or the characteristics of the distribution system. This highlights the need for malaria monitoring both before and during intervention

A natural agonist of mosquito TRPA1 from the medicinal plant Cinnamosma fragrans that is toxic, antifeedant, and repellent to the yellow fever mosquito Aedes aegypti.

PubMed

Inocente, Edna Alfaro; Shaya, Marguerite; Acosta, Nuris; Rakotondraibe, L Harinantenaina; Piermarini, Peter M

2018-02-01

Plants produce various secondary metabolites that offer a potential source of novel insecticides and repellents for the control of mosquito vectors. Plants of the genus Cinnamosma are endemic to, and widely-distributed throughout, the island of Madagascar. The barks of these species are commonly used in traditional medicines for treating a wide range of maladies. The therapeutic nature of the bark is thought to be associated with its enrichment of pungent drimane sesquiterpenes, which elicit antifeedant and toxic effects in some insects. Here we test the hypothesis that a bark extract of Cinnamosma fragrans (CINEX) and its major drimane sesquiterpenes are insecticidal, antifeedant, and repellent to Aedes aegypti, the principal mosquito vector of chikungunya, dengue, yellow fever, and Zika viruses. We demonstrate that CINEX is 1) toxic to larval and adult female mosquitoes, and 2) antifeedant and repellent to adult female mosquitoes. Moreover, we show that cinnamodial (CDIAL), a sesquiterpene dialdehyde isolated from CINEX, duplicates these bioactivities and exhibits similar toxic potency against pyrethroid-susceptible and -resistant strains of Ae. aegypti. Importantly, we show that CDIAL is an agonist of heterologously-expressed mosquito Transient Receptor Potential A1 (TRPA1) channels, and the antifeedant activity of CDIAL is dampened in a TRPA1-deficient strain of Ae. aegypti (TRPA1-/-). Intriguingly, TRPA1-/- mosquitoes do not exhibit toxic resistance to CDIAL. The data indicate that modulation of TRPA1 is required for the sensory detection and avoidance of CDIAL by mosquitoes, but not for inducing the molecule's toxicity. Our study suggests that CDIAL may serve as a novel chemical platform for the development of natural product-based insecticides and repellents for controlling mosquito vectors.

Different delivery mechanisms for insecticide-treated nets in rural Burkina Faso: a provider's perspective.

PubMed

Beiersmann, Claudia; De Allegri, Manuela; Tiendrebéogo, Justin; Yé, Maurice; Jahn, Albrecht; Mueller, Olaf

2010-12-04

Insecticide-treated nets (ITNs) have been confirmed to be a very effective tool in malaria control. Two different delivery strategies for roll-out of ITN programmes have been the focus of debate in the last years: free distribution and distribution through commercial marketing systems. They are now seen as complementary rather than opponent. Acceptance of these programmes by the community and involved providers is an important aspect influencing their sustainability. This paper looks at how providers perceived, understood and accepted two interventions involving two different delivery strategies (subsidized sales supported by social marketing and free distribution to pregnant women attending antenatal care services). The interventions took place in one province of north-western Burkina Faso in 2006 in the frame of a large randomized controlled ITN intervention study. For this descriptive qualitative study data were collected through focus group discussions and individual interviews. A total of four focus group discussions and eleven individual interviews have been conducted with the providers of the study interventions. The free distribution intervention was well accepted and perceived as running well. The health care staff had a positive and beneficial view of the intervention and did not feel overwhelmed by the additional workload. The social marketing intervention was also seen as positive by the rural shopkeepers. However, working in market economy, shopkeepers feared the risk of unsold ITNs, due to the low demand and capacity to pay for the product in the community. The combination of ITN free distribution and social marketing was in general well accepted by the different providers. However, low purchasing power of clients and the resulting financial insecurities of shopkeepers remain a challenge to ITN social marketing in rural SSA.

The impact of a hybrid social marketing intervention on inequities in access, ownership and use of insecticide-treated nets.

PubMed

Agha, Sohail; Van Rossem, Ronan; Stallworthy, Guy; Kusanthan, Thankian

2007-01-29

An ITN intervention was initiated in three predominantly rural districts of Eastern Province, Zambia, that lacked commercial distribution and communication infrastructures. Social marketing techniques were used for product and message development. Public sector clinics and village-based volunteers promoted and distributed subsidized ITNs priced at 2.5 dollars per net. A study was conducted to assess the effects of the intervention on inequities in knowledge, access, ownership and use of ITNs. A post-test only quasi-experimental study design was used to compare intervention and comparison districts. A total of 2,986 respondents were interviewed. Survey respondents were grouped into four socio-economic (SES) categories: low, medium-low, medium and high. Knowledge, access, ownership and use indicators are compared. Concentration index scores are calculated. Interactions between intervention status and SES help determine how different SES groups benefited from the intervention. Although overall use of nets remained relatively low, post-test data show that knowledge, access, ownership and use of mosquito nets was higher in intervention districts. A decline in SES inequity in access to nets occurred in intervention districts, resulting from a disproportionately greater increase in access among the low SES group. Declines in SES inequities in net ownership and use of nets were associated with the intervention. The largest increases in net ownership and use occurred among medium and high SES categories. Increasing access to nets among the poorest respondents in rural areas may not lead to increases in net use unless the price of nets is no longer a barrier to their purchase.

Effectiveness of post-campaign, door-to-door, hang-up, and communication interventions to increase long-lasting, insecticidal bed net utilization in Togo (2011–2012): a cluster randomized, control trial

PubMed Central

2014-01-01

Background It is well established that insecticide-treated bed nets (ITNs), in particular long-lasting, insecticidal nets (LLINs), can be used as one of the primary interventions for effective malaria control. A consistent gap between net ownership and use has been observed, indicating that factors exist that prevent an owned mosquito net from being used. One approach used in the context of LLIN campaigns is a post-distribution, door-to-door visit of households with educational messages and to physically assist with hang-up of nets. Methods A cluster randomized trial was conducted in the Plateaux Region of Togo to evaluate the effectiveness of different approaches to post-LLIN campaign home visits (number of visits and timing) by volunteers to enhance LLIN hang-up and utilization. Results It was found that, in general, households that received intervention visits, particularly the most recent intervention visit, had levels of use that were typically 5 to 10% higher than the control households, while access did not differ among control and intervention households. Eight months post-campaign, ITN use by all individuals, children under five years and women of reproductive age was 11.3 to 14.4 percentage points greater in the study arm that received all three intervention visits than in the control communities. In households that received one or two additional door-to-door visits, the majority of respondents indicated that the volunteer provided new information during the visit regarding the use and importance of ITNs despite having received previous multiple visits. Conclusions The impact of the interventions appears to have been primarily through the delivery and reinforcement of key behaviour-change communication (BCC) messages regarding the importance of using an ITN and its care. Regardless of whether the respondents in fact received new information or had forgotten earlier information, this suggests that regular visits from community agents are useful in

Determination of the predictive factors of long-lasting insecticide-treated net ownership and utilisation in the Bamenda Health District of Cameroon.

PubMed

Fokam, Eric B; Kindzeka, Germaine F; Ngimuh, Leonard; Dzi, Kevin T J; Wanji, Samuel

2017-03-16

Malaria is a serious health concern in Africa. In Cameroon, an endemic country where malaria remains a major public health problem, several control measures have been put in place among which the use of insecticide-treated bednets (LLINs/ITNs) is considered one of the core vector control strategies. However, the greatest challenges include ownership and utilisation by individuals and households. Factors such as age, marital status, gender, education and occupation of the household head, household size, knowledge of bednets, socioeconomic status, and environmental factors have been suggested to have an impact on bednet ownership and utilisation in different settings. The present study sought to determine bednet ownership and utilisation rates and to assess the impact of predictive factors on bednet ownership and use in the Bamenda Health District (BHD) of Cameroon. A cross-sectional study involving 384 households was conducted in six health areas in the BHD. A structured and semi-structured questionnaire was used to collect data on demographic and household characteristics as well as information on their bednet ownership and utilisation. Descriptive statistics, bivariate and multivariate logistic regression analysis were performed. Frequency of bednet ownership was relatively high (63.5%) with LLINs being most abundant (91.9%); the majority of households (87.7%) obtained their bednets during the 2011 free distribution campaign. Utilisation was relatively high (69.3%), with negligence (29.3%) and heat discomfort (26.7%) accounting most for non-usage of bednets. Children less than 5 years (63%) and pregnant women (60%) most often used these nets. Households headed by a married couple, those with older household heads, household with smaller size (5-12 persons), and knowledge of bednets (good knowledge) had positive impacts on bednet ownership (p < 0.05). The gender of the household head (males), their educational level, environmental conditions (presence of

Field trial on a novel control method for the dengue vector, Aedes aegypti by the systematic use of Olyset® Net and pyriproxyfen in Southern Vietnam

PubMed Central

2013-01-01

Background Jars, tanks, and drums provide favorable rearing/breeding sites for Aedes aegypti in Vietnam. However, the use of insecticides to control mosquitoes at such breeding sites has not been approved in Vietnam since they are also often sources of drinking water, making larval vector control difficult. Mosquito nets pre-treated with long-lasting insecticide treated nets (LLITNs) form an effective measure for malaria control. We examined changes in the abundance of immature Aedes aegypti to evaluate the efficacy of covering ceramic jars with lids comprising one type of LLITN, Olyset® Net, in inhibiting oviposition by adult females, and to evaluate the effect of treating other breeding containers, such as flower vases, inside and around the outside of houses with a slow-release pyriproxyfen formulation to kill pupae. Methods We selected 313 households for the trial and 363 households for the control in Tan Chanh, Long An province, Vietnam. In the trial area, Olyset® Net lids were used to cover five major types of water container (ceramic jars, cylindrical concrete tanks, other concrete tanks, plastic drums, and plastic buckets), while pyriproxyfen was used to treat flower vases and ant traps. We also monitored dengue virus transmission by measuring anti-dengue IgM and IgG levels in healthy residents in both control and trial areas to estimate the effectiveness of Olyset® Net at controlling the dengue vector, Aedes aegypti. Results The container-index and house-index for immature Ae. aegypti fell steeply one month after treatment in the trial area. Lids with Olyset® Net that fit container openings clearly seemed to reduce the presence of immature Ae. aegypti as the density of pupae decreased 1 month after treatment in the trial area. Pyriproxyfen was also effective at killing pupae in the water containers in the trial area. Although the dengue seroconversion rate was not influenced by Olyset® Net, it was lower in two-five year old children when compared to

Field trial on a novel control method for the dengue vector, Aedes aegypti by the systematic use of Olyset® Net and pyriproxyfen in Southern Vietnam.

PubMed

Tsunoda, Takashi; Kawada, Hitoshi; Huynh, Trang T T; Luu, Loan Le; Le, San Hoang; Tran, Huu Ngoc; Vu, Huong Thi Que; Le, Hieu Minh; Hasebe, Futoshi; Tsuzuki, Ataru; Takagi, Masahiro

2013-01-11

Jars, tanks, and drums provide favorable rearing/breeding sites for Aedes aegypti in Vietnam. However, the use of insecticides to control mosquitoes at such breeding sites has not been approved in Vietnam since they are also often sources of drinking water, making larval vector control difficult. Mosquito nets pre-treated with long-lasting insecticide treated nets (LLITNs) form an effective measure for malaria control. We examined changes in the abundance of immature Aedes aegypti to evaluate the efficacy of covering ceramic jars with lids comprising one type of LLITN, Olyset® Net, in inhibiting oviposition by adult females, and to evaluate the effect of treating other breeding containers, such as flower vases, inside and around the outside of houses with a slow-release pyriproxyfen formulation to kill pupae. We selected 313 households for the trial and 363 households for the control in Tan Chanh, Long An province, Vietnam. In the trial area, Olyset® Net lids were used to cover five major types of water container (ceramic jars, cylindrical concrete tanks, other concrete tanks, plastic drums, and plastic buckets), while pyriproxyfen was used to treat flower vases and ant traps. We also monitored dengue virus transmission by measuring anti-dengue IgM and IgG levels in healthy residents in both control and trial areas to estimate the effectiveness of Olyset® Net at controlling the dengue vector, Aedes aegypti. The container-index and house-index for immature Ae. aegypti fell steeply one month after treatment in the trial area. Lids with Olyset® Net that fit container openings clearly seemed to reduce the presence of immature Ae. aegypti as the density of pupae decreased 1 month after treatment in the trial area. Pyriproxyfen was also effective at killing pupae in the water containers in the trial area. Although the dengue seroconversion rate was not influenced by Olyset® Net, it was lower in two-five year old children when compared to older children and adults in

Theoretical impact of insecticide-impregnated school uniforms on dengue incidence in Thai children.

PubMed

Massad, Eduardo; Amaku, Marcos; Coutinho, Francisco Antonio Bezerra; Kittayapong, Pattamaporn; Wilder-Smith, Annelies

2013-03-28

Children carry the main burden of morbidity and mortality caused by dengue. Children spend a considerable amount of their day at school; hence strategies that reduce human-mosquito contact to protect against the day-biting habits of Aedes mosquitoes at schools, such as insecticide-impregnated uniforms, could be an effective prevention strategy. We used mathematical models to calculate the risk of dengue infection based on force of infection taking into account the estimated proportion of mosquito bites that occur in school and the proportion of school time that children wear the impregnated uniforms. The use of insecticide-impregnated uniforms has efficacy varying from around 6% in the most pessimistic estimations, to 55% in the most optimistic scenarios simulated. Reducing contact between mosquito bites and human hosts via insecticide-treated uniforms during school time is theoretically effective in reducing dengue incidence and may be a valuable additional tool for dengue control in school-aged children. The efficacy of this strategy, however, is dependent on the compliance of the target population in terms of proper and consistent wearing of uniforms and, perhaps more importantly, the proportion of bites inflicted by the Aedes population during school time.

Impact of Insecticide-Treated Net Ownership on All-Cause Child Mortality in Malawi, 2006-2010.

PubMed

Florey, Lia S; Bennett, Adam; Hershey, Christine L; Bhattarai, Achuyt; Nielsen, Carrie F; Ali, Doreen; Luhanga, Misheck; Taylor, Cameron; Eisele, Thomas P; Yé, Yazoume

2017-09-01

Insecticide-treated nets (ITNs) have been shown to be highly effective at reducing malaria morbidity and mortality in children. However, there are limited studies that assess the association between increasing ITN coverage and child mortality over time, at the national level, and under programmatic conditions. Two analytic approaches were used to examine this association: a retrospective cohort analysis of individual children and a district-level ecologic analysis. To evaluate the association between household ITN ownership and all-cause child mortality (ACCM) at the individual level, data from the 2010 Demographic and Health Survey (DHS) were modeled in a Cox proportional hazards framework while controlling for numerous environmental, household, and individual confounders through the use of exact matching. To evaluate population-level association between ITN ownership and ACCM between 2006 and 2010, program ITN distribution data and mortality data from the 2006 Multiple Indicator Cluster Survey and the 2010 DHS were aggregated at the district level and modeled using negative binomial regression. In the Cox model controlling for household, child and maternal health factors, children between 1 and 59 months in households owning an ITN had significantly lower mortality compared with those without an ITN (hazard ratio = 0.75, 95% confidence interval [CI] = 0.62-90). In the district-level model, higher ITN ownership was significantly associated with lower ACCM (incidence rate ratio = 0.77; 95% CI = 0.60-0.98). These findings suggest that increasing ITN ownership may have contributed to the decline in ACCM during 2006-2010 in Malawi and represent a novel use of district-level data from nationally representative surveys.

Modified mosquito landing boxes dispensing transfluthrin provide effective protection against Anopheles arabiensis mosquitoes under simulated outdoor conditions in a semi-field system.

PubMed

Andrés, Marta; Lorenz, Lena M; Mbeleya, Edgar; Moore, Sarah J

2015-06-24

Efforts to control malaria vectors have primarily focused on scaling-up of long-lasting insecticidal nets (LLINs) and indoor residual spraying. Although highly efficient against indoor-biting and indoor-resting vectors, these interventions have lower impact on outdoor-biting mosquitoes. Innovative vector control tools are required to prevent outdoor human-mosquito contacts. In this work, the potential of spatial repellents, delivered in an active system that requires minimal user compliance, to provide personal protection against exophagic mosquitoes active in the early evening was explored. A device previously used as an odour-baited lure and kill apparatus, the mosquito landing box (MLB), was modified to dispense the volatile synthetic pyrethroid, transfluthrin, as a spatial repellent. The MLB has an active odour-dispensing mechanism that uses a solar-powered fan and switches on at dusk to provide long duration dispensing of volatile compounds without the need for the user to remember to employ it. Two MLBs were located 5 m from a human volunteer to investigate the repellent effects of a transfluthrin 'bubble' created between the MLBs. Transfluthrin was emanated from polyester strips, hanging inside the MLB odour-dispensing unit. A fully randomized cross-over design was performed in a large, semi-field, screened cage to assess the effect of the repellent against laboratory-reared Anopheles arabiensis mosquitoes under ambient outdoor conditions. The knock-down capacity of the transfluthrin-treated strips was also evaluated at different time points up to 3 weeks after being impregnated to measure duration of efficacy. The protective transfluthrin bubble provided 68.9% protection against An. arabiensis bites under these simulated outdoor conditions. Volatile transfluthrin caused low mortality among mosquitoes in the semi-field system. Transfluthrin-treated strips continued to knock down mosquitoes in laboratory tests, 3 weeks after impregnation, although this effect

Biological Control of Mosquito Vectors: Past, Present, and Future

PubMed Central

Benelli, Giovanni; Jeffries, Claire L.; Walker, Thomas

2016-01-01

Mosquitoes represent the major arthropod vectors of human disease worldwide transmitting malaria, lymphatic filariasis, and arboviruses such as dengue virus and Zika virus. Unfortunately, no treatment (in the form of vaccines or drugs) is available for most of these diseases and vector control is still the main form of prevention. The limitations of traditional insecticide-based strategies, particularly the development of insecticide resistance, have resulted in significant efforts to develop alternative eco-friendly methods. Biocontrol strategies aim to be sustainable and target a range of different mosquito species to reduce the current reliance on insecticide-based mosquito control. In this review, we outline non-insecticide based strategies that have been implemented or are currently being tested. We also highlight the use of mosquito behavioural knowledge that can be exploited for control strategies. PMID:27706105

A Two-Locus Model of the Evolution of Insecticide Resistance to Inform and Optimise Public Health Insecticide Deployment Strategies

PubMed Central

2017-01-01

We develop a flexible, two-locus model for the spread of insecticide resistance applicable to mosquito species that transmit human diseases such as malaria. The model allows differential exposure of males and females, allows them to encounter high or low concentrations of insecticide, and allows selection pressures and dominance values to differ depending on the concentration of insecticide encountered. We demonstrate its application by investigating the relative merits of sequential use of insecticides versus their deployment as a mixture to minimise the spread of resistance. We recover previously published results as subsets of this model and conduct a sensitivity analysis over an extensive parameter space to identify what circumstances favour mixtures over sequences. Both strategies lasted more than 500 mosquito generations (or about 40 years) in 24% of runs, while in those runs where resistance had spread to high levels by 500 generations, 56% favoured sequential use and 44% favoured mixtures. Mixtures are favoured when insecticide effectiveness (their ability to kill homozygous susceptible mosquitoes) is high and exposure (the proportion of mosquitoes that encounter the insecticide) is low. If insecticides do not reliably kill homozygous sensitive genotypes, it is likely that sequential deployment will be a more robust strategy. Resistance to an insecticide always spreads slower if that insecticide is used in a mixture although this may be insufficient to outperform sequential use: for example, a mixture may last 5 years while the two insecticides deployed individually may last 3 and 4 years giving an overall ‘lifespan’ of 7 years for sequential use. We emphasise that this paper is primarily about designing and implementing a flexible modelling strategy to investigate the spread of insecticide resistance in vector populations and demonstrate how our model can identify vector control strategies most likely to minimise the spread of insecticide resistance

Insecticidal and repellent activities of insecticide-sucrose solutions to Culex pipiens molestus (Diptera: Culicidae) under laboratory and field conditions.

