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Sample records for trypanosomiasis vector control

  1. Trypanosomiasis vector control in Africa and Latin America

    PubMed Central

    Schofield, Chris J; Kabayo, John P

    2008-01-01

    Vectors of trypanosomiasis – tsetse (Glossinidae) in Africa, kissing-bugs (Triatominae) in Latin America – are very different insects but share demographic characteristics that render them highly vulnerable to available control methods. For both, the main operational problems relate to re-invasion of treated areas, and the solution seems to be in very large-scale interventions covering biologically-relevant areas rather than adhering to administrative boundaries. In this review we present the underlying rationale, operational background and progress of the various trypanosomiasis vector control initiatives active in both continents. PMID:18673535

  2. Evaluating paratransgenesis as a potential control strategy for African trypanosomiasis.

    PubMed

    Medlock, Jan; Atkins, Katherine E; Thomas, David N; Aksoy, Serap; Galvani, Alison P

    2013-01-01

    Genetic-modification strategies are currently being developed to reduce the transmission of vector-borne diseases, including African trypanosomiasis. For tsetse, the vector of African trypanosomiasis, a paratransgenic strategy is being considered: this approach involves modification of the commensal symbiotic bacteria Sodalis to express trypanosome-resistance-conferring products. Modified Sodalis can then be driven into the tsetse population by cytoplasmic incompatibility (CI) from Wolbachia bacteria. To evaluate the effectiveness of this paratransgenic strategy in controlling African trypanosomiasis, we developed a three-species mathematical model of trypanosomiasis transmission among tsetse, humans, and animal reservoir hosts. Using empirical estimates of CI parameters, we found that paratransgenic tsetse have the potential to eliminate trypanosomiasis, provided that any extra mortality caused by Wolbachia colonization is low, that the paratransgene is effective at protecting against trypanosome transmission, and that the target tsetse species comprises a large majority of the tsetse population in the release location.

  3. Control and surveillance of human African trypanosomiasis.

    PubMed

    2013-01-01

    In the 1960s, it appeared that human African trypanosomiasis (HAT) could be effectively controlled, but by the beginning of the twenty-first century several decades of neglect had led to alarming numbers of reported new cases, with an estimated 300 000 people infected. The World Health Organization (WHO) responded with a series of initiatives aimed at bringing HAT under control again. Since 2001, the pharmaceutical companies that produce drugs for HAT have committed themselves to providing them free of charge to WHO for distribution for the treatment of patients. In addition, funds have been provided to WHO to support national sleeping sickness control programmes to boost control and surveillance of the disease. That, coupled with bilateral cooperation and the work of nongovernmental organizations, helped reverse the upward trend in HAT prevalence. By 2012, the number of reported cases was fewer than 8000. This success in bringing HAT under control led to its inclusion in the WHO Roadmap for eradication, elimination and control of neglected tropical diseases, with a target set to eliminate the disease as a public health problem by 2020. A further target has been set, by countries in which HAT is endemic, to eliminate gambiense HAT by reducing the incidence of infection to zero in a defined geographical area. This report provides information about new diagnostic approaches, new therapeutic regimens and better understanding of the distribution of the disease with high-quality mapping. The roles of human and animal reservoirs and the tsetse fly vectors that transmit the parasites are emphasized. The new information has formed the basis for an integrated strategy with which it is hoped that elimination of gambiense HAT will be achieved. The report also contains recommendations on the approaches that will lead to elimination of the disease.

  4. Prospects for developing odour baits to control Glossina fuscipes spp., the major vector of human African trypanosomiasis.

    PubMed

    Omolo, Maurice O; Hassanali, Ahmed; Mpiana, Serge; Esterhuizen, Johan; Lindh, Jenny; Lehane, Mike J; Solano, Philippe; Rayaisse, Jean Baptiste; Vale, Glyn A; Torr, Steve J; Tirados, Inaki

    2009-01-01

    We are attempting to develop cost-effective control methods for the important vector of sleeping sickness, Glossina fuscipes spp. Responses of the tsetse flies Glossina fuscipes fuscipes (in Kenya) and G. f. quanzensis (in Democratic Republic of Congo) to natural host odours are reported. Arrangements of electric nets were used to assess the effect of cattle-, human- and pig-odour on (1) the numbers of tsetse attracted to the odour source and (2) the proportion of flies that landed on a black target (1x1 m). In addition responses to monitor lizard (Varanus niloticus) were assessed in Kenya. The effects of all four odours on the proportion of tsetse that entered a biconical trap were also determined. Sources of natural host odour were produced by placing live hosts in a tent or metal hut (volumes approximately 16 m(3)) from which the air was exhausted at approximately 2000 L/min. Odours from cattle, pigs and humans had no significant effect on attraction of G. f. fuscipes but lizard odour doubled the catch (P<0.05). Similarly, mammalian odours had no significant effect on landing or trap entry whereas lizard odour increased these responses significantly: landing responses increased significantly by 22% for males and 10% for females; the increase in trap efficiency was relatively slight (5-10%) and not always significant. For G. f. quanzensis, only pig odour had a consistent effect, doubling the catch of females attracted to the source and increasing the landing response for females by approximately 15%. Dispensing CO(2) at doses equivalent to natural hosts suggested that the response of G. f. fuscipes to lizard odour was not due to CO(2). For G. f. quanzensis, pig odour and CO(2) attracted similar numbers of tsetse, but CO(2) had no material effect on the landing response. The results suggest that identifying kairomones present in lizard odour for G. f. fuscipes and pig odour for G. f. quanzensis may improve the performance of targets for controlling these species.

  5. Tsetse Flies (Glossina) as Vectors of Human African Trypanosomiasis: A Review

    PubMed Central

    Changasi, Robert Emojong

    2016-01-01

    Human African Trypanosomiasis (HAT) transmitted by the tsetse fly continues to be a public health issue, despite more than a century of research. There are two types of the disease, the chronic gambiense and the acute rhodesiense-HAT. Fly abundance and distribution have been affected by changes in land-use patterns and climate. However, disease transmission still continues. Here, we review some aspects of HAT ecoepidemiology in the context of altered infestation patterns and maintenance of the transmission cycle as well as emerging options in disease and vector control. PMID:27034944

  6. Tsetse Flies (Glossina) as Vectors of Human African Trypanosomiasis: A Review.

    PubMed

    Wamwiri, Florence Njeri; Changasi, Robert Emojong

    2016-01-01

    Human African Trypanosomiasis (HAT) transmitted by the tsetse fly continues to be a public health issue, despite more than a century of research. There are two types of the disease, the chronic gambiense and the acute rhodesiense-HAT. Fly abundance and distribution have been affected by changes in land-use patterns and climate. However, disease transmission still continues. Here, we review some aspects of HAT ecoepidemiology in the context of altered infestation patterns and maintenance of the transmission cycle as well as emerging options in disease and vector control.

  7. Diagnosis and Chemotherapy of Human Trypanosomiasis and Vector Ecology of Rift Valley and Congo-Crimean Hemorrhagic Fever in Kenya.

    DTIC Science & Technology

    1994-01-27

    AD-A280 198 I~hhumhhII AD_____ GRANT NO: DAMD17-90-Z-0005 (]’) TITLE: DIAGNOSIS AND CHEMOTHERAPY OF HUMAN TRYPANOSOMIASIS AND VECTOR ECOLOGY OF RIFT...Date OCONUS JUN 89 Diagnosis and Chemotherapy of Human Trypanosomiasis and Vector Ecology of Rift Valley Fever and Congo-Crimean Hemorrhagic Fever in...Kenya CONTENTS I. HUMAN TRYPANOSOMIASIS IN KENYA: DIAGNOSIS AND CHEMOTHERAPY Background

  8. Genome Sequence of the Tsetse Fly (Glossina morsitans): Vector of African Trypanosomiasis

    PubMed Central

    2014-01-01

    Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein–encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology. PMID:24763584

  9. Genome sequence of the tsetse fly (Glossina morsitans): vector of African trypanosomiasis.

    PubMed

    2014-04-25

    Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein-encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology.

  10. A review of recent knowledge of the ecology of the main vectors of trypanosomiasis*

    PubMed Central

    Langridge, W. P.; Kernaghan, R. J.; Glover, P. E.

    1963-01-01

    In this survey of recent ecological research on the main vectors of trypanosomiasis in those countries of East, Central and West Africa that are not predominantly French-speaking, the authors, after outlining the distribution of tsetse flies and the type of country in which they occur, discuss the direct and indirect effects of climate on these insects—particularly on their physiological water balance and on pupal fat reserves—and their recent advances into new areas. They review the considerable work that has been done on the resting habits and breeding-sites of different Glossina species, knowledge of which is important for effective control, and research on predators of pupae and adult flies and on the feeding activity of tsetse flies. Means of assessing populations and various factors affecting the size and nutritional status of tsetse flies are also discussed, as is the effect on the fly population of artificial changes in the habitat. Finally, a plea is made for a revision of present methods of land use and stock management, if full advantage is to be taken of achievements in fly control. PMID:13928678

  11. Diagnosis and Chemotherapy of Human Trypanosomiasis and Vector Ecology of Rift Valley Fever and Congo-Crimean Hemorrhagic Fever in Kenya

    DTIC Science & Technology

    1991-11-06

    AD-A259 524 AD GRANT NO: DAMD17-90-Z-0005 TITLE: DIAGNOSIS AND CHEMOTHERAPY OF HUMAN TRYPANOSOMIASIS AND VECTOR ECOLOGY OF RIFT VALLEY FEVER AND...62787A 62787A870 AN 014 11. TITLE (dud Secufity Claniflcat•)n) Diagnosis and Chemotherapy of Human Trypanosomiasis and Vector Ecology of Rift Valley...OCONUS JUN 89 - -- .- . . .- . . .. ’-..." -. . :- -•- ... , .-. ,. I Diagnosis and Chemotherapy of Human Trypanosomiasis a. Screening of WRAIR

  12. Past and Ongoing Tsetse and Animal Trypanosomiasis Control Operations in Five African Countries: A Systematic Review

    PubMed Central

    Holt, Hannah R.; Selby, Richard; Guitian, Javier

    2016-01-01

    Background Control operations targeting Animal African Trypanosomiasis and its primary vector, the tsetse, were covering approximately 128,000 km2 of Africa in 2001, which is a mere 1.3% of the tsetse infested area. Although extensive trypanosomiasis and tsetse (T&T) control operations have been running since the beginning of the 20th century, Animal African Trypanosomiasis is still a major constraint of livestock production in sub-Saharan Africa. Methodology/Principal Findings We performed a systematic review of the existing literature describing T&T control programmes conducted in a selection of five African countries, namely Burkina Faso, Cameroon, Ethiopia, Uganda and Zambia, between 1980 and 2015. Sixty-eight documents were eventually selected from those identified by the database search. This was supplemented with information gathered through semi-structured interviews conducted with twelve key informants recruited in the study countries and selected based on their experience and knowledge of T&T control. The combined information from these two sources was used to describe the inputs, processes and outcomes from 23 major T&T control programmes implemented in the study countries. Although there were some data gaps, involvement of the target communities and sustainability of the control activities were identified as the two main issues faced by these programmes. Further, there was a lack of evaluation of these control programmes, as well as a lack of a standardised methodology to conduct such evaluations. Conclusions/Significance Past experiences demonstrated that coordinated and sustained control activities require careful planning, and evidence of successes, failures and setbacks from past control programmes represent a mine of information. As there is a lack of evaluation of these programmes, these data have not been fully exploited for the design, analyses and justification of future control programmes. PMID:28027299

  13. Human African trypanosomiasis prevention, treatment and control costs: a systematic review.

    PubMed

    Keating, Joseph; Yukich, Joshua O; Sutherland, C Simone; Woods, Geordie; Tediosi, Fabrizio

    2015-10-01

    The control and eventual elimination of human African trypanosomiasis (HAT) requires the expansion of current control and surveillance activities. A systematic review of the published literature on the costs of HAT prevention, treatment, and control, in addition to the economic burden, was conducted. All studies that contained primary or secondary data on costs of prevention, treatment and control were considered, resulting in the inclusion of 42 papers. The geographically focal nature of the disease and a lack of standardization in the cost data limit the usefulness of the available information for making generalizations across diverse settings. More recent information on the costs of treatment and control interventions for HAT is needed to provide accurate information for analyses and planning. The cost information contained herein can be used to inform rational decision making in control and elimination programs, and to assess potential synergies with existing vector-borne disease control programs, but programs would benefit significantly from new cost data collection.

  14. Challenges facing the elimination of sleeping sickness in west and central Africa: sustainable control of animal trypanosomiasis as an indispensable approach to achieve the goal.

    PubMed

    Simo, Gustave; Rayaisse, Jean Baptiste

    2015-12-16

    African trypanosomiases are infectious diseases caused by trypanosomes. African animal trypanosomiasis (AAT) remains an important threat for livestock production in some affected areas whereas human African trypanosomiasis (HAT) is targeted for elimination in 2020. In West and Central Africa, it has been shown that the parasites causing these diseases can coexist in the same tsetse fly or the same animal. In such complex settings, the control of these diseases must be put in the general context of trypanosomiasis control or "one health" concept where the coordination of control operations will be beneficial for both diseases. In this context, implementing control activities on AAT will help to sustain HAT control. It will also have a positive impact on animal health and economic development of the regions. The training of inhabitants on how to implement and sustain vector control tools will enable a long-term sustainability of control operations that will lead to the elimination of HAT and AAT.

  15. Tsetse fly control and trypanosomiasis in Africa, quo vadis?

    PubMed

    Dräger, N

    2011-02-01

    National and international efforts to eradicate tsetse fly-borne human and animal trypanosomiasis are critically evaluated, and possible reasons for their failure in many cases are discussed. Some formerly performed campaigns in specific areas with positive results cannot be taken as examples to solve the main problems. In future, a significant reduction of trypanosomiasis cases will be possible to achieve only if a concerted long-term Pan-African approach, based on financial security, the continuity of expert staff, and a well-planned, ecologically sound land use, is generally accepted.

  16. Control of human African trypanosomiasis in the Quiçama focus, Angola.

    PubMed Central

    Ruiz, José Antonio; Simarro, Pere P.; Josenando, Teofilo

    2002-01-01

    OBJECTIVE: To update the epidemiological status of human African trypanosomiasis (HAT), also known as sleeping sickness, in the Quiçama focus, province of Bengo, Angola, and to establish a HAT control programme. METHODS: In 1997, 8796 people (the population of 31 villages) were serologically screened for Trypanosoma brucei gambiense, the causative agent of HAT. In 1998 and 1999, surveys were carried out in villages where HAT cases had been identified in 1997. Individuals were screened using the card agglutination trypanosomiasis test (CATT), and then examined for the presence of the parasite. CATT- positive individuals in whom the presence of the parasite could not be confirmed were further tested with the CATT using serum dilutions, and those with a positive antibody end titre of 1-in-4 or above were followed-up. Patients with < or =10 white cells/micro l and no trypanosomes in their cerebrospinal fluid (CSF) were classified as being in the first stage of the disease. Vector control was not considered necessary or feasible. FINDINGS: The main transmission areas were on the Kwanza riverbanks, where 5042 inhabitants live. In 1997, the HAT prevalence was 1.97%, but this decreased to 0.55% in 1998 and to 0.33% in 1999. The relapse rate was 3% in patients treated with pentamidine and 3.5% in patients treated with melarsoprol. In patients treated with pentamidine, there was no difference in the relapse rate for patients with initial CSF white cell counts of 0-5 cells/ micro l or 6-10 cells/micro l. The overall mortality rate was 0.6% and the rate of reactive arsenical encephalopathy among the melarsoprol-treated patients was 1.7%. CONCLUSION: The epidemiological status of the disease was updated and the transmission areas were defined. The control methods implemented allowed the disease prevalence to be reduced. PMID:12378293

  17. Human African trypanosomiasis.

    PubMed

    Lejon, Veerle; Bentivoglio, Marina; Franco, José Ramon

    2013-01-01

    Human African trypanosomiasis or sleeping sickness is a neglected tropical disease that affects populations in sub-Saharan Africa. The disease is caused by infection with the gambiense and rhodesiense subspecies of the extracellular parasite Trypanosoma brucei, and is transmitted to humans by bites of infected tsetse flies. The disease evolves in two stages, the hemolymphatic and meningoencephalitic stages, the latter being defined by central nervous system infection after trypanosomal traversal of the blood-brain barrier. African trypanosomiasis, which leads to severe neuroinflammation, is fatal without treatment, but the available drugs are toxic and complicated to administer. The choice of medication is determined by the infecting parasite subspecies and disease stage. Clinical features include a constellation of nonspecific symptoms and signs with evolving neurological and psychiatric alterations and characteristic sleep-wake disturbances. Because of the clinical profile variability and insidiously progressive central nervous system involvement, disease staging is currently based on cerebrospinal fluid examination, which is usually performed after the finding of trypanosomes in blood or other body fluids. No vaccine being available, control of human African trypanosomiasis relies on diagnosis and treatment of infected patients, assisted by vector control. Better diagnostic tools and safer, easy to use drugs are needed to facilitate elimination of the disease.

  18. Disappearance of some human African trypanosomiasis transmission foci in Zambia in the absence of a tsetse fly and trypanosomiasis control program over a period of forty years.

    PubMed

    Mwanakasale, Victor; Songolo, Peter

    2011-03-01

    We conducted a situation analysis of human African trypanosomiasis (HAT) in Zambia from January 2000 to April 2007. The aim of this survey was to identify districts in Zambia that were still recording cases of HAT. Three districts namely, Mpika, Chama, and Chipata were found to be still reporting cases of HAT and thus lay in HAT transmission foci in North Eastern Zambia. During the period under review, 24 cases of HAT were reported from these three districts. We thereafter reviewed literature on the occurrence of HAT in Zambia from the early 1960s to mid 1990s. This revealed that HAT transmission foci were widespread in Western, North Western, Lusaka, Eastern, Luapula, and Northern Provinces of Zambia during this period. In this article we have tried to give possible reasons as to why the distribution of HAT transmission foci is so different between before and after 2000 when there has been no active national tsetse fly and trypanosomiasis control program in Zambia.

  19. Beyond Tsetse--Implications for Research and Control of Human African Trypanosomiasis Epidemics.

    PubMed

    Welburn, Susan C; Molyneux, David H; Maudlin, Ian

    2016-03-01

    Epidemics of both forms of human African trypanosomiasis (HAT) are confined to spatially stable foci in Sub-Saharan Africa while tsetse distribution is widespread. Infection rates of Trypanosoma brucei gambiense in tsetse are extremely low and cannot account for the catastrophic epidemics of Gambian HAT (gHAT) seen over the past century. Here we examine the origins of gHAT epidemics and evidence implicating human genetics in HAT epidemiology. We discuss the role of stress causing breakdown of heritable tolerance in silent disease carriers generating gHAT outbreaks and see how peculiarities in the epidemiologies of gHAT and Rhodesian HAT (rHAT) impact on strategies for disease control.

  20. American Trypanosomiasis

    DTIC Science & Technology

    2011-06-01

    unlimited 13. SUPPLEMENTARY NOTES See also ADA545141. Chapter 2 from e-book, Topics on the Pathology of Protozoan and Invasive Arthropod Diseases. 14...rod-shaped kinetoplast (arrow). x1000 2 2 • Topics on The paThology of proTozoan and invasive arThropod diseases In South America, trypanosomiasis...endemic areas.6,7 Trypanosoma rangeli, a related and similarly distributed protozoan , is nonpathogenic. It does not invade and destroy cells and

  1. African Trypanosomiasis

    DTIC Science & Technology

    2011-06-01

    infection by protozoan hemo- flagellates of the Trypanosoma brucei complex, 2 subspe- cies of which cause disease in humans: Trypanosoma bru- cei gambiense...public release; distribution unlimited 13. SUPPLEMENTARY NOTES See also ADA545141. Chapter 3 from e-book, Topics on the Pathology of Protozoan and...the brief ferry crossing. 2 3 • Topics on The paThology of proTozoan and invasive arThropod diseases Three severe epidemics of African trypanosomiasis

  2. Short-course eflornithine in Gambian trypanosomiasis: a multicentre randomized controlled trial.

    PubMed Central

    Pépin, J.; Khonde, N.; Maiso, F.; Doua, F.; Jaffar, S.; Ngampo, S.; Mpia, B.; Mbulamberi, D.; Kuzoe, F.

    2000-01-01

    OBJECTIVE: A randomized controlled trial was conducted to determine whether 7 days of intravenous eflornithine (100 mg/kg every 6 h) was as effective as the standard 14-day regimen in the treatment of late-stage Trypanosoma brucei gambiense trypanosomiasis. METHODS: A total of 321 patients (274 new cases, 47 relapsing cases) were randomized at four participating centres in Congo, Côte d'Ivoire, the Democratic Republic of the Congo, and Uganda to one of these treatment regimens and followed up for 2 years. RESULTS: Six patients died during treatment, one of whom was on the 7-day regimen, whereas the other five had been on the 14-day regimen (P = 0.2). The response to eflornithine differed markedly between Uganda and other countries. Among new cases in Uganda, the 2-year probability of cure was 73% on the 14-day course compared with 62% on the 7-day regimen (hazard ratio (HR) for treatment failure, 7-day versus 14-day regimen: 1.45, 95% CI: 0.7, 3.1, P = 0.3). Among new cases in Côte d'Ivoire, Congo, and the Democratic Republic of the Congo combined, the 2-year probability of cure was 97% on the 14-day course compared with 86.5% on the 7-day regimen (HR for treatment failure, 7-day vs 14-day: 6.72, 95% confidence interval (CI): 1.5, 31.0, P = 0.003). Among relapsing cases in all four countries, the 2-year probability of cure was 94% with 7 days and 100% with 14 days of treatment. Factors associated with a higher risk of treatment failure were: a positive lymph node aspirate (HR 4.1; 95% CI: 1.8-9.4), a cerebrospinal fluid (CSF) white cell count > or = 100/mm3 (HR 3.5; 95% CI: 1.1-10.9), being treated in Uganda (HR 2.9; 95% CI: 1.4-5.9), and CSF trypanosomes (HR 1.9; 95% CI: 0.9-4.1). Being stuporous on admission was associated with a lower risk of treatment failure (HR 0.18; 95% CI: 0.02-1.4) as was increasing age (HR 0.977; 95% CI: 0.95-1.0, for each additional year of age). DISCUSSION: The 7-day course of eflornithine is an effective treatment of relapsing cases

  3. Implications of Heterogeneous Biting Exposure and Animal Hosts on Trypanosomiasis brucei gambiense Transmission and Control

    PubMed Central

    Stone, Chris M.; Chitnis, Nakul

    2015-01-01

    The gambiense form of sleeping sickness is a neglected tropical disease, which is presumed to be anthroponotic. However, the parasite persists in human populations at levels of considerable rarity and as such the existence of animal reservoirs has been posited. Clarifying the impact of animal host reservoirs on the feasibility of interrupting sleeping sickness transmission through interventions is a matter of urgency. We developed a mathematical model allowing for heterogeneous exposure of humans to tsetse, with animal populations that differed in their ability to transmit infections, to investigate the effectiveness of two established techniques, screening and treatment of at-risk populations, and vector control. Importantly, under both assumptions, an integrated approach of human screening and vector control was supported in high transmission areas. However, increasing the intensity of vector control was more likely to eliminate transmission, while increasing the intensity of human screening reduced the time to elimination. Non-human animal hosts played important, but different roles in HAT transmission, depending on whether or not they contributed as reservoirs. If they did not serve as reservoirs, sensitivity analyses suggested their attractiveness may instead function as a sink for tsetse bites. These outcomes highlight the importance of understanding the ecological and environmental context of sleeping sickness in optimizing integrated interventions, particularly for moderate and low transmission intensity settings. PMID:26426854

  4. The impact of insecticide-resistance on control of vectors and vector-borne diseases

    PubMed Central

    Busvine, J. R.; Pal, R.

    1969-01-01

    A questionnaire inquiring into the nature of schemes for the insecticidal control of disease vectors, the development of resistance in these vectors, and the effect of any such resistance on their control and on the extent of disease was sent to more than 100 health authorities throughout the world. The replies to the questionnaire are summarized in this paper. Until recently, the use of insecticides in public health has been largely based on three organochlorine compounds—DDT, HCH and dieldrin. However, in some countries resistance to these has now severely affected control both of many insect species and of the diseases they transmit (e.g., malaria, yellow fever, filariasis, typhus, plague). Certain other public health problems (onchocerciasis, Chagas' disease, trypanosomiasis, leishmaniasis) have not so far been greatly affected by resistance, but it is difficult to be sure of the continued reliability of the organochlorines. Research in the past 5 years, much of it sponsored by WHO, has shown the value of various organophosphorus and carbamate insecticides as replacements for the organochlorines, although resistance to them, too, can occur. Attention must therefore be focused on all facets of the use of these newer compounds and particular scrutiny made of possible instances of resistance to them. PMID:5307234

  5. Thrust-Vector-Control System

    NASA Technical Reports Server (NTRS)

    Murray, Jonathan

    1992-01-01

    Control gains computed via matrix Riccati equation. Software-based system controlling aim of gimbaled rocket motor on spacecraft adaptive and optimal in sense it adjusts control gains in response to feedback, according to optimizing algorithm based on cost function. Underlying control concept also applicable, with modifications, to thrust-vector control on vertical-takeoff-and-landing airplanes, control of orientations of scientific instruments, and robotic control systems.

  6. [American human trypanosomiasis 90 years after its discovery by Carlos Chagas. I. Epidemiology and control].

    PubMed

    Pays, J F

    1998-01-01

    It was in 1909 that Carlos Chagas described the disease which now bears his name. During the ensuing 90 years, our knowledge of this apparently whimsical, protozoan disease has grown enormously but many points remain unclear. Epidemiologically speaking, current knowledge is poor about the mechanisms and markers of variability of Trypanosoma cruzi, mechanisms allowing the organism to survive in the host, and susceptibility of infected individuals to disabling or fatal late complications. With regard to vector control, it is increasingly obvious that success will be more difficult than previously thought due to the likelihood that, as domestic species are exterminated, they will be replaced by semi-domesticated or wild species. Two other factors that have significantly changed the conventional epidemiological profile of Chagas'disease on the subcontinent over the past 50 years are human intervention in the environment and population migration from rural to urban zones. Despite the breakthroughs achieved in the last decade. Chagas'disease, with its multiple modes of transmission (vector-borne, congenital, and transfusional to name but the most important), diverse reservoir involving over 175 species, and potential for course of the disease in man, will remain a major health problem in Latin America countries for many years to come.

  7. Vector insects and their control.

    PubMed

    Lehane, M J

    1996-01-01

    This paper emphasizes the huge influence that vector-transmitted disease has on humans using plague, epidemic typhus and nagana as examples. The continuing need for vector control in campaigns against insect-transmitted disease is shown by reference to current control programmes mounted against Chagas' disease, onchocerciasis, lymphatic filariasis and nagana. These successful campaigns have not been reliant on new breakthroughs but on the forging of available tools into effective strategies widely and efficiently used by the control authorities, and the long-lasting political commitment to the success of the schemes in question. A brief mention is made of current fashions in vector control research and that great care needs to be taken by policy-makers to achieve a balance between long-term research aiming at the production of fundamentally new control technologies and operational research aiming to forge the often highly effective tools we already have into sound control strategies.

  8. Vector control after malaria eradication

    PubMed Central

    Micks, D. W.

    1963-01-01

    In considerable areas now in or near the consolidation phase of malaria eradication, other vector-borne diseases present serious public health problems, even though not susceptible to control on the same world-wide scale as malaria. Several of these areas are already making plans for converting their malaria eradication services to vector control services. While it is possible to use essentially the same personnel and equipment, the methods must be adapted to the biology and habits of the vector. For a smooth and rapid transition, considerable advance planning is therefore needed—preferably well ahead of the consolidation phase. The author gives several examples of the need for flexibility in effecting the changeover and of the problems likely to arise after the completion of malaria eradication programmes. He recommends that epidemiological studies should be extended to vector-borne diseases other than malaria while eradication programmes are still in progress and that vector control programmes should be integrated into the basic health services of the country as soon as possible. He also underlines the importance of water management and other aspects of environmental sanitation in vector control programmes. PMID:20604169

  9. Research priorities for Chagas disease, human African trypanosomiasis and leishmaniasis.

    PubMed

    2012-01-01

    This report provides a review and analysis of the research landscape for three diseases - Chagas disease, human African trypanosomiasis and leishmaniasis - that disproportionately afflict poor and remote populations with limited access to health services. It represents the work of the disease reference group on Chagas Disease, Human African Trypanosomiasis and Leishmaniasis (DRG3) which was established to identify key research priorities through review of research evidence and input from stakeholders' consultations. The diseases, which are caused by related protozoan parasites, are described in terms of their epidemiology and diseases burden, clinical forms and pathogenesis, HIV coinfection, diagnosis, drugs and drug resistance, vaccines, vector control, and health-care interventions. Priority areas for research are identified based on criteria such as public health relevance, benefit and impact on poor populations and equity, and feasibility. The priorities are found in the areas of diagnostics, drugs, vector control, asymptomatic infection, economic analysis of treatment and vector control methods, and in some specific issues such as surveillance methods or transmission-blocking vaccines for particular diseases. This report will be useful to researchers, policy and decision-makers, funding bodies, implementation organizations, and civil society. This is one of ten disease and thematic reference group reports that have come out of the TDR Think Tank, all of which have contributed to the development of the Global Report for Research on Infectious Diseases of Poverty, available at: www.who.int/tdr/stewardship/global_report/en/index.html.

  10. Epidemiology of human African trypanosomiasis

    PubMed Central

    Franco, Jose R; Simarro, Pere P; Diarra, Abdoulaye; Jannin, Jean G

    2014-01-01

    Human African trypanosomiasis (HAT), or sleeping sickness, is caused by Trypanosoma brucei gambiense, which is a chronic form of the disease present in western and central Africa, and by Trypanosoma brucei rhodesiense, which is an acute disease located in eastern and southern Africa. The rhodesiense form is a zoonosis, with the occasional infection of humans, but in the gambiense form, the human being is regarded as the main reservoir that plays a key role in the transmission cycle of the disease. The gambiense form currently assumes that 98% of the cases are declared; the Democratic Republic of the Congo is the most affected country, with more than 75% of the gambiense cases declared. The epidemiology of the disease is mediated by the interaction of the parasite (trypanosome) with the vectors (tsetse flies), as well as with the human and animal hosts within a particular environment. Related to these interactions, the disease is confined in spatially limited areas called “foci”, which are located in Sub-Saharan Africa, mainly in remote rural areas. The risk of contracting HAT is, therefore, determined by the possibility of contact of a human being with an infected tsetse fly. Epidemics of HAT were described at the beginning of the 20th century; intensive activities have been set up to confront the disease, and it was under control in the 1960s, with fewer than 5,000 cases reported in the whole continent. The disease resurged at the end of the 1990s, but renewed efforts from endemic countries, cooperation agencies, and nongovernmental organizations led by the World Health Organization succeeded to raise awareness and resources, while reinforcing national programs, reversing the trend of the cases reported, and bringing the disease under control again. In this context, sustainable elimination of the gambiense HAT, defined as the interruption of the transmission of the disease, was considered as a feasible target for 2030. Since rhodesiense HAT is a zoonosis

  11. Bovine trypanosome species prevalence and farmers' trypanosomiasis control methods in south-western Uganda.

    PubMed

    Alingu, Richard A; Muhanguzi, Dennis; MacLeod, Ewan; Waiswa, Charles; Fyfe, Jenna

    2014-10-28

    A cross-sectional study was conducted in Mbarara district, south-western Uganda in May 2012 to determine the burden of African animal trypanosomosis (AAT) in the semi-intensive dairy production systems where pyrethroid acaricides are frequently used in the control of tick-borne diseases (TBDs). A total of 295 cattle blood samples were taken and analysed using a single pair of primers previously designed to amplify internal transcribed spacer (ITS1) of trypanosome ribosomal deoxyribonucleic acid (rDNA). A structured questionnaire was administered to 55 participating livestock farmers to generate data on acaricide and trypanocidal drug usage. The overall prevalence of trypanosome species was 2.4% (95% CI; 1.0% - 4.8%); Trypanosoma vivax was the most predominant species (2.0%; 95% CI; 0.7% - 4.4%). A single mixed infection of T. vivax and Trypanosoma brucei s.l. was detected. All the participating farmers used acaricides for tsetse and TBD control; 89.1% of the acaricides used were pyrethroids. About half of the farmers used trypanocidal drugs, mainly diminazene formulations (Berenil®). Low prevalence of trypanosomes in examined samples is most likely related to the frequent use of pyrethroid insecticides, trypanocides and restricted grazing (paddocking and tethering). These rigorous management practices are geared towards optimising production of exotic dairy breeds kept in this region that are highly susceptible to TBDs and AAT.

  12. Impact of tsetse and trypanosomiasis control on cattle herd composition and calf growth and mortality at Arbaminch District (Southern Rift Valley, Ethiopia).

    PubMed

    Gechere, Geja; Terefe, Getachew; Belihu, Kelay

    2012-10-01

    The effect of tsetse/trypanosomiasis control on cattle herd composition and growth and mortality of calves in tsetse controlled (by Southern Tsetse Eradication Project (STEP)) and uncontrolled blocks in southern Ethiopia was assessed. Structured questionnaire was used to interview 182 households to estimate cattle herd composition and calf mortality. Calves were bled to examine the presence of trypanosomes by the buffy coat technique. Forty NGU traps were deployed and fly catches determined. A case-control study was performed on 40 calves for 6 months to estimate calve growth parameters. Accordingly, the mean cattle herd size was lower in tsetse-controlled block than in the uncontrolled block, whereas the relative number of calves in a herd tend to be higher in the tsetse-controlled block (P = 0.06). While there was no report of cattle mortality in tsetse-controlled block, 16.48 % of the respondents have lost calves in tsetse-uncontrolled block in 1 year time. The prevalence of trypanosome positive calves was 2.95 % for uncontrolled block but no positive case in tsetse-controlled block. The apparent densities of flies/trap/day in tsetse-uncontrolled block were 30-fold higher than in tsetse-controlled block (P < 0.01). The case-control study revealed that the mean body weight gain of calves in tsetse-controlled block (40.23 ± 0.7 kg) was significantly higher than that of the uncontrolled block (34.74 ± 0.68 kg). The above findings strongly suggest that the intervention by the STEP project has significantly reduced tsetse population and trypanosomiasis consequently contributing to improved calf growth and survival.

  13. [Research progress on malaria vector control].

    PubMed

    Zhu, Guo-Ding; Cao, Jun; Zhou, Hua-Yun; Gao, Qi

    2013-06-01

    Vector control plays a crucial role in the stages of malaria control and elimination. Currently, it mainly relies on the chemical control methods for adult mosquitoes in malaria endemic areas, however, it is undergoing the serious threat by insecticide resistance. In recent years, the transgenic technologies of malaria vectors have made a great progress in the laboratory. This paper reviews the challenges of the traditional methods and the rapid developed genetic modified technology in the application of vector control.

  14. Insecticide resistance and vector control.

    PubMed Central

    Brogdon, W. G.; McAllister, J. C.

    1998-01-01

    Insecticide resistance has been a problem in all insect groups that serve as vectors of emerging diseases. Although mechanisms by which insecticides become less effective are similar across all vector taxa, each resistance problem is potentially unique and may involve a complex pattern of resistance foci. The main defense against resistance is close surveillance of the susceptibility of vector populations. We describe the mechanisms of insecticide resistance, as well as specific instances of resistance emergence worldwide, and discuss prospects for resistance management and priorities for detection and surveillance. PMID:9866736

  15. Control of malaria and other vector-borne protozoan diseases in the tropics: enduring challenges despite considerable progress and achievements

    PubMed Central

    2014-01-01

    Vector-borne protozoan diseases represent a serious public health challenge, especially in the tropics where poverty together with vector-favorable climates are the aggravating factors. Each of the various strategies currently employed to face these scourges is seriously inadequate. Despite enormous efforts, vaccines—which represent the ideal weapon against these parasitic diseases—are yet to be sufficiently developed and implemented. Chemotherapy and vector control are therefore the sole effective attempts to minimize the disease burden. Nowadays, both strategies are also highly challenged by the phenomenon of drug and insecticide resistance, which affects virtually all interventions currently used. The recently growing support from international organizations and governments of some endemic countries is warmly welcome, and should be optimally exploited in the various approaches to drug and insecticide research and development to overcome the burden of these prevalent diseases, especially malaria, leishmaniasis, Human African Trypanosomiasis (HAT), and Chagas disease. PMID:24401663

  16. Control of phlebotomine (Diptera: Psychodidae) leishmaniasis vectors.

    PubMed

    Amóra, Sthenia S A; Bevilaqua, Claudia M L; Feijó, Francisco M C; D Alves, Nilza; do V Maciel, Michelline

    2009-01-01

    Phlebotomines are of medical and veterinary concern as they vector leishmaniasis, bartonellosis and some arboviruses. The adaptations of some species to places modified by humans bring these vectors into contact with dwellings, which can facilitate disease transmission, and the vector control strategies adopted have rendered controversial results. Regarding leishmaniasis, for instance, which vector and reservoirs control can be effective, there is an assumption that the incidence of human infection is directly related to the number of infectious dogs, as well as to entomological factors. Therefore, vector control can provide a cheaper and more practical solution to prevent cases of leishmaniasis. Nevertheless, due to the complexity of the factors involved, chemical control is still essential, and biological insecticides and insecticide plants, for example, represent areas for study that should be encouraged and developed since they show promising results. This paper summarizes the control strategies adopted so far, especially the methods and efficiency of the entomological components of leishmaniasis control programs.

  17. Integrated Thrust Vectored Engine Control

    DTIC Science & Technology

    2001-06-01

    erformances operationnelles des aeronefs militaires, des vehicules terrestres et des vehicules maritimes] To order the complete compilation report...throttling "* Autonomous Engine Configuration Side forces demand to define nozzle vectoring "* Simple Interface FADEC -> FCS " Minimum Interaction FCS

  18. Malaria vector control: from past to future.

    PubMed

    Raghavendra, Kamaraju; Barik, Tapan K; Reddy, B P Niranjan; Sharma, Poonam; Dash, Aditya P

    2011-04-01

    Malaria is one of the most common vector-borne diseases widespread in the tropical and subtropical regions. Despite considerable success of malaria control programs in the past, malaria still continues as a major public health problem in several countries. Vector control is an essential part for reducing malaria transmission and became less effective in recent years, due to many technical and administrative reasons, including poor or no adoption of alternative tools. Of the different strategies available for vector control, the most successful are indoor residual spraying and insecticide-treated nets (ITNs), including long-lasting ITNs and materials. Earlier DDT spray has shown spectacular success in decimating disease vectors but resulted in development of insecticide resistance, and to control the resistant mosquitoes, organophosphates, carbamates, and synthetic pyrethroids were introduced in indoor residual spraying with needed success but subsequently resulted in the development of widespread multiple insecticide resistance in vectors. Vector control in many countries still use insecticides in the absence of viable alternatives. Few developments for vector control, using ovitraps, space spray, biological control agents, etc., were encouraging when used in limited scale. Likewise, recent introduction of safer vector control agents, such as insect growth regulators, biocontrol agents, and natural plant products have yet to gain the needed scale of utility for vector control. Bacterial pesticides are promising and are effective in many countries. Environmental management has shown sufficient promise for vector control and disease management but still needs advocacy for inter-sectoral coordination and sometimes are very work-intensive. The more recent genetic manipulation and sterile insect techniques are under development and consideration for use in routine vector control and for these, standardized procedures and methods are available but need thorough

  19. A Multi-Host Agent-Based Model for a Zoonotic, Vector-Borne Disease. A Case Study on Trypanosomiasis in Eastern Province, Zambia

    PubMed Central

    Macleod, Ewan T.; Anderson, Neil E.; Schaten, Kathrin; Kuleszo, Joanna; Simuunza, Martin; Welburn, Susan C.; Atkinson, Peter M.

    2016-01-01

    Background This paper presents a new agent-based model (ABM) for investigating T. b. rhodesiense human African trypanosomiasis (rHAT) disease dynamics, produced to aid a greater understanding of disease transmission, and essential for development of appropriate mitigation strategies. Methods The ABM was developed to model rHAT incidence at a fine spatial scale along a 75 km transect in the Luangwa Valley, Zambia. The method offers a complementary approach to traditional compartmentalised modelling techniques, permitting incorporation of fine scale demographic data such as ethnicity, age and gender into the simulation. Results Through identification of possible spatial, demographic and behavioural characteristics which may have differing implications for rHAT risk in the region, the ABM produced output that could not be readily generated by other techniques. On average there were 1.99 (S.E. 0.245) human infections and 1.83 (S.E. 0.183) cattle infections per 6 month period. The model output identified that the approximate incidence rate (per 1000 person-years) was lower amongst cattle owning households (0.079, S.E. 0.017), than those without cattle (0.134, S.E. 0.017). Immigrant tribes (e.g. Bemba I.R. = 0.353, S.E.0.155) and school-age children (e.g. 5–10 year old I.R. = 0.239, S.E. 0.041) were the most at-risk for acquiring infection. These findings have the potential to aid the targeting of future mitigation strategies. Conclusion ABMs provide an alternative way of thinking about HAT and NTDs more generally, offering a solution to the investigation of local-scale questions, and which generate results that can be easily disseminated to those affected. The ABM can be used as a tool for scenario testing at an appropriate spatial scale to allow the design of logistically feasible mitigation strategies suggested by model output. This is of particular importance where resources are limited and management strategies are often pushed to the local scale. PMID:28027323

  20. Vector control activities. Fiscal year, 1982

    SciTech Connect

    Pickard, E.; Cooney, J.C.; McDuff, B.R.

    1983-06-01

    The goal of the TVA Vector Control Program is to protect the public from potential vectors of disease by controlling medically-important arthropod pests that are propagated on TVA lands or waters. In addition, freedom from annoying mosquitoes and other blood-sucking pests permits the development, use, and full enjoyment of the vast recreational opportunities offered by the many miles of freshwater lakes. To attain this goal the program is divided into operations and support studies. The support studies are designed to improve the operational effectiveness and efficiency of the control program and to identify other vector control problems that require TVA attention and study. Specifically, activities concerning water level management of TVA lakes, dewatering projects, plant growth control, drainage and insect control programs are detailed. Further, report is made of post-impoundment surveys, soil sampling studies of Mosquite larvae and ecological mosquito management studies.

  1. Feedback Control Design for Counterflow Thrust Vectoring

    DTIC Science & Technology

    2005-09-01

    thrust vector angle. A model 27N pneumatic R-DDV servovalve from HR Textron is used in the test rig for this purpose. Data acquisition and control are...support this research. We also thank Robert Avant, Fritz Dittus and Mohammed I. Alidu for helping in the experimental setup. References ’Alvi, F. S... Thomson , M., "Minimal Controller Synthesis for Time-delay Systems Using a Smith Predictor," IEE Colloquium on Adaptive Controllers in Practice - Part Two

  2. Ascent thrust vector control system test

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Testing of the Ascent Thrust Vector Control System in support of the Ares 1-X program at the Marshall Space Flight Center in Huntsville, Alabama. This image is extracted from a high definition video file and is the highest resolution available

  3. Socio-Economic and Cultural Determinants of Human African Trypanosomiasis at the Kenya – Uganda Transboundary

    PubMed Central

    Rutto, Jane Jemeli; Osano, Odipo; Thuranira, Elias Gitonga; Kurgat, Richard Kiptum; Odenyo, Victor Agab Omondi

    2013-01-01

    Background Kenya and Uganda have reported different Human African Trypanosomiasis incidences in the past more than three decades, with the latter recording more cases. This cross-sectional study assessed the demographic characteristics, tsetse and trypanosomiasis control practices, socio-economic and cultural risk factors influencing Trypanosoma brucei rhodesiense (T.b.r.) infection in Teso and Busia Districts, Western Kenya and Tororo and Busia Districts, Southeast Uganda. A conceptual framework was postulated to explain interactions of various socio-economic, cultural and tsetse control factors that predispose individuals and populations to HAT. Methods A cross-sectional household survey was conducted between April and October 2008. Four administrative districts reporting T.b.r and lying adjacent to each other at the international boundary of Kenya and Uganda were purposely selected. Household data collection was carried out in two villages that had experienced HAT and one other village that had no reported HAT case from 1977 to 2008 in each district. A structured questionnaire was administered to 384 randomly selected household heads or their representatives in each country. The percent of respondents giving a specific answer was reported. Secondary data was also obtained on socio-economic and political issues in both countries. Results Inadequate knowledge on the disease cycle and intervention measures contributed considerable barriers to HAT, and more so in Uganda than in Kenya. Gender-associated socio-cultural practices greatly predisposed individuals to HAT. Pesticides-based crop husbandry in the 1970's reportedly reduced vector population while vegetation of coffee and banana's and livestock husbandry directly increased occurrence of HAT. Livestock husbandry practices in the villages were strong predictors of HAT incidence. The residents in Kenya (6.7%) applied chemoprophylaxis and chemotherapeutic controls against trypanosomiasis to a larger extent than

  4. Mosquito Oviposition Behavior and Vector Control.

    PubMed

    Day, Jonathan F

    2016-11-18

    The burden of gene transfer from one mosquito generation to the next falls on the female and her eggs. The selection of an oviposition site that guarantees egg and larval survival is a critical step in the reproductive process. The dangers associated with ephemeral aquatic habitats, lengthy droughts, freezing winters, and the absence of larval nutrition makes careful oviposition site selection by a female mosquito extremely important. Mosquito species exhibit a remarkable diversity of oviposition behaviors that ensure eggs are deposited into microenvironments conducive for successful larval development and the emergence of the next mosquito generation. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control opportunities directed against specific disease vectors. For example, Aedes aegypti Linnaeus is the vector of viruses causing important human diseases including yellow fever, dengue, chikungunya, and Zika. The preference of this species to oviposit in natural and artificial containers has facilitated the development of Ae. aegypti-specific surveillance and toxic oviposition traps designed to detect and control this important vector species in and around disease foci. A better understanding of the wide diversity of mosquito oviposition behavior will allow the development of new and innovative surveillance and control devices directed against other important mosquito vectors of human and animal disease.

  5. Mosquito Oviposition Behavior and Vector Control

    PubMed Central

    Day, Jonathan F.

    2016-01-01

    The burden of gene transfer from one mosquito generation to the next falls on the female and her eggs. The selection of an oviposition site that guarantees egg and larval survival is a critical step in the reproductive process. The dangers associated with ephemeral aquatic habitats, lengthy droughts, freezing winters, and the absence of larval nutrition makes careful oviposition site selection by a female mosquito extremely important. Mosquito species exhibit a remarkable diversity of oviposition behaviors that ensure eggs are deposited into microenvironments conducive for successful larval development and the emergence of the next mosquito generation. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control opportunities directed against specific disease vectors. For example, Aedes aegypti Linnaeus is the vector of viruses causing important human diseases including yellow fever, dengue, chikungunya, and Zika. The preference of this species to oviposit in natural and artificial containers has facilitated the development of Ae. aegypti-specific surveillance and toxic oviposition traps designed to detect and control this important vector species in and around disease foci. A better understanding of the wide diversity of mosquito oviposition behavior will allow the development of new and innovative surveillance and control devices directed against other important mosquito vectors of human and animal disease. PMID:27869724

  6. African trypanosomiasis and antibodies: implications for vaccination, therapy and diagnosis.

    PubMed

    Magez, Stefan; Radwanska, Magdalena

    2009-10-01

    African trypanosomiasis causes devastating effects on human populations and livestock herds in large parts of sub-Saharan Africa. Control of the disease is hampered by the lack of any efficient vaccination results in a field setting, and the severe side effects of current drug therapies. In addition, with the exception of Trypanosoma brucei gambiense infections, the diagnosis of trypanosomiasis has to rely on microscopic analysis of blood samples, as other specific tools are nonexistent. However, new developments in biotechnology, which include loop-mediated isothermal amplification as an adaptation to conventional PCR, as well as the antibody engineering that has allowed the development of Nanobody technology, offer new perspectives in both the detection and treatment of trypanosomiasis. In addition, recent data on parasite-induced B-cell memory destruction offer new insights into mechanisms of vaccine failure, and should lead us towards new strategies to overcome trypanosome defenses operating against the host immune system.

  7. Electromechanical actuation for thrust vector control applications

    NASA Technical Reports Server (NTRS)

    Roth, Mary Ellen

    1990-01-01

    The advanced launch system (ALS), is a launch vehicle that is designed to be cost-effective, highly reliable, and operationally efficient with a goal of reducing the cost per pound to orbit. An electromechanical actuation (EMA) system is being developed as an attractive alternative to the hydraulic systems. The controller will integrate 20 kHz resonant link power management and distribution (PMAD) technology and pulse population modulation (PPM) techniques to implement field-oriented vector control (FOVC) of a new advanced induction motor. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a built-in test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance, and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA thrust vector control (TVC) system. The EMA system and work proposed for the future are discussed.

  8. Vector ecology and integrated control procedures

    PubMed Central

    Laird, Marshall

    1963-01-01

    The elucidation of population regulatory mechanisms calls for exhaustive biological and ecological studies of whole ecosystems. Until lately, little effort was made to relate insect control activities to such a background, and the use of non-selective pesticides has often resulted in biotic equilibria being disrupted to the ultimate advantage of the organism under attack or of some other undesirable species. However, there is a growing realization in the field of economic entomology at large that biotic control agents usually constitute the major portion of the environmental resistance to increases in pest numbers and that insecticides should be fitted into the ecosystem, and not imposed upon it—in fact, that integrated control procedures are called for. The author considers such integrated procedures from the standpoint of vector control. His paper points out their potentialities in helping to solve resistance problems and in increasing the selectivity of control operations. It further suggests that they offer the means of achieving economical and lasting reductions of vector populations to levels at which human disease transmission is interrupted and pest problems lose much of their importance. PMID:20604165

  9. Chagas disease (American trypanosomiasis) in Mexico: an update.

    PubMed

    Carabarin-Lima, Alejandro; González-Vázquez, María Cristina; Rodríguez-Morales, Olivia; Baylón-Pacheco, Lidia; Rosales-Encina, José Luis; Reyes-López, Pedro Antonio; Arce-Fonseca, Minerva

    2013-08-01

    Chagas disease is a parasitic infection caused by the protozoan Trypanosoma cruzi, a flagellated organism that is transmitted mainly to humans through the infected feces of triatomine kissing bugs (vector transmission in endemic areas) or by transfusion of infected blood, donations of infected organ, or transmission from an infected mother to her child at birth. Chagas disease was first described in 1909 by the Brazilian physician Carlos Chagas, and due to the parasite's distribution throughout North, Central and South America, the disease is commonly known as American trypanosomiasis. However, this disease is now present in non-endemic countries such as Canada, the United States of America, and several countries in Europe (principally Spain). Moreover, Chagas disease was recently designated by the World Health Organization as one of the main neglected tropical diseases. The aim of this review is to summarize the research efforts recently described in studies conducted in Mexico on Chagas disease. In this country, there are no existing vector control programs. In addition, there is no consensus on the diagnostic methods for acute and chronic Chagas disease in maternity wards and blood banks, and trypanocidal therapy is not administered to chronic patients. The actual prevalence of the disease is unknown because no official reporting of cases is performed. Therefore, the number of people infected by different routes of transmission (vector, congenital, blood transfusion, organ transplantation, or oral) is unknown. We believe that by promoting education about Chagas disease in schools starting at the basic elementary level and including reinforcement at higher education levels will ensure that the Mexican population would be aware of this health problem and that the control measures adopted will have more acceptance and success. We hope that this review sensitizes the relevant authorities and that the appropriate measures to reduce the risk of infection by T. cruzi

  10. 40 CFR 258.22 - Disease vector control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Disease vector control. 258.22 Section... MUNICIPAL SOLID WASTE LANDFILLS Operating Criteria § 258.22 Disease vector control. (a) Owners or operators of all MSWLF units must prevent or control on-site populations of disease vectors using...

  11. 40 CFR 258.22 - Disease vector control.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Disease vector control. 258.22 Section... MUNICIPAL SOLID WASTE LANDFILLS Operating Criteria § 258.22 Disease vector control. (a) Owners or operators of all MSWLF units must prevent or control on-site populations of disease vectors using...

  12. 40 CFR 258.22 - Disease vector control.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Disease vector control. 258.22 Section... MUNICIPAL SOLID WASTE LANDFILLS Operating Criteria § 258.22 Disease vector control. (a) Owners or operators of all MSWLF units must prevent or control on-site populations of disease vectors using...

  13. 40 CFR 258.22 - Disease vector control.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Disease vector control. 258.22 Section... MUNICIPAL SOLID WASTE LANDFILLS Operating Criteria § 258.22 Disease vector control. (a) Owners or operators of all MSWLF units must prevent or control on-site populations of disease vectors using...

  14. 40 CFR 258.22 - Disease vector control.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Disease vector control. 258.22 Section... MUNICIPAL SOLID WASTE LANDFILLS Operating Criteria § 258.22 Disease vector control. (a) Owners or operators of all MSWLF units must prevent or control on-site populations of disease vectors using...

  15. Conflict and human African trypanosomiasis.

    PubMed

    Berrang-Ford, Lea; Lundine, Jamie; Breau, Sebastien

    2011-02-01

    Human African Trypanosomiasis (HAT) has reemerged in sub-Saharan Africa as a disease of major public health importance. The success of HAT elimination in sub-Saharan Africa is subject to the feasibility of controlling, eliminating, or mitigating the determinants of incidence in affected countries. Conflict has been widely recognized and cited as a contributing factor to the resurgence of HAT in many countries, as well as to continuing HAT incidence in politically unstable and resource-poor regions. Despite extensive anecdotal and qualitative recognition of the role of conflict, there has been no quantitative research of this topic at the population level in affected African countries. We characterize the qualitative and quantitative associations between HAT incidence and conflict-related processes in HAT-affected African countries over the past 30 years. HAT and conflict-related data were collected for 35 affected countries in sub-Saharan Africa for the years 1976-2004. Descriptive and univariate inferential statistics, as well as negative binomial regression modeling, are used to assess the associations between HAT and conflict. A space-time scan statistic is used to identify significant incidence clusters. Clusters of HAT incidence over the past 30 years have predominantly coincided with periods of conflict or socio-political instability. HAT cases occurred significantly more often in countries and during years with conflict, high political terror, and internationalized civil war. The results indicate a lag period between the start of conflict events and a peak in incidence of approximately 10 years. We recommend explicit consideration and quantification of socio-political measures such as conflict and terror indices in GIS (Geographic Information Systems)-based risk assessments for HAT policy and intervention.

  16. The Biological Control of the Malaria Vector

    PubMed Central

    Kamareddine, Layla

    2012-01-01

    The call for malaria control, over the last century, marked a new epoch in the history of this disease. Many control strategies targeting either the Plasmodium parasite or the Anopheles vector were shown to be effective. Yet, the emergence of drug resistant parasites and insecticide resistant mosquito strains, along with numerous health, environmental, and ecological side effects of many chemical agents, highlighted the need to develop alternative tools that either complement or substitute conventional malaria control approaches. The use of biological means is considered a fundamental part of the recently launched malaria eradication program and has so far shown promising results, although this approach is still in its infancy. This review presents an overview of the most promising biological control tools for malaria eradication, namely fungi, bacteria, larvivorous fish, parasites, viruses and nematodes. PMID:23105979

  17. Electromechanical actuation for thrust vector control applications

    NASA Technical Reports Server (NTRS)

    Roth, Mary Ellen

    1990-01-01

    At present, actuation systems for the Thrust Vector Control (TVC) for launch vehicles are hydraulic systems. The Advanced Launch System (ALS), a joint initiative between NASA and the Air Force, is a launch vehicle that is designed to be cost effective, highly reliable and operationally efficient with a goal of reducing the cost per pound to orbit. As part of this initiative, an electromechanical actuation system is being developed as an attractive alternative to the hydraulic systems used today. NASA-Lewis is developing and demonstrating an Induction Motor Controller Actuation System with a 40 hp peak rating. The controller will integrate 20 kHz resonant link Power Management and Distribution (PMAD) technology and Pulse Population Modulation (PPM) techniques to implement Field Oriented Vector Control (FOVC) of a new advanced induction motor. Through PPM, multiphase variable frequency, variable voltage waveforms can be synthesized from the 20 kHz source. FOVC shows that varying both the voltage and frequency and their ratio (V/F), permits independent control of both torque and speed while operating at maximum efficiency at any point on the torque-speed curve. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a Built-in Test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA TVC system. The design and fabrication of the motor controller is being done by General Dynamics Space Systems Division. The University of Wisconsin-Madison will assist in the design of the advanced induction motor and in the implementation of the FOVC theory. A 75 hp electronically controlled dynamometer will be used to test the motor controller in all four quadrants of operation using flight type

  18. Glossina fuscipes populations provide insights for Human African Trypanosomiasis transmission in Uganda

    PubMed Central

    Aksoy, Serap; Caccone, Adalgisa; Galvani, Alison P.; Okedi, Loyce M.

    2013-01-01

    Uganda has both forms of human African trypanosomiasis (HAT): the chronic gambiense disease in the northwest and the acute rhodesiense disease in the south. The recent spread of rhodesiense into central Uganda has raised concerns given the different control strategies the two diseases require. We present knowledge on the population genetics of the major vector species Glossina fuscipes fuscipes in Uganda with a focus on population structure, measures of gene flow between populations, and the occurrence of polyandry. The microbiome composition and diversity is discussed, focusing on their potential role on trypanosome infection outcomes. We discuss the implications of these findings for large-scale tsetse control programs, including suppression or eradication, being undertaken in Uganda and potential future genetic applications. PMID:23845311

  19. Glossina fuscipes populations provide insights for human African trypanosomiasis transmission in Uganda.

    PubMed

    Aksoy, Serap; Caccone, Adalgisa; Galvani, Alison P; Okedi, Loyce M

    2013-08-01

    Uganda has both forms of human African trypanosomiasis (HAT): the chronic gambiense disease in the northwest and the acute rhodesiense disease in the south. The recent spread of rhodesiense into central Uganda has raised concerns given the different control strategies the two diseases require. We present knowledge on the population genetics of the major vector species Glossina fuscipes fuscipes in Uganda with a focus on population structure, measures of gene flow between populations, and the occurrence of polyandry. The microbiome composition and diversity is discussed, focusing on their potential role on trypanosome infection outcomes. We discuss the implications of these findings for large-scale tsetse control programs, including suppression or eradication, being undertaken in Uganda, and potential future genetic applications.

  20. Using species distribution models to optimize vector control in the framework of the tsetse eradication campaign in Senegal.

    PubMed

    Dicko, Ahmadou H; Lancelot, Renaud; Seck, Momar T; Guerrini, Laure; Sall, Baba; Lo, Mbargou; Vreysen, Marc J B; Lefrançois, Thierry; Fonta, William M; Peck, Steven L; Bouyer, Jérémy

    2014-07-15

    Tsetse flies are vectors of human and animal trypanosomoses in sub-Saharan Africa and are the target of the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). Glossina palpalis gambiensis (Diptera: Glossinidae) is a riverine species that is still present as an isolated metapopulation in the Niayes area of Senegal. It is targeted by a national eradication campaign combining a population reduction phase based on insecticide-treated targets (ITTs) and cattle and an eradication phase based on the sterile insect technique. In this study, we used species distribution models to optimize control operations. We compared the probability of the presence of G. p. gambiensis and habitat suitability using a regularized logistic regression and Maxent, respectively. Both models performed well, with an area under the curve of 0.89 and 0.92, respectively. Only the Maxent model predicted an expert-based classification of landscapes correctly. Maxent predictions were therefore used throughout the eradication campaign in the Niayes to make control operations more efficient in terms of deployment of ITTs, release density of sterile males, and location of monitoring traps used to assess program progress. We discuss how the models' results informed about the particular ecology of tsetse in the target area. Maxent predictions allowed optimizing efficiency and cost within our project, and might be useful for other tsetse control campaigns in the framework of the PATTEC and, more generally, other vector or insect pest control programs.