PubMed

Shin, Ehyun; Park, Chan; Ahn, Young-Joon; Lee, Dong-Kyu; Chang, Kyu-Sik

2011-06-01

Culex pipiens molestus Forskal has been reported as a dominant species in underground structures of urban areas in the Republic of Korea (ROK) during all seasons and becomes bothersome to humans in late autumn and winter. Most Cx. pipiens molestus in septic tanks are controlled in the ROK using larvicides such as Bt and IGR. However, there are a number of problems associated with larvicides, such as high cost and requirement for frequent use. In the present work, a new control method for Cx. pipiens molestus in septic tanks by using mixtures of sucrose solution with insecticides was investigated. The insecticidal and repellent activities of ten insecticides were evaluated for best control of Cx. pipiens molestus in septic tanks. Firstly, differences in susceptibilities to insecticides were evaluated in topical assays by forced direct contact bioassay and in a screened wire cage by free direct contact bioassay. The difference in insecticide susceptibility in the mosquitoes was the result of repellency by the insecticides. In three septic tanks, the density of Culex mosquitoes was sharply reduced by a deltamethrin-sucrose solution kit. The results demonstrated the potential for mosquito control by deltamethrin-sucrose solution, and the study offers basic information related to mosquito control in septic tanks. Copyright © 2011 Society of Chemical Industry.

Adaptation and evaluation of the bottle assay for monitoring insecticide resistance in disease vector mosquitoes in the Peruvian Amazon

PubMed Central

Zamora Perea, Elvira; Balta León, Rosario; Palomino Salcedo, Miriam; Brogdon, William G; Devine, Gregor J

2009-01-01

Background The purpose of this study was to establish whether the "bottle assay", a tool for monitoring insecticide resistance in mosquitoes, can complement and augment the capabilities of the established WHO assay, particularly in resource-poor, logistically challenging environments. Methods Laboratory reared Aedes aegypti and field collected Anopheles darlingi and Anopheles albimanus were used to assess the suitability of locally sourced solvents and formulated insecticides for use with the bottle assay. Using these adapted protocols, the ability of the bottle assay and the WHO assay to discriminate between deltamethrin-resistant Anopheles albimanus populations was compared. The diagnostic dose of deltamethrin that would identify resistance in currently susceptible populations of An. darlingi and Ae. aegypti was defined. The robustness of the bottle assay during a surveillance exercise in the Amazon was assessed. Results The bottle assay (using technical or formulated material) and the WHO assay were equally able to differentiate deltamethrin-resistant and susceptible An. albimanus populations. A diagnostic dose of 10 μg a.i./bottle was identified as the most sensitive discriminating dose for characterizing resistance in An. darlingi and Ae. aegypti. Treated bottles, prepared using locally sourced solvents and insecticide formulations, can be stored for > 14 days and used three times. Bottles can be stored and transported under local conditions and field-assays can be completed in a single evening. Conclusion The flexible and portable nature of the bottle assay and the ready availability of its components make it a potentially robust and useful tool for monitoring insecticide resistance and efficacy in remote areas that require minimal cost tools. PMID:19728871

[Efficacy of permethrin-impregnated Olyset Net mosquito nets in a zone with pyrethroid resistant vectors. I--Entomologic evaluation].

PubMed

Doannio, J M; Dossou-Yovo, J; Diarrassouba, S; Chauvancy, G; Darriet, F; Chandre, F; Henry, M C; Nzeyimana, I; Guillet, P; Carnevale, P

1999-01-01

The efficacy of permethrin-treated Olyset Net mosquito nets on malaria transmission and morbidity was studied in Kafine, a village located in the savanna region of the Cote d'Ivoire in Africa. After collecting sociodemographic, entomological, and parasitological data, bednets were distributed first in the southern half of the village and then in the whole village. Throughout the study period, mosquito specimens were captured on the skin of inhabitants at four points in the village between 6 PM and 6 AM both inside (but outside bednets) and outside houses. Prior to distribution of bednets, the mean biting rate (MBR) by Anopheles gambiae was 77.4 bites per man per night (b/m/n). The mean parturity rate (MPR) was 40.6 p. 100, the sporozootic index (SI) was 0.99 p. 100, and the mean entomological inoculation rate (MEIR) was 0.7 infectious bites per man per night (b+/m/n). Six months after distribution of bednets in the southern half of the village, MBR was 80.2 b/m/n, MPR was 32 p. 100, SI was 1.8 p. 100, and MEIR was 0.83 b+/m/n. After extending distribution to the whole village, data from November 1996 to July 1997 were as follows: MBR, 67.8 b/m/n; MPR, 20.1 p. 100; SI, 0.65 p. 100; and MEIR, 0.66 p. 100. From August 1977 to July 1998, data were as follows: MBR, 102.6 b/m/n; MPR, 26.2 p. 100; SI, 1.15 p. 100; and MEIR, 0.74 b+/m/n. Comparative analysis of these data showed that use of bednets had no effect on the bite or entomological inoculation rate. This is in agreement with the documented resistance of vectors in the study zone to permethrin. Despite the known stimulation/repulsion effect of permethrin, use of treated bednets had no real impact on transmission. This inefficacy could be related to the high prevalence (80 p. 100) of the Kdr gene (responsible for resistance) in the savanna form of Anopheles gambiae.

Long-lasting insecticide-treated house screens and targeted treatment of productive breeding-sites for dengue vector control in Acapulco, Mexico

PubMed Central

Che-Mendoza, Azael; Guillermo-May, Guillermo; Herrera-Bojórquez, Josué; Barrera-Pérez, Mario; Dzul-Manzanilla, Felipe; Gutierrez-Castro, Cipriano; Arredondo-Jiménez, Juan I.; Sánchez-Tejeda, Gustavo; Vazquez-Prokopec, Gonzalo; Ranson, Hilary; Lenhart, Audrey; Sommerfeld, Johannes; McCall, Philip J.; Kroeger, Axel; Manrique-Saide, Pablo

2015-01-01

Background Long-lasting insecticidal net screens (LLIS) fitted to domestic windows and doors in combination with targeted treatment (TT) of the most productive Aedes aegypti breeding sites were evaluated for their impact on dengue vector indices in a cluster-randomised trial in Mexico between 2011 and 2013. Methods Sequentially over 2 years, LLIS and TT were deployed in 10 treatment clusters (100 houses/cluster) and followed up over 24 months. Cross-sectional surveys quantified infestations of adult mosquitoes, immature stages at baseline (pre-intervention) and in four post-intervention samples at 6-monthly intervals. Identical surveys were carried out in 10 control clusters that received no treatment. Results LLIS clusters had significantly lower infestations compared to control clusters at 5 and 12 months after installation, as measured by adult (male and female) and pupal-based vector indices. After addition of TT to the intervention houses in intervention clusters, indices remained significantly lower in the treated clusters until 18 (immature and adult stage indices) and 24 months (adult indices only) post-intervention. Conclusions These safe, simple affordable vector control tools were well-accepted by study participants and are potentially suitable in many regions at risk from dengue worldwide. PMID:25604761

Impact of PermaNet 3.0 on entomological indices in an area of pyrethroid resistant Anopheles gambiae in south-western Nigeria

PubMed Central

2014-01-01

Background PermaNet® 3.0 is an insecticide synergist-combination long-lasting insecticidal net designed to have increased efficacy against malaria vectors with metabolic resistance, even when combined with kdr. The current study reports on the impact of this improved tool on entomological indices in an area with pyrethroid-resistant malaria vectors in Nigeria. Methods Baseline entomological indices across eight villages in Remo North LGA of Ogun State provided the basis for selection of three villages (Ilara, Irolu and Ijesa) for comparing the efficacy of PermaNet® 3.0 (PN3.0), PermaNet® 2.0 (PN2.0) and untreated polyester nets as a control (UTC). In each case, nets were distributed to cover all sleeping spaces and were evaluated for insecticidal activity on a 3-monthly basis. Collection of mosquitoes was conducted monthly via window traps and indoor resting catches. The arithmetic means of mosquito catches per house, entomological inoculation rates before and during the intervention were compared as well as three other outcome parameters: the mean mosquito blood feeding rate, mean mortality and mean parity rates. Results Anopheles gambiae s.l. was the main malaria vector in the three villages, accounting for >98% of the Anopheles population and found in appreciable numbers for 6–7 months. Deltamethrin, permethrin and lambdacyhalothrin resistance were confirmed at Ilara, Irolu and Ijesa. The kdr mutation was the sole resistance mechanism at Ilara, whereas kdr plus P450-based metabolic mechanisms were detected at Irolu and Ijesa. Bioassays repeated on domestically used PN 2.0 and PN 3.0 showed persistent optimal (100%) bio-efficacy for both net types after the 3rd, 6th, 9th and 12th month following net distribution. The use of PN 3.0 significantly reduced mosquito densities with a ‘mass killing’ effect inside houses. Households with PN 3.0 also showed reduced blood feeding as well as lower mosquito parity and sporozoite rates compared to the PN 2.0 and the

A geographic information system approach to evaluating the effects of the endangered species protection program on mosquito control.

PubMed

Spradling, S L; Olson, J K; Coulson, R N; Lovelady, C N

1998-06-01

The purpose of this study was to assess what impacts on organized mosquito control the implementation of an Endangered Species Protection Program for the Houston toad might have in Chambers and Harris counties, Texas. The study was also intended to demonstrate the value of using geographic information system (GIS) techniques and methodologies in making such assessments to those in mosquito control who are unfamiliar with GIS and its applications. Using the GIS, Geographical Analysis Support System (GRASS), databases were developed on the habitats and patterns of mosquito control insecticide usage occurring in Chambers and Harris counties. These databases were then employed by means of various utilities associated with GRASS and computer-supported, rule-based reasoning processes to create maps depicting the amount and locations of toad habitat and the areas treated annually with insecticides by districts in Chambers and Harris counties. This map information was then used via other GRASS utilities to identify and depict zones of overlap or coincidence between toad habitat and areas treated with insecticides for mosquito control in the 2 counties. As compared to existing maps for toad habitat, our resulting GIS-generated maps gave more precise, easy-to-use information that could be used to make decisions as to how to protect the toad in the zones of coincidence in each county without causing undue disruption to mosquito control activities in these zones.

Clinical malaria among pregnant women on combined insecticide treated nets (ITNs) and intermittent preventive treatment (IPTp) with sulphadoxine-pyrimethamine in Yaounde, Cameroon

PubMed Central

2014-01-01

Background Malaria remains a burden for pregnant women and the under 5. Intermittent preventive treatment of pregnant women (IPTp) for malaria with sulfadoxine – pyrimethamine (SP) has since replaced prophylaxis and legislation has been reinforced in the area of insecticide treated mosquito nets (ITNs) in Cameroon. Clinical malaria despite all these measures remains a problem. We compared the socio-obstetrical characteristics of women who developed clinical malaria and those who did not though in the same regimen. Methods A 5 – year nested cohort study (2007 – 2011 inclusive) at the tertiary level hospitals in Yaounde. Pregnant women who willingly accepted to participate in the study were enrolled at booking and three doses of SP were administered between 18 – 20 weeks of gestation, between 26–28 weeks and between 32 – 34 weeks. Those who developed clinical malaria were considered as cases and were compared for socio – obstetrical characteristics with those who did not. Venous blood was drawn from the women in both arms for parasite density estimation and identification and all the clinical cases were treated conventionally. Results Each arm had 166 cases and many women who developed clinical malaria were between 15 and 19 years (OR 5.5, 95% CI 3.9 – 5.3, p < 0.001). They were of low gravidity (OR 6.5, 95% CI 3.8 – 11.3, p < 0.001) as well as low parity (OR 4.6, 95% CI 2.7 – 7.9, p < 0.001). The cases were single women (OR 4.58, 95% CI 2.54 – 8.26, p < 0.001) and had attained only primary level of education (OR 4.6, 95% CI 2.8 – 7.9, p < 0.001). Gestational ages were between 20 to 30 weeks during clinical malaria (OR 6.8, 95% CI 4.1 – 11.7, p < 0.001). The time between the first and second dose of SP was longer than ten weeks in the cases (OR 5.5, 95% CI 3.2 – 9.3, p < 0.001) and parasite density was higher also among the cases (OR 6.9, 95% CI 5.9 – 12.1, p < 0.001). Conclusion Long spacing between the

Malaria Vector Control Still Matters despite Insecticide Resistance.

PubMed

Alout, Haoues; Labbé, Pierrick; Chandre, Fabrice; Cohuet, Anna

2017-08-01

Mosquito vectors' resistance to insecticides is usually considered a major threat to the recent progresses in malaria control. However, studies measuring the impact of interventions and insecticide resistance reveal inconsistencies when using entomological versus epidemiological indices. First, evaluation tests that do not reflect the susceptibility of mosquitoes when they are infectious may underestimate insecticide efficacy. Moreover, interactions between insecticide resistance and vectorial capacity reveal nonintuitive outcomes of interventions. Therefore, considering ecological interactions between vector, parasite, and environment highlights that the impact of insecticide resistance on the malaria burden is not straightforward and we suggest that vector control still matters despite insecticide resistance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biological Control of Mosquito Vectors: Past, Present, and Future.

PubMed

Benelli, Giovanni; Jeffries, Claire L; Walker, Thomas

2016-10-03

Mosquitoes represent the major arthropod vectors of human disease worldwide transmitting malaria, lymphatic filariasis, and arboviruses such as dengue virus and Zika virus. Unfortunately, no treatment (in the form of vaccines or drugs) is available for most of these diseases andvectorcontrolisstillthemainformofprevention. Thelimitationsoftraditionalinsecticide-based strategies, particularly the development of insecticide resistance, have resulted in significant efforts to develop alternative eco-friendly methods. Biocontrol strategies aim to be sustainable and target a range of different mosquito species to reduce the current reliance on insecticide-based mosquito control. In thisreview, weoutline non-insecticide basedstrategiesthat havebeenimplemented orare currently being tested. We also highlight the use of mosquito behavioural knowledge that can be exploited for control strategies.

How will the reduction of tariffs and taxes on insecticide- treated bednets affect household purchases?

PubMed

Simon, Jonathon L; Larson, Bruce A; Zusman, Alexander; Rosen, Sydney

2002-01-01

One of the steps called for in the fight against malaria is the removal of tariffs and taxes on insecticide-treated bednets (ITNs), netting materials, and insecticides, with a view to reducing the retail prices of ITNs and thus increasing utilization. In this paper we develop an approach for analysing the extent to which reform of tariff and tax policy can be expected to increase ITN purchases. We consider the following questions: (1). How much does the retail price of ITNs change if tariffs and taxes are reduced or eliminated? (2). How responsive is consumer demand to changes in the retail price of ITNs? Data on the price elasticity of demand for ITNs are very limited. Nevertheless, they suggest that ITN demand is not highly responsive to lower prices if household preferences are held constant. The reduction in retail prices associated with the removal of tariffs and taxes depends on the structure of the market in individual countries. In Nigeria, reducing the tariff on insecticides from 42% to zero and the tariff on netting materials from 40% to 5% is expected to increase ITN purchases by 9-27%, depending on the elasticity used. Country-specific information about market structure and cost conditions is needed if predictions are to be made as to how a specific policy change will affect ITN purchases.

How will the reduction of tariffs and taxes on insecticide- treated bednets affect household purchases?

PubMed Central

Simon, Jonathon L.; Larson, Bruce A.; Zusman, Alexander; Rosen, Sydney

2002-01-01

One of the steps called for in the fight against malaria is the removal of tariffs and taxes on insecticide-treated bednets (ITNs), netting materials, and insecticides, with a view to reducing the retail prices of ITNs and thus increasing utilization. In this paper we develop an approach for analysing the extent to which reform of tariff and tax policy can be expected to increase ITN purchases. We consider the following questions: (1). How much does the retail price of ITNs change if tariffs and taxes are reduced or eliminated? (2). How responsive is consumer demand to changes in the retail price of ITNs? Data on the price elasticity of demand for ITNs are very limited. Nevertheless, they suggest that ITN demand is not highly responsive to lower prices if household preferences are held constant. The reduction in retail prices associated with the removal of tariffs and taxes depends on the structure of the market in individual countries. In Nigeria, reducing the tariff on insecticides from 42% to zero and the tariff on netting materials from 40% to 5% is expected to increase ITN purchases by 9-27%, depending on the elasticity used. Country-specific information about market structure and cost conditions is needed if predictions are to be made as to how a specific policy change will affect ITN purchases. PMID:12481212

Effectiveness and equity of the Tanzania National Voucher Scheme for mosquito nets over 10 years of implementation.

PubMed

Kramer, Karen; Mandike, Renata; Nathan, Rose; Mohamed, Ally; Lynch, Matthew; Brown, Nick; Mnzava, Ally; Rimisho, Wilhelmina; Lengeler, Christian

2017-06-15

The Tanzania National Voucher Scheme (TNVS) was a public private partnership managed by the Ministry of Health that provided pregnant women and infants with highly subsidized (long-lasting) insecticide-treated nets between 2004 and 2014. It was implemented in the context of the National Insecticide Treated Nets (NATNETS) Programme and was the main keep up strategy for vulnerable populations. The programme design was adjusted considerably over time to incorporate new evidence, shifting public health policies, and changing donor priorities. Three TNVS models can be distinguished: (1) the fixed discount; (2) the fixed top-up; (3) the hybrid voucher model. The changes improved equity and effectiveness, but also had a profound effect on how the programme was managed and implemented. The TNVS reached the majority of beneficiaries with vouchers, and significantly increased household ownership and use of LLINs. While two mass distribution campaigns implemented between 2009 and 2011 achieved universal coverage and equity, the TNVS ensured continuous protection of the vulnerable populations before, during and after the campaigns. The TNVS stimulated and maintained a large national retail network which managed the LLIN supply chain. The effectiveness of the TNVS was a function of several interdependent factors, including the supply chain of vouchers through the public health system; the supply chain of nets in the commercial sector; the demand for nets from voucher recipients; management and risk mitigation measures; and the influence of global and donor objectives. The TNVS was a highly innovative and globally influential programme, which stimulated the thinking around effectively and equitably distributing ITNs, and contributed directly to the evolution of global policy. It was a fundamental component of the NATNETS programme which protected a malaria-vulnerable population for over a decade.