  1. Using species distribution models to optimize vector control in the framework of the tsetse eradication campaign in Senegal

    PubMed Central

    Dicko, Ahmadou H.; Lancelot, Renaud; Seck, Momar T.; Guerrini, Laure; Sall, Baba; Lo, Mbargou; Vreysen, Marc J. B.; Lefrançois, Thierry; Fonta, William M.; Peck, Steven L.; Bouyer, Jérémy

    2014-01-01

    Tsetse flies are vectors of human and animal trypanosomoses in sub-Saharan Africa and are the target of the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). Glossina palpalis gambiensis (Diptera: Glossinidae) is a riverine species that is still present as an isolated metapopulation in the Niayes area of Senegal. It is targeted by a national eradication campaign combining a population reduction phase based on insecticide-treated targets (ITTs) and cattle and an eradication phase based on the sterile insect technique. In this study, we used species distribution models to optimize control operations. We compared the probability of the presence of G. p. gambiensis and habitat suitability using a regularized logistic regression and Maxent, respectively. Both models performed well, with an area under the curve of 0.89 and 0.92, respectively. Only the Maxent model predicted an expert-based classification of landscapes correctly. Maxent predictions were therefore used throughout the eradication campaign in the Niayes to make control operations more efficient in terms of deployment of ITTs, release density of sterile males, and location of monitoring traps used to assess program progress. We discuss how the models’ results informed about the particular ecology of tsetse in the target area. Maxent predictions allowed optimizing efficiency and cost within our project, and might be useful for other tsetse control campaigns in the framework of the PATTEC and, more generally, other vector or insect pest control programs. PMID:24982143

  2. Mathematical models of human african trypanosomiasis epidemiology.

    PubMed

    Rock, Kat S; Stone, Chris M; Hastings, Ian M; Keeling, Matt J; Torr, Steve J; Chitnis, Nakul

    2015-03-01

    Human African trypanosomiasis (HAT), commonly called sleeping sickness, is caused by Trypanosoma spp. and transmitted by tsetse flies (Glossina spp.). HAT is usually fatal if untreated and transmission occurs in foci across sub-Saharan Africa. Mathematical modelling of HAT began in the 1980s with extensions of the Ross-Macdonald malaria model and has since consisted, with a few exceptions, of similar deterministic compartmental models. These models have captured the main features of HAT epidemiology and provided insight on the effectiveness of the two main control interventions (treatment of humans and tsetse fly control) in eliminating transmission. However, most existing models have overestimated prevalence of infection and ignored transient dynamics. There is a need for properly validated models, evolving with improved data collection, that can provide quantitative predictions to help guide control and elimination strategies for HAT.

  3. Vector and reservoir control for preventing leishmaniasis

    PubMed Central

    González, Urbà; Pinart, Mariona; Sinclair, David; Firooz, Alireza; Enk, Claes; Vélez, Ivan D; Esterhuizen, Tonya M; Tristan, Mario; Alvar, Jorge

    2015-01-01

    Background Leishmaniasis is caused by the Leishmania parasite, and transmitted by infected phlebotomine sandflies. Of the two distinct clinical syndromes, cutaneous leishmaniasis (CL) affects the skin and mucous membranes, and visceral leishmaniasis (VL) affects internal organs. Approaches to prevent transmission include vector control by reducing human contact with infected sandflies, and reservoir control, by reducing the number of infected animals. Objectives To assess the effects of vector and reservoir control interventions for cutaneous and for visceral leishmaniasis. Search methods We searched the following databases to 13 January 2015: Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, EMBASE, LILACS and WHOLIS, Web of Science, and RePORTER. We also searched trials registers for ongoing trials. Selection criteria Randomized controlled trials (RCTs) evaluating the effects of vector and reservoir control interventions in leishmaniasis-endemic regions. Data collection and analysis Two review authors independently searched for trials and extracted data from included RCTs. We resolved any disagreements by discussion with a third review author. We assessed the quality of the evidence using the GRADE approach. Main results We included 14 RCTs that evaluated a range of interventions across different settings. The study methods were generally poorly described, and consequently all included trials were judged to be at high or unclear risk of selection and reporting bias. Only seven trials reported clinical outcome data which limits our ability to make broad generalizations to different epidemiological settings and cultures. Cutaneous leishmaniasis One four-arm RCT from Afghanistan compared indoor residual spraying (IRS), insecticide-treated bednets (ITNs), and insecticide-treated bedsheets, with no intervention. Over 15 months follow-up, all three insecticide-based interventions had a lower incidence of CL than the control area (IRS: risk

  4. The Role of Spatial Statistics in the Control and Elimination of Neglected Tropical Diseases in Sub-Saharan Africa: A Focus on Human African Trypanosomiasis, Schistosomiasis and Lymphatic Filariasis.

    PubMed

    Stanton, M C

    2017-01-01

    Disease control and elimination programmes can benefit greatly from accurate information on the spatial variability of disease risk, particularly when risk is highly spatially heterogeneous. Due to advances in statistical methodology, coupled with the increased availability of geospatial technology, this information is becoming increasingly accessible. In this chapter we describe recent advancements in spatial methods associated with the analysis of disease data measured at the point-level and demonstrate their application to the control and elimination of neglected tropical diseases (NTDs). We further provide information on spatially referenced data sources and software that can be used to create NTD risk maps, concentrating on those that can be freely obtained. Examples relating to three NTDs affecting populations in sub-Saharan Africa are presented throughout the chapter, i.e., human African trypanosomiasis, schistosomiasis and lymphatic filariasis. These three diseases, with differing routes of transmission, control methods and level of spatial heterogeneity, demonstrate the flexibility and applicability of the methods described.

  5. Vector snail control in Qalyub, Egypt

    PubMed Central

    van der Schalie, Henry

    1958-01-01

    The author describes a pilot study in vector snail control carried out in 1953-54 by the Bilharziasis Control Project in Qalyub, Egypt. After giving a brief description of the site chosen for the Project—an area of some 5000 acres (2000 hectares) under perennial irrigation—he presents a detailed account of the various snail surveys of the irrigation canals and drains and of the molluscicidal treatment of infested channels. He points out that despite the thoroughness of the surveying and treatment the snails were not completely eliminated from the area and stresses that the high cost of the molluscicide used (copper sulfate) would prohibit its widespread and continual use. He considers, however, that pending the perfection of such long-term bilharziasis control measures as improved sanitation, better treatment facilities, and health education of the public, snail control is of the first importance and determined efforts should be made to find more efficient and cheaper methods of effecting it. PMID:13585074

  6. Paratransgenic Control of Vector Borne Diseases

    PubMed Central

    Hurwitz, Ivy; Fieck, Annabeth; Read, Amber; Hillesland, Heidi; Klein, Nichole; Kang, Angray; Durvasula, Ravi

    2011-01-01

    Conventional methodologies to control vector borne diseases with chemical pesticides are often associated with environmental toxicity, adverse effects on human health and the emergence of insect resistance. In the paratransgenic strategy, symbiotic or commensal microbes of host insects are transformed to express gene products that interfere with pathogen transmission. These genetically altered microbes are re-introduced back to the insect where expression of the engineered molecules decreases the host's ability to transmit the pathogen. We have successfully utilized this strategy to reduce carriage rates of Trypanosoma cruzi, the causative agent of Chagas disease, in the triatomine bug, Rhodnius prolixus, and are currently developing this methodology to control the transmission of Leishmania donovani by the sand fly Phlebotomus argentipes. Several effector molecules, including antimicrobial peptides and highly specific single chain antibodies, are currently being explored for their anti-parasite activities in these two systems. In preparation for eventual field use, we are actively engaged in risk assessment studies addressing the issue of horizontal gene transfer from the modified bacteria to environmental microbes. PMID:22110385

  7. Thrust Vector Control for Nuclear Thermal Rockets

    NASA Technical Reports Server (NTRS)

    Ensworth, Clinton B. F.

    2013-01-01

    Future space missions may use Nuclear Thermal Rocket (NTR) stages for human and cargo missions to Mars and other destinations. The vehicles are likely to require engine thrust vector control (TVC) to maintain desired flight trajectories. This paper explores requirements and concepts for TVC systems for representative NTR missions. Requirements for TVC systems were derived using 6 degree-of-freedom models of NTR vehicles. Various flight scenarios were evaluated to determine vehicle attitude control needs and to determine the applicability of TVC. Outputs from the models yielded key characteristics including engine gimbal angles, gimbal rates and gimbal actuator power. Additional factors such as engine thrust variability and engine thrust alignment errors were examined for impacts to gimbal requirements. Various technologies are surveyed for TVC systems for the NTR applications. A key factor in technology selection is the unique radiation environment present in NTR stages. Other considerations including mission duration and thermal environments influence the selection of optimal TVC technologies. Candidate technologies are compared to see which technologies, or combinations of technologies best fit the requirements for selected NTR missions. Representative TVC systems are proposed and key properties such as mass and power requirements are defined. The outputs from this effort can be used to refine NTR system sizing models, providing higher fidelity definition for TVC systems for future studies.

  8. Paratransgenic control of vector borne diseases.

    PubMed

    Hurwitz, Ivy; Fieck, Annabeth; Read, Amber; Hillesland, Heidi; Klein, Nichole; Kang, Angray; Durvasula, Ravi

    2011-01-01

    Conventional methodologies to control vector borne diseases with chemical pesticides are often associated with environmental toxicity, adverse effects on human health and the emergence of insect resistance. In the paratransgenic strategy, symbiotic or commensal microbes of host insects are transformed to express gene products that interfere with pathogen transmission. These genetically altered microbes are re-introduced back to the insect where expression of the engineered molecules decreases the host's ability to transmit the pathogen. We have successfully utilized this strategy to reduce carriage rates of Trypanosoma cruzi, the causative agent of Chagas disease, in the triatomine bug, Rhodnius prolixus, and are currently developing this methodology to control the transmission of Leishmania donovani by the sand fly Phlebotomus argentipes. Several effector molecules, including antimicrobial peptides and highly specific single chain antibodies, are currently being explored for their anti-parasite activities in these two systems. In preparation for eventual field use, we are actively engaged in risk assessment studies addressing the issue of horizontal gene transfer from the modified bacteria to environmental microbes.

  9. Future treatment options for human African trypanosomiasis.

    PubMed

    Jones, Amy J; Avery, Vicky M

    2015-01-01

    Over the past 17 years, the number of reported cases of human African trypanosomiasis (HAT) has declined by over 90%, a significant result since the disease was highlighted as a public health problem by the WHO in 1995. However, if the goal of eliminating HAT by 2020 is to be achieved, then new treatments need to be identified and developed. A plethora of compound collections has been screened against Trypanosoma brucei spp, the etiological agents of HAT, resulting in three compounds progressing to clinical development. However, due to the high attrition rates in drug discovery, it is essential that research continues to identify novel molecules. Failure to do so, will result in the absence of molecules in the pipeline to fall back on should the current clinical trials be unsuccessful. This could seriously compromise control efforts to date, resulting in a resurgence in the number of HAT cases.

  10. New Highly Dynamic Approach for Thrust Vector Control

    NASA Astrophysics Data System (ADS)

    Hecht, M.; Ettl, J.; Grothe, D.; Hrbud, I.

    2015-09-01

    For a new launcher system a thrust vector control system is needed. This launch vehicle system consists of two rockets which are namely the VS-50 (two-stage suborbital vehicle) and the VLM-1 (three-stage microsatellite launch vehicle). VLM-1 and VS-50 are developed in a cooperation between the German Aerospace Center (DLR) and the Brazilian Aeronautics and Space Institute (IAE). To keep these two rockets on its trajectory during flight a highly dynamic thrust vector control system is required. For the purpose of developing such a highly dynamic thrust vector control system a master thesis was written by the author. The development includes all mechanical constructions as well as control algorithms and electronics design. Moreover an optimization of control algorithms was made to increase the dynamic capabilities of the thrust vector control system. The composition of the right components plus the sophisticated control algorithm make the thrust vector control system highly dynamic.

  11. Molecular evidence of a Trypanosoma brucei gambiense sylvatic cycle in the human african trypanosomiasis foci of Equatorial Guinea

    PubMed Central

    Cordon-Obras, Carlos; Rodriguez, Yasmin Fermin; Fernandez-Martinez, Amalia; Cano, Jorge; Ndong-Mabale, Nicolas; Ncogo-Ada, Policarpo; Ndongo-Asumu, Pedro; Aparicio, Pilar; Navarro, Miguel; Benito, Agustin; Bart, Jean-Mathieu

    2015-01-01

    Gambiense trypanosomiasis is considered an anthroponotic disease. Consequently, control programs are generally aimed at stopping transmission of Trypanosoma brucei gambiense (T. b. gambiense) by detecting and treating human cases. However, the persistence of numerous foci despite efforts to eliminate this disease questions this strategy as unique tool to pursue the eradication. The role of animals as a reservoir of T. b. gambiense is still controversial, but could partly explain maintenance of the infection at hypo-endemic levels. In the present study, we evaluated the presence of T. b. gambiense in wild animals in Equatorial Guinea. The infection rate ranged from 0.8% in the insular focus of Luba to more than 12% in Mbini, a focus with a constant trickle of human cases. The parasite was detected in a wide range of animal species including four species never described previously as putative reservoirs. Our study comes to reinforce the hypothesis that animals may play a role in the persistence of T. b. gambiense transmission, being particularly relevant in low transmission settings. Under these conditions the integration of sustained vector control and medical interventions should be considered to achieve the elimination of gambiense trypanosomiasis. PMID:26257727

  12. Exploiting the potential of vector control for disease prevention.

    PubMed Central

    Townson, H.; Nathan, M. B.; Zaim, M.; Guillet, P.; Manga, L.; Bos, R.; Kindhauser, M.

    2005-01-01

    Although vector control has proven highly effective in preventing disease transmission, it is not being used to its full potential, thereby depriving disadvantaged populations of the benefits of well tried and tested methods. Following the discovery of synthetic residual insecticides in the 1940s, large-scale programmes succeeded in bringing many of the important vector-borne diseases under control. By the late 1960s, most vector-borne diseases--with the exception of malaria in Africa--were no longer considered to be of primary public health importance. The result was that control programmes lapsed, resources dwindled, and specialists in vector control disappeared from public health units. Within two decades, many important vector-borne diseases had re-emerged or spread to new areas. The time has come to restore vector control to its key role in the prevention of disease transmission, albeit with an increased emphasis on multiple measures, whether pesticide-based or involving environmental modification, and with a strengthened managerial and operational capacity. Integrated vector management provides a sound conceptual framework for deployment of cost-effective and sustainable methods of vector control. This approach allows for full consideration of the complex determinants of disease transmission, including local disease ecology, the role of human activity in increasing risks of disease transmission, and the socioeconomic conditions of affected communities. PMID:16462987

  13. Dynamic Model Based Vector Control of Linear Induction Motor

    DTIC Science & Technology

    2012-05-01

    reference frame. In Section III, the basic structure of vector control is introduced. Proportional-Integral ( PI ) control is incorporated into vector...The load mass is then released from the slider. The performed simulation is based on selected PI control gains of Kp = 35 and KI = 75. Fig. 12 shows...controlled separately to maintain a desired flux level in the machine. The force current Isq is proportional to the load which is regulated using a PI

  14. Chemotherapy of human African trypanosomiasis.

    PubMed

    Burchmore, Richard J S; Ogbunude, Patrick O J; Enanga, Bertin; Barrett, Michael P

    2002-01-01

    Human African trypanosomiasis or sleeping sickness is resurgent [1,2]. The disease is caused by subspecies of the parasitic haemoflagellate, Trypanosoma brucei. Infection starts with the bite of an infected tsetse fly (Glossina spp.). Parasites move from the site of infection to the draining lymphatic vessels and blood stream. The parasites proliferate within the bloodstream and later invade other tissues including the central nervous system. Once they have established themselves within the CNS, a progressive breakdown of neurological function accompanies the disease. Coma precedes death during this late phase. Two forms of the disease are recognised, one caused by Trypanosoma brucei rhodesiense, endemic in Eastern and Southern Africa, in which parasites rapidly invade the CNS causing death within weeks if untreated. T. b. gambiense, originally described in West Africa, but also widespread in Central Africa, proliferates more slowly and can take several years before establishing a CNS-involved infection. Many countries are in the midst of epidemics caused by gambiense-type parasites. Four drugs have been licensed to treat the disease [3]; two of them, pentamidine and suramin, are used prior to CNS involvement. The arsenic-based drug, melarsoprol is used once parasites are established in the CNS. The fourth, eflornithine, is effective against late stage disease caused by T. b. gambiense, but is ineffective against T. b. rhodesiense. Another drug, nifurtimox is licensed for South American trypanosomiasis but also been used in trials against melarsoprol-refractory late sage disease. This review focuses on what is known about modes of action of current drugs and discusses targets for future drug development.

  15. Addressing malaria vector control challenges in South Sudan: proposed recommendations.

    PubMed

    Chanda, Emmanuel; Doggale, Constantino; Pasquale, Harriet; Azairwe, Robert; Baba, Samson; Mnzava, Abraham

    2013-02-08

    Upon the signing of the Comprehensive Peace Agreement in 2005, the Republic of South Sudan (RSS) has faced a lot of challenges, such as a lack of infrastructure, human resources and an enormous burden of vector borne diseases including malaria. While a national malaria strategic plan 2006-2011 was developed, the vector control component has remained relatively weak. The strategy endorses the distribution of long-lasting insecticidal nets (LLINs) as the frontline intervention with other interventions recommended only when technical and institutional capacity is available. In 2006, a draft integrated vector management (IVM) strategic plan 2007-2012 was developed but never implemented, resulting in minimal coordination, implementation and coverage of malaria vector control tools including their inherent impact. To address this challenge, the vector control team of the National Malaria Control Programme (NMCP) is being strengthened. With the objective of building national capacity and technical collaboration for effective implementation of the IVM strategy, a national malaria vector control conference was held from 15-17th October 2012 in Juba. A range of NMCP partners, state ministries, acadaemia, private sector, national and international non-governmental organizations, including regional and global policymakers attended the meeting. The conference represented a major milestone and made recommendations revolving around the five key elements of the IVM approach. The meeting endorsed that vector control efforts in RSS be augmented with other interventions within the confines of the IVM strategy as a national approach, with strong adherence to its key elements.

  16. Hot Ball and Socket Thrust Vector Control

    DTIC Science & Technology

    1982-03-01

    idCmonstratd slngl e plane vectoring of V6 dog at mý vver.e• preesure of’ 850 rsl•a for 1I1inc. The meaond, temtfm at C3) in Augucvt 1ý4(1 under Naval...duration * Successful vectoring through 16 dog of travel for the first 17.3 see, including deflection to the planned maximum angle of 8 deg KA Cotnmand to...drawing C13179-01-01, "Stat.ic Teat AAsembly - Hot BmlI and Socket. 8 Dog . TVC Capability"’. Phys.ical characteriticR of the nozzle asnemb.y deplcted in

  17. Controlled removal of a nonviral episomal vector from transfected cells.

    PubMed

    Rupprecht, Sina; Hagedorn, Claudia; Seruggia, Davide; Magnusson, Terese; Wagner, Ernst; Ogris, Manfred; Lipps, Hans J

    2010-10-15

    An ideal vector to be used in gene therapy should allow long-term and regulated expression of the therapeutic sequence, but in many cases, it would be most desirable to remove all ectopic vector sequences from the cell once expression is no longer required. The vector pEPI is the first nonviral autonomous replicon that was constructed for mammalian cells. It represents a minimal model system to study the epigenetic regulation of replication and transcription but is also regarded as a promising alternative to currently used viral vector systems in gene therapy. Its function relies on a transcription unit linked to an S/MAR sequence. We constructed an inducible pEPI vector system based on the Tet ON system in which transcription is switched on in the presence of doxycycline. We show that for vector replication and long-term maintenance an ongoing transcription running into the S/MAR element is required. Once established, the vector is lost from the cell upon switching off transcription from the gene linked to the S/MAR. This feature provides not only controlled transgene expression but also the possibility to remove all vector molecules from the cells upon demand. This inducible episomal nonviral vector system will find broad application in gene therapy but also in reprogramming of somatic cells or modification of stem cells.

  18. Is Vector Control Sufficient to Limit Pathogen Spread in Vineyards?

    PubMed

    Daugherty, M P; O'Neill, S; Byrne, F; Zeilinger, A

    2015-06-01

    Vector control is widely viewed as an integral part of disease management. Yet epidemiological theory suggests that the effectiveness of control programs at limiting pathogen spread depends on a variety of intrinsic and extrinsic aspects of a pathosystem. Moreover, control programs rarely evaluate whether reductions in vector density or activity translate into reduced disease prevalence. In areas of California invaded by the glassy-winged sharpshooter (Homalodisca vitripennis Germar), Pierce's disease management relies heavily on chemical control of this vector, primarily via systemic conventional insecticides (i.e., imidacloprid). But, data are lacking that attribute reduced vector pressure and pathogen spread to sharpshooter control. We surveyed 34 vineyards over successive years to assess the epidemiological value of within-vineyard chemical control. The results showed that imidacloprid reduced vector pressure without clear nontarget effects or secondary pest outbreaks. Effects on disease prevalence were more nuanced. Treatment history over the preceding 5 yr affected disease prevalence, with significantly more diseased vines in untreated compared with regularly or intermittently treated vineyards. Yet, the change in disease prevalence between years was low, with no significant effects of insecticide treatment or vector abundance. Collectively, the results suggest that within-vineyard applications of imidacloprid can reduce pathogen spread, but with benefits that may take multiple seasons to become apparent. The relatively modest effect of vector control on disease prevalence in this system may be attributable in part to the currently low regional sharpshooter population densities stemming from area-wide control, without which the need for within-vineyard vector control would be more pronounced.

  19. Current Trends in Vector Control: Adapting to Selective Pressure

    DTIC Science & Technology

    2008-11-16

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP023975 TITLE: Current Trends in Vector Control: Adapting to Selective...ADP023967 thru ADP023976 UNCLASSIFIED Current Trends in Vector Control: Adapting to Selective Pressure Kendra Lawrence MAJ, Medical Service Corps...of Research, is to mitigate the products to the forefront that may fulfill risk posed by arthropods to DoD mission needs. The Department of personnel

  20. From population structure to genetically-engineered vectors: new ways to control vector-borne diseases?

    PubMed

    Sparagano, O A E; De Luna, C J

    2008-07-01

    Epidemiological studies on vectors and the pathogens they can carry (such as Borrelia burgdorferi) are showing some correlations between infection rates and biodiversity highlighting the "dilution" effects on potential vectors. Meanwhile other studies comparing sympatric small rodent species demonstrated that rodent species transmitting more pathogens are parasitized by more ectoparasite species. Studies on population structure and size have also proven a difference on the intensity of the parasitic infection. Furthermore, preliminary results in genetic improvement in mosquitoes (genetic markers, sexing, and genetic sterilization) will also increase performance as it has already been shown in field applications in developing countries. Recent results have greatly improved the fitness of genetically-modified insects compared to wild type populations with new approaches such as the post-integration elimination of transposon sequences, stabilising any insertion in genetically-modified insects. Encouraging results using the Sterile Insect Technique highlighted some metabolism manipulation to avoid the viability of offspring from released parent insect in the wild. Recent studies on vector symbionts would also bring a new angle in vector control capabilities, while complete DNA sequencing of some arthropods could point out ways to block the deadly impact on animal and human populations. These new potential approaches will improve the levels of control or even in some cases would eradicate vector species and consequently the vector-borne diseases they can transmit. In this paper we review some of the population biology theories, biological control methods, and the genetic techniques that have been published in the last years that are recommended to control for vector-borne diseases.

  1. The Interaction between Vector Life History and Short Vector Life in Vector-Borne Disease Transmission and Control

    PubMed Central

    Brand, Samuel P. C.; Keeling, Matt J.

    2016-01-01

    Epidemiological modelling has a vital role to play in policy planning and prediction for the control of vectors, and hence the subsequent control of vector-borne diseases. To decide between competing policies requires models that can generate accurate predictions, which in turn requires accurate knowledge of vector natural histories. Here we highlight the importance of the distribution of times between life-history events, using short-lived midge species as an example. In particular we focus on the distribution of the extrinsic incubation period (EIP) which determines the time between infection and becoming infectious, and the distribution of the length of the gonotrophic cycle which determines the time between successful bites. We show how different assumptions for these periods can radically change the basic reproductive ratio (R0) of an infection and additionally the impact of vector control on the infection. These findings highlight the need for detailed entomological data, based on laboratory experiments and field data, to correctly construct the next-generation of policy-informing models. PMID:27128163

  2. The Interaction between Vector Life History and Short Vector Life in Vector-Borne Disease Transmission and Control.

    PubMed

    Brand, Samuel P C; Rock, Kat S; Keeling, Matt J

    2016-04-01

    Epidemiological modelling has a vital role to play in policy planning and prediction for the control of vectors, and hence the subsequent control of vector-borne diseases. To decide between competing policies requires models that can generate accurate predictions, which in turn requires accurate knowledge of vector natural histories. Here we highlight the importance of the distribution of times between life-history events, using short-lived midge species as an example. In particular we focus on the distribution of the extrinsic incubation period (EIP) which determines the time between infection and becoming infectious, and the distribution of the length of the gonotrophic cycle which determines the time between successful bites. We show how different assumptions for these periods can radically change the basic reproductive ratio (R0) of an infection and additionally the impact of vector control on the infection. These findings highlight the need for detailed entomological data, based on laboratory experiments and field data, to correctly construct the next-generation of policy-informing models.

  3. Integrated epidemiology for vector-borne zoonoses.

    PubMed

    Wardrop, Nicola A

    2016-02-01

    The development and application of interventions for the control of vector-borne zoonoses requires broad understanding of epidemiological linkages between vector, animal infection and human infection. However, there are significant gaps in our understanding of these linkages and a lack of appropriate data poses a considerable barrier to addressing this issue. A move towards strengthened surveillance of vectors and disease in both animal and human hosts, in combination with linked human-animal surveys, could form the backbone for epidemiological integration, enabling explicit assessment of the animal-human (and vector) interface, and subsequent implications for spill-over to human populations. Currently available data on the spatial distribution of human African trypanosomiasis allow an illustrative example.

  4. Drug resistance in human African trypanosomiasis.

    PubMed

    Barrett, Michael P; Vincent, Isabel M; Burchmore, Richard J S; Kazibwe, Anne J N; Matovu, Enock

    2011-09-01

    Human African trypanosomiasis or 'sleeping sickness' is a neglected tropical disease caused by the parasite Trypanosoma brucei. A decade of intense international cooperation has brought the incidence to fewer than 10,000 reported cases per annum with anti-trypanosomal drugs, particularly against stage 2 disease where the CNS is involved, being central to control. Treatment failures with melarsoprol started to appear in the 1990s and their incidence has risen sharply in many foci. Loss of plasma membrane transporters involved in drug uptake, particularly the P2 aminopurine transporter and also a transporter termed the high affinity pentamidine transporter, relate to melarsoprol resistance selected in the laboratory. The same two transporters are also responsible for the uptake of the stage 1 drug pentamidine and, to varying extents, other diamidines. However, reports of treatment failures with pentamidine have been rare from the field. Eflornithine (difluoromethylornithine) has replaced melarsoprol as first-line treatment in many regions. However, a need for protracted and complicated drug dosing regimens slowed widespread implementation of eflornithine monotherapy. A combination of eflornithine with nifurtimox substantially decreases the required dose and duration of eflornithine administration and this nifurtimox-eflornithine combination therapy has enjoyed rapid implementation. Unfortunately, selection of resistance to eflornithine in the laboratory is relatively easy (through loss of an amino acid transporter believed to be involved in its uptake), as is selection of resistance to nifurtimox. The first anecdotal reports of treatment failures with eflornithine monotherapy are emerging from some foci. The possibility that parasites resistant to melarsoprol on the one hand, and eflornithine on the other, are present in the field indicates that genes capable of conferring drug resistance to both drugs are in circulation. If new drugs, that act in ways that will not

  5. Control of vector populations using genetically modified mosquitoes.

    PubMed

    Wilke, André Barreto Bruno; Gomes, Almério de Castro; Natal, Delsio; Marrelli, Mauro Toledo

    2009-10-01

    The ineffectiveness of current strategies for chemical control of mosquito vectors raises the need for developing novel approaches. Thus, we carried out a literature review of strategies for genetic control of mosquito populations based on the sterile insect technique. One of these strategies consists of releasing radiation-sterilized males into the population; another, of integrating a dominant lethal gene under the control of a specific promoter into immature females. Advantages of these approaches over other biological and chemical control strategies include: highly species-specific, environmentally safety, low production cost, and high efficacy. The use of this genetic modification technique will constitute an important tool for integrated vector management.

  6. Parallel and vector computation for stochastic optimal control applications

    NASA Technical Reports Server (NTRS)

    Hanson, F. B.

    1989-01-01

    A general method for parallel and vector numerical solutions of stochastic dynamic programming problems is described for optimal control of general nonlinear, continuous time, multibody dynamical systems, perturbed by Poisson as well as Gaussian random white noise. Possible applications include lumped flight dynamics models for uncertain environments, such as large scale and background random atmospheric fluctuations. The numerical formulation is highly suitable for a vector multiprocessor or vectorizing supercomputer, and results exhibit high processor efficiency and numerical stability. Advanced computing techniques, data structures, and hardware help alleviate Bellman's curse of dimensionality in dynamic programming computations.

  7. A role for vector control in dengue vaccine programs.

    PubMed

    Christofferson, Rebecca C; Mores, Christopher N

    2015-12-10

    Development and deployment of a successful dengue virus (DENV) vaccine has confounded research and pharmaceutical entities owing to the complex nature of DENV immunity and concerns over exacerbating the risk of DENV hemorrhagic fever (DHF) as a consequence of vaccination. Thus, consensus is growing that a combination of mitigation strategies will be needed for DENV to be successfully controlled, likely involving some form of vector control to enhance a vaccine program. We present here a deterministic compartmental model to illustrate that vector control may enhance vaccination campaigns with imperfect coverage and efficacy. Though we recognize the costs and challenges associated with continuous control programs, simultaneous application of vector control methods coincident with vaccine roll out can have a positive effect by further reducing the number of human cases. The success of such an integrative strategy is predicated on closing gaps in our understanding of the DENV transmission cycle in hyperedemic locations.

  8. A changing environment and the epidemiology of tsetse-transmitted livestock trypanosomiasis.

    PubMed

    Van den Bossche, Peter; de La Rocque, Stéphane; Hendrickx, Guy; Bouyer, Jérémy

    2010-05-01

    The distribution, prevalence and impact of vector-borne diseases are often affected by anthropogenic environmental changes that alter the interactions between the host, the parasite and the vector. In the case of tsetse-transmitted livestock trypanosomiasis these changes are a result of the encroachment of people and their livestock into tsetse-infected wild areas. This has created a sequence of new epidemiological settings that is changing the relative importance of the domestic or sylvatic trypanosome transmission cycles and is causing concomitant changes in the impact of the disease on livestock. These changes in the dynamics of the epidemiology have an important impact on the factors that need to be considered when developing area-specific strategies for the future management of tsetse-transmitted livestock trypanosomiasis.

  9. Robust nonlinear control of vectored thrust aircraft

    NASA Technical Reports Server (NTRS)

    Doyle, John C.; Murray, Richard; Morris, John

    1993-01-01

    An interdisciplinary program in robust control for nonlinear systems with applications to a variety of engineering problems is outlined. Major emphasis will be placed on flight control, with both experimental and analytical studies. This program builds on recent new results in control theory for stability, stabilization, robust stability, robust performance, synthesis, and model reduction in a unified framework using Linear Fractional Transformations (LFT's), Linear Matrix Inequalities (LMI's), and the structured singular value micron. Most of these new advances have been accomplished by the Caltech controls group independently or in collaboration with researchers in other institutions. These recent results offer a new and remarkably unified framework for all aspects of robust control, but what is particularly important for this program is that they also have important implications for system identification and control of nonlinear systems. This combines well with Caltech's expertise in nonlinear control theory, both in geometric methods and methods for systems with constraints and saturations.

  10. A Quasioptical Vector Interferometer for Polarization Control

    NASA Technical Reports Server (NTRS)

    Chuss, David T.; Wollack, Edward J.; Moseley, Harvey S.; Novak, Giles

    2005-01-01

    We present a mathematical description of a Quasioptical Vector Interferometer (QVI), a device that maps an input polarization state to an output polarization state by introducing a phase delay between two linear orthogonal components of the input polarization. The advantages of such a device over a spinning wave-plate modulator for measuring astronomical polarization in the far-infrared through millimeter are: 1. The use of small, linear motions eliminates the need for cryogenic rotational bearings, 2. The phase flexibility allows measurement of Stokes V as well as Q and U, and 3. The QVI allows for both multi-wavelength and broadband modulation. We suggest two implementations of this device as an astronomical polarization modulator. The first involves two such modulators placed in series. By adjusting the two phase delays, it is possible to use such a modulator to measure Stokes Q, U, and V for passbands that are not too large. Conversely, a single QVI may be used to measure Q and V independent of frequency. In this implementation, Stokes U must be measured by rotating the instrument. We conclude this paper by presenting initial laboratory results.

  11. Abnormal biochemical and haematological indices in trypanosomiasis as a threat to herd production.

    PubMed

    Ohaeri, C C; Eluwa, M C

    2011-05-11

    Blood samples were collected from 46 domestic ruminants comprising of 23 trypanosomiasis infected and 23 uninfected control groups to study some biochemical and haematological effects of trypanosomiasis under natural condition. The effect of trypanosome infection in ruminant animals showed that infected animals had significantly lower (P<0.05) packed cell volume, erythrocyte count and higher (P<0.01) mean cell volumes than uninfected animals. Leucocytosis, reticulocytosis and thrombocytopenia were also observed. The infection also produced a decrease in albumin (P<0.001), significant increase in total protein and bilirubin levels. These changes were not seen in the animals that were not infected. The outcome of the work shows that herds are severely affected by the disease, and therefore supports the prospect of routine check as an epidemiologic tool in trypanosomiasis based on its abnormal effects in blood.

  12. The population structure of Glossina fuscipes fuscipes in the Lake Victoria basin in Uganda: implications for vector control

    PubMed Central

    2012-01-01

    Background Glossina fuscipes fuscipes is the primary vector of trypanosomiasis in humans and livestock in Uganda. The Lake Victoria basin has been targeted for tsetse eradication using a rolling carpet initiative, from west to east, with four operational blocks (3 in Uganda and 1 in Kenya), under a Pan-African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). We screened tsetse flies from the three Ugandan PATTEC blocks for genetic diversity at 15 microsatellite loci from continental and offshore populations to provide empirical data to support this initiative. Methods We collected tsetse samples from 11 sites across the Lake Victoria basin in Uganda. We performed genetic analyses on 409 of the collected tsetse flies and added data collected for 278 individuals in a previous study. The flies were screened across 15 microsatellite loci and the resulting data were used to assess the temporal stability of populations, to analyze patterns of genetic exchange and structuring, to estimate dispersal rates and evaluate the sex bias in dispersal, as well as to estimate demographic parameters (NE and NC). Results We found that tsetse populations in this region were stable over 4-16 generations and belong to 4 genetic clusters. Two genetic clusters (1 and 2) corresponded approximately to PATTEC blocks 1 and 2, while the other two (3 and 4) fell within PATTEC block 3. Island populations grouped into the same genetic clusters as neighboring mainland sites, suggesting presence of gene flow between these sites. There was no evidence of the stretch of water separating islands from the mainland forming a significant barrier to dispersal. Dispersal rates ranged from 2.5 km per generation in cluster 1 to 14 km per generation in clusters 3 and 4. We found evidence of male-biased dispersal. Few breeders are successfully dispersing over large distances. Effective population size estimates were low (33–310 individuals), while census size estimates ranged from 1200 (cluster

  13. Vector Control and Surveillance Operations in the Republic of Singapore

    PubMed Central

    Yoshikawa, Minako Jen

    2013-01-01

    Singapore is known for its comprehensive vector control methods that keep mosquito populations at low levels in the urban, tropical, and green city-state. This report describes the measures taken by the National Environment Agency on the basis of observations of vector control and surveillance activities in residential areas, construction sites, and foreign worker quarters. The government-led active operations dealt not only with mosquito control but also social issues in urban residential buildings where people with varying preferences live, the responsibilities of the business sector, and the education of multi-cultural/lingual residents and foreign workers. The public health measures implemented in Singapore offer useful ideas to countries/cities that have not yet established vector control programs against mosquito-borne infectious diseases. PMID:23874140

  14. Implementation of a new fuzzy vector control of induction motor.

    PubMed

    Rafa, Souad; Larabi, Abdelkader; Barazane, Linda; Manceur, Malik; Essounbouli, Najib; Hamzaoui, Abdelaziz

    2014-05-01

    The aim of this paper is to present a new approach to control an induction motor using type-1 fuzzy logic. The induction motor has a nonlinear model, uncertain and strongly coupled. The vector control technique, which is based on the inverse model of the induction motors, solves the coupling problem. Unfortunately, in practice this is not checked because of model uncertainties. Indeed, the presence of the uncertainties led us to use human expertise such as the fuzzy logic techniques. In order to maintain the decoupling and to overcome the problem of the sensitivity to the parametric variations, the field-oriented control is replaced by a new block control. The simulation results show that the both control schemes provide in their basic configuration, comparable performances regarding the decoupling. However, the fuzzy vector control provides the insensitivity to the parametric variations compared to the classical one. The fuzzy vector control scheme is successfully implemented in real-time using a digital signal processor board dSPACE 1104. The efficiency of this technique is verified as well as experimentally at different dynamic operating conditions such as sudden loads change, parameter variations, speed changes, etc. The fuzzy vector control is found to be a best control for application in an induction motor.

  15. Drugs and drug resistance in African trypanosomiasis.

    PubMed

    Delespaux, Vincent; de Koning, Harry P

    2007-01-01

    Despite the many decades of use of most of the current trypanocides, we know little of their mode of action. This may in part be because most of these will act on multiple targets once inside the cell, and they derive their selective action on the parasite from selective accumulation by the pathogen. Loss of this capacity for drug uptake by the trypanosome would thus be a major cause for drug resistance. We here discuss the use of current drugs against human and veterinary African trypanosomiasis, the prevalence, causes and mechanisms of drug resistance and new developments in trypanosomiasis therapy such as the introduction of nifurtimox and DB289.

  16. Spray characterization of ULV sprayers typically used in vector control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous spray machines are used to apply products for the control of human disease vectors, such as mosquitoes and flies. However, the selection and setup of these machines significantly affect the level of control achieved during an application. The droplet spectra produced by nine different ULV...

  17. Dengue and Chikungunya Vector Control Pocket Guide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This technical guide consolidates information and procedures for surveillance and control of mosquitoes that transmit dengue and chikungunya viruses. The guide focuses on mosquitoes that transmit dengue but also makes reference to chikungunya and yellow fever because the pathogens that cause these ...

  18. Prospects for vector control through genetic manipulation of populations*

    PubMed Central

    Craig, George B.

    1963-01-01

    Since the development of insecticide-resistance and the consequent partial failure of the chemical approach to the control of disease vectors, interest in the biological approach has re-awakened. An aspect of the latter approach that is of great current interest is “autocidal control”—that is, the use of insects for their own destruction. This paper discusses the various ways in which genetic mechanisms can be used to bring about the destruction of harmful insects, with special reference to those of medical importance. The author considers that the prospects for the genetic control of vector species are good, but stresses that before genetic methods can be applied on a field scale certain requirements must be met. For example, genetic technology must be expanded, a firm background of genetic knowledge of vector species must be built up, a great deal more information about vector ecology, particularly population dynamics, must be acquired, and techniques for the mass production of vector insects under controlled conditions must be developed. PMID:20604180

  19. A critical assessment of vector control for dengue prevention.

    PubMed

    Achee, Nicole L; Gould, Fred; Perkins, T Alex; Reiner, Robert C; Morrison, Amy C; Ritchie, Scott A; Gubler, Duane J; Teyssou, Remy; Scott, Thomas W

    2015-05-01

    Recently, the Vaccines to Vaccinate (v2V) initiative was reconfigured into the Partnership for Dengue Control (PDC), a multi-sponsored and independent initiative. This redirection is consistent with the growing consensus among the dengue-prevention community that no single intervention will be sufficient to control dengue disease. The PDC's expectation is that when an effective dengue virus (DENV) vaccine is commercially available, the public health community will continue to rely on vector control because the two strategies complement and enhance one another. Although the concept of integrated intervention for dengue prevention is gaining increasingly broader acceptance, to date, no consensus has been reached regarding the details of how and what combination of approaches can be most effectively implemented to manage disease. To fill that gap, the PDC proposed a three step process: (1) a critical assessment of current vector control tools and those under development, (2) outlining a research agenda for determining, in a definitive way, what existing tools work best, and (3) determining how to combine the best vector control options, which have systematically been defined in this process, with DENV vaccines. To address the first step, the PDC convened a meeting of international experts during November 2013 in Washington, DC, to critically assess existing vector control interventions and tools under development. This report summarizes those deliberations.

  20. A Critical Assessment of Vector Control for Dengue Prevention

    PubMed Central

    Achee, Nicole L.; Gould, Fred; Perkins, T. Alex; Reiner, Robert C.; Morrison, Amy C.; Ritchie, Scott A.; Gubler, Duane J.; Teyssou, Remy; Scott, Thomas W.

    2015-01-01

    Recently, the Vaccines to Vaccinate (v2V) initiative was reconfigured into the Partnership for Dengue Control (PDC), a multi-sponsored and independent initiative. This redirection is consistent with the growing consensus among the dengue-prevention community that no single intervention will be sufficient to control dengue disease. The PDC's expectation is that when an effective dengue virus (DENV) vaccine is commercially available, the public health community will continue to rely on vector control because the two strategies complement and enhance one another. Although the concept of integrated intervention for dengue prevention is gaining increasingly broader acceptance, to date, no consensus has been reached regarding the details of how and what combination of approaches can be most effectively implemented to manage disease. To fill that gap, the PDC proposed a three step process: (1) a critical assessment of current vector control tools and those under development, (2) outlining a research agenda for determining, in a definitive way, what existing tools work best, and (3) determining how to combine the best vector control options, which have systematically been defined in this process, with DENV vaccines. To address the first step, the PDC convened a meeting of international experts during November 2013 in Washington, DC, to critically assess existing vector control interventions and tools under development. This report summarizes those deliberations. PMID:25951103

  1. The Innovative Vector Control Consortium: improved control of mosquito-borne diseases.

    PubMed

    Hemingway, Janet; Beaty, Barry J; Rowland, Mark; Scott, Thomas W; Sharp, Brian L

    2006-07-01

    Few new insecticides have been produced for control of disease vectors for public health in developing countries over the past three decades, owing to market constraints, and the available insecticides are often poorly deployed. The Innovative Vector Control Consortium will address these market failures by developing a portfolio of chemical and technological tools that will be directly and immediately accessible to populations in the developing world. The Bill and Melinda Gates Foundation has supported this new initiative to enable industry and academia to change the vector control paradigm for malaria and dengue and to ensure that vector control, alongside drugs, case management and vaccines, can be better used to reduce disease.

  2. Genetics and evolution of triatomines: from phylogeny to vector control

    PubMed Central

    Gourbière, S; Dorn, P; Tripet, F; Dumonteil, E

    2012-01-01

    Triatomines are hemipteran bugs acting as vectors of the protozoan parasite Trypanosoma cruzi. This parasite causes Chagas disease, one of the major parasitic diseases in the Americas. Studies of triatomine genetics and evolution have been particularly useful in the design of rational vector control strategies, and are reviewed here. The phylogeography of several triatomine species is now slowly emerging, and the struggle to reconcile the phenotypic, phylogenetic, ecological and epidemiological species concepts makes for a very dynamic field. Population genetic studies using different markers indicate a wide range of population structures, depending on the triatomine species, ranging from highly fragmented to mobile, interbreeding populations. Triatomines transmit T. cruzi in the context of complex interactions between the insect vectors, their bacterial symbionts and the parasites; however, an integrated view of the significance of these interactions in triatomine biology, evolution and in disease transmission is still lacking. The development of novel genetic markers, together with the ongoing sequencing of the Rhodnius prolixus genome and more integrative studies, will provide key tools to expanding our understanding of these important insect vectors and allow the design of improved vector control strategies. PMID:21897436

  3. Methods for control of tick vectors of Lyme Borreliosis

    USGS Publications Warehouse

    Jaenson, T.G.T.; Fish, D.; Ginsberg, H.S.; Gray, J.S.; Mather, T.N.; Piesman, J.

    1991-01-01

    During the IVth International Conference on Lyme Borreliosis in Stockholm, 1990, a workshop on control of Lyme disease vectors briefly reviewed: basic ecological principles for tick control; biocontrol of ticks; chemical control, including the use of repellents and use of permethrin-treated rodent nest material; tick control by habitat modification; and reduction of tick host availability. It was concluded that, although much research work remains, Lyme borreliosis is to a large extent a preventable infection. Avoidance of heavily tick-infested areas, personal protection using proper clothing, and prompt removal of attached ticks remain the most effective protective measures. Many other prophylactic measures are available and could be efficiently integrated into schemes to reduce the abundance of vectors. However, since the ecology of the infection varies greatly between different localities it may be necessary to apply different combinations of control methods in different endemic regions.

  4. Vector disparity sensor with vergence control for active vision systems.

    PubMed

    Barranco, Francisco; Diaz, Javier; Gibaldi, Agostino; Sabatini, Silvio P; Ros, Eduardo

    2012-01-01

    This paper presents an architecture for computing vector disparity for active vision systems as used on robotics applications. The control of the vergence angle of a binocular system allows us to efficiently explore dynamic environments, but requires a generalization of the disparity computation with respect to a static camera setup, where the disparity is strictly 1-D after the image rectification. The interaction between vision and motor control allows us to develop an active sensor that achieves high accuracy of the disparity computation around the fixation point, and fast reaction time for the vergence control. In this contribution, we address the development of a real-time architecture for vector disparity computation using an FPGA device. We implement the disparity unit and the control module for vergence, version, and tilt to determine the fixation point. In addition, two on-chip different alternatives for the vector disparity engines are discussed based on the luminance (gradient-based) and phase information of the binocular images. The multiscale versions of these engines are able to estimate the vector disparity up to 32 fps on VGA resolution images with very good accuracy as shown using benchmark sequences with known ground-truth. The performances in terms of frame-rate, resource utilization, and accuracy of the presented approaches are discussed. On the basis of these results, our study indicates that the gradient-based approach leads to the best trade-off choice for the integration with the active vision system.

  5. Solid rocket booster thrust vector control subsystem description

    NASA Technical Reports Server (NTRS)

    Redmon, J., Jr. (Compiler)

    1983-01-01

    Major Solid Rocket Booster-Thrust Vector Control (SRB-TVC) subsystem components and subcomponents used in the Space Transportation System (STS) are identified. Simplified schematics, detailed schematics, figures, photographs, and data are included to acquaint the reader with the operation, performance, and physical layout as well as the materials and instrumentation used.

  6. Vectored Thrust Digital Flight Control for Crew Escape. Volume 2.

    DTIC Science & Technology

    1985-12-01

    general the roll euler angle is essentially a " free " control variable since rotations about the velocity vector induce no injurious force and torque...400 +200 -200 - i +200 -200 radicl ion +1 - acceleration radical Figure 7.63 MIL 2 (Table 1) 339 u t=OUstt=S +2000 n *" Q ~ f 2 7- _7- dynornic

  7. Topographic models for predicting malaria vector breeding habitats: potential tools for vector control managers

    PubMed Central

    2013-01-01

    Background Identification of malaria vector breeding sites can enhance control activities. Although associations between malaria vector breeding sites and topography are well recognized, practical models that predict breeding sites from topographic information are lacking. We used topographic variables derived from remotely sensed Digital Elevation Models (DEMs) to model the breeding sites of malaria vectors. We further compared the predictive strength of two different DEMs and evaluated the predictability of various habitat types inhabited by Anopheles larvae. Methods Using GIS techniques, topographic variables were extracted from two DEMs: 1) Shuttle Radar Topography Mission 3 (SRTM3, 90-m resolution) and 2) the Advanced Spaceborne Thermal Emission Reflection Radiometer Global DEM (ASTER, 30-m resolution). We used data on breeding sites from an extensive field survey conducted on an island in western Kenya in 2006. Topographic variables were extracted for 826 breeding sites and for 4520 negative points that were randomly assigned. Logistic regression modelling was applied to characterize topographic features of the malaria vector breeding sites and predict their locations. Model accuracy was evaluated using the area under the receiver operating characteristics curve (AUC). Results All topographic variables derived from both DEMs were significantly correlated with breeding habitats except for the aspect of SRTM. The magnitude and direction of correlation for each variable were similar in the two DEMs. Multivariate models for SRTM and ASTER showed similar levels of fit indicated by Akaike information criterion (3959.3 and 3972.7, respectively), though the former was slightly better than the latter. The accuracy of prediction indicated by AUC was also similar in SRTM (0.758) and ASTER (0.755) in the training site. In the testing site, both SRTM and ASTER models showed higher AUC in the testing sites than in the training site (0.829 and 0.799, respectively). The

  8. Application of Lanczos vectors to control design of flexible structures

    NASA Technical Reports Server (NTRS)

    Craig, Roy R., Jr.; Su, Tzu-Jeng

    1990-01-01

    This report covers research conducted during the first year of the two-year grant. The research, entitled 'Application of Lanczos Vectors to Control Design of Flexible Structures' concerns various ways to obtain reduced-order mathematical models for use in dynamic response analyses and in control design studies. This report summarizes research described in several reports and papers that were written under this contract. Extended abstracts are presented for technical papers covering the following topics: controller reduction by preserving impulse response energy; substructuring decomposition and controller synthesis; model reduction methods for structural control design; and recent literature on structural modeling, identification, and analysis.

  9. Thrust vector control algorithm design for the Cassini spacecraft

    NASA Technical Reports Server (NTRS)

    Enright, Paul J.

    1993-01-01

    This paper describes a preliminary design of the thrust vector control algorithm for the interplanetary spacecraft, Cassini. Topics of discussion include flight software architecture, modeling of sensors, actuators, and vehicle dynamics, and controller design and analysis via classical methods. Special attention is paid to potential interactions with structural flexibilities and propellant dynamics. Controller performance is evaluated in a simulation environment built around a multi-body dynamics model, which contains nonlinear models of the relevant hardware and preliminary versions of supporting attitude determination and control functions.

  10. Thrust vector control algorithm design for the Cassini spacecraft

    NASA Astrophysics Data System (ADS)

    Enright, Paul J.

    1993-02-01

    This paper describes a preliminary design of the thrust vector control algorithm for the interplanetary spacecraft, Cassini. Topics of discussion include flight software architecture, modeling of sensors, actuators, and vehicle dynamics, and controller design and analysis via classical methods. Special attention is paid to potential interactions with structural flexibilities and propellant dynamics. Controller performance is evaluated in a simulation environment built around a multi-body dynamics model, which contains nonlinear models of the relevant hardware and preliminary versions of supporting attitude determination and control functions.

  11. Design of high power electromechanical actuator for thrust vector control

    NASA Technical Reports Server (NTRS)

    Cowan, J. R.; Myers, W. N.

    1991-01-01

    NASA-Marshall has undertaken the development of electromechanical actuators (EMAs) for thrust vector control (TVC) augmentation system implementation. The TVC EMA presented has as its major components two three-phase brushless dc motors, a two-pass gear-reduction system, and a roller screw for rotary-to-linear motion conversion. System control is furnished by a solid-state electronic controller and power supply; a pair of resolvers deliver position feedback to the controller, such that precise positioning is achieved. Peformance comparisons have been conducted between the EMA and comparable-performance hydraulic systems applicable to TVCs.

  12. 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

  13. A review of the control of Simulium vectors of onchocerciasis

    PubMed Central

    McMahon, J. P.

    1967-01-01

    The purpose of this paper is to bring together all the available information concerning the control of Simulium vectors of onchocerciasis in Africa and Central and South America. Some of the larger control schemes are described in detail. Insecticidal formulations, rates of dosage, and methods of application are given when available, and costs per square mile (or square kilometre) are quoted where possible as a guide to future operations. The efficacy of ground application (larviciding) as compared with aerial application (larviciding and adulticiding) is discussed and it is concluded that ground larviciding is likely to achieve the best results, at less cost, in onchocercal foci where the vectors usually breed in small, densely wooded streams. Data in connexion with fly densities, prior and subsequent to control schemes, are quoted when available. PMID:5301384

  14. Viking Orbiter 1975 thrust vector control system accuracy

    NASA Technical Reports Server (NTRS)

    Mcglinchey, L. F.

    1974-01-01

    The thrust vector control (TVC) system of the Viking Orbiter 1975 is discussed. The purpose of the TVC system is to point the engine thrust at the vehicle center of mass and to maintain attitude stability during propulsive maneuvers. This is accomplished by mounting the engine in a two-axis gimbal system. The TVC system then controls the pointing of the engine by closed loop control of two linear actuators which extend or retract and rotate the engine in its gimbal system. The effect of the TVC on the velocity vector pointing error incurred during a propulsive maneuver is analyzed. Models for predicting the magnitude of the error for various propulsive maneuvers are developed.

  15. Controlling Compressor Vane Flow Vectoring Angles at Transonic Speeds

    NASA Astrophysics Data System (ADS)

    Munson, Matthew; Rempfer, Dietmar; Williams, David; Acharya, Mukund

    2003-11-01

    The ability to control flow separation angles from compressor inlet guide vanes with a Coanda-type actuator is demonstrated using both wind tunnel experiments and finite element simulations. Vectoring angles up to 40 degrees from the uncontrolled baseline state were measured with helium schlieren visualization at transonic Mach numbers ranging from 0.1 to 0.6, and with airfoil chord Reynolds numbers ranging from 89,000 to 710,000. The magnitude of the vectoring angle is shown to depend upon the geometry of the trailing edge, and actuator slot size, and the momentum flux coefficient. Under certain conditions the blowing has no effect on the vectoring angle indicating that the Coanda effect is not present. DNS simulations with the finite element method investigated the effects of geometry changes and external flow. Continuous control of the vectoring angle is demonstrated, which has important implications for application to rotating machinery. The technique is shown to reduce the stall flow coefficient by 15 percent in an axial flow compressor.

  16. CFD evaluation of an advanced thrust vector control concept

    NASA Technical Reports Server (NTRS)

    Tiarn, Weihnurng; Cavalleri, Robert

    1990-01-01

    A potential concept that can offer an alternate method for thrust vector control of the Space Shuttle Solid Rocket Booster is the use of a cylindrical probe that is inserted (on demand) through the wall of the rocket nozzle. This Probe Thrust Vector Control (PTVC) concept is an alternate to that of a gimbaled nozzle or a Liquid Injection Thrust Vector (LITVC) system. The viability of the PTVC concept can be assessed either experimentally and/or with the use of CFD. A purely experimental assessment can be time consuming and expensive, whereas a CFD assessment can be very time- and cost-effective. Two key requirements of the proposed concept are PTVC vectoring performance and the active cooling requirements for the probe to maintain its thermal and structural integrity. An active thermal cooling method is the injection of coolant around the pheriphery of the probe. How much coolant is required and how this coolant distributes itself in the flow field is of major concern. The objective of the work reported here is the use of CFD to answer these question and in the design of test hardware to substantiate the results of the CFD predictions.

  17. Velocity vector control system augmented with direct lift control

    NASA Technical Reports Server (NTRS)

    Tisdale, H. F., Sr.; Kelly, W. W. (Inventor)

    1981-01-01

    A pilot-controlled stability control system that employs direct lift control (spoiler control) with elevator control to control the flight path angle of an aircraft is described. A computer on the aircraft generates an elevator control signal and a spoiler control signal, using a pilot-controlled pitch control signal and pitch rate, vertical velocity, roll angle, groundspeed, engine pressure ratio and vertical acceleration signals which are generated on the aircraft. The direct lift control by the aircraft spoilers improves the response of the aircraft flight path angle and provides short term flight path stabilization against environmental disturbances.

  18. Targeting male mosquito swarms to control malaria vector density

    PubMed Central

    Sawadogo, Simon Peguedwinde; Niang, Abdoulaye; Bilgo, Etienne; Millogo, Azize; Maïga, Hamidou; Dabire, Roch K.; Tripet, Frederic; Diabaté, Abdoulaye

    2017-01-01

    Malaria control programs are being jeopardized by the spread of insecticide resistance in mosquito vector populations. It has been estimated that the spread of resistance could lead to an additional 120000 deaths per year, and interfere with the prospects for sustained control or the feasibility of achieving malaria elimination. Another complication for the development of resistance management strategies is that, in addition to insecticide resistance, mosquito behavior evolves in a manner that diminishes the impact of LLINs and IRS. Mosquitoes may circumvent LLIN and IRS control through preferential feeding and resting outside human houses and/or being active earlier in the evening before people go to sleep. Recent developments in our understanding of mosquito swarming suggest that new tools targeting mosquito swarms can be designed to cut down the high reproductive rate of malaria vectors. Targeting swarms of major malaria vectors may provide an effective control method to counteract behavioral resistance developed by mosquitoes. Here, we evaluated the impact of systematic spraying of swarms of Anopheles gambiae s.l. using a mixed carbamate and pyrethroid aerosol. The impact of this intervention on vector density, female insemination rates and the age structure of males was measured. We showed that the resulting mass killing of swarming males and some mate-seeking females resulted in a dramatic 80% decrease in population size compared to a control population. A significant decrease in female insemination rate and a significant shift in the age structure of the male population towards younger males incapable of mating were observed. This paradigm-shift study therefore demonstrates that targeting primarily males rather than females, can have a drastic impact on mosquito population. PMID:28278212

  19. Attitude Control for an Aero-Vehicle Using Vector Thrusting and Variable Speed Control Moment Gyros

    NASA Technical Reports Server (NTRS)

    Shin, Jong-Yeob; Lim, K. B.; Moerder, D. D.

    2005-01-01

    Stabilization of passively unstable thrust-levitated vehicles can require significant control inputs. Although thrust vectoring is a straightforward choice for realizing these inputs, this may lead to difficulties discussed in the paper. This paper examines supplementing thrust vectoring with Variable-Speed Control Moment Gyroscopes (VSCMGs). The paper describes how to allocate VSCMGs and the vectored thrust mechanism for attitude stabilization in frequency domain and also shows trade-off between vectored thrust and VSCMGs. Using an H2 control synthesis methodology in LMI optimization, a feedback control law is designed for a thrust-levitated research vehicle and is simulated with the full nonlinear model. It is demonstrated that VSCMGs can reduce the use of vectored thrust variation for stabilizing the hovering platform in the presence of strong wind gusts.

  20. Trypanosomiasis challenge estimation using the diminazene aceturate (Berenil) index in Zebu in Gabon.

    PubMed

    Cossic, Brieuc G A; Adjahoutonon, Brice; Gloaguen, Pierre; Dibanganga, Gui Lov; Maganga, Gael; Leroy, Pascal; MacLeod, Ewan T; Picozzi, Kim

    2017-03-01

    A longitudinal study was conducted within a cattle ranch in Gabon to determine the diminazene aceturate (Berenil) index (DAI) in a group of Zebu, raised under low tsetse density; this measure providing an assessment of trypanosomiasis risk. The objective was to evaluate the trypanosomiasis pressure thus informing trypanosomiasis control methods and cattle management. Twenty female adult Zebu were monitored for 24 weeks during the dry season. Blood samples were collected on a weekly basis and subjected to parasitological and haematological analysis (n = 480), using the buffy-coat method and the packed cell volume value (PCV), respectively, infected animals were treated with a single intramuscular injection of diminazene aceturate (8 mg/kg). Twenty-nine single infectious events were recorded and a DAI of 1.45 was calculated. Two trypanosome species were identified: Trypanosoma congolense (96.2%) and Trypanosoma vivax (3.8%). The mean PCV value of the infected animals was lower (26.6) compared to non-infected animals (32.0). This study shows that DAI may be a useful tool to assess trypanosomiasis. However, this is a time-consuming method that may be improved by using randomly selected sentinel animals to adapt the chemoprophylactic schemes, hence decreasing the costs and the drug resistance risk.

  1. Fault tolerant vector control of induction motor drive

    NASA Astrophysics Data System (ADS)

    Odnokopylov, G.; Bragin, A.

    2014-10-01

    For electric composed of technical objects hazardous industries, such as nuclear, military, chemical, etc. an urgent task is to increase their resiliency and survivability. The construction principle of vector control system fault-tolerant asynchronous electric. Displaying recovery efficiency three-phase induction motor drive in emergency mode using two-phase vector control system. The process of formation of a simulation model of the asynchronous electric unbalance in emergency mode. When modeling used coordinate transformation, providing emergency operation electric unbalance work. The results of modeling transient phase loss motor stator. During a power failure phase induction motor cannot save circular rotating field in the air gap of the motor and ensure the restoration of its efficiency at rated torque and speed.

  2. Adaptive support vector regression for UAV flight control.

    PubMed

    Shin, Jongho; Jin Kim, H; Kim, Youdan

    2011-01-01

    This paper explores an application of support vector regression for adaptive control of an unmanned aerial vehicle (UAV). Unlike neural networks, support vector regression (SVR) generates global solutions, because SVR basically solves quadratic programming (QP) problems. With this advantage, the input-output feedback-linearized inverse dynamic model and the compensation term for the inversion error are identified off-line, which we call I-SVR (inversion SVR) and C-SVR (compensation SVR), respectively. In order to compensate for the inversion error and the unexpected uncertainty, an online adaptation algorithm for the C-SVR is proposed. Then, the stability of the overall error dynamics is analyzed by the uniformly ultimately bounded property in the nonlinear system theory. In order to validate the effectiveness of the proposed adaptive controller, numerical simulations are performed on the UAV model.

  3. A Research Agenda for Malaria Eradication: Vector Control

    PubMed Central

    2011-01-01

    Different challenges are presented by the variety of malaria transmission environments present in the world today. In each setting, improved control for reduction of morbidity is a necessary first step towards the long-range goal of malaria eradication and a priority for regions where the disease burden is high. For many geographic areas where transmission rates are low to moderate, sustained and well-managed application of currently available tools may be sufficient to achieve local elimination. The research needs for these areas will be to sustain and perhaps improve the effectiveness of currently available tools. For other low-to-moderate transmission regions, notably areas where the vectors exhibit behaviours such as outdoor feeding and resting that are not well targeted by current strategies, new interventions that target predictable features of the biology/ecologies of the local vectors will be required. To achieve elimination in areas where high levels of transmission are sustained by very efficient vector species, radically new interventions that significantly reduce the vectorial capacity of wild populations will be needed. Ideally, such interventions should be implemented with a one-time application with a long-lasting impact, such as genetic modification of the vectorial capacity of the wild vector population. PMID:21311587

  4. Towards the Atlas of human African trypanosomiasis

    PubMed Central

    Cecchi, Giuliano; Paone, Massimo; Franco, José R; Fèvre, Eric M; Diarra, Abdoulaye; Ruiz, José A; Mattioli, Raffaele C; Simarro, Pere P

    2009-01-01

    Background Updated, accurate and comprehensive information on the distribution of human African trypanosomiasis (HAT), also known as sleeping sickness, is critically important to plan and monitor control activities. We describe input data, methodology, preliminary results and future prospects of the HAT Atlas initiative, which will allow major improvements in the understanding of the spatial distribution of the disease. Methods Up-to-date as well as historical data collected by national sleeping sickness control programmes, non-governmental organizations and research institutes have been collated over many years by the HAT Control and Surveillance Programme of the World Health Organization. This body of information, unpublished for the most part, is now being screened, harmonized, and analysed by means of database management systems and geographical information systems (GIS). The number of new HAT cases and the number of people screened within a defined geographical entity were chosen as the key variables to map disease distribution in sub-Saharan Africa. Results At the time of writing, over 600 epidemiological reports and files from seventeen countries were collated and included in the data repository. The reports contain information on approximately 20,000 HAT cases, associated to over 7,000 different geographical entities. The oldest epidemiological records considered so far date back to 1985, the most recent having been gathered in 2008. Data from Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea and Gabon from the year 2000 onwards were fully processed and the preliminary regional map of HAT distribution is presented. Conclusion The use of GIS tools and geo-referenced, village-level epidemiological data allow the production of maps that substantially improve on the spatial quality of previous cartographic products of similar scope. The significant differences between our preliminary outputs and earlier maps of HAT transmission areas

  5. Design and test of electromechanical actuators for thrust vector control

    NASA Technical Reports Server (NTRS)

    Cowan, J. R.; Weir, Rae Ann

    1993-01-01

    New control mechanisms technologies are currently being explored to provide alternatives to hydraulic thrust vector control (TVC) actuation systems. For many years engineers have been encouraging the investigation of electromechanical actuators (EMA) to take the place of hydraulics for spacecraft control/gimballing systems. The rationale is to deliver a lighter, cleaner, safer, more easily maintained, as well as energy efficient space vehicle. In light of this continued concern to improve the TVC system, the Propulsion Laboratory at the NASA George C. Marshall Space Flight Center (MSFC) is involved in a program to develop electromechanical actuators for the purpose of testing and TVC system implementation. Through this effort, an electromechanical thrust vector control actuator has been designed and assembled. The design consists of the following major components: Two three-phase brushless dc motors, a two pass gear reduction system, and a roller screw, which converts rotational input into linear output. System control is provided by a solid-state electronic controller and power supply. A pair of resolvers and associated electronics deliver position feedback to the controller such that precise positioning is achieved. Testing and evaluation is currently in progress. Goals focus on performance comparisons between EMA's and similar hydraulic systems.

  6. Spray Characterization of Thermal Fogging Equipment Typically Used in Vector Control

    DTIC Science & Technology

    2008-12-01

    KEY WORDS Atomization, droplet size, sprayer, thermal fogger, vector control INTRODUCTION One of the most common methods for control- ling...ment and insecticides, applicators depend on recommended equipment operating parameters , as supplied by the manufacturer, along with recommended...2001). In vector control, Seleena et al. (2001) studied thermal application of Bacillus thwingiensis var. israelensis for dengue vector control using

  7. Biological Control Strategies for Mosquito Vectors of Arboviruses

    PubMed Central

    Huang, Yan-Jang S.; Higgs, Stephen; Vanlandingham, Dana L.

    2017-01-01

    Historically, biological control utilizes predatory species and pathogenic microorganisms to reduce the population of mosquitoes as disease vectors. This is particularly important for the control of mosquito-borne arboviruses, which normally do not have specific antiviral therapies available. Although development of resistance is likely, the advantages of biological control are that the resources used are typically biodegradable and ecologically friendly. Over the past decade, the advancement of molecular biology has enabled optimization by the manipulation of genetic materials associated with biological control agents. Two significant advancements are the discovery of cytoplasmic incompatibility induced by Wolbachia bacteria, which has enhanced replacement programs, and the introduction of dominant lethal genes into local mosquito populations through the release of genetically modified mosquitoes. As various arboviruses continue to be significant public health threats, biological control strategies have evolved to be more diverse and become critical tools to reduce the disease burden of arboviruses. PMID:28208639

  8. Vector control structure of an asynchronous motor at maximum torque

    NASA Astrophysics Data System (ADS)

    Chioncel, C. P.; Tirian, G. O.; Gillich, N.; Raduca, E.

    2016-02-01

    Vector control methods offer the possibility to gain high performance, being widely used. Certain applications require an optimum control in limit operating conditions, as, at maximum torque, that is not always satisfied. The paper presents how the voltage and the frequency for an asynchronous machine (ASM) operating at variable speed are determinate, with an accent on the method that keeps the rotor flux constant. The simulation analyses consider three load types: variable torque and speed, variable torque and constant speed, constant torque and variable speed. The final values of frequency and voltage are obtained through the proposed control schemes with one controller using the simulation language based on the Maple module. The dynamic analysis of the system is done for the case with P and PI controller and allows conclusions on the proposed method, which can have different applications, as the ASM in wind turbines.

  9. Energy-saving technology of vector controlled induction motor based on the adaptive neuro-controller

    NASA Astrophysics Data System (ADS)

    Engel, E.; Kovalev, I. V.; Karandeev, D.

    2015-10-01

    The ongoing evolution of the power system towards a Smart Grid implies an important role of intelligent technologies, but poses strict requirements on their control schemes to preserve stability and controllability. This paper presents the adaptive neuro-controller for the vector control of induction motor within Smart Gird. The validity and effectiveness of the proposed energy-saving technology of vector controlled induction motor based on adaptive neuro-controller are verified by simulation results at different operating conditions over a wide speed range of induction motor.

  10. Paratransgenesis: a promising new strategy for mosquito vector control.

    PubMed

    Wilke, André Barretto Bruno; Marrelli, Mauro Toledo

    2015-06-24

    The three main mosquito genera, Anopheles, Aedes and Culex, transmit respectively malaria, dengue and lymphatic filariasis. Current mosquito control strategies have proved unsuccessful, and there still is a substantial number of morbidity and mortality from these diseases. Genetic control methods have now arisen as promising alternative strategies, based on two approaches: the replacement of a vector population by disease-refractory mosquitoes and the release of mosquitoes carrying a lethal gene to suppress target populations. However, substantial hurdles and limitations need to be overcome if these methods are to be used successfully, the most significant being that a transgenic mosquito strain is required for every target species, making genetically modified mosquito strategies inviable when there are multiple vector mosquitoes in the same area. Genetically modified bacteria capable of colonizing a wide range of mosquito species may be a solution to this problem and another option for the control of these diseases. In the paratransgenic approach, symbiotic bacteria are genetically modified and reintroduced in mosquitoes, where they express effector molecules. For this approach to be used in practice, however, requires a better understanding of mosquito microbiota and that symbiotic bacteria and effector molecules be identified. Paratransgenesis could prove very useful in mosquito species that are inherently difficult to transform or in sibling species complexes. In this approach, a genetic modified bacteria can act by: (a) causing pathogenic effects in the host; (b) interfering with the host's reproduction; (c) reducing the vector's competence; and (d) interfering with oogenesis and embryogenesis. It is a much more flexible and adaptable approach than the use of genetically modified mosquitoes because effector molecules and symbiotic bacteria can be replaced if they do not achieve the desired result. Paratransgenesis may therefore become an important integrated

  11. Interruption of vector transmission by native vectors and “the art of the possible”

    PubMed Central

    Salvatella, Roberto; Irabedra, Pilar; Castellanos, Luis G

    2013-01-01

    In a recent article in the Reader’s Opinion, advantages and disadvantages of the certification processes of interrupted Chagas disease transmission (American trypanosomiasis) by native vector were discussed. Such concept, accepted by those authors for the case of endemic situations with introduced vectors, has been built on a long and laborious process by endemic countries and Subregional Initiatives for Prevention, Control and Treatment of Chagas, with Technical Secretariat of the Pan American Health Organization/World Health Organization, to create a horizon target and goal to concentrate priorities and resource allocation and actions. With varying degrees of sucess, which are not replaceable for a certificate of good practice, has allowed during 23 years to safeguard the effective control of transmission of Trypanosoma cruzi not to hundreds of thousands, but millions of people at risk conditions, truly “the art of the possible.” PMID:24626310

  12. Optimal control strategy of malaria vector using genetically modified mosquitoes.

    PubMed

    Rafikov, M; Bevilacqua, L; Wyse, A P P

    2009-06-07

    The development of transgenic mosquitoes that are resistant to diseases may provide a new and effective weapon of diseases control. Such an approach relies on transgenic mosquitoes being able to survive and compete with wild-type populations. These transgenic mosquitoes carry a specific code that inhibits the plasmodium evolution in its organism. It is said that this characteristic is hereditary and consequently the disease fades away after some time. Once transgenic mosquitoes are released, interactions between the two populations and inter-specific mating between the two types of mosquitoes take place. We present a mathematical model that considers the generation overlapping and variable environment factors. Based on this continuous model, the malaria vector control is formulated and solved as an optimal control problem, indicating how genetically modified mosquitoes should be introduced in the environment. Numerical simulations show the effectiveness of the proposed control.

  13. Resistance of vectors of disease to pesticides. Fifth report of the WHO Expert Committee in Vector Biology and Control.

    PubMed

    1980-01-01

    The resistance of vectors (the term includes primary and intermediate vertebrate and invertebrate hosts and animal reservoirs of human and animal diseases) of disease to pesticides is a major problem faced by WHO member states in the control of vectorborne diseases. Since the meeting of the WHO Expert Committee on Insecticides in 1975, resistance has continued to increase and to affect disease control programs in many countries. The appearance of multiresistance in several important vectors has been the most significant development since the 1975 meeting. The sandfly Phlebotomus papatasi in Bihar, India has been found to be resistant to DDT, leaving the tsetse fly the only important vector species in which resistance has not been reported. This book discusses 1) pesticide resistance in arthropod vectors, malaria vectors, vectors of other diseases and disease reservoirs (rodents); 2) present status of research on resistance of vectors to pesticides, including the biochemistry and genetics of resistance; 3) measures to counteract resistance; 4) detection and monitoring of vector resistance to pesticides; 5) disseminatin of information and training; and 6) recommendations for future research and courses of action.

  14. A literature review of economic evaluations for a neglected tropical disease: human African trypanosomiasis ("sleeping sickness").

    PubMed

    Sutherland, C Simone; Yukich, Joshua; Goeree, Ron; Tediosi, Fabrizio

    2015-02-01

    Human African trypanosomiasis (HAT) is a disease caused by infection with the parasite Trypanosoma brucei gambiense or T. b. rhodesiense. It is transmitted to humans via the tsetse fly. Approximately 70 million people worldwide were at risk of infection in 1995, and approximately 20,000 people across Africa are infected with HAT. The objective of this review was to identify existing economic evaluations in order to summarise cost-effective interventions to reduce, control, or eliminate the burden of HAT. The studies included in the review were compared and critically appraised in order to determine if there were existing standardised methods that could be used for economic evaluation of HAT interventions or if innovative methodological approaches are warranted. A search strategy was developed using keywords and was implemented in January 2014 in several databases. The search returned a total of 2,283 articles. After two levels of screening, a total of seven economic evaluations were included and underwent critical appraisal using the Scottish Intercollegiate Guidelines Network (SIGN) Methodology Checklist 6: Economic Evaluations. Results from the existing studies focused on the cost-effectiveness of interventions for the control and reduction of disease transmission. Modelling was a common method to forecast long-term results, and publications focused on interventions by category, such as case detection, diagnostics, drug treatments, and vector control. Most interventions were considered cost-effective based on the thresholds described; however, the current treatment, nifurtomix-eflornithine combination therapy (NECT), has not been evaluated for cost-effectiveness, and considerations for cost-effective strategies for elimination have yet to be completed. Overall, the current evidence highlights the main components that play a role in control; however, economic evaluations of HAT elimination strategies are needed to assist national decision makers, stakeholders, and

  15. Human African trypanosomiasis, chemotherapy and CNS disease.

    PubMed

    Rodgers, Jean

    2009-06-25

    Trypanosomes have been recognised as human pathogens for over a century. Human African trypanosomiasis is endemic in an area sustaining 60 million people and is fatal without chemotherapeutic intervention. Available trypanocidal drugs require parenteral administration and are associated with adverse reactions including the development of a severe post-treatment reactive encephalopathy (PTRE). Following infection the parasites proliferate in the systemic compartment before invading the CNS where a cascade of events results in neuroinflammation. This review summarises the clinical manifestations of the infection and chemotherapeutic regimens as well as the current research findings and hypotheses regarding the neuropathogenesis of the disease.

  16. Cost of Dengue Vector Control Activities in Malaysia.

    PubMed

    Packierisamy, P Raviwharmman; Ng, Chiu-Wan; Dahlui, Maznah; Inbaraj, Jonathan; Balan, Venugopalan K; Halasa, Yara A; Shepard, Donald S

    2015-11-01

    Dengue fever, an arbovirus disease transmitted by Aedes mosquitoes, has recently spread rapidly, especially in the tropical countries of the Americas and Asia-Pacific regions. It is endemic in Malaysia, with an annual average of 37,937 reported dengue cases from 2007 to 2012. This study measured the overall economic impact of dengue in Malaysia, and estimated the costs of dengue prevention. In 2010, Malaysia spent US$73.5 million or 0.03% of the country's GDP on its National Dengue Vector Control Program. This spending represented US$1,591 per reported dengue case and US$2.68 per capita population. Most (92.2%) of this spending occurred in districts, primarily for fogging. A previous paper estimated the annual cost of dengue illness in the country at US$102.2 million. Thus, the inclusion of preventive activities increases the substantial estimated cost of dengue to US$175.7 million, or 72% above illness costs alone. If innovative technologies for dengue vector control prove efficacious, and a dengue vaccine was introduced, substantial existing spending could be rechanneled to fund them.

  17. Cost of Dengue Vector Control Activities in Malaysia

    PubMed Central

    Packierisamy, P. Raviwharmman; Ng, Chiu-Wan; Dahlui, Maznah; Inbaraj, Jonathan; Balan, Venugopalan K.; Halasa, Yara A.; Shepard, Donald S.

    2015-01-01

    Dengue fever, an arbovirus disease transmitted by Aedes mosquitoes, has recently spread rapidly, especially in the tropical countries of the Americas and Asia-Pacific regions. It is endemic in Malaysia, with an annual average of 37,937 reported dengue cases from 2007 to 2012. This study measured the overall economic impact of dengue in Malaysia, and estimated the costs of dengue prevention. In 2010, Malaysia spent US$73.5 million or 0.03% of the country's GDP on its National Dengue Vector Control Program. This spending represented US$1,591 per reported dengue case and US$2.68 per capita population. Most (92.2%) of this spending occurred in districts, primarily for fogging. A previous paper estimated the annual cost of dengue illness in the country at US$102.2 million. Thus, the inclusion of preventive activities increases the substantial estimated cost of dengue to US$175.7 million, or 72% above illness costs alone. If innovative technologies for dengue vector control prove efficacious, and a dengue vaccine was introduced, substantial existing spending could be rechanneled to fund them. PMID:26416116

  18. 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.

  19. Seroprevalence survey of American trypanosomiasis in Central Valley of Toluca.

    PubMed

    Quijano-Hernández, Israel A; Castro-Barcena, Alejandro; Barbabosa-Pliego, Alberto; Ochoa-García, Laucel; Del Ángel-Caraza, Javier; Vázquez-Chagoyán, Juan C

    2012-01-01

    American trypanosomiasis is a growing health issue in the Americas. México is an endemic country, where some locations such as in the State of México are considered highly prevalent. In the valley of Toluca city, the capital of the State of Mexico, there exists an apparent high prevalence in dogs. The absence of triatomine vectors suggests that dogs may not be infected. Therefore, we conducted a directed survey to domiciliated and nondomiciliated dogs to reassess dogs' T. cruzi seroprevalence status. HAI and ELISA serologic tests were applied to 124 and 167 serums of domiciliated and nondomiciliated dogs in the target city. Risk factors were estimated, but the results did not show any evidence to assess them. No domiciliated dogs tested positive to both tests, whereas only one non-domiciliated dog resulted positive. This animal may have acquired the infection in an endemic area and then migrated to Toluca. Research results indicate that T. cruzi infection is not actively transmitted among dogs, and it is pointed out that dogs are the main sentinel animal population to evaluate a possible expansion of the territory affected by Chagas' disease.

  20. Study of African Trypanosomiasis and Leishmaniasis. Volume 1. Summary.

    DTIC Science & Technology

    1983-12-01

    AD-A139 365 STUDS OF AFRICAN TRYPANOSOMIASIS AND LEISHMANIASIS(U) f/f ARMY MEDICAL RESEARCH UNITKENYA Apo NEW YORK 09675 M J REARDON ET AL DEC 83...STUDY OF AFRICAN TRYPANOSOMIASIS AND LEISHMANIASIS FINAL REPORT CID LTC M.J. Reardon, VC I.E. Muriithi LTC J.D. Chulay, MC LTC L.D. Hendricks, MSC ym 4...CATALOG NUMBER 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED STUDY OF AFRICAN TRYPANOSOMIASIS AND FINAL--October 1982- LEISHMAIASIS 14

  1. Will integrated surveillance systems for vectors and vector-borne diseases be the future of controlling vector-borne diseases? A practical example from China.

    PubMed

    Wu, Y; Ling, F; Hou, J; Guo, S; Wang, J; Gong, Z

    2016-07-01

    Vector-borne diseases are one of the world's major public health threats and annually responsible for 30-50% of deaths reported to the national notifiable disease system in China. To control vector-borne diseases, a unified, effective and economic surveillance system is urgently needed; all of the current surveillance systems in China waste resources and/or information. Here, we review some current surveillance systems and present a concept for an integrated surveillance system combining existing vector and vector-borne disease monitoring systems. The integrated surveillance system has been tested in pilot programmes in China and led to a 21·6% cost saving in rodent-borne disease surveillance. We share some experiences gained from these programmes.

  2. Trapping volume control in optical tweezers using cylindrical vector beams.

    PubMed

    Skelton, S E; Sergides, M; Saija, R; Iatì, M A; Maragó, O M; Jones, P H

    2013-01-01

    We present the result of an investigation into the optical trapping of spherical microparticles using laser beams with a spatially inhomogeneous polarization direction [cylindrical vector beams (CVBs)]. We perform three-dimensional tracking of the Brownian fluctuations in the position of a trapped particle and extract the trap spring constants. We characterize the trap geometry by the aspect ratio of spring constants in the directions transverse and parallel to the beam propagation direction and evaluate this figure of merit as a function of polarization angle. We show that the additional degree of freedom present in CVBs allows us to control the optical trap strength and geometry by adjusting only the polarization of the trapping beam. Experimental results are compared with a theoretical model of optical trapping using CVBs derived from electromagnetic scattering theory in the T-matrix framework.

  3. Development of novel types of plastid transformation vectors and evaluation of factors controlling expression.

    PubMed

    Herz, Stefan; Füssl, Monika; Steiger, Sandra; Koop, Hans-Ulrich

    2005-12-01

    Two new vector types for plastid transformation were developed and uidA reporter gene expression was compared to standard transformation vectors. The first vector type does not contain any plastid promoter, instead it relies on extension of existing plastid operons and was therefore named "operon-extension" vector. When a strongly expressed plastid operon like psbA was extended by the reporter gene with this vector type, the expression level was superior to that of a standard vector under control of the 16S rRNA promoter. Different insertion sites, promoters and 5'-UTRs were analysed for their effect on reporter gene expression with standard and operon-extension vectors. The 5'-UTR of phage 7 gene 10 in combination with a modified N-terminus was found to yield the highest expression levels. Expression levels were also strongly dependent on external factors like plant or leaf age or light intensity. In the second vector type, named "split" plastid transformation vector, modules of the expression cassette were distributed on two separate vectors. Upon co-transformation of plastids with these vectors, the complete expression cassette became inserted into the plastome. This result can be explained by successive co-integration of the split vectors and final loop-out recombination of the duplicated sequences. The split vector concept was validated with different vector pairs.

  4. American Trypanosomiasis (Also Known as Chagas Disease) Diagnosis

    MedlinePlus

    ... by testing with at least two different serologic tests. Related Links For more information about laboratory diagnosis of Chagas disease, see the DPDx Web site: Chagas disease (American Trypanosomiasis) Diagnostic Procedures: Blood ...

  5. The Burden of Human African Trypanosomiasis

    PubMed Central

    Fèvre, Eric M.; Wissmann, Beatrix v.; Welburn, Susan C.; Lutumba, Pascal

    2008-01-01

    Human African trypanosomiasis (HAT, or sleeping sickness) is a protozoan parasitic infection caused by Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense. These are neglected tropical diseases, and T.b. rhodesiense HAT is a zoonosis. We review current knowledge on the burden of HAT in sub-Saharan Africa, with an emphasis on the disability-adjusted life year (DALY), data sources, and methodological issues relating to the use of this metric for assessing the burden of this disease. We highlight areas where data are lacking to properly quantify the impact of these diseases, mainly relating to quantifying under-reporting and disability associated with infection, and challenge the HAT research community to tackle the neglect in data gathering to enable better evidence-based assessments of burden using DALYs or other appropriate measures. PMID:19104653

  6. Emergence and Prevalence of Human Vector-Borne Diseases in Sink Vector Populations

    PubMed Central

    Rascalou, Guilhem; Pontier, Dominique; Menu, Frédéric; Gourbière, Sébastien

    2012-01-01

    Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining ‘source’ populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining ‘sink’ vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15–55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale. PMID:22629337

  7. Emergence and prevalence of human vector-borne diseases in sink vector populations.

    PubMed

    Rascalou, Guilhem; Pontier, Dominique; Menu, Frédéric; Gourbière, Sébastien

    2012-01-01

    Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining 'source' populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining 'sink' vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15-55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale.

  8. Integrated pest management and allocation of control efforts for vector-borne diseases

    USGS Publications Warehouse

    Ginsberg, H.S.

    2001-01-01

    Applications of various control methods were evaluated to determine how to integrate methods so as to minimize the number of human cases of vector-borne diseases. These diseases can be controlled by lowering the number of vector-human contacts (e.g., by pesticide applications or use of repellents), or by lowering the proportion of vectors infected with pathogens (e.g., by lowering or vaccinating reservoir host populations). Control methods should be combined in such a way as to most efficiently lower the probability of human encounter with an infected vector. Simulations using a simple probabilistic model of pathogen transmission suggest that the most efficient way to integrate different control methods is to combine methods that have the same effect (e.g., combine treatments that lower the vector population; or combine treatments that lower pathogen prevalence in vectors). Combining techniques that have different effects (e.g., a technique that lowers vector populations with a technique that lowers pathogen prevalence in vectors) will be less efficient than combining two techniques that both lower vector populations or combining two techniques that both lower pathogen prevalence, costs being the same. Costs of alternative control methods generally differ, so the efficiency of various combinations at lowering human contact with infected vectors should be estimated at available funding levels. Data should be collected from initial trials to improve the effects of subsequent interventions on the number of human cases.

  9. ProactiveVector control strategies and improved monitoring and evaluation practices for dengue prevention.

    PubMed

    Eisen, Lars; Beaty, Barry J; Morrison, Amy C; Scott, Thomas W

    2009-11-01

    Despite tremendous efforts by public health organizations in dengue-endemic countries, it has proven difficult to achieve effective and sustainable control of the primary dengue virus vector Aedes aegypti (L.) and to effectively disrupt dengue outbreaks. This problem has multiple root causes, including uncontrolled urbanization, increased global spread of dengue viruses, and vector and dengue control programs not being provided adequate resources. In this forum article, we give an overview of the basic elements of a vector and dengue control program and describe a continuous improvement cyclical model to systematically and incrementally improve control program performance by regular efforts to identify ineffective methods and inferior technology, and then replacing them with better performing alternatives. The first step includes assessments of the overall resource allocation among vector/dengue control program activities, the efficacy of currently used vector control methods, and the appropriateness of technology used to support the program. We expect this will reveal that 1) some currently used vector control methods are not effective, 2) resource allocations often are skewed toward reactive vector control measures, and 3) proactive approaches commonly are underfunded and therefore poorly executed. Next steps are to conceptualize desired changes to vector control methods or technologies used and then to operationally determine in pilot studies whether these changes are likely to improve control program performance. This should be followed by a shift in resource allocation to replace ineffective methods and inferior technology with more effective and operationally tested alternatives. The cyclical and self-improving nature of the continuous improvement model will produce locally appropriate management strategies that continually are adapted to counter changes in vector population or dengue virus transmission dynamics. We discuss promising proactive vector control

  10. Man-fly contact in the Gambian trypanosomiasis focus of Nola-Bilolo (Central African Republic).

    PubMed

    Gouteux, J P; Kounda Gboumbi, J C; Noutoua, L; D'Amico, F; Bailly, C; Roungou, J B

    1993-09-01

    A study using bipyramid tetse fly traps in the Nola-Bilolo sleeping sickness focus (Central African Republic) reveals ecological and behavioural differences between two vectors, Glossina palpalis palpalis and G. fuscipes fuscipes. The latter species inhabits mainly open water sites and surrounding forest, whereas G. p. palpalis occurs mainly in coffe plantations near villages. Consequently, the man-fly contact differs considerably according to the species. The intensity of trypanosomiasis transmission, estimated by the probable distribution of cases, showed significant positive correlation with the density of the flies. Analysis of the fly blood meals in two villages show that, unlike G. g. palpalis, G. f. fuscipes feeds on men more than on pigs. Trypanosoma vivax infection was observed only in G. fuscipes fuscipes. The differences in occupation of the environment between the two vectors must be taken in account in trapping programmes which may modify this distribution.

  11. Modeling and vector control of planar magnetic levitator

    SciTech Connect

    Kim, W.; Trumper, D.L.; Lang, J.H.

    1998-11-01

    The authors designed and implemented a magnetically levitated stage with large planar motion capability. This planar magnetic levitator employs four novel permanent-magnet linear motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for drive. These linear levitation motors can be used as building blocks in the general class of multi-degree-of-freedom motion stages. In this paper, the authors discuss electromechanical modeling and real-time vector control of such a permanent-magnet levitator. They describe the dynamics in a dq frame introduced to decouple the forces acting on the magnetically levitated moving part, namely, the platen. A transformation similar to the Blondel-Park transformation is derived for commutation of the stator phase currents. The authors provide test results on step responses of the magnetically levitated stage. It shows 5-nm rms positioning noise in x and y, which demonstrates the applicability of such stages in the next-generation photolithography in semiconductor manufacturing.

  12. Disruptive technology for vector control: the Innovative Vector Control Consortium and the US Military join forces to explore transformative insecticide application technology for mosquito control programmes.

    PubMed

    Knapp, Jennifer; Macdonald, Michael; Malone, David; Hamon, Nicholas; Richardson, Jason H

    2015-09-26

    Malaria vector control technology has remained largely static for decades and there is a pressing need for innovative control tools and methodology to radically improve the quality and efficiency of current vector control practices. This report summarizes a workshop jointly organized by the Innovative Vector Control Consortium (IVCC) and the Armed Forces Pest Management Board (AFPMB) focused on public health pesticide application technology. Three main topics were discussed: the limitations with current tools and techniques used for indoor residual spraying (IRS), technology innovation to improve efficacy of IRS programmes, and truly disruptive application technology beyond IRS. The group identified several opportunities to improve application technology to include: insuring all IRS programmes are using constant flow valves and erosion resistant tips; introducing compression sprayer improvements that help minimize pesticide waste and human error; and moving beyond IRS by embracing the potential for new larval source management techniques and next generation technology such as unmanned "smart" spray systems. The meeting served to lay the foundation for broader collaboration between the IVCC and AFPMB and partners in industry, the World Health Organization, the Bill and Melinda Gates Foundation and others.

  13. Visceral Leishmaniasis on the Indian Subcontinent: Modelling the Dynamic Relationship between Vector Control Schemes and Vector Life Cycles

    PubMed Central

    2016-01-01

    Background Visceral leishmaniasis (VL) is a disease caused by two known vector-borne parasite species (Leishmania donovani, L. infantum), transmitted to man by phlebotomine sand flies (species: Phlebotomus and Lutzomyia), resulting in ≈50,000 human fatalities annually, ≈67% occurring on the Indian subcontinent. Indoor residual spraying is the current method of sand fly control in India, but alternative means of vector control, such as the treatment of livestock with systemic insecticide-based drugs, are being evaluated. We describe an individual-based, stochastic, life-stage-structured model that represents a sand fly vector population within a village in India and simulates the effects of vector control via fipronil-based drugs orally administered to cattle, which target both blood-feeding adults and larvae that feed on host feces. Principle findings Simulation results indicated efficacy of fipronil-based control schemes in reducing sand fly abundance depended on timing of drug applications relative to seasonality of the sand fly life cycle. Taking into account cost-effectiveness and logistical feasibility, two of the most efficacious treatment schemes reduced population peaks occurring from April through August by ≈90% (applications 3 times per year at 2-month intervals initiated in March) and >95% (applications 6 times per year at 2-month intervals initiated in January) relative to no control, with the cumulative number of sand fly days occurring April-August reduced by ≈83% and ≈97%, respectively, and more specifically during the summer months of peak human exposure (June-August) by ≈85% and ≈97%, respectively. Conclusions Our model should prove useful in a priori evaluation of the efficacy of fipronil-based drugs in controlling leishmaniasis on the Indian subcontinent and beyond. PMID:27537774

  14. Discovery of Infection Associated Metabolic Markers in Human African Trypanosomiasis

    PubMed Central

    Lamour, Sabrina D.; Gomez-Romero, Maria; Vorkas, Panagiotis A.; Alibu, Vincent P.; Saric, Jasmina; Holmes, Elaine; Sternberg, Jeremy M.

    2015-01-01

    Human African trypanosomiasis (HAT) remains a major neglected tropical disease in Sub-Saharan Africa. As clinical symptoms are usually non-specific, new diagnostic and prognostic markers are urgently needed to enhance the number of identified cases and optimise treatment. This is particularly important for disease caused by Trypanosoma brucei rhodesiense, where indirect immunodiagnostic approaches have to date been unsuccessful. We have conducted global metabolic profiling of plasma from T.b.rhodesiense HAT patients and endemic controls, using 1H nuclear magnetic resonance (NMR) spectroscopy and ultra-performance liquid chromatography, coupled with mass spectrometry (UPLC-MS) and identified differences in the lipid, amino acid and metabolite profiles. Altogether 16 significantly disease discriminatory metabolite markers were found using NMR, and a further 37 lipid markers via UPLC-MS. These included significantly higher levels of phenylalanine, formate, creatinine, N-acetylated glycoprotein and triglycerides in patients relative to controls. HAT patients also displayed lower concentrations of histidine, sphingomyelins, lysophosphatidylcholines, and several polyunsaturated phosphatidylcholines. While the disease metabolite profile was partially consistent with previous data published in experimental rodent infection, we also found unique lipid and amino acid profile markers highlighting subtle but important differences between the host response to trypanosome infections between animal models and natural human infections. Our results demonstrate the potential of metabolic profiling in the identification of novel diagnostic biomarkers and the elucidation of pathogenetic mechanisms in this disease. PMID:26505639

  15. Discovery of Infection Associated Metabolic Markers in Human African Trypanosomiasis.

    PubMed

    Lamour, Sabrina D; Gomez-Romero, Maria; Vorkas, Panagiotis A; Alibu, Vincent P; Saric, Jasmina; Holmes, Elaine; Sternberg, Jeremy M

    2015-01-01

    Human African trypanosomiasis (HAT) remains a major neglected tropical disease in Sub-Saharan Africa. As clinical symptoms are usually non-specific, new diagnostic and prognostic markers are urgently needed to enhance the number of identified cases and optimise treatment. This is particularly important for disease caused by Trypanosoma brucei rhodesiense, where indirect immunodiagnostic approaches have to date been unsuccessful. We have conducted global metabolic profiling of plasma from T.b.rhodesiense HAT patients and endemic controls, using 1H nuclear magnetic resonance (NMR) spectroscopy and ultra-performance liquid chromatography, coupled with mass spectrometry (UPLC-MS) and identified differences in the lipid, amino acid and metabolite profiles. Altogether 16 significantly disease discriminatory metabolite markers were found using NMR, and a further 37 lipid markers via UPLC-MS. These included significantly higher levels of phenylalanine, formate, creatinine, N-acetylated glycoprotein and triglycerides in patients relative to controls. HAT patients also displayed lower concentrations of histidine, sphingomyelins, lysophosphatidylcholines, and several polyunsaturated phosphatidylcholines. While the disease metabolite profile was partially consistent with previous data published in experimental rodent infection, we also found unique lipid and amino acid profile markers highlighting subtle but important differences between the host response to trypanosome infections between animal models and natural human infections. Our results demonstrate the potential of metabolic profiling in the identification of novel diagnostic biomarkers and the elucidation of pathogenetic mechanisms in this disease.

  16. Linear matrix inequalities for analysis and control of linear vector second-order systems

    SciTech Connect

    Adegas, Fabiano D.; Stoustrup, Jakob

    2014-10-06

    Many dynamical systems are modeled as vector second-order differential equations. This paper presents analysis and synthesis conditions in terms of LMI with explicit dependence in the coefficient matrices of vector second-order systems. These conditions benefit from the separation between the Lyapunov matrix and the system matrices by introducing matrix multipliers, which potentially reduce conservativeness in hard control problems. Multipliers facilitate the usage of parameter-dependent Lyapunov functions as certificates of stability of uncertain and time-varying vector second-order systems. The conditions introduced in this work have the potential to increase the practice of analyzing and controlling systems directly in vector second-order form.

  17. Vector control programs in Saint Johns County, Florida and Guayas, Ecuador: successes and barriers to integrated vector management

    PubMed Central

    2014-01-01

    Background Vector-borne diseases (VBDs) and mosquito control programs (MCPs) diverge in settings and countries, and lead control specialists need to be aware of the most effective control strategies. Integrated Vector Management (IVM) strategies, once implemented in MCPs, aim to reduce cost and optimize protection of the populations against VBDs. This study presents a strengths, weaknesses, opportunities, and threats (SWOT) analysis to compare IVM strategies used by MCPs in Saint Johns County, Florida and Guayas, Ecuador. This research evaluates MCPs strategies to improve vector control activities. Methods Methods included descriptive findings of the MCP operations. Information was obtained from vector control specialists, directors, and residents through field trips, surveys, and questionnaires. Evaluations of the strategies and assets of the control programs where obtained through SWOT analysis and within an IVM approach. Results Organizationally, the Floridian MCP is a tax-based District able to make decisions independently from county government officials, with the oversight of an elected board of commissioners. The Guayas program is directed by the country government and assessed by non-governmental organizations like the World health Organization. Operationally, the Floridian MCP conducts entomological surveillance and the Ecuadorian MCP focuses on epidemiological monitoring of human disease cases. Strengths of both MCPs were their community participation and educational programs. Weaknesses for both MCPs included limitations in budgets and technical capabilities. Opportunities, for both MCPs, are additional funding and partnerships with private, non-governmental, and governmental organizations. Threats experienced by both MCPs included political constraints and changes in the social and ecological environment that affect mosquito densities and control efforts. IVM pillars for policy making were used to compare the information among the programs. Differences

  18. High-speed current dq PI controller for vector controlled PMSM drive.

    PubMed

    Marufuzzaman, Mohammad; Reaz, Mamun Bin Ibne; Rahman, Labonnah Farzana; Chang, Tae Gyu

    2014-01-01

    High-speed current controller for vector controlled permanent magnet synchronous motor (PMSM) is presented. The controller is developed based on modular design for faster calculation and uses fixed-point proportional-integral (PI) method for improved accuracy. Current dq controller is usually implemented in digital signal processor (DSP) based computer. However, DSP based solutions are reaching their physical limits, which are few microseconds. Besides, digital solutions suffer from high implementation cost. In this research, the overall controller is realizing in field programmable gate array (FPGA). FPGA implementation of the overall controlling algorithm will certainly trim down the execution time significantly to guarantee the steadiness of the motor. Agilent 16821A Logic Analyzer is employed to validate the result of the implemented design in FPGA. Experimental results indicate that the proposed current dq PI controller needs only 50 ns of execution time in 40 MHz clock, which is the lowest computational cycle for the era.

  19. High-Speed Current dq PI Controller for Vector Controlled PMSM Drive

    PubMed Central

    Reaz, Mamun Bin Ibne; Rahman, Labonnah Farzana; Chang, Tae Gyu

    2014-01-01

    High-speed current controller for vector controlled permanent magnet synchronous motor (PMSM) is presented. The controller is developed based on modular design for faster calculation and uses fixed-point proportional-integral (PI) method for improved accuracy. Current dq controller is usually implemented in digital signal processor (DSP) based computer. However, DSP based solutions are reaching their physical limits, which are few microseconds. Besides, digital solutions suffer from high implementation cost. In this research, the overall controller is realizing in field programmable gate array (FPGA). FPGA implementation of the overall controlling algorithm will certainly trim down the execution time significantly to guarantee the steadiness of the motor. Agilent 16821A Logic Analyzer is employed to validate the result of the implemented design in FPGA. Experimental results indicate that the proposed current dq PI controller needs only 50 ns of execution time in 40 MHz clock, which is the lowest computational cycle for the era. PMID:24574913

  20. Feedback control for counterflow thrust vectoring with a turbine engine: Experiment design and robust control design and implementation

    NASA Astrophysics Data System (ADS)

    Dores, Delfim Zambujo Das

    2005-11-01

    Engineering research over the last few years has successfully demonstrated the potential of thrust vector control using counterflow at conditions up to Mach 2. Flow configurations that include the pitch vectoring of rectangular jets and multi-axis vector control in diamond and axisymmetric nozzle geometries have been studied. Although bistable (on-off) fluid-based control has been around for some time, the present counterflow thrust vector control is unique because proportional and continuous jet response can be achieved in the absence of moving parts, while avoiding jet attachment, which renders most fluidic approaches unacceptable for aircraft and missile control applications. However, before this study, research had been limited to open-loop studies of counterflow thrust vectoring. For practical implementation it was vital that the counterflow scheme be used in conjunction with feedback control. Hence, the focus of this research was to develop and experimentally demonstrate a feedback control design methodology for counterflow thrust vectoring. This research focused on 2-D (pitch) thrust vectoring and addresses four key modeling issues. The first issue is to determine the measured variable to be commanded since the thrust vector angle is not measurable in real time. The second related issue is to determine the static mapping from the thrust vector angle to this measured variable. The third issue is to determine the dynamic relationship between the measured variable and the thrust vector angle. The fourth issue is to develop dynamic models with uncertainty characterizations. The final and main goal was the design and implementation of robust controllers that yield closed-loop systems with fast response times, and avoid overshoot in order to aid in the avoidance of attachment. These controllers should be simple and easy to implement in real applications. Hence, PID design has been chosen. Robust control design is accomplished by using ℓ1 control theory in

  1. The Effective Population Size of Malaria Mosquitoes: Large Impact of Vector Control

    PubMed Central

    Athrey, Giridhar; Hodges, Theresa K.; Reddy, Michael R.; Overgaard, Hans J.; Matias, Abrahan; Ridl, Frances C.; Kleinschmidt, Immo; Caccone, Adalgisa; Slotman, Michel A.

    2012-01-01

    Malaria vectors in sub-Saharan Africa have proven themselves very difficult adversaries in the global struggle against malaria. Decades of anti-vector interventions have yielded mixed results—with successful reductions in transmission in some areas and limited impacts in others. These varying successes can be ascribed to a lack of universally effective vector control tools, as well as the development of insecticide resistance in mosquito populations. Understanding the impact of vector control on mosquito populations is crucial for planning new interventions and evaluating existing ones. However, estimates of population size changes in response to control efforts are often inaccurate because of limitations and biases in collection methods. Attempts to evaluate the impact of vector control on mosquito effective population size (Ne) have produced inconclusive results thus far. Therefore, we obtained data for 13–15 microsatellite markers for more than 1,500 mosquitoes representing multiple time points for seven populations of three important vector species—Anopheles gambiae, An. melas, and An. moucheti—in Equatorial Guinea. These populations were exposed to indoor residual spraying or long-lasting insecticidal nets in recent years. For comparison, we also analyzed data from two populations that have no history of organized vector control. We used Approximate Bayesian Computation to reconstruct their demographic history, allowing us to evaluate the impact of these interventions on the effective population size. In six of the seven study populations, vector control had a dramatic impact on the effective population size, reducing Ne between 55%–87%, the exception being a single An. melas population. In contrast, the two negative control populations did not experience a reduction in effective population size. This study is the first to conclusively link anti-vector intervention programs in Africa to sharply reduced effective population sizes of malaria vectors

  2. Trypanosomiasis, cardiomyopathy and the risk of ischemic stroke.

    PubMed

    Carod-Artal, Francisco Javier

    2010-05-01

    American (Chagas disease) and African (sleeping sickness) trypanosomiasis are neglected tropical diseases and are a heavy burden in Latin America and Africa, respectively. Chagas disease is an independent risk factor for stroke. Apical aneurysm, heart failure and cardiac arrhythmias are associated with ischemic stroke in chagasic cardiomyopathy. Not all chagasic patients who suffer an ischemic stroke have a severe cardiomyopathy, and stroke may be the first manifestation of Chagas disease. Cardioembolism affecting the middle cerebral artery is the most common stroke subtype. Risk of recurrence is high and careful evaluation of recurrence risk should be addressed. Repolarization changes, low voltage and prolonged QT interval are common electrocardiography alterations in human African trypanosomiasis, and can be found in more than 70% of patients. Epidemiological studies are needed to asses the risk of stroke in African trypanosomiasis perimyocarditis.

  3. Overview of current situation of dengue and dengue vector control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dengue is the most important arbovirus of humans in the world. It is caused by one of four closely related virus serotypes whose primary vector is Aedes aegypti and secondarily by Ae. albopictus. A global dengue pandemic began in Southeast Asia after World War II and has intensified during the las...

  4. Olfactory disruption: towards controlling important insect vectors of disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chemical repellents are used to decrease contacts between insect disease vectors and their hosts, thus reducing the probability of disease transmission. The molecular mechanisms by which repellents have their effects are poorly understood and remain a controversial topic. Here we present recent re...

  5. Trypanosoma cruzi: adaptation to its vectors and its hosts

    PubMed Central

    Noireau, François; Diosque, Patricio; Jansen, Ana Maria

    2009-01-01

    American trypanosomiasis is a parasitic zoonosis that occurs throughout Latin America. The etiological agent, Trypanosoma cruzi, is able to infect almost all tissues of its mammalian hosts and spreads in the environment in multifarious transmission cycles that may or not be connected. This biological plasticity, which is probably the result of the considerable heterogeneity of the taxon, exemplifies a successful adaptation of a parasite resulting in distinct outcomes of infection and a complex epidemiological pattern. In the 1990s, most endemic countries strengthened national control programs to interrupt the transmission of this parasite to humans. However, many obstacles remain to the effective control of the disease. Current knowledge of the different components involved in elaborate system that is American trypanosomiasis (the protozoan parasite T. cruzi, vectors Triatominae and the many reservoirs of infection), as well as the interactions existing within the system, is still incomplete. The Triatominae probably evolve from predatory reduvids in response to the availability of vertebrate food source. However, the basic mechanisms of adaptation of some of them to artificial ecotopes remain poorly understood. Nevertheless, these adaptations seem to be associated with a behavioral plasticity, a reduction in the genetic repertoire and increasing developmental instability. PMID:19250627

  6. A Literature Review of Economic Evaluations for a Neglected Tropical Disease: Human African Trypanosomiasis (“Sleeping Sickness”)

    PubMed Central

    Sutherland, C. Simone; Yukich, Joshua; Goeree, Ron; Tediosi, Fabrizio

    2015-01-01

    Human African trypanosomiasis (HAT) is a disease caused by infection with the parasite Trypanosoma brucei gambiense or T. b. rhodesiense. It is transmitted to humans via the tsetse fly. Approximately 70 million people worldwide were at risk of infection in 1995, and approximately 20,000 people across Africa are infected with HAT. The objective of this review was to identify existing economic evaluations in order to summarise cost-effective interventions to reduce, control, or eliminate the burden of HAT. The studies included in the review were compared and critically appraised in order to determine if there were existing standardised methods that could be used for economic evaluation of HAT interventions or if innovative methodological approaches are warranted. A search strategy was developed using keywords and was implemented in January 2014 in several databases. The search returned a total of 2,283 articles. After two levels of screening, a total of seven economic evaluations were included and underwent critical appraisal using the Scottish Intercollegiate Guidelines Network (SIGN) Methodology Checklist 6: Economic Evaluations. Results from the existing studies focused on the cost-effectiveness of interventions for the control and reduction of disease transmission. Modelling was a common method to forecast long-term results, and publications focused on interventions by category, such as case detection, diagnostics, drug treatments, and vector control. Most interventions were considered cost-effective based on the thresholds described; however, the current treatment, nifurtomix-eflornithine combination therapy (NECT), has not been evaluated for cost-effectiveness, and considerations for cost-effective strategies for elimination have yet to be completed. Overall, the current evidence highlights the main components that play a role in control; however, economic evaluations of HAT elimination strategies are needed to assist national decision makers, stakeholders, and

  7. Multichannel vector field control module for LLRF control of superconducting cavities

    SciTech Connect

    Varghese, P; Chase, B.; Barnes, B.; Branlard, J.; Joireman, P.W.; Klepec, D.; Mavric, U.; Tupikov, V.; /Fermilab

    2007-06-01

    The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33-channel, FPGA based down-conversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. A 32-bit, 400MHz floating point DSP provides additional computational and control capability for calibration and implementation of more complex control algorithms. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a Slot0 CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as data acquisition.

  8. Implementation of integrated vector management for disease vector control in the Eastern Mediterranean: where are we and where are we going?

    PubMed

    Mnzova, A; Williams, J; Bos, R; Zaim, M

    2011-05-01

    Integrated vector management (IVM) is an acknowledged strategy of choice for the prevention and control of vector-borne diseases. The paper describes and documents the progress countries of the World Health Organization (WHO) Eastern Mediterranean Region have made in endorsing and translating the strategy into action at the national level. These include increased political commitment; strengthened intersectoral coordination and partnership; strengthened capacity in entomology and vector control; and scaling up of vector control interventions through universal access. These efforts, however, are compromised by inappropriate institutional arrangements in some countries; weak national capacities to address management of pesticides; , development and spread of vector resistance to insecticides, including to pyrethroids; and the expansion of emerging and re-emerging vector-borne diseases. With WHO leadership and support from partners, countries continue to address these challenges head-on.

  9. Vector control of wind turbine on the basis of the fuzzy selective neural net*

    NASA Astrophysics Data System (ADS)

    Engel, E. A.; Kovalev, I. V.; Engel, N. E.

    2016-04-01

    An article describes vector control of wind turbine based on fuzzy selective neural net. Based on the wind turbine system’s state, the fuzzy selective neural net tracks an maximum power point under random perturbations. Numerical simulations are accomplished to clarify the applicability and advantages of the proposed vector wind turbine’s control on the basis of the fuzzy selective neuronet. The simulation results show that the proposed intelligent control of wind turbine achieves real-time control speed and competitive performance, as compared to a classical control model with PID controllers based on traditional maximum torque control strategy.

  10. Thrust vector control of upper stage with a gimbaled thruster during orbit transfer

    NASA Astrophysics Data System (ADS)

    Wang, Zhaohui; Jia, Yinghong; Jin, Lei; Duan, Jiajia

    2016-10-01

    In launching Multi-Satellite with One-Vehicle, the main thruster provided by the upper stage is mounted on a two-axis gimbal. During orbit transfer, the thrust vector of this gimbaled thruster (GT) should theoretically pass through the mass center of the upper stage and align with the command direction to provide orbit transfer impetus. However, it is hard to be implemented from the viewpoint of the engineering mission. The deviations of the thrust vector from the command direction would result in large velocity errors. Moreover, the deviations of the thrust vector from the upper stage mass center would produce large disturbance torques. This paper discusses the thrust vector control (TVC) of the upper stage during its orbit transfer. Firstly, the accurate nonlinear coupled kinematic and dynamic equations of the upper stage body, the two-axis gimbal and the GT are derived by taking the upper stage as a multi-body system. Then, a thrust vector control system consisting of the special attitude control of the upper stage and the gimbal rotation of the gimbaled thruster is proposed. The special attitude control defined by the desired attitude that draws the thrust vector to align with the command direction when the gimbal control makes the thrust vector passes through the upper stage mass center. Finally, the validity of the proposed method is verified through numerical simulations.

  11. Geospatial Risk Factors of Canine American Trypanosomiasis (Chagas Disease) (42 Cases: 2000-2012).

    PubMed

    Raghavan, Ram K; Saunders, Ashley B; Goodin, Doug G; Anderson, Gary A; Harkin, Kenneth R

    2015-10-01

    American trypanosomiasis or Chagas disease caused by Trypanosoma cruzi affects many mammals, including humans and dogs, in all Latin American countries outside the Caribbean and increasingly also in the southern United States. Dogs are considered as reliable sentinels and have been identified as an important risk factor for the disease in humans in endemic countries. Factors that determine American trypanosomiasis in dogs may therefore have public health relevance. Associations of different environmental, locational, and pet owner socioeconomic conditions were evaluated retrospectively as potential risk factors for American trypanosomiasis status in dogs in a case-control study. Laboratory-confirmed cases received at the Texas A&M University Veterinary Medical Teaching Hospital between the years 2000 and 2012 and candidate risk factor variables extracted from publicly available environmental data and 2010 US Census Bureau were used. The sample included 42 dogs serologically positive and 82 dogs serologically negative determined by indirect immunofluorescent assay. The diagnostic titer was 1:160 (case). Univariate logistic regressions followed by stepwise multivariate logistic modeling were used for variable screening and to determine the strengths of variable associations with case status. Total Edge Contrast Index (odds ratio [OR] = 3.35, 95% confidence interval [CI] 3.10, 3.62), residing in homes that had rural addresses (OR = 2.48, 95% CI 2.43, 2.53), total number of owner occupied housing units in a neighborhood with a householder who is Hispanic or Latino (OR = 1.66, 95% CI 1.04, 2.66), and the total number of housing units in a neighborhood that were built on or prior to year 1980 (OR = 2.22, 95% CI 1.94, 2.55) were identified as risk factors. Suitable awareness campaigns and future research that considers pet owner housing and socioeconomic circumstances are necessary for effective prevention and control of this disease among dogs.

  12. The Cost of Dengue Vector Control Activities in Malaysia by Different Service Providers.

    PubMed

    Packierisamy, P Raviwharmman; Ng, Chiu-Wan; Dahlui, Maznah; Venugopalan, B; Halasa, Yara A; Shepard, Donald S

    2015-11-01

    We examined variations in dengue vector control costs and resource consumption between the District Health Departments (DHDs) and Local Authorities (LAs) to assist informed decision making as to the future roles of these agencies in the delivery of dengue vector control services in Malaysia. Data were collected from the vector control units of DHDs and LAs in 8 selected districts. We captured costs and resource consumption in 2010 for premise inspection for mosquito breeding sites, fogging to destroy adult mosquitoes and larviciding of potential breeding sites. Overall, DHDs spent US$5.62 million or US$679 per case and LAs spent US$2.61 million or US$499 per case. The highest expenditure for both agencies was for fogging, 51.0% and 45.8% of costs for DHDs and LAs, respectively. The DHDs had higher resource costs for human personnel, vehicles, pesticides, and equipment. The findings provide some evidence to rationalize delivery of dengue vector control services in Malaysia.

  13. A Heading and Flight-Path Angle Control of Aircraft Based on Required Acceleration Vector

    NASA Astrophysics Data System (ADS)

    Yoshitani, Naoharu

    This paper describes a control of heading and flight-path angles of aircraft to time-varying command angles. The controller first calculates an acceleration command vector (acV), which is vertical to the velocity vector. acV consists of two components; the one is feedforward acceleration obtained from the rates of command angles, and the other is feedback acceleration obtained from angle deviations by using PID control law. A bank angle command around the velocity vector and commands of pitch and yaw rates are then obtained to generate the required acceleration. A roll rate command is calculated from bank angle deviation. Roll, pitch and yaw rate commands are put into the attitude controller, which can be composed of any suitable control laws such as PID control. The control requires neither aerodynamic coefficients nor online calculation of the inverse dynamics of the aircraft. A numerical simulation illustrates the effects of the control.

  14. Spray Characterization of Ultra-Low-Volume Sprayers Typically Used in Vector Control

    DTIC Science & Technology

    2009-01-01

    control of human disease vectors, such as mosquitoes and flies, and the selection and setup of these machines significantly affects the level of...specific spray application scenarios. KEY WORDS Atomization, droplet size, sprayer, ULV sprays, vector control INTRODUCTION One of the most common methods...size parameters are presented. Table 1. Atomization parameters for oil-based spray solutions. Sprayer Rate (oz/min) Pressure (psi) DV0.1 (mm 6 SD) DV0.5

  15. Controlling the vector of distraction osteogenesis in the management of obstructive sleep apnea

    PubMed Central

    Shilo, Dekel; Emodi, Omri; Aizenbud, Dror; Rachmiel, Adi

    2016-01-01

    Background: Obstructive sleep apnea (OSA) in individuals with craniofacial anomalies can compromise airway and is a serious life-threatening condition. In many cases, tracheostomy is carried out as the treatment of choice. Distraction osteogenesis of the mandible as a treatment modality for OSA is very useful and may spare the need for tracheostomy or allow decannulation, yet controlling the vector of distraction is still a major challenge. We present a method for controlling the vector of distraction. Materials and Methods: Eight patients with severe respiratory distress secondary to a micrognathic mandible were treated by mandibular distraction osteogenesis using either external or internal devices. Temporary anchorage devices (TADs) and orthodontic elastics were used to control the vector of distraction. Cephalometric X-rays, computed tomography, and polysomnographic sleep studies were used to analyze the results. Results: A mean distraction of 22 mm using the internal devices and a mean of 30 mm using the external devices were achieved. Increase in the pharyngeal airway and hyoid bone advancement was also observed. Anterior-posterior advancement of the mandible was noted with no clockwise rotation. Most importantly, clinical improvement in symptoms of OSA, respiratory distress, and feeding was noted. Conclusions: We describe a method for controlling the vector of distraction used as a treatment for OSA. In these cases, TADs were used as an anchorage unit to control the vector of distraction. Our results show excellent clinical and radiographical results. TADs are a simple and nonexpensive method to control the vector of distraction.

  16. [Blood proteins in African trypanosomiasis: variations and statistical interpretations].

    PubMed

    Cailliez, M; Poupin, F; Pages, J P; Savel, J

    1982-01-01

    The estimation of blood orosomucoid, haptoglobin, C-reactive protein and immunoglobulins levels, has enable us to prove a specific proteic profile in the human african trypanosomiasis, as compared with other that of parasitic diseases, and with an healthy african reference group. Data processing informatique by principal components analysis, provide a valuable pool for epidemiological surveys.

  17. Application of three controls optimally in a vector-borne disease - a mathematical study

    NASA Astrophysics Data System (ADS)

    Kar, T. K.; Jana, Soovoojeet

    2013-10-01

    We have proposed and analyzed a vector-borne disease model with three types of controls for the eradication of the disease. Four different classes for the human population namely susceptible, infected, recovered and vaccinated and two different classes for the vector populations namely susceptible and infected are considered. In the first part of our analysis the disease dynamics are described for fixed controls and some inferences have been drawn regarding the spread of the disease. Next the optimal control problem is formulated and solved considering control parameters as time dependent. Different possible combination of controls are used and their effectiveness are compared by numerical simulation.

  18. Developmental Testing of Electric Thrust Vector Control Systems for Manned Launch Vehicle Applications

    NASA Technical Reports Server (NTRS)

    Bates, Lisa B.; Young, David T.

    2012-01-01

    This paper describes recent developmental testing to verify the integration of a developmental electromechanical actuator (EMA) with high rate lithium ion batteries and a cross platform extensible controller. Testing was performed at the Thrust Vector Control Research, Development and Qualification Laboratory at the NASA George C. Marshall Space Flight Center. Electric Thrust Vector Control (ETVC) systems like the EMA may significantly reduce recurring launch costs and complexity compared to heritage systems. Electric actuator mechanisms and control requirements across dissimilar platforms are also discussed with a focus on the similarities leveraged and differences overcome by the cross platform extensible common controller architecture.

  19. Experimental and theoretical comparison of the Probe Thrust Vector Control concept

    NASA Technical Reports Server (NTRS)

    Cavalleri, Robert; Tiarn, Weihnurng; Lewis, Lynn

    1991-01-01

    A concept that offers an alternate method for thrust vector control of liquid or solid propellant rockets is the use of a solid body or probe that is inserted on demand through the wall of the rocket nozzle. This Probe Thrust Vector Control (PTVC) concept is an alternative to that of a gimbaled nozzle or a Liquid Injection Thrust Vector control system. The viability of the PTVC concept can be assessed either experimentally and/or with the use of CFD. A purely experimental assessment is time consuming and expensive, whereas a CFD assessment is time- and cost-effective. Two key requirements of the concept are PTVC vectoring performance and active cooling requirements for the probe to maintain its thermal and structural integrity. The objective of the work reported here is presentation of experimental subscale cold flow tests and comparison of these tests with CFD predictions and the response time of the PTVC system.

  20. Launching the first postgraduate diploma in medical entomology and disease vector control in Pakistan.

    PubMed

    Rathor, H R; Mnzava, A; Bile, K M; Hafeez, A; Zaman, S

    2010-01-01

    The Health Services Academy has launched a 12-month postgraduate diploma course in medical entomology and disease vector control. The objective is to create a core of experts trained to prevent and control vector-borne diseases. The course is a response to the serious health and socioeconomic burden caused by a number of vector-borne diseases in Pakistan. The persistence, emergence and re-emergence of these diseases is mainly attributed to the scarcity of trained vector-control experts. The training course attempts to fill the gap in trained manpower and thus reduce the morbidity and mortality due to these diseases, resulting in incremental gains to public health. This paper aims to outline the steps taken to establish the course and the perceived challenges to be addressed in order to sustain its future implementation.