A stitch in time: a cross-sectional survey looking at long lasting insecticide-treated bed net ownership, utilization and attrition in SNNPR, Ethiopia.

PubMed

Batisso, Esey; Habte, Tedila; Tesfaye, Gezahegn; Getachew, Dawit; Tekalegne, Agonafer; Kilian, Albert; Mpeka, Betty; Lynch, Caroline

2012-06-07

Since 2002/03, an estimated 4.7 million nets have been distributed in the Southern Nations, Nationalities and Peoples Region (SNNPR) among an at risk population of approximately 10 million people. Evidence from the region suggests that large-scale net ownership rapidly increased over a relatively short period of time. However, little is known about how coverage is being maintained given that the last mass distribution was in 2006/2007. This study sought to determine the status of current net ownership, utilization and rate of long lasting insecticide-treated nets (LLIN) loss in the previous three years in the context of planning for future net distribution to try to achieve sustainable universal coverage. A total of 750 household respondents were interviewed across malarious, rural kebeles of SNNPR. Households were randomly selected following a two-stage cluster sampling design where kebeles were defined as clusters. Kebeles were chosen using proportional population sampling (PPS), and 25 households within 30 kebeles randomly chosen. Approximately 67.5% (95%CI: 64.1-70.8) of households currently owned at least one net. An estimated 31.0% (95%CI 27.9-34.4) of all nets owned in the previous three years had been discarded by owners, the majority of whom considered the nets too torn, old or dirty (79.9%: 95%CI 75.8-84.0). Households reported that one-third of nets (33.7%) were less than one year old when they were discarded. The majority (58.8%) of currently owned nets had 'good' structural integrity according to a proportionate Hole Index. Nearly two-thirds of households (60.6%) reported using their nets the previous night. The overriding reason for not using nets was that they were too torn (45.7%, 95% CI 39.1-50.7). Yet, few households are making repairs to their nets (3.7%, 95% CI: 2.4-5.1). Results suggest that the life span of nets may be shorter than previously thought, with little maintenance by their owners. With the global move towards malaria elimination it

Distributing insecticide-treated bednets during measles vaccination: a low-cost means of achieving high and equitable coverage.

PubMed Central

Grabowsky, Mark; Nobiya, Theresa; Ahun, Mercy; Donna, Rose; Lengor, Miata; Zimmerman, Drake; Ladd, Holly; Hoekstra, Edward; Bello, Aliu; Baffoe-Wilmot, Aba; Amofah, George

2005-01-01

OBJECTIVE: To achieve high and equitable coverage of insecticide-treated bednets by integrating their distribution into a measles vaccination campaign. METHODS: In December 2002 in the Lawra district in Ghana, a measles vaccination campaign lasting 1 week targeted all children aged 9 months-15 years. Families with one or more children less than five years old were targeted to receive a free insecticide-treated bednet. The Ghana Health Service, with support from the Ghana Red Cross and UNICEF, provided logistical support, volunteer workers and social mobilization during the campaign. Volunteers visited homes to inform caregivers about the campaign and encourage them to participate. We assessed pre-campaign coverage of bednets by interviewing caregivers leaving vaccination and distribution sites. Five months after distribution, a two-stage cluster survey using population-proportional sampling assessed bednet coverage, retention and use. Both the pre-campaign and post-campaign survey assessed household wealth using an asset inventory. FINDINGS: At the campaign exit interview 636/776 (82.0%) caregivers reported that they had received a home visit by a Red Cross volunteer before the campaign and that 32/776 (4.1%) of the youngest children in each household who were less than 5 years of age slept under an insecticide-treated bednet. Five months after distribution caregivers reported that 204/219 (93.2%) of children aged 9 months to 5 years had been vaccinated during the campaign; 234/248 (94.4%) of households were observed to have an insecticide-treated bednet; and 170/249 (68.3%) were observed to have a net hung over a bed. Altogether 222/248 (89.5%) caregivers reported receiving at least one insecticide-treated bednet during the campaign, and 153/254 (60.2%) said that on the previous night their youngest child had slept under a bednet received during the campaign. For households in the poorest quintile, post-campaign coverage of insecticide-treated bednets was 10 times

High-Throughput Mosquito and Fly Bioassay System for Natural and Artificial Substrates Treated with Residual Insecticides

DTIC Science & Technology

2013-03-01

1989. Evaluation of the cotton fabric model for screening topical mosquito repellents . J Am Mosq Control Assoc 5:73–76. WHO [World Health Organization...institutions, research libraries, and research funders in the common goal of maximizing access to critical research. High-Throughput Mosquito and Fly Bioassay...A. Allan , Todd W. Walker , Christopher J. Geden , Jerome A. Hogsette , and Kenneth J. Linthicum Source: Journal of the American Mosquito Control

Ownership and usage of insecticide-treated bed nets after free distribution via a voucher system in two provinces of Mozambique.

PubMed

Macedo de Oliveira, Alexandre; Wolkon, Adam; Krishnamurthy, Ramesh; Erskine, Marcy; Crenshaw, Dana P; Roberts, Jacquelin; Saúte, Francisco

2010-08-04

Insecticide-treated bed nets (ITNs) are an efficacious intervention for malaria prevention. During a national immunization campaign in Mozambique, vouchers, which were to be redeemed at a later date for free ITNs, were distributed in Manica and Sofala provinces. A survey to evaluate ITN ownership and usage post-campaign was conducted. Four districts in each province and four enumeration areas (EAs) in each district were selected using probability proportional to size. Within each EA, 32 households (HHs) were selected using a simple random sample. Interviews to assess ownership and usage were conducted in each of the selected HHs using personal digital assistants. Valid interviews were completed for 947 (92.5%) (440 in Manica and 507 in Sofala) of the 1,024 selected HHs. Among participating HHs, 65.0% in Manica and 63.1% in Sofala reported that at least one child under five years of age slept in the house the previous night. HH ownership of at least one bed net of any kind was 20.6% (95% confidence interval [CI]: 7.9%-43.6%) and 35.6% (95% CI: 27.8%-44.3%) pre-campaign; and 55.1% (95% CI: 43.6%-66.1%) and 59.6 (95% CI: 42.4%-74.7%) post-campaign in Manica and Sofala, respectively. Post-campaign HH ownership of at least one ITN was 50.2% (95% CI: 41.8%-58.5%) for both provinces combined. In addition, 60.3% (95% CI: 50.6%-69.2%) of children under five years of age slept under an ITN the previous night. This ITN distribution increased bed net ownership and usage rates. Integration of ITN distribution with immunization campaigns presents an opportunity for reaching malaria control targets and should continue to be considered.

Rapid Scale-Up of Long-Lasting Insecticide-Treated Bed Nets through Integration into the National Immunization Program during Child Health Week in Togo, 2004

PubMed Central

Wolkon, Adam; Vanden Eng, Jodi L.; Morgah, Kodjo; Eliades, M. James; Thwing, Julie; Terlouw, Dianne J.; Takpa, Vincent; Dare, Aboudou; Sodahlon, Yao K.; Doumanou, Yao; Hightower, Allen W.; Lama, Marcel; Thawani, Neeta; Slutsker, Laurence; Hawley, William A.

2010-01-01

In December 2004, Togo was the first country to conduct a nationwide free insecticide-treated net (ITN) distribution as part of its National Integrated Child Health Campaign. Community-based cross-sectional surveys were conducted one and nine months post-campaign as part of a multidisciplinary evaluation of the nationwide distribution of ITNs to children 9–59 months of age to evaluate ITN ownership, equity, and use. Our results demonstrated that at one month post-campaign, 93.1% of all eligible children received an ITN. Household ITN ownership and equity increased significantly post-campaign. Nine months post-campaign, 78.6% of households with a child eligible to participate in the campaign retained at least one campaign net. Use by eligible children was 43.5% at one month post-campaign (during the dry season) and 52.9% at nine months post-campaign (during the rainy season). Household ownership of at least one ITN increased from 8.0% pre-campaign to 62.5% one month post-campaign. Together, these findings demonstrate that in this setting, increased household ITN ownership, equity, and retention can be achieved on a national scale through free ITN distribution during an integrated campaign. PMID:21036829

Theoretical impact of insecticide-impregnated school uniforms on dengue incidence in Thai children

PubMed Central

Massad, Eduardo; Amaku, Marcos; Coutinho, Francisco Antonio Bezerra; Kittayapong, Pattamaporn; Wilder-Smith, Annelies

2013-01-01

Background Children carry the main burden of morbidity and mortality caused by dengue. Children spend a considerable amount of their day at school; hence strategies that reduce human–mosquito contact to protect against the day-biting habits of Aedes mosquitoes at schools, such as insecticide-impregnated uniforms, could be an effective prevention strategy. Methodology We used mathematical models to calculate the risk of dengue infection based on force of infection taking into account the estimated proportion of mosquito bites that occur in school and the proportion of school time that children wear the impregnated uniforms. Principal findings The use of insecticide-impregnated uniforms has efficacy varying from around 6% in the most pessimistic estimations, to 55% in the most optimistic scenarios simulated. Conclusions Reducing contact between mosquito bites and human hosts via insecticide-treated uniforms during school time is theoretically effective in reducing dengue incidence and may be a valuable additional tool for dengue control in school-aged children. The efficacy of this strategy, however, is dependent on the compliance of the target population in terms of proper and consistent wearing of uniforms and, perhaps more importantly, the proportion of bites inflicted by the Aedes population during school time. PMID:23541045

A pre-intervention study of malaria vector abundance in Rio Muni, Equatorial Guinea: Their role in malaria transmission and the incidence of insecticide resistance alleles

PubMed Central

Ridl, Frances C; Bass, Chris; Torrez, Miguel; Govender, Dayanandan; Ramdeen, Varsha; Yellot, Lee; Edu, Amado Edjang; Schwabe, Christopher; Mohloai, Peter; Maharaj, Rajendra; Kleinschmidt, Immo

2008-01-01

Background Following the success of the malaria control intervention on the island of Bioko, malaria control by the use of indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLITN) was extended to Rio Muni, on the mainland part of Equatorial Guinea. This manuscript reports on the malaria vectors present and the incidence of insecticide resistant alleles prior to the onset of the programme. Methods Anopheles mosquitoes were captured daily using window traps at 30 sentinel sites in Rio Muni, from December 2006 to July 2007. The mosquitoes were identified to species and their sporozoite rates, knockdown resistance (kdr) and acetylcholinesterase (AChE) sensitivity measured, to define the role of vector species in malaria transmission and their potential susceptibility to insecticides. Results A total of 6,162 Anopheles mosquitoes were collected of which 4,808 were morphologically identified as Anopheles gambiae s.l., 120 Anopheles funestus, 1,069 Anopheles moucheti, and 165 Anopheles nili s.l.. Both M and S molecular forms of Anopheles gambiae s.s. and Anopheles melas were identified. Anopheles ovengensis and Anopheles carnevalei were the only two members of the An. nili group to be identified. Using the species-specific sporozoite rates and the average number of mosquitoes per night, the number of infective mosquitoes per trap per 100 nights for each species complex was calculated as a measure of transmission risk. Both kdr-w and kdr-e alleles were present in the S-form of An. gambiae s.s. (59% and 19% respectively) and at much lower frequencies in the M-form (9.7% and 1.8% respectively). The kdr-w and kdr-e alleles co-occurred in 103 S-form and 1 M-form specimens. No insensitive AChE was detected. Conclusion Anopheles gambiae s.s, a member of the Anopheles gambiae complex was shown to be the major vector in Rio Muni with the other three groups playing a relatively minor role in transmission. The demonstration of a high frequency of kdr alleles

Efficacy of Two Common Methods of Application of Residual Insecticide for Controlling the Asian Tiger Mosquito, Aedes albopictus (Skuse), in Urban Areas.

PubMed

Marini, Lorenzo; Baseggio, Alberto; Drago, Andrea; Martini, Simone; Manella, Paolo; Romi, Roberto; Mazzon, Luca

2015-01-01

After its first introduction in the 1980's the Asian tiger mosquito, Aedes albopictus (Skuse), has spread throughout Southern Europe. Ae. albopictus is considered an epidemiologically important vector for the transmission of many viral pathogens such as the yellow fever virus, dengue fever and Chikungunya fever, as well as several filarial nematodes such as Dirofilaria immitis or D. repens. It is therefore crucial to develop measures to reduce the risks of disease transmission by controlling the vector populations. The aim of the study was to compare the efficacy of two application techniques (mist vs. stretcher sprayer) and two insecticides (Etox based on the nonester pyrethroid Etofenprox vs. Microsin based on the pyrethroid type II Cypermetrin) in controlling adult tiger mosquito populations in highly populated areas. To test the effect of the two treatments pre- and post-treatment human landing rate counts were conducted for two years. After one day from the treatment we observed a 100% population decrease in mosquito abundance with both application methods and both insecticides. However, seven and 14 days after the application the stretcher sprayer showed larger population reductions than the mist sprayer. No effect of insecticide type after one day and 14 days was found, while Etox caused slightly higher population reduction than Microsin after seven days. Emergency measures to locally reduce the vector populations should adopt adulticide treatments using stretcher sprayers. However, more research is still needed to evaluate the potential negative effects of adulticide applications on non-target organisms.

UV light and urban pollution: bad cocktail for mosquitoes?

PubMed

Tetreau, Guillaume; Chandor-Proust, Alexia; Faucon, Frédéric; Stalinski, Renaud; Akhouayri, Idir; Prud'homme, Sophie M; Régent-Kloeckner, Myriam; Raveton, Muriel; Reynaud, Stéphane

2014-01-01

Mosquito breeding sites consist of water pools, which can either be large open areas or highly covered ponds with vegetation, thus with different light exposures combined with the presence in water of xenobiotics including polycyclic aromatic hydrocarbons (PAHs) generated by urban pollution. UV light and PAHs are abiotic factors known to both affect the mosquito insecticide resistance status. Nonetheless, their potential combined effects on the mosquito physiology have never been investigated. The present article aims at describing the effects of UV exposure alongside water contamination with two major PAH pollutants (fluoranthene and benzo[a]pyrene) on a laboratory population of the yellow fever mosquito Aedes aegypti. To evaluate the effects of PAH exposure and low energetic UV (UV-A) irradiation on mosquitoes, different parameters were measured including: (1) The PAH localization and its impact on cell mortality by fluorescent microscopy; (2) The detoxification capacities (cytochrome P450, glutathione-S-transferase, esterase); (3) The responses to oxidative stress (Reactive Oxygen Species-ROS) and (4) The tolerance of mosquito larvae to a bioinsecticide (Bacillus thuringiensis subsp. israelensis-Bti) and to five chemical insecticides (DDT, imidacloprid, permethrin, propoxur and temephos). Contrasting effects regarding mosquito cell mortality, detoxification and oxidative stress were observed as being dependent on the pollutant considered, despite the fact that the two PAHs belong to the same family. Moreover, UV is able to modify pollutant effects on mosquitoes, including tolerance to three insecticides (imidacloprid, propoxur and temephos), cell damage and response to oxidative stress. Taken together, our results suggest that UV and pollution, individually or in combination, are abiotic parameters that can affect the physiology and insecticide tolerance of mosquitoes; but the complexity of their direct effect and of their interaction will require further

Household use of insecticide consumer products in a dengue-endemic area in México.

PubMed

Loroño-Pino, María Alba; Chan-Dzul, Yamili N; Zapata-Gil, Rocio; Carrillo-Solís, Claudia; Uitz-Mena, Ana; García-Rejón, Julián E; Keefe, Thomas J; Beaty, Barry J; Eisen, Lars

2014-10-01

To evaluate the household use of insecticide consumer products to kill mosquitoes and other insect pests, as well as the expenditures for using these products, in a dengue-endemic area of México. A questionnaire was administered to 441 households in Mérida City and other communities in Yucatán to assess household use of insecticide consumer products. A total of 86.6% of surveyed households took action to kill insect pests with consumer products. The most commonly used product types were insecticide aerosol spray cans (73.6%), electric plug-in insecticide emitters (37.4%) and mosquito coils (28.3%). Mosquitoes were targeted by 89.7% of households using insecticide aerosol spray cans and >99% of households using electric plug-in insecticide emitters or mosquito coils. Products were used daily or every 2 days in most of the households for insecticide aerosol spray cans (61.4%), electric plug-in insecticide emitters (76.2%) and mosquito coils (82.1%). For all products used to kill insect pests, the median annual estimated expenditure per household that took action was 408 Mexican pesos ($MXN), which corresponded to approximately 31 $US. These numbers are suggestive of an annual market in excess of 75 million $MXN (>5.7 million $US) for Mérida City alone. Mosquitoes threaten human health and are major nuisances in homes in the study area in México. Households were found to have taken vigorous action to kill mosquitoes and other insect pests and spent substantial amounts of money on insecticide consumer products. © 2014 John Wiley & Sons Ltd.

Free distribution of insecticidal bed nets improves possession and preferential use by households and is equitable: findings from two cross-sectional surveys in thirteen malaria endemic districts of Bangladesh.

PubMed

Ahmed, Syed M; Hossain, Shamim; Kabir, Mohammad M; Roy, Sanjit

2011-12-13

BRAC, an indigenous non-governmental development organization (NGO), has been implementing a programme to prevent and control malaria in the 13 malaria-endemic districts of Bangladesh since 2007. One of the critical preventive interventions is the distribution of insecticidal bed nets (long-lasting insecticide-treated nets, LLINs and insecticide-treated ordinary nets, ITNs) to the community free of cost. This study aimed to assess progress in the possession, preferential use, and knowledge on use of the LLIN/ITNs including the programme's avowed pro-poor inclination one and three and half years after intervention began. A convenient sampling strategy based on malaria endemicity in the districts was adopted. First, thirty upazila (sub-district, with a population around 250,000)s were selected at random, with high prevalent districts contributing more upazilas; second, from each upazila, one (2008) to two (2011) villages (covered by insecticidal bed net distribution programme) were selected. From each village, households that had either one under-five child and/or a pregnant woman were included in the survey, one household being included only once. Data were collected using a pre-tested structured questionnaire. In all, 3,760 households in 2008 and 7,895 households in 2011 were surveyed for collecting relevant information. Proportion of households with at least one LLIN, and at least one LLIN/ITN increased (22-59 to 62-67% and 22-64% to 74-76% respectively) over time, including increase in the mean number of LLIN/ITNs per household (≤ 1 to 1 +). The programme achieved > 80% coverage in sleeping under an LLIN/ITN in the case of under-five children and pregnant women, especially in the high-endemic districts. Knowledge regarding critical time of hanging the net also increased over time (7-22 to 44-54%), but remained low. The pro-poor inclination of the programme is reflected in the status of relevant indicators according to self-rated poverty status of the households

An examination of the effect of aerosolized Permanone insecticide on zebra finch susceptibility to West Nile virus.

PubMed

Jankowski, Mark D; Moore, Murray E; Hofmeister, Erik K

2017-12-01

West Nile virus (WNV) is maintained cryptically primarily in avian (passerine) populations, where it is transmitted by Culex spp. mosquitoes. Mosquito-control measures currently include physical activities to reduce mosquito-breeding sites and the application of mosquito larvicides or aerosolized insecticides to kill adults (adulticides) when arboviral diseases such as WNV or Zika virus are detected in mosquito populations. Organochlorine, organophosphorus, carbamate, and pyrethroid insecticides are often used. Previous work suggests an effect of pyrethroids on the immune system in a variety of vertebrates. We examined the effects of exposure to aerosolized Permanone® 30:30 insecticide (permethrin and piperonyl butoxide in soy oil vehicle) at approximately 10 3 to 10 6 times potential environmental concentrations on the response of captive zebra finches (Taeniopygia guttata) to experimental challenge with WNV. Compared to vehicle control birds, WNV outcome was unchanged (65% of birds produced a viremia) in the "low" exposure (9.52 ± 3.13 mg/m 3 standard deviation [SD] permethrin) group but reduced in the "high" exposure (mean 376.5 ± 27.9 mg/m 3 SD permethrin) group (30% were viremic; p < 0.05). After clearing WNV infection, birds treated with Permanone regained less body mass than vehicle-treated birds (p < 0.001). The present study suggests that exposure to aerosolized Permanone insecticide at levels exceeding typical application rates has the potential to not change or to mildly enhance a bird's resistance to WNV. Environ Toxicol Chem 2017;36:3376-3386. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Determinants of household demand for bed nets in a rural area of southern Mozambique

PubMed Central

Chase, Claire; Sicuri, Elisa; Sacoor, Charfudin; Nhalungo, Delino; Nhacolo, Ariel; Alonso, Pedro L; Menéndez, Clara

2009-01-01

Background A key to making insecticide-treated nets (ITNs) a long-term, sustainable solution to the spread of malaria is understanding what drives their purchase and use. Few studies have analysed the determinants of demand for bed nets for malaria prevention at the household level, and in particular, how demand for nets compares with demand for other mosquito prevention methods. Methods This study uses a household survey to assess the determinants of demand for bed nets in an area of endemic malaria transmission in rural, southern Mozambique. The study looks at willingness to pay (WTP) for bed nets, net ownership, usage, and past purchase behaviour, alongside expenditure and frequency of use of alternate methods for malaria prevention. Results While overall net ownership in the sample is low, the evidence fails to suggest that poorer households are less likely to own bed nets, when controlling for covariates, nor does the likelihood of receiving a free net depend on socioeconomic status (SES). Formal schooling and market knowledge seem to indicate higher average willingness to pay, while use of alternate methods for malaria prevention, and receipt of Indoor Residual Spraying (IRS) are found to decrease demand for bed nets. Conclusion For long-term sustainability of ITNs to be realized, results suggest that either full or partial subsidies may be necessary in some contexts to encourage households to obtain and use nets. Given the possible substitution effects of combined malaria control interventions, and the danger of not taking into consideration household preferences for malaria prevention, successful malaria control campaigns should invest a portion of their funds towards educating recipients of IRS and users of other preventive methods on the importance of net use even in the absence of mosquitoes. PMID:19527505

Use of insecticide-treated school uniforms for prevention of dengue in schoolchildren: a cost-effectiveness analysis.

PubMed

Tozan, Yesim; Ratanawong, Pitcha; Louis, Valérie R; Kittayapong, Pattamaporn; Wilder-Smith, Annelies

2014-01-01

Dengue-related illness is a leading cause of hospitalization and death, particularly among children. Practical, acceptable and affordable measures are urgently needed to protect this age group. Schools where children spend most of their day is proposed as an ideal setting to implement preventive strategies against day-biting Aedes mosquitoes. The use of insecticide-treated school uniforms is a promising strategy currently under investigation. Using a decision-analytic model, we evaluated the cost-effectiveness of the use of insecticide-treated school uniforms for prevention of dengue, compared with a "do-nothing" alternative, in schoolchildren from the societal perspective. We explored how the potential economic value of the intervention varied under various scenarios of intervention effectiveness and cost, as well as dengue infection risk in school-aged children, using data specific to Thailand. At an average dengue incidence rate of 5.8% per year in school-aged children, the intervention was cost-effective (ICER≤$16,440) in a variety of scenarios when the intervention cost per child was $5.3 or less and the intervention effectiveness was 50% or higher. In fact, the intervention was cost saving (ICER<0) in all scenarios in which the intervention cost per child was $2.9 or less per year and the intervention effectiveness was 50% or higher. The results suggested that this intervention would be of no interest to Thai policy makers when the intervention cost per child was $10.6 or higher per year regardless of intervention effectiveness (ICER>$16,440). Our results present the potential economic value of the use of insecticide-treated uniforms for prevention of dengue in schoolchildren in a typical dengue endemic setting and highlight the urgent need for additional research on this intervention.

Use of Insecticide-Treated School Uniforms for Prevention of Dengue in Schoolchildren: A Cost-Effectiveness Analysis

PubMed Central

Tozan, Yesim; Ratanawong, Pitcha; Louis, Valérie R.; Kittayapong, Pattamaporn; Wilder-Smith, Annelies

2014-01-01

Background Dengue-related illness is a leading cause of hospitalization and death, particularly among children. Practical, acceptable and affordable measures are urgently needed to protect this age group. Schools where children spend most of their day is proposed as an ideal setting to implement preventive strategies against day-biting Aedes mosquitoes. The use of insecticide-treated school uniforms is a promising strategy currently under investigation. Methods Using a decision-analytic model, we evaluated the cost-effectiveness of the use of insecticide-treated school uniforms for prevention of dengue, compared with a “do-nothing” alternative, in schoolchildren from the societal perspective. We explored how the potential economic value of the intervention varied under various scenarios of intervention effectiveness and cost, as well as dengue infection risk in school-aged children, using data specific to Thailand. Results At an average dengue incidence rate of 5.8% per year in school-aged children, the intervention was cost-effective (ICER≤$16,440) in a variety of scenarios when the intervention cost per child was $5.3 or less and the intervention effectiveness was 50% or higher. In fact, the intervention was cost saving (ICER<0) in all scenarios in which the intervention cost per child was $2.9 or less per year and the intervention effectiveness was 50% or higher. The results suggested that this intervention would be of no interest to Thai policy makers when the intervention cost per child was $10.6 or higher per year regardless of intervention effectiveness (ICER>$16,440). Conclusions Our results present the potential economic value of the use of insecticide-treated uniforms for prevention of dengue in schoolchildren in a typical dengue endemic setting and highlight the urgent need for additional research on this intervention. PMID:25247556

Informing new or improved vector control tools for reducing the malaria burden in Tanzania: a qualitative exploration of perceptions of mosquitoes and methods for their control among the residents of Dar es Salaam.

PubMed

Makungu, Christina; Stephen, Stephania; Kumburu, Salome; Govella, Nicodem J; Dongus, Stefan; Hildon, Zoe Jane-Lara; Killeen, Gerry F; Jones, Caroline

2017-10-11

The effectiveness of malaria prevention with long-lasting insecticidal nets and indoor residual spraying is limited by emerging insecticide resistance, evasive mosquito behaviours that include outdoor biting, sub-optimal implementation and inappropriate use. New vector control interventions are required and their potential effectiveness will be enhanced if existing household perceptions and practices are integrated into intervention design. This qualitative descriptive study used focus groups discussions, in-depth interviews and photovoice methods to explore mosquito control perceptions and practices among residents in four study sites in Dar es Salaam, Tanzania. Mosquitoes were perceived as a growing problem, directly attributed to widespread environmental deterioration and lack of effective mosquito control interventions. Malaria and nuisance biting were perceived as the main problem caused by mosquitoes. Breeding sites were clearly distinguished from resting sites but residents did not differentiate between habitats producing malaria vector mosquitoes and others producing mostly nuisance mosquitoes. The most frequently mentioned protection methods in the wealthiest locations were bed nets, aerosol insecticide sprays, window screens, and fumigation, while bed nets were most frequently mentioned and described as 'part of the culture' in the least wealthy locations. Mosquito-proofed housing was consistently viewed as desirable, but considered unaffordable outside wealthiest locations. Slapping and covering up with clothing were most commonly used to prevent biting outdoors. Despite their utility outdoors, topical repellents applied to the skin were considered expensive, and viewed with suspicion due to perceived side effects. Improving the local environment was the preferred method for preventing outdoor biting. Affordability, effectiveness, availability, practicality, as well as social influences, such as government recommendations, socialization and

Combination of indoor residual spraying with long-lasting insecticide-treated nets for malaria control in Zambezia, Mozambique: a cluster randomised trial and cost-effectiveness study protocol

PubMed Central

Alonso, Sergi; Zulliger, Rose; Wagman, Joe; Saifodine, Abuchahama; Candrinho, Baltazar; Macete, Eusébio; Brew, Joe; Fornadel, Christen; Kassim, Hidayat; Loch, Lourdes; Sacoor, Charfudin; Varela, Kenyssony; Carty, Cara L; Robertson, Molly; Saute, Francisco

2018-01-01

Background Most of the reduction in malaria prevalence seen in Africa since 2000 has been attributed to vector control interventions. Yet increases in the distribution and intensity of insecticide resistance and higher costs of newer insecticides pose a challenge to sustaining these gains. Thus, endemic countries face challenging decisions regarding the choice of vector control interventions. Methods A cluster randomised trial is being carried out in Mopeia District in the Zambezia Province of Mozambique, where malaria prevalence in children under 5 is high (68% in 2015), despite continuous and campaign distribution of long-lasting insecticide-treated nets (LLINs). Study arm 1 will continue to use the standard, LLIN-based National Malaria Control Programme vector control strategy (LLINs only), while study arm 2 will receive indoor residual spraying (IRS) once a year for 2 years with a microencapsulated formulation of pirimiphos-methyl (Actellic 300 CS), in addition to the standard LLIN strategy (LLINs+IRS). Prior to the 2016 IRS implementation (the first of two IRS campaigns in this study), 146 clusters were defined and stratified per number of households. Clusters were then randomised 1:1 into the two study arms. The public health impact and cost-effectiveness of IRS intervention will be evaluated over 2 years using multiple methods: (1) monthly active malaria case detection in a cohort of 1548 total children aged 6–59 months; (2) enhanced passive surveillance at health facilities and with community health workers; (3) annual cross-sectional surveys; and (4) entomological surveillance. Prospective microcosting of the intervention and provider and societal costs will be conducted. Insecticide resistance status pattern and changes in local Anopheline populations will be included as important supportive outcomes. Discussion By evaluating the public health impact and cost-effectiveness of IRS with a non-pyrethroid insecticide in a high-transmission setting with

Combination of indoor residual spraying with long-lasting insecticide-treated nets for malaria control in Zambezia, Mozambique: a cluster randomised trial and cost-effectiveness study protocol.

PubMed

Chaccour, Carlos J; Alonso, Sergi; Zulliger, Rose; Wagman, Joe; Saifodine, Abuchahama; Candrinho, Baltazar; Macete, Eusébio; Brew, Joe; Fornadel, Christen; Kassim, Hidayat; Loch, Lourdes; Sacoor, Charfudin; Varela, Kenyssony; Carty, Cara L; Robertson, Molly; Saute, Francisco

2018-01-01

Most of the reduction in malaria prevalence seen in Africa since 2000 has been attributed to vector control interventions. Yet increases in the distribution and intensity of insecticide resistance and higher costs of newer insecticides pose a challenge to sustaining these gains. Thus, endemic countries face challenging decisions regarding the choice of vector control interventions. A cluster randomised trial is being carried out in Mopeia District in the Zambezia Province of Mozambique, where malaria prevalence in children under 5 is high (68% in 2015), despite continuous and campaign distribution of long-lasting insecticide-treated nets (LLINs). Study arm 1 will continue to use the standard, LLIN-based National Malaria Control Programme vector control strategy (LLINs only), while study arm 2 will receive indoor residual spraying (IRS) once a year for 2 years with a microencapsulated formulation of pirimiphos-methyl (Actellic 300 CS), in addition to the standard LLIN strategy (LLINs+IRS). Prior to the 2016 IRS implementation (the first of two IRS campaigns in this study), 146 clusters were defined and stratified per number of households. Clusters were then randomised 1:1 into the two study arms. The public health impact and cost-effectiveness of IRS intervention will be evaluated over 2 years using multiple methods: (1) monthly active malaria case detection in a cohort of 1548 total children aged 6-59 months; (2) enhanced passive surveillance at health facilities and with community health workers; (3) annual cross-sectional surveys; and (4) entomological surveillance. Prospective microcosting of the intervention and provider and societal costs will be conducted. Insecticide resistance status pattern and changes in local Anopheline populations will be included as important supportive outcomes. By evaluating the public health impact and cost-effectiveness of IRS with a non-pyrethroid insecticide in a high-transmission setting with high LLIN ownership, it is

Application site and adult age impact on the efficacy of two topically-applied insecticides to Culex quinquefasciatus Say

USDA-ARS?s Scientific Manuscript database

Insecticide droplets will impact the mosquito body, but little is known about the interaction of these droplets to a mosquito as it is flying through the air. Droplets of insecticide were applied to the mosquito body in order to determine if a droplet of insecticide will kill a mosquito when it com...

Old ingredients for a new recipe? Neem cake, a low-cost botanical by-product in the fight against mosquito-borne diseases.

PubMed

Benelli, Giovanni; Murugan, Kadarkarai; Panneerselvam, Chellasamy; Madhiyazhagan, Pari; Conti, Barbara; Nicoletti, Marcello

2015-02-01

Mosquitoes (Diptera: Culicidae) represent an important threat to millions of people worldwide, since they act as vectors for important pathogens, such as malaria, yellow fever, dengue and West Nile. Control programmes mainly rely on chemical treatments against larvae, indoor residual spraying and insecticide-treated bed nets. In recent years, huge efforts have been carried out to propose new eco-friendly alternatives, with a special focus on the evaluation of plant-borne mosquitocidal compounds. Major examples are neem-based products (Azadirachta indica A. Juss, Meliaceae) that have been proven as really effective against a huge range of pests of medical and veterinary importance, including mosquitoes. Recent research highlighted that neem cake, a cheap by-product from neem oil extraction, is an important source of mosquitocidal metabolites. In this review, we examined (i) the latest achievements about neem cake metabolomics with special reference to nor-terpenoid and related content; (ii) the neem cake ovicidal, larvicidal and pupicidal toxicity against Aedes, Anopheles and Culex mosquito vectors; (iii) its non-target effects against vertebrates; and (iv) its oviposition deterrence effects on mosquito females. Overall, neem cake can be proposed as an eco-friendly and low-cost source of chemicals to build newer and safer control tools against mosquito vectors.

Estimating a mosquito repellent's potential to reduce malaria in communities.

PubMed

Kiszewski, A E; Darling, S T

2010-12-01

Probability models for assessing a mosquito repellent's potential to reduce malaria transmission are not readily available to public health researchers. To provide a means for estimating the epidemiological efficacy of mosquito repellents in communities, we developed a simple mathematical model. A static probability model is presented to simulate malaria infection in a community during a single transmission season. The model includes five parameters- sporozoite rate, human infection rate, biting pressure, repellent efficacy, and product-acceptance rate. The model assumes that a certain percentage of the population uses a personal mosquito repellent over the course of a seven-month transmission season and that this repellent maintains a constant rate of protective efficacy against the bites of malaria vectors. This model measures the probability of evading infection in circumstances where vector biting pressure, repellent efficacy, and product acceptance may vary. [corrected] Absolute protection using mosquito repellents alone requires high rates of repellent efficacy and product acceptance. [corrected] Using performance data from a highly effective repellent, the model estimates an 88.9% reduction of infections over a seven- month transmission season. A corresponding reduction in the incidence of super-infection in community members not completely evading infection can also be presumed. Thus, the model shows that mass distribution of a repellent with >98% efficacy and >98% product acceptance would suppress new malaria infections to levels lower than those achieved with insecticide treated nets (ITNs). A combination of both interventions could create synergies that result in reductions of disease burden significantly greater than with the use of ITNs alone.

Household use of insecticide consumer products in a dengue endemic area in México

PubMed Central

Loroño-Pino, María Alba; Chan-Dzul, Yamili N.; Zapata-Gil, Rocio; Carrillo-Solís, Claudia; Uitz-Mena, Ana; García-Rejón, Julián E.; Keefe, Thomas J.; Beaty, Barry J.; Eisen, Lars

2014-01-01

Objectives To evaluate household use of insecticide consumer products to kill mosquitoes and other insect pests, as well as the expenditures for using these products, in a dengue endemic area in México. Methods A questionnaire was administered to 441 households in Mérida City or other communities in Yucatán State to assess household use of insecticide consumer products. Results Most (86.6%) households took action to kill insect pests with consumer products. Among those households, the most commonly used product types were insecticide aerosol spray cans (73.6%), electric plug-in insecticide emitters (37.4%), and mosquito coils (28.3%). Mosquitoes were targeted by 89.7% of households using insecticide aerosol spray cans and >99% of households using electric plug-in insecticide emitters or mosquito coils. During the part of the year when a given product type was used, the frequency of use was daily or every 2 days in most of the households for insecticide aerosol spray cans (61.4%), electric plug-in insecticide emitters (76.2%), and mosquito coils (82.1%). For all products used to kill insect pests, the median annual estimated expenditure per household that took action was 408 Mexican pesos ($MXN), which corresponded to ∼31 $U.S. These numbers are suggestive of an annual market in excess of 75 million $MXN (>5.7 million $U.S.) for Mérida City alone. Conclusion Mosquitoes threaten human health and are major nuisances in homes in the study area in México. Households were found to have taken vigorous action to kill mosquitoes and other insect pests and spent substantial amounts of money on insecticide consumer products. PMID:25040259

Impact of long-lasting, insecticidal nets on anaemia and prevalence of Plasmodium falciparum among children under five years in areas with highly resistant malaria vectors.