  1. Stakeholder Narratives on Trypanosomiasis, Their Effect on Policy and the Scope for One Health

    PubMed Central

    Grant, Catherine; Anderson, Neil; Machila, Noreen

    2015-01-01

    Background This paper explores the framings of trypanosomiasis, a widespread and potentially fatal zoonotic disease transmitted by tsetse flies (Glossina species) affecting both humans and livestock. This is a country case study focusing on the political economy of knowledge in Zambia. It is a pertinent time to examine this issue as human population growth and other factors have led to migration into tsetse-inhabited areas with little historical influence from livestock. Disease transmission in new human-wildlife interfaces such as these is a greater risk, and opinions on the best way to manage this are deeply divided. Methods A qualitative case study method was used to examine the narratives on trypanosomiasis in the Zambian policy context through a series of key informant interviews. Interviewees included key actors from international organisations, research organisations and local activists from a variety of perspectives acknowledging the need to explore the relationships between the human, animal and environmental sectors. Principal Findings Diverse framings are held by key actors looking from, variously, the perspectives of wildlife and environmental protection, agricultural development, poverty alleviation, and veterinary and public health. From these viewpoints, four narratives about trypanosomiasis policy were identified, focused around four different beliefs: that trypanosomiasis is protecting the environment, is causing poverty, is not a major problem, and finally, that it is a Zambian rather than international issue to contend with. Within these narratives there are also conflicting views on the best control methods to use and different reasoning behind the pathways of response. These are based on apparently incompatible priorities of people, land, animals, the economy and the environment. The extent to which a One Health approach has been embraced and the potential usefulness of this as a way of reconciling the aims of these framings and narratives is

  2. A Simple Design Method Based on Vector Control of AC Machines with LC Filter

    NASA Astrophysics Data System (ADS)

    Saito, Ryosuke; Kubota, Hisao

    This paper presents a simple voltage control system of AC machines using PWM voltage source inverter with output LC filters. By assuming a motor as a current source, the voltage is controlled by a simple proportional differential (PD) control. The vector control and PD control can be separately controlled in this system. A method for disturbance rejection is also described. The effectiveness of the proposed method is verified by simulations and experiments.

  3. Determinants of Human African Trypanosomiasis Elimination via Paratransgenesis.

    PubMed

    Gilbert, Jennifer A; Medlock, Jan; Townsend, Jeffrey P; Aksoy, Serap; Ndeffo Mbah, Martial; Galvani, Alison P

    2016-03-01

    Human African trypanosomiasis (HAT), transmitted by tsetse flies, has historically infected hundreds of thousands of individuals annually in sub-Saharan Africa. Over the last decade, concerted control efforts have reduced reported cases to below 10,000 annually, bringing complete elimination within reach. A potential technology to eliminate HAT involves rendering the flies resistant to trypanosome infection. This approach can be achieved through the introduction of transgenic Sodalis symbiotic bacteria that have been modified to produce a trypanocide, and propagated via Wolbachia symbionts, which confer a reproductive advantage to the paratransgenic tsetse. However, the population dynamics of these symbionts within tsetse flies have not yet been evaluated. Specifically, the key factors that determine the effectiveness of paratransgenesis have yet to be quantified. To identify the impact of these determinants on T.b. gambiense and T.b. rhodesiense transmission, we developed a mathematical model of trypanosome transmission that incorporates tsetse and symbiont population dynamics. We found that fecundity and mortality penalties associated with Wolbachia or recombinant Sodalis colonization, probabilities of vertical transmission, and tsetse migration rates are fundamental to the feasibility of HAT elimination. For example, we determined that HAT elimination could be sustained over 25 years when Wolbachia colonization minimally impacted fecundity or mortality, and when the probability of recombinant Sodalis vertical transmission exceeded 99.9%. We also found that for a narrow range of recombinant Sodalis vertical transmission probability (99.9-90.6% for T.b. gambiense and 99.9-85.8% for T.b. rhodesiense), cumulative HAT incidence was reduced between 30% and 1% for T.b. gambiense and between 21% and 3% for T.b. rhodesiense, although elimination was not predicted. Our findings indicate that fitness and mortality penalties associated with paratransgenic symbionts, as well

  4. Determinants of Human African Trypanosomiasis Elimination via Paratransgenesis

    PubMed Central

    Gilbert, Jennifer A.; Medlock, Jan; Townsend, Jeffrey P.; Aksoy, Serap

    2016-01-01

    Human African trypanosomiasis (HAT), transmitted by tsetse flies, has historically infected hundreds of thousands of individuals annually in sub-Saharan Africa. Over the last decade, concerted control efforts have reduced reported cases to below 10,000 annually, bringing complete elimination within reach. A potential technology to eliminate HAT involves rendering the flies resistant to trypanosome infection. This approach can be achieved through the introduction of transgenic Sodalis symbiotic bacteria that have been modified to produce a trypanocide, and propagated via Wolbachia symbionts, which confer a reproductive advantage to the paratransgenic tsetse. However, the population dynamics of these symbionts within tsetse flies have not yet been evaluated. Specifically, the key factors that determine the effectiveness of paratransgenesis have yet to be quantified. To identify the impact of these determinants on T.b. gambiense and T.b. rhodesiense transmission, we developed a mathematical model of trypanosome transmission that incorporates tsetse and symbiont population dynamics. We found that fecundity and mortality penalties associated with Wolbachia or recombinant Sodalis colonization, probabilities of vertical transmission, and tsetse migration rates are fundamental to the feasibility of HAT elimination. For example, we determined that HAT elimination could be sustained over 25 years when Wolbachia colonization minimally impacted fecundity or mortality, and when the probability of recombinant Sodalis vertical transmission exceeded 99.9%. We also found that for a narrow range of recombinant Sodalis vertical transmission probability (99.9–90.6% for T.b. gambiense and 99.9–85.8% for T.b. rhodesiense), cumulative HAT incidence was reduced between 30% and 1% for T.b. gambiense and between 21% and 3% for T.b. rhodesiense, although elimination was not predicted. Our findings indicate that fitness and mortality penalties associated with paratransgenic symbionts, as

  5. Future challenges for parasitology: vector control and one health in the Americas.

    PubMed

    Little, Susan E

    2013-08-01

    "One Health" is a term that encapsulates and underscores the inherent interrelatedness of the health of people, animals, and the environment. Vector-borne infections are central in one health. Many arthropod vectors readily feed on humans and other animals, serving as an ideal conduit to move pathogens between a wide spectrum of potential hosts. As ecological niches flux, opportunities arise for vectors to interact with novel species, allowing infectious agents to broaden both geographic and host ranges. Habitat change has been linked to the emergence of novel human and veterinary disease agents, and can dramatically facilitate expansion opportunities by allowing existing vector populations to flourish and by supporting the establishment of new pathogen maintenance systems. At the same time, control efforts can be hindered by the development of parasiticide and pesticide resistance, foiling efforts to meet these challenges. Using examples drawn from representative diseases important in one health in the Americas, including rickettsial infections, Lyme borreliosis, Chagas disease, and West Nile virus, this paper reviews key aspects of vector-borne disease maintenance cycles that present challenges for one health in the Americas, including emergence of vector-borne disease agents, the impact of habitat change on vector-borne disease transmission, and the complexities faced in developing effective control programs. Novel strategies will be required to effectively combat these infections in the future if we are to succeed in the goal of fostering an environment which supports healthy animals and healthy people.

  6. Required duration of combined annual ivermectin treatment and vector control in the Onchocerciasis Control Programme in west Africa.

    PubMed Central

    Plaisier, A. P.; Alley, E. S.; van Oortmarssen, G. J.; Boatin, B. A.; Habbema, J. D.

    1997-01-01

    In the extension areas of the Onchocerciasis Control Programme in West Africa, aerial larviciding is supplemented with annual ivermectin treatment, mainly to achieve better control of morbidity. The purpose of this study is to determine whether and to what extent the addition of annual ivermectin treatment permits earlier cessation of vector control than originally recommended. The effectiveness of combined ivermectin distribution and vector control was assessed using an epidemiological model. Model predictions suggest that, dependent on the pre-control endemicity of the area and the proportion of persons treated during each ivermectin round, large-scale annual treatment permits a considerable reduction in the duration of vector control. Taking into account uncertainty about the efficacy of ivermectin, our results indicate that, provided treatment coverage is at least 65% and there is no importation of infection from elsewhere, 12 years of combined control will be sufficient to reduce the risk of recrudescence to below 1% in even the most afflicted areas. PMID:9277011

  7. Vector-control response in a post-flood disaster setting, Honiara, Solomon Islands, 2014

    PubMed Central

    Musto, Jennie; Bugoro, Hugo; Butafa, Charles; Sio, Alison; Joshua, Cynthia

    2016-01-01

    Problem The close quartering and exposed living conditions in evacuation centres and the potential increase in vector density after flooding in Solomon Islands resulted in an increased risk of exposure for the occupants to vectorborne diseases. Context In April 2014, Solomon Islands experienced a flash flooding event that affected many areas and displaced a large number of people. In the capital, Honiara, nearly 10 000 people were housed in emergency evacuation centres at the peak of the post-flood emergency. At the time of the floods, the number of dengue cases was increasing, following a record outbreak in 2013. Action The National Vector Borne Disease Control Programme with the assistance of the World Health Organization implemented an emergency vector-control response plan to provide protection to the at-risk populations in the evacuation centres. The National Surveillance Unit also activated an early warning disease surveillance system to monitor communicable diseases, including dengue and malaria. Outcome Timely and strategic application of the emergency interventions probably prevented an increase in dengue and malaria cases in the affected areas. Discussion Rapid and appropriate precautionary vector-control measures applied in a post-natural disaster setting can prevent and mitigate vectorborne disease incidences. Collecting vector surveillance data allows better analysis of vector-control operations’ effectiveness. PMID:27757255

  8. A review of ecological factors associated with the epidemiology of wildlife trypanosomiasis in the luangwa and zambezi valley ecosystems of zambia.

    PubMed

    Munang'andu, Hetron Mweemba; Siamudaala, Victor; Munyeme, Musso; Nalubamba, King Shimumbo

    2012-01-01

    Trypanosomiasis has been endemic in wildlife in Zambia for more than a century. The disease has been associated with neurological disorders in humans. Current conservation strategies by the Zambian government of turning all game reserves into state-protected National Parks (NPs) and game management areas (GMAs) have led to the expansion of the wildlife and tsetse population in the Luangwa and Zambezi valley ecosystem. This ecological niche lies in the common tsetse fly belt that harbors the highest tsetse population density in Southern Africa. Ecological factors such as climate, vegetation and rainfall found in this niche allow for a favorable interplay between wild reservoir hosts and vector tsetse flies. These ecological factors that influence the survival of a wide range of wildlife species provide adequate habitat for tsetse flies thereby supporting the coexistence of disease reservoir hosts and vector tsetse flies leading to prolonged persistence of trypanosomiasis in the area. On the other hand, increase in anthropogenic activities poses a significant threat of reducing the tsetse and wildlife habitat in the area. Herein, we demonstrate that while conservation of wildlife and biodiversity is an important preservation strategy of natural resources, it could serve as a long-term reservoir of wildlife trypanosomiasis.

  9. Cost-effectiveness of algorithms for confirmation test of human African trypanosomiasis.

    PubMed

    Lutumba, Pascal; Meheus, Filip; Robays, Jo; Miaka, Constantin; Kande, Victor; Büscher, Philippe; Dujardin, Bruno; Boelaert, Marleen

    2007-10-01

    The control of Trypanosoma brucei gambiense human African trypanosomiasis (HAT) is compromised by low sensitivity of the routinely used parasitologic confirmation tests. More sensitive alternatives, such as mini-anion exchange centrifugation technique (mAECT) or capillary tube centrifugation (CTC), are more expensive. We used formal decision analysis to assess the cost-effectiveness of alternative HAT confirmation algorithms in terms of cost per life saved. The effectiveness of the standard method, a combination of lymph node puncture (LNP), fresh blood examination (FBE), and thick blood film (TBF), was 36.8%; the LNP-FBE-CTC-mAECT sequence reached almost 80%. The cost per person examined ranged from euro1.56 for LNP-FBE-TBF to euro2.99 for LNP-TBF-CTC-mAECT-CATT (card agglutination test for trypanosomiasis) titration. LNP-TBF-CTC-mAECT was the most cost-effective in terms of cost per life saved. HAT confirmation algorithms that incorporate concentration techniques are more effective and efficient than the algorithms that are currently and routinely used by several T.b. gambiense control programs.

  10. Control of Ducted Fan Flying Object Using Thrust Vectoring

    NASA Astrophysics Data System (ADS)

    Miwa, Masafumi; Shigematsu, Yuki; Yamashita, Takashi

    Recently, R/C helicopter is used in fields of aerial photography and aerial investigation. But helicopter rotor blades are not covered, and the thrust is generated by high rotational speed. Thus R/C helicopter has a high risk of damage. In this study, we developed a new flying object using ducted fans instead of rotor blades. At first, PD control was employed for pitch and roll attitude control, but it caused steady state error. Moreover, PI-D control was used instead of PD control, and it reduced the steady state error. We succeeded to achieve stable hovering by 3-axes (roll, pitch and yaw axis) attitude control.

  11. Design and test of a high power electromechanical actuator for thrust vector control

    NASA Technical Reports Server (NTRS)

    Cowan, J. R.; Myers, W. N.

    1992-01-01

    NASA-Marshall is involved in the development of electromechanical actuators (EMA) for thrust-vector control (TVC) system testing and implementation in spacecraft control/gimballing systems, with a view to the replacement of hydraulic hardware. TVC system control is furnished by solid state controllers and power supplies; a pair of resolvers supply position feedback to the controller for precise positioning. Performance comparisons between EMA and hydraulic TVC systems are performed.

  12. Omni-axis secondary injection thrust vector control system

    NASA Technical Reports Server (NTRS)

    Kirkley, D. J.

    1973-01-01

    The concept, development, design study and preliminary analysis and layout of the required digital logic scheme to be used for injection valve control are presented. An application and optimization study of an Omni-Axis Secondary Injection Control System applicable to the proposed Space Shuttle Pressure Fed Engine is reported. Technical definition and analysis control procedures and test routines, as well as a supporting set of drawing sketches and reference manual, are enclosed.

  13. An agent-vector-host-environment model for controlling small arms and light weapons.

    PubMed

    Pinto, Andrew D; Sharma, Malika; Muggah, Robert

    2011-05-01

    Armed violence is a significant public health problem. It results in fatal and non-fatal injuries and disrupts social and economic processes that are essential to the health of individuals and communities. We argue that an agent-vector-host-environment model can be helpful in understanding and describing the availability and misuse of small arms and light weapons. Moreover, such a model can assist in identifying potential control points and in developing mitigation strategies. These concepts have been developed from analogous vector control programs and are applied to controlling arms to reduce their misuse. So-called 'denormalization' and 'de-legitimization' campaigns that focus on the vector - including the industry producing these commodities - can be based on the experience of public health in controlling tobacco use and exposure. This model can assist health professionals, civil society and governments in developing comprehensive strategies to limit the production, distribution and misuse of small arms and light weapons.

  14. Automated innovative diagnostic, data management and communication tool, for improving malaria vector control in endemic settings.

    PubMed

    Vontas, John; Mitsakakis, Konstantinos; Zengerle, Roland; Yewhalaw, Delenasaw; Sikaala, Chadwick Haadezu; Etang, Josiane; Fallani, Matteo; Carman, Bill; Müller, Pie; Chouaïbou, Mouhamadou; Coleman, Marlize; Coleman, Michael

    2016-01-01

    Malaria is a life-threatening disease that caused more than 400,000 deaths in sub-Saharan Africa in 2015. Mass prevention of the disease is best achieved by vector control which heavily relies on the use of insecticides. Monitoring mosquito vector populations is an integral component of control programs and a prerequisite for effective interventions. Several individual methods are used for this task; however, there are obstacles to their uptake, as well as challenges in organizing, interpreting and communicating vector population data. The Horizon 2020 project "DMC-MALVEC" consortium will develop a fully integrated and automated multiplex vector-diagnostic platform (LabDisk) for characterizing mosquito populations in terms of species composition, Plasmodium infections and biochemical insecticide resistance markers. The LabDisk will be interfaced with a Disease Data Management System (DDMS), a custom made data management software which will collate and manage data from routine entomological monitoring activities providing information in a timely fashion based on user needs and in a standardized way. The ResistanceSim, a serious game, a modern ICT platform that uses interactive ways of communicating guidelines and exemplifying good practices of optimal use of interventions in the health sector will also be a key element. The use of the tool will teach operational end users the value of quality data (relevant, timely and accurate) to make informed decisions. The integrated system (LabDisk, DDMS & ResistanceSim) will be evaluated in four malaria endemic countries, representative of the vector control challenges in sub-Saharan Africa, (Cameroon, Ivory Coast, Ethiopia and Zambia), highly representative of malaria settings with different levels of endemicity and vector control challenges, to support informed decision-making in vector control and disease management.

  15. Host Intracellular Signaling Events and Pro-inflammatory Cytokine Production in African Trypanosomiasis

    PubMed Central

    Kuriakose, Shiby M.; Singh, Rani; Uzonna, Jude E.

    2016-01-01

    Pathogens, such as bacteria, viruses, and parasites, possess specific molecules or proteins that are recognized by several host innate immune receptors, leading to the activation of several intracellular signaling molecules and pathways. The magnitude and quality of these events significantly affect the outcome of infection. African trypanosomes, including Trypanosoma congolense, are capable of manipulating the host immune response, including the activity of macrophages, which are the key immune cells that contribute to the immunopathogenesis of African trypanosomiasis. Although it is known that immune hyperactivation and excessive pro-inflammatory cytokine production are the hallmarks of African trypanosomiasis, the mechanisms through which these events are triggered are poorly defined. However, it is known that macrophages may play a significant role in these processes, because phagocytosis of trypanosomes by macrophages initiates intracellular signal transduction cascades that lead to the release of pro-inflammatory cytokines and alteration in cell function. This review highlights recent progress in our understanding of the innate immune receptors, signaling pathways, and transcription factors involved in T. congolense-induced pro-inflammatory cytokine production in macrophages. It will reveal the existence of complex signaling events through which the parasite modulates the host immune response, thus identifying novel targets that could aid in designing strategies to effectively control the disease. PMID:27242788

  16. Position Sensorless Vector Control for Permanent Magnet Synchronous Motors Based on Maximum Torque Control Frame

    NASA Astrophysics Data System (ADS)

    Hida, Hajime; Tomigashi, Yoshio; Kishimoto, Keiji

    High efficiency drive can be achieved by the maximum torque-per-ampere (MTPA) control which used reluctance torque effectively. However, the calculations for estimating rotor position and for controlling the d-axis current are required. The motor parameters of inductance etc. that are easily affected by magnetic saturation are included in those calculations. This paper proposes a new MTPA control method, which is robust against changes of motor parameters caused by magnetic saturation. In addition, complex calculation for d-axis current or reference to the table is not necessary. In this method, we define a novel coordinate frame, which has one axis aligned with the current vector of the MTPA control, and estimate the frame directly. Because the parameter Lqm for estimating the frame is less affected by the magnetic saturation than the conventional Lq, the effect of magnetic saturation on the position estimation can be greatly suppressed. First, an extended electromotive force model based on the proposed frame and a parameter Lqm for an estimation of the frame are derived. Next, the effectiveness of this proposed method is confirmed by simulations and experiments.

  17. Mosquito vector biology and control in Latin America - A 25th Symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 25th Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 81st Annual Meeting in New Orleans, LA, in March 2015. The principal objective, for the previous 24 symposia, was to promote participation in the AMCA by vector control spec...

  18. Mosquito vector biology and control in Latin America - a 24th symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 24th Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 80th Annual Meeting in Seattle, WA in February 2014. The principal objective, as for the previous 23 symposia, was to promote participation in the AMCA by vector control spe...

  19. MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATIN AMERICA - A 19TH SYMPOSIUM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 19th Annual Latin American symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 75th Annual Meeting in New Orleans, LA, in April 2009. The principal objective, as for the previous 18 symposia, was to promote participation in the AMCA by vector control s...

  20. Mosquito vector biology and control in Latin America - A 21st symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 21st Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 77th Annual Meeting in Anaheim, CA in March 2011. The principal objective, as for the previous 20 symposia, was to promote participation in the AMCA by vector control specia...

  1. Mosquito vector biology and control in Latin America - a 20TH symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 20th Annual Latin American symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 76th Annual Meeting in Lexington, KY in March 2010. The principal objective, as for the previous 19 symposia, was to promote participation in the AMCA by vector control spec...

  2. Mosquito vector biology and control in Latin America - a 22nd Symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 22nd Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 78th Annual Meeting in Austin, TX in February 2012. The principal objective, as for the previous 21 symposia, was to promote participation in the AMCA by vector control spec...

  3. MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATIN AMERICA- An 18TH SYMPOSIUM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 18th Annual Latin American symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 74th Annual Meeting in Sparks, NV, in March 2008. The principal objective, as for the previous 17 symposia, was to promote participation in the AMCA by vector control speci...

  4. Fluidic scale model multi-plane thrust vector control test results

    NASA Technical Reports Server (NTRS)

    Chiarelli, Charles; Johnsen, Raymond K.; Shieh, Chih F.; Wing, David J.

    1993-01-01

    An experimental investigation has been conducted at the NASA Langley 16-Foot Transonic Tunnel Static Test Facility to determine the concept feasibility of using fluidics to achieve multiplane thrust vector control in a 2D convergent-divergent (2D-CD) fixed aperture nozzle. Pitch thrust vector control is achieved by injection of flow through a slot in the divergent flap into the primary nozzle flow stream. Yaw vector control results from secondary air delivered tangentially to vertical Coanda flaps. These flaps are offset laterally and aligned parallel to the primary nozzle side walls. All tests were conducted at static (no external flow) conditions. Flow visualization was conducted using a paint flow technique and Focus Schlieren. Significant levels of pitch deflection angles (19 deg) were achieved at low pressure ratios and practical levels (14 deg) resulted at typical intermediate power settings. The ability of the Coanda surface blowing concept to produce yaw deflection was limited to NPR not greater than 4.

  5. Sustainability of vector control strategies in the Gran Chaco Region: current challenges and possible approaches

    PubMed Central

    Gürtler, Ricardo E

    2011-01-01

    Sustainability has become a focal point of the international agenda. At the heart of its range of distribution in the Gran Chaco Region, the elimination of Triatoma infestans has failed, even in areas subject to intensive professional vector control efforts. Chagas disease control programs traditionally have been composed of two divorced entities: a vector control program in charge of routine field operations (bug detection and insecticide spraying) and a disease control program in charge of screening blood donors, diagnosis, etiologic treatment and providing medical care to chronic patients. The challenge of sustainable suppression of bug infestation and Trypanosoma cruzi transmission can be met through integrated disease management, in which vector control is combined with active case detection and treatment to increase impact, cost-effectiveness and public acceptance in resource-limited settings. Multi-stakeholder involvement may add sustainability and resilience to the surveillance system. Chagas vector control and disease management must remain a regional effort within the frame of sustainable development rather than being viewed exclusively as a matter of health pertinent to the health sector. Sustained and continuous coordination between governments, agencies, control programs, academia and the affected communities is critical. PMID:19753458

  6. Treatment options for second-stage gambiense human African trypanosomiasis.

    PubMed

    Eperon, Gilles; Balasegaram, Manica; Potet, Julien; Mowbray, Charles; Valverde, Olaf; Chappuis, François

    2014-11-01

    Treatment of second-stage gambiense human African trypanosomiasis relied on toxic arsenic-based derivatives for over 50 years. The availability and subsequent use of eflornithine, initially in monotherapy and more recently in combination with nifurtimox (NECT), has drastically improved the prognosis of treated patients. However, NECT logistic and nursing requirements remain obstacles to its deployment and use in peripheral health structures in rural sub-Saharan Africa. Two oral compounds, fexinidazole and SCYX-7158, are currently in clinical development. The main scope of this article is to discuss the potential impact of new oral therapies to improve diagnosis-treatment algorithms and patients' access to treatment, and to contribute to reach the objectives of the recently launched gambiense human African trypanosomiasis elimination program.

  7. Treatment options for second-stage gambiense human African trypanosomiasis

    PubMed Central

    Eperon, Gilles; Balasegaram, Manica; Potet, Julien; Mowbray, Charles; Valverde, Olaf; Chappuis, François

    2014-01-01

    Treatment of second-stage gambiense human African trypanosomiasis relied on toxic arsenic-based derivatives for over 50 years. The availability and subsequent use of eflornithine, initially in monotherapy and more recently in combination with nifurtimox (NECT), has drastically improved the prognosis of treated patients. However, NECT logistic and nursing requirements remain obstacles to its deployment and use in peripheral health structures in rural sub-Saharan Africa. Two oral compounds, fexinidazole and SCYX-7158, are currently in clinical development. The main scope of this article is to discuss the potential impact of new oral therapies to improve diagnosis-treatment algorithms and patients’ access to treatment, and to contribute to reach the objectives of the recently launched gambiense human African trypanosomiasis elimination program. PMID:25204360

  8. Human African trypanosomiasis of the CNS: current issues and challenges

    PubMed Central

    Kennedy, Peter G.E.

    2004-01-01

    Human African trypanosomiasis (HAT), also known as sleeping sickness, is a major cause of mortality and morbidity in sub-Saharan Africa. Current therapy with melarsoprol for CNS HAT has unacceptable side-effects with an overall mortality of 5%. This review discusses the issues of diagnosis and staging of CNS disease, its neuropathogenesis, and the possibility of new therapies for treating late-stage disease. PMID:14966556

  9. Fighting Arbovirus Transmission: Natural and Engineered Control of Vector Competence in Aedes Mosquitoes

    PubMed Central

    Kean, Joy; Rainey, Stephanie M.; McFarlane, Melanie; Donald, Claire L.; Schnettler, Esther; Kohl, Alain; Pondeville, Emilie

    2015-01-01

    Control of aedine mosquito vectors, either by mosquito population reduction or replacement with refractory mosquitoes, may play an essential role in the fight against arboviral diseases. In this review, we will focus on the development and application of biological approaches, both natural or engineered, to limit mosquito vector competence for arboviruses. The study of mosquito antiviral immunity has led to the identification of a number of host response mechanisms and proteins that are required to control arbovirus replication in mosquitoes, though more factors influencing vector competence are likely to be discovered. We will discuss key aspects of these pathways as targets either for selection of naturally resistant mosquito populations or for mosquito genetic manipulation. Moreover, we will consider the use of endosymbiotic bacteria such as Wolbachia, which in some cases have proven to be remarkably efficient in disrupting arbovirus transmission by mosquitoes, but also the use of naturally occurring insect-specific viruses that may interfere with arboviruses in mosquito vectors. Finally, we will discuss the use of paratransgenesis as well as entomopathogenic fungi, which are also proposed strategies to control vector competence. PMID:26463078

  10. Fighting Arbovirus Transmission: Natural and Engineered Control of Vector Competence in Aedes Mosquitoes.

    PubMed

    Kean, Joy; Rainey, Stephanie M; McFarlane, Melanie; Donald, Claire L; Schnettler, Esther; Kohl, Alain; Pondeville, Emilie

    2015-03-23

    Control of aedine mosquito vectors, either by mosquito population reduction or replacement with refractory mosquitoes, may play an essential role in the fight against arboviral diseases. In this review, we will focus on the development and application of biological approaches, both natural or engineered, to limit mosquito vector competence for arboviruses. The study of mosquito antiviral immunity has led to the identification of a number of host response mechanisms and proteins that are required to control arbovirus replication in mosquitoes, though more factors influencing vector competence are likely to be discovered. We will discuss key aspects of these pathways as targets either for selection of naturally resistant mosquito populations or for mosquito genetic manipulation. Moreover, we will consider the use of endosymbiotic bacteria such as Wolbachia, which in some cases have proven to be remarkably efficient in disrupting arbovirus transmission by mosquitoes, but also the use of naturally occurring insect-specific viruses that may interfere with arboviruses in mosquito vectors. Finally, we will discuss the use of paratransgenesis as well as entomopathogenic fungi, which are also proposed strategies to control vector competence.

  11. [Control of vectors of human onchocerciasis in intertropical Africa (author's transl)].

    PubMed

    Philippon, B; Le Berre, R

    1978-01-01

    First the authors make short comments on the two Simuliidae species complexes vectors of African human onchocerciasis (S. damnosum s.l. and S. neavei), as well as on the reasons for renewed interest in the control of those vectors; then they review the various possible methods of control (ecological, biological, genetical and chemical methods) and they finally detail the methodology of anti-S. damnosum chemical larviciding which is the only kind or large scale control presently used against onchocerciasis vectors. The experiences and results of the previous campaigns resulted in the large Onchocerciasis Control Programme in Volta River Basin (O.C.P.) which now appears as a model for present and future control measures against S. damnosum. This Programme is briefly described, together with its results, problems (reinvasion) and orientations. As a conclusion, the excellent level of control of the vectors and onchocerciasis transmission which is obtained is emphasized and it is expected that in the future new large scale campaigns using O.C.P. experience may be initiated.

  12. Heritable strategies for controlling insect vectors of disease

    PubMed Central

    Burt, Austin

    2014-01-01

    Mosquito-borne diseases are causing a substantial burden of mortality, morbidity and economic loss in many parts of the world, despite current control efforts, and new complementary approaches to controlling these diseases are needed. One promising class of new interventions under development involves the heritable modification of the mosquito by insertion of novel genes into the nucleus or of Wolbachia endosymbionts into the cytoplasm. Once released into a target population, these modifications can act to reduce one or more components of the mosquito population's vectorial capacity (e.g. the number of female mosquitoes, their longevity or their ability to support development and transmission of the pathogen). Some of the modifications under development are designed to be self-limiting, in that they will tend to disappear over time in the absence of recurrent releases (and hence are similar to the sterile insect technique, SIT), whereas other modifications are designed to be self-sustaining, spreading through populations even after releases stop (and hence are similar to traditional biological control). Several successful field trials have now been performed with Aedes mosquitoes, and such trials are helping to define the appropriate developmental pathway for this new class of intervention. PMID:24821918

  13. A comparative analysis of the relative efficacy of vector-control strategies against dengue fever.

    PubMed

    Amaku, Marcos; Coutinho, Francisco Antonio Bezerra; Raimundo, Silvia Martorano; Lopez, Luis Fernandez; Nascimento Burattini, Marcelo; Massad, Eduardo

    2014-03-01

    Dengue is considered one of the most important vector-borne infection, affecting almost half of the world population with 50 to 100 million cases every year. In this paper, we present one of the simplest models that can encapsulate all the important variables related to vector control of dengue fever. The model considers the human population, the adult mosquito population and the population of immature stages, which includes eggs, larvae and pupae. The model also considers the vertical transmission of dengue in the mosquitoes and the seasonal variation in the mosquito population. From this basic model describing the dynamics of dengue infection, we deduce thresholds for avoiding the introduction of the disease and for the elimination of the disease. In particular, we deduce a Basic Reproduction Number for dengue that includes parameters related to the immature stages of the mosquito. By neglecting seasonal variation, we calculate the equilibrium values of the model's variables. We also present a sensitivity analysis of the impact of four vector-control strategies on the Basic Reproduction Number, on the Force of Infection and on the human prevalence of dengue. Each of the strategies was studied separately from the others. The analysis presented allows us to conclude that of the available vector control strategies, adulticide application is the most effective, followed by the reduction of the exposure to mosquito bites, locating and destroying breeding places and, finally, larvicides. Current vector-control methods are concentrated on mechanical destruction of mosquitoes' breeding places. Our results suggest that reducing the contact between vector and hosts (biting rates) is as efficient as the logistically difficult but very efficient adult mosquito's control.

  14. A Small-molecule-controlled System for Efficient Pseudotyping of Prototype Foamy Virus Vectors

    PubMed Central

    Ho, Yu-Ping; Schnabel, Viktor; Swiersy, Anka; Stirnnagel, Kristin; Lindemann, Dirk

    2012-01-01

    Foamy virus (FV) vector systems have recently demonstrated their power as efficient gene transfer tools for different target tissues. Unfortunately, FVs cannot be naturally pseudotyped by heterologous viral glycoproteins due to an unusual particle morphogenesis involving a FV Env-dependent particle release process. Therefore, current FV vector systems are constrained to the broad host cell range provided by the cognate viral glycoprotein. We evaluated different approaches for pseudotyping of FV vectors, in which the specific FV Gag–Env interaction, essential for particle egress, is substituted by a small-molecule controlled heterodimerization (HD) system. In one system developed, one HD-domain (HDD) is fused to a membrane-targeting domain (MTD), such as the human immunodeficiency virus (HIV) Gag matrix (MA) subunit, with a second fused to the FV capsid protein. Coexpression of both components with different heterologous viral glycoproteins allowed an efficient, dimerizer-dependent pseudotyping of FV capsids. With this system FV vesicular stomatitis virus glycoprotein (VSV-G) pseudotype titers greater than 1 × 106 IU/ml were obtained, at levels comparable to authentic FV vector particles. As a proof-of-principle we demonstrate that Pac2 cells, naturally resistant to FV vectors, become permissive to FV VSV-G pseudotypes. Similar to other retroviral vectors, this FV pseudotyping system now enables adaptation of cell-specific targeting approaches for FVs. PMID:22472951

  15. A community empowerment strategy embedded in a routine dengue vector control programme: a cluster randomised controlled trial.

    PubMed

    Castro, Marta; Sánchez, Lizet; Pérez, Dennis; Carbonell, Nestor; Lefèvre, Pierre; Vanlerberghe, Veerle; Van der Stuyft, Patrick

    2012-05-01

    The non-sustainability of vertically organised dengue vector control programmes led to pleas for changing the emphasis towards community-based strategies. We conducted a cluster randomised controlled trial with 16 intervention and 16 control clusters to test the effectiveness of a community empowerment strategy intertwined with the routine dengue vector control programme in La Lisa, Havana City, Cuba. The intervention included four components on top of routine control: organisation and management; entomological risk surveillance; capacity building; and community work for vector control. In the control clusters, routine activities continued without interference. The community participation score increased from 1.4 to 3.4. Good knowledge of breeding sites increased by 52.8% and 27.5% in the intervention and control clusters, respectively. There were no changes in adequate Aedes aegypti control practices at household level in the control clusters, but in the intervention clusters adequacy increased by 36.2%. At baseline, the Breteau indices (BI) were approximately 0.1 and were comparable; they fluctuated over time but became different with the launch of the community-based dengue control activities in the intervention clusters. Over the intervention period, the BI remained 53% (95% CI 22-92%) lower in these clusters than in the control clusters. The empowerment strategy increased community involvement and added effectiveness to routine A. aegypti control.

  16. Low-magnetic-field control of electric polarization vector in a helimagnet.

    PubMed

    Ishiwata, Shintaro; Taguchi, Yasujiro; Murakawa, Hiroshi; Onose, Yoshinori; Tokura, Yoshinori

    2008-03-21

    The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of +/-30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba2Mg2Fe12O22, which shows the helimagnetic spin structure with the propagation vector k0 parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k0, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis.

  17. [Evaluation of vector control techniques: an economic approach].

    PubMed

    Audibert, M

    2009-04-01

    Programs of disease control must be evaluated. Evaluation of these programs in terms of public health is straightforward but should be carried out in conjunction with economic evaluation to measure the cost effectiveness and cost-benefit ratio. The purpose of this report is to clarify the importance of economic evaluation by explaining why it is necessary, when it should be carried out, and what methods should be used. Program evaluation is a process with several steps. Each step is associated with specific indicators. Determining these indicators is a prerequisite for construction of the database needed for evaluation. Two methods are proposed for data analysis, i.e., a simple one for cost-effectiveness and cost-benefit analysis and a more sophisticated one for impact analysis that must take into consideration treated and non-treated groups. Economic evaluation of disease control programs is as important as epidemiologic evaluation. However this evaluation cannot be carried out as a standalone procedure but only within a multidisciplinary framework.

  18. Investigations on the control of bilharziasis vectors in Israel*

    PubMed Central

    Saliternik, Z.; Witenberg, G.

    1959-01-01

    In spite of the arrival in Israel over the past decade of large numbers of immigrants infected with bilharziasis and although during that period there have been two sporadic outbreaks of the disease, there seems little immediate danger of bilharziasis spreading in the country. However, hydrographical, agricultural and economic conditions are subject to rapid changes in Israel and the present favourable situation may not be lasting. In anticipation, therefore, of possible outbreaks, laboratory experiments have been conducted to evaluate the efficacy in the control of Bulinus ova and adult snails and schistosome cercariae of a number of known molluscides and other substances. Although similar studies have been made in several other countries, it was felt advisable to repeat them under local hydrological conditions, particularly in view of the high carbonate content of the local waters. While most of the substances tested exert some molluscicidal action, only copper sulfate, sodium pentachlorophenate and common salt were found to be of practical value. PMID:14441019

  19. Analysis of Power Converter Losses in Vector Control System of a Self-Excited Induction Generator

    NASA Astrophysics Data System (ADS)

    Bašić, Mateo; Vukadinović, Dinko; Polić, Miljenko

    2014-03-01

    This paper provides analysis of losses in the hysteresis-driven three-phase power converter with IGBTs and free-wheeling diodes. The converter under consideration is part of the self-excited induction generator (SEIG) vector control system. For the analysis, the SEIG vector control system is used in which the induction generator iron losses are taken into account. The power converter losses are determined by using a suitable loss estimation algorithm reported in literature. The chosen algorithm allows the power converter losses to be determined both by type (switching/conduction losses) and by converter component (IGBT/diode losses). The overall power converter losses are determined over wide ranges of rotor speed, dc-link voltage and load resistance, and subsequently used for offline correction of the overall control system's losses (efficiency) obtained through control system simulations with an ideal power converter. The control system's efficiency values obtained after the correction are compared with the measured values.

  20. Chagas disease vector control in Tupiza, southern Bolivia.

    PubMed

    Guillen, G; Diaz, R; Jemio, A; Cassab, J A; Pinto, C T; Schofield, C J

    1997-01-01

    Heavy domestic and peridomestic infestations of Triatoma infestans were controlled in two villages in southern Bolivia by the application of deltamethrin SC25 (2.5% suspension concentrate) at a target dose of 25 mg a.i./m2. Actual applied dose was monitored by HPLC analysis of filter papers placed at various heights on the house walls, and was shown to range from 0 to 59.6 about a mean of 28.5 mg a.i./m2. Wall bioassays showed high mortality of T. infestans during the first month after the application of deltamethrin. Mortality declined to zero as summer temperatures increased, but reappeared with the onset of the following winter. In contrast, knockdown was apparent throughout the trial, showing no discernible temperature dependence. House infestation rates, measured by manual sampling and use of paper sheets to collect bug faeces, declined from 79% at the beginning of the trial to zero at the 6 month evaluation. All but one of the houses were still free of T. infestans at the final evaluation 12 months after spraying, although a small number of bugs were found at this time in 5 of 355 peridomestic dependencies. Comparative cost studies endorse the recommendation of large-scale application of deltamethrin, or pyrethroid of similar cost-effectiveness, as a means to eliminate domestic T. infestans populations in order to interrupt transmission of Chagas disease.

  1. Mosquito Vector Control and Biology in Latin America - A 17th Symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 17th Annual Latin America American symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 73rd Annual Meeting in Orlando, FL, in April 2007. The principal objective, as for the previous 16 symposia, was to promote participation in the AMCA by vector cont...

  2. Further evaluation of spray characterization of sprayers typically used in vector control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Droplet size spectra from different sprayers used to generate sprays for controlling insects that may vector diseases were measured by a laser diffraction instrument. The objective of this work was to measure the droplet size generated by different sprayers with water- and oil-based spray solutions...

  3. Population control of the malaria vector Anopheles pseudopunctipennis by habitat manipulation.

    PubMed Central

    Bond, J. Guillermo; Rojas, Julio C.; Arredondo-Jiménez, Juan I.; Quiroz-Martínez, Humberto; Valle, Javier; Williams, Trevor

    2004-01-01

    Insect vector-borne diseases continue to present a major challenge to human health. Understanding the factors that regulate the size of mosquito populations is considered fundamental to the ability to predict disease transmission rates and for vector population control. The mosquito, Anopheles pseudopunctipennis, a vector of Plasmodium spp., breeds in riverside pools containing filamentous algae in Mesoamerica. Breeding pools along 3 km sections of the River Coatan, Chiapas, Mexico were subjected to algal extraction or left as controls in a cross-over trial extending over 2 years. Initial densities of An. pseudopunctipennis larvae were directly proportional to the prevalence of filamentous algae in each breeding site. The extraction of algae brought about a striking decline in the density of An. pseudopunctipennis larvae sustained for about six weeks, and a concurrent reduction in the adult population in both years of the study. Mark-release experiments indicated that dispersal from adjacent untreated areas was unlikely to exert an important influence on the magnitude of mosquito control that we observed. Habitat manipulation by extraction of filamentous algae offers a unique opportunity for sustainable control of this malaria vector. This technique may represent a valuable intervention, complimenting insecticide spraying of households, to minimize Plasmodium transmission rates in Mesoamerica. PMID:15475337

  4. Intrusive versus domiciliated triatomines and the challenge of adapting vector control practices against Chagas disease

    PubMed Central

    Waleckx, Etienne; Gourbière, Sébastien; Dumonteil, Eric

    2015-01-01

    Chagas disease prevention remains mostly based on triatomine vector control to reduce or eliminate house infestation with these bugs. The level of adaptation of triatomines to human housing is a key part of vector competence and needs to be precisely evaluated to allow for the design of effective vector control strategies. In this review, we examine how the domiciliation/intrusion level of different triatomine species/populations has been defined and measured and discuss how these concepts may be improved for a better understanding of their ecology and evolution, as well as for the design of more effective control strategies against a large variety of triatomine species. We suggest that a major limitation of current criteria for classifying triatomines into sylvatic, intrusive, domiciliary and domestic species is that these are essentially qualitative and do not rely on quantitative variables measuring population sustainability and fitness in their different habitats. However, such assessments may be derived from further analysis and modelling of field data. Such approaches can shed new light on the domiciliation process of triatomines and may represent a key tool for decision-making and the design of vector control interventions. PMID:25993504

  5. Evaluation of spray droplet spectrum of sprayers used for vector control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Droplet spectra data were collected from spray equipment intended for use in vector control by the US Department of Defense pest management programs to determine if they produce droplets in the ultra-low volume (ULV) spectrum. Droplets generated by 26 sprayers utilizing water + non-ionic surfactant...

  6. Mosquito vector biology and control in Latin America - a 23rd symposium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 23nd Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 79th Annual Meeting in Atlantic City, NJ in February 2013. The principal objective, as for the previous 22 symposia, was to promote participation in the AMCA by vector contr...

  7. An innovative ecohealth intervention for Chagas disease vector control in Yucatan, Mexico

    PubMed Central

    Waleckx, Etienne; Camara-Mejia, Javier; Ramirez-Sierra, Maria Jesus; Cruz-Chan, Vladimir; Rosado-Vallado, Miguel; Vazquez-Narvaez, Santos; Najera-Vazquez, Rosario; Gourbière, Sébastien; Dumonteil, Eric

    2015-01-01

    Background Non-domiciliated (intrusive) triatomine vectors remain a challenge for the sustainability of Chagas disease vector control as these triatomines are able to transiently (re-)infest houses. One of the best-characterized examples is Triatoma dimidiata from the Yucatan peninsula, Mexico, where adult insects seasonally infest houses between March and July. Methods We focused our study on three rural villages in the state of Yucatan, Mexico, in which we performed a situation analysis as a first step before the implementation of an ecohealth (ecosystem approach to health) vector control intervention. Results The identification of the key determinants affecting the transient invasion of human dwellings by T. dimidiata was performed by exploring associations between bug presence and qualitative and quantitative variables describing the ecological, biological and social context of the communities. We then used a participatory action research approach for implementation and evaluation of a control strategy based on window insect screens to reduce house infestation by T. dimidiata. Conclusions This ecohealth approach may represent a valuable alternative to vertically-organized insecticide spraying. Further evaluation may confirm that it is sustainable and provides effective control (in the sense of limiting infestation of human dwellings and vector/human contacts) of intrusive triatomines in the region. PMID:25604765

  8. Malaria vector control at a crossroads: public health entomology and the drive to elimination.

    PubMed

    Mnzava, Abraham P; Macdonald, Michael B; Knox, Tessa B; Temu, Emmanuel A; Shiff, Clive J

    2014-09-01

    Vector control has been at the core of successful malaria control. However, a dearth of field-oriented vector biologists threatens to undermine global reductions in malaria burden. Skilled cadres are needed to manage insecticide resistance, to maintain coverage with current interventions, to develop new paradigms for tackling 'residual' transmission and to target interventions as transmission becomes increasingly heterogeneous. Recognising this human resource crisis, in September 2013, WHO Global Malaria Programme issued guidance for capacity building in entomology and vector control, including recommendations for countries and implementing partners. Ministries were urged to develop long-range strategic plans for building human resources for public health entomology and vector control (including skills in epidemiology, geographic information systems, operational research and programme management) and to set in place the requisite professional posts and career opportunities. Capacity building and national ownership in all partner projects and a clear exit strategy to sustain human and technical resources after project completion were emphasised. Implementing partners were urged to support global and regional efforts to enhance public health entomology capacity. While the challenges inherent in such capacity building are great, so too are the opportunities to establish the next generation of public health entomologists that will enable programmes to continue on the path to malaria elimination.

  9. Clustering of Vector Control Interventions Has Important Consequences for Their Effectiveness: A Modelling Study

    PubMed Central

    Lutambi, Angelina Mageni; Chitnis, Nakul; Briët, Olivier J. T.; Smith, Thomas A.; Penny, Melissa A.

    2014-01-01

    Vector control interventions have resulted in considerable reductions in malaria morbidity and mortality. When universal coverage cannot be achieved for financial or logistical reasons, the spatial arrangement of vector control is potentially important for optimizing benefits. This study investigated the effect of spatial clustering of vector control interventions on reducing the population of biting mosquitoes. A discrete-space continuous-time mathematical model of mosquito population dynamics and dispersal was extended to incorporate vector control interventions of insecticide treated bednets (ITNs), Indoor residual Spraying (IRS), and larviciding. Simulations were run at varying levels of coverage and degree of spatial clustering. At medium to high coverage levels of each of the interventions or in combination was more effective to spatially spread these interventions than to cluster them. Suggesting that when financial resources are limited, unclustered distribution of these interventions is more effective. Although it is often stated that locally high coverage is needed to achieve a community effect of ITNs or IRS, our results suggest that if the coverage of ITNs or IRS are insufficient to achieve universal coverage, and there is no targeting of high risk areas, the overall effects on mosquito densities are much greater if they are distributed in an unclustered way, rather than clustered in specific localities. Also, given that interventions are often delivered preferentially to accessible areas, and are therefore clustered, our model results show this may be inefficient. This study provides evidence that the effectiveness of an intervention can be highly dependent on its spatial distribution. Vector control plans should consider the spatial arrangement of any intervention package to ensure effectiveness is maximized. PMID:24823656

  10. A Flight-Path Control of Aircraft Based on Required Acceleration Vector

    NASA Astrophysics Data System (ADS)

    Yoshitani, Naoharu

    This paper presents an automatic flight-path control of aircraft. In the control, a desired flight trajectory is first determined as a sequence of straight lines, arcs and spirals in the three-dimensional space. Commands and command rates of heading and flight-path (climb) angles are then obtained from the desired trajectory. A required acceleration vector of the aircraft is calculated based on the command rates and angle deviations. Desired roll, pitch and yaw rates are then obtained by acceleration controller and are fed to attitude control. The feedback control of acceleration employs conventional PID control technology, without using inverse dynamics of the aircraft, and the attitude control can employ any existing control technologies suitable for the aircraft to be controlled. These make the proposed control relatively simple and easy to implement. Numerical simulations illustrate the effectiveness of the control.

  11. Thailand Momentum on Policy and Practice in Local Legislation on Dengue Vector Control

    PubMed Central

    Bhumiratana, Adisak; Intarapuk, Apiradee; Chujun, Suriyo; Kaewwaen, Wuthichai; Sorosjinda-Nunthawarasilp, Prapa; Koyadun, Surachart

    2014-01-01

    Over a past decade, an administrative decentralization model, adopted for local administration development in Thailand, is replacing the prior centralized (top-down) command system. The change offers challenges to local governmental agencies and other public health agencies at all the ministerial, regional, and provincial levels. A public health regulatory and legislative framework for dengue vector control by local governmental agencies is a national topic of interest because dengue control program has been integrated into healthcare services at the provincial level and also has been given priority in health plans of local governmental agencies. The enabling environments of local administrations are unique, so this critical review focuses on the authority of local governmental agencies responsible for disease prevention and control and on the functioning of local legislation with respect to dengue vector control and practices. PMID:24799896

  12. Genetic shifting: a novel approach for controlling vector-borne diseases

    PubMed Central

    Tabachnick, Walter J.

    2014-01-01

    Rendering populations of vectors of diseases incapable of transmitting pathogens through genetic methods has long been a goal of vector geneticists. We outline a method to achieve this goal that does not involve introduction of any new genetic variants to the target population. Rather we propose that shifting the frequencies of naturally occurring alleles that confer refractoriness to transmission can reduce transmission below a sustainable level. The program employs methods successfully used in plant and animal breeding. Because no artificially constructed genetically modified organisms (GMOs) are introduced into the environment, the method is minimally controversial. We use Aedes aegypti and dengue virus (DENV) for illustrative purposes, but point out the proposed program is generally applicable to vector-borne disease control. PMID:24794113

  13. Drivers, dynamics, and control of emerging vector-borne zoonotic diseases

    PubMed Central

    Kilpatrick, A. Marm; Randolph, Sarah E.

    2013-01-01

    Emerging vector-borne diseases represent an important issue for global health. Many vector-borne pathogens have appeared in new regions in the past two decades, and many endemic diseases have increased in incidence. Although introductions and local emergence are frequently considered distinct processes, many emerging endemic pathogens are in fact invading at a local scale coincident with habitat change. We highlight key differences in the dynamics and disease burden that result from increased pathogen transmission following habitat change compared with the introduction of pathogens to new regions. Truly in situ emergence is commonly driven by changes in human factors as much as by enhanced enzootic cycles whereas pathogen invasion results from anthropogenic trade and travel and suitable conditions for a pathogen, including hosts, vectors, and climate. Once established, ecological factors related to vector characteristics shape the evolutionary selective pressure on pathogens that may result in increased use of humans as transmission hosts. We describe challenges inherent in the control of vector-borne zoonotic diseases and some emerging non-traditional strategies that may be more effective in the long term. PMID:23200503

  14. Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection

    NASA Astrophysics Data System (ADS)

    Zmijanovic, V.; Lago, V.; Sellam, M.; Chpoun, A.

    2014-01-01

    Transverse secondary gas injection into the supersonic flow of an axisymmetric convergent-divergent nozzle is investigated to describe the effects of the fluidic thrust vectoring within the framework of a small satellite launcher. Cold-flow dry-air experiments are performed in a supersonic wind tunnel using two identical supersonic conical nozzles with the different transverse injection port positions. The complex three-dimensional flow field generated by the supersonic cross-flows in these test nozzles was examined. Valuable experimental data were confronted and compared with the results obtained from the numerical simulations. Different nozzle models are numerically simulated under experimental conditions and then further investigated to determine which parameters significantly affect thrust vectoring. Effects which characterize the nozzle and thrust vectoring performances are established. The results indicate that with moderate secondary to primary mass flow rate ratios, ranging around 5 %, it is possible to achieve pertinent vector side forces. It is also revealed that injector positioning and geometry have a strong effect on the shock vector control system and nozzle performances.

  15. The argument for integrating vector control with multiple drug administration campaigns to ensure elimination of lymphatic filariasis

    PubMed Central

    Burkot, TR; Durrheim, DN; Melrose, WD; Speare, R; Ichimori, K

    2006-01-01

    Background There is a danger that mass drug administration campaigns may fail to maintain adequate treatment coverage to achieve lymphatic filariasis elimination. Hence, additional measures to suppress transmission might be needed to ensure the success of the Global Program for the Elimination of Lymphatic Filariasis. Discussion Vector control successfully eliminated lymphatic filariasis when implemented alone or with mass drug administration. Challenges to lymphatic filariasis elimination include uncertainty of the exact level and duration of microfilarial suppression required for elimination, the mobility of infected individuals, consistent non-participation of some infected individuals with mass drug administration, the possible development of anti-filarial drug resistance and treatment strategies in areas co-endemic with loasis. Integration of vector control with mass drug administration can address some of these challenges. The potential benefits of vector control would include: (1) the ability to suppress filariasis transmission without the need to identify all individual 'foci of infection'; (2) minimizing the risk of reestablishment of transmission from imported microfilaria positive individuals; and (3) decreasing the risk of dengue or malaria transmission where, respectively, Aedes or Anopheles are lymphatic filariasis vectors. Summary With adequate sustained treatment coverage, mass drug administration should meet the criteria for elimination of lymphatic filariasis. However, it may be difficult to sustain sufficiently high mass drug administration coverage to achieve lymphatic filariasis elimination in some areas, particularly, where Aedes species are the vectors. Since vector control was effective in controlling and even eliminating lymphatic filariasis transmission, integration of vector control with mass drug administration will ensure the sustainability of transmission suppression and thereby better ensure the success of national filariasis

  16. Vista/F-16 Multi-Axis Thrust Vectoring (MATV) control law design and evaluation

    NASA Technical Reports Server (NTRS)

    Zwerneman, W. D.; Eller, B. G.

    1994-01-01

    For the Multi-Axis Thrust Vectoring (MATV) program, a new control law was developed using multi-axis thrust vectoring to augment the aircraft's aerodynamic control power to provide maneuverability above the normal F-16 angle of attack limit. The control law architecture was developed using Lockheed Fort Worth's offline and piloted simulation capabilities. The final flight control laws were used in flight test to demonstrate tactical benefits gained by using thrust vectoring in air-to-air combat. Differences between the simulator aerodynamics data base and the actual aircraft aerodynamics led to significantly different lateral-directional flying qualities during the flight test program than those identified during piloted simulation. A 'dial-a-gain' flight test control law update was performed in the middle of the flight test program. This approach allowed for inflight optimization of the aircraft's flying qualities. While this approach is not preferred over updating the simulator aerodynamic data base and then updating the control laws, the final selected gain set did provide adequate lateral-directional flying qualities over the MATV flight envelope. The resulting handling qualities and the departure resistance of the aircraft allowed the 422nd_squadron pilots to focus entirely on evaluating the aircraft's tactical utility.

  17. An Assessment of Participatory Integrated Vector Management for Malaria Control in Kenya

    PubMed Central

    Mbogo, Charles; Mwangangi, Joseph; Imbahale, Susan; Kibe, Lydia; Orindi, Benedict; Girma, Melaku; Njui, Annah; Lwande, Wilber; Affognon, Hippolyte; Gichuki, Charity; Mukabana, Wolfgang Richard

    2015-01-01

    Background The World Health Organization (WHO) recommends integrated vector management (IVM) as a strategy to improve and sustain malaria vector control. However, this approach has not been widely adopted. Objectives We comprehensively assessed experiences and findings on IVM in Kenya with a view to sharing lessons that might promote its wider application. Methods The assessment used information from a qualitative external evaluation of two malaria IVM projects implemented between 2006 and 2011 and an analysis of their accumulated entomological and malaria case data. The project sites were Malindi and Nyabondo, located in coastal and western Kenya, respectively. The assessment focused on implementation of five key elements of IVM: integration of vector control methods, evidence-based decision making, intersectoral collaboration, advocacy and social mobilization, and capacity building. Results IVM was more successfully implemented in Malindi than in Nyabondo owing to greater community participation and multistakeholder engagement. There was a significant decline in the proportion of malaria cases among children admitted to Malindi Hospital, from 23.7% in 2006 to 10.47% in 2011 (p < 0.001). However, the projects’ operational research methodology did not allow statistical attribution of the decline in malaria and malaria vectors to specific IVM interventions or other factors. Conclusions Sustaining IVM is likely to require strong participation and support from multiple actors, including community-based groups, non-governmental organizations, international and national research institutes, and various government ministries. A cluster-randomized controlled trial would be essential to quantify the effectiveness and impact of specific IVM interventions, alone or in combination. Citation Mutero CM, Mbogo C, Mwangangi J, Imbahale S, Kibe L, Orindi B, Girma M, Njui A, Lwande W, Affognon H, Gichuki C, Mukabana WR. 2015. An assessment of participatory integrated vector

  18. Design development of the Apollo command and service module thrust vector attitude control systems

    NASA Technical Reports Server (NTRS)

    Peters, W. H.

    1978-01-01

    Development of the Apollo thrust vector control digital autopilot (TVC DAP) was summarized. This is the control system that provided pitch and yaw attitude control during velocity change maneuvers using the main rocket engine on the Apollo service module. A list of ten primary functional requirements for this control system are presented, each being subordinate to a more general requirement appearing earlier on the list. Development process functions were then identified and the essential information flow paths were explored. This provided some visibility into the particular NASA/contractor interface, as well as relationships between the many individual activities.

  19. Vectorial capacity and vector control: reconsidering sensitivity to parameters for malaria elimination

    PubMed Central

    Brady, Oliver J.; Godfray, H. Charles J.; Tatem, Andrew J.; Gething, Peter W.; Cohen, Justin M.; McKenzie, F. Ellis; Perkins, T. Alex; Reiner, Robert C.; Tusting, Lucy S.; Sinka, Marianne E.; Moyes, Catherine L.; Eckhoff, Philip A.; Scott, Thomas W.; Lindsay, Steven W.; Hay, Simon I.; Smith, David L.

    2016-01-01

    Background Major gains have been made in reducing malaria transmission in many parts of the world, principally by scaling-up coverage with long-lasting insecticidal nets and indoor residual spraying. Historically, choice of vector control intervention has been largely guided by a parameter sensitivity analysis of George Macdonald's theory of vectorial capacity that suggested prioritizing methods that kill adult mosquitoes. While this advice has been highly successful for transmission suppression, there is a need to revisit these arguments as policymakers in certain areas consider which combinations of interventions are required to eliminate malaria. Methods and Results Using analytical solutions to updated equations for vectorial capacity we build on previous work to show that, while adult killing methods can be highly effective under many circumstances, other vector control methods are frequently required to fill effective coverage gaps. These can arise due to pre-existing or developing mosquito physiological and behavioral refractoriness but also due to additive changes in the relative importance of different vector species for transmission. Furthermore, the optimal combination of interventions will depend on the operational constraints and costs associated with reaching high coverage levels with each intervention. Conclusions Reaching specific policy goals, such as elimination, in defined contexts requires increasingly non-generic advice from modelling. Our results emphasize the importance of measuring baseline epidemiology, intervention coverage, vector ecology and program operational constraints in predicting expected outcomes with different combinations of interventions. PMID:26822603

  20. Rational spatio-temporal strategies for controlling a Chagas disease vector in urban environments

    PubMed Central

    Levy, Michael Z.; Malaga Chavez, Fernando S.; Cornejo del Carpio, Juan G.; Vilhena, Daril A.; McKenzie, F. Ellis; Plotkin, Joshua B.

    2010-01-01

    The rational design of interventions is critical to controlling communicable diseases, especially in urban environments. In the case of the Chagas disease vector Triatoma infestans, successful control is stymied by the return of the insect after the effectiveness of the insecticide wanes. Here, we adapt a genetic algorithm, originally developed for the travelling salesman problem, to improve the spatio-temporal design of insecticide campaigns against T. infestans, in a complex urban environment. We find a strategy that reduces the expected instances of vector return 34-fold compared with the current strategy of sequential insecticide application to spatially contiguous communities. The relative success of alternative control strategies depends upon the duration of the effectiveness of the insecticide, and it shows chaotic fluctuations in response to unforeseen delays in a control campaign. We use simplified models to analyse the outcomes of qualitatively different spatio-temporal strategies. Our results provide a detailed procedure to improve control efforts for an urban Chagas disease vector, as well as general guidelines for improving the design of interventions against other disease agents in complex environments. PMID:20061346

  1. Biosynthesized silver nanoparticles using floral extract of Chrysanthemum indicum L.--potential for malaria vector control.