PubMed

Tokponnon, Filémon T; Ogouyémi, Aurore Hounto; Sissinto, Yolande; Sovi, Arthur; Gnanguenon, Virgile; Cornélie, Sylvie; Adéothy, Adicath Adéola; Ossè, Razaki; Wakpo, Abel; Gbénou, Dina; Oke, Mariam; Kinde-Gazard, Dorothée; Kleinschmidt, Immo; Akogbeto, Martin C; Massougbodji, Achille

2014-03-01

The widespread use of insecticide-treated nets (LLINs) leads to the development of vector resistance to insecticide. This resistance can reduce the effectiveness of LLIN-based interventions and perhaps reverse progress in reducing malaria morbidity. To prevent such difficulty, it is important to know the real impact of resistance in the effectiveness of mosquito nets. Therefore, an assessment of LLIN efficacy was conducted in malaria prevention among children in high and low resistance areas. The study was conducted in four rural districts and included 32 villages categorized as low or high resistance areas in Plateau Department, south-western Benin. Larvae collection was conducted to measure vector susceptibility to deltamethrin and knockdown resistance (kdr) frequency. In each resistance area, around 500 children were selected to measure the prevalence of malaria infection as well as the prevalence of anaemia associated with the use of LLINs. Observed mortalities of Anopheles gambiae s.s population exposed to deltamethrin ranged from 19 to 96%. Knockdown resistance frequency was between 38 and 84%. The prevalence of malaria infection in children under five years was 22.4% (19.9-25.1). This prevalence was 17.3% (14.2-20.9) in areas of high resistance and 27.1% (23.5-31.1) in areas of low resistance (p=0.04). Eight on ten children that were aged six - 30 months against seven on ten of those aged 31-59 months were anaemic. The anaemia observed in the six to 30-month old children was significantly higher than in the 31-59 month old children (p=0.00) but no difference associated with resistance areas was observed (p=0.35). The net use rate was 71%. The risk of having malaria was significantly reduced (p<0.05) with LLIN use in both low and high resistance areas. The preventive effect of LLINs in high resistance areas was 60% (95% CI: 40-70), and was significantly higher than that observed in low resistance areas (p<0.05). The results of this study showed that the

Long-lasting insecticide-treated house screens and targeted treatment of productive breeding-sites for dengue vector control in Acapulco, Mexico.

PubMed

Che-Mendoza, Azael; Guillermo-May, Guillermo; Herrera-Bojórquez, Josué; Barrera-Pérez, Mario; Dzul-Manzanilla, Felipe; Gutierrez-Castro, Cipriano; Arredondo-Jiménez, Juan I; Sánchez-Tejeda, Gustavo; Vazquez-Prokopec, Gonzalo; Ranson, Hilary; Lenhart, Audrey; Sommerfeld, Johannes; McCall, Philip J; Kroeger, Axel; Manrique-Saide, Pablo

2015-02-01

Long-lasting insecticidal net screens (LLIS) fitted to domestic windows and doors in combination with targeted treatment (TT) of the most productive Aedes aegypti breeding sites were evaluated for their impact on dengue vector indices in a cluster-randomised trial in Mexico between 2011 and 2013. Sequentially over 2 years, LLIS and TT were deployed in 10 treatment clusters (100 houses/cluster) and followed up over 24 months. Cross-sectional surveys quantified infestations of adult mosquitoes, immature stages at baseline (pre-intervention) and in four post-intervention samples at 6-monthly intervals. Identical surveys were carried out in 10 control clusters that received no treatment. LLIS clusters had significantly lower infestations compared to control clusters at 5 and 12 months after installation, as measured by adult (male and female) and pupal-based vector indices. After addition of TT to the intervention houses in intervention clusters, indices remained significantly lower in the treated clusters until 18 (immature and adult stage indices) and 24 months (adult indices only) post-intervention. These safe, simple affordable vector control tools were well-accepted by study participants and are potentially suitable in many regions at risk from dengue worldwide. © The author 2015. The World Health Organization has granted Oxford University Press permission for the reproduction of this article.

Plasmodium infection decreases fecundity and increases survival of mosquitoes.

PubMed

Vézilier, J; Nicot, A; Gandon, S; Rivero, A

2012-10-07

Long-lived mosquitoes maximize the chances of Plasmodium transmission. Yet, in spite of decades of research, the effect of Plasmodium parasites on mosquito longevity remains highly controversial. On the one hand, many studies report shorter lifespans in infected mosquitoes. On the other hand, parallel (but separate) studies show that Plasmodium reduces fecundity and imply that this is an adaptive strategy of the parasite aimed at redirecting resources towards longevity. No study till date has, however, investigated fecundity and longevity in the same individuals to see whether this prediction holds. In this study, we follow for both fecundity and longevity in Plasmodium-infected and uninfected mosquitoes using a novel, albeit natural, experimental system. We also explore whether the genetic variations that arise through the evolution of insecticide resistance modulate the effect of Plasmodium on these two life-history traits. We show that (i) a reduction in fecundity in Plasmodium-infected mosquitoes is accompanied by an increase in longevity; (ii) this increase in longevity arises through a trade-off between reproduction and survival; and (iii) in insecticide-resistant mosquitoes, the slope of this trade-off is steeper when the mosquito is infected by Plasmodium (cost of insecticide resistance).

Effects of lambda-cyhalothrin on mosquito larvae and predatory aquatic insects.

PubMed

Lawler, Sharon P; Dritz, Deborah A; Christiansen, Julie A; Cornel, Anthony J

2007-03-01

Agricultural insecticides can affect mosquito production in rice fields by controlling mosquitoes, disrupting biological control or contributing to selection of insecticide resistance. The duration of insecticidal activity of the pyrethroid lambda-cyhalothrin was quantified on predatory insects in rice fields and on three kinds of mosquito larva: a pyrethroid-susceptible strain of Culex tarsalis Coquillet, a pyrethroid-resistant strain of Cx pipiens L. (sensu lato) and non-resistant Cx pipiens s.l. Lambda-cyhalothrin killed most caged, susceptible mosquitoes for up to 21 days. It killed fewer resistant Cx pipiens s.l., but suppressed their survival for over a week. Lambda-cyhalothrin suppressed field populations of predatory insects through day 29. Agricultural use of lambda-cyhalothrin can provide incidental mosquito control. However, the pyrethroid persisted in sediment and gradually decreased in activity, which could contribute to selection of pyrethroid-resistant mosquitoes. Because caged mosquitoes showed good survival before predators recovered, disruption of biological control is possible. It is therefore advisable for growers and mosquito control agencies to communicate about pesticide use. Copyright 2006 Society of Chemical Industry.

Insecticide-Treated Nets Utilization and Associated Factors among under-5 Years Old Children in Mirab-Abaya District, Gamo-Gofa Zone, Ethiopia.

PubMed

Admasie, Amha; Zemba, Amanuel; Paulos, Wondimagegn

2018-01-01

Malaria can be prevented using cost-effective interventions. It can be prevented at large via the use of insecticide-treated mosquito nets (ITNs). The use of ITNs decreases malaria mortality rates by 55% in under-5 years old children in Africa, Ethiopia, realizing the effectiveness, scaling up distribution and utilization of ITNs to cover 100% of children less than 5 years of age. However, little is known about ITNs utilization and factors associated with the utilization in under-5 years old children in the study area yet. The purpose of this study was to assess the level and associated factors of ITNs utilization in under-5 years old children among households with under-5 years old children of Mirab Abaya District, Gamo Gofa Zone, Ethiopia. A community-based cross-sectional study was conducted during August-September, 2016. Six study Kebeles were identified by simple random sampling technique and 398 households with at least one under-5 years old children were selected by random sampling technique using computer generated random numbers from health post family folders. Structured, interviewer questionnaire was administered to mothers or care givers of the children. Data were entered to Epi Info Version 3.5 and analyzed in SPSS version 21 statistical software. Bivariate and multivariate logistic regression analysis was done. P -value <0.05 and odds ratio with 95% confidence interval were used for the determination of associations between dependent and predictor variables. Results were presented in narrations, tables, and graph. Among 398 under-5 years old children assessed, the majority, 362 (91.0%) of them had access to ITN, but only 137 (37.2%) of the child had ITNs utilization during the previous night prior to the survey. Households with age of mothers or caretakers 31-44 years, AOR = 0.03, 95% CI (0.01-0.07) and ≥45 years of age; AOR = 0.05, 95% CI (0.01-0.58); households with family size ≤5 members, AOR = 11.23, 95% CI (4

Impact of Insecticide-Treated Net Ownership on All-Cause Child Mortality in Malawi, 2006–2010

PubMed Central

Florey, Lia S.; Bennett, Adam; Hershey, Christine L.; Bhattarai, Achuyt; Nielsen, Carrie F.; Ali, Doreen; Luhanga, Misheck; Taylor, Cameron; Eisele, Thomas P.; Yé, Yazoume

2017-01-01

Abstract. Insecticide-treated nets (ITNs) have been shown to be highly effective at reducing malaria morbidity and mortality in children. However, there are limited studies that assess the association between increasing ITN coverage and child mortality over time, at the national level, and under programmatic conditions. Two analytic approaches were used to examine this association: a retrospective cohort analysis of individual children and a district-level ecologic analysis. To evaluate the association between household ITN ownership and all-cause child mortality (ACCM) at the individual level, data from the 2010 Demographic and Health Survey (DHS) were modeled in a Cox proportional hazards framework while controlling for numerous environmental, household, and individual confounders through the use of exact matching. To evaluate population-level association between ITN ownership and ACCM between 2006 and 2010, program ITN distribution data and mortality data from the 2006 Multiple Indicator Cluster Survey and the 2010 DHS were aggregated at the district level and modeled using negative binomial regression. In the Cox model controlling for household, child and maternal health factors, children between 1 and 59 months in households owning an ITN had significantly lower mortality compared with those without an ITN (hazard ratio = 0.75, 95% confidence interval [CI] = 0.62–90). In the district-level model, higher ITN ownership was significantly associated with lower ACCM (incidence rate ratio = 0.77; 95% CI = 0.60–0.98). These findings suggest that increasing ITN ownership may have contributed to the decline in ACCM during 2006–2010 in Malawi and represent a novel use of district-level data from nationally representative surveys. PMID:28990922

Synergistic insecticidal and repellent effects of combined pyrethroid and repellent-impregnated bed nets using a novel long-lasting polymer-coating multi-layer technique.

PubMed

Faulde, Michael K; Nehring, Oliver

2012-08-01

New and improved strategies for malaria control and prevention are urgently needed. As a contribution to an optimized personal protection strategy, a novel long-lasting insecticide and repellent-treated net (LLIRN) has been designed by binding combinations of permethrin plus N,N-diethyl-m-toluamide (DEET), or insect repellent 3535 (IR3535), and etofenprox plus DEET, onto fibres of bed net fabric employing a new multi-layer polymer-coating technique. Protective repellent efficacy, toxicological effectiveness and residual activity of 12 LLIRN types have been evaluated by laboratory testing against adult Aedes aegypti. The novel multi-layer LLIRN design allowed simultaneous embedding at concentrations up to 5,930 mg/m(2) for DEET, 3,408 mg/m(2) for IR3535, 2,296 mg/m(2) for permethrin and 2,349 mg/m(2) for etofenprox, respectively. IR3535 layers prevented co-binding of additional pyrethroid-containing polymer layers, thus making pyrethroids plus DEET LLIRNs an ideal combination. All LLIRNs revealed synergistic insecticidal effects which, when measured against concentration controls of the isolated compounds, were significant in all LLIRN types designed. DEET in DEET plus permethrin LLIRNs significantly (p < 0.0001) reduced the concentration-dependent permethrin 100 % knockdown (KD) time from 55 to 75 %, the corresponding 100 % kill time (p < 0.0001) from 55 to 64 %. DEET in DEET plus etofenprox LLIRNs reduced the dose-specific 100 % knockdown (KD) time of etofenprox from 42 to 50 % (p = 0.004), the 100 % kill time from 25 to 38 % (p < 0.0001). Permethrin or etofenprox did not influence spatial repellency of DEET or IR3535 on LLIRNs. Vice versa, DEET and IR3535 increased spatial and excitatory repellency and reduced landing and probing frequency on LLIRNs resulting in strongly enhanced biting protection, even at low concentrations. One hundred percent biting and probing protection of stored LLIRNs was preserved for 83 weeks with the 5,930 mg/m(2) DEET

A novel video-tracking system to quantify the behaviour of nocturnal mosquitoes attacking human hosts in the field.

PubMed

Angarita-Jaimes, N C; Parker, J E A; Abe, M; Mashauri, F; Martine, J; Towers, C E; McCall, P J; Towers, D P

2016-04-01

Many vectors of malaria and other infections spend most of their adult life within human homes, the environment where they bloodfeed and rest, and where control has been most successful. Yet, knowledge of peri-domestic mosquito behaviour is limited, particularly how mosquitoes find and attack human hosts or how insecticides impact on behaviour. This is partly because technology for tracking mosquitoes in their natural habitats, traditional dwellings in disease-endemic countries, has never been available. We describe a sensing device that enables observation and recording of nocturnal mosquitoes attacking humans with or without a bed net, in the laboratory and in rural Africa. The device addresses requirements for sub-millimetre resolution over a 2.0 × 1.2 × 2.0 m volume while using minimum irradiance. Data processing strategies to extract individual mosquito trajectories and algorithms to describe behaviour during host/net interactions are introduced. Results from UK laboratory and Tanzanian field tests showed that Culex quinquefasciatus activity was higher and focused on the bed net roof when a human host was present, in colonized and wild populations. Both C. quinquefasciatus and Anopheles gambiae exhibited similar behavioural modes, with average flight velocities varying by less than 10%. The system offers considerable potential for investigations in vector biology and many other fields. © 2016 The Authors.

Price subsidies and the market for mosquito nets in developing countries: A study of Tanzania's discount voucher scheme.

PubMed

Gingrich, Chris D; Hanson, Kara; Marchant, Tanya; Mulligan, Jo-Ann; Mponda, Hadji

2011-07-01

This study uses a partial equilibrium simulation model to explore how price subsidies for insecticide-treated mosquito nets (ITNs) affect households' purchases of ITNs. The model describes the ITN market in a typical developing country and is applied to the situation in Tanzania, where the Tanzania National Voucher Scheme (TNVS) provides a targeted subsidy to vulnerable population groups by means of a discount voucher. The data for this study come from a nationally-representative household survey completed July-August 2006 covering over 4300 households in 21 districts. The simulation results show the impact of the voucher program on ITN coverage among target households, namely those that experienced the birth of a child. More specifically, the share of target households purchasing an ITN increased from 18 to 62 percent because of the discount voucher. The model also suggests that the voucher program could cause the retail ITN price to rise due to an overall increase in demand. As a result, ITN purchases by households without a voucher may actually decline. The simulation model suggests that additional increases toward the stated goal of 80 percent ITN coverage for pregnant women and children could best be achieved through a combination of "catch up" mass distribution programs and expanding the target group for the voucher program to cover additional households. The model can be employed in other countries considering use of a targeted price subsidy for ITNs, and could be adapted to assess the impact of subsidies for other public health commodities. Copyright © 2011 Elsevier Ltd. All rights reserved.

Dengue vector management using insecticide treated materials and targeted interventions on productive breeding-sites in Guatemala.

PubMed

Rizzo, Nidia; Gramajo, Rodrigo; Escobar, Maria Cabrera; Arana, Byron; Kroeger, Axel; Manrique-Saide, Pablo; Petzold, Max

2012-10-30

In view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies particularly for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites. The study was conducted as a cluster randomized community trial using "reduction of the vector population" as the main outcome variable. The trial had two arms: 10 intervention clusters (neighborhoods) and 10 control clusters in the town of Poptun Guatemala. Activities included entomological assessments (characteristics of breeding-sites, pupal productivity, Stegomyia indices) at baseline, 6 weeks after the first intervention (coverage of window and exterior doorways made of PermaNet 2.0 netting, factory treated with deltamethrin at 55 mg/m2, and of 200 L drums with similar treated material) and 6 weeks after the second intervention (combination of treated materials and other suitable interventions targeting productive breeding-sites i.e larviciding with Temephos, elimination etc.). The second intervention took place 17 months after the first intervention. The insecticide residual activity and the insecticidal content were also studied at different intervals. Additionally, information about demographic characteristics, cost of the intervention, coverage of houses protected and satisfaction in the population with the interventions was collected. At baseline (during the dry season) a variety of productive container types for Aedes pupae were identified: various container types holding >20 L, 200 L drums, washbasins and buckets (producing 83.7% of all pupae). After covering 100% of windows and exterior doorways and a small number of drums (where the commercial cover could be fixed) in 970 study households, tropical rains occurred in the area and

Dengue vector management using insecticide treated materials and targeted interventions on productive breeding-sites in Guatemala

PubMed Central

2012-01-01

Background In view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies particularly for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites. Methods The study was conducted as a cluster randomized community trial using “reduction of the vector population” as the main outcome variable. The trial had two arms: 10 intervention clusters (neighborhoods) and 10 control clusters in the town of Poptun Guatemala. Activities included entomological assessments (characteristics of breeding-sites, pupal productivity, Stegomyia indices) at baseline, 6 weeks after the first intervention (coverage of window and exterior doorways made of PermaNet 2.0 netting, factory treated with deltamethrin at 55 mg/m2, and of 200 L drums with similar treated material) and 6 weeks after the second intervention (combination of treated materials and other suitable interventions targeting productive breeding-sites i.e larviciding with Temephos, elimination etc.). The second intervention took place 17 months after the first intervention. The insecticide residual activity and the insecticidal content were also studied at different intervals. Additionally, information about demographic characteristics, cost of the intervention, coverage of houses protected and satisfaction in the population with the interventions was collected. Results At baseline (during the dry season) a variety of productive container types for Aedes pupae were identified: various container types holding >20 L, 200 L drums, washbasins and buckets (producing 83.7% of all pupae). After covering 100% of windows and exterior doorways and a small number of drums (where the commercial cover could be fixed) in 970 study households, tropical

Evaluation of a national universal coverage campaign of long-lasting insecticidal nets in a rural district in north-west Tanzania.

PubMed

West, Philippa A; Protopopoff, Natacha; Rowland, Mark W; Kirby, Matthew J; Oxborough, Richard M; Mosha, Franklin W; Malima, Robert; Kleinschmidt, Immo

2012-08-10

Insecticide-treated nets (ITN) are one of the most effective measures for preventing malaria. Mass distribution campaigns are being used to rapidly increase net coverage in at-risk populations. This study had two purposes: to evaluate the impact of a universal coverage campaign (UCC) of long-lasting insecticidal nets (LLINs) on LLIN ownership and usage, and to identify factors that may be associated with inadequate coverage. In 2011 two cross-sectional household surveys were conducted in 50 clusters in Muleba district, north-west Tanzania. Prior to the UCC 3,246 households were surveyed and 2,499 afterwards. Data on bed net ownership and usage, demographics of household members and household characteristics including factors related to socio-economic status were gathered, using an adapted version of the standard Malaria Indicator Survey. Specific questions relating to the UCC process were asked. The proportion of households with at least one ITN increased from 62.6% (95% Confidence Interval (CI) = 60.9-64.2) before the UCC to 90.8% (95% CI = 89.0-92.3) afterwards. ITN usage in all residents rose from 40.8% to 55.7%. After the UCC 58.4% (95% CI = 54.7-62.1) of households had sufficient ITNs to cover all their sleeping places. Households with children under five years (OR = 2.4, 95% CI = 1.9-2.9) and small households (OR = 1.9, 95% CI = 1.5-2.4) were most likely to reach universal coverage. Poverty was not associated with net coverage. Eighty percent of households surveyed received LLINs from the campaign. The UCC in Muleba district of Tanzania was equitable, greatly improving LLIN ownership and, more moderately, usage. However, the goal of universal coverage in terms of the adequate provision of nets was not achieved. Multiple, continuous delivery systems and education activities are required to maintain and improve bed net ownership and usage.

Small-scale field evaluation of push-pull system against early- and outdoor-biting malaria mosquitoes in an area of high pyrethroid resistance in Tanzania

PubMed Central

Mmbando, Arnold S.; Ngowo, Halfan S.; Kilalangongono, Masoud; Abbas, Said; Matowo, Nancy S.; Moore, Sarah J.; Okumu, Fredros O.

2017-01-01

Background: Despite high coverage of indoor interventions like insecticide-treated nets, mosquito-borne infections persist, partly because of outdoor-biting, early-biting and insecticide-resistant vectors. Push-pull systems, where mosquitoes are repelled from humans and attracted to nearby lethal targets, may constitute effective complementary interventions. Methods: A partially randomized cross-over design was used to test efficacy of push-pull in four experimental huts and four local houses, in an area with high pyrethroid resistance in Tanzania. The push-pull system consisted of 1.1% or 2.2% w/v transfluthrin repellent dispensers and an outdoor lure-and-kill device (odour-baited mosquito landing box). Matching controls were set up without push-pull. Adult male volunteers collected mosquitoes attempting to bite them outdoors, but collections were also done indoors using exit traps in experimental huts and by volunteers in the local houses. The collections were done hourly (1830hrs-0730hrs) and mosquito catches compared between push-pull and controls. An. gambiae s.l. and An. funestus s.l. were assessed by PCR to identify sibling species, and ELISA to detect Plasmodium falciparum and blood meal sources. Results: Push-pull in experimental huts reduced outdoor-biting for An. arabiensis and Mansonia species by 30% and 41.5% respectively. However, the reductions were marginal and insignificant for An. funestus (12.2%; p>0.05) and Culex (5%; p>0.05). Highest protection against all species occurred before 2200hrs. There was no significant difference in number of mosquitoes inside exit traps in huts with or without push-pull. In local households, push-pull significantly reduced indoor and outdoor-biting of An. arabiensis by 48% and 25% respectively, but had no effect on other species. Conclusion: This push-pull system offered modest protection against outdoor-biting An. arabiensis, without increasing indoor mosquito densities. Additional experimentation is required to

Repelling mosquitoes with essential oils

NASA Astrophysics Data System (ADS)

Riley, L.

2017-12-01

Mosquitoes carry diseases than can lead to serious illness and death. According to the World Health Organization, mosquitoes infect over 300 million people a year with Malaria and Dengue Fever, two life threatening diseases vectored by mosquitoes. Although insecticides are the most effective way to control mosquitoes, they are not always environmentally friendly. Therefore, alternative tactics should be considered. In this study, we looked at the repellency of various essential oils on female Aedes aegypti through a series of laboratory assays.

An insecticide resistance-breaking mosquitocide targeting inward rectifier potassium channels in vectors of Zika virus and malaria.

PubMed

Swale, Daniel R; Engers, Darren W; Bollinger, Sean R; Gross, Aaron; Inocente, Edna Alfaro; Days, Emily; Kanga, Fariba; Johnson, Reed M; Yang, Liu; Bloomquist, Jeffrey R; Hopkins, Corey R; Piermarini, Peter M; Denton, Jerod S

2016-11-16

Insecticide resistance is a growing threat to mosquito control programs around the world, thus creating the need to discover novel target sites and target-specific compounds for insecticide development. Emerging evidence suggests that mosquito inward rectifier potassium (Kir) channels represent viable molecular targets for developing insecticides with new mechanisms of action. Here we describe the discovery and characterization of VU041, a submicromolar-affinity inhibitor of Anopheles (An.) gambiae and Aedes (Ae.) aegypti Kir1 channels that incapacitates adult female mosquitoes from representative insecticide-susceptible and -resistant strains of An. gambiae (G3 and Akron, respectively) and Ae. aegypti (Liverpool and Puerto Rico, respectively) following topical application. VU041 is selective for mosquito Kir channels over several mammalian orthologs, with the exception of Kir2.1, and is not lethal to honey bees. Medicinal chemistry was used to develop an analog, termed VU730, which retains activity toward mosquito Kir1 but is not active against Kir2.1 or other mammalian Kir channels. Thus, VU041 and VU730 are promising chemical scaffolds for developing new classes of insecticides to combat insecticide-resistant mosquitoes and the transmission of mosquito-borne diseases, such as Zika virus, without harmful effects on humans and beneficial insects.

Behaviour of Anopheles albimanus in relation to pyrethroid-treated bednets.

PubMed

Arredondo-Jiménez, J I; Rodríguez, M H; Loyola, E G; Bown, D N

1997-01-01

Responses of the malaria vector Anopheles albimanus to pyrethroid impregnated bednets made of cotton or nylon, compared with untreated nets, were investigated in houses occupied by two people inside and/or outside two bednets, in coastal Chiapas, México. The pyrethroid used was lambdacyhalothrin 30 mg a.i./m2. Bioassay mortality rates of An.albimanus exposed to treated nets for 3 or 15 min, rose from 40-55% to 90-100% for nylon nets 3-19 weeks post-treatment, but were consistently lower for treated cotton nets. An.albimanus females (collected unfed on human bait) were released in houses surrounded by curtains for trapping mosquitoes that exited from the house. Floor sheets were used in and around each experimental house for retrieving any mosquitoes knocked-down and/or killed. During post-treatment assessment for 17 weeks, An.albimanus blood-feeding success rates were 23-24% with untreated nets, 14-18% with treated cotton nets and 8-15% with treated nylon nets, significantly reduced when both human baits were inside the treated bednets, but not when one or more baits were outside the treated bednet(s) within the house. Proportions of mosquitoes leaving houses < 3 h post-release were 53-59% from houses with untreated bednets versus 65-78% with treated bednets. Except in one case (when both humans were outside treated cotton nets), these increased early exit rates were significant, whether or not the human baits were inside the treated bednets indoors. Mortality rates of An.albimanus females exiting overnight (22.00-06.00 hours) averaged 15-39% from houses with treated cotton and 16-46% with treated nylon nets, very significantly greater than the control mean rates of 6-8% mortality with untreated nets. Observations on wild-caught An.albimanus females marked with fluorescent powder and released indoors revealed that few mosquitoes (3-11%) actually contacted the bednets unless both human baits remained under them - when contact rates were 22% on treated nylon, 23% on

Entomopathogenic fungal infection leads to temporospatial modulation of the mosquito immune system

USDA-ARS?s Scientific Manuscript database

Alternative methods of mosquito control are needed to tackle the rising burden of mosquito-borne diseases while minimizing the use of synthetic insecticides which are not only harmful to the environment but also are increasingly threatened by the rapid and widespread development of insecticide resis...

Evaluation of community-based continuous distribution of long-lasting insecticide-treated nets in Toamasina II District, Madagascar.

PubMed

de Beyl, Celine Zegers; Kilian, Albert; Brown, Andrea; Sy-Ar, Mohamad; Selby, Richmond Ato; Randriamanantenasoa, Felicien; Ranaivosoa, Jocelyn; Zigirumugabe, Sixte; Gerberg, Lilia; Fotheringham, Megan; Lynch, Matthew; Koenker, Hannah

2017-08-10

Continuous distribution of insecticide-treated nets (ITNs) is thought to be an effective mechanism to maintain ITN ownership and access between or in the absence of mass campaigns, but evidence is limited. A community-based ITN distribution pilot was implemented and evaluated in Toamasina II District, Madagascar, to assess this new channel for continuous ITN distribution. Beginning 9 months after the December 2012 mass campaign, a community-based distribution pilot ran for an additional 9 months, from September 2013 to June 2014. Households requested ITN coupons from community agents in their village. After verification by the agents, households exchanged the coupon for an ITN at a distribution point. The evaluation was a two-stage cluster survey with a sample size of 1125 households. Counterfactual ITN ownership and access were calculated by excluding ITNs received through the community pilot. At the end of the pilot, household ownership of any ITN was 96.5%, population access to ITN was 81.5 and 61.5% of households owned at least 1 ITN for every 2 people. Without the ITNs provided through the community channel, household ownership of any ITN was estimated at 74.6%, population access to an ITN at 55.5%, and households that owned at least 1 ITN for 2 people at only 34.7%, 18 months after the 2012 campaign. Ownership of community-distributed ITNs was higher among the poorest wealth quintiles. Over 80% of respondents felt the community scheme was fair and simple to use. Household ITN ownership and population ITN access exceeded RBM targets after the 9-month community distribution pilot. The pilot successfully provided coupons and ITNs to households requesting them, particularly for the least poor wealth quintiles, and the scheme was well-perceived by communities. Further research is needed to determine whether community-based distribution can sustain ITN ownership and access over the long term, how continuous availability of ITNs affects household net replacement

Susceptibility of Culicidae Mosquitoes to Some Insecticides Recommended by WHO in a Malaria Endemic Area of Southeastern Iran

PubMed Central

Fathian, Mousa; Vatandoost, Hassan; Moosa-Kazemi, Seyed Hassan; Raeisi, Ahmad; Yaghoobi-Ershadi, Mohammad Reza; Oshaghi, Mohammad Ali; Sedaghat, Mohammad Mehdi

2015-01-01

Background: According to the national strategy plan on monitoring of insecticides resistance, this study was carried out to determine the base line susceptibility of the Culicidae mosquitoes to the WHO-recommended insecticides in an endemic focus of malaria in southeastern Iran. Methods: Larval collection was carried out by dipping method and adult collection occurred by suction tube from January to December 2010. The susceptibility test was assessed to DDT 4 %, malathion 5 %, propoxur 0.1 %, deltamethrin 0.05 %, lambda-cyhalothrin 0.05 %, and cyfluthrin 0.15 % at different interval times (discriminative dose) followed by 24 h recovery period. The LT50 and LT90 values were calculated for plotting the regression line using Microsoft office Excel software ver. 2007. Results: Anopheles stephensi was quite resistant to DDT and showed susceptible or tolerant to other insecticides. The LT50 and LT90 values to DDT in this species were 29.07, and 98.26 minutes, respectively. Anopheles culicifacies and Anopheles dthali were found susceptible or tolerant to insecticides. Culex pipiens was found resistance to DDT, propoxur, lambda-cyhalothrin and cyfluthrin whereas observed susceptible to malathion and tolerant to deltamethrin. Ochlerotatus caspius sl. was resistant to DDT, whereas found susceptible to other insecticides. Culisita longiareolata was susceptible to deltamethrin, whereas tolerant to other insecticides. The LT50 and LT90 values of Cs. longiareolata to DDT were 17.82, and 51.26 minutes. Conclusion: We suggested the same study in different parts of the country for monitoring and evaluation of control measures. PMID:26114141

Effectiveness and Cost of Insecticide-Treated Bed Nets and Indoor Residual Spraying for the Control of Cutaneous Leishmaniasis: A Cluster-Randomized Control Trial in Morocco

PubMed Central

Faraj, Chafika; Yukich, Joshua; Adlaoui, El Bachir; Wahabi, Rachid; Mnzava, Abraham Peter; Kaddaf, Mustapha; El Idrissi, Abderrahmane Laamrani; Ameur, Btissam; Kleinschmidt, Immo

2016-01-01

Cutaneous leishmaniasis (CL) remains an important public health problem in Morocco. A cluster-randomized trial was conducted with the following three study arms: 1) long-lasting insecticide-treated nets (LLINs) plus standard of care environmental management (SoC-EM), 2) indoor residual spraying (IRS) with α-cypermethrin plus SoC-EM, and 3) SoC-EM alone. Incidence of new CL cases by passive and active case detection, sandfly abundance, and cost and cost-effectiveness was compared between study arms over 5 years. Incidence of CL and sandfly abundance were significantly lower in the IRS arm compared with SoC-EM (CL incidence rate ratio = 0.32, 95% confidence interval [CI] = 0.15–0.69, P = 0.005 and sandfly abundance ratio = 0.39, 95% CI = 0.18–0.85, P = 0.022). Reductions in the LLIN arm of the study were not significant, possibly due to poor compliance. IRS was effective and more cost-effective for the prevention of CL in Morocco. PMID:26811431

Status of pyrethroid resistance in Anopheles gambiae s. s. M form prior to the scaling up of Long Lasting Insecticidal Nets (LLINs) in Adzopé, Eastern Côte d’Ivoire

PubMed Central

2012-01-01

Background The growing development of pyrethroid resistance constitutes a serious threat to malaria control programmes and if measures are not taken in time, resistance may compromise control efforts in the foreseeable future. Prior to Long Lasting Insecticidal Nets (LLINs) distribution in Eastern Cote d’Ivoire, we conducted bioassays to inform the National Malaria Control Programme of the resistance status of the main malaria vector, Anopheles gambiae s. s. and the need for close surveillance of resistance. Methods Larvae of An. gambiae s. s. were collected in two areas of Adzopé (Port-Bouët and Tsassodji) and reared to adults. WHO susceptibility tests with impregnated filter papers were carried out to detect resistance to three pyrethroids commonly used to develop LLINs: permethrin 1%, deltamethrin 0.05% and lambda-cyhalothrin 0.05%. Molecular assays were conducted to detect M and S forms and the L1014F kdr allele in individual mosquitoes. Results Resistance, at various degrees was detected in both areas of Adzopé. Overall, populations of An. gambiae at both sites surveyed showed equivalent frequency of the L1014F kdr allele (0.67) but for all tested pyrethroids, there were significantly higher survival rates for mosquitoes from Tsassodji (32–58%) than those from Port-Bouët (3–32%) (p < 0.001), indicating the implication of resistance mechanisms other than kdr alone. During the survey period (May–June) in this forested area of Côte d’Ivoire, An. gambiae s. s. found were exclusively of the M form and were apparently selected for pyrethroid resistance through agricultural and household usage of insecticides. Conclusion Prior to LLINs scaling up in Eastern Côte d’Ivoire, resistance was largely present at various levels in An. gambiae. Underlying mechanisms included the high frequency of the L1014F kdr mutation and other unidentified components, probably metabolic detoxifiers. Their impact on the efficacy of the planned strategy (LLINs) in the

The underlying reasons for very high levels of bed net use, and higher malaria infection prevalence among bed net users than non-users in the Tanzanian city of Dar es Salaam: a qualitative study.

PubMed

Msellemu, Daniel; Shemdoe, Aloysia; Makungu, Christina; Mlacha, Yeromini; Kannady, Khadija; Dongus, Stefan; Killeen, Gerry F; Dillip, Angel

2017-10-23

Bed nets reduce malaria-related illness and deaths, by forming a protective barrier around people sleeping under them. When impregnated with long-lasting insecticide formulations they also repel or kill mosquitoes attempting to feed upon sleeping humans, and can even suppress entire populations of malaria vectors that feed predominantly upon humans. Nevertheless, an epidemiological study in 2012 demonstrated higher malaria prevalence among bed net users than non-users in urban Dar es Salaam, Tanzania. Focus group discussions were conducted with women from four selected wards of Dar es Salaam city, focusing on four major themes relating to bed net use behaviours: (1) reasons for bed net use, (2) reasons for not using bed nets, (3) stimuli or reminders for people to use a bed net (4) perceived reasons for catching malaria while using a bed net. An analytical method by framework grouping of relevant themes was used address key issues of relevance to the study objectives. Codes were reviewed and grouped into categories and themes. All groups said the main reason for bed net use was protection against malaria. Houses with well-screened windows, with doors that shut properly, and that use insecticidal sprays against mosquitoes, were said not to use bed nets, while frequent attacks from malaria was the main stimulus for people to use bed nets. Various reasons were mentioned as potential reasons that compromise bed net efficacy, the most common of which were: (1) bed net sharing by two or more people, especially if one occupant tends to come to bed late at night, and does not tuck in the net 71%; (2) one person shares the bed but does not use the net, moving it away from the side on which s/he sleeps 68%; (3) ineffective usage habits, called ulalavi, in which a sprawling sleeper either touches the net while sleeping up against it or leaves a limb hanging outside of it 68%. Less common reasons mentioned included: (1) Small bed nets which become un-tucked at night (31%); (2

A Cluster-Randomized Trial of Insecticide-Treated Curtains for Dengue Vector Control in Thailand

PubMed Central

Lenhart, Audrey; Trongtokit, Yuwadee; Alexander, Neal; Apiwathnasorn, Chamnarn; Satimai, Wichai; Vanlerberghe, Veerle; Van der Stuyft, Patrick; McCall, Philip J.

2013-01-01

The efficacy of insecticide-treated window curtains (ITCs) for dengue vector control was evaluated in Thailand in a cluster-randomized controlled trial. A total of 2,037 houses in 26 clusters was randomized to receive the intervention or act as control (no treatment). Entomological surveys measured Aedes infestations (Breteau index, house index, container index, and pupae per person index) and oviposition indices (mean numbers of eggs laid in oviposition traps) immediately before and after intervention, and at 3-month intervals over 12 months. There were no consistent statistically significant differences in entomological indices between intervention and control clusters, although oviposition indices were lower (P < 0.01) in ITC clusters during the wet season. It is possible that the open housing structures in the study reduced the likelihood of mosquitoes making contact with ITCs. ITCs deployed in a region where this house design is common may be unsuitable for dengue vector control. PMID:23166195

A Single Crossing-Over Event in Voltage-Sensitive Na+ Channel Genes May Cause Critical Failure of Dengue Mosquito Control by Insecticides

PubMed Central

Hirata, Koichi; Komagata, Osamu; Itokawa, Kentaro; Yamamoto, Atsushi; Tomita, Takashi; Kasai, Shinji

2014-01-01

The voltage-sensitive sodium (Na+) channel (Vssc) is the target site of pyrethroid insecticides. Pest insects develop resistance to this class of insecticide by acquisition of one or multiple amino acid substitution(s) in this channel. In Southeast Asia, two major Vssc types confer pyrethroid resistance in the dengue mosquito vector Aedes aegypti, namely, S989P+V1016G and F1534C. We expressed several types of Vssc in Xenopus oocytes and examined the effect of amino acid substitutions in Vssc on pyrethroid susceptibilities. S989P+V1016G and F1534C haplotypes reduced the channel sensitivity to permethrin by 100- and 25-fold, respectively, while S989P+V1016G+F1534C triple mutations reduced the channel sensitivity to permethrin by 1100-fold. S989P+V1016G and F1534C haplotypes reduced the channel sensitivity to deltamethrin by 10- and 1-fold (no reduction), respectively, but S989P+V1016G+F1534C triple mutations reduced the channel sensitivity to deltamethrin by 90-fold. These results imply that pyrethroid insecticides are highly likely to lose their effectiveness against A. aegypti if such a Vssc haplotype emerges as the result of a single crossing-over event; thus, this may cause failure to control this key mosquito vector. Here, we strongly emphasize the importance of monitoring the occurrence of triple mutations in Vssc in the field population of A. aegypti. PMID:25166902

Interdependence of domestic malaria prevention measures and mosquito-human interactions in urban Dar es Salaam, Tanzania.