    PubMed

    Arokiyaraj, Selvaraj; Dinesh Kumar, Vannam; Elakya, Vijay; Kamala, Tamilselvan; Park, Sung Kwon; Ragam, Muthiah; Saravanan, Muthupandian; Bououdina, Mohomad; Arasu, Mariadhas Valan; Kovendan, Kalimuthu; Vincent, Savariar

    2015-07-01

    Mosquitoes transmit serious human diseases, causing millions of deaths every year. The use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides synthesized of natural products for vector control have been a priority in this area. In the present study, silver nanoparticles (Ag NPs) were green-synthesized using a floral extract of Chrysanthemum indicum screened for larvicidal and pupicidal activity against the first to fourth instar larvae and pupae of the malaria vector Anopheles stephensi mosquitoes. The synthesized Ag NPs were characterized by using UV-vis absorption, X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy techniques. The textures of the yielded Ag NPs were found to be spherical and polydispersed with a mean size in the range of 25-59 nm. Larvae and pupae were exposed to various concentrations of aqueous extract of C. indicum and synthesized Ag NPs for 24 h, and the maximum mortality was observed from the synthesized Ag NPs against the vector A. stephensi (LC50 = 5.07, 10.35, 14.19, 22.81, and 35.05 ppm; LC90 = 29.18, 47.15, 65.53, 87.96, and 115.05 ppm). These results suggest that the synthesized Ag NPs have the potential to be used as an ideal eco-friendly approach for the control of A. stephensi. Additionally, this study provides the larvicidal and pupicidal properties of green-synthesized Ag NPs with the floral extract of C. indicum against vector mosquito species from the geographical location of India.

  2. The continuing problem of human African trypanosomiasis (sleeping sickness).

    PubMed

    Kennedy, Peter G E

    2008-08-01

    Human African trypanosomiasis, also known as sleeping sickness, is a neglected disease, and it continues to pose a major threat to 60 million people in 36 countries in sub-Saharan Africa. Transmitted by the bite of the tsetse fly, the disease is caused by protozoan parasites of the genus Trypanosoma and comes in two types: East African human African trypanosomiasis caused by Trypanosoma brucei rhodesiense and the West African form caused by Trypanosoma brucei gambiense. There is an early or hemolymphatic stage and a late or encephalitic stage, when the parasites cross the blood-brain barrier to invade the central nervous system. Two critical current issues are disease staging and drug therapy, especially for late-stage disease. Lumbar puncture to analyze cerebrospinal fluid will remain the only method of disease staging until reliable noninvasive methods are developed, but there is no widespread consensus as to what exactly defines biologically central nervous system disease or what specific cerebrospinal fluid findings should justify drug therapy for late-stage involvement. All four main drugs used for human African trypanosomiasis are toxic, and melarsoprol, the only drug that is effective for both types of central nervous system disease, is so toxic that it kills 5% of patients who receive it. Eflornithine, alone or combined with nifurtimox, is being used increasingly as first-line therapy for gambiense disease. There is a pressing need for an effective, safe oral drug for both stages of the disease, but this will require a significant increase in investment for new drug discovery from Western governments and the pharmaceutical industry.

  3. Leucocytozoonosis and trypanosomiasis in redstarts in Finland.

    PubMed

    Rintamäki, P T; Huhta, E; Jokimäki, J; Squires-Parsons, D

    1999-07-01

    Leucocytozoon spp. and Trypanosoma spp. blood parasites in the redstart (Phoenicurus phoenicurus) were studied during spring migration 1994 in southern Finland (53 individuals) and the breeding season 1992-1994 in northern Finland (69). Parasite prevalence was higher during the breeding season (48%) than during the migration period (13%), with no age or sex differences in the breeding site birds. In both periods, redstarts were infected by the same blood parasites Leucocytozoon shaartusicum (46% prevalence at the breeding site and 71% during the migration period) and Trypanosoma avium, complex (58% and 43%, respectively). One individual at the breeding site had contracted L. dubreuili and one at the stop-over site had T. everetti. Our results may support the assumption that tissue-hidden parasites relapse during the breeding season when birds may have diminished immune response related to egg production and brood rearing. Another explanation could be that the high abundance of ornithophilic vectors enhance parasite transmission during breeding season in northern Finland.

  4. Human African trypanosomiasis in non-endemic countries.

    PubMed

    Sudarshi, Darshan; Brown, Mike

    2015-02-01

    Human African trypanosomiasis (HAT) or sleeping sickness is a parasitic disease, acquired by the bite of an infected tsetse fly. In non-endemic countries HAT is rare, and therefore the diagnosis may be delayed leading to potentially fatal consequences. In this article the clinical presentation, diagnosis and treatment of the two forms of HAT are outlined. Rhodesiense HAT is an acute illness that presents in tourists who have recently visited game parks in Eastern or Southern Africa, whereas Gambiense HAT has a more chronic clinical course, in individuals from West or Central Africa.

  5. Malaria vector control practices in an irrigated rice agro-ecosystem in central Kenya and implications for malaria control

    PubMed Central

    Ng'ang'a, Peter N; Shililu, Josephat; Jayasinghe, Gayathri; Kimani, Violet; Kabutha, Charity; Kabuage, Lucy; Kabiru, Ephantus; Githure, John; Mutero, Clifford

    2008-01-01

    Background Malaria transmission in most agricultural ecosystems is complex and hence the need for developing a holistic malaria control strategy with adequate consideration of socio-economic factors driving transmission at community level. A cross-sectional household survey was conducted in an irrigated ecosystem with the aim of investigating vector control practices applied and factors affecting their application both at household and community level. Methods Four villages representing the socio-economic, demographic and geographical diversity within the study area were purposefully selected. A total of 400 households were randomly sampled from the four study villages. Both semi-structured questionnaires and focus group discussions were used to gather both qualitative and quantitative data. Results The results showed that malaria was perceived to be a major public health problem in the area and the role of the vector Anopheles mosquitoes in malaria transmission was generally recognized. More than 80% of respondents were aware of the major breeding sites of the vector. Reported personal protection methods applied to prevent mosquito bites included; use of treated bed nets (57%), untreated bed nets (35%), insecticide coils (21%), traditional methods such as burning of cow dung (8%), insecticide sprays (6%), and use of skin repellents (2%). However, 39% of respondents could not apply some of the known vector control methods due to unaffordability (50.5%), side effects (19.9%), perceived lack of effectiveness (16%), and lack of time to apply (2.6%). Lack of time was the main reason (56.3%) reported for non-application of environmental management practices, such as draining of stagnant water (77%) and clearing of vegetations along water canals (67%). Conclusion The study provides relevant information necessary for the management, prevention and control of malaria in irrigated agro-ecosystems, where vectors of malaria are abundant and disease transmission is stable

  6. Operational vector-borne disease surveillance and control: closing the capabilities gap through research at overseas military laboratories.

    PubMed

    Evans, Brian P; Clark, Jeffrey W; Barbara, Kathryn A; Mundal, Kirk D; Furman, Barry D; McAvin, James C; Richardson, Jason H

    2009-01-01

    Malaria, dengue fever, chikungunya virus, leishmaniasis, and a myriad of other vector-borne diseases pose significant threats to the warfighter and to the overall combat effectiveness of units. Military preventive medicine (PM) assets must accurately evaluate the vector-borne disease threat and then implement and/or advise the commander on countermeasures to reduce a particular threat. The success of these measures is contingent upon the biology of the disease vector and on the tools or methods used to conduct vector/pathogen surveillance and vector control. There is a significant gap between the tools available and those required for operational PM assets to provide real-time, effective surveillance and control. A network of US Army and US Navy overseas laboratories is focused on closing the current capabilities gap. Their mission is to develop and field test tools and methods to enhance the combatant commander's ability to identify and mitigate the threat posed by these vector-borne diseases.

  7. Paratransgenesis applied for control of tsetse transmitted sleeping sickness.

    PubMed

    Aksoy, Serap; Weiss, Brian; Attardo, Geoffrey

    2008-01-01

    African trypanosomiasis (sleeping sickness) is a major cause of morbidity and mortality in Subsaharan Africa for human and animal health. In the absence of effective vaccines and efficacious drugs, vector control is an alternative intervention tool to break the disease cycle. This chapter describes the vectorial and symbiotic biology of tsetse with emphasis on the current knowledge on tsetse symbiont genomics and functional biology, and tsetse's trypanosome transmission capability. The ability to culture one of tsetse's commensal symbiotic microbes, Sodalis in vitro has allowed for the development of a genetic transformation system for this organism. Tsetse can be repopulated with the modified Sodalis symbiont, which can express foreign gene products (an approach we refer to as paratransgenic expression system). Expanding knowledge on tsetse immunity effectors, on genomics of tsetse symbionts and on tsetse's parasite transmission biology stands to enhance the development and potential application of paratransgenesis as a new vector-control strategy. We describe the hallmarks of the paratransgenic transformation technology where the modified symbionts expressing trypanocidal compounds can be used to manipulate host functions and lead to the control of trypanosomiasis by blocking trypanosome transmission in the tsetse vector.

  8. [New vector control measures implemented between 2005 and 2011 on Reunion Island: lessons learned from chikungunya epidemic].

    PubMed

    Bâville, M; Dehecq, J S; Reilhes, O; Margueron, T; Polycarpe, D; Filleul, L

    2012-03-01

    A major chikungunya outbreak concerned 38% of people living in Reunion Island in 2005-2006. Chikungunya is an arthropod-born-virus disease conveyed by mosquitoes called Aedes albopictus. The health agency in Indian Ocean is responsible for vector control. Previously, in the early 40s, vector control concerned only malaria prophylaxis in La Réunion. Then, during the chikungunya outbreak, a new vector control team was installed and learned from this epidemic. The lessons drawn from chikungunya outbreak in La Réunion are about global executive management and organization linked the local partners and population. The lessons also concern technical topics such as the need of scientific research about vectors and vector-control methods. Finally, the regional cooperation in Indian Ocean (Réunion, Maurice, Seychelles, Comoros, Madagascar) has to be developed to share epidemiologic and entomologic data in order to prevent new chikungunya or dengue outbreak.

  9. Hydrologic modeling to screen potential environmental management methods for malaria vector control in Niger

    NASA Astrophysics Data System (ADS)

    Gianotti, Rebecca L.; Bomblies, Arne; Eltahir, Elfatih A. B.

    2009-08-01

    This paper describes the first use of Hydrology-Entomology and Malaria Transmission Simulator (HYDREMATS), a physically based distributed hydrology model, to investigate environmental management methods for malaria vector control in the Sahelian village of Banizoumbou, Niger. The investigation showed that leveling of topographic depressions where temporary breeding habitats form during the rainy season, by altering pool basin microtopography, could reduce the pool persistence time to less than the time needed for establishment of mosquito breeding, approximately 7 days. Undertaking soil surface plowing can also reduce pool persistence time by increasing the infiltration rate through an existing pool basin. Reduction of the pool persistence time to less than the rainfall interstorm period increases the frequency of pool drying events, removing habitat for subadult mosquitoes. Both management approaches could potentially be considered within a given context. This investigation demonstrates that management methods that modify the hydrologic environment have significant potential to contribute to malaria vector control in water-limited, Sahelian Africa.

  10. Krylov vector methods for model reduction and control of flexible structures

    NASA Technical Reports Server (NTRS)

    Su, Tzu-Jeng; Craig, Roy R., Jr.

    1992-01-01

    Krylov vectors and the concept of parameter matching are combined here to develop model-reduction algorithms for structural dynamics systems. The method is derived for a structural dynamics system described by a second-order matrix differential equation. The reduced models are shown to have a promising application in the control of flexible structures. It can eliminate control and observation spillovers while requiring only the dynamic spillover terms to be considered. A model-order reduction example and a flexible structure control example are provided to show the efficacy of the method.

  11. Improvement of Direct Torque Control by using a Space Vector Modulation Control of Three-Level Inverter

    NASA Astrophysics Data System (ADS)

    Achalhi, A.; Bezza, M.; Belbounaguia, N.; Boujoudi, B.

    2017-03-01

    The performances of Direct Torque Control (DTC) of Induction machine are highly related to the inverter used therewith. The purpose of this paper is to highlight the efficiency of the space vector modulation (SVM) control of three level inverter associated with the direct torque control. The first part of this work is devoted to present the mathematical models of the DTC associated with 2-levels inverter then 3-levels inverter. Simulations on Matlab/Simulink will allow a comparative study to highlight advantages of the use of three levels inverter. The second part is devoted to the improvement of the DTC associated with a 3-levels inverter by application of the space vector modulation strategy (SVM) in order to manage the switching frequency and reduce harmonics. The efficiency of this solution will be attested by simulation on Matlab/Simulink.

  12. Modeling and path-following control of a vector-driven stratospheric satellite

    NASA Astrophysics Data System (ADS)

    Zheng, Zewei; Chen, Tian; Xu, Ming; Zhu, Ming

    2016-05-01

    The stratospheric satellite driven by steady prevailing winds in the stratosphere must be controlled in its longitudinal excursion to keep a latitudinal orbital flight. In a reliable and high-precision control system, an available system model must come first. In this paper, we study the 6 degree-of-freedom (DOF) modeling and path-following problem of a novel stratospheric satellite which consists of a high-altitude helium balloon, a truss and two vector-motor-driven propellers. To keep a latitudinal flight orbit, an algorithm for accurate latitudinal path following is proposed based on the theories of vector field and sliding mode control. Moreover, a forward velocity controller is added to the control algorithm to maintain a constant velocity. Finally, a series of open-loop control simulations are completed to verify the effectiveness of the model in the performance of the stratospheric satellite dynamics, and path-following control simulation results demonstrate the effectiveness of the proposed control algorithm.

  13. Preliminary design study of a lateral-directional control system using thrust vectoring

    NASA Technical Reports Server (NTRS)

    Lallman, F. J.

    1985-01-01

    A preliminary design of a lateral-directional control system for a fighter airplane capable of controlled operation at extreme angles of attack is developed. The subject airplane is representative of a modern twin-engine high-performance jet fighter, is equipped with ailerons, rudder, and independent horizontal-tail surfaces. Idealized bidirectional thrust-vectoring engine nozzles are appended to the mathematic model of the airplane to provide additional control moments. Optimal schedules for lateral and directional pseudo control variables are calculated. Use of pseudo controls results in coordinated operation of the aerodynamic and thrust-vectoring controls with minimum coupling between the lateral and directional airplane dynamics. Linear quadratic regulator designs are used to specify a preliminary flight control system to improve the stability and response characteristics of the airplane. Simulated responses to step pilot control inputs are stable and well behaved. For lateral stick deflections, peak stability axis roll rates are between 1.25 and 1.60 rad/sec over an angle-of-attack range of 10 deg to 70 deg. For rudder pedal deflections, the roll rates accompanying the sideslip responses can be arrested by small lateral stick motions.

  14. Cost-Effectiveness of Chagas Disease Vector Control Strategies in Northwestern Argentina

    PubMed Central

    Vazquez-Prokopec, Gonzalo M.; Spillmann, Cynthia; Zaidenberg, Mario; Kitron, Uriel; Gürtler, Ricardo E.

    2009-01-01

    Background Control and prevention of Chagas disease rely mostly on residual spraying of insecticides. In Argentina, vector control shifted from a vertical to a fully horizontal strategy based on community participation between 1992 and 2004. The effects of such strategy on Triatoma infestans, the main domestic vector, and on disease transmission have not been assessed. Methods and Findings Based on retrospective (1993–2004) records from the Argentinean Ministry of Health for the Moreno Department, Northwestern Argentina, we performed a cost-effectiveness (CE) analysis and compared the observed CE of the fully horizontal vector control strategy with the expected CE for a vertical or a mixed (i.e., vertical attack phase followed by horizontal surveillance) strategy. Total direct costs (in 2004 US$) of the horizontal and mixed strategies were, respectively, 3.3 and 1.7 times lower than the costs of the vertical strategy, due to reductions in personnel costs. The estimated CE ratios for the vertical, mixed and horizontal strategies were US$132, US$82 and US$45 per averted human case, respectively. When per diems were excluded from the costs (i.e., simulating the decentralization of control activities), the CE of vertical, mixed and horizontal strategies was reduced to US$60, US$42 and US$32 per averted case, respectively. Conclusions and Significance The mixed strategy would have averted between 1.6 and 4.0 times more human cases than the fully horizontal strategy, and would have been the most cost-effective option to interrupt parasite transmission in the Department. In rural and dispersed areas where waning vertical vector programs cannot accomplish full insecticide coverage, alternative strategies need to be developed. If properly implemented, community participation represents not only the most appealing but also the most cost-effective alternative to accomplish such objectives. PMID:19156190

  15. Innovative dengue vector control interventions in Latin America: what do they cost?

    PubMed Central

    Basso, César; Beltrán-Ayala, Efraín; Mitchell-Foster, Kendra; Cortés, Sebastián; Manrique-Saide, Pablo; Guillermo-May, Guillermo; Carvalho de Lima, Edilmar

    2016-01-01

    Background Five studies were conducted in Fortaleza (Brazil), Girardot (Colombia), Machala (Ecuador), Acapulco (Mexico), and Salto (Uruguay) to assess dengue vector control interventions tailored to the context. The studies involved the community explicitly in the implementation, and focused on the most productive breeding places for Aedes aegypti. This article reports the cost analysis of these interventions. Methods We conducted the costing from the perspective of the vector control program. We collected data on quantities and unit costs of the resources used to deliver the interventions. Comparable information was requested for the routine activities. Cost items were classified, analyzed descriptively, and aggregated to calculate total costs, costs per house reached, and incremental costs. Results Cost per house of the interventions were $18.89 (Fortaleza), $21.86 (Girardot), $30.61 (Machala), $39.47 (Acapulco), and $6.98 (Salto). Intervention components that focused mainly on changes to the established vector control programs seem affordable; cost savings were identified in Salto (−21%) and the clean patio component in Machala (−12%). An incremental cost of 10% was estimated in Fortaleza. On the other hand, there were also completely new components that would require sizeable financial efforts (installing insecticide-treated nets in Girardot and Acapulco costs $16.97 and $24.96 per house, respectively). Conclusions The interventions are promising, seem affordable and may improve the cost profile of the established vector control programs. The costs of the new components could be considerable, and should be assessed in relation to the benefits in reduced dengue burden. PMID:26924235

  16. Opportunities for Improved Chagas Disease Vector Control Based on Knowledge, Attitudes and Practices of Communities in the Yucatan Peninsula, Mexico

    PubMed Central

    Rosecrans, Kathryn; Cruz-Martin, Gabriela; King, Ashley; Dumonteil, Eric

    2014-01-01

    Background Chagas disease is a vector-borne parasitic disease of major public health importance. Current prevention efforts are based on triatomine vector control to reduce transmission to humans. Success of vector control interventions depends on their acceptability and value to affected communities. We aimed to identify opportunities for and barriers to improved vector control strategies in the Yucatan peninsula, Mexico. Methodology/principal findings We employed a sequence of qualitative and quantitative research methods to investigate knowledge, attitudes and practices surrounding Chagas disease, triatomines and vector control in three rural communities. Our combined data show that community members are well aware of triatomines and are knowledgeable about their habits. However, most have a limited understanding of the transmission dynamics and clinical manifestations of Chagas disease. While triatomine control is not a priority for community members, they frequently use domestic insecticide products including insecticide spray, mosquito coils and plug-in repellents. Families spend about $32 US per year on these products. Alternative methods such as yard cleaning and window screens are perceived as desirable and potentially more effective. Screens are nonetheless described as unaffordable, in spite of a cost comparable to the average annual spending on insecticide products. Conclusion/Significance Further education campaigns and possibly financing schemes may lead families to redirect their current vector control spending from insecticide products to window screens. Also, synergism with mosquito control efforts should be further explored to motivate community involvement and ensure sustainability of Chagas disease vector control. PMID:24676038

  17. An Adaptive Supervisory Sliding Fuzzy Cerebellar Model Articulation Controller for Sensorless Vector-Controlled Induction Motor Drive Systems

    PubMed Central

    Wang, Shun-Yuan; Tseng, Chwan-Lu; Lin, Shou-Chuang; Chiu, Chun-Jung; Chou, Jen-Hsiang

    2015-01-01

    This paper presents the implementation of an adaptive supervisory sliding fuzzy cerebellar model articulation controller (FCMAC) in the speed sensorless vector control of an induction motor (IM) drive system. The proposed adaptive supervisory sliding FCMAC comprised a supervisory controller, integral sliding surface, and an adaptive FCMAC. The integral sliding surface was employed to eliminate steady-state errors and enhance the responsiveness of the system. The adaptive FCMAC incorporated an FCMAC with a compensating controller to perform a desired control action. The proposed controller was derived using the Lyapunov approach, which guarantees learning-error convergence. The implementation of three intelligent control schemes—the adaptive supervisory sliding FCMAC, adaptive sliding FCMAC, and adaptive sliding CMAC—were experimentally investigated under various conditions in a realistic sensorless vector-controlled IM drive system. The root mean square error (RMSE) was used as a performance index to evaluate the experimental results of each control scheme. The analysis results indicated that the proposed adaptive supervisory sliding FCMAC substantially improved the system performance compared with the other control schemes. PMID:25815450

  18. Microbial control of malaria: biological warfare against the parasite and its vector.

    PubMed

    Abdul-Ghani, Rashad; Al-Mekhlafi, Abdulsalam M; Alabsi, Mogeeb S

    2012-02-01

    Microbial applications in malaria transmission control have drawn global attention. Mosquito midgut microbiota can modulate vector immunity and block Plasmodium development. Paratransgenic manipulation of bacterial symbionts and Wolbachia can affect reproductive characteristics of mosquitoes. Bacillus-based biolarvicides can control mosquito larvae in different breeding habitats, but their effectiveness differs according to the type of formulation applied, and the physical and ecological conditions of the environment. Entomopathogenic fungi show promise as effective and evolution-proof agents against adult mosquitoes. In addition, transgenic fungi can express anti-plasmodial effector molecules that can target the parasite inside its vector. Despite showing effectiveness in domestic environments as well as against insecticide-resistant mosquitoes, claims towards their deployability in the field and their possible use in integrated vector management programmes have yet to be investigated. Viral pathogens show efficacy in the interruption of sporogonic development of the parasite, and protozoal pathogens exert direct pathogenic potential on larvae and adults with substantial effects on mosquito longevity and fecundity. However, the technology required for their isolation and maintenance impedes their field application. Many agents show promising findings; however, the question remains about the epidemiologic reality of these approaches because even those that have been tried under field conditions still have certain limitations. This review addresses aspects of the microbial control of malaria between proof-of-concept and epidemiologic reality.

  19. Noise-induced hearing loss and associated factors among vector control workers in a Malaysian state.

    PubMed

    Masilamani, Retneswari; Rasib, Abdul; Darus, Azlan; Ting, Anselm Su

    2014-11-01

    This study aims to determine the prevalence and associated factors of noise-induced hearing loss (NIHL) among vector control workers in the state of Negeri Sembilan, Malaysia. This was an analytical cross-sectional study conducted on 181 vector control workers who were working in district health offices in a state in Malaysia. Data were collected using a self-administered questionnaire and audiometry. Prevalence of NIHL was 26% among this group of workers. NIHL was significantly associated with the age-group of 40 years and older, length of service of 10 or more years, current occupational noise exposure, listening to loud music, history of firearms use, and history of mumps/measles infection. Following logistic regression, age of more than 40 years and noise exposure in current occupation were associated with NIHL with an odds ratio of 3.45 (95% confidence interval = 1.68-7.07) and 6.87 (95% confidence interval = 1.54-30.69), respectively, among this group of vector control workers.

  20. Mapping Neglected Swimming Pools from Satellite Data for Urban Vector Control

    NASA Astrophysics Data System (ADS)

    Barker, C. M.; Melton, F. S.; Reisen, W. K.

    2010-12-01

    Neglected swimming pools provide suitable breeding habit for mosquitoes, can contain thousands of mosquito larvae, and present both a significant nuisance and public health risk due to their inherent proximity to urban and suburban populations. The rapid increase and sustained rate of foreclosures in California associated with the recent recession presents a challenge for vector control districts seeking to identify, treat, and monitor neglected pools. Commercial high resolution satellite imagery offers some promise for mapping potential neglected pools, and for mapping pools for which routine maintenance has been reestablished. We present progress on unsupervised classification techniques for mapping both neglected pools and clean pools using high resolution commercial satellite data and discuss the potential uses and limitations of this data source in support of vector control efforts. An unsupervised classification scheme that utilizes image segmentation, band thresholds, and a change detection approach was implemented for sample regions in Coachella Valley, CA and the greater Los Angeles area. Comparison with field data collected by vector control personal was used to assess the accuracy of the estimates. The results suggest that the current system may provide some utility for early detection, or cost effective and time efficient annual monitoring, but additional work is required to address spectral and spatial limitations of current commercial satellite sensors for this purpose.

  1. In silico models for predicting vector control chemicals targeting Aedes aegypti.

    PubMed

    Devillers, J; Lagneau, C; Lattes, A; Garrigues, J C; Clémenté, M M; Yébakima, A

    2014-01-01

    Human arboviral diseases have emerged or re-emerged in numerous countries worldwide due to a number of factors including the lack of progress in vaccine development, lack of drugs, insecticide resistance in mosquitoes, climate changes, societal behaviours, and economical constraints. Thus, Aedes aegypti is the main vector of the yellow fever and dengue fever flaviviruses and is also responsible for several recent outbreaks of the chikungunya alphavirus. As for the other mosquito species, the A. aegypti control relies heavily on the use of insecticides. However, because of increasing resistance to the different families of insecticides, reduction of Aedes populations is becoming increasingly difficult. Despite the unquestionable utility of insecticides in fighting mosquito populations, there are very few new insecticides developed and commercialized for vector control. This is because the high cost of the discovery of an insecticide is not counterbalanced by the 'low profitability' of the vector control market. Fortunately, the use of quantitative structure-activity relationship (QSAR) modelling allows the reduction of time and cost in the discovery of new chemical structures potentially active against mosquitoes. In this context, the goal of the present study was to review all the existing QSAR models on A. aegypti. The homology and pharmacophore models were also reviewed. Specific attention was paid to show the variety of targets investigated in Aedes in relation to the physiology and ecology of the mosquito as well as the diversity of the chemical structures which have been proposed, encompassing man-made and natural substances.

  2. In silico models for predicting vector control chemicals targeting Aedes aegypti

    PubMed Central

    Devillers, J.; Lagneau, C.; Lattes, A.; Garrigues, J.C.; Clémenté, M.M.; Yébakima, A.

    2014-01-01

    Human arboviral diseases have emerged or re-emerged in numerous countries worldwide due to a number of factors including the lack of progress in vaccine development, lack of drugs, insecticide resistance in mosquitoes, climate changes, societal behaviours, and economical constraints. Thus, Aedes aegypti is the main vector of the yellow fever and dengue fever flaviviruses and is also responsible for several recent outbreaks of the chikungunya alphavirus. As for the other mosquito species, the A. aegypti control relies heavily on the use of insecticides. However, because of increasing resistance to the different families of insecticides, reduction of Aedes populations is becoming increasingly difficult. Despite the unquestionable utility of insecticides in fighting mosquito populations, there are very few new insecticides developed and commercialized for vector control. This is because the high cost of the discovery of an insecticide is not counterbalanced by the ‘low profitability’ of the vector control market. Fortunately, the use of quantitative structure–activity relationship (QSAR) modelling allows the reduction of time and cost in the discovery of new chemical structures potentially active against mosquitoes. In this context, the goal of the present study was to review all the existing QSAR models on A. aegypti. The homology and pharmacophore models were also reviewed. Specific attention was paid to show the variety of targets investigated in Aedes in relation to the physiology and ecology of the mosquito as well as the diversity of the chemical structures which have been proposed, encompassing man-made and natural substances. PMID:25275884

  3. Parasitic diseases in humans transmitted by vectors.

    PubMed

    Cholewiński, Marcin; Derda, Monika; Hadaś, Edward

    2015-01-01

    Despite the considerable progress of medicine, parasitic diseases still pose a great threat to human health and life. Among parasitic diseases, those transmitted by vectors, mainly arthropods, play a particular role. These diseases occur most frequently in the poorest countries and affect a vast part of the human population. They include malaria, babesiosis, trypanosomiasis, leishmaniasis and filariasis. This study presents those vector-transmitted diseases that are responsible for the greatest incidence and mortality of people on a global scale. Attention is focused primarily on diseases transmitted by mosquitoes, flies, Hemiptera and ticks.

  4. An update on the incidence of dengue gaining strength in Saudi Arabia and current control approaches for its vector mosquito

    PubMed Central

    2014-01-01

    Background The cases of dengue reported earlier in the late 1990s from the Kingdom of Saudi Arabia (KSA) occurred in the cities of Jeddah and Makkah. Although the kingdom has ample financial resources to establish effective control measures for the dengue vector, numerous cases of dengue occur and fluctuate in numbers from year to year. This necessitates a serious review of the current vector control strategies being practiced in order to identify the existing shortcomings. This short report provides an update on epidemiology of dengue in KSA (specifically in cities of Jeddah and Makkah) with a critical look at the current vector control strategies. Findings In 2013, 4411 cases of dengue were reported, with 8 cases of mortality. This number of dengue incidence was four times higher compared to 2012. In 2013, the highest number of 1272 dengue cases was reported in May, while the lowest number (37) of cases was reported in September. Conclusions It is evident that the control strategies of the dengue vector presently employed are inadequate. There seems to be serious deficiencies in following proper scientific procedures during field application(s) of control materials against the vector as is evident by the increases in the number of dengue cases as well as frequent outbreaks of the vector mosquito populations. In this review, some specific suggestions are made to draw attention to the relevant KSA authorities of the possible reasons behind unsuccessful control results and as to how to improve the strategy of dengue vector control in the kingdom. PMID:24890567

  5. Delivery of antihuman African trypanosomiasis drugs across the blood-brain and blood-CSF barriers.

    PubMed

    Sekhar, Gayathri N; Watson, Christopher P; Fidanboylu, Mehmet; Sanderson, Lisa; Thomas, Sarah A

    2014-01-01

    Human African trypanosomiasis (HAT or sleeping sickness) is a potentially fatal disease caused by the parasite, Trypanosoma brucei sp. The parasites are transmitted by the bite of insect vectors belonging to the genus Glossina (tsetse flies) and display a life cycle strategy that is equally spread between human and insect hosts. T.b. gambiense is found in western and central Africa whereas, T.b. rhodesiense is found in eastern and southern Africa. The disease has two clinical stages: a blood stage after the bite of an infected tsetse fly, followed by a central nervous system (CNS) stage where the parasite penetrates the brain; causing death if left untreated. The blood-brain barrier (BBB) makes the CNS stage difficult to treat because it prevents 98% of all known compounds from entering the brain, including some anti-HAT drugs. Those that do enter the brain are toxic compounds in their own right and have serious side effects. There are only a few drugs available to treat HAT and those that do are stage specific. This review summarizes the incidence, diagnosis, and treatment of HAT and provides a close examination of the BBB transport of anti-HAT drugs and an overview of the latest drugs in development.

  6. Silver nanoparticles: a possibility for malarial and filarial vector control technology.

    PubMed

    Soni, Namita; Prakash, Soam

    2014-11-01

    Green synthesis technology is one of the rapid, reliable and best routes for the synthesis of silver nanoparticles (AgNPs). There are bioactive compounds with enormous potential in Azadirachta indica (Neem). The extraordinary mosquitoes warrant nanotechnology to integrate with novel molecules. This will be sustainable technology for future. Here, we synthesized AgNPs using aqueous extracts of leaves and bark of Az. indica (Neem). We tested AgNPs as larvicides, pupicides and adulticides against the malaria vector Anopheles stephensi and filariasis vector Culex quinquefasciatus. The results were obtained using UV-visible spectrophotometer and the images were recorded with a transmission electron microscope (TEM). The efficacy tests were then performed at different concentrations varying many hours by probit analysis. The synthesized AgNPs were spherical in shape and with varied sizes (10.47-nm leaf and 19.22-nm bark). The larvae, pupae and adults of filariasis vector C. quinquefasciatus were found to be more susceptible to our AgNPs than the malaria vector An. stephensi. The first and the second instar larvae of C. quinquefasciatus show a mortality rate of 100% after 30 min of exposure. The results against the pupa of C. quinquefasciatus were recorded as LC₅₀ 4 ppm, LC₉₀ 11 ppm and LC₉₉ 13 ppm after 3 h of exposure. In the case of adult mosquitoes, LC₅₀ 1.06 μL/cm(2), LC₉₀ 2.13 μL/cm(2) and LC₉₉ 2.4 μL/cm(2) were obtained after 4 h of exposure. These results suggest that our AgNPs are environment-friendly for controlling malarial and filarial vectors.

  7. Global Status of DDT and Its Alternatives for Use in Vector Control to Prevent Disease

    PubMed Central

    van den Berg, Henk

    2009-01-01

    Objective I review the status of dichlorodiphenyltrichloroethane (DDT), used for disease vector control, along with current evidence on its benefits and risks in relation to the available alternatives. Data sources and extraction Contemporary data on DDT use were largely obtained from questionnaires and reports. I also conducted a Scopus search to retrieve published articles. Data synthesis DDT has been recommended as part of the arsenal of insecticides available for indoor residual spraying until suitable alternatives are available. Approximately 14 countries use DDT for disease control, and several countries are preparing to reintroduce DDT. The effectiveness of DDT depends on local settings and merits close consideration in relation to the alternatives. Concerns about the continued use of DDT are fueled by recent reports of high levels of human exposure associated with indoor spraying amid accumulating evidence on chronic health effects. There are signs that more malaria vectors are becoming resistant to the toxic action of DDT, and that resistance is spreading to new countries. A comprehensive cost assessment of DDT versus its alternatives that takes side effects into account is missing. Effective chemical methods are available as immediate alternatives to DDT, but the choice of insecticide class is limited, and in certain areas the development of resistance is undermining the efficacy of insecticidal tools. New insecticides are not expected in the short term. Nonchemical methods are potentially important, but their effectiveness at program level needs urgent study. Conclusions To reduce reliance on DDT, support is needed for integrated and multipartner strategies of vector control and for the continued development of new technologies. Integrated vector management provides a framework for developing and implementing effective technologies and strategies as sustainable alternatives to reliance on DDT. PMID:20049114

  8. Biochemical evidence of efficacy of potash alum for the control of dengue vector Aedes aegypti (Linnaeus).

    PubMed

    Preet, Shabad; Sneha, A

    2011-06-01

    Aedes aegypti is the primary vector of dengue, yellow fever and chikungunya in India and other South East Asian countries, and novel insecticides for vector control are urgently needed. In the present investigation, efficacy of potash alum, a traditionally known double salt in Indian and Chinese medicine system, was tested against the larvae of dengue vector, A. aegypti. LC(50,) LC(90) and LC(99) values were recorded for various instar larvae where I instar larvae were found to be the most susceptible and IV instar larvae as the least susceptible one. The LC(50) values of crude and standard potash alum of various instar larvae ranged between 15.29 and 48.53 ppm and 20.50-65.10 ppm, respectively. Biochemical changes were also evidenced in IV instar A. aegypti larvae following a sublethal exposure for 24 h in the levels of various nutrient reserves and primary metabolites such as sugar, glycogen, lipids and proteins suggesting possible mode of action responsible for larval mortality. Sugar and glycogen concentrations were measured as 24.6 and 10.67 μg per five larvae in controls which were significantly (p<0.05) reduced by 32.11-93.98% and 39.26-94.47%, respectively, in larvae treated with crude alum. In controls, protein and lipid content were recorded as 210.74 and 94.71 μg per five larvae which dropped up to 26.53% and 25.5%, respectively, in larvae following treatment with crude alum. Moreover, drastic changes were also recorded for DNA content with 25.39-44.17% decrease in crude alum-treated larvae. It is evident from these results that potash alum, a fairly cheaper and readily available ecofriendly compound could be recommended as a potential chemical larvicide against dengue vector at mosquito breeding sites in the vicinity of human dwellings.

  9. Modest additive effects of integrated vector control measures on malaria prevalence and transmission in western Kenya

    PubMed Central

    2013-01-01

    Background The effect of integrating vector larval intervention on malaria transmission is unknown when insecticide-treated bed-net (ITN) coverage is very high, and the optimal indicator for intervention evaluation needs to be determined when transmission is low. Methods A post hoc assignment of intervention-control cluster design was used to assess the added effect of both indoor residual spraying (IRS) and Bacillus-based larvicides (Bti) in addition to ITN in the western Kenyan highlands in 2010 and 2011. Cross-sectional, mass parasite screenings, adult vector populations, and cohort of active case surveillance (ACS) were conducted before and after the intervention in three study sites with two- to three-paired intervention-control clusters at each site each year. The effect of larviciding, IRS, ITNs and other determinants of malaria risk was assessed by means of mixed estimating methods. Results Average ITN coverage increased from 41% in 2010 to 92% in 2011 in the study sites. IRS intervention had significant added impact on reducing vector density in 2010 but the impact was modest in 2011. The effect of IRS on reducing parasite prevalence was significant in 2011 but was seasonal specific in 2010. ITN was significantly associated with parasite densities in 2010 but IRS application was significantly correlated with reduced gametocyte density in 2011. IRS application reduced about half of the clinical malaria cases in 2010 and about one-third in 2011 compare to non-intervention areas. Conclusion Compared with a similar study conducted in 2005, the efficacy of the current integrated vector control with ITN, IRS, and Bti reduced three- to five-fold despite high ITN coverage, reflecting a modest added impact on malaria transmission. Additional strategies need to be developed to further reduce malaria transmission. PMID:23870708

  10. Discovery and Verification of Osteopontin and Beta-2-microglobulin as Promising Markers for Staging Human African Trypanosomiasis*

    PubMed Central

    Tiberti, Natalia; Hainard, Alexandre; Lejon, Veerle; Robin, Xavier; Ngoyi, Dieudonné Mumba; Turck, Natacha; Matovu, Enock; Enyaru, John; Ndung'u, Joseph Mathu; Scherl, Alexander; Dayon, Loïc; Sanchez, Jean-Charles

    2010-01-01

    Human African trypanosomiasis, or sleeping sickness, is a parasitic disease endemic in sub-Saharan Africa, transmitted to humans through the bite of a tsetse fly. The first or hemolymphatic stage of the disease is associated with presence of parasites in the bloodstream, lymphatic system, and body tissues. If patients are left untreated, parasites cross the blood-brain barrier and invade the cerebrospinal fluid and the brain parenchyma, giving rise to the second or meningoencephalitic stage. Stage determination is a crucial step in guiding the choice of treatment, as drugs used for S2 are potentially dangerous. Current staging methods, based on counting white blood cells and demonstrating trypanosomes in cerebrospinal fluid, lack specificity and/or sensitivity. In the present study, we used several proteomic strategies to discover new markers with potential for staging human African trypanosomiasis. Cerebrospinal fluid (CSF) samples were collected from patients infected with Trypanosoma brucei gambiense in the Democratic Republic of Congo. The stage was determined following the guidelines of the national control program. The proteome of the samples was analyzed by two-dimensional gel electrophoresis (n = 9), and by sixplex tandem mass tag (TMT) isobaric labeling (n = 6) quantitative mass spectrometry. Overall, 73 proteins were overexpressed in patients presenting the second stage of the disease. Two of these, osteopontin and β-2-microglobulin, were confirmed to be potential markers for staging human African trypanosomiasis (HAT) by Western blot and ELISA. The two proteins significantly discriminated between S1 and S2 patients with high sensitivity (68% and 78%, respectively) for 100% specificity, and a combination of both improved the sensitivity to 91%. The levels of osteopontin and β-2-microglobulin in CSF of S2 patients (μg/ml range), as well as the fold increased concentration in S2 compared with S1 (3.8 and 5.5 respectively) make the two markers good

  11. Preparing the United States for Zika Virus: Pre-emptive Vector Control and Personal Protection.

    PubMed

    Diaz, James H

    2016-12-01

    Discovered in 1947 in a monkey in the Zika forest of Uganda, Zika virus was dismissed as a cause of a mild illness that was confined to Africa and Southeast Asia and transmitted by Aedes mosquitoes. In 2007, Zika virus appeared outside of its endemic borders in an outbreak on the South Pacific Island of Yap. In 2013, Zika virus was associated with a major neurological complication, Guillain-Barré syndrome, in a larger outbreak in the French Polynesian Islands. From the South Pacific, Zika invaded Brazil in 2015 and caused another severe neurological complication, fetal microcephaly. The mosquito-borne transmission of Zika virus can be propagated by sexual transmission and, possibly, by blood transfusions, close personal contacts, and organ transplants, like other flaviviruses. Since these combined mechanisms of infectious disease transmission could result in catastrophic incidences of severe neurological diseases in adults and children, the public should know what to expect from Zika virus, how to prevent infection, and what the most likely failures in preventive measures will be. With federal research funding stalled, a Zika vaccine is far away. The only national strategies to prepare the United States for Zika virus invasion now are effective vector control measures and personal protection from mosquito bites. In addition to a basic knowledge of Aedes mosquito vectors and their biting behaviors, an understanding of simple household vector control measures, and the selection of the best chemical and physical mosquito repellents will be required to repel the Zika threat.

  12. A model for the control of malaria using genetically modified vectors.

    PubMed

    Diaz, H; Ramirez, A A; Olarte, A; Clavijo, C

    2011-05-07

    Recent works have considered the problem of using transgenic mosquitoes to control a malaria epidemic. These insects have been genetically engineered to reduce their capacity to infect humans with malaria parasites. We analyze a model of the mosquito population dynamics when genetically modified individuals are introduced into a wild type population so that the effect of their introduction can be assessed. The model describes the dynamics of gene selection under sexual reproduction in a closed vector population. Our results show that the fitness of the resulting heterozygous population is the key parameter for the success of the invasion, independently of the fitness of homozygous vectors. The vector population dynamics model is then combined with an epidemiological model to study the feasibility of controlling a malaria epidemic. Basic reproductive numbers are calculated for both models, and conditions are obtained for preventing reappearance of the epidemic. Simulations on this model show that it may be possible to reduce or even eradicate the epidemic only if the heterozygous population is better adapted than the wild type. They also show that this can be achieved without completely eliminating the wild type mosquitoes.

  13. [Introduction of Bacillus sphaericus strain-2362 (GRISELESF) for biological control of malaria vectors in Guatemala].

    PubMed

    Blanco Castro, S D; Martínez Arias, A; Cano Velásquez, O R; Tello Granados, R; Mendoza, I

    2000-01-01

    Malaria continues to be an important health problem in a number of countries of Central and South America where it is considered as a highly prevent endemic disease. The objective of this paper is to assess the entomo-epidemiological impact of a pilot program for the biological control of malaria-transmitting vectors, which was implemented in 1998 in Escuintla, Republic of Guatemala. This program was based on the use of 20,000 L of biolarvicide Bacillus sphaericus- strain-2362 (GRISELESF) which was applied in the 46 localities of highest epidemiological risk at a rate of 10 mL/m2 of effective area of breeding. The entomologic effectiveness of this biolarvicide was monitored from the first 72 hours to 4 months after the application. There was a total larval reduction of 94.57 in the maturity stage of the water phase of Anopheles albimanus vector. The epidemiological analysis was carried out by comparing the rate of malaria prevalence (per 1000 pop) during 1997 and 1998. The five treated municipalities showed a statistically significant reduction of 50% (p 0.01). The results obtained in this paper coincided with those reported by comparable studies, so, this allowed us to recommend the use of the biolarvicide Bacillus sphaericus (strain-2362) as part of a comprehensive program of malaria-transmitting vector control in the Republic of Guatemala and other countries of the region.

  14. Application of Lanczos vectors to control design of flexible structures, part 2

    NASA Technical Reports Server (NTRS)

    Craig, Roy R., Jr.; Su, Tzu-Jeng

    1992-01-01

    This report covers the period of the grant from January 1991 until its expiration in June 1992. Together with an Interim Report (Ref. 9), it summarizes the research conducted under NASA Grant NAG9-357 on the topic 'Application of Lanczos Vectors to Control Design of Flexible Structures.' The research concerns various ways to obtain reduced-order mathematical models of complex structures for use in dynamics analysis and in the design of control systems for these structures. This report summarizes the research.

  15. Precision vector control of a superconducting RF cavity driven by an injection locked magnetron

    DOE PAGES

    Chase, Brian; Pasquinelli, Ralph; Cullerton, Ed; ...

    2015-03-01

    The technique presented in this paper enables the regulation of both radio frequency amplitude and phase in narrow band devices such as a Superconducting RF (SRF) cavity driven by constant power output devices i.e. magnetrons [1]. The ability to use low cost high efficiency magnetrons for accelerator RF power systems, with tight vector regulation, presents a substantial cost savings in both construction and operating costs - compared to current RF power system technology. An operating CW system at 2.45 GHz has been experimentally developed. Vector control of an injection locked magnetron has been extensively tested and characterized with a SRFmore » cavity as the load. Amplitude dynamic range of 30 dB, amplitude stability of 0.3% r.m.s, and phase stability of 0.26 degrees r.m.s. has been demonstrated.« less

  16. Precision vector control of a superconducting RF cavity driven by an injection locked magnetron

    SciTech Connect

    Chase, Brian; Pasquinelli, Ralph; Cullerton, Ed; Varghese, Philip

    2015-03-01

    The technique presented in this paper enables the regulation of both radio frequency amplitude and phase in narrow band devices such as a Superconducting RF (SRF) cavity driven by constant power output devices i.e. magnetrons [1]. The ability to use low cost high efficiency magnetrons for accelerator RF power systems, with tight vector regulation, presents a substantial cost savings in both construction and operating costs - compared to current RF power system technology. An operating CW system at 2.45 GHz has been experimentally developed. Vector control of an injection locked magnetron has been extensively tested and characterized with a SRF cavity as the load. Amplitude dynamic range of 30 dB, amplitude stability of 0.3% r.m.s, and phase stability of 0.26 degrees r.m.s. has been demonstrated.

  17. Onchocerciasis Transmission in Ghana: Persistence under Different Control Strategies and the Role of the Simuliid Vectors

    PubMed Central

    Lamberton, Poppy H. L.; Cheke, Robert A.; Winskill, Peter; Tirados, Iñaki; Walker, Martin; Osei-Atweneboana, Mike Y.; Biritwum, Nana-Kwadwo; Tetteh-Kumah, Anthony; Boakye, Daniel A.; Wilson, Michael D.; Post, Rory J.; Basañez, María-Gloria

    2015-01-01

    Background The World Health Organization (WHO) aims at eliminating onchocerciasis by 2020 in selected African countries. Current control focuses on community-directed treatment with ivermectin (CDTI). In Ghana, persistent transmission has been reported despite long-term control. We present spatial and temporal patterns of onchocerciasis transmission in relation to ivermectin treatment history. Methodology/Principal Findings Host-seeking and ovipositing blackflies were collected from seven villages in four regions of Ghana with 3–24 years of CDTI at the time of sampling. A total of 16,443 flies was analysed for infection; 5,812 (35.3%) were dissected for parity (26.9% parous). Heads and thoraces of 12,196 flies were dissected for Onchocerca spp. and DNA from 11,122 abdomens was amplified using Onchocerca primers. A total of 463 larvae (0.03 larvae/fly) from 97 (0.6%) infected and 62 (0.4%) infective flies was recorded; 258 abdomens (2.3%) were positive for Onchocerca DNA. Infections (all were O. volvulus) were more likely to be detected in ovipositing flies. Transmission occurred, mostly in the wet season, at Gyankobaa and Bosomase, with transmission potentials of, respectively, 86 and 422 L3/person/month after 3 and 6 years of CDTI. The numbers of L3/1,000 parous flies at these villages were over 100 times the WHO threshold of one L3/1,000 for transmission control. Vector species influenced transmission parameters. At Asubende, the number of L3/1,000 ovipositing flies (1.4, 95% CI = 0–4) also just exceeded the threshold despite extensive vector control and 24 years of ivermectin distribution, but there were no infective larvae in host-seeking flies. Conclusions/Significance Despite repeated ivermectin treatment, evidence of O. volvulus transmission was documented in all seven villages and above the WHO threshold in two. Vector species influences transmission through biting and parous rates and vector competence, and should be included in transmission models

  18. Multiple Insecticide Resistance: An Impediment to Insecticide-Based Malaria Vector Control Program

    PubMed Central

    Steurbaut, Walter; Spanoghe, Pieter; Van Bortel, Wim; Denis, Leen; Tessema, Dejene A.; Getachew, Yehenew; Coosemans, Marc; Duchateau, Luc; Speybroeck, Niko

    2011-01-01

    Background Indoor Residual Spraying (IRS), insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) are key components in malaria prevention and control strategy. However, the development of resistance by mosquitoes to insecticides recommended for IRS and/or ITNs/LLINs would affect insecticide-based malaria vector control. We assessed the susceptibility levels of Anopheles arabiensis to insecticides used in malaria control, characterized basic mechanisms underlying resistance, and evaluated the role of public health use of insecticides in resistance selection. Methodology/Principal findings Susceptibility status of An. arabiensis was assessed using WHO bioassay tests to DDT, permethrin, deltamethrin, malathion and propoxur in Ethiopia from August to September 2009. Mosquito specimens were screened for knockdown resistance (kdr) and insensitive acetylcholinesterase (ace-1R) mutations using AS-PCR and PCR-RFLP, respectively. DDT residues level in soil from human dwellings and the surrounding environment were determined by Gas Chromatography with Electron Capture Detector. An. arabiensis was resistant to DDT, permethrin, deltamethrin and malathion, but susceptible to propoxur. The West African kdr allele was found in 280 specimens out of 284 with a frequency ranged from 95% to 100%. Ace-1R mutation was not detected in all specimens scored for the allele. Moreover, DDT residues were found in soil samples from human dwellings but not in the surrounding environment. Conclusion The observed multiple-resistance coupled with the occurrence of high kdr frequency in populations of An. arabiensis could profoundly affect the malaria vector control programme in Ethiopia. This needs an urgent call for implementing rational resistance management strategies and integrated vector control intervention. PMID:21264325

  19. The role of vector control in stopping the transmission of malaria: threats and opportunities.

    PubMed

    Hemingway, Janet

    2014-01-01

    Malaria control, and that of other insect borne diseases such as dengue, is heavily dependent on our ability to control the mosquito populations that transmit these diseases. The major push over the last decade to reduce the global burden of malaria has been driven by the distribution of pyrethroid insecticide-treated bednets and an increase in coverage of indoor residual spraying (IRS). This has reduced malaria deaths by a third. Progress towards the goal of reducing this further is threatened by lack of funding and the selection of drug and insecticide resistance. When malaria control was initially scaled up, there was little pyrethroid resistance in the major vectors, today there is no country in Africa where the vectors remain fully susceptible to pyrethroids. The first pyrethroid resistance mechanisms to be selected produced low-level resistance which had little or no operational significance. More recently, metabolically based resistance has been selected, primarily in West Africa, which in some mosquito populations produces more than 1000-fold resistance. As this spreads the effectiveness of pyrethroid-based bednets and IRS will be compromised. New public health insecticides are not readily available. The pipeline of agrochemical insecticides that can be re-purposed for public health dried up 30 years ago when the target product profile for agricultural insecticides shifted from broad spectrum, stable, contact-acting insecticides to narrow spectrum stomach poisons that could be delivered through the plant. A public-private partnership, the Innovative Vector Control Consortium, was established in 2005 to stimulate the development of new public health pesticides. Nine potential new classes of chemistry are in the pipeline, with the intention of developing three into new insecticides. While this has been successfully achieved, it will still take 6-9 years for new insecticides to reach the market. Careful management of the resistance situation in the interim

  20. Control of the Aedes vectors of the dengue viruses and Wuchereria bancrofti: the French Polynesian experience.

    PubMed

    Lardeux, F; Rivière, F; Séchan, Y; Loncke, S

    2002-12-01

    In most of the 130 islands of French Polynesia, the stenotopic mosquitoes Aedes aegypti (the main local vector for the viruses causing dengue) and Aedes polynesiensis (the main local vector of Wuchereria bancrofti) share many breeding sites in water containers such as discarded cans, coconut shells, buckets and water-storage pots and drums. In addition to selective application of insecticides, non-polluting methods of controlling these mosquitoes have been evaluated during the last decade in two main ecological situations: (1) villages, where Aedes breeding sites are typically peridomestic; and (2) flooded burrows of land crabs, the major source of Ae. polynesiensis throughout the South Pacific region. Large-scale trials of biological control agents, such as mosquito fish (Gambusia affinis and Poecilia reticulata) and copepods (Mesocyclops aspericornis), and of integrated-control strategies have demonstrated the efficacy of certain techniques and control agents against the target Aedes populations in some village situations. Generally, mechanical methods (the use of layers of polystyrene beads against mosquito larvae and pupae, and screening against adult mosquitoes) were more efficient than use of the biological control agents. By integrating several methods of control, mosquito densities (as measured by human-bait collections and larval surveys) were reduced significantly compared with the results of concurrent sampling from untreated villages, and control remained effective for months after the interventions ceased. In land-crab burrows, the first attempts to control Aedes larvae used bacterial agents (Bacillus thuringiensis) and predatory copepods gave disappointing results. Mesocyclops aspericornis could be an effective control agent if the burrows were constantly flooded, but most burrows dry out and refill periodically, so copepod populations do not survive. As it proved difficult to reach all corners of the long sinuous burrows with any control agent

  1. Universal Parameter Measurement and Sensorless Vector Control of Induction and Permanent Magnet Synchronous Motors

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shu; Ara, Takahiro

    Recently, induction motors (IMs) and permanent-magnet synchronous motors (PMSMs) have been used in various industrial drive systems. The features of the hardware device used for controlling the adjustable-speed drive in these motors are almost identical. Despite this, different techniques are generally used for parameter measurement and speed-sensorless control of these motors. If the same technique can be used for parameter measurement and sensorless control, a highly versatile adjustable-speed-drive system can be realized. In this paper, the authors describe a new universal sensorless control technique for both IMs and PMSMs (including salient pole and nonsalient pole machines). A mathematical model applicable for IMs and PMSMs is discussed. Using this model, the authors derive the proposed universal sensorless vector control algorithm on the basis of estimation of the stator flux linkage vector. All the electrical motor parameters are determined by a unified test procedure. The proposed method is implemented on three test machines. The actual driving test results demonstrate the validity of the proposed method.

  2. [Adenosine deaminase in experimental trypanosomiasis: future implications].

    PubMed

    Pérez-Aguilar, Mary Carmen; Rondón-Mercado, Rocío

    2015-09-01

    The adenosine deaminase represents a control point in the regulation of extracellular adenosine levels, thus playing a critical role in the modulation of purinergic responses to certain pathophysiological events. Several studies have shown that serum and plasma enzyme levels are elevated in some diseases caused by microorganisms, which may represent a compensatory mechanism due to the elevated levels of adenosine and the release of inflammatory mediators. Recent research indicates that adenosine deaminase activity decreases and affects hematological parameters of infected animals with Trypanosoma evansi, so that such alterations could have implications in the pathogenesis of the disease. In addition, the enzyme has been detected in this parasite; allowing the inference that it could be associated with the vital functions of the same, similar to what occurs in mammals. This knowledge may be useful in the association of chemotherapy with specific inhibitors of the enzyme in future studies.

  3. Circadian entrainment by light and host in the Chagas disease vector, Triatoma infestans.

    PubMed

    Valentinuzzi, Verónica Sandra; Amelotti, Ivana; Gorla, David Eladio; Catalá, Silvia Susana; Ralph, Martin Roland

    2014-03-01

    Triatoma infestans (Reduviidae: Triatominae, "kissing bug") is the main insect vector of Trypanosoma cruzi, the causative agent of Chagas disease, a chronic trypanosomiasis infecting 10 million people world-wide. This hematophagous bug feeds on diurnal and nocturnal species during each host's quiescent time. As the hosts are also its major predators, kissing bugs are subjected to dual selective pressures from a single source. Therefore, synchronization of feeding with the host's behavior is critical to the insects' survival. We show that nonphotic signals linked to the host eclipse the role of light and dark as the primary circadian zeitgeber for these bugs, although light still strongly inhibits locomotor behavior directly. In nature, this combination provides the insect with great flexibility in organizing physiology and behavior: anticipating a quiescent host or avoiding its potential predation while remaining directly responsive to immediate environmental conditions. Manipulation of nonphotic entrainment could be a useful chronobiotic tool in the control of Chagas disease.

  4. A model framework to estimate impact and cost of genetics-based sterile insect methods for dengue vector control.

    PubMed

    Alphey, Nina; Alphey, Luke; Bonsall, Michael B

    2011-01-01

    Vector-borne diseases impose enormous health and economic burdens and additional methods to control vector populations are clearly needed. The Sterile Insect Technique (SIT) has been successful against agricultural pests, but is not in large-scale use for suppressing or eliminating mosquito populations. Genetic RIDL technology (Release of Insects carrying a Dominant Lethal) is a proposed modification that involves releasing insects that are homozygous for a repressible dominant lethal genetic construct rather than being sterilized by irradiation, and could potentially overcome some technical difficulties with the conventional SIT technology. Using the arboviral disease dengue as an example, we combine vector population dynamics and epidemiological models to explore the effect of a program of RIDL releases on disease transmission. We use these to derive a preliminary estimate of the potential cost-effectiveness of vector control by applying estimates of the costs of SIT. We predict that this genetic control strategy could eliminate dengue rapidly from a human community, and at lower expense (approximately US$ 2~30 per case averted) than the direct and indirect costs of disease (mean US$ 86-190 per case of dengue). The theoretical framework has wider potential use; by appropriately adapting or replacing each component of the framework (entomological, epidemiological, vector control bio-economics and health economics), it could be applied to other vector-borne diseases or vector control strategies and extended to include other health interventions.

  5. Developing an evidence-based decision support system for rational insecticide choice in the control of African malaria vectors.

    PubMed

    Coleman, Michael; Sharp, Brian; Seocharan, Ishen; Hemingway, Janet

    2006-07-01

    The emergence of Anopheles species resistant to insecticides widely used in vector control has the potential to impact directly on the control of malaria. This may have a particularly dramatic effect in Africa, where pyrethroids impregnated onto bed-nets are the dominant insecticides used for vector control. Because the same insecticides are used for crop pests, the extensive use and misuse of insecticides for agriculture has contributed to the resistance problem in some vectors. The potential for resistance to develop in African vectors has been apparent since the 1950s, but the scale of the problem has been poorly documented. A geographical information system-based decision support system for malaria control has recently been established in Africa and used operationally in Mozambique. The system incorporates climate data and disease transmission rates, but to date it has not incorporated spatial or temporal data on vector abundance or insecticide resistance. As a first step in incorporating this information, available published data on insecticide resistance in Africa has now been collated and incorporated into this decision support system. Data also are incorporated onto the openly available Mapping Malaria Risk in Africa (MARA) Web site (http://www.mara.org.za). New data, from a range of vector population-monitoring initiatives, can now be incorporated into this open access database to allow a spatial understanding of resistance distribution and its potential impact on disease transmission to benefit vector control programs.

  6. Operational efficiency and sustainability of vector control of malaria and dengue: descriptive case studies from the Philippines

    PubMed Central

    2012-01-01

    Background Analysis is lacking on the management of vector control systems in disease-endemic countries with respect to the efficiency and sustainability of operations. Methods Three locations were selected, at the scale of province, municipality and barangay (i.e. village). Data on disease incidence, programme activities, and programme management were collected on-site through meetings and focus group discussions. Results Adaptation of disease control strategies to the epidemiological situation per barangay, through micro-stratification, brings gains in efficiency, but should be accompanied by further capacity building on local situational analysis for better selection and targeting of vector control interventions within the barangay. An integrated approach to vector control, aiming to improve the rational use of resources, was evident with a multi-disease strategy for detection and response, and by the use of combinations of vector control methods. Collaboration within the health sector was apparent from the involvement of barangay health workers, re-orientation of job descriptions and the creation of a disease surveillance unit. The engagement of barangay leaders and use of existing community structures helped mobilize local resources and voluntary services for vector control. In one location, local authorities and the community were involved in the planning, implementation and evaluation of malaria control, which triggered local programme ownership. Conclusions Strategies that contributed to an improved efficiency and sustainability of vector control operations were: micro-stratification, integration of vector control within the health sector, a multi-disease approach, involvement of local authorities, and empowerment of communities. Capacity building on situational analysis and vector surveillance should be addressed through national policy and guidelines. PMID:22873707

  7. Seroprevalence of CANINE LEISHMANIASIS AND American trypanosomiasis in dogs from Grenada, West Indies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Canine leishmaniasis and American trypanosomiasis (AT) are caused by related hemoflagellated parasites, Leishmania spp. and Trypanosoma cruzi, which share several common host species. Dogs are reservoirs for human infections with both pathogens. We determined the prevalence of antibodies to Leishman...

  8. Aedes aegypti Control Through Modernized, Integrated Vector Management

    PubMed Central

    Yakob, Laith; Funk, Sebastian; Camacho, Anton; Brady, Oliver; Edmunds, W. John

    2017-01-01

    Introduction: In the context of the ongoing, unprecedented Zika virus outbreak in the Americas, the World Health Organization has expressed its support for developing and up-scaling three novel approaches to controlling the Aedes aegypti mosquito: the Sterile Insect Technique (SIT), the Release of Insects carrying Dominant Lethal genes (RIDL) and the release of Wolbachia-infected mosquitoes. Whereas the former two approaches are temporary insect population suppression strategies, Wolbachia infection is a self-sustaining, invasive strategy that uses inherited endosymbiotic bacteria to render natural mosquito populations arbovirus resistant. Methods: A mathematical model is parameterised with new, Brazilian field data informing the mating competitiveness of mass-reared, released insects; and simulations compare and contrast projections of vector control achieved with the alternative approaches. Results: Important disadvantages of Wolbachia and SIT are identified: both strategies result in mosquitoes ovipositing non-viable eggs and, by alleviating intense larval competition, can cause an overall increase in survival to the adult stage. However, it is demonstrated that strategically combining the suppression methods with Wolbachia can generate a sustained control while mitigating the risks of inadvertent exacerbation of the wild mosquito population. Discussion: This initial analysis demonstrates potential for good synergy when combining novel mosquito approaches in a modernized, integrated vector control programme. PMID:28286698

  9. A Gyroless Safehold Control Law Using Angular Momentum as an Inertial Reference Vector

    NASA Technical Reports Server (NTRS)

    Stoneking, Eric; Lebsock, Ken

    2008-01-01

    A novel safehold control law was developed for the nadir-pointing Vegetation Canopy Lidar (VCL) spacecraft, necessitated by a challenging combination of constraints. The instrument optics did not have a recloseable cover to protect them form potentially catastrophic damage if they were exposed to direct sunlight. The baseline safehold control law relied on a single-string inertial reference unit. A gyroless safehold law was developed to give a degree of robustness to gyro failures. Typical safehold solutions were not viable; thermal constraints made spin stabilization unsuitable, and an inertial hold based solely on magnetometer measurements wandered unaceptably during eclipse. The novel approach presented here maintains a momentum bias vector not for gyroscopic stiffness, but to use as an inertial reference direction during eclipse. The control law design is presented. The effect on stability of the rank-deficiency of magnetometer-based rate derivation is assessed. The control law's performance is evaluated by simulation.

  10. A Gyroless Safehold Control Law using Angular Momentum as an Inertial Reference Vector

    NASA Technical Reports Server (NTRS)

    Stoneking, Eric; Lebsock, Ken

    2008-01-01

    A novel safehold control law was developed for the nadir-pointing Vegetation Canopy Lidar (VCL) spacecraft, necessitated by a challenging combination of constraints. The instrument optics did not have a reclosable cover to protect them from potentially catastrophic damage if they were exposed to direct sunlight. The baseline safehold control law relied on a single-string inertial reference unit. A gyroless safehold law was developed to give a degree of rebustness to gyro failures. Typical safehold solutions were not viable; thermal constraints made spin stabilization unsuitable, and an inertial hold based solely on magnetometer measurements wandered unacceptably during eclipse. The novel approach presented here maintains a momentum bias vector not for gyroscopic stiffness, but to use as an inertial reference direction during eclipse. The control law design is presented. The effect on stability of the rate-deficiency of magnetometer-based rate derivation is assessed. The control law's performance is evaluated by simulation.

  11. Vector population manipulation for control of arboviruses--a novel prospect for India.

    PubMed

    Niranjan Reddy, Bp; Gupta, Bhavna; Rao, B Prasad

    2014-04-01

    India, the seventh largest country in the world, has diverse geographical and climatic regions with vast rural and peri-urban areas. Many are experiencing an escalation in the spread and intensity of numerous human diseases transmitted by insects. Classically, the management of these vector-borne diseases is underpinned by either chemical insecticides and/or environmental management targeted at the vector. However, these methods or their present implementation do not offer acceptable levels of control, and more effective and sustainable options are now available. Genetic strategies for the prevention of arbovirus transmission are most advanced for dengue and chikungunya, targeting their primary vector, Aedes aegypti. The national burden in terms of morbidity and mortality as a direct consequence of dengue virus in India is considered to be the largest worldwide, over 4 times that of any other country. Presently, new genetic technologies are undergoing field evaluation of their biosafety and efficacy in several countries. This paper discusses the merits of these approaches and argues for fair and transparent appraisal in India as a matter of urgency. Identification of any associated risks and their appropriate mitigation are fundamental to that process.

  12. Surface functionalization of silver nanoparticles: novel applications for insect vector control.

    PubMed

    Sooresh, Aishwarya; Kwon, Hyeogsun; Taylor, Robert; Pietrantonio, Patricia; Pine, Michelle; Sayes, Christie M

    2011-10-01

    Every day, people and animals contract debilitating and life threatening diseases due to bites from infected flies, ticks, and mosquitoes. The current methods utilized to fight against these diseases are only partially effective or safe for humans and animals. When it comes to insect vector control, a conceptual paradigm shift is urgently needed. This work proposes a novel synthetic scheme to produce a nanoparticle-pesticide core-shell conjugate to be used as an active agent against arthropod vectors, such as mosquitoes. As a proof of concept, we conjugated nanosilver to the pyrethroid pesticide deltamethrin. First, electron microscopy and Fourier transform infrared spectroscopy verified the presence of a 15 nm nanosilver core surrounded by deltamethrin. Second, when the conjugate was exposed to mosquitoes for a 24 h bioassay, mortality was observed at 9 × 10(-4) M. Silver was detected in the hemolymph of mosquitoes exposed to the conjugate. We concluded that the newly developed nanoconjugate did not inactivate the primary function of the pesticide and was effective in killing mosquitoes at low concentrations. These results demonstrate the potential to use nanoparticle surfaces to kill insects, specifically vectors of human pathogens.

  13. [Aedes albopictus, vector of chikungunya and dengue viruses in Reunion Island: biology and control].

    PubMed

    Delatte, H; Paupy, C; Dehecq, J S; Thiria, J; Failloux, A B; Fontenille, D

    2008-03-01

    Chikungunya virus (CHIKV) and dengue virus (DENV) are mosquito-borne viruses transmitted by the Aedes genus. Dengue is considered as the most important arbovirus disease throughout the World. Chikungunya, known from epidemics in continental Africa and Asia, has up to now been poorly studied. It has been recently responsible for the severe 2004-2007 epidemic reported in the Indian Ocean (IO), which has caused several serious health and economic problems. This unprecedented epidemic of the IO has shown severe health troubles with morbidity and death associated, which had never been observed before. The two major vectors of those arboviruses in the IO area are Aedes aegypti and Aedes albopictus. The latest is considered as the main vector in most of the islands of the area, especially in Reunion Island. Ae. albopictus showed strong ecological plasticity. Small disposable containers were the principal urban breeding sites, and preferred natural developmental sites were bamboo stumps and rock holes in peri-urban and gully areas. The virus has been isolated from field collected Ae. albopictus females, and in two out of 500 pools of larvae, demonstrating vertical transmission. Experimental works showed that both Ae. albopictus and Ae. aegypti from west IO islands are efficient vectors of dengue and chikungunya viruses. Since 2006 and all along the epidemic of CHIKV, measures for the control of larvae (temephos then Bacillus thuringiensis) and adults (fenitrothion, then deltamethrine) of Ae. albopictus where applied along with individual and collective actions (by the use of repellents, and removal of breeding sites around houses) in Reunion Island. In order to prevent such epidemics, a preventive plan for arboviruses upsurge is ongoing processed. This plan would allow a quicker response to the threat and adapt it according to the virus and its specific vector.

  14. Community-Effectiveness of Temephos for Dengue Vector Control: A Systematic Literature Review

    PubMed Central

    George, Leyanna; Lenhart, Audrey; Toledo, Joao; Lazaro, Adhara; Han, Wai Wai; Velayudhan, Raman; Runge Ranzinger, Silvia; Horstick, Olaf

    2015-01-01

    The application of the organophosphate larvicide temephos to water storage containers is one of the most commonly employed dengue vector control methods. This systematic literature review is to the knowledge of the authors the first that aims to assess the community-effectiveness of temephos in controlling both vectors and dengue transmission when delivered either as a single intervention or in combination with other interventions. A comprehensive literature search of 6 databases was performed (PubMed, WHOLIS, GIFT, CDSR, EMBASE, Wiley), grey literature and cross references were also screened for relevant studies. Data were extracted and methodological quality of the studies was assessed independently by two reviewers. 27 studies were included in this systematic review (11 single intervention studies and 16 combined intervention studies). All 11 single intervention studies showed consistently that using temephos led to a reduction in entomological indices. Although 11 of the 16 combined intervention studies showed that temephos application together with other chemical vector control methods also reduced entomological indices, this was either not sustained over time or–as in the five remaining studies—failed to reduce the immature stages. The community-effectiveness of temephos was found to be dependent on factors such as quality of delivery, water turnover rate, type of water, and environmental factors such as organic debris, temperature and exposure to sunlight. Timing of temephos deployment and its need for reapplication, along with behavioural factors such as the reluctance of its application to drinking water, and operational aspects such as cost, supplies, time and labour were further limitations identified in this review. In conclusion, when applied as a single intervention, temephos was found to be effective at suppressing entomological indices, however, the same effect has not been observed when temephos was applied in combination with other

  15. Oviposition Site Selection by the Dengue Vector Aedes aegypti and Its Implications for Dengue Control

    PubMed Central

    Wong, Jacklyn; Stoddard, Steven T.; Astete, Helvio; Morrison, Amy C.; Scott, Thomas W.

    2011-01-01

    Background Because no dengue vaccine or antiviral therapy is commercially available, controlling the primary mosquito vector, Aedes aegypti, is currently the only means to prevent dengue outbreaks. Traditional models of Ae. aegypti assume that population dynamics are regulated by density-dependent larval competition for food and little affected by oviposition behavior. Due to direct impacts on offspring survival and development, however, mosquito choice in oviposition site can have important consequences for population regulation that should be taken into account when designing vector control programs. Methodology/Principal Findings We examined oviposition patterns by Ae. aegypti among 591 naturally occurring containers and a set of experimental containers in Iquitos, Peru. Using larval starvation bioassays as an indirect measure of container food content, we assessed whether females select containers with the most food for their offspring. Our data indicate that choice of egg-laying site is influenced by conspecific larvae and pupae, container fill method, container size, lid, and sun exposure. Although larval food positively influenced oviposition, our results did not support the hypothesis that females act primarily to maximize food for larvae. Females were most strongly attracted to sites containing immature conspecifics, even when potential competitors for their progeny were present in abundance. Conclusion/Significance Due to strong conspecific attraction, egg-laying behavior may contribute more to regulating Ae. aegypti populations than previously thought. If highly infested containers are targeted for removal or larvicide application, females that would have preferentially oviposited in those sites may instead distribute their eggs among other suitable, previously unoccupied containers. Strategies that kill mosquitoes late in their development (i.e., insect growth regulators that kill pupae rather than larvae) will enhance vector control by creating

  16. Drug discovery and human African trypanosomiasis: a disease less neglected?

    PubMed

    Ferrins, Lori; Rahmani, Raphaël; Baell, Jonathan B

    2013-10-01

    Human African trypanosomiasis (HAT) has been neglected for a long time. The most recent drug to treat this disease, eflornithine, was approved by the US FDA in 2000. Current treatments exhibit numerous problematic side effects and are often ineffective against the debilitating CNS resident stage of the disease. Fortunately, several partnerships and initiatives have been formed over the last 20 years in an effort to eradicate HAT, along with a number of other neglected diseases. This has led to an increasing number of foundations and research institutions that are currently working on the development of new drugs for HAT and tools with which to diagnose and treat patients. New biochemical pathways as therapeutic targets are emerging, accompanied by increasing numbers of new antitrypanosomal compound classes. The future looks promising that this collaborative approach will facilitate eagerly awaited breakthroughs in the treatment of HAT.

  17. Is Dengue Vector Control Deficient in Effectiveness or Evidence?: Systematic Review and Meta-analysis

    PubMed Central

    Bowman, Leigh R.; Donegan, Sarah; McCall, Philip J.

    2016-01-01

    Background Although a vaccine could be available as early as 2016, vector control remains the primary approach used to prevent dengue, the most common and widespread arbovirus of humans worldwide. We reviewed the evidence for effectiveness of vector control methods in reducing its transmission. Methodology/Principal Findings Studies of any design published since 1980 were included if they evaluated method(s) targeting Aedes aegypti or Ae. albopictus for at least 3 months. Primary outcome was dengue incidence. Following Cochrane and PRISMA Group guidelines, database searches yielded 960 reports, and 41 were eligible for inclusion, with 19 providing data for meta-analysis. Study duration ranged from 5 months to 10 years. Studies evaluating multiple tools/approaches (23 records) were more common than single methods, while environmental management was the most common method (19 studies). Only 9/41 reports were randomized controlled trials (RCTs). Two out of 19 studies evaluating dengue incidence were RCTs, and neither reported any statistically significant impact. No RCTs evaluated effectiveness of insecticide space-spraying (fogging) against dengue. Based on meta-analyses, house screening significantly reduced dengue risk, OR 0.22 (95% CI 0.05–0.93, p = 0.04), as did combining community-based environmental management and water container covers, OR 0.22 (95% CI 0.15–0.32, p<0.0001). Indoor residual spraying (IRS) did not impact significantly on infection risk (OR 0.67; 95% CI 0.22–2.11; p = 0.50). Skin repellents, insecticide-treated bed nets or traps had no effect (p>0.5), but insecticide aerosols (OR 2.03; 95% CI 1.44–2.86) and mosquito coils (OR 1.44; 95% CI 1.09–1.91) were associated with higher dengue risk (p = 0.01). Although 23/41 studies examined the impact of insecticide-based tools, only 9 evaluated the insecticide susceptibility status of the target vector population during the study. Conclusions/Significance This review and meta

  18. Nanobody conjugated PLGA nanoparticles for active targeting of African Trypanosomiasis.

    PubMed

    Arias, José L; Unciti-Broceta, Juan D; Maceira, José; Del Castillo, Teresa; Hernández-Quero, José; Magez, Stefan; Soriano, Miguel; García-Salcedo, José A

    2015-01-10

    Targeted delivery of therapeutics is an alternative approach for the selective treatment of infectious diseases. The surface of African trypanosomes, the causative agents of African trypanosomiasis, is covered by a surface coat consisting of a single variant surface glycoprotein, termed VSG. This coat is recycled by endocytosis at a very high speed, making the trypanosome surface an excellent target for the delivery of trypanocidal drugs. Here, we report the design of a drug nanocarrier based on poly ethylen glycol (PEG) covalently attached (PEGylated) to poly(D,L-lactide-co-glycolide acid) (PLGA) to generate PEGylated PLGA nanoparticles. This nanocarrier was coupled to a single domain heavy chain antibody fragment (nanobody) that specifically recognizes the surface of the protozoan pathogen Trypanosoma brucei. Nanoparticles were loaded with pentamidine, the first-line drug for T. b. gambiense acute infection. An in vitro effectiveness assay showed a 7-fold decrease in the half-inhibitory concentration (IC50) of the formulation relative to free drug. Furthermore, in vivo therapy using a murine model of African trypanosomiasis demonstrated that the formulation cured all infected mice at a 10-fold lower dose than the minimal full curative dose of free pentamidine and 60% of mice at a 100-fold lower dose. This nanocarrier has been designed with components approved for use in humans and loaded with a drug that is currently in use to treat the disease. Moreover, this flexible nanobody-based system can be adapted to load any compound, opening a range of new potential therapies with application to other diseases.

  19. Evaluation of novel insecticides for control of dengue vector Aedes aegypti (Diptera: Culicidae).

    PubMed

    Paul, Ayesa; Harrington, Laura C; Scott, Jeffrey G

    2006-01-01

    Insecticides are one of the major tools for controlling vector populations and for reducing the transmission of human pathogens. However, there are few new insecticides being developed and marketed for vector control. Herein, we report on the toxicity of six novel insecticides to both adult and larval Aedes aegypti (L). and the toxicity of three novel insect growth regulators (IGRs) to larvae. Four insecticides were highly or moderately toxic to larvae with LC50 values of 16 (chlorfenapyr), 70 (hydramethylnon), 79 (indoxacarb), and 84 ng/ml (imidacloprid). Diafenthiuron and chlorfenapyr were moderately toxic to adult mosquitoes with LC50 values of 13 and 92 ng/cm2, respectively. Imidacloprid was strongly synergized by piperonyl butoxide (PBO) in Ae. aegypti adults, suggesting that neonicotinoids are intrinsically very toxic to adult mosquitoes (in the absence of detoxification). The effect of PBO on the toxicity in adults and larvae was considerably different, both in terms of the insecticides that were synergized (or antagonized for chlorfenapyr versus adults) and in terms of the degree of synergism. This result implies that the cytochrome P450s involved in metabolism of these insecticides are different between adults and larvae. Pyriproxyfen was confirmed as a potent IGR (EC50 of 0.0017 ng/ml) for mosquitoes, although tebufenozide lacked activity. The potential for use of these materials in mosquito control is discussed.

  20. Anticipatory Monitoring and Control of Complex Systems using a Fuzzy based Fusion of Support Vector Regressors

    SciTech Connect

    Miltiadis Alamaniotis; Vivek Agarwal

    2014-10-01

    This paper places itself in the realm of anticipatory systems and envisions monitoring and control methods being capable of making predictions over system critical parameters. Anticipatory systems allow intelligent control of complex systems by predicting their future state. In the current work, an intelligent model aimed at implementing anticipatory monitoring and control in energy industry is presented and tested. More particularly, a set of support vector regressors (SVRs) are trained using both historical and observed data. The trained SVRs are used to predict the future value of the system based on current operational system parameter. The predicted values are then inputted to a fuzzy logic based module where the values are fused to obtain a single value, i.e., final system output prediction. The methodology is tested on real turbine degradation datasets. The outcome of the approach presented in this paper highlights the superiority over single support vector regressors. In addition, it is shown that appropriate selection of fuzzy sets and fuzzy rules plays an important role in improving system performance.

  1. Independent Orbiter Assessment (IOA): Analysis of the ascent thrust vector control actuator subsystem

    NASA Technical Reports Server (NTRS)

    Wilson, R. E.; Riccio, J. R.

    1986-01-01

    The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Ascent Thrust Vector Control (ATVC) Actuator hardware are documented. The function of the Ascent Thrust Vector Control Actuators (ATVC) is to gimbal the main engines to provide for attitude and flight path control during ascent. During first stage flight, the SRB nozzles provide nearly all the steering. After SRB separation, the Orbiter is steered by gimbaling of its main engines. There are six electrohydraulic servoactuators, one pitch and one yaw for each of the three main engines. Each servoactuator is composed of four electrohydraulic servovalve assemblies, one second stage power spool valve assembly, one primary piston assembly and a switching valve. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Critical failures resulting in loss of ATVC were mainly due to loss of hydraulic fluid, fluid contamination and mechanical failures.

  2. Lentiviral vector system for coordinated constitutive and drug controlled tetracycline-regulated gene co-expression.

    PubMed

    Stahlhut, Maike; Schwarzer, Adrian; Eder, Matthias; Yang, Min; Li, Zhixiong; Morgan, Michael; Schambach, Axel; Kustikova, Olga S

    2015-09-01

    Constitutive co-expression of cooperating transgenes using retroviral integrating vectors is frequently used for genetic modification of different cell types to establish therapeutic or cancer models. However, such approaches are unable to dissect the influence of dose, order and reversibility of transgene expression on the fate of newly developed therapeutic/malignant phenotypes. We present a modular lentiviral vector system, which provides expression of constitutive and inducible components. To demonstrate its functionality, we constitutively expressed the well-described transcription factor Meis1 followed by inducible co-expression of collaborating partner Hoxa9 under the control of tetracycline responsive promoters in murine fibroblasts and primary hematopoietic progenitor cells (HPCs). Fluorescent markers to track transgene co-expression revealed tightly controlled, efficiently inducible and reversible but cell type dependent gene transfer over time. We demonstrated dose-dependent blockade of myeloid differentiation when both Meis1/Hoxa9 were concomitantly overexpressed in primary HPCs in vitro, but the absence of the transformed phenotype in non-induced samples or when Hoxa9 expression was down-regulated. This system combines the advantages of lentiviral gene transfer and the opportunity for drug-controlled co-expression of multiple transgenes to dissect, among others, gene networks governing complex cell behavior, such as proto-oncogene dose-dependent leukemogenic pathways or collaborating mechanisms of genes enhancing competitive fitness of hematopoietic cells.

  3. Development of a New Chemotherapy for Human African Trypanosomiasis by Using an Animal Model: Suramin with DL-Alpha-Difluoromethylornithine

    DTIC Science & Technology

    1989-09-14

    AD-A237 230_ DEVELOPMENT OF A NEW CHEMOTHERAPY FOR HUMAN AFRICAN TRYPANOSOMIASIS BY USING AN ANIMAL MODEL: SURAMIN WITH DL..DIFLUOROMETHYLORNITHINE... Chemotherapy for African trypanosomiasis by polyamine biosynthesis inhibition.) FINAL PROGRESS REPORT Allen B. Clarkson, Jr., Ph.D. September 14, 1989...AF 061 11. TITLE (include Security Classification) "Development of a New Chemotherapy for Human African Trypanosomiasis by Using an Animal Model

  4. Development of a New Chemotherapy for Human African Trypanosomiasis by Using an Animal Model: Suramin with DL-Alpha-Difluoromethylornithine

    DTIC Science & Technology

    1989-09-14

    AD-A2 3 7 231 AD ______________ DEVELOPMENT OF A NEW CHEMOTHERAPY FOR HUMAN AFRICAN TRYPANOSOMIASIS BY USING AN ANIMAL MODEL: SURAMIN WITH DL...DIFLUOROMETHYLORNITHINE ( Chemotherapy for African trypanosomiasis by polyamine biosynthesis inhibition.) ANNUAL PROGRESS REPORT -- YEAR TWO Allen B... Chemotherapy for Human African Trypanosomiasis by Using an Animal Model: Suramin with DL- a- Difluoromethylornithine" 12. PERSONAL AUTHOR(S) Clarkson, Allen

  5. Vector Liapunov Function Approach to Longitudinal Control of Vehicles in a Platoon

    NASA Astrophysics Data System (ADS)

    Zhang, Jiye; Suda, Yoshihiro; Iwasa, Takashi; Komine, Hisanao

    An important aspect of an automated highway system design is the synthesis of an automated vehicle following system. Associated with automated vehicle following system is the problem of the stability of a string of vehicle, i.e., the problem of spacing error propagation, and in some cases, amplification upstream from one vehicle to another, due to some disturbance at the head of the string. In this paper, the novel method to determine the stability of a string of vehicle is established based on the vector Liapunov method. Based on the new results for the stability of string of vehicle, the controller is constructed by sliding mode control method. The stability domain of the controller parameters of the string of vehicles is enlarged.

  6. Advances in biological control in relation to vectors of human diseases

    PubMed Central

    Weiser, J.

    1963-01-01

    In recent years, increased knowledge of insect pathology and ecology and the development of insecticide-resistance have led to a revival of interest in biological methods of controlling insects that carry human diseases. The author of this paper reviews the information at present available with regard to the various pathogens, predators and parasites of insect vectors of human disease—cockroaches, lice, bugs, fleas, mosquitos, flies and ticks—and suggests lines of future research that might prove profitable. In this connexion he stresses that only a world-wide investigation of the diseases of medically important insects will yield data on which a balanced biological research programme can be based—a programme leading to the development of practicable control procedures and their integration with chemical and other methods of control. PMID:20604158

  7. Spatial predictions of Rhodesian Human African Trypanosomiasis (sleeping sickness) prevalence in Kaberamaido and Dokolo, two newly affected districts of Uganda.

    PubMed

    Batchelor, Nicola A; Atkinson, Peter M; Gething, Peter W; Picozzi, Kim; Fèvre, Eric M; Kakembo, Abbas S L; Welburn, Susan C

    2009-12-15

    The continued northwards spread of Rhodesian sleeping sickness or Human African Trypanosomiasis (HAT) within Uganda is raising concerns of overlap with the Gambian form of the disease. Disease convergence would result in compromised diagnosis and treatment for HAT. Spatial determinants for HAT are poorly understood across small areas. This study examines the relationships between Rhodesian HAT and several environmental, climatic and social factors in two newly affected districts, Kaberamaido and Dokolo. A one-step logistic regression analysis of HAT prevalence and a two-step logistic regression method permitted separate analysis of both HAT occurrence and HAT prevalence. Both the occurrence and prevalence of HAT were negatively correlated with distance to the closest livestock market in all models. The significance of distance to the closest livestock market strongly indicates that HAT may have been introduced to this previously unaffected area via the movement of infected, untreated livestock from endemic areas. This illustrates the importance of the animal reservoir in disease transmission, and highlights the need for trypanosomiasis control in livestock and the stringent implementation of regulations requiring the treatment of cattle prior to sale at livestock markets to prevent any further spread of Rhodesian HAT within Uganda.

  8. Combining Attractants and Larvicides in Biodegradable Matrices for Sustainable Mosquito Vector Control

    PubMed Central

    Schorkopf, Dirk Louis P.; Spanoudis, Christos G.; Mboera, Leonard E. G.; Mafra-Neto, Agenor; Ignell, Rickard; Dekker, Teun

    2016-01-01

    Background There is a global need for cost-effective and environmentally friendly tools for control of mosquitoes and mosquito-borne diseases. One potential way to achieve this is to combine already available tools to gain synergistic effects to reduce vector mosquito populations. Another possible way to improve mosquito control is to extend the active period of a given control agent, enabling less frequent applications and consequently, more efficient and longer lasting vector population suppression. Methodology/principal findings We investigated the potential of biodegradable wax emulsions to improve the performance of semiochemical attractants for gravid female culicine vectors of disease, as well as to achieve more effective control of their aquatic larval offspring. As an attractant for gravid females, we selected acetoxy hexadecanolide (AHD), the Culex oviposition pheromone. As toxicant for mosquito larvae, we chose the biological larvicides Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus (Bs). These attractant and larvicidal agents were incorporated, separately and in combination, into a biodegradable wax emulsion, a commercially available product called SPLAT (Specialized Pheromone & Lure Application Technology) and SPLATbac, which contains 8.33% Bti and 8.33% Bs. Wax emulsions were applied to water surfaces as buoyant pellets of 20 mg each. Dose-mortality analyses of Culex quinquefasciatus Say larvae demonstrated that a single 20 mg pellet of a 10−1 dilution of SPLATbac in a larval tray containing 1 L of water caused 100% mortality of neonate (1st instar) larvae for at least five weeks after application. Mortality of 3rd instar larvae remained equally high with SPLATbac dilutions down to 10−2 for over two weeks post application. Subsequently, AHD was added to SPLAT (emulsion only, without Bs or Bti) to attract gravid females (SPLATahd), or together with biological larvicides to attract ovipositing females and kill emerging larvae

  9. Insecticide resistance in Culex quinquefasciatus from Zanzibar: implications for vector control programmes

    PubMed Central

    2012-01-01

    Background Zanzibar has a long history of lymphatic filariasis (LF) caused by the filarial parasite Wuchereria bancrofti, and transmitted by the mosquito Culex quinquefasciatus Say. The LF Programme in Zanzibar has successfully implemented mass drug administration (MDA) to interrupt transmission, and is now in the elimination phase. Monitoring infections in mosquitoes, and assessing the potential role of interventions such as vector control, is important in case the disease re-emerges as a public health problem. Here, we examine Culex mosquito species from the two main islands to detect W. bancrofti infection and to determine levels of susceptibility to the insecticides used for vector control. Methods Culex mosquitoes collected during routine catches in Vitongoji, Pemba Island, and Makadara, Unguja Island were tested for W. bancrofti infection using PCR. Insecticide bioassays on Culex mosquitoes were performed to determine susceptibility to permethrin, deltamethrin, lambda-cyhalothrin, DDT and bendiocarb. Additional synergism assays with piperonyl butoxide (PBO) were used for lambda-cyhalothrin. Pyrosequencing was used to determine the kdr genotype and sequencing of the mitochondrial cytochrome oxidase I (mtCOI) subunit performed to identify ambiguous Culex species. Results None of the wild-caught Culex mosquitoes analysed were found to be positive for W. bancrofti. High frequencies of resistance to all insecticides were found in Wete, Pemba Island, whereas Culex from the nearby site of Tibirinzi (Pemba) and in Kilimani, Unguja Island remained relatively susceptible. Species identification confirmed that mosquitoes from Wete were Culex quinquefasciatus. The majority of the Culex collected from Tibirinzi and all from Kilimani could not be identified to species by molecular assays. Two alternative kdr alleles, both resulting in a L1014F substitution were detected in Cx. quinquefasciatus from Wete with no homozygote susceptible detected. Metabolic resistance to

  10. Dengue: Vector Biology, Transmission and Control Options in Mexico (El Dengue: Binomia Del Vector, Transmision y Opciones Para su Control en Mexico)

    DTIC Science & Technology

    1990-01-01

    plaguicidas ", "Resistance of disease vectors and carriers to pesticides" "Resistencia de los vectores de las enfermedades a los plagui- cidas...Organuzac6a Mundial de la S&lud, "Reastmencia de vectores y- reservorios de enfertnedades a "o plaguicidas ", OHS, Scen de Infomna T&zticce (1976...585. Orprizaci6n Mundial de ta Salud, "Resistencia de los. vectorts de Ias enfermedades a los plaguicidas ", OMS5 Sa’ic de Infor- mrer T&scAsk (19Ml 655

  11. Efficacy of local neem extracts for sustainable malaria vector control in an African village

    PubMed Central

    Gianotti, Rebecca L; Bomblies, Arne; Dafalla, Mustafa; Issa-Arzika, Ibrahim; Duchemin, Jean-Bernard; Eltahir, Elfatih AB

    2008-01-01

    Background Larval control of malaria vectors has been historically successful in reducing malaria transmission, but largely fell out of favour with the introduction of synthetic insecticides and bed nets. However, an integrated approach to malaria control, including larval control methods, continues to be the best chance for success, in view of insecticide resistance, the behavioural adaptation of the vectors to changing environments and the difficulties of reaching the poorest populations most at risk,. Laboratory studies investigating the effects of neem seed (Azadirachta indica) extracts on Anopheles larvae have shown high rates of larval mortality and reductions in adult longevity, as well as low potential for resistance development. Methods This paper describes a method whereby seeds of the neem tree can be used to reduce adult Anopheles gambiae s.l. abundance in a way that is low cost and can be implemented by residents of rural villages in western Niger. The study was conducted in Banizoumbou village, western Niger. Neem seeds were collected from around the village. Dried seeds were ground into a coarse powder, which was then sprinkled onto known Anopheles larvae breeding habitats twice weekly during the rainy season 2007. Adult mosquitoes were captured on a weekly basis in the village and captures compared to those from 2005 and 2006 over the same period. Adult mosquitoes were also captured in a nearby village, Zindarou, as a control data set and compared to those from Banizoumbou. Results It was found that twice-weekly applications of the powder to known breeding habitats of Anopheles larvae in 2007 resulted in 49% fewer adult female Anopheles gambiae s.l. mosquitoes in Banizoumbou, compared with previous captures under similar environmental conditions and with similar habitat characteristics in 2005 and 2006. The productivity of the system in 2007 was found to be suppressed compared to the mean behaviour of 2005 and 2006 in Banizoumbou, whereas no change

  12. The journey towards elimination of gambiense human African trypanosomiasis: not far, nor easy.

    PubMed

    Franco, J R; Simarro, P P; Diarra, A; Ruiz-Postigo, J A; Jannin, J G

    2014-05-01

    Considering the epidemic situation of gambiense human African trypanosomiasis (HAT) at the end of the twentieth century, the World Health Organization (WHO) and partners strengthened disease control and surveillance. Over the last 15 years, the activities implemented through the National Control Programmes have brought gambiense HAT under control and now its elimination is deemed as an achievable goal. In 2012, WHO targeted gambiense HAT for elimination as a public health problem by 2020. The final goal will be the sustainable disease elimination by 2030, defined as the interruption of the transmission of gambiense HAT. The elimination is considered feasible, because of the epidemiological vulnerability of the disease, the current state of control, the availability of strategies and tools and international commitment and political will. Integration of activities in the health system is needed to ensure the sustainability of the elimination. The development of user-friendly diagnostic and treatment tools will facilitate the integration process. Adequate funding is needed to implement activities, but also to support research that will make the elimination sustainable. A long-term commitment by donors is needed and ownership of the process by endemic countries is critical.

  13. Is participation contagious? Evidence from a household vector control campaign in urban Peru

    PubMed Central

    Buttenheim, Alison M.; Paz-Soldan, Valerie; Barbu, Corentin; Skovira, Christine; Calderón, Javier Quintanilla; Riveros, Lina Margot Mollesaca; Cornejo, Juan Oswaldo; Small, Dylan S.; Bicchieri, Christina; Naquira, Cesar; Levy, Michael Z.

    2013-01-01

    Objectives High rates of household participation are critical to the success of door-to-door vector control campaigns. We used the Health Belief Model to assess determinants of participation, including neighbor participation as a cue to action, in a Chagas disease vector control campaign in Peru. Methods We evaluated clustering of participation among neighbors; estimated participation as a function of household infestation status, neighborhood type, and number of participating neighbors; and described reported reasons for refusal to participate in a district of 2911 households. Results We observed significant clustering of participation along city blocks (p< .0001). Participation was significantly higher for households in new vs. established neighborhoods, for infested households, and for households with more participating neighbors. The effect of neighbor participation was greater in new neighborhoods. Conclusions Results support a “contagion” model of participation, highlighting the possibility that one or two participating households can tip a block towards full participation. Future campaigns can leverage these findings by making participation more visible, by addressing stigma associated with spraying, and by employing group incentives to spray. PMID:24062411

  14. Area-wide biological control of disease vectors and agents affecting wildlife.

    PubMed

    Reichard, R E

    2002-04-01

    Two examples of area-wide programmes, employing the sterile insect technique (SIT), which have eradicated a parasite and a disease vector common to domestic and wild animals are described. New World screwworm (NWS), Cochliomyia hominivorax, caused significant morbidity and mortality of livestock and wild mammals in tropical and subtropical areas of America before eradication was achieved in North America using the SIT and other components of an integrated pest management (IPM) programme. Movement of wild as well as domestic animals from an area which is infested with screwworm to a free area requires prophylactic treatment. Tsetse fly-borne trypanosomosis has an immense influence on the distribution of people and livestock in Africa. The immunotolerance of wildlife to the parasites is an important factor in maintaining some areas livestock free as wildlife refuges. Slaughter has ceased of wild hoofstock species considered to be disease reservoirs for control purposes. The SIT, combined with other IPM measures, has resulted in the eradication of the tsetse fly and trypanosomosis from Zanzibar. Other programmes in Africa are underway. Microbial 'biopesticides' have also been employed successfully against plant insect pests and some vectors of human disease. It seems likely that for the immediate future, wildlife may benefit from area-wide biological control programmes, intended mainly to protect humans and/or domestic animals.

  15. Can vector control play a useful supplementary role against bancroftian filariasis?

    PubMed Central

    Maxwell, C. A.; Mohammed, K.; Kisumku, U.; Curtis, C. F.

    1999-01-01

    A single campaign of mass treatment for bancroftian filariasis with diethylcarbamazine (DEC) in Makunduchi, a town in Zanzibar, United Republic of Tanzania, combined with elimination of mosquito breeding in pit latrines with polystyrene beads was followed by a progressive decline over a 5-year period in the microfilarial rate from 49% to 3%. Evidence that vector control had contributed to this long-term decline was obtained by comparison with another town, Moga, where a DEC campaign was used without vector control and where resurgence of microfilariae could be observed 3-6 years after the campaign. In Zanzibar town, treatment of 3844 wet pit latrines and cesspits with polystyrene beads reduced the adult mosquito population in houses by about 65%. Supplementary treatment of open drains and marshes with Bacillus sphaericus produced little or no additional reduction compared to a sector of the town where only pit treatment with polystyrene was carried out. The cost and effort of achieving the 65% reduction in mosquito population could hardly be justified for its impact on filariasis alone, but its noticeable impact on biting nuisance might help to gain community support for an integrated programme. PMID:10083712

  16. National malaria vector control policy: an analysis of the decision to scale-up larviciding in Nigeria

    PubMed Central

    Tesfazghi, Kemi; Hill, Jenny; Jones, Caroline; Ranson, Hilary; Worrall, Eve

    2016-01-01

    Background: New vector control tools are needed to combat insecticide resistance and reduce malaria transmission. The World Health Organization (WHO) endorses larviciding as a supplementary vector control intervention using larvicides recommended by the WHO Pesticides Evaluation Scheme (WHOPES). The decision to scale-up larviciding in Nigeria provided an opportunity to investigate the factors influencing policy adoption and assess the role that actors and evidence play in the policymaking process, in order to draw lessons that help accelerate the uptake of new methods for vector control. Methods: A retrospective policy analysis was carried out using in-depth interviews with national level policy stakeholders to establish normative national vector control policy or strategy decision-making processes and compare these with the process that led to the decision to scale-up larviciding. The interviews were transcribed, then coded and analyzed using NVivo10. Data were coded according to pre-defined themes from an analytical policy framework developed a priori. Results: Stakeholders reported that the larviciding decision-making process deviated from the normative vector control decision-making process. National malaria policy is normally strongly influenced by WHO recommendations, but the potential of larviciding to contribute to national economic development objectives through larvicide production in Nigeria was cited as a key factor shaping the decision. The larviciding decision involved a restricted range of policy actors, and notably excluded actors that usually play advisory, consultative and evidence generation roles. Powerful actors limited the access of some actors to the policy processes and content. This may have limited the influence of scientific evidence in this policy decision. Conclusions: This study demonstrates that national vector control policy change can be facilitated by linking malaria control objectives to wider socioeconomic considerations and

  17. Chlorfenapyr: a new insecticide with novel mode of action can control pyrethroid resistant malaria vectors

    PubMed Central

    2011-01-01

    Background Malaria vectors have acquired widespread resistance to many of the currently used insecticides, including synthetic pyrethroids. Hence, there is an urgent need to develop alternative insecticides for effective management of insecticide resistance in malaria vectors. In the present study, chlorfenapyr was evaluated against Anopheles culicifacies and Anopheles stephensi for its possible use in vector control. Methods Efficacy of chlorfenapyr against An. culicifacies and An. stephensi was assessed using adult bioassay tests. In the laboratory, determination of diagnostic dose, assessment of residual activity on different substrates, cross-resistance pattern with different insecticides and potentiation studies using piperonyl butoxide were undertaken by following standard procedures. Potential cross-resistance patterns were assessed on field populations of An. culicifacies. Results A dose of 5.0% chlorfenapyr was determined as the diagnostic concentration for assessing susceptibility applying the WHO tube test method in anopheline mosquitoes with 2 h exposure and 48 h holding period. The DDT-resistant/malathion-deltamethrin-susceptible strain of An. culicifacies species C showed higher LD50 and LD99 (0.67 and 2.39% respectively) values than the DDT-malathion-deltamethrin susceptible An. culicifacies species A (0.41 and 2.0% respectively) and An. stephensi strains (0.43 and 2.13% respectively) and there was no statistically significant difference in mortalities among the three mosquito species tested (p > 0.05). Residual activity of chlorfenapyr a.i. of 400 mg/m2 on five fabricated substrates, namely wood, mud, mud+lime, cement and cement + distemper was found to be effective up to 24 weeks against An. culicifacies and up to 34 weeks against An. stephensi. No cross-resistance to DDT, malathion, bendiocarb and deltamethrin was observed with chlorfenapyr in laboratory-reared strains of An. stephensi and field-caught An. culicifacies. Potentiation studies

  18. Monitoring malaria vector control interventions: effectiveness of five different adult mosquito sampling methods.

    PubMed

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

    2013-09-01

    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.

  19. A novel biopesticide PONNEEM to control human vector mosquitoes Anopheles stephensi L. and Culex quinquefasciatus Say.

    PubMed

    Maheswaran, Rajan; Ignacimuthu, Savarimuthu

    2015-09-01

    Organophosphate pesticides are widely used in vector mosquito management and agricultural pest management. These chemicals enter into natural water bodies and soil and cause hazards to the environment. The objective of this study was to prepare a natural pesticide which will not harm the environment and yet control vector mosquitoes. PONNEEM, a novel biopesticide, patented and prepared from the oils of Azadirachta indica and Pongamia glabra, was tested against Anopheles stephensi and Culex quinquefasciatus. One hundred percent larvicidal and ovicidal activities were observed at 0.1-ppm concentration of PONNEEM against the two mosquito species under laboratory and sunlight conditions up to 12 months from the date of manufacture. Very high oviposition reduction of 26.46 and 32.16 % is also recorded. Reductions in α-esterase level (0.0818 ± 0.340 and 0.2188 ± 0.003), β-esterase level (0.0866 ± 0.026 and 0.0398 ± 0.010 μg naphthol produced/min/mg larval protein), glutathione S-transferase enzyme (14.2571 ± 0.51 and 15.3326 ± 0.51 μmol/min/mg larval protein) and total protein levels (0.0390 ± 0.008 and 0.1975 ± 0.029 mg/individual larva in treated groups of A. stephensi and C. quinquefasciatus at 0.1-ppm concentration, respectively. The non-target organisms such as Gambusia affinis and Diplonychus indicus were not affected. Biopesticides are good alternatives to synthetic pesticides. PONNEEM can be effectively used for the management of human vector mosquitoes. Since it has a biodegradable nature and does not alter the environmental condition of water and soil.

  20. 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

  1. Genomic Footprints of Selective Sweeps from Metabolic Resistance to Pyrethroids in African Malaria Vectors Are Driven by Scale up of Insecticide-Based Vector Control

    PubMed Central

    Ndula, Miranda; Irving, Helen; Mzihalowa, Themba

    2017-01-01

    Insecticide resistance in mosquito populations threatens recent successes in malaria prevention. Elucidating patterns of genetic structure in malaria vectors to predict the speed and direction of the spread of resistance is essential to get ahead of the ‘resistance curve’ and to avert a public health catastrophe. Here, applying a combination of microsatellite analysis, whole genome sequencing and targeted sequencing of a resistance locus, we elucidated the continent-wide population structure of a major African malaria vector, Anopheles funestus. We identified a major selective sweep in a genomic region controlling cytochrome P450-based metabolic resistance conferring high resistance to pyrethroids. This selective sweep occurred since 2002, likely as a direct consequence of scaled up vector control as revealed by whole genome and fine-scale sequencing of pre- and post-intervention populations. Fine-scaled analysis of the pyrethroid resistance locus revealed that a resistance-associated allele of the cytochrome P450 monooxygenase CYP6P9a has swept through southern Africa to near fixation, in contrast to high polymorphism levels before interventions, conferring high levels of pyrethroid resistance linked to control failure. Population structure analysis revealed a barrier to gene flow between southern Africa and other areas, which may prevent or slow the spread of the southern mechanism of pyrethroid resistance to other regions. By identifying a genetic signature of pyrethroid-based interventions, we have demonstrated the intense selective pressure that control interventions exert on mosquito populations. If this level of selection and spread of resistance continues unabated, our ability to control malaria with current interventions will be compromised. PMID:28151952

  2. Genomic Footprints of Selective Sweeps from Metabolic Resistance to Pyrethroids in African Malaria Vectors Are Driven by Scale up of Insecticide-Based Vector Control.

    PubMed

    Barnes, Kayla G; Weedall, Gareth D; Ndula, Miranda; Irving, Helen; Mzihalowa, Themba; Hemingway, Janet; Wondji, Charles S

    2017-02-01

    Insecticide resistance in mosquito populations threatens recent successes in malaria prevention. Elucidating patterns of genetic structure in malaria vectors to predict the speed and direction of the spread of resistance is essential to get ahead of the 'resistance curve' and to avert a public health catastrophe. Here, applying a combination of microsatellite analysis, whole genome sequencing and targeted sequencing of a resistance locus, we elucidated the continent-wide population structure of a major African malaria vector, Anopheles funestus. We identified a major selective sweep in a genomic region controlling cytochrome P450-based metabolic resistance conferring high resistance to pyrethroids. This selective sweep occurred since 2002, likely as a direct consequence of scaled up vector control as revealed by whole genome and fine-scale sequencing of pre- and post-intervention populations. Fine-scaled analysis of the pyrethroid resistance locus revealed that a resistance-associated allele of the cytochrome P450 monooxygenase CYP6P9a has swept through southern Africa to near fixation, in contrast to high polymorphism levels before interventions, conferring high levels of pyrethroid resistance linked to control failure. Population structure analysis revealed a barrier to gene flow between southern Africa and other areas, which may prevent or slow the spread of the southern mechanism of pyrethroid resistance to other regions. By identifying a genetic signature of pyrethroid-based interventions, we have demonstrated the intense selective pressure that control interventions exert on mosquito populations. If this level of selection and spread of resistance continues unabated, our ability to control malaria with current interventions will be compromised.

  3. Malaria transmission after five years of vector control on Bioko Island, Equatorial Guinea

    PubMed Central

    2012-01-01

    extensive malaria control and a generalized reduction in the force of transmission, parasite prevalence and child mortality, foci of very high transmission persist on Bioko Island, particularly in the northwestern Punta Europa area. This area is favorable for anopheline mosquito breeding; human biting rates are high, and the EIRs are among the highest ever recorded. Both vector species collected in the study have a propensity to bite outdoors more frequently than indoors. Despite current vector control efforts mosquito densities remain high in such foci of high malaria transmission. To further reduce transmission, indoor residual spraying (IRS) needs to be supplemented with additional vector control interventions. PMID:23146423

  4. Socio-economic factors influencing control of vector-borne diseases in the pastoralist system of south western Uganda.

    PubMed

    Mugisha, Anthony; McLeod, Anni; Percy, Rachel; Kyewalabye, Elizabeth

    2008-05-01

    Research in control of tick-borne diseases and trypanosomosis, and their vectors, namely, ticks and tsetse flies respectively, has been on going for decades. However, very little attention has been paid to the socio-economic factors that are likely to influence the outcome of the interventions in the control of these diseases. Thus, this study was designed to investigate these factors, mainly the intra-household factors influencing decision-making in the control of Vector-borne diseases in the pastoralist areas of Uganda. These factors included: indigenous technical knowledge, household economic factors, and gender. Both qualitative and quantitative methods were used in the collection and analysis of data. The tools used for data collection included among others, participatory learning and action (PLA), and Case studies. The findings included the following: In pastoralist households, a big proportion of the household budget was allocated to vector-borne diseases control. In the male-headed households, men dominated decision-making on vector-borne diseases control, although the goals and priorities of men and women in these households were not the same. Also, vector-borne disease control was predominantly by use of modern veterinary drugs, and pastoralists treated sick cattle by themselves even in situations where there were veterinary personnel.

  5. Eco-bio-social research on community-based approaches for Chagas disease vector control in Latin America

    PubMed Central

    Gürtler, Ricardo E.; Yadon, Zaida E.

    2015-01-01

    This article provides an overview of three research projects which designed and implemented innovative interventions for Chagas disease vector control in Bolivia, Guatemala and Mexico. The research initiative was based on sound principles of community-based ecosystem management (ecohealth), integrated vector management, and interdisciplinary analysis. The initial situational analysis achieved a better understanding of ecological, biological and social determinants of domestic infestation. The key factors identified included: housing quality; type of peridomestic habitats; presence and abundance of domestic dogs, chickens and synanthropic rodents; proximity to public lights; location in the periphery of the village. In Bolivia, plastering of mud walls with appropriate local materials and regular cleaning of beds and of clothes next to the walls, substantially decreased domestic infestation and abundance of the insect vector Triatoma infestans. The Guatemalan project revealed close links between house infestation by rodents and Triatoma dimidiata, and vector infection with Trypanosoma cruzi. A novel community-operated rodent control program significantly reduced rodent infestation and bug infection. In Mexico, large-scale implementation of window screens translated into promising reductions in domestic infestation. A multi-pronged approach including community mobilisation and empowerment, intersectoral cooperation and adhesion to integrated vector management principles may be the key to sustainable vector and disease control in the affected regions. PMID:25604759

  6. Eco-bio-social research on community-based approaches for Chagas disease vector control in Latin America.

    PubMed

    Gürtler, Ricardo E; Yadon, Zaida E

    2015-02-01

    This article provides an overview of three research projects which designed and implemented innovative interventions for Chagas disease vector control in Bolivia, Guatemala and Mexico. The research initiative was based on sound principles of community-based ecosystem management (ecohealth), integrated vector management, and interdisciplinary analysis. The initial situational analysis achieved a better understanding of ecological, biological and social determinants of domestic infestation. The key factors identified included: housing quality; type of peridomestic habitats; presence and abundance of domestic dogs, chickens and synanthropic rodents; proximity to public lights; location in the periphery of the village. In Bolivia, plastering of mud walls with appropriate local materials and regular cleaning of beds and of clothes next to the walls, substantially decreased domestic infestation and abundance of the insect vector Triatoma infestans. The Guatemalan project revealed close links between house infestation by rodents and Triatoma dimidiata, and vector infection with Trypanosoma cruzi. A novel community-operated rodent control program significantly reduced rodent infestation and bug infection. In Mexico, large-scale implementation of window screens translated into promising reductions in domestic infestation. A multi-pronged approach including community mobilisation and empowerment, intersectoral cooperation and adhesion to integrated vector management principles may be the key to sustainable vector and disease control in the affected regions.

  7. Scientists and public involvement: a consultation on the relation between malaria, vector control and transgenic mosquitoes.

    PubMed

    Boëte, Christophe

    2011-12-01

    Among the hopes for vector-based malaria control, the use of transgenic mosquitoes able to kill malaria parasites is seen as a potential way to interrupt malaria transmission. While this potential solution is gaining some support, the ethical and social aspects related to this high-tech method remain largely unexplored and underestimated. Related to those latter points, the aim of the present survey is to determine how scientists working on malaria and its vector mosquitoes perceive public opinion and how they evaluate public consultations on their research. This study has been performed through a questionnaire addressing questions related to the type of research, the location, the nationality and the perception of the public involvement by scientists. The results suggest that even if malaria researchers agree to interact with a non-scientific audience, they (especially the ones from the global North) remain quite reluctant to have their research project submitted in a jargon-free version to the evaluation and the prior-agreement by a group of non-specialists. The study, by interrogating the links between the scientific community and the public from the perspective of the scientists, reveals the importance of fostering structures and processes that could lead to a better involvement of a non specialist public in the actual debates linking scientific, technological and public health issues in Africa.

  8. Major QTLs Control Resistance to Rice Hoja Blanca Virus and Its Vector Tagosodes orizicolus

    PubMed Central

    Romero, Luz E.; Lozano, Ivan; Garavito, Andrea; Carabali, Silvio J.; Triana, Monica; Villareal, Natalia; Reyes, Luis; Duque, Myriam C.; Martinez, César P.; Calvert, Lee; Lorieux, Mathias

    2013-01-01

    Rice hoja blanca (white leaf) disease can cause severe yield losses in rice in the Americas. The disease is caused by the rice hoja blanca virus (RHBV), which is transmitted by the planthopper vector Tagosodes orizicolus. Because classical breeding schemes for this disease rely on expensive, time-consuming screenings, there is a need for alternatives such as marker-aided selection. The varieties Fedearroz 2000 and Fedearroz 50, which are resistant to RHBV and to the feeding damage caused by T. orizicolus, were crossed with the susceptible line WC366 to produce segregating F2:3 populations. The F3 families were scored for their resistance level to RHBV and T. orizicolus. The F2:3 lines of both crosses were genotyped using microsatellite markers. One major QTL on the short arm of chromosome 4 was identified for resistance to RHBV in the two populations. Two major QTL on chromosomes 5 and 7 were identified for resistance to T. orizicolus in the Fd2000 × WC366 and Fd50 × WC366 crosses, respectively. This comparative study using two distinct rice populations allowed for a better understanding of how the resistance to RHBV and its vector are controlled genetically. Simple marker-aided breeding schemes based on QTL information can be designed to improve rice germplasm to reduce losses caused by this important disease. PMID:24240781

  9. Chagas disease vector control through different intervention modalities in endemic localities of Paraguay.

    PubMed Central

    Rojas de Arias, A.; Ferro, E. A.; Ferreira, M. E.; Simancas, L. C.

    1999-01-01

    In a field study carried out in three rural communities in Paraguay in a zone endemic for Chagas disease, we implemented three different vector control interventions--spraying, housing improvement, and a combination of spraying plus housing improvement--which effectively reduced the triatomine infestation. The reduction of triatomine infestation was 100% (47/47) in the combined intervention community, whereas in the community where housing improvement was carried out it was 96.4% (53/55). In the community where fumigation alone was used, the impact was 97.6% (40/41) in terms of domiciliary infestation. In all the houses where an intervention was made, an 18-month follow-up showed reinfestation rates of less than 10%. A serological survey of the population in the pre- and post-intervention periods revealed a shift in positive cases towards older age groups, but no significant differences were observed. The rate of seroconversion was 1.3% (three new cases) in the community with housing improvement only, but none of these cases could have resulted from vector transmission. The most cost-effective intervention was insecticide spraying, which during a 21-month follow-up period had a high impact on triatomine infestation and cost US$ 29 per house as opposed to US$ 700 per house for housing improvement. PMID:10327712

  10. Major QTLs control resistance to rice hoja blanca virus and its vector Tagosodes orizicolus.

    PubMed

    Romero, Luz E; Lozano, Ivan; Garavito, Andrea; Carabali, Silvio J; Triana, Monica; Villareal, Natalia; Reyes, Luis; Duque, Myriam C; Martinez, César P; Calvert, Lee; Lorieux, Mathias

    2014-01-10

    Rice hoja blanca (white leaf) disease can cause severe yield losses in rice in the Americas. The disease is caused by the rice hoja blanca virus (RHBV), which is transmitted by the planthopper vector Tagosodes orizicolus. Because classical breeding schemes for this disease rely on expensive, time-consuming screenings, there is a need for alternatives such as marker-aided selection. The varieties Fedearroz 2000 and Fedearroz 50, which are resistant to RHBV and to the feeding damage caused by T. orizicolus, were crossed with the susceptible line WC366 to produce segregating F2:3 populations. The F3 families were scored for their resistance level to RHBV and T. orizicolus. The F2:3 lines of both crosses were genotyped using microsatellite markers. One major QTL on the short arm of chromosome 4 was identified for resistance to RHBV in the two populations. Two major QTL on chromosomes 5 and 7 were identified for resistance to T. orizicolus in the Fd2000 × WC366 and Fd50 × WC366 crosses, respectively. This comparative study using two distinct rice populations allowed for a better understanding of how the resistance to RHBV and its vector are controlled genetically. Simple marker-aided breeding schemes based on QTL information can be designed to improve rice germplasm to reduce losses caused by this important disease.

  11. Test stand for precise measurement of impulse and thrust vector of small attitude control jets

    NASA Technical Reports Server (NTRS)

    Woodruff, J. R.; Chisel, D. M.

    1973-01-01

    A test stand which accurately measures the impulse bit and thrust vector of reaction jet thrusters used in the attitude control system of space vehicles has been developed. It can be used to measure, in a vacuum or ambient environment, both impulse and thrust vector of reaction jet thrusters using hydrazine or inert gas propellants. The ballistic pendulum configuration was selected because of its accuracy, simplicity, and versatility. The pendulum is mounted on flexure pivots rotating about a vertical axis at the center of its mass. The test stand has the following measurement capabilities: impulse of 0.00004 to 4.4 N-sec (0.00001 to 1.0 lb-sec) with a pulse duration of 0.5 msec to 1 sec; static thrust of 0.22 to 22 N (0.05 to 5 lb) with a 5 percent resolution; and thrust angle alinement of 0.22 to 22 N (0.05 to 5 lb) thrusters with 0.01 deg accuracy.

  12. Genetically modifying the insect gut microbiota to control Chagas disease vectors through systemic RNAi.

    PubMed

    Taracena, Mabel L; Oliveira, Pedro L; Almendares, Olivia; Umaña, Claudia; Lowenberger, Carl; Dotson, Ellen M; Paiva-Silva, Gabriela O; Pennington, Pamela M

    2015-02-01

    Technologies based on RNA interference may be used for insect control. Sustainable strategies are needed to control vectors of Chagas disease such as Rhodnius prolixus. The insect microbiota can be modified to deliver molecules to the gut. Here, Escherichia coli HT115(DE3) expressing dsRNA for the Rhodnius heme-binding protein (RHBP) and for catalase (CAT) were fed to nymphs and adult triatomine stages. RHBP is an egg protein and CAT is an antioxidant enzyme expressed in all tissues by all developmental stages. The RNA interference effect was systemic and temporal. Concentrations of E. coli HT115(DE3) above 3.35 × 10(7) CFU/mL produced a significant RHBP and CAT gene knockdown in nymphs and adults. RHBP expression in the fat body was reduced by 99% three days after feeding, returning to normal levels 10 days after feeding. CAT expression was reduced by 99% and 96% in the ovary and the posterior midgut, respectively, five days after ingestion. Mortality rates increased by 24-30% in first instars fed RHBP and CAT bacteria. Molting rates were reduced by 100% in first instars and 80% in third instars fed bacteria producing RHBP or CAT dsRNA. Oviposition was reduced by 43% (RHBP) and 84% (CAT). Embryogenesis was arrested in 16% (RHBP) and 20% (CAT) of laid eggs. Feeding females 105 CFU/mL of the natural symbiont, Rhodococcus rhodnii, transformed to express RHBP-specific hairpin RNA reduced RHBP expression by 89% and reduced oviposition. Modifying the insect microbiota to induce systemic RNAi in R. prolixus may result in a paratransgenic strategy for sustainable vector control.

  13. American Trypanosomiasis (Also Known as Chagas Disease) Detailed FAQs

    MedlinePlus

    ... which is transmitted to animals and people by insect vectors that are found only in the Americas ( ... the main way is through vectorborne transmission. The insect vectors are called triatomine bugs. These blood-sucking ...

  14. American Trypanosomiasis (Also Known as Chagas Disease) Treatment

    MedlinePlus

    ... United States Trypanosoma cruzi Infection Study: Evidence for Vector-borne Transmission of the Parasite That Causes Chagas ... United States Trypanosoma cruzi Infection Study: Evidence for Vector-borne Transmission of the Parasite That Causes Chagas ...

  15. Effectiveness of Large-Scale Chagas Disease Vector Control Program in Nicaragua by Residual Insecticide Spraying against Triatoma dimidiata

    PubMed Central

    Yoshioka, Kota; Nakamura, Jiro; Pérez, Byron; Tercero, Doribel; Pérez, Lenin; Tabaru, Yuichiro

    2015-01-01

    Chagas disease is one of the most serious health problems in Latin America. Because the disease is transmitted mainly by triatomine vectors, a three-phase vector control strategy was used to reduce its vector-borne transmission. In Nicaragua, we implemented an indoor insecticide spraying program in five northern departments to reduce house infestation by Triatoma dimidiata. The spraying program was performed in two rounds. After each round, we conducted entomological evaluation to compare the vector infestation level before and after spraying. A total of 66,200 and 44,683 houses were sprayed in the first and second spraying rounds, respectively. The entomological evaluation showed that the proportion of houses infested by T. dimidiata was reduced from 17.0% to 3.0% after the first spraying, which was statistically significant (P < 0.0001). However, the second spraying round did not demonstrate clear effectiveness. Space–time analysis revealed that reinfestation of T. dimidiata is more likely to occur in clusters where the pre-spray infestation level is high. Here we discuss how large-scale insecticide spraying is neither effective nor affordable when T. dimidiata is widely distributed at low infestation levels. Further challenges involve research on T. dimidiata reinfestation, diversification of vector control strategies, and implementation of sustainable vector surveillance. PMID:26416118

  16. Implementation of the Orbital Maneuvering Systems Engine and Thrust Vector Control for the European Service Module

    NASA Technical Reports Server (NTRS)

    Millard, Jon

    2014-01-01

    The European Space Agency (ESA) has entered into a partnership with the National Aeronautics and Space Administration (NASA) to develop and provide the Service Module (SM) for the Orion Multipurpose Crew Vehicle (MPCV) Program. The European Service Module (ESM) will provide main engine thrust by utilizing the Space Shuttle Program Orbital Maneuvering System Engine (OMS-E). Thrust Vector Control (TVC) of the OMS-E will be provided by the Orbital Maneuvering System (OMS) TVC, also used during the Space Shuttle Program. NASA will be providing the OMS-E and OMS TVC to ESA as Government Furnished Equipment (GFE) to integrate into the ESM. This presentation will describe the OMS-E and OMS TVC and discuss the implementation of the hardware for the ESM.