PubMed

Geissbühler, Yvonne; Chaki, Prosper; Emidi, Basiliana; Govella, Nicodemus J; Shirima, Rudolf; Mayagaya, Valeliana; Mtasiwa, Deo; Mshinda, Hassan; Fillinger, Ulrike; Lindsay, Steven W; Kannady, Khadija; de Castro, Marcia Caldas; Tanner, Marcel; Killeen, Gerry F

2007-09-19

Successful malaria vector control depends on understanding behavioural interactions between mosquitoes and humans, which are highly setting-specific and may have characteristic features in urban environments. Here mosquito biting patterns in Dar es Salaam, Tanzania are examined and the protection against exposure to malaria transmission that is afforded to residents by using an insecticide-treated net (ITN) is estimated. Mosquito biting activity over the course of the night was estimated by human landing catch in 216 houses and 1,064 residents were interviewed to determine usage of protection measures and the proportion of each hour of the night spent sleeping indoors, awake indoors, and outdoors. Hourly variations in biting activity by members of the Anopheles gambiae complex were consistent with classical reports but the proportion of these vectors caught outdoors in Dar es Salaam was almost double that of rural Tanzania. Overall, ITNs confer less protection against exophagic vectors in Dar es Salaam than in rural southern Tanzania (59% versus 70%). More alarmingly, a biting activity maximum that precedes 10 pm and much lower levels of ITN protection against exposure (38%) were observed for Anopheles arabiensis, a vector of modest importance locally, but which predominates transmission in large parts of Africa. In a situation of changing mosquito and human behaviour, ITNs may confer lower, but still useful, levels of personal protection which can be complemented by communal transmission suppression at high coverage. Mosquito-proofing houses appeared to be the intervention of choice amongst residents and further options for preventing outdoor transmission include larviciding and environmental management.

The development of insecticide-treated durable wall lining for malaria control: insights from rural and urban populations in Angola and Nigeria

PubMed Central

2012-01-01

Background Durable lining (DL) is a deltamethrin-impregnated polyethylene material, which is designed to cover domestic walls that would normally be sprayed with residual insecticide. The operational success of DL as a long-lasting insecticidal substrate will be dependent on a high level of user acceptability as households must maintain correctly installed linings on their walls for several years. Preliminary trials were undertaken to identify a material to develop into a marketable wall lining and to assess its level of acceptability among rural and urban populations. Methods In Angola (n=60), prototype DL and insecticide-treated plastic sheeting (ITPS) were installed on urban house walls and ceilings, respectively, and acceptability was compared to indoor residual spraying (IRS) (n=20) using a knowledge, attitude and practice (KAP) questionnaire. In Nigeria (n=178), three materials (prototype DL, ITPS and insecticide-treated wall netting) were distributed among rural and urban households. User opinions were gathered from focus group discussions, in-depth interviews and KAP questionnaires. Results In Angola, after two weeks, the majority of participants (98%) expressed satisfaction with the products and identified the killing of insects as the materials’ principal benefits (73%). After one year, despite a loss of almost 50% of households to refugee repatriation, all 32 remaining households still asserted that they had liked the DL/ITPS in their homes and given the choice of intervention preferred DL/ITPS to IRS (94%) or insecticide-treated nets (78%). In Nigeria, a dichotomy between rural and urban respondents emerged. Rural participants favoured wall adornments and accepted wall linings because of their perceived decorative value and entomological efficacy. By contrast, urban households preferred minimal wall decoration and rejected the materials based upon objections to their aesthetics and installation feasibility. Conclusions The high level of acceptability

Persistent oscillations and backward bifurcation in a malaria model with varying human and mosquito populations: implications for control.

PubMed

Ngonghala, Calistus N; Teboh-Ewungkem, Miranda I; Ngwa, Gideon A

2015-06-01

We derive and study a deterministic compartmental model for malaria transmission with varying human and mosquito populations. Our model considers disease-related deaths, asymptomatic immune humans who are also infectious, as well as mosquito demography, reproduction and feeding habits. Analysis of the model reveals the existence of a backward bifurcation and persistent limit cycles whose period and size is determined by two threshold parameters: the vectorial basic reproduction number Rm, and the disease basic reproduction number R0, whose size can be reduced by reducing Rm. We conclude that malaria dynamics are indeed oscillatory when the methodology of explicitly incorporating the mosquito's demography, feeding and reproductive patterns is considered in modeling the mosquito population dynamics. A sensitivity analysis reveals important control parameters that can affect the magnitudes of Rm and R0, threshold quantities to be taken into consideration when designing control strategies. Both Rm and the intrinsic period of oscillation are shown to be highly sensitive to the mosquito's birth constant λm and the mosquito's feeding success probability pw. Control of λm can be achieved by spraying, eliminating breeding sites or moving them away from human habitats, while pw can be controlled via the use of mosquito repellant and insecticide-treated bed-nets. The disease threshold parameter R0 is shown to be highly sensitive to pw, and the intrinsic period of oscillation is also sensitive to the rate at which reproducing mosquitoes return to breeding sites. A global sensitivity and uncertainty analysis reveals that the ability of the mosquito to reproduce and uncertainties in the estimations of the rates at which exposed humans become infectious and infectious humans recover from malaria are critical in generating uncertainties in the disease classes.

The Effect of Single or Repeated Home Visits on the Hanging and Use of Insecticide-Treated Mosquito Nets following a Mass Distribution Campaign - A Cluster Randomized, Controlled Trial

PubMed Central

Kilian, Albert; Balayo, Connie; Feldman, Mitra; Koenker, Hannah; Lokko, Kojo; Ashton, Ruth A.; Bruce, Jane; Lynch, Matthew; Boulay, Marc

2015-01-01

Background Study objective was to evaluate the effectiveness of commonly used post-campaign hang-up visits on the hanging and use of campaign nets. Methods A cluster-randomized trial was carried out in Uganda following an ITN distribution campaign. Five clusters (parishes, consisting of ∼11 villages each) were randomly selected for each of the three study arms with between 7,534 and 9,401 households per arm. Arm 1 received one hang-up visit, while Arm 2 received two visits by volunteers four and seven months after the campaign. Visits consisted of assistance hanging the net and education on net use. The control arm was only exposed to messages during the campaign itself. Three cross-sectional surveys with a two-stage cluster sampling design, representative of the study populations, were carried out to capture the two key outcome variables of net hanging and ITN use. Sample size was calculated to detect at least a 15 percentage-points change in net use, and was 1811 at endline. The analysis used an intention-to-treat approach. Findings Both hanging and use of ITN increased during follow-up in a similar way in all three study arms. The proportion of the population using an ITN the previous night was 64.0% (95% CI 60.8, 67.2), for one additional visit, 68.2% (63.8, 72.2) for two visits and 64.0% (59.4, 68.5) for the control. The proportion of households with all campaign nets hanging increased from 55.7% to 72.5% at endline (p<0.0005 for trend), with no difference between study arms. Financial cost per household visited was estimated as USD 2.33 for the first visit and USD 2.24 for the second. Conclusions Behavior change communication provided during the campaign or through other channels was sufficient to induce high levels of net hanging and use and additional “hang-up” activities were not cost-effective. PMID:25774676

Evaluation of new tools for malaria vector control in Cameroon: focus on long lasting insecticidal nets.

PubMed

Etang, Josiane; Nwane, Philippe; Piameu, Michael; Manga, Blaise; Souop, Daniel; Awono-Ambene, Parfait

2013-01-01

From 2006 to 2011, biological activity of insecticides for Indoor Residual Spraying (IRS), conventional treatment of nets (CTNs) or long lasting insecticidal nets (LLINs) was evaluated before their approval in Cameroon. The objective of the study was to select the best tools for universal malaria vector control coverage. Bioassays were performed using WHO cones and the Kisumu susceptible strain of Anopheles gambiae s.s.. Among tested products, residual activity and wash resistance of Alpha-cypermethrin LLINs (Interceptor) and CTNs (Fendona) were assessed during 5 months in the Ntougou neighborhood. All the 14 tested products were found effective (95-100% knockdown and mortality rates), although a significant decrease of efficacy was seen with lambda-cyhalothrinWP IRS, alpha-cypermethrin CTNs and LLINs (p< 0.05). However, the efficacy of Interceptor nets did not decrease during the 5 months evaluation, even after 25 washes (0.07nets displayed a drastic decrease of activity after 5 washes, odds ratio was 3.07 (1.0-8.59). This study provided useful data for decision making and community education toward universal coverage of malaria vector control in Cameroon.

Evaluation of New Tools for Malaria Vector Control in Cameroon: Focus on Long Lasting Insecticidal Nets

PubMed Central

Etang, Josiane; Nwane, Philippe; Piameu, Michael; Manga, Blaise; Souop, Daniel; Awono-Ambene, Parfait

2013-01-01

Background From 2006 to 2011, biological activity of insecticides for Indoor Residual Spraying (IRS), conventional treatment of nets (CTNs) or long lasting insecticidal nets (LLINs) was evaluated before their approval in Cameroon. The objective of the study was to select the best tools for universal malaria vector control coverage. Methodology Bioassays were performed using WHO cones and the Kisumu susceptible strain of Anopheles gambiae s.s.. Among tested products, residual activity and wash resistance of Alpha-cypermethrin LLINs (Interceptor) and CTNs (Fendona) were assessed during 5 months in the Ntougou neighborhood. Principal Findings All the 14 tested products were found effective (95–100% knockdown and mortality rates), although a significant decrease of efficacy was seen with lambda-cyhalothrinWP IRS, alpha-cypermethrin CTNs and LLINs (p< 0.05). However, the efficacy of Interceptor nets did not decrease during the 5 months evaluation, even after 25 washes (0.07nets displayed a drastic decrease of activity after 5 washes, odds ratio was 3.07 (1.0–8.59). Conclusion This study provided useful data for decision making and community education toward universal coverage of malaria vector control in Cameroon. PMID:24086399

Pyrethroid Resistance Alters the Blood-Feeding Behavior in Puerto Rican Aedes aegypti Mosquitoes Exposed to Treated Fabric

USDA-ARS?s Scientific Manuscript database

Emerging insecticide resistance is a major issue for vector control; it decreases effectiveness of insecticides, thereby requiring greater quantities for comparable control with a net increase in risk of disease resurgence, product cost, and damage risk to the ecosystem. Pyrethroid resistance has b...

Use of butterflies as nontarget insect test species and the acute toxicity and hazard of mosquito control insecticides.

PubMed

Hoang, Tham C; Pryor, Rachel L; Rand, Gary M; Frakes, Robert A

2011-04-01

Honeybees are the standard insect test species used for toxicity testing of pesticides on nontarget insects for the U.S. Environmental Protection Agency (U.S. EPA) under the Federal Insecticide Fungicide and Rodenticide Act (FIFRA). Butterflies are another important insect order and a valued ecological resource in pollination. The current study conducted acute toxicity tests with naled, permethrin, and dichlorvos on fifth larval instar (caterpillars) and adults of different native Florida, USA, butterfly species to determine median lethal doses (24-h LD50), because limited acute toxicity data are available with this major insect group. Thorax- and wing-only applications of each insecticide were conducted. Based on LD50s, thorax and wing application exposures were acutely toxic to both caterpillars and adults. Permethrin was the most acutely toxic insecticide after thorax exposure to fifth instars and adult butterflies. However, no generalization on acute toxicity (sensitivity) of the insecticides could be concluded based on exposures to fifth instars versus adult butterflies or on thorax versus wing exposures of adult butterflies. A comparison of LD50s of the butterflies from this study (caterpillars and adults) with honeybee LD50s for the adult mosquito insecticides on a µg/organism or µg/g basis indicates that several butterfly species are more sensitive to these insecticides than are honeybees. A comparison of species sensitivity distributions for all three insecticides shows that permethrin had the lowest 10th percentile. Using a hazard quotient approach indicates that both permethrin and naled applications in the field may present potential acute hazards to butterflies, whereas no acute hazard of dichlorvos is apparent in butterflies. Butterflies should be considered as potential test organisms when nontarget insect testing of pesticides is suggested under FIFRA. Copyright © 2011 SETAC.

Prevention of malaria in Afghanistan through social marketing of insecticide-treated nets: evaluation of coverage and effectiveness by cross-sectional surveys and passive surveillance.

PubMed

Rowland, Mark; Webster, Jayne; Saleh, Padshah; Chandramohan, Daniel; Freeman, Tim; Pearcy, Barbara; Durrani, Naeem; Rab, Abdur; Mohammed, Nasir

2002-10-01

Malaria is often a major health problem in countries undergoing war or conflict owing to breakdown of health systems, displacement of vulnerable populations, and the increased risk of epidemics. After 23 years of conflict, malaria has become prevalent in many rural areas of Afghanistan. From 1993 to the present, a network of non-governmental organizations, co-ordinated by HealthNet International, has operated a programme of bednet sales and re-treatment in lowland areas. To examine whether a strategy based on insecticide-treated nets (ITN) is a viable public health solution to malaria, communities were given the opportunity to buy nets and then monitored to determine population coverage and disease control impact. This was carried out using two contrasting methods: cross-sectional surveys and passive surveillance from clinics using a case-control design. Nets were purchased by 59% of families. Cross-sectional surveys demonstrated a 59% reduction in the risk of Plasmodium falciparum infection among ITN users compared with non-users (OR 0.41; 95% CI 0.25-0.66). The passive surveillance method showed a comparable reduction in the risk of symptomatic P. falciparum malaria among ITN users (OR 0.31; 95% CI 0.21-0.47). The cross-sectional method showed a 50% reduction in risk of P. vivax infection in ITN users compared with non-users (OR 0.50; 95% CI 0.17-1.49) but this effect was not statistically significant. The passive surveillance method showed a 25% reduction in the risk of symptomatic P. vivax malaria (OR 0.75; 95% CI 0.66-0.85). ITN appeared to be less effective against P. vivax because of relapsing infections; hence an effect took more than one season to become apparent. Passive surveillance was cheaper to perform and gave results consistent with cross-sectional surveys. Untreated nets provided some protection. Data on socioeconomic status, a potential confounding factor, was not collected. However, at the time of net sales, there was no difference in malaria

What Is Threatening the Effectiveness of Insecticide-Treated Bednets? A Case-Control Study of Environmental, Behavioral, and Physical Factors Associated with Prevention Failure.

PubMed

Obala, Andrew A; Mangeni, Judith Nekesa; Platt, Alyssa; Aswa, Daniel; Abel, Lucy; Namae, Jane; Prudhomme O'Meara, Wendy

2015-01-01

Insecticide-treated nets are the cornerstone of global malaria control and have been shown to reduce malaria morbidity by 50-60%. However, some areas are experiencing a resurgence in malaria following successful control. We describe an efficacy decay framework to understand why high malaria burden persists even under high ITN coverage in a community in western Kenya. We enrolled 442 children hospitalized with malaria and paired them with age, time, village and gender-matched controls. We completed comprehensive household and neighborhood assessments including entomological surveillance. The indicators are grouped into five domains in an efficacy decay framework: ITN ownership, compliance, physical integrity, vector susceptibility and facilitating factors. After variable selection, case-control data were analyzed using conditional logistic regression models and mosquito data were analyzed using negative binomial regression. Predictive margins were calculated from logistic regression models. Measures of ITN coverage and physical integrity were not correlated with hospitalized malaria in our study. However, consistent ITN use (Adjusted Odds Ratio (AOR) = 0.23, 95%CI: 0.12-0.43), presence of nearby larval sites (AOR = 1.137, 95%CI: 1.02-1.27), and specific types of crops (AOR (grains) = 0.446, 95%CI: 0.24-0.82) were significantly correlated with malaria amongst children who owned an ITN. The odds of hospitalization for febrile malaria nearly tripled when one other household member had symptomatic malaria infection (AOR-2.76, 95%CI:1.83-4.18). Overall, perfect household adherence could reduce the probability of hospitalization for malaria to less than 30% (95%CI:0.12-0.46) and adjusting environmental factors such as elimination of larval sites and growing grains nearby could reduce the probability of hospitalization for malaria to less than 20% (95%CI:0.04-0.31). Availability of ITNs is not the bottleneck for malaria prevention in this community. Behavior change

Novel Methods for Mosquito Control using RNAi.

USDA-ARS?s Scientific Manuscript database

The discovery and development of novel insecticides for vector control is a primary focus of toxicology research conducted at the Mosquito and Fly Research Unit, Gainesville, FL. Targeting critical genes/proteins in mosquitoes using RNA interference (RNAi) is being investigated as a method to devel...

Pyrethroid resistance in Anopheles gambiae leads to increased susceptibility to the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana

PubMed Central

2010-01-01

Background Entomopathogenic fungi are being investigated as a new mosquito control tool because insecticide resistance is preventing successful mosquito control in many countries, and new methods are required that can target insecticide-resistant malaria vectors. Although laboratory studies have previously examined the effects of entomopathogenic fungi against adult mosquitoes, most application methods used cannot be readily deployed in the field. Because the fungi are biological organisms it is important to test potential field application methods that will not adversely affect them. The two objectives of this study were to investigate any differences in fungal susceptibility between an insecticide-resistant and insecticide-susceptible strain of Anopheles gambiae sensu stricto, and to test a potential field application method with respect to the viability and virulence of two fungal species Methods Pieces of white polyester netting were dipped in Metarhizium anisopliae ICIPE-30 or Beauveria bassiana IMI391510 mineral oil suspensions. These were kept at 27 ± 1°C, 80 ± 10% RH and the viability of the fungal conidia was recorded at different time points. Tube bioassays were used to infect insecticide-resistant (VKPER) and insecticide-susceptible (SKK) strains of An. gambiae s.s., and survival analysis was used to determine effects of mosquito strain, fungus species or time since fungal treatment of the net. Results The resistant VKPER strain was significantly more susceptible to fungal infection than the insecticide-susceptible SKK strain. Furthermore, B. bassiana was significantly more virulent than M. anisopliae for both mosquito strains, although this may be linked to the different viabilities of these fungal species. The viability of both fungal species decreased significantly one day after application onto polyester netting when compared to the viability of conidia remaining in suspension. Conclusions The insecticide-resistant mosquito strain was susceptible

Trifluoromethylphenyl amides as novel insecticides and fungicides

USDA-ARS?s Scientific Manuscript database

Because of increased resistance to insecticides in arthropods, it is necessary to identify new chemicals that may have novel modes of action. Following an extensive literature search for compounds with insecticidal and mosquito repellent activity, we have designed and synthesized a set of 20 trif...