  17. PAB3D Simulations of a Nozzle with Fluidic Injection for Yaw Thrust-Vector Control

    NASA Technical Reports Server (NTRS)

    Deere, Karen A.

    1998-01-01

    An experimental and computational study was conducted on an exhaust nozzle with fluidic injection for yaw thrust-vector control. The nozzle concept was tested experimentally in the NASA Langley Jet Exit Test Facility (JETF) at nozzle pressure ratios up to 4 and secondary fluidic injection flow rates up to 15 percent of the primary flow rate. Although many injection-port geometries and two nozzle planforms (symmetric and asymmetric) were tested experimentally, this paper focuses on the computational results of the more successful asymmetric planform with a slot injection port. This nozzle concept was simulated with the Navier-Stokes flow solver, PAB3D, invoking the Shih, Zhu, and Lumley algebraic Reynolds stress turbulence model (ASM) at nozzle pressure ratios (NPRs) of 2,3, and 4 with secondary to primary injection flow rates (w(sub s)/w(sub p)) of 0, 2, 7 and 10 percent.

  18. Polarization-based control of spin-orbit vector modes of light in biphoton interference.

    PubMed

    Leary, C C; Lankford, Maggie; Sundarraman, Deepika

    2016-06-27

    We report the experimental generation of a class of spin-orbit vector modes of light via an asymmetric Mach-Zehnder interferometer, obtained from an input beam prepared in a product state of its spin and orbital degrees of freedom. These modes contain a spatially varying polarization structure which may be controllably propagated about the beam axis by varying the retardance between the vertical and horizontal polarization components of the light. Additionally, their transverse spatial intensity distributions may be continuously manipulated by tuning the input polarization parameters. In the case of an analogous biphoton input, we predict that this device will exhibit biphoton (Hong-Ou-Mandel) interference in conjunction with the aforementioned tunable mode transformations.

  19. Different mosquito species host Wickerhamomyces anomalus (Pichia anomala): perspectives on vector-borne diseases symbiotic control.

    PubMed

    Ricci, Irene; Mosca, Michela; Valzano, Matteo; Damiani, Claudia; Scuppa, Patrizia; Rossi, Paolo; Crotti, Elena; Cappelli, Alessia; Ulissi, Ulisse; Capone, Aida; Esposito, Fulvio; Alma, Alberto; Mandrioli, Mauro; Sacchi, Luciano; Bandi, Claudio; Daffonchio, Daniele; Favia, Guido

    2011-01-01

    The genetic manipulation of the microbial community associated with hematophagus insects is particularly relevant for public health applications. Within mosquito populations, this relationship has been overlooked until recently. New advances in molecular biotechnology propose the genetic manipulation of mosquito symbionts to prevent the transmission of pathogens to humans by interfering with the obligatory life cycle stages within the insect through the use of effector molecules. This approach, defined as 'paratransgenesis', has opened the way for the investigation and characterization of microbes residing in the mosquito body, particularly those localised within the gut. Some interesting bacteria have been identified as candidates for genetic modification, however, endosymbiotic yeasts remain largely unexplored with little information on the symbiotic relationships to date. Here we review the recent report of symbiotic relationship between Wickerhamomyces anomalus (Pichia anomala) and several mosquito vector species as promising methods to implement control of mosquito-borne diseases.

  20. An agent-based model to simulate tsetse fly distribution and control techniques: a case study in Nguruman, Kenya

    PubMed Central

    Lin, Shengpan; DeVisser, Mark H.; Messina, Joseph P.

    2015-01-01

    Background African trypanosomiasis, also known as “sleeping sickness” in humans and “nagana” in livestock is an important vector-borne disease in Sub-Saharan Africa. Control of trypanosomiasis has focused on eliminating the vector, the tsetse fly (Glossina, spp.). Effective tsetse fly control planning requires models to predict tsetse population and distribution changes over time and space. Traditional planning models have used statistical tools to predict tsetse distributions and have been hindered by limited field survey data. Methodology/Results We developed an Agent-Based Model (ABM) to provide timing and location information for tsetse fly control without presence/absence training data. The model is driven by daily remotely-sensed environment data. The model provides a flexible tool linking environmental changes with individual biology to analyze tsetse control methods such as aerial insecticide spraying, wild animal control, releasing irradiated sterile tsetse males, and land use and cover modification. Significance This is a bottom-up process-based model with freely available data as inputs that can be easily transferred to a new area. The tsetse population simulation more closely approximates real conditions than those using traditional statistical models making it a useful tool in tsetse fly control planning. PMID:26309347

  1. Utility of expanded polystyrene (EPS) beads in the control of vector-borne diseases.

    PubMed

    Sivagnaname, N; Amalraj, D Dominic; Mariappan, T

    2005-10-01

    The use of chemicals or bio-larvicides for the control of Culex quinquefasciatus and Anopheles stephensi breeding in pit latrines and overhead tanks (OHT) respectively is discouraged owing to many undesirable impacts in the environment. Due to faecal contamination and poor survival, use of predatory fish in OHTs is not feasible. The use of expanded polystyrene (EPS) beads is a potential alternative in these habitats. EPS beads not only prevent oviposition but also kill the immature by forming a thick blanket on the water surface. A thick layer of 2 cm with beads of 2 mm is sufficient to suppress and prevent mosquito breeding. These are cheap, environmentally safe and do not need frequent application since they remain on the surface for quiet a long time. Successful trials against C. quinquefasciatus breeding in pit latrines, soakage pits, septic tanks, etc., have been carried out in Kenya, Zimbabwe and Tanzania. Certain trials with EPS indicated reduction in microfilaria (mf) rate besides decline in biting density. In India, EPS beads have also been used on small scale for the control of A. stephensi and A. culicifacies breeding in OHTs and unused wells respectively. The polystyrene beads have also been reported to be effective in the control of mosquito breeding in biogas plants and other industrial situations. The practical utility of EPS beads in the control of vector-borne diseases has been discussed in the present review.

  2. Characterization of truck-mounted atomization equipment typically used in vector control.

    PubMed

    Hoffmann, W C; Walker, T W; Martin, D E; Barber, J A B; Gwinn, T; Smith, V L; Szumlas, D; Lan, Y; Fritz, B K

    2007-09-01

    The control of medically important arthropod vectors of human and animal disease is a high priority for both public health and military officials. Because droplet size of pesticide spray material is a critical factor affecting vector control applications, the droplet-size spectra produced by 11 sprayers and 3 spray formulations were evaluated. Droplet-size spectra were measured by a laser diffraction instrument, a hot-wire system, and rotating slides. There were considerable differences in the droplet-size spectra produced by the different sprayers tested. The volume median diameter (Dv0.5) for the water-based sprays ranged from 4.7 to 211 microm, depending on the sprayer, and the percent of spray volume contained in droplets less than 20 microm (%vol <20 microm) ranged between 0.5% and 98.9%. The Dv0.5 measurements for the oil-based sprays ranged from 9.4 to 125.3 microm and the %vol <20 microm ranged between 2.4% and 97.9%. The correlations between the Dv0.5 measured by the laser system (Dv0.5-laser) and the mass median diameter, Sauter diameter, and Dv0.5 measured by the AIMS probe were all significant. Generally, the slide Dv0.5s were numerically similar to the Dv0.5 from the laser system and the Sauter diameter from the Army Insecticide Measuring System probe. There was less consistent agreement between the % <32 microm values obtained from the slides and those from the other 2 samplers. The information presented can be used by applicators to select the sprayer that produces the droplet-size spectra needed for their particular application situation.

  3. Quantitative evaluation of a thrust vector controlled transport at the conceptual design phase

    NASA Astrophysics Data System (ADS)

    Ricketts, Vincent Patrick

    The impetus to innovate, to push the bounds and break the molds of evolutionary design trends, often comes from competition but sometimes requires catalytic political legislature. For this research endeavor, the 'catalyzing legislation' comes in response to the rise in cost of fossil fuels and the request put forth by NASA on aircraft manufacturers to show reduced aircraft fuel consumption of +60% within 30 years. This necessitates that novel technologies be considered to achieve these values of improved performance. One such technology is thrust vector control (TVC). The beneficial characteristic of thrust vector control technology applied to the traditional tail-aft configuration (TAC) commercial transport is its ability to retain the operational advantage of this highly evolved aircraft type like cabin evacuation, ground operation, safety, and certification. This study explores if the TVC transport concept offers improved flight performance due to synergistically reducing the traditional empennage size, overall resulting in reduced weight and drag, and therefore reduced aircraft fuel consumption. In particular, this study explores if the TVC technology in combination with the reduced empennage methodology enables the TAC aircraft to synergistically evolve while complying with current safety and certification regulation. This research utilizes the multi-disciplinary parametric sizing software, AVD Sizing, developed by the Aerospace Vehicle Design (AVD) Laboratory. The sizing software is responsible for visualizing the total system solution space via parametric trades and is capable of determining if the TVC technology can enable the TAC aircraft to synergistically evolve, showing marked improvements in performance and cost. This study indicates that the TVC plus reduced empennage methodology shows marked improvements in performance and cost.

  4. Plant extracts, isolated phytochemicals, and plant-derived agents which are lethal to arthropod vectors of human tropical diseases--a review.

    PubMed

    Pohlit, Adrian Martin; Rezende, Alex Ribeiro; Lopes Baldin, Edson Luiz; Lopes, Norberto Peporine; Neto, Valter Ferreira de Andrade

    2011-04-01

    The recent scientific literature on plant-derived agents with potential or effective use in the control of the arthropod vectors of human tropical diseases is reviewed. Arthropod-borne tropical diseases include: amebiasis, Chagas disease (American trypanosomiasis), cholera, cryptosporidiosis, dengue (hemorrhagic fever), epidemic typhus (Brill-Zinsser disease), filariasis (elephantiasis), giardia (giardiasis), human African trypanosomiasis (sleeping sickness), isosporiasis, leishmaniasis, Lyme disease (lyme borreliosis), malaria, onchocerciasis, plague, recurrent fever, sarcocystosis, scabies (mites as causal agents), spotted fever, toxoplasmosis, West Nile fever, and yellow fever. Thus, coverage was given to work describing plant-derived extracts, essential oils (EOs), and isolated chemicals with toxic or noxious effects on filth bugs (mechanical vectors), such as common houseflies (Musca domestica Linnaeus), American and German cockroaches (Periplaneta americana Linnaeus, Blatella germanica Linnaeus), and oriental latrine/blowflies (Chrysomya megacephala Fabricius) as well as biting, blood-sucking arthropods such as blackflies (Simulium Latreille spp.), fleas (Xenopsylla cheopis Rothschild), kissing bugs (Rhodnius Stål spp., Triatoma infestans Klug), body and head lice (Pediculus humanus humanus Linnaeus, P. humanus capitis De Geer), mosquitoes (Aedes Meigen, Anopheles Meigen, Culex L., and Ochlerotatus Lynch Arribálzaga spp.), sandflies (Lutzomyia longipalpis Lutz & Neiva, Phlebotomus Loew spp.), scabies mites (Sarcoptes scabiei De Geer, S. scabiei var hominis, S. scabiei var canis, S. scabiei var suis), and ticks (Ixodes Latreille, Amblyomma Koch, Dermacentor Koch, and Rhipicephalus Koch spp.). Examples of plant extracts, EOs, and isolated chemicals exhibiting noxious or toxic activity comparable or superior to the synthetic control agents of choice (pyrethroids, organophosphorous compounds, etc.) are provided in the text for many arthropod vectors of tropical

  5. Emerging trends in the diagnosis of human African Trypanosomiasis.

    PubMed

    Radwanska, Magdalena

    2010-12-01

    Human African trypanosomiasis (HAT) or sleeping sickness is caused by protozoan parasites Trypanosoma brucei gambiense and T. b. rhodesiense. Despite the enormous technological progress in molecular parasitology in recent years, the diagnosis of HAT is still problematic due to the lack of specific tools. To date, there are two realities when it comes to HAT; the first one being the world of modern experimental laboratories, equipped with the latest state-of-the-art technology, and the second being the world of HAT diagnosis, where the latest semi-commercial test was introduced 30 years ago (Magnus et al. 1978). Hence, it appears that the lack of progress in HAT diagnosis is not primarily due to a lack of scientific interest or a lack of research funds, but mainly results from the many obstacles encountered in the translation of basic research into field-applicable diagnostics. This review will provide an overview of current diagnostic methods and highlight specific difficulties in solving the shortcomings of these methods. Future perspectives for accurate, robust, affordable diagnostics will be discussed as well.

  6. Human African trypanosomiasis in endemic populations and travellers.

    PubMed

    Blum, J A; Neumayr, A L; Hatz, C F

    2012-06-01

    Human African trypanosomiasis (HAT) or sleeping sickness is caused by the protozoan parasites Trypanosoma brucei (T.b.) gambiense (West African form) and T.b. rhodesiense (East African form) that are transmitted by the bite of the tsetse fly, Glossina spp.. Whereas most patients in endemic populations are infected with T.b. gambiense, most tourists are infected with T.b. rhodesiense. In endemic populations, T.b. gambiense HAT is characterized by chronic and intermittent fever, headache, pruritus, and lymphadenopathy in the first stage and by sleep disturbances and neuro-psychiatric disorders in the second stage. Recent descriptions of the clinical presentation of T.b. rhodesiense in endemic populations show a high variability in different foci. The symptomatology of travellers is markedly different from the usual textbook descriptions of African HAT patients. The onset of both infections is almost invariably an acute and febrile disease. Diagnosis and treatment are difficult and rely mostly on old methods and drugs. However, new molecular diagnostic technologies are under development. A promising new drug combination is currently evaluated in a phase 3 b study and further new drugs are under evaluation.

  7. Dyes, trypanosomiasis and DNA: a historical and critical review.

    PubMed

    Wainwright, M

    2010-12-01

    Trypanosomiasis, a group of diseases including sleeping sickness in humans and Nagana in cattle in Africa, and Chagas' disease in South America, remains a considerable problem in the 21(st) century. The therapies that are available, however, usually have their roots in the "dye therapy" of a century ago, knowledge gained at the microscope from parasite staining procedures and converted to chemotherapy based on compounds closely related to the laboratory reagents. Dyes such as trypan red and trypan blue led to the development of suramin, while cationic nitrogen heterocyclic dyes furnished examples of the phenanthridinium class, such as ethidium (homidium) and isometamidium. Both suramin and isometamidium remain in use. Owing to mutagenicity issues, the presence of ethidium among the phenanthridinium dyes has led to concerns over the clinical use of related derivatives. There are several mechanisms for dye-DNA interaction, however, including possible hydrogen bonding of dye to the polymer, and these are discussed together with structure-activity relations and cellular localization of the phenanthridine and isomeric acridines involved. Better understanding of nucleic acid binding properties has allowed the preparation of more effective phenanthridinium analogues intended for use as anticancer/antiviral therapy.

  8. Recent Updates on Development of Drug Molecules for Human African Trypanosomiasis.

    PubMed

    Singh Grewal, Ajmer; Pandita, Deepti; Bhardwaj, Shashikant; Lather, Viney

    2016-01-01

    Human African trypanosomiasis (HAT, better called as sleeping sickness), caused by two morphologically identicalprotozoan parasite Trypanosoma bruceiis transmitted by the bite of tsetse flies of Glossinagenus, mainly in the rural areas of the sub-Saharan Africa. HAT is one of the neglected tropical diseases and is characterized by sleep disturbance as the main symptom, hence is called as sleeping sickness. As it is epidemic in the poorest population of Africa, there is limited availability of safe and cost-effective tools for controlling the disease. Trypanosoma bruceigambiense causes sleeping sickness in Western and Central Africa, whereas Trypanosoma bruceirhodesiense is the reason for prevalence of sleeping sickness in Eastern and Southern Africa. For the treatment of sleeping sickness, only five drugs have been approved suramin, pentamidine, melarsoprol, eflornithine and nifurtimox. Various small molecules of diverse chemical nature have been synthesized for targeting HAT and many of them are in the clinical trialsincluding fexinidazole (phase I completed) and SCYX-7158 (advanced in phase I). The present work has been planned to review various types of small molecules developed in the last 10 years having potent antitrypanosoma activity likely to be beneficial in sleeping sickness along with different natural anti-HAT agents.

  9. Update on field use of the available drugs for the chemotherapy of human African trypanosomiasis.

    PubMed

    Simarro, P P; Franco, J; Diarra, A; Postigo, J A Ruiz; Jannin, J

    2012-06-01

    Despite the fact that eflornithine was considered as the safer drug to treat human African trypanosomiasis (HAT) and has been freely available since 2001, the difficulties in logistics and cost burden associated with this drug meant that the toxic melarsoprol remained the drug of choice. The World Health Organization responded to the situation by designing a medical kit containing all the materials needed to use eflornithine, and by implementing a training and drugs distribution programme which has allowed a transition to this much safer treatment. The introduction of the combination of nifurtimox and eflornithine (NECT) has accelerated the shift from melarsoprol to the best treatment available, due to reduced dosage and treatment time for eflornithine that has significantly lessened the cost and improved the burden of logistics encountered during treatment and distribution. The decrease in the use of more dangerous but cheaper melarsoprol has meant a rise in the per patient cost of treating HAT. Although NECT is cheaper than eflornithine monotherapy, an unexpected consequence has been a continuing rise in the per patient cost of treating HAT. The ethical decision of shifting to the best available treatment imposes a financial burden on HAT control programmes that might render long-term application unsustainable. These factors call for continuing research to provide new safer and more effective drugs that are simple to administer and cheaper when compared to current drugs.

  10. Forecasting Human African Trypanosomiasis Prevalences from Population Screening Data Using Continuous Time Models

    PubMed Central

    Hasker, Epco; Lumbala, Crispin; Lutumba, Pascal; de Vlas, Sake J.; van de Klundert, Joris

    2016-01-01

    To eliminate and eradicate gambiense human African trypanosomiasis (HAT), maximizing the effectiveness of active case finding is of key importance. The progression of the epidemic is largely influenced by the planning of these operations. This paper introduces and analyzes five models for predicting HAT prevalence in a given village based on past observed prevalence levels and past screening activities in that village. Based on the quality of prevalence level predictions in 143 villages in Kwamouth (DRC), and based on the theoretical foundation underlying the models, we consider variants of the Logistic Model—a model inspired by the SIS epidemic model—to be most suitable for predicting HAT prevalence levels. Furthermore, we demonstrate the applicability of this model to predict the effects of planning policies for screening operations. Our analysis yields an analytical expression for the screening frequency required to reach eradication (zero prevalence) and a simple approach for determining the frequency required to reach elimination within a given time frame (one case per 10000). Furthermore, the model predictions suggest that annual screening is only expected to lead to eradication if at least half of the cases are detected during the screening rounds. This paper extends knowledge on control strategies for HAT and serves as a basis for further modeling and optimization studies. PMID:27657937

  11. Results of solar electric thrust vector control system design, development and tests

    NASA Technical Reports Server (NTRS)

    Fleischer, G. E.

    1973-01-01

    Efforts to develop and test a thrust vector control system TVCS for a solar-energy-powered ion engine array are described. The results of solar electric propulsion system technology (SEPST) III real-time tests of present versions of TVCS hardware in combination with computer-simulated attitude dynamics of a solar electric multi-mission spacecraft (SEMMS) Phase A-type spacecraft configuration are summarized. Work on an improved solar electric TVCS, based on the use of a state estimator, is described. SEPST III tests of TVCS hardware have generally proved successful and dynamic response of the system is close to predictions. It appears that, if TVCS electronic hardware can be effectively replaced by control computer software, a significant advantage in control capability and flexibility can be gained in future developmental testing, with practical implications for flight systems as well. Finally, it is concluded from computer simulations that TVCS stabilization using rate estimation promises a substantial performance improvement over the present design.

  12. High effective coverage of vector control interventions in children after achieving low malaria transmission in Zanzibar, Tanzania

    PubMed Central

    2013-01-01

    Background Formerly a high malaria transmission area, Zanzibar is now targeting malaria elimination. A major challenge is to avoid resurgence of malaria, the success of which includes maintaining high effective coverage of vector control interventions such as bed nets and indoor residual spraying (IRS). In this study, caretakers' continued use of preventive measures for their children is evaluated, following a sharp reduction in malaria transmission. Methods A cross-sectional community-based survey was conducted in June 2009 in North A and Micheweni districts in Zanzibar. Households were randomly selected using two-stage cluster sampling. Interviews were conducted with 560 caretakers of under-five-year old children, who were asked about perceptions on the malaria situation, vector control, household assets, and intention for continued use of vector control as malaria burden further decreases. Results Effective coverage of vector control interventions for under-five children remains high, although most caretakers (65%; 363/560) did not perceive malaria as presently being a major health issue. Seventy percent (447/643) of the under-five children slept under a long-lasting insecticidal net (LLIN) and 94% (607/643) were living in houses targeted with IRS. In total, 98% (628/643) of the children were covered by at least one of the vector control interventions. Seasonal bed-net use for children was reported by 25% (125/508) of caretakers of children who used bed nets. A high proportion of caretakers (95%; 500/524) stated that they intended to continue using preventive measures for their under-five children as malaria burden further reduces. Malaria risk perceptions and different perceptions of vector control were not found to be significantly associated with LLIN effective coverage. Conclusions While the majority of caretakers felt that malaria had been reduced in Zanzibar, effective coverage of vector control interventions remained high. Caretakers appreciated the

  13. New Paradigms for Virus Detection, Surveillance and Control of Zika Virus Vectors in the Settings of Southeast Asia.

    PubMed

    Vythilingam, Indra; Sam, Jamal I-C; Chan, Yoke F; Khaw, Loke T; Sulaiman, Wan Y Wan

    2016-01-01

    Zika virus (ZIKV) has now become a global public health concern. The vectors for ZIKV are Aedes aegypti and A. albopictus. Both these mosquitoes are predominant in Southeast Asia and are also responsible for the spread of other arboviral diseases like dengue virus and chikungunya virus. The incidence of dengue has been increasing over the years and this is of concern to public health workers. Simple laboratory tools for the detection of ZIKV is also lacking. In the absence of drugs and vaccine for these arboviral diseases, vector control is the main option for surveillance and control. Aedes larval surveys have been the hallmark of dengue control along with larviciding and fogging when cases are reported. However, we need new paradigms and options for control of these vectors. The current situation in Southeast Asia clearly proves that effective strategies for vector control need to be proactive and not reactive. This will be the way forward to control epidemics of these diseases inclusive of ZIKV until a vaccine becomes available.

  14. New Paradigms for Virus Detection, Surveillance and Control of Zika Virus Vectors in the Settings of Southeast Asia

    PubMed Central

    Vythilingam, Indra; Sam, Jamal I-C.; Chan, Yoke F.; Khaw, Loke T.; Sulaiman, Wan Y. Wan

    2016-01-01

    Zika virus (ZIKV) has now become a global public health concern. The vectors for ZIKV are Aedes aegypti and A. albopictus. Both these mosquitoes are predominant in Southeast Asia and are also responsible for the spread of other arboviral diseases like dengue virus and chikungunya virus. The incidence of dengue has been increasing over the years and this is of concern to public health workers. Simple laboratory tools for the detection of ZIKV is also lacking. In the absence of drugs and vaccine for these arboviral diseases, vector control is the main option for surveillance and control. Aedes larval surveys have been the hallmark of dengue control along with larviciding and fogging when cases are reported. However, we need new paradigms and options for control of these vectors. The current situation in Southeast Asia clearly proves that effective strategies for vector control need to be proactive and not reactive. This will be the way forward to control epidemics of these diseases inclusive of ZIKV until a vaccine becomes available. PMID:27679623

  15. An araC-controlled bacterial cre expression system to produce DNA minicircle vectors for nuclear and mitochondrial gene therapy.

    PubMed

    Bigger, B W; Tolmachov, O; Collombet, J M; Fragkos, M; Palaszewski, I; Coutelle, C

    2001-06-22

    The presence of CpG motifs and their associated sequences in bacterial DNA causes an immunotoxic response following the delivery of these plasmid vectors into mammalian hosts. We describe a biotechnological approach to the elimination of this problem by the creation of a bacterial cre recombinase expression system, tightly controlled by the arabinose regulon. This permits the Cre-mediated and -directed excision of the entire bacterial vector sequences from plasmid constructs to create supercoiled gene expression minicircles for gene therapy. Minicircle yields using standard culture volumes are sufficient for most in vitro and in vivo applications whereas minicircle expression in vitro is significantly increased over standard plasmid transfection. By the simple expedient of removing the bacterial DNA complement, we significantly reduce the size and CpG content of these expression vectors, which should also reduce DNA-induced inflammatory responses in a dose-dependent manner. We further describe the generation of minicircle expression vectors for mammalian mitochondrial gene therapy, for which no other vector systems currently exist. The removal of bacterial vector sequences should permit appropriate transcription and correct transcriptional cleavage from the mitochondrial minicircle constructs in a mitochondrial environment and brings the realization of mitochondrial gene therapy a step closer.

  16. Digitally controlled high-performance dc SQUID readout electronics for a 304-channel vector magnetometer

    NASA Astrophysics Data System (ADS)

    Bechstein, S.; Petsche, F.; Scheiner, M.; Drung, D.; Thiel, F.; Schnabel, A.; Schurig, Th

    2006-06-01

    Recently, we have developed a family of dc superconducting quantum interference device (SQUID) readout electronics for several applications. These electronics comprise a low-noise preamplifier followed by an integrator, and an analog SQUID bias circuit. A highly-compact low-power version with a flux-locked loop bandwidth of 0.3 MHz and a white noise level of 1 nV/√Hz was specially designed for a 304-channel low-Tc dc SQUID vector magnetometer, intended to operate in the new Berlin Magnetically Shielded Room (BMSR-2). In order to minimize the space needed to mount the electronics on top of the dewar and to minimize the power consumption, we have integrated four electronics channels on one 3 cm × 10 cm sized board. Furthermore we embedded the analog components of these four channels into a digitally controlled system including an in-system programmable microcontroller. Four of these integrated boards were combined to one module with a size of 4 cm × 4 cm × 16 cm. 19 of these modules were implemented, resulting in a total power consumption of about 61 W. To initialize the 304 channels and to service the system we have developed software tools running on a laptop computer. By means of these software tools the microcontrollers are fed with all required data such as the working points, the characteristic parameters of the sensors (noise, voltage swing), or the sensor position inside of the vector magnetometer system. In this paper, the developed electronics including the software tools are described, and first results are presented.

  17. Natural products from plants as drug candidates and lead compounds against leishmaniasis and trypanosomiasis.

    PubMed

    Salem, Manar M; Werbovetz, Karl A

    2006-01-01

    Millions of people in the developing world are affected by diseases caused by the kinetoplastid parasites: the leishmaniases, African trypanosomiasis, and Chagas disease. In many cases the drugs employed for treatment are toxic, marginally effective, given by injection, and/or compromised by the development of resistance. Since safe, effective, and affordable chemotherapeutic agents for leishmaniasis and trypanosomiasis are clearly needed, the identification of new antikinetoplastid drug candidates should be an urgent priority. Numerous plant-derived natural products from different structural classes have been investigated as antileishmanial and antitrypanosomal candidates, including various alkaloids, terpenoids, flavonoids, and quinonoids. This review outlines the antikinetoplastid activities of plant-derived natural products reported in the literature and also provides an overview of mechanistic studies that have been conducted with these compounds. Given the activities of these agents and their diverse range of effects on parasite biology, natural products are a potentially rich source of drug candidates and leads against leishmaniasis and trypanosomiasis.

  18. Clinical features, diagnosis, and treatment of human African trypanosomiasis (sleeping sickness).

    PubMed

    Kennedy, Peter Ge

    2013-02-01

    Human African trypanosomiasis, or sleeping sickness, is caused by infection with parasites of the genus Trypanosoma, transmitted by the tsetse fly. The disease has two forms, Trypanosoma brucei (T b) rhodesiense and T b gambiense; and is almost always fatal if untreated. Despite a recent reduction in the number of reported cases, patients with African trypanosomiasis continue to present major challenges to clinicians. Because treatment for CNS-stage disease can be very toxic, diagnostic staging to distinguish early-stage from late-stage disease when the CNS in invaded is crucial but remains problematic. Melarsoprol is the only available treatment for late-stage T b rhodesiense infection, but can be lethal to 5% of patients owing to post-treatment reactive encephalopathy. Eflornithine combined with nifurtimox is the first-line treatment for late-stage T b gambiense. New drugs are in the pipeline for treatment of CNS human African trypanosomiasis, giving rise to cautious optimism.

  19. Hyperlipidaemia in trypanosomiasis of naturally infected horses: possible cachexia-anorexia syndrome?

    PubMed

    Ranjithkumar, Muthusamy; Malik, Tauseef Ahmed; Saxena, Anju; Dan, Ananya; Sakthivel, Pillanatham Civalingam; Dey, Sahadeb

    2013-02-01

    Trypanosomiasis caused by Trypanosoma evansi commonly produces wasting disease with signs of emaciation and cachexia mainly at the end stage. The present study was conducted to explore the possible hyperlipaemia or hyperlipidaemia and its association with cachexia-anorexia in equine trypanosomiasis. Out of the fifteen confirmed animals, none of the plasma sample was opaque. There was a significant increase in plasma triglyceride, total cholesterol and blood urea nitrogen and a highly significant increase in low-density lipoprotein (LDL) levels. A mild increase in high-density lipoprotein (HDL) and very low-density lipoprotein levels were observed, while the relative percentage of HDL and LDL was altered with high significance. A moderate increase in triglyceride and highly significant increase in LDL might be the reasons for retention of appetite and lipolysis. Possible protein breakdown and presence of lipolysis might be the reasons for cachexia in equine trypanosomiasis.

  20. Compound control method of neutral point voltage of three level NPC inverter based on the vector method of virtual space and hysteresis control

    NASA Astrophysics Data System (ADS)

    Yang, Fengping; Xiao, Fangfei

    2017-03-01

    Current control methods include hardware control and software control corresponding to the inherent unbalance problem of neutral point voltage in three level NPC inverter. The hardware control is rarely used due to its high cost. In this paper, a new compound control method has been presented based on the vector method of virtual space and traditional hysteresis control of neutral point voltage, which can make up the shortcoming of the virtual control without the feedback control system of neutral point voltage and the blind area of hysteresis control and control the deviation and wave of neutral point voltage. The accuracy of this method has been demonstrated by simulation.

  1. Insecticide-treated plastic tarpaulins for control of malaria vectors in refugee camps.

    PubMed

    Graham, K; Mohammad, N; Rehman, H; Nazari, A; Ahmad, M; Kamal, M; Skovmand, O; Guillet, P; Allan, R; Zaim, M; Yates, A; Lines, J; Rowland, M

    2002-12-01

    Spraying of canvas tents with residual pyrethroid insecticide is an established method of malaria vector control in tented refugee camps. In recent years, plastic sheeting (polythene tarpaulins) has replaced canvas as the utilitarian shelter material for displaced populations in complex emergencies. Advances in technology enable polythene sheeting to be impregnated with pyrethroid during manufacture. The efficacy of such material against mosquitoes when erected as shelters under typical refugee camp conditions is unknown. Tests were undertaken with free-flying mosquitoes on entomological study platforms in an Afghan refugee camp to compare the insecticidal efficacy of plastic tarpaulin sprayed with deltamethrin on its inner surface (target dose 30 mg/m2), tarpaulin impregnated with deltamethrin (initially > or = 30 mg/m2) during manufacture, and a tent made from the factory impregnated tarpaulin material. Preliminary tests done in the laboratory with Anopheles stephensi Liston (Diptera: Culicidae) showed that 1-min exposure to factory-impregnated tarpaulins would give 100% mortality even after outdoor weathering in a temperate climate for 12 weeks. Outdoor platform tests with the erected materials (baited with human subjects) produced mosquito mortality rates between 86-100% for sprayed or factory-impregnated tarpaulins and tents (average approximately 40 anophelines and approximately 200 culicines/per platform/night), whereas control mortality (with untreated tarpaulin) was no more than 5%. Fewer than 20% of mosquitoes blood-fed on human subjects under either insecticide-treated or non-treated shelters. The tarpaulin shelter was a poor barrier to host-seeking mosquitoes and treatment with insecticide did not reduce the proportion blood-feeding. Even so, the deployment of insecticide-impregnated tarpaulins in refugee camps, if used by the majority of refugees, has the potential to control malaria by killing high proportions of mosquitoes and so reducing the average

  2. Sustainable vector control and management of Chagas disease in the Gran Chaco, Argentina.

    PubMed

    Gürtler, Ricardo E; Kitron, Uriel; Cecere, M Carla; Segura, Elsa L; Cohen, Joel E

    2007-10-09

    Chagas disease remains a serious obstacle to health and economic development in Latin America, especially for the rural poor. We report the long-term effects of interventions in rural villages in northern Argentina during 1984-2006. Two community-wide campaigns of residual insecticide spraying immediately and strongly reduced domestic infestation and infection with Trypanosoma cruzi in Triatoma infestans bugs and dogs and more gradually reduced the seroprevalence of children <15 years of age. Because no effective surveillance and control actions followed the first campaign in 1985, transmission resurged in 2-3 years. Renewed interventions in 1992 followed by sustained, supervised, community-based vector control largely suppressed the reestablishment of domestic bug colonies and finally led to the interruption of local human T. cruzi transmission. Human incidence of infection was nearly an order of magnitude higher in peripheral rural areas under pulsed, unsupervised, community-based interventions, where human transmission became apparent in 2000. The sustained, supervised, community-based strategy nearly interrupted domestic transmission to dogs but did not eliminate T. infestans despite the absence of pyrethroid-insecticide resistance. T. infestans persisted in part because of the lack of major changes in housing construction and quality. Sustained community participation grew out of establishing a trusted relationship with the affected communities and the local schools. The process included health promotion and community mobilization, motivation, and supervision in close cooperation with locally nominated leaders.

  3. Spray characterization of ultra-low-volume sprayers typically used in vector control.

    PubMed

    Hoffmann, W Clint; Walker, Todd W; Fritz, Bradley K; Farooq, Muhammad; Smith, Vincent L; Robinson, Cathy A; Szumlas, Dan; Lan, Yubin

    2009-09-01

    Numerous spray machines are used to apply pesticides for the control of human disease vectors, such as mosquitoes and flies, and the selection and setup of these machines significantly affects the level of control achieved during an application. The droplet spectra produced by 9 different ultra-low-volume sprayers with oil- and water-based spray solutions were evaluated along with 2 thermal foggers with the use of diesel-based spray solutions. The droplet spectra from the sprayers were measured with the use of laser diffraction droplet sizing equipment. The volume median diameter from the sprayers ranged from 14.8 to 61.9 microm for the oil-based spray solutions and 15.5 to 87.5 microm for the water-based spray solutions. The 2 thermal foggers generated sprays with a volume median diameter of 3.5 microm. The data presented will allow spray applicators to select the spray solution and sprayer that generate the droplet-size spectra that meet the desired specific spray application scenarios.

  4. Pneumatic motor powered Thrust Vector Control (TVC) for liquid propelled launch vehicles

    NASA Astrophysics Data System (ADS)

    Malone, Mark C.; Evans, P. S.

    1992-02-01

    Recent studies performed for the Titan 4 launch vehicle indicate significant potential advantages in replacing the current stage 1 and 2 recirculating hydraulic TVC (thrust vector control) system with a PMA (pneumatic mechanical actuation) system. Some of the advantages of a PMA system over the recirculating hydraulic system include reduced part count and weight, reduced maintenance and life-cycle cost, and improved mission reliability. PMA technology, used in aircraft applications since the 1960s, is well suited in launch vehicle TVC applications where an existing pneumatic pressure source is available. A typical pneumatic motor TVC consists of a pneumatic power source, a dual rotor pneumatic motor, a gear box, a ball screw actuator, and the associated closed-loop servo-control elements. One key issue with implementing this mechanical approach is designing a TVC system to withstand large load transient disturbances during liquid engine starting. Hydraulic actuator transient loads have exceeded 60,000 lb(sub f) for a 30,000 lb(sub f) stall design actuator during ground starts of the Titan 3B, Stage 1 engine. A PMA TVC system must also withstand these start transients without imparting excessive reaction loads to the engine nozzle and thrust structure. Work completed to date with Martin Marietta to examine pneumatic motor powered TVC options and technology benefits is presented. The load transient issue is discussed along with potential solutions and the associated trades. General background on PMA technology and experience base is also presented.

  5. Sustainable vector control and management of Chagas disease in the Gran Chaco, Argentina

    PubMed Central

    Gürtler, Ricardo E.; Kitron, Uriel; Cecere, M. Carla; Segura, Elsa L.; Cohen, Joel E.

    2007-01-01

    Chagas disease remains a serious obstacle to health and economic development in Latin America, especially for the rural poor. We report the long-term effects of interventions in rural villages in northern Argentina during 1984–2006. Two community-wide campaigns of residual insecticide spraying immediately and strongly reduced domestic infestation and infection with Trypanosoma cruzi in Triatoma infestans bugs and dogs and more gradually reduced the seroprevalence of children <15 years of age. Because no effective surveillance and control actions followed the first campaign in 1985, transmission resurged in 2–3 years. Renewed interventions in 1992 followed by sustained, supervised, community-based vector control largely suppressed the reestablishment of domestic bug colonies and finally led to the interruption of local human T. cruzi transmission. Human incidence of infection was nearly an order of magnitude higher in peripheral rural areas under pulsed, unsupervised, community-based interventions, where human transmission became apparent in 2000. The sustained, supervised, community-based strategy nearly interrupted domestic transmission to dogs but did not eliminate T. infestans despite the absence of pyrethroid-insecticide resistance. T. infestans persisted in part because of the lack of major changes in housing construction and quality. Sustained community participation grew out of establishing a trusted relationship with the affected communities and the local schools. The process included health promotion and community mobilization, motivation, and supervision in close cooperation with locally nominated leaders. PMID:17913895

  6. Influence of stimuli colour in SSVEP-based BCI wheelchair control using support vector machines.

    PubMed

    Singla, Rajesh; Khosla, Arun; Jha, Rameshwar

    2014-04-01

    This study aims to develop a Steady State Visual Evoked Potential (SSVEP)-based Brain Computer Interface (BCI) system to control a wheelchair, with improving accuracy as the major goal. The developed wheelchair can move in forward, backward, left, right and stop positions. Four different flickering frequencies in the low frequency region were used to elicit the SSVEPs and were displayed on a Liquid Crystal Display (LCD) monitor using LabVIEW. Four colours (green, red, blue and violet) were included in the study to investigate the colour influence in SSVEPs. The Electroencephalogram (EEG) signals recorded from the occipital region were first segmented into 1 s windows and features were extracted by using Fast Fourier Transform (FFT). Three different classifiers, two based on Artificial Neural Network (ANN) and one based on Support Vector Machine (SVM), were compared to yield better accuracy. Twenty subjects participated in the experiment and the accuracy was calculated by considering the number of correct detections produced while performing a pre-defined movement sequence. SSVEP with violet colour showed higher performance than green and red. The One-Against-All (OAA) based multi-class SVM classifier showed better accuracy than the ANN classifiers. The classification accuracy over 20 subjects varies between 75-100%, while information transfer rates (ITR) varies from 12.13-27 bpm for BCI wheelchair control with SSVEPs elicited by violet colour stimuli and classified using OAA-SVM.

  7. Monitoring the aquatic toxicity of mosquito vector control spray pesticides to freshwater receiving waters.

    PubMed

    Phillips, Bryn M; Anderson, Brian S; Voorhees, Jennifer P; Siegler, Katie; Denton, Debra; TenBrook, Patti; Larsen, Karen; Isorena, Philip; Tjeerdema, Ron S

    2014-07-01

    Pesticides are applied to state and local waterways in California to control insects such as mosquitoes, which are known to serve as a vector for West Nile Virus infection of humans. The California State Water Resources Control Board adopted a National Pollutant Discharge Elimination System General Permit to address the discharge to waters of the United States of pesticides resulting from adult and larval mosquito control. Because pesticides used in spray activities have the potential to cause toxicity to nontarget organisms in receiving waters, the current study was designed to determine whether toxicity testing provides additional, useful environmental risk information beyond chemical analysis in monitoring spray pesticide applications. Monitoring included a combination of aquatic toxicity tests and chemical analyses of receiving waters from agricultural, urban, and wetland habitats. The active ingredients monitored included the organophosphate pesticides malathion and naled, the pyrethroid pesticides etofenprox, permethrin, and sumithrin, pyrethrins, and piperonyl butoxide (PBO). Approximately 15% of the postapplication water samples were significantly toxic. Toxicity of half of these samples was attributed to the naled breakdown product dichlorvos. Toxicity of 2 other water samples likely occurred when PBO synergized the effects of pyrethroid pesticides that were likely present in the receiving system. Four of 43 postapplication sediment samples were significantly more toxic than their corresponding pre-application samples, but none of the observed toxicity was attributed to the application events. These results indicate that many of the spray pesticides used for adult mosquito control do not pose significant acute toxicity risk to invertebrates in receiving systems. In the case of naled in water, analysis of only the active ingredient underestimated potential impacts to the receiving system, because toxicity was attributed to the breakdown product, dichlorvos

  8. The Value of Information in Decision-Analytic Modeling for Malaria Vector Control in East Africa.

    PubMed

    Kim, Dohyeong; Brown, Zachary; Anderson, Richard; Mutero, Clifford; Miranda, Marie Lynn; Wiener, Jonathan; Kramer, Randall

    2016-03-23

    Decision analysis tools and mathematical modeling are increasingly emphasized in malaria control programs worldwide to improve resource allocation and address ongoing challenges with sustainability. However, such tools require substantial scientific evidence, which is costly to acquire. The value of information (VOI) has been proposed as a metric for gauging the value of reduced model uncertainty. We apply this concept to an evidenced-based Malaria Decision Analysis Support Tool (MDAST) designed for application in East Africa. In developing MDAST, substantial gaps in the scientific evidence base were identified regarding insecticide resistance in malaria vector control and the effectiveness of alternative mosquito control approaches, including larviciding. We identify four entomological parameters in the model (two for insecticide resistance and two for larviciding) that involve high levels of uncertainty and to which outputs in MDAST are sensitive. We estimate and compare a VOI for combinations of these parameters in evaluating three policy alternatives relative to a status quo policy. We find having perfect information on the uncertain parameters could improve program net benefits by up to 5-21%, with the highest VOI associated with jointly eliminating uncertainty about reproductive speed of malaria-transmitting mosquitoes and initial efficacy of larviciding at reducing the emergence of new adult mosquitoes. Future research on parameter uncertainty in decision analysis of malaria control policy should investigate the VOI with respect to other aspects of malaria transmission (such as antimalarial resistance), the costs of reducing uncertainty in these parameters, and the extent to which imperfect information about these parameters can improve payoffs.

  9. Development and assessment of plant-based synthetic odor baits for surveillance and control of Malaria vectors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent malaria vector control measures have considerably reduced indoor biting mosquito populations. However, reducing the outdoor biting populations remains a challenge because of the unavailability of appropriate lures to achieve this. This study sought to test the efficacy of plant-based syntheti...

  10. The evolution of ocular onchocerciasis in the Volta River Basin Area over a period of five years of vector control.

    PubMed

    Dadzie, K Y; Rolland, A; Thylefors, B

    1984-03-01

    The results of an ophthalmological evaluation conducted in seven West African savannah villages before and after 5 years of vector control, were analysed to determine the effect of an interrupted or greatly reduced transmission of Onchocerca volvulus on the evolution of ocular onchocerciasis. Cross-sectional data showed a significant reduction of the prevalence of ocular onchocerciasis in five of the villages, and the rates of irreversible ocular lesions and blindness were generally lower after 5 years of vector control. A longitudinal study of a defined population showed that the ocular status of most patients with ocular onchocerciasis remained stable or improved over the 5 year period, particularly in lightly infected cases. The evolution of ocular onchocerciasis showed a deterioration in a minor proportion, restricted to cases of already existing severe lesions, resulting in blindness. A comparison of ophthalmic data from adjacent areas without vector control, indicates that a five year period of vector control may reduce the risk of developing eye lesions or blindness due to onchocerciasis by 50%.

  11. Declining malaria, rising of dengue and Zika virus: insights for mosquito vector control.

    PubMed

    Benelli, Giovanni; Mehlhorn, Heinz

    2016-05-01

    The fight against mosquito-borne diseases is a challenge of huge public health importance. To our mind, 2015 was an extraordinary year for malaria control, due to three hot news: the Nobel Prize to Youyou Tu for the discovery of artemisinin, the development of the first vaccine against Plasmodium falciparum malaria [i.e. RTS,S/AS01 (RTS,S)], and the fall of malaria infection rates worldwide, with special reference to sub-Saharan Africa. However, there are major challenges that still deserve attention, in order to boost malaria prevention and control. Indeed, parasite strains resistant to artemisinin have been detected, and RTS,S vaccine does not offer protection against Plasmodium vivax malaria, which predominates in many countries outside of Africa. Furthermore, the recent outbreaks of Zika virus infections, occurring in South America, Central America and the Caribbean, represent the most recent of four arrivals of important arboviruses in the Western Hemisphere, over the last 20 years. Zika virus follows dengue (which slyly arrived in the hemisphere over decades and became more aggressive in the 1990s), West Nile virus (emerged in 1999) and chikungunya (emerged in 2013). Notably, there are no specific treatments for these arboviruses. The emerging scenario highlights that the effective and eco-friendly control of mosquito vectors, with special reference to highly invasive species such as Aedes aegypti and Aedes albopictus, is crucial. The concrete potential of screening plant species as sources of metabolites for parasitological purposes is worthy of attention, as elucidated by the Y. Tu's example. Notably, plant-borne molecules are often effective at few parts per million against Aedes, Ochlerotatus, Anopheles and Culex young instars, can be used for the rapid synthesis of mosquitocidal nanoformulations and even employed to prepare cheap repellents with low human toxicity. In addition, behaviour-based control tools relying to the employ of sound traps and the

  12. Independent Orbiter Assessment (IOA): Assessment of the ascent thrust vector control actuator subsystem FMEA/CIL

    NASA Technical Reports Server (NTRS)

    Wilson, R. E.

    1988-01-01

    The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Ascent Thrust Vector Control Actuator (ATVD) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy from the comparison is provided through additional analysis as required. This report documents the results of that comparison for the Orbiter ATVC hardware. The IOA product for the ATVC actuator analysis consisted of 25 failure mode worksheets that resulted in 16 potential critical items being identified. Comparison was made to the NASA baseline which consisted of 21 FMEAs and 13 CIL items. This comparison produced agreement on all CIL items. Based on the Pre 51-L baseline, all non-CIL FMEAs were also in agreement.

  13. Application of Diagnostic Analysis Tools to the Ares I Thrust Vector Control System

    NASA Technical Reports Server (NTRS)

    Maul, William A.; Melcher, Kevin J.; Chicatelli, Amy K.; Johnson, Stephen B.

    2010-01-01

    The NASA Ares I Crew Launch Vehicle is being designed to support missions to the International Space Station (ISS), to the Moon, and beyond. The Ares I is undergoing design and development utilizing commercial-off-the-shelf tools and hardware when applicable, along with cutting edge launch technologies and state-of-the-art design and development. In support of the vehicle s design and development, the Ares Functional Fault Analysis group was tasked to develop an Ares Vehicle Diagnostic Model (AVDM) and to demonstrate the capability of that model to support failure-related analyses and design integration. One important component of the AVDM is the Upper Stage (US) Thrust Vector Control (TVC) diagnostic model-a representation of the failure space of the US TVC subsystem. This paper first presents an overview of the AVDM, its development approach, and the software used to implement the model and conduct diagnostic analysis. It then uses the US TVC diagnostic model to illustrate details of the development, implementation, analysis, and verification processes. Finally, the paper describes how the AVDM model can impact both design and ground operations, and how some of these impacts are being realized during discussions of US TVC diagnostic analyses with US TVC designers.

  14. Habitat Hydrology and Geomorphology Control the Distribution of Malaria Vector Larvae in Rural Africa

    PubMed Central

    Hardy, Andrew J.; Gamarra, Javier G. P.; Cross, Dónall E.; Macklin, Mark G.; Smith, Mark W.; Kihonda, Japhet; Killeen, Gerry F.; Ling’ala, George N.; Thomas, Chris J.

    2013-01-01

    Background Larval source management is a promising component of integrated malaria control and elimination. This requires development of a framework to target productive locations through process-based understanding of habitat hydrology and geomorphology. Methods We conducted the first catchment scale study of fine resolution spatial and temporal variation in Anopheles habitat and productivity in relation to rainfall, hydrology and geomorphology for a high malaria transmission area of Tanzania. Results Monthly aggregates of rainfall, river stage and water table were not significantly related to the abundance of vector larvae. However, these metrics showed strong explanatory power to predict mosquito larval abundances after stratification by water body type, with a clear seasonal trend for each, defined on the basis of its geomorphological setting and origin. Conclusion Hydrological and geomorphological processes governing the availability and productivity of Anopheles breeding habitat need to be understood at the local scale for which larval source management is implemented in order to effectively target larval source interventions. Mapping and monitoring these processes is a well-established practice providing a tractable way forward for developing important malaria management tools. PMID:24312606

  15. Linear Test Bed. Volume 2: Test Bed No. 2. [linear aerospike test bed for thrust vector control

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Test bed No. 2 consists of 10 combustors welded in banks of 5 to 2 symmetrical tubular nozzle assemblies, an upper stationary thrust frame, a lower thrust frame which can be hinged, a power package, a triaxial combustion wave ignition system, a pneumatic control system, pneumatically actuated propellant valves, a purge and drain system, and an electrical control system. The power package consists of the Mark 29-F fuel turbopump, the Mark 29-0 oxidizer turbopump, a gas generator assembly, and propellant ducting. The system, designated as a linear aerospike system, was designed to demonstrate the feasibility of the concept and to explore technology related to thrust vector control, thrust vector optimization, improved sequencing and control, and advanced ignition systems. The propellants are liquid oxygen/liquid hydrogen. The system was designed to operate at 1200-psia chamber pressure at an engine mixture ratio of 5.5. With 10 combustors, the sea level thrust is 95,000 pounds.

  16. RNA interference in mosquito: understanding immune responses, double-stranded RNA delivery systems and potential applications in vector control.

    PubMed

    Balakrishna Pillai, A; Nagarajan, U; Mitra, A; Krishnan, U; Rajendran, S; Hoti, S L; Mishra, R K

    2017-04-01

    RNA interference (RNAi) refers to the process of post-transcriptional silencing of cellular mRNA by the application of double-stranded RNA (dsRNA). RNAi strategies have been widely employed to regulate gene expression in plants and animals including insects. With the availability of the full genome sequences of major vector mosquitoes, RNAi has been increasingly used to conduct genetic studies of human pathogens in mosquito vectors and to study the evolution of insecticide resistance in mosquitoes. This review summarizes the recent progress in our understanding of mosquito-pathogen interactions using RNAi and various methods of dsRNA delivery in mosquitoes at different stages. We also discuss potential applications of this technology to develop novel tools for vector control.

  17. Control of tripod-scheme cold-atom wavepackets by manipulating a non-Abelian vector potential

    SciTech Connect

    Zhang Qi; Gong Jiangbin; Oh, C.H.

    2010-06-15

    Tripod-scheme cold atoms interacting with laser beams have attracted considerable interest for their role in synthesizing effective non-Abelian vector potentials. Such effective vector potentials can be exploited to realize an all-optical imprinting of geometric phases onto matter waves. By working on carefully designed extensions of our previous work, we show that coherent lattice structure of cold-atom sub-wavepackets can be formed and that the non-Abelian Aharonov-Bohm effect can be easily manifested via the translational motion of cold atoms. We also show that by changing the frame of reference, effects due to a non-Abelian vector potential may be connected with a simple dynamical phase effect, and that under certain conditions it can be understood as an Abelian geometric phase in a different frame of reference. Results should help design better schemes for the control of cold-atom matter waves.

  18. Two step male release strategy using transgenic mosquito lines to control transmission of vector-borne diseases.

    PubMed

    Carvalho, Danilo Oliveira; Costa-da-Silva, André Luis; Lees, Rosemary Susan; Capurro, Margareth Lara

    2014-04-01

    Mosquitoes are responsible for the transmission of pathogens that cause devastating human diseases such as malaria and dengue. The current increase in mean global temperature and changing sea level interfere with precipitation frequency and some other climatic conditions which, in general, influence the rate of development of insects and etiologic agents causing acceleration as the temperature rises. The most common strategy employed to combat target mosquito species is the Integrated Vector Management (IVM), which comprises the use of multiple activities and various approaches to preventing the spread of a vector in infested areas. IVM programmes are becoming ineffective; and the global scenario is threatening, requiring new interventions for vector control and surveillance. Not surprisingly, there is a growing need to find alternative methods to combat the mosquito vectors. The possibility of using transgenic mosquitoes to fight against those diseases has been discussed over the last two decades and this use of transgenic lines to suppress populations or to replace them is still under investigation through field and laboratory trials. As an alternative, the available transgenic strategies could be improved by coupling suppression and substitution strategies. The idea is to first release a suppression line to significantly reduce the wild population, and once the first objective is reached a second release using a substitution line could be then performed. Examples of targeting this approach against vectors of malaria and dengue are discussed.

  19. [Use of insecticide-treated cattle to control Rift Valley fever and West Nile virus vectors in Senegal].

    PubMed

    Diallo, D; Ba, Y; Dia, I; Lassana, K; Diallo, M

    2008-12-01

    Rift Valley Fever (RVF) and West Nile fever (WN) viruses are transmitted by several mosquito species and share the same vectors in Northern Senegal (West Africa). In absence of an effective treatment and vaccines, vector control remains an alternative method of prevention and control of these vector-borne diseases. The methods targeting adults' pest mosquitoes and malaria vectors which are currently used by the population in the Barkedji area (insecticides treated nets, bombs and copper coil) would not be effective against these vectors because of their exophagic and zoophilic behavior. Thus, we decided to evaluate the effectiveness of insecticide-treated cattle as a method to control these vectors. We evaluated the effects of this treatment on the mortality and the behaviour (attractiveness and engorgement) of the main vectors and subsidiary the whole mosquito fauna. Our study was conducted during September 2005, and between July and November 2006, at Niakha pond located 4 km from the Barkedji village in the Sahelian region of Senegal. A bull-calf was treated with 25 mg/m2 of deltamethrin and compared to an untreated calf of the same weight used as a control. The assays were conducted using two net-traps placed at the edge of the pond from 19:00 PM to 22:00 PM each night for 4 nights per week for 4 consecutive weeks after each treatment. The risk that host- seeking mosquitoes that do not have possibility to feed on cattle might turn to men cohabiting with these cattle was evaluated simultaneously during the bioassay. The deltamethrin treatment led to a significant reduction in the average number of mosquitoes attracted by the treated-calf compared to the control during the first 2 weeks post-treatment both for all species and for the main vectors such as Ae. vexans, Ae. ochraceus, Cx. poicilipes, Cx. neavei and Ma. uniformis. However these means were comparable for the last two weeks post-treatment both for the whole mosquito fauna and the main vectors with the

  20. Inductance and Active Phase Vector Based Torque Control for Switched Reluctance Motor Drives.

    NASA Astrophysics Data System (ADS)

    Kalpathi, Ramani Raman

    The Switched Reluctance Motor (SRM) drive technology has developed significantly over the last few years. The simplicity in both motor design and power converter requirement along with the availability of high frequency, high power semiconductor switches have made SRMs compete with conventional adjustable speed drive technologies. The subject of winding current control in switched reluctance machines has always been associated with the shaft position information. The use of inductance for direct commutation control is the central subject of this dissertation. In contrast to the conventional methods based on position commutation, new methods of control based on inductance commutation are presented. The object of a commutation algorithm is to switch the currents in the phase coils, in order to provide continuous energy conversion with maximum torque output for a given unit of input current. Since torque production in a SRM is based on the concept of variable reluctance, it makes more sense to observe the instantaneous phase inductance or reluctance instead of estimating the rotor position. The inductance sensors observe the machine parameters and provide sufficient information on the electrical characteristics of the coils. This control strategy avoids the inductance to position transformation blocks conventionally used in SRM control systems. In a typical SRM, the phase coils have a nonlinear behavior of inductance due to effects of current saturation. Also the parameters of one phase coil differ from those of the other due to manufacturing tolerances or due to bearing wear. In such cases, the algorithms written during the stage of manufacturing may not be valid after parameter changes. Optimizing torque production in the event of phase asymmetry and saturation is developed in this research. Indirect sensors connected to the active phase coil of the SRM are based on sensing the flux level in the active coil. New commutation algorithms based on flux sensing concepts

  1. Computational Study of Fluidic Thrust Vectoring using Separation Control in a Nozzle

    NASA Technical Reports Server (NTRS)

    Deere, Karen; Berrier, Bobby L.; Flamm, Jeffrey D.; Johnson, Stuart K.

    2003-01-01

    A computational investigation of a two- dimensional nozzle was completed to assess the use of fluidic injection to manipulate flow separation and cause thrust vectoring of the primary jet thrust. The nozzle was designed with a recessed cavity to enhance the throat shifting method of fluidic thrust vectoring. The structured-grid, computational fluid dynamics code PAB3D was used to guide the design and analyze over 60 configurations. Nozzle design variables included cavity convergence angle, cavity length, fluidic injection angle, upstream minimum height, aft deck angle, and aft deck shape. All simulations were computed with a static freestream Mach number of 0.05. a nozzle pressure ratio of 3.858, and a fluidic injection flow rate equal to 6 percent of the primary flow rate. Results indicate that the recessed cavity enhances the throat shifting method of fluidic thrust vectoring and allows for greater thrust-vector angles without compromising thrust efficiency.

  2. Trypanosomiasis:goats as a possible reservoir of Trypanosoma congolense in the Republic of the Sudan.

    PubMed

    Mahmoud, M M; Elmalik, K H

    1977-08-01

    Experimental Trypanosoma congolense infections of goats and calves were compared. Goats developed a chronic form of trypanosomiasis, often recovering spontaneously from a strain which caused an acute fatal disease in calves. Goats may be important in the maintenace of T. congolense in nature in the Sudan.

  3. West-African trypanosomiasis in a returned traveller from Ghana: an unusual cause of progressive neurological decline.

    PubMed

    Elliott, Ivo; Patel, Trupti; Shah, Jagrit; Venkatesan, Pradhib

    2014-08-14

    West-African trypanosomiasis caused by Trypanosoma brucei gambiense is a rare imported infection presenting with somnolence, lymphadenopathy and wide-ranging neurological symptoms. A 67-year-old Caucasian man presented with a 10-month history of cognitive deterioration, ataxic gait, somnolence and urinary incontinence. His symptoms had progressed more rapidly over the course of a month prior to admission. Serological testing confirmed a diagnosis of West-African trypanosomiasis. The patient was successfully treated with eflornithine and made a good recovery. West-African trypanosomiasis should be considered in the differential diagnosis of unexplained cognitive decline in those with a relevant travel history. If left untreated, the condition is universally fatal.

  4. Genome Investigations of Vector Competence in Aedes aegypti to Inform Novel Arbovirus Disease Control Approaches.

    PubMed

    Severson, David W; Behura, Susanta K

    2016-10-30

    Dengue (DENV), yellow fever, chikungunya, and Zika virus transmission to humans by a mosquito host is confounded by both intrinsic and extrinsic variables. Besides virulence factors of the individual arboviruses, likelihood of virus transmission is subject to variability in the genome of the primary mosquito vector, Aedes aegypti. The "vectorial capacity" of A. aegypti varies depending upon its density, biting rate, and survival rate, as well as its intrinsic ability to acquire, host and transmit a given arbovirus. This intrinsic ability is known as "vector competence". Based on whole transcriptome analysis, several genes and pathways have been predicated to have an association with a susceptible or refractory response in A. aegypti to DENV infection. However, the functional genomics of vector competence of A. aegypti is not well understood, primarily due to lack of integrative approaches in genomic or transcriptomic studies. In this review, we focus on the present status of genomics studies of DENV vector competence in A. aegypti as limited information is available relative to the other arboviruses. We propose future areas of research needed to facilitate the integration of vector and virus genomics and environmental factors to work towards better understanding of vector competence and vectorial capacity in natural conditions.