Trifluoromethylphenyl amides as novel insecticides and fungicides

USDA-ARS?s Scientific Manuscript database

Because of increased resistance to insecticides in arthropods, it is necessary to identify new chemicals that may have novel modes of action. Following an extensive literature search for compounds with insecticidal and mosquito repellent activity, we have designed and synthesized a set of 20 trifluo...

Trifluoromethylphenyl amides as novel insecticides and fungicides

USDA-ARS?s Scientific Manuscript database

Because of increased resistance to insecticides in arthropods, it is necessary to identify new chemicals that may have novel modes of action. Following an extensive literature search for compounds with insecticidal and mosquito repellent activity, we have designed and synthesized a set of 20 triflu...

Gender and willingness to pay for insecticides treated bed nets in a poor rural area in Tanzania.

PubMed

Mujinja, P G M; Makwaya, C K; Sauerborn, R

2004-12-01

To examine socio-economic and malaria related differences between males and females that may cause gender differences in willingness to pay (WTP) for insecticide treated bed nets in a poor rural area. A two-week-interval (test re-test) cross-sectional study. Kisarawe District in coastal Tanzania. Two hundred and fifty one males and two hundred dollars females were interviewed. Females had about 50% of the males' income. The monthly average income was about US dollars 10.50 for females and US dollars 20.20 for males. The proportion of respondents willing to pay for an ITN, for both males and females, declined as the ITN prices increased (P<0.05). The mean maximum WTP difference between men and women, between both rounds were not statistically significant (p>0.05). Male respondents reported a higher mean number of own underfives living in the household compared to women, the difference was not statistically significant (P>0.8). Willingness to pay for ITN was found to be independent of having an under five child with recent history of malaria. Among both males and females, there was an association between a recent experience with malaria episode and WTP, p=0.05 and p=0.02 respectively. Among females, the proportion of those willing to pay for another person, at the lowest ITN price, was significantly higher in those with under five children in their households than in those with no underfives. This was not the case among the male respondents as the association was not statistically significant. Contrary to expectations were was no statistically significant difference in WTP for an ITN between females and males. Further studies that link willingness and ability to pay are required in rural poor population, such studies may be valuable inputs to government policy on and planning of ITN interventions in the public and private sector.

Numerical modeling of mosquito population dynamics of Aedes aegypti.

PubMed

Yamashita, William M S; Das, Shyam S; Chapiro, Grigori

2018-04-16

The global incidences of dengue virus have increased the interest in studying and understanding the mosquito population dynamics. It is predominantly spread by Aedes aegypti in the tropical and sub-tropical countries in the world. Understanding these dynamics is important for public health in countries where climatic and environmental conditions are favorable for the propagation of these diseases. For this reason, a new model has been proposed to investigate the population dynamics of mosquitoes in a city. The present paper discusses the numerical modeling of population dynamics of Ae. aegypti mosquitoes in an urban neighborhood of a city using the finite volume method. The model describes how populations spread through the city assisted by the wind. This model allows incorporating external factors (wind and chemical insecticides) and topography data (streets, building blocks, parks, forests and beach). The proposed model has been successfully tested in examples involving two Brazilian cities (City center, Juiz de Fora and Copacabana Beach, Rio de Janeiro). Invasion phenomena of Ae. aegypti mosquitoes have been observed in each of the simulations. It was observed that, inside the blocks, the growth of the population for both winged and aquatic phase causes an infestation of Ae. aegypti in a short time. Within the blocks the mosquito population was concentrated and diffused slowly. In the streets, there was a long-distance spread, which was influenced by wind and diffusion with a low concentration of mosquito population. The model was also tested taking into account chemical insecticides spread in two different configurations. It has been observed that the insecticides have a significant effect on the mosquito population for both winged and aquatic phases when the chemical insecticides spread more uniformly along all the streets in a neighborhood of a city. The presented methodology can be employed to evaluate and to understand the epidemic risks in a specific

Insecticide-treated durable wall lining (ITWL): future prospects for control of malaria and other vector-borne diseases.

PubMed

Messenger, Louisa A; Rowland, Mark

2017-05-22

While long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the cornerstones of malaria vector control throughout sub-Saharan Africa, there is an urgent need for the development of novel insecticide delivery mechanisms to sustain and consolidate gains in disease reduction and to transition towards malaria elimination and eradication. Insecticide-treated durable wall lining (ITWL) may represent a new paradigm for malaria control as a potential complementary or alternate longer-lasting intervention to IRS. ITWL can be attached to inner house walls, remain efficacious over multiple years and overcome some of the operational constraints of first-line control strategies, specifically nightly behavioural compliance required of LLINs and re-current costs and user fatigue associated with IRS campaigns. Initial experimental hut trials of insecticide-treated plastic sheeting reported promising results, achieving high levels of vector mortality, deterrence and blood-feeding inhibition, particularly when combined with LLINs. Two generations of commercial ITWL have been manufactured to date containing either pyrethroid or non-pyrethroid formulations. While some Phase III trials of these products have demonstrated reductions in malaria incidence, further large-scale evidence is still required before operational implementation of ITWL can be considered either in a programmatic or more targeted community context. Qualitative studies of ITWL have identified aesthetic value and observable entomological efficacy as key determinants of household acceptability. However, concerns have been raised regarding installation feasibility and anticipated cost-effectiveness. This paper critically reviews ITWL as both a putative mechanism of house improvement or more conventional intervention and discusses its future prospects as a method for controlling malaria and other vector-borne diseases.

Effects of truck-mounted, ultra low volume mosquito adulticides on honey bees (Apis mellifera) in a suburban field setting

PubMed Central

DeLisi, Nicholas A.; Danka, Robert G.; Walker, Todd W.; Ottea, James A.; Healy, Kristen B.

2018-01-01

Few studies have examined the impact of mosquito adulticides on honey bees under conditions that reflect actual field exposure. Whereas several studies have evaluated the toxicity of mosquito control products on honey bees, most have been laboratory based and have focused solely on acute mortality as a measure of impact. The goal of this study was to determine effects of routine applications of truck-based ultra-low volume (ULV) mosquito adulticides (i.e., Scourge, Duet, and Deltagard) on honey bees in a suburban setting. The mosquito adulticides used in this study were pyrethroids with active ingredients resmethrin (Scourge), prallethrin and sumithrin (Duet), and deltamethrin (Deltagard), in which resmethrin, prallethrin, and sumithrin were synergized with piperonyl butoxide. We measured and compared mortality and detoxification enzyme activities (esterase and glutathione S-transferase) from sentinel beehives within and outside of mosquito control areas. Concurrently, colony health (i.e., number of adult bees, brood quantity and brood quality) was compared throughout the study period. No significant differences were observed in honey bee mortality, colony health or detoxification enzyme activities between treated (five sprayed areas each received one to three insecticide treatment) and control sites (four unsprayed areas that did not receive insecticide treatment) over the seven week study period. However, our laboratory study showed that exposure to resmethrin, the active ingredient in Scourge, caused significant inhibition of esterase activity compared with the control group. Our findings suggest that proper application of truck based insecticides for mosquito control results in little or no exposure and therefore minimal effects on domestic honey bees. PMID:29494661

Effects of truck-mounted, ultra low volume mosquito adulticides on honey bees (Apis mellifera) in a suburban field setting.

PubMed

Pokhrel, Vivek; DeLisi, Nicholas A; Danka, Robert G; Walker, Todd W; Ottea, James A; Healy, Kristen B

2018-01-01

Few studies have examined the impact of mosquito adulticides on honey bees under conditions that reflect actual field exposure. Whereas several studies have evaluated the toxicity of mosquito control products on honey bees, most have been laboratory based and have focused solely on acute mortality as a measure of impact. The goal of this study was to determine effects of routine applications of truck-based ultra-low volume (ULV) mosquito adulticides (i.e., Scourge, Duet, and Deltagard) on honey bees in a suburban setting. The mosquito adulticides used in this study were pyrethroids with active ingredients resmethrin (Scourge), prallethrin and sumithrin (Duet), and deltamethrin (Deltagard), in which resmethrin, prallethrin, and sumithrin were synergized with piperonyl butoxide. We measured and compared mortality and detoxification enzyme activities (esterase and glutathione S-transferase) from sentinel beehives within and outside of mosquito control areas. Concurrently, colony health (i.e., number of adult bees, brood quantity and brood quality) was compared throughout the study period. No significant differences were observed in honey bee mortality, colony health or detoxification enzyme activities between treated (five sprayed areas each received one to three insecticide treatment) and control sites (four unsprayed areas that did not receive insecticide treatment) over the seven week study period. However, our laboratory study showed that exposure to resmethrin, the active ingredient in Scourge, caused significant inhibition of esterase activity compared with the control group. Our findings suggest that proper application of truck based insecticides for mosquito control results in little or no exposure and therefore minimal effects on domestic honey bees.

Interactive cost of Plasmodium infection and insecticide resistance in the malaria vector Anopheles gambiae.

PubMed

Alout, Haoues; Dabiré, Roch K; Djogbénou, Luc S; Abate, Luc; Corbel, Vincent; Chandre, Fabrice; Cohuet, Anna

2016-07-19

Insecticide resistance raises concerns for the control of vector-borne diseases. However, its impact on parasite transmission could be diverse when considering the ecological interactions between vector and parasite. Thus we investigated the fitness cost associated with insecticide resistance and Plasmodium falciparum infection as well as their interactive cost on Anopheles gambiae survival and fecundity. In absence of infection, we observed a cost on fecundity associated with insecticide resistance. However, survival was higher for mosquito bearing the kdr mutation and equal for those with the ace-1(R) mutation compared to their insecticide susceptible counterparts. Interestingly, Plasmodium infection reduced survival only in the insecticide resistant strains but not in the susceptible one and infection was associated with an increase in fecundity independently of the strain considered. This study provides evidence for a survival cost associated with infection by Plasmodium parasite only in mosquito selected for insecticide resistance. This suggests that the selection of insecticide resistance mutation may have disturbed the interaction between parasites and vectors, resulting in increased cost of infection. Considering the fitness cost as well as other ecological aspects of this natural mosquito-parasite combination is important to predict the epidemiological impact of insecticide resistance.

Interventions that effectively target Anopheles funestus mosquitoes could significantly improve control of persistent malaria transmission in south-eastern Tanzania.

PubMed

Kaindoa, Emmanuel W; Matowo, Nancy S; Ngowo, Halfan S; Mkandawile, Gustav; Mmbando, Arnold; Finda, Marcelina; Okumu, Fredros O

2017-01-01

Malaria is transmitted by many Anopheles species whose proportionate contributions vary across settings. We re-assessed the roles of Anopheles arabiensis and Anopheles funestus, and examined potential benefits of species-specific interventions in an area in south-eastern Tanzania, where malaria transmission persists, four years after mass distribution of long-lasting insecticide-treated nets (LLINs). Monthly mosquito sampling was done in randomly selected households in three villages using CDC light traps and back-pack aspirators, between January-2015 and January-2016, four years after the last mass distribution of LLINs in 2011. Multiplex polymerase chain reaction (PCR) was used to identify members of An. funestus and Anopheles gambiae complexes. Enzyme-linked immunosorbent assay (ELISA) was used to detect Plasmodium sporozoites in mosquito salivary glands, and to identify sources of mosquito blood meals. WHO susceptibility assays were done on wild caught female An. funestus s.l, and physiological ages approximated by examining mosquito ovaries for parity. A total of 20,135 An. arabiensis and 4,759 An. funestus were collected. The An. funestus group consisted of 76.6% An. funestus s.s, 2.9% An. rivulorum, 7.1% An. leesoni, and 13.4% unamplified samples. Of all mosquitoes positive for Plasmodium, 82.6% were An. funestus s.s, 14.0% were An. arabiensis and 3.4% were An. rivulorum. An. funestus and An. arabiensis contributed 86.21% and 13.79% respectively, of annual entomological inoculation rate (EIR). An. arabiensis fed on humans (73.4%), cattle (22.0%), dogs (3.1%) and chicken (1.5%), but An. funestus fed exclusively on humans. The An. funestus populations were 100% susceptible to organophosphates, pirimiphos methyl and malathion, but resistant to permethrin (10.5% mortality), deltamethrin (18.7%), lambda-cyhalothrin (18.7%) and DDT (26.2%), and had reduced susceptibility to bendiocarb (95%) and propoxur (90.1%). Parity rate was higher in An. funestus (65.8%) than

Interventions that effectively target Anopheles funestus mosquitoes could significantly improve control of persistent malaria transmission in south–eastern Tanzania

PubMed Central

Matowo, Nancy S.; Ngowo, Halfan S.; Mkandawile, Gustav; Mmbando, Arnold; Finda, Marcelina; Okumu, Fredros O.

2017-01-01

Malaria is transmitted by many Anopheles species whose proportionate contributions vary across settings. We re-assessed the roles of Anopheles arabiensis and Anopheles funestus, and examined potential benefits of species-specific interventions in an area in south-eastern Tanzania, where malaria transmission persists, four years after mass distribution of long-lasting insecticide-treated nets (LLINs). Monthly mosquito sampling was done in randomly selected households in three villages using CDC light traps and back-pack aspirators, between January-2015 and January-2016, four years after the last mass distribution of LLINs in 2011. Multiplex polymerase chain reaction (PCR) was used to identify members of An. funestus and Anopheles gambiae complexes. Enzyme-linked immunosorbent assay (ELISA) was used to detect Plasmodium sporozoites in mosquito salivary glands, and to identify sources of mosquito blood meals. WHO susceptibility assays were done on wild caught female An. funestus s.l, and physiological ages approximated by examining mosquito ovaries for parity. A total of 20,135 An. arabiensis and 4,759 An. funestus were collected. The An. funestus group consisted of 76.6% An. funestus s.s, 2.9% An. rivulorum, 7.1% An. leesoni, and 13.4% unamplified samples. Of all mosquitoes positive for Plasmodium, 82.6% were An. funestus s.s, 14.0% were An. arabiensis and 3.4% were An. rivulorum. An. funestus and An. arabiensis contributed 86.21% and 13.79% respectively, of annual entomological inoculation rate (EIR). An. arabiensis fed on humans (73.4%), cattle (22.0%), dogs (3.1%) and chicken (1.5%), but An. funestus fed exclusively on humans. The An. funestus populations were 100% susceptible to organophosphates, pirimiphos methyl and malathion, but resistant to permethrin (10.5% mortality), deltamethrin (18.7%), lambda-cyhalothrin (18.7%) and DDT (26.2%), and had reduced susceptibility to bendiocarb (95%) and propoxur (90.1%). Parity rate was higher in An. funestus (65.8%) than

The effect of insecticide-treated bed nets on the incidence and prevalence of malaria in children in an area of unstable seasonal transmission in western Myanmar

PubMed Central

2013-01-01

Background Insecticide-treated bed nets (ITN) reduce malaria morbidity and mortality consistently in Africa, but their benefits have been less consistent in Asia. This study’s objective was to evaluate the malaria protective efficacy of village-wide usage of ITN in Western Myanmar and estimate the cost-effectiveness of ITN compared with extending early diagnosis and treatment services. Methods A cluster-randomized controlled trial was conducted in Rakhine State to assess the efficacy of ITNs in preventing malaria and anaemia in children and their secondary effects on nutrition and development. The data were aggregated for each village to obtain cluster-level infection rates. In total 8,175 children under 10 years of age were followed up for 10 months, which included the main malaria transmission period. The incidence and prevalence of Plasmodium falciparum and Plasmodium vivax infections, and the biting behaviour of Anopheles mosquitoes in the area were studied concurrently. The trial data along with costs for current recommended treatment practices were modelled to estimate the cost-effectiveness of ITNs compared with, or in addition to extending the coverage of early diagnosis and treatment services. Results In aggregate, malaria infections, spleen rates, haemoglobin concentrations, and weight for height, did not differ significantly during the study period between villages with and without ITNs, with a weighted mean difference of −2.6 P. falciparum episodes per 1,000 weeks at risk (95% Confidence Interval −7 to 1.8). In areas with a higher incidence of malaria there was some evidence ITN protective efficacy. The economic analysis indicated that, despite the uncertainty and variability in their protective efficacy in the different study sites, ITN could still be cost-effective, but not if they displaced funding for early diagnosis and effective treatment which is substantially more cost-effective. Conclusion In Western Myanmar deployment of ITNs did not

The effect of insecticide-treated bed nets on the incidence and prevalence of malaria in children in an area of unstable seasonal transmission in western Myanmar.

PubMed

Smithuis, Frank M; Kyaw, Moe Kyaw; Phe, U Ohn; van der Broek, Ingrid; Katterman, Nina; Rogers, Colin; Almeida, Patrick; Kager, Piet A; Stepniewska, Kasia; Lubell, Yoel; Simpson, Julie A; White, Nicholas J

2013-10-11

Insecticide-treated bed nets (ITN) reduce malaria morbidity and mortality consistently in Africa, but their benefits have been less consistent in Asia. This study's objective was to evaluate the malaria protective efficacy of village-wide usage of ITN in Western Myanmar and estimate the cost-effectiveness of ITN compared with extending early diagnosis and treatment services. A cluster-randomized controlled trial was conducted in Rakhine State to assess the efficacy of ITNs in preventing malaria and anaemia in children and their secondary effects on nutrition and development. The data were aggregated for each village to obtain cluster-level infection rates. In total 8,175 children under 10 years of age were followed up for 10 months, which included the main malaria transmission period. The incidence and prevalence of Plasmodium falciparum and Plasmodium vivax infections, and the biting behaviour of Anopheles mosquitoes in the area were studied concurrently. The trial data along with costs for current recommended treatment practices were modelled to estimate the cost-effectiveness of ITNs compared with, or in addition to extending the coverage of early diagnosis and treatment services. In aggregate, malaria infections, spleen rates, haemoglobin concentrations, and weight for height, did not differ significantly during the study period between villages with and without ITNs, with a weighted mean difference of -2.6 P. falciparum episodes per 1,000 weeks at risk (95% Confidence Interval -7 to 1.8). In areas with a higher incidence of malaria there was some evidence ITN protective efficacy. The economic analysis indicated that, despite the uncertainty and variability in their protective efficacy in the different study sites, ITN could still be cost-effective, but not if they displaced funding for early diagnosis and effective treatment which is substantially more cost-effective. In Western Myanmar deployment of ITNs did not provide consistent protection against malaria

Multi-country comparison of delivery strategies for mass campaigns to achieve universal coverage with insecticide-treated nets: what works best?