  5. Genome Investigations of Vector Competence in Aedes aegypti to Inform Novel Arbovirus Disease Control Approaches

    PubMed Central

    Severson, David W.; Behura, Susanta K.

    2016-01-01

    Dengue (DENV), yellow fever, chikungunya, and Zika virus transmission to humans by a mosquito host is confounded by both intrinsic and extrinsic variables. Besides virulence factors of the individual arboviruses, likelihood of virus transmission is subject to variability in the genome of the primary mosquito vector, Aedes aegypti. The “vectorial capacity” of A. aegypti varies depending upon its density, biting rate, and survival rate, as well as its intrinsic ability to acquire, host and transmit a given arbovirus. This intrinsic ability is known as “vector competence”. Based on whole transcriptome analysis, several genes and pathways have been predicated to have an association with a susceptible or refractory response in A. aegypti to DENV infection. However, the functional genomics of vector competence of A. aegypti is not well understood, primarily due to lack of integrative approaches in genomic or transcriptomic studies. In this review, we focus on the present status of genomics studies of DENV vector competence in A. aegypti as limited information is available relative to the other arboviruses. We propose future areas of research needed to facilitate the integration of vector and virus genomics and environmental factors to work towards better understanding of vector competence and vectorial capacity in natural conditions. PMID:27809220

  6. Simulation development and evaluation of an improved longitudinal velocity vector control wheel steering mode and electronic display format

    NASA Technical Reports Server (NTRS)

    Steinmetz, G. G.

    1980-01-01

    Using simulation, an improved longitudinal velocity vector control wheel steering mode and an improved electronic display format for an advanced flight system were developed and tested. Guidelines for the development phase were provided by test pilot critique summaries of the previous system. The results include performances from computer generated step column inputs across the full airplane speed and configuration envelope, as well as piloted performance results taken from a reference line tracking task and an approach to landing task conducted under various environmental conditions. The analysis of the results for the reference line tracking and approach to landing tasks indicates clearly detectable improvement in pilot tracking accuracy with a reduction in physical workload. The original objectives of upgrading the longitudinal axis of the velocity vector control wheel steering mode were successfully met when measured against the test pilot critique summaries and the original purpose outlined for this type of augment control mode.

  7. Public Health Interventions for Aedes Control in the Time of Zikavirus– A Meta-Review on Effectiveness of Vector Control Strategies

    PubMed Central

    Bouzid, Maha; Brainard, Julii; Hooper, Lee; Hunter, Paul R.

    2016-01-01

    Background There is renewed interest in effective measures to control Zika and dengue vectors. A synthesis of published literature with a focus on the quality of evidence is warranted to determine the effectiveness of vector control strategies. Methodology We conducted a meta-review assessing the effectiveness of any Aedes control measure. We searched Scopus and Medline for relevant reviews through to May 2016. Titles, abstracts and full texts were assessed independently for inclusion by two authors. Data extraction was performed in duplicate and validity of the evidence was assessed using GRADE criteria. Findings 13 systematic reviews that investigated the effect of control measures on entomological parameters or disease incidence were included. Biological controls seem to achieve better reduction of entomological indices than chemical controls, while educational campaigns can reduce breeding habitats. Integrated vector control strategies may not always increase effectiveness. The efficacy of any control programme is dependent on local settings, intervention type, resources and study duration, which may partly explain the varying degree of success between studies. Nevertheless, the quality of evidence was mostly low to very low due to poor reporting of study design, observational methodologies, heterogeneity, and indirect outcomes, thus hindering an evidence-based recommendation. Conclusions The evidence for the effectiveness of Aedes control measures is mixed. Chemical control, which is commonly used, does not appear to be associated with sustainable reductions of mosquito populations over time. Indeed, by contributing to a false sense of security, chemical control may reduce the effectiveness of educational interventions aimed at encouraging local people to remove mosquito breeding sites. Better quality studies of the impact of vector control interventions on the incidence of human infections with Dengue or Zika are still needed. PMID:27926934

  8. Chemical and environmental vector control as a contribution to the elimination of visceral leishmaniasis on the Indian subcontinent: cluster randomized controlled trials in Bangladesh, India and Nepal

    PubMed Central

    Joshi, Anand B; Das, Murari L; Akhter, Shireen; Chowdhury, Rajib; Mondal, Dinesh; Kumar, Vijay; Das, Pradeep; Kroeger, Axel; Boelaert, Marleen; Petzold, Max

    2009-01-01

    Background Bangladesh, India and Nepal are working towards the elimination of visceral leishmaniasis (VL) by 2015. In 2005 the World Health Organization/Training in Tropical Diseases launched an implementation research programme to support integrated vector management for the elimination of VL from Bangladesh, India and Nepal. The programme is conducted in different phases, from proof-of-concept to scaling up intervention. This study was designed in order to evaluate the efficacy of the three different interventions for VL vector management: indoor residual spraying (IRS); long-lasting insecticide treated nets (LLIN); and environmental modification (EVM) through plastering of walls with lime or mud. Methods Using a cluster randomized controlled trial we compared three vector control interventions with a control arm in 96 clusters (hamlets or neighbourhoods) in each of the 4 study sites: Bangladesh (one), India (one) and Nepal (two). In each site four villages with high reported VL incidences were included. In each village six clusters and in each cluster five households were randomly selected for sand fly collection on two consecutive nights. Control and intervention clusters were matched with average pre-intervention vector densities. In each site six clusters were randomly assigned to each of the following interventions: indoor residual spraying (IRS); long-lasting insecticide treated nets (LLIN); environmental management (EVM) or control. All the houses (50-100) in each intervention cluster underwent the intervention measures. A reduction of intra-domestic sand fly densities measured in the study households by overnight US Centres for Disease Prevention and Control light trap captures (that is the number of sand flies per trap per night) was the main outcome measure. Results IRS, and to a lesser extent EVM and LLINs, significantly reduced sand fly densities for at least 5 months in the study households irrespective of type of walls or whether or not people

  9. Qualitative evaluation of chromatographic data from quality control schemes using a support vector machine.

    PubMed

    Ventura, M; Sanchez-Niubo, A; Ruiz, F; Agell, N; Ventura, R; Angulo, C; Domingo-Salvany, A; Segura, J; Torre, R de la

    2008-01-01

    The qualitative evaluation of chromatographic data in the framework of external quality assurance schemes is considered in this paper. The homogeneity in the evaluation of chromatographic data among human experts in samples with analytes close to the limit of detection of analytical methods was examined and also a Support Vector Machine (SVM) was developed as an alternative to experts for a more homogeneous and automatic evaluation. A set of 105 ion chromatograms obtained by anti-doping control laboratories was used in this study. The quality of the ion chromatograms was evaluated qualitatively by nine independent experts (associating a score from 0 to 4) and also more objectively taking into account chromatographic parameters (peak width, asymmetry, resolution and S/N ratio). Results obtained showed a high degree of variability among experts when judging ion chromatograms. Experts applying extremely outlying evaluation criteria were identified and excluded from the data used to develop the SVM. This machine was built providing the system with qualitative information (scores assigned by experts) and with objective data (parameters) of the ion chromatograms. A seven-fold cross-validation approach was used to train and to evaluate the predictive ability of the machine. According to the results obtained, the SVM developed was found to be close to the reasoning process followed by the homogeneous human expert group. This machine also could provide a scoring system to sort laboratories according to the quality of their results. The qualitative evaluation of analytical records using a scoring system allowed the identification of the main factors affecting the quality of chromatographic analytical data, such as the specific analytical technique applied and the adherence to guidelines for reporting positive results.

  10. Unexpected Failures to Control Chagas Disease Vectors With Pyrethroid Spraying in Northern Argentina

    PubMed Central

    Gurevitz, J. M.; Gaspe, M. S.; Enríquez, G. F.; Vassena, C. V.; Alvarado-Otegui, J. A.; Provecho, Y. M.; Mougabure Cueto, G. A; Picollo, M. I.; Kitron, U.; Gürtler, R. E.

    2013-01-01

    Effectiveness of the elimination efforts against Triatoma infestans (Klug) in South America through residual application of pyrethroid insecticides has been highly variable in the Gran Chaco region. We investigated apparent vector control failures after a standard community-wide spraying with deltamethrin SC in a rural area of northeastern Argentina encompassing 353 houses. Insecticide spraying reduced house infestation less than expected: from 49.5% at baseline to 12.3 and 6.7% at 4 and 8 mo postspraying, respectively. Persistent infestations were detected in 28.4% of houses, and numerous colonies with late-stage bugs were recorded after the interventions. Laboratory bioassays showed reduced susceptibility to pyrethroids in the local bug populations. Eleven of 14 bug populations showed reduced mortality in diagnostic dose assays (range, 35 ± 5% to 97 ± 8%) whereas the remainder had 100% mortality. A fully enclosed residual bug population in a large chicken coop survived four pyrethroid sprays, including two double-dose applications, and was finally suppressed with malathion. The estimated resistance ratio of this bug population was 7.17 (range, 4.47–11.50). Our field data combined with laboratory bioassays and a residual foci experiment demonstrate that the initial failure to suppress T. infestans was mainly because of the unexpected occurrence of reduced susceptibility to deltamethrin in an area last treated with pyrethroid insecticides 12 yr earlier. Our results underline the need for close monitoring of the impact of insecticide spraying to provide early warning of possible problems due to enhanced resistance or tolerance and determine appropriate responses. PMID:23270166

  11. Application of eco-friendly tools and eco-bio-social strategies to control dengue vectors in urban and peri-urban settings in Thailand

    PubMed Central

    Kittayapong, Pattamaporn; Thongyuan, Suporn; Olanratmanee, Phanthip; Aumchareoun, Worawit; Koyadun, Surachart; Kittayapong, Rungrith; Butraporn, Piyarat

    2012-01-01

    Background Dengue is considered one of the most important vector-borne diseases in Thailand. Its incidence is increasing despite routine implementation of national dengue control programmes. This study, conducted during 2010, aimed to demonstrate an application of integrated, community-based, eco-bio-social strategies in combination with locally-produced eco-friendly vector control tools in the dengue control programme, emphasizing urban and peri-urban settings in eastern Thailand. Methodology Three different community settings were selected and were randomly assigned to intervention and control clusters. Key community leaders and relevant governmental authorities were approached to participate in this intervention programme. Ecohealth volunteers were identified and trained in each study community. They were selected among active community health volunteers and were trained by public health experts to conduct vector control activities in their own communities using environmental management in combination with eco-friendly vector control tools. These trained ecohealth volunteers carried out outreach health education and vector control during household visits. Management of public spaces and public properties, especially solid waste management, was efficiently carried out by local municipalities. Significant reduction in the pupae per person index in the intervention clusters when compared to the control ones was used as a proxy to determine the impact of this programme. Results Our community-based dengue vector control programme demonstrated a significant reduction in the pupae per person index during entomological surveys which were conducted at two-month intervals from May 2010 for the total of six months in the intervention and control clusters. The programme also raised awareness in applying eco-friendly vector control approaches and increased intersectoral and household participation in dengue control activities. Conclusion An eco-friendly dengue vector control

  12. Lethal and Pre-Lethal Effects of a Fungal Biopesticide Contribute to Substantial and Rapid Control of Malaria Vectors

    PubMed Central

    Blanford, Simon; Shi, Wangpeng; Christian, Riann; Marden, James H.; Koekemoer, Lizette L.; Brooke, Basil D.; Coetzee, Maureen; Read, Andrew F.; Thomas, Matthew B.

    2011-01-01

    Rapidly emerging insecticide resistance is creating an urgent need for new active ingredients to control the adult mosquitoes that vector malaria. Biopesticides based on the spores of entomopathogenic fungi have shown considerable promise by causing very substantial mortality within 7–14 days of exposure. This mortality will generate excellent malaria control if there is a high likelihood that mosquitoes contact fungi early in their adult lives. However, where contact rates are lower, as might result from poor pesticide coverage, some mosquitoes will contact fungi one or more feeding cycles after they acquire malaria, and so risk transmitting malaria before the fungus kills them. Critics have argued that ‘slow acting’ fungal biopesticides are, therefore, incapable of delivering malaria control in real-world contexts. Here, utilizing standard WHO laboratory protocols, we demonstrate effective action of a biopesticide much faster than previously reported. Specifically, we show that transient exposure to clay tiles sprayed with a candidate biopesticide comprising spores of a natural isolate of Beauveria bassiana, could reduce malaria transmission potential to zero within a feeding cycle. The effect resulted from a combination of high mortality and rapid fungal-induced reduction in feeding and flight capacity. Additionally, multiple insecticide-resistant lines from three key African malaria vector species were completely susceptible to fungus. Thus, fungal biopesticides can block transmission on a par with chemical insecticides, and can achieve this where chemical insecticides have little impact. These results support broadening the current vector control paradigm beyond fast-acting chemical toxins. PMID:21897846

  13. Functional and biodegradable dendritic macromolecules with controlled architectures as nontoxic and efficient nanoscale gene vectors.

    PubMed

    Luo, Kui; He, Bin; Wu, Yao; Shen, Youqing; Gu, Zhongwei

    2014-01-01

    Gene therapy has provided great potential to revolutionize the treatment of many diseases. This therapy is strongly relied on whether a delivery vector efficiently and safely directs the therapeutic genes into the target tissue/cells. Nonviral gene delivery vectors have been emerging as a realistic alternative to the use of viral analogs with the potential of a clinically relevant output. Dendritic polymers were employed as nonviral vectors due to their branched and layered architectures, globular shape and multivalent groups on their surface, showing promise in gene delivery. In the present review, we try to bring out the recent trend of studies on functional and biodegradable dendritic polymers as nontoxic and efficient gene delivery vectors. By regulating dendritic polymer design and preparation, together with recent progress in the design of biodegradable polymers, it is possible to precisely manipulate their architectures, molecular weight and chemical composition, resulting in predictable tuning of their biocompatibility as well as gene transfection activities. The multifunctional and biodegradable dendritic polymers possessing the desirable characteristics are expected to overcome extra- and intracellular obstacles, and as efficient and nontoxic gene delivery vectors to move into the clinical arena.

  14. Selective inhibition of RNA polymerase I transcription as a potential approach to treat African trypanosomiasis

    PubMed Central

    Kerry, Louise E.; Pegg, Elaine E.; Cameron, Donald P.; Budzak, James; Poortinga, Gretchen; Hannan, Katherine M.; Hannan, Ross D.

    2017-01-01

    Trypanosoma brucei relies on an essential Variant Surface Glycoprotein (VSG) coat for survival in the mammalian bloodstream. High VSG expression within an expression site body (ESB) is mediated by RNA polymerase I (Pol I), which in other eukaryotes exclusively transcribes ribosomal RNA genes (rDNA). As T. brucei is reliant on Pol I for VSG transcription, we investigated Pol I transcription inhibitors for selective anti-trypanosomal activity. The Pol I inhibitors quarfloxin (CX-3543), CX-5461, and BMH-21 are currently under investigation for treating cancer, as rapidly dividing cancer cells are particularly dependent on high levels of Pol I transcription compared with nontransformed cells. In T. brucei all three Pol I inhibitors have IC50 concentrations for cell proliferation in the nanomolar range: quarfloxin (155 nM), CX-5461 (279 nM) or BMH-21 (134 nM) compared with IC50 concentrations in the MCF10A human breast epithelial cell line (4.44 μM, 6.89 μM or 460 nM, respectively). T. brucei was therefore 29-fold more sensitive to quarfloxin, 25-fold more sensitive to CX-5461 and 3.4-fold more sensitive to BMH-21. Cell death in T. brucei was due to rapid inhibition of Pol I transcription, as within 15 minutes treatment with the inhibitors rRNA precursor transcript was reduced 97-98% and VSG precursor transcript 91-94%. Incubation with Pol I transcription inhibitors also resulted in disintegration of the ESB as well as the nucleolus subnuclear structures, within one hour. Rapid ESB loss following the block in Pol I transcription argues that the ESB is a Pol I transcription nucleated structure, similar to the nucleolus. In addition to providing insight into Pol I transcription and ES control, Pol I transcription inhibitors potentially also provide new approaches to treat trypanosomiasis. PMID:28263991

  15. Selective inhibition of RNA polymerase I transcription as a potential approach to treat African trypanosomiasis.

    PubMed

    Kerry, Louise E; Pegg, Elaine E; Cameron, Donald P; Budzak, James; Poortinga, Gretchen; Hannan, Kate; Hannan, Ross D; Rudenko, Gloria

    2017-03-06

    Trypanosoma brucei relies on an essential Variant Surface Glycoprotein (VSG) coat for survival in the mammalian bloodstream. High VSG expression within an expression site body (ESB) is mediated by RNA polymerase I (Pol I), which in other eukaryotes exclusively transcribes ribosomal RNA genes (rDNA). As T. brucei is reliant on Pol I for VSG transcription, we investigated Pol I transcription inhibitors for selective anti-trypanosomal activity. The Pol I inhibitors quarfloxin (CX-3543), CX-5461, and BMH-21 are currently under investigation for treating cancer, as rapidly dividing cancer cells are particularly dependent on high levels of Pol I transcription compared with nontransformed cells. In T. brucei all three Pol I inhibitors have IC50 concentrations for cell proliferation in the nanomolar range: quarfloxin (155 nM), CX-5461 (279 nM) or BMH-21 (134 nM) compared with IC50 concentrations in the MCF10A human breast epithelial cell line (4.44 μM, 6.89 μM or 460 nM, respectively). T. brucei was therefore 29-fold more sensitive to quarfloxin, 25-fold more sensitive to CX-5461 and 3.4-fold more sensitive to BMH-21. Cell death in T. brucei was due to rapid inhibition of Pol I transcription, as within 15 minutes treatment with the inhibitors rRNA precursor transcript was reduced 97-98% and VSG precursor transcript 91-94%. Incubation with Pol I transcription inhibitors also resulted in disintegration of the ESB as well as the nucleolus subnuclear structures, within one hour. Rapid ESB loss following the block in Pol I transcription argues that the ESB is a Pol I transcription nucleated structure, similar to the nucleolus. In addition to providing insight into Pol I transcription and ES control, Pol I transcription inhibitors potentially also provide new approaches to treat trypanosomiasis.

  16. Metabolomics Identifies Multiple Candidate Biomarkers to Diagnose and Stage Human African Trypanosomiasis

    PubMed Central

    Vincent, Isabel M.; Daly, Rónán; Courtioux, Bertrand; Cattanach, Amy M.; Biéler, Sylvain; Ndung’u, Joseph M.; Bisser, Sylvie; Barrett, Michael P.

    2016-01-01

    Treatment for human African trypanosomiasis is dependent on the species of trypanosome causing the disease and the stage of the disease (stage 1 defined by parasites being present in blood and lymphatics whilst for stage 2, parasites are found beyond the blood-brain barrier in the cerebrospinal fluid (CSF)). Currently, staging relies upon detecting the very low number of parasites or elevated white blood cell numbers in CSF. Improved staging is desirable, as is the elimination of the need for lumbar puncture. Here we use metabolomics to probe samples of CSF, plasma and urine from 40 Angolan patients infected with Trypanosoma brucei gambiense, at different disease stages. Urine samples provided no robust markers indicative of infection or stage of infection due to inherent variability in urine concentrations. Biomarkers in CSF were able to distinguish patients at stage 1 or advanced stage 2 with absolute specificity. Eleven metabolites clearly distinguished the stage in most patients and two of these (neopterin and 5-hydroxytryptophan) showed 100% specificity and sensitivity between our stage 1 and advanced stage 2 samples. Neopterin is an inflammatory biomarker previously shown in CSF of stage 2 but not stage 1 patients. 5-hydroxytryptophan is an important metabolite in the serotonin synthetic pathway, the key pathway in determining somnolence, thus offering a possible link to the eponymous symptoms of “sleeping sickness”. Plasma also yielded several biomarkers clearly indicative of the presence (87% sensitivity and 95% specificity) and stage of disease (92% sensitivity and 81% specificity). A logistic regression model including these metabolites showed clear separation of patients being either at stage 1 or advanced stage 2 or indeed diseased (both stages) versus control. PMID:27941966

  17. Tsetse Control and Gambian Sleeping Sickness; Implications for Control Strategy

    PubMed Central

    Kovacic, Vanja; Mangwiro, T. N. Clement; Vale, Glyn A.; Hastings, Ian; Solano, Philippe; Lehane, Michael J.; Torr, Steve J.

    2015-01-01

    Background Gambian sleeping sickness (human African trypanosomiasis, HAT) outbreaks are brought under control by case detection and treatment although it is recognised that this typically only reaches about 75% of the population. Vector control is capable of completely interrupting HAT transmission but is not used because it is considered too expensive and difficult to organise in resource-poor settings. We conducted a full scale field trial of a refined vector control technology to determine its utility in control of Gambian HAT. Methods and Findings The major vector of Gambian HAT is the tsetse fly Glossina fuscipes which lives in the humid zone immediately adjacent to water bodies. From a series of preliminary trials we determined the number of tiny targets required to reduce G. fuscipes populations by more than 90%. Using these data for model calibration we predicted we needed a target density of 20 per linear km of river in riverine savannah to achieve >90% tsetse control. We then carried out a full scale, 500 km2 field trial covering two HAT foci in Northern Uganda to determine the efficacy of tiny targets (overall target density 5.7/km2). In 12 months, tsetse populations declined by more than 90%. As a guide we used a published HAT transmission model and calculated that a 72% reduction in tsetse population is required to stop transmission in those settings. Interpretation The Ugandan census suggests population density in the HAT foci is approximately 500 per km2. The estimated cost for a single round of active case detection (excluding treatment), covering 80% of the population, is US$433,333 (WHO figures). One year of vector control organised within the country, which can completely stop HAT transmission, would cost US$42,700. The case for adding this method of vector control to case detection and treatment is strong. We outline how such a component could be organised. PMID:26267814

  18. Intensified Surveillance and Insecticide-based Control of the Chagas Disease Vector Triatoma infestans in the Argentinean Chaco

    PubMed Central

    Gurevitz, Juan M.; Gaspe, María Sol; Enriquez, Gustavo F.; Provecho, Yael M.; Kitron, Uriel; Gürtler, Ricardo E.

    2013-01-01

    Background The elimination of Triatoma infestans, the main Chagas disease vector in the Gran Chaco region, remains elusive. We implemented an intensified control strategy based on full-coverage pyrethroid spraying, followed by frequent vector surveillance and immediate selective insecticide treatment of detected foci in a well-defined rural area in northeastern Argentina with moderate pyrethroid resistance. We assessed long-term impacts, and identified factors and procedures affecting spray effectiveness. Methods and Findings After initial control interventions, timed-manual searches were performed by skilled personnel in 4,053 sites of 353–411 houses inspected every 4–7 months over a 35-month period. Residual insecticide spraying was less effective than expected throughout the three-year period, mainly because of the occurrence of moderate pyrethroid resistance and the limited effectiveness of selective treatment of infested sites only. After initial interventions, peridomestic infestation prevalence always exceeded domestic infestation, and timed-manual searches consistently outperformed householders' bug detection, except in domiciles. Most of the infestations occurred in houses infested at baseline, and were restricted to four main ecotopes. Houses with an early persistent infestation were spatially aggregated up to a distance of 2.5 km. An Akaike-based multi-model inference approach showed that new site-level infestations increased substantially with the local availability of appropriate refugia for triatomine bugs, and with proximity to the nearest site found infested at one or two preceding surveys. Conclusions and Significance Current vector control procedures have limited effectiveness in the Gran Chaco. Selective insecticide sprays must include all sites within the infested house compound. The suppression of T. infestans in rural areas with moderate pyrethroid resistance requires increased efforts and appropriate management actions. In addition to

  19. Preliminary Investigation on Battery Sizing Investigation for Thrust Vector Control on Ares I and Ares V Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Miller, Thomas B.

    2011-01-01

    An investigation into the merits of battery powered Electro Hydrostatic Actuation (EHA) for Thrust Vector Control (TVC) of the Ares I and Ares V launch vehicles is described. A top level trade study was conducted to ascertain the technical merits of lithium-ion (Li-ion) and thermal battery performance to determine the preferred choice of an energy storage system chemistry that provides high power discharge capability for a relatively short duration.

  20. Modeling Transmission Dynamics and Control of Vector-Borne Neglected Tropical Diseases

    PubMed Central

    Luz, Paula M.; Struchiner, Claudio J.; Galvani, Alison P.

    2010-01-01

    Neglected tropical diseases affect more than one billion people worldwide. The populations most impacted by such diseases are typically the most resource-limited. Mathematical modeling of disease transmission and cost-effectiveness analyses can play a central role in maximizing the utility of limited resources for neglected tropical diseases. We review the contributions that mathematical modeling has made to optimizing intervention strategies of vector-borne neglected diseases. We propose directions forward in the modeling of these diseases, including integrating new knowledge of vector and pathogen ecology, incorporating evolutionary responses to interventions, and expanding the scope of sensitivity analysis in order to achieve robust results. PMID:21049062

  1. Multiaxis control power from thrust vectoring for a supersonic fighter aircraft model at Mach 0.20 to 2.47

    NASA Technical Reports Server (NTRS)

    Capone, Francis J.; Bare, E. Ann

    1987-01-01

    The aeropropulsive characteristics of an advanced twin-engine fighter aircraft designed for supersonic cruise have been studied in the Langley 16-Foot Tansonic Tunnel and the Lewis 10- by 10-Foot Supersonic Tunnel. The objective was to determine multiaxis control-power characteristics from thrust vectoring. A two-dimensional convergent-divergent nozzle was designed to provide yaw vector angles of 0, -10, and -20 deg combined with geometric pitch vector angles of 0 and 15 deg. Yaw thrust vectoring was provided by yaw flaps located in the nozzle sidewalls. Roll control was obtained from differential pitch vectoring. This investigation was conducted at Mach numbers from 0.20 to 2.47. Angle of attack was varied from 0 to about 19 deg, and nozzle pressure ratio was varied from about 1 (jet off) to 28, depending on Mach number. Increments in force or moment coefficient that result from pitch or yaw thrust vectoring remain essentially constant over the entire angle-of-attack range of all Mach numbers tested. There was no effect of pitch vectoring on the lateral aerodynamic forces and moments and only very small effects of yaw vectoring on the longitudinal aerodynamic forces and moments. This result indicates little cross-coupling of control forces and moments for combined pitch-yaw vectoring.

  2. A general modelling and control algorithm of a three-phase multilevel diode clamped inverter by means of a direct space vector control

    NASA Astrophysics Data System (ADS)

    Bouhali, O.; Francois, B.; Berkouk, E. M.; Saudemont, C.

    2005-07-01

    This paper presents a simple and general direct modulation strategy that enables to copy directly modulated waveforms onto output voltages of a multilevel three-phase Diode Clamped Inverter (DCI). A general modelling of this converter is presented. A space vector scheme is developed without using Park transforms. Based on this algorithm, the location of the reference voltage vector is determined and the voltage vectors for the modulation are deduced. Simultaneously, their durations are calculated. The proposed algorithm is general and can be directly applied to a (n+1) levels inverter independently on its topology (Diode Clamped Inverter, Neutral Point Clamped, Flying Capacitor Inverter...). To verify this algorithm, both control algorithms of a 5-level DCI and a 11-level DCI are considered and simulation results are given.

  3. Tsetse Fly Control in Kenya's Spatially and Temporally Dynamic Control Reservoirs: A Cost Analysis

    PubMed Central

    McCord, Paul F.; Messina, Joseph P.; Campbell, David J.; Grady, Sue C.

    2011-01-01

    Human African trypanosomiasis (HAT) and animal African trypanosomiasis (AAT) are significant health concerns throughout much of sub-Saharan Africa. Funding for tsetse fly control operations has decreased since the 1970s, which has in turn limited the success of campaigns to control the disease vector. To maximize the effectiveness of the limited financial resources available for tsetse control, this study develops and analyzes spatially and temporally dynamic tsetse distribution maps of Glossina subgenus Morsitans populations in Kenya from January 2002 to December 2010, produced using the Tsetse Ecological Distribution Model. These species distribution maps reveal seasonal variations in fly distributions. Such variations allow for the identification of “control reservoirs” where fly distributions are spatially constrained by fluctuations in suitable habitat and tsetse population characteristics. Following identification of the control reservoirs, a tsetse management operation is simulated in the control reservoirs using capital and labor control inputs from previous studies. Finally, a cost analysis, following specific economic guidelines from existing tsetse control analyses, is conducted to calculate the total cost of a nationwide control campaign of the reservoirs compared to the cost of a nationwide campaign conducted at the maximum spatial extent of the fly distributions from January 2002 to December 2010. The total cost of tsetse management within the reservoirs sums to $14,212,647, while the nationwide campaign at the maximum spatial extent amounts to $33,721,516. This savings of $19,508,869 represents the importance of identifying seasonally dynamic control reservoirs when conducting a tsetse management campaign, and, in the process, offers an economical means of fly control and disease management for future program planning. PMID:22581989

  4. IMPROVEMENT OF SMVGEAR II ON VECTOR AND SCALAR MACHINES THROUGH ABSOLUTE ERROR TOLERANCE CONTROL (R823186)

    EPA Science Inventory

    The computer speed of SMVGEAR II was improved markedly on scalar and vector machines with relatively little loss in accuracy. The improvement was due to a method of frequently recalculating the absolute error tolerance instead of keeping it constant for a given set of chemistry. ...

  5. Efficacy of extracts of Bacillus thuringiensis israelensis for the control of mosquito vectors.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    More than 1 million human cases of Chikungunya were recently reported in India. Aedes aegypti (the yellow fever mosquito) is an important disease vector in India where it transmits Chikungunya, dengue, and yellow fever viruses to humans. In this study, scientists from Bharathiar University in Coim...

  6. Certifying achievement in the control of Chagas disease native vectors: what is a viable scenario?

    PubMed Central

    Hashimoto, Ken; Yoshioka, Kota

    2014-01-01

    As an evaluation scheme, we propose certifying for “control”, as alternative to “interruption”, of Chagas disease transmission by native vectors, to project a more achievable and measurable goal and sharing good practices through an “open online platform” rather than “formal certification” to make the key knowledge more accumulable and accessible. PMID:25317713

  7. Expressed sequence tags from the black-winged sharpshooter: Application to biology and vector control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We identified 14 putative full-length transcripts of proteins important for the survival of the black-winged sharpshooter, BWSS, Oncometopia nigricans. The BWSS is considered a highly competent vector of several strains of the xylem-inhabiting bacterium Xylella fastidiosa, the causal agent of a numb...

  8. Using global information technology to detect, monitor, and control mosquito pest and disease vector populations.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Geographic Information Systems (GIS), image analysis, and remote sensing comprise global information technologies that are used to characterize pest and vector populations of mosquitoes. At this national meeting, scientists from ARS and McNeese State University organized and convened a half-day sym...

  9. Recombinant viral vectored vaccines for the control of avian influenza: a review

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The poultry industry has been at the forefront of developing recombinant viral vectored vaccines in an attempt to improve the immune response to vaccination. With AIV, the hemagglutinin surface glycoprotein is the key antigen for protection against infection. This allows a single gene to be transf...

  10. Characteristics, behaviors and association between Human African Trypanosomiasis and HIV seropositivity among volunteer blood donors in a semi-rural area: A survey from Kikwit, the Democratic Republic of Congo.

    PubMed

    Ndilu, Lefils Kasiama; Ekila, Mathilde Bothale; Mayuma, Donald Fundji; Musaka, Alain; Wumba, Roger; Aloni, Michel Ntetani

    2016-12-01

    Blood safety is a major element in the strategy to control the HIV epidemic. The aim of this study was to determine the prevalence and the associated factors of a positive HIV test among blood donors and its association between Human African Trypanosomiasis in Kikwit, the Democratic Republic of Congo. A cross-sectional study was conducted between November 2012 and May 2013. An anonymous questionnaire was designed to extract relevant data. The average mean age of participants was 30 years. The majority were man (67.8%). The overall prevalence of HIV, syphilis, hepatitis B, hepatitis C and human African trypanosomiasis was respectively 3.2%, 1.9%, 1.6%, 1.3% and 1.3%. Alcohol intake, casual unprotected sex, not using condoms during casual sex, sex after alcohol intake and seroprevalence of human African trypanosomiasis were significantly associated with a positive HIV test result ( p<0.05). In this study, sexual risk behaviors were the major risk factors associated with positive HIV tests in blood donors living in Kikwit. It is important to raise awareness about HIV and voluntary blood donation in response to some observations noted in this study such as the low educational level of the blood donors, the low level of knowledge of HIV prevention methods.

  11. Glymphatic fluid transport controls paravascular clearance of AAV vectors from the brain

    PubMed Central

    Murlidharan, Giridhar; Crowther, Andrew; Reardon, Rebecca A.; Song, Juan

    2016-01-01

    Adeno-associated viruses (AAV) are currently being evaluated in clinical trials for gene therapy of CNS disorders. However, host factors that influence the spread, clearance, and transduction efficiency of AAV vectors in the brain are not well understood. Recent studies have demonstrated that fluid flow mediated by aquaporin-4 (AQP4) channels located on astroglial end feet is essential for exchange of solutes between interstitial and cerebrospinal fluid. This phenomenon, which is essential for interstitial clearance of solutes from the CNS, has been termed glial-associated lymphatic transport or glymphatic transport. In the current study, we demonstrate that glymphatic transport profoundly affects various aspects of AAV gene transfer in the CNS. Altered localization of AQP4 in aged mouse brains correlated with significantly increased retention of AAV vectors in the parenchyma and reduced systemic leakage following ventricular administration. We observed a similar increase in AAV retention and transgene expression upon i.c.v. administration in AQP4–/– mice. Consistent with this observation, fluorophore-labeled AAV vectors showed markedly reduced flux from the ventricles of AQP4–/– mice compared with WT mice. These results were further corroborated by reduced AAV clearance from the AQP4-null brain, as demonstrated by reduced transgene expression and vector genome accumulation in systemic organs. We postulate that deregulation of glymphatic transport in aged and diseased brains could markedly affect the parenchymal spread, clearance, and gene transfer efficiency of AAV vectors. Assessment of biomarkers that report the kinetics of CSF flux in prospective gene therapy patients might inform variable treatment outcomes and guide future clinical trial design. PMID:27699236

  12. Glymphatic fluid transport controls paravascular clearance of AAV vectors from the brain.

    PubMed

    Murlidharan, Giridhar; Crowther, Andrew; Reardon, Rebecca A; Song, Juan; Asokan, Aravind

    2016-09-08

    Adeno-associated viruses (AAV) are currently being evaluated in clinical trials for gene therapy of CNS disorders. However, host factors that influence the spread, clearance, and transduction efficiency of AAV vectors in the brain are not well understood. Recent studies have demonstrated that fluid flow mediated by aquaporin-4 (AQP4) channels located on astroglial end feet is essential for exchange of solutes between interstitial and cerebrospinal fluid. This phenomenon, which is essential for interstitial clearance of solutes from the CNS, has been termed glial-associated lymphatic transport or glymphatic transport. In the current study, we demonstrate that glymphatic transport profoundly affects various aspects of AAV gene transfer in the CNS. Altered localization of AQP4 in aged mouse brains correlated with significantly increased retention of AAV vectors in the parenchyma and reduced systemic leakage following ventricular administration. We observed a similar increase in AAV retention and transgene expression upon i.c.v. administration in AQP4(-/-) mice. Consistent with this observation, fluorophore-labeled AAV vectors showed markedly reduced flux from the ventricles of AQP4(-/-) mice compared with WT mice. These results were further corroborated by reduced AAV clearance from the AQP4-null brain, as demonstrated by reduced transgene expression and vector genome accumulation in systemic organs. We postulate that deregulation of glymphatic transport in aged and diseased brains could markedly affect the parenchymal spread, clearance, and gene transfer efficiency of AAV vectors. Assessment of biomarkers that report the kinetics of CSF flux in prospective gene therapy patients might inform variable treatment outcomes and guide future clinical trial design.

  13. Gambiense human african trypanosomiasis and immunological memory: effect on phenotypic lymphocyte profiles and humoral immunity.

    PubMed

    Lejon, Veerle; Mumba Ngoyi, Dieudonné; Kestens, Luc; Boel, Luc; Barbé, Barbara; Kande Betu, Victor; van Griensven, Johan; Bottieau, Emmanuel; Muyembe Tamfum, Jean-Jacques; Jacobs, Jan; Büscher, Philippe

    2014-03-01

    In mice, experimental infection with Trypanosoma brucei causes decreased bone marrow B-cell development, abolished splenic B-cell maturation and loss of antibody mediated protection including vaccine induced memory responses. Nothing is known about this phenomenon in human African trypanosomiasis (HAT), but if occurring, it would imply the need of revaccination of HAT patients after therapy and abolish hope for a HAT vaccine. The effect of gambiense HAT on peripheral blood memory T- and B-cells and on innate and vaccine induced antibody levels was examined. The percentage of memory B- and T-cells was quantified in peripheral blood, prospectively collected in DR Congo from 117 Trypanosoma brucei gambiense infected HAT patients before and six months after treatment and 117 controls at the same time points. Antibodies against carbohydrate antigens on red blood cells and against measles were quantified. Before treatment, significantly higher percentages of memory B-cells, mainly T-independent memory B-cells, were observed in HAT patients compared to controls (CD20+CD27+IgM+, 13.0% versus 2.0%, p<0.001). The percentage of memory T-cells, mainly early effector/memory T-cells, was higher in HAT (CD3+CD45RO+CD27+, 19.4% versus 16.7%, p = 0.003). After treatment, the percentage of memory T-cells normalized, the percentage of memory B-cells did not. The median anti-red blood cell carbohydrate IgM level was one titer lower in HAT patients than in controls (p<0.004), and partially normalized after treatment. Anti-measles antibody concentrations were lower in HAT patients than in controls (medians of 1500 versus 2250 mIU/ml, p = 0.02), and remained so after treatment, but were above the cut-off level assumed to provide protection in 94.8% of HAT patients, before and after treatment (versus 98.3% of controls, p = 0.3). Although functionality of the B-cells was not verified, the results suggest that immunity was conserved in T.b. gambiense infected HAT patients and

  14. A review of the vector management methods to prevent and control outbreaks of West Nile virus infection and the challenge for Europe

    PubMed Central

    2014-01-01

    West Nile virus infection is a growing concern in Europe. Vector management is often the primary option to prevent and control outbreaks of the disease. Its implementation is, however, complex and needs to be supported by integrated multidisciplinary surveillance systems and to be organized within the framework of predefined response plans. The impact of the vector control measures depends on multiple factors and the identification of the best combination of vector control methods is therefore not always straightforward. Therefore, this contribution aims at critically reviewing the existing vector control methods to prevent and control outbreaks of West Nile virus infection and to present the challenges for Europe. Most West Nile virus vector control experiences have been recently developed in the US, where ecological conditions are different from the EU and vector control is organized under a different regulatory frame. The extrapolation of information produced in North America to Europe might be limited because of the seemingly different epidemiology in the European region. Therefore, there is an urgent need to analyse the European experiences of the prevention and control of outbreaks of West Nile virus infection and to perform robust cost-benefit analysis that can guide the implementation of the appropriate control measures. Furthermore, to be effective, vector control programs require a strong organisational backbone relying on a previously defined plan, skilled technicians and operators, appropriate equipment, and sufficient financial resources. A decision making guide scheme is proposed which may assist in the process of implementation of vector control measures tailored on specific areas and considering the available information and possible scenarios. PMID:25015004

  15. Boundaries of the origin of replication: creation of a pET-28a-derived vector with p15A copy control allowing compatible coexistence with pET vectors.

    PubMed

    Sathiamoorthy, Sarmitha; Shin, Jumi A

    2012-01-01

    During our studies involving protein-DNA interactions, we constructed plasmid pSAM to fulfill two requirements: 1) to facilitate transfer of cloned sequences from widely used expression vector pET-28a(+), and 2) to provide a vector compatible with pBR322-derived plasmids for use in cells harboring two different plasmids. Vector pSAM is a pET-28a(+)-derived plasmid with the p15A origin of replication (ori); pET-28a(+) contains the pBR322 replicon that is incompatible with other pBR322-derived plasmids. By replacing the original pET-28a(+) replicon-comprising the ori, RNAI, RNAII, and Rom-with the p15A replicon, we generated pSAM, which contains the pET-28a(+) multiple cloning site and is now compatible with pBR322-derived vectors. Plasmid copy number was assessed using quantitative PCR: pSAM copy number was maintained at 18±4 copies per cell, consistent with that of other p15A-type vectors. Compatibility with pBR322-derived vectors was tested with pGEX-6p-1 and pSAM, which maintained their copy numbers of 49±10 and 14±4, respectively, when both were present within the same cell. Swapping of the ori is a common practice; however, it is vital that all regions of the original replicon be removed. Additional vector pSAMRNAI illustrated that incompatibility remains when portions of the replicon, such as RNAI and/or Rom, are retained; pSAMRNAI, which contains the intact RNAI but not ROM, lowered the copy number of pGEX-6p-1 to 18±2 in doubly transformed cells due to retention of the pET-28a(+)-derived RNAI. Thus, pSAMRNAI is incompatible with vectors controlled by the pBR322 replicon and further demonstrates the need to remove all portions of the original replicon and to quantitatively assess copy number, both individually and in combination, to ensure vector compatibility. To our knowledge, this is the first instance where the nascent vector has been quantitatively assessed for both plasmid copy number and compatibility. New vector pSAM provides ease of transferring

  16. Progress in directed energy control of vectors for microbes and other cells

    NASA Astrophysics Data System (ADS)

    Kiel, Johnathan L.; Parker, Jill E.; Holwitt, Eric A.; Vivekananda, Jeeva; Sloan, Mark A.; Stribling, Lucille J. V.

    2004-07-01

    Biosynthetic semiconductor, diazoluminomelanin (DALM), is a polymer of tyrosine, luminol, and nitrite. DALM has a very large cross section of absorption for light from ultraviolet to radio frequencies. This polymer can be made efficiently in a genetically engineered E.coli, JM109/pIC2ORNR1.1 (ATCC# 69905). We have been pursuing ways to couple electromagnetic radiation to vectors using this polymer. DNA capture elements (DCEs; formerly aptamers) have made this possible. We incorporated DCEs into the plasmid of this E. coli to direct binding to whatever microbe or cell desired and to produce DALM attached to the plasmid DNA. Using two other vectors pSV2neoNR101 or pSV2neoNR8005 (ATCC # 69617 and 69618, respectively), both propagated in the E. coli host HB101, we have also inserted genes necessary for DALM production into animal and human cell lines (mouse monocytic leukemia: ATCC # CRL- 11771, -11772, -1173, mouse mammary adenocarcinoma: ATCC# CRL-12184, -12185; and human carcinoma of the cervix: ATCC # CRL-12510). The DCE/DALM vectors can be used to tag target cells, detectable by broad-spectrum light absorbance, luminescence, or fluorescence. DCE/DALM can further be activated with light, microwave energy, or by oxidative chemistry to kill the targeted microbes or other cells.

  17. Substituted 2-Phenyl-Imidazopyridines: A New Class of Drug Leads for Human African Trypanosomiasis

    PubMed Central

    Tatipaka, Hari Babu; Gillespie, J. Robert; Chatterjee, Arnab K.; Norcross, Neil R.; Hulverson, Matthew A.; Ranade, Ranae M.; Nagendar, Pendem; Creason, Sharon A.; McQueen, Joshua; Duster, Nicole A.; Nagle, Advait; Supek, Frantisek; Molteni, Valentina; Wenzler, Tanja; Brun, Reto; Glynne, Richard; Buckner, Frederick S.; Gelb, Michael H.

    2014-01-01

    A phenotypic screen of a compound library for antiparasitic activity on Trypanosoma brucei, the causative agent of human African trypanosomiasis, led to the identification of substituted 2-(3-aminophenyl) oxazolopyridines as a starting point for hit-to-lead medicinal chemistry. A total of 110 analogues were prepared, which led to the identification of 64, a substituted 2-(3-aminophenyl) imidazopyridine. This compound showed antiparasitic activity in vitro with an EC50 of 2 nM and displayed reasonable drug-like properties when tested in a number of in vitro assays. The compound was orally bioavailable and displayed good plasma and brain exposure in mice. Compound 64 cured mice infected with Trypanosoma brucei when dosed orally down to 2.5 mg/kg. Given its potent anti-parasitic properties and its ease of synthesis, compound 64 represents a new lead for the development of drugs to treat human African trypanosomiasis. PMID:24354316

  18. A rare case of trypanosomiasis in a two month old infant in Mumbai, India.

    PubMed

    Kaur, Raminder; Gupta, V K; Dhariwal, A C; Jain, D C; Shiv, Lal

    2007-06-01

    Human Trypanosomiasis is a rare occurrence in India. In the cases reported so far the disease causative species have been the species infective to animals viz., Trypanosoma lewisi and Trypanosoma evansi. These animal species usually non pathogenic in humans can acquire the desired virulence and emerge as human pathogens causing serious disease, in the right combination of environmental, host related and organism related factors. We report here a case of trypanosomiasis caused by the rodent parasite T. lewisi in a two months old infant in urban Mumbai. Under the fastly changing environmental scenario there is an urgent need to be prepared for the emerging zoonoses. Any unusual disease occurrence in a given geographical area acquires a special significance in this context and should be reported to assess its public health importance and be prepared to deal with the consequent challenges posed, if any.

  19. Indigenous knowledge system for treatment of trypanosomiasis in Kaduna state of Nigeria.

    PubMed

    Atawodi, S E; Ameh, D A; Ibrahim, S; Andrew, J N; Nzelibe, H C; Onyike, E O; Anigo, K M; Abu, E A; James, D B; Njoku, G C; Sallau, A B

    2002-02-01

    A survey was carried out in Kaduna State of Nigeria to establish the indigenous knowledge system for treating trypanosomiasis in domestic animals. Questionnaire and interviews were, respectively, administered to, or conducted with about 200 livestock farmers and traders spread around the state. Data obtained revealed the use of several plants either alone or in combination, for the treatment and management of trypasonomiasis. The most common plants encountered were Adansonia digitata, Terminalia avicennoides, Khaya senegalensis, Cissus populnea, Tamarindus indica, Lawsonia inermis, Boswellia dalzielli, Pseudocedrela kotschi, Syzyium quinensis, Sterculia setigera, Afzelia africana, Prosopis africana, Lancea kerstingii. The method of preparation and mode of administration of some of these plants in the treatment of trypanosomiasis are reviewed and discussed.

  20. Substituted 2-phenylimidazopyridines: a new class of drug leads for human African trypanosomiasis.

    PubMed

    Tatipaka, Hari Babu; Gillespie, J Robert; Chatterjee, Arnab K; Norcross, Neil R; Hulverson, Matthew A; Ranade, Ranae M; Nagendar, Pendem; Creason, Sharon A; McQueen, Joshua; Duster, Nicole A; Nagle, Advait; Supek, Frantisek; Molteni, Valentina; Wenzler, Tanja; Brun, Reto; Glynne, Richard; Buckner, Frederick S; Gelb, Michael H

    2014-02-13

    A phenotypic screen of a compound library for antiparasitic activity on Trypanosoma brucei, the causative agent of human African trypanosomiasis, led to the identification of substituted 2-(3-aminophenyl)oxazolopyridines as a starting point for hit-to-lead medicinal chemistry. A total of 110 analogues were prepared, which led to the identification of 64, a substituted 2-(3-aminophenyl)imidazopyridine. This compound showed antiparasitic activity in vitro with an EC50 of 2 nM and displayed reasonable druglike properties when tested in a number of in vitro assays. The compound was orally bioavailable and displayed good plasma and brain exposure in mice. Compound 64 cured mice infected with Trypanosoma brucei when dosed orally down to 2.5 mg/kg. Given its potent antiparasitic properties and its ease of synthesis, compound 64 represents a new lead for the development of drugs to treat human African trypanosomiasis.

  1. Combatting African Animal Trypanosomiasis (AAT) in livestock: The potential role of trypanotolerance.

    PubMed

    Yaro, M; Munyard, K A; Stear, M J; Groth, D M

    2016-07-30

    African Animal Trypanosomiasis (AAT) is endemic in at least 37 of the 54 countries in Africa. It is estimated to cause direct and indirect losses to the livestock production industry in excess of US$ 4.5 billion per annum. A century of intervention has yielded limited success, owing largely to the extraordinary complexity of the host-parasite interaction. Trypanotolerance, which refers to the inherent ability of some African livestock breeds, notably Djallonke sheep, N'Dama cattle and West African Dwarf goats, to withstand a trypanosomiasis challenge and still remain productive without any form of therapy, is an economically sustainable option for combatting this disease. Yet trypanotolerance has not been adequately exploited in the fight against AAT. In this review, we describe new insights into the genetic basis of trypanotolerance and discuss the potential of exploring this phenomenon as an integral part of the solution for AAT, particularly, in the context of African animal production systems.

  2. Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania

    PubMed Central

    Ferguson, Heather M; Ng'habi, Kija R; Walder, Thomas; Kadungula, Demetrius; Moore, Sarah J; Lyimo, Issa; Russell, Tanya L; Urassa, Honorathy; Mshinda, Hassan; Killeen, Gerry F; Knols, Bart GJ

    2008-01-01

    Background Medical entomologists increasingly recognize that the ability to make inferences between laboratory experiments of vector biology and epidemiological trends observed in the field is hindered by a conceptual and methodological gap occurring between these approaches which prevents hypothesis-driven empirical research from being conducted on relatively large and environmentally realistic scales. The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap. Semi-field systems are defined as enclosed environments, ideally situated within the natural ecosystem of a target disease vector and exposed to ambient environmental conditions, in which all features necessary for its life cycle completion are present. Although the value of SFS as a research tool for malaria vector biology is gaining recognition, only a few such facilities exist worldwide and are relatively small in size (< 100 m2). Methods The establishment of a 625 m2 state-of-the-art SFS for large-scale experimentation on anopheline mosquito ecology and control within a rural area of southern Tanzania, where malaria transmission intensities are amongst the highest ever recorded, is described. Results A greenhouse frame with walls of mosquito netting and a polyethylene roof was mounted on a raised concrete platform at the Ifakara Health Institute. The interior of the SFS was divided into four separate work areas that have been set up for a variety of research activities including mass-rearing for African malaria vectors under natural conditions, high throughput evaluation of novel mosquito control and trapping techniques, short-term assays of host-seeking behaviour and olfaction, and longer-term experimental investigation of anopheline population dynamics and gene flow within a contained environment that simulates a local village domestic setting. Conclusion The SFS at Ifakara was completed and ready for use in under two years. Preliminary observations

  3. The Atlas of human African trypanosomiasis: a contribution to global mapping of neglected tropical diseases

    PubMed Central

    2010-01-01

    Background Following World Health Assembly resolutions 50.36 in 1997 and 56.7 in 2003, the World Health Organization (WHO) committed itself to supporting human African trypanosomiasis (HAT)-endemic countries in their efforts to remove the disease as a public health problem. Mapping the distribution of HAT in time and space has a pivotal role to play if this objective is to be met. For this reason WHO launched the HAT Atlas initiative, jointly implemented with the Food and Agriculture Organization of the United Nations, in the framework of the Programme Against African Trypanosomosis. Results The distribution of HAT is presented for 23 out of 25 sub-Saharan countries having reported on the status of sleeping sickness in the period 2000 - 2009. For the two remaining countries, i.e. Angola and the Democratic Republic of the Congo, data processing is ongoing. Reports by National Sleeping Sickness Control Programmes (NSSCPs), Non-Governmental Organizations (NGOs) and Research Institutes were collated and the relevant epidemiological data were entered in a database, thus incorporating (i) the results of active screening of over 2.2 million people, and (ii) cases detected in health care facilities engaged in passive surveillance. A total of over 42 000 cases of HAT and 6 000 different localities were included in the database. Various sources of geographic coordinates were used to locate the villages of epidemiological interest. The resulting average mapping accuracy is estimated at 900 m. Conclusions Full involvement of NSSCPs, NGOs and Research Institutes in building the Atlas of HAT contributes to the efficiency of the mapping process and it assures both the quality of the collated information and the accuracy of the outputs. Although efforts are still needed to reduce the number of undetected and unreported cases, the comprehensive, village-level mapping of HAT control activities over a ten-year period ensures a detailed and reliable representation of the known

  4. Human African trypanosomiasis in a Belgian traveller returning from the Masai Mara area, Kenya, February 2012.

    PubMed

    Clerinx, J; Vlieghe, E; Asselman, V; Van de Casteele, S; Maes, M B; Lejon, V

    2012-03-08

    A Belgian traveller was diagnosed with human African trypanosomiasis (HAT) due to Trypanosoma brucei rhodesiense nine days after visiting the Masai Mara area in Kenya. He presented with an inoculation chancre and was treated with suramin within four days of fever onset. Two weeks earlier, HAT was also reported in a German traveller who had visited the Masai Mara area. Because no cases have occurred in the area for over 12 years, this may indicate a focal cluster of HAT.

  5. Target-based drug discovery for human African trypanosomiasis: selection of molecular target and chemical matter.

    PubMed

    Gilbert, Ian H

    2014-01-01

    Target-based approaches for human African trypanosomiasis (HAT) and related parasites can be a valuable route for drug discovery for these diseases. However, care needs to be taken in selection of both the actual drug target and the chemical matter that is developed. In this article, potential criteria to aid target selection are described. Then the physiochemical properties of typical oral drugs are discussed and compared to those of known anti-parasitics.

  6. Identification and Characterization of FTY720 for the Treatment of Human African Trypanosomiasis

    PubMed Central

    Kaiser, Marcel; Avery, Vicky M.

    2015-01-01

    The screening of a focused library identified FTY720 (Fingolimod; Gilenya) as a potent selective antitrypanosomal compound active against Trypanosoma brucei gambiense and T. brucei rhodesiense, the causative agents of human African trypanosomiasis (HAT). This is the first report of trypanocidal activity for FTY720, an oral drug registered for the treatment of relapsing multiple sclerosis, and the characterization of sphingolipids as a potential new class of compounds for HAT. PMID:26666915

  7. Spatial orientation and balance control changes induced by altered gravitoinertial force vectors

    NASA Technical Reports Server (NTRS)

    Kaufman, G. D.; Wood, S. J.; Gianna, C. C.; Black, F. O.; Paloski, W. H.

    2001-01-01

    were short-lived, however, with a recovery time of several postural test trials (minutes). There were also asymmetries in the direction of postcentrifugation COP and head tilt which depended on the subject's orientation during the centrifugation adaptation period (left ear or right ear out). The amount of total head movements during centrifugation correlated poorly or inversely with postcentrifugation postural stability, and the most unstable subject made no head movements. There was no decrease in postural stability after static tilt, although these subjects also reported a perceived tilt briefly after return to upright, and they also had COP asymmetries. Abnormal subjects underestimated roll-tilt during centrifugation, and their directed saccades revealed permanent spatial distortions. Bilateral abnormal subjects started out with poor postural control, but showed no postural decrements after centrifugation, while unilateral abnormal subjects had varying degrees of postural decrement, both in their everyday function and as a result of experiencing the centrifugation. In addition, three unilateral, abnormal subjects, who rode twice in opposite orientations, revealed a consistent orthogonal pattern of COP offsets after centrifugation. These results suggest that both orientation and magnitude of the gravitoinertial vector are used by the central nervous system for calibration of multiple orientation systems. A change in the background gravitoinertial force (otolith input) can rapidly initiate postural and perceptual adaptation in several sensorimotor systems, independent of a structured visual surround.

  8. Mosquito fauna and perspectives for integrated control of urban vector-mosquito populations in Southern Benin (West Africa).

    PubMed

    Lingenfelser, Andre; Rydzanicz, Katarzyna; Kaiser, Achim; Becker, Norbert

    2010-01-01

    This study aims at an integrated vector management (IVM) concept of implementing biological control agents against vector mosquito larvae as a cost-effective and scalable control strategy. In the first step, the mosquito species composition fauna of southern Benin was studied using standard entomological procedures in natural and man-made habitats. Altogether, 24 species belonging to 6 genera of mosquitoes Aedes, Anopheles, Culex, Mansonia, Uranotaenia, Ficalbia were recorded. Five species, Cx. thalassius, Cx. nebulosus, Cx. perfuscus, Cx. pocilipes and Fi. mediolineata are described the first time for Benin. The local mosquito species showed high susceptibility to a Bacillus sphaericus formulation (VectoLex(R) WDG ) in a standardized field test. A dosage of 1 g/m(2) was effective to achieve 100 percent mortality rate for Cx. quinquefasciatus late instar larvae in a sewage habitat, with a residual effect of up to 7 days. After more than 1 year of baseline data collection, operational larviciding with B. thuringiensis var. israelensis and B. sphaericus was commenced in 2006 in selected areas. Microbial insecticides products for larval control show great potential within IVM programmes and may augment control efforts against adult insects, such as the use of insecticide-treated bed nets or indoor wall spraying in many parts of Africa.

  9. Modelling geographic variation in the cost-effectiveness of control policies for infectious vector diseases: the example of Chagas disease.

    PubMed

    Castillo-Riquelme, Marianela; Chalabi, Zaid; Lord, Joanne; Guhl, Felipe; Campbell-Lendrum, Diarmid; Davies, Clive; Fox-Rushby, Julia

    2008-03-01

    Few cost-effectiveness analysis (CEA) models have accounted for geographic variation in input parameters. This paper describes a deterministic discrete-time multi-state model to estimate the cost-effectiveness of vector control policies for Chagas disease, where implementation varies according to village characteristics. The model outputs include the total number of new infections, disability adjusted life years (DALYs) incurred, costs of associated healthcare, and total costs of the Ministry of Health's control policy for house surveillance and spraying. Incremental net benefits were estimated to determine Colombian villages in which it is cost-effective to implement the control policy. The robustness of these conclusions was evaluated by deterministic sensitivity analyses. The model should help provide a decision-support system to compare control policies and to allocate resources geographically.

  10. Torque Ripple Suppression Control Based on the Periodic Disturbance Observer with a Complex Vector Representation for Permanent Magnet Synchronous Motors

    NASA Astrophysics Data System (ADS)

    Tadano, Yugo; Akiyama, Takao; Nomura, Masakatsu; Ishida, Muneaki

    This paper introduces a method for torque ripple suppression control involving the use of the periodic disturbance observer. By using the Fourier transform (or rotating coordinate transform and a low-pass filter), the torque ripple component, which is synchronized with the motor rotation, can easily be obtained owing to its periodic variations. With the new control method, a suppression control system synchronized with the torque ripple frequency can be built. Further, by using the system identification technique, the model system from compensating current value to torque detection value can be expressed as a speed-adjustable one-dimension complex vector in rotating coordinates. This method is suitable for an adjustable-speed drive, and the control parameters and reference model can be adjusted automatically. The most important feature of this method is its excellent performance for mechanical resonance suppression caused by torque ripple. This paper presents analysis and experimental results that validate the method.

  11. Construction and characterization of plasmid and lambda phage vector systems for study of transcriptional control in Escherichia coli.

    PubMed

    Hirano, M; Shigesada, K; Imai, M

    1987-01-01

    We constructed a family of lambda phage and plasmid vectors which facilitate cloning and quantitative analysis of transcriptional regulator in both single and multiple copies. Their expression system was modified from the ara-trp-lac fusion operon of plasmid pMC81 [Casadaban and Cohen, J. Mol. Biol. 138 (1980) 179-207], which is designed to assay both promoters and terminators with a single vehicle. To eliminate transcriptional and translational polar effects liable to occur in the original fusion operon upon insertion of a foreign nucleotide sequence, intracistronic Rho-dependent terminators, that are present within the trpB gene and distal to the cloning site were deleted, and DNA spacers containing stop codons were introduced immediately before and after the cloning site. In analysis of the cloned trp regulatory region, the lambda phage system faithfully reproduced the tight regulation by tryptophan characteristic to the natural trp operon on the E. coli chromosome, whereas the plasmid counterpart exhibited a substantially relaxed response. Comparative studies on the relative strengths of various promoters and terminators have further demonstrated that the lambda phage vector system permits accurate assays of exceptionally strong promoters like Ptrp and lambda pL without disturbing the bacterial growth, while being sensitive enough for detecting low-level transcription under the control of weak promoters or potent terminators. Cloning with the lambda phage vector can be greatly facilitated by transferring the target regulatory site precloned with the plasmid onto the phage genome through in vivo recombination.

  12. The US Air Force Aerial Spray Unit: a history of large area disease vector control operations, WWII through Katrina.

    PubMed

    Breidenbaugh, Mark; Haagsma, Karl

    2008-01-01

    The US Air Force has had a long history of aerial applications of pesticides to fulfill a variety of missions, the most important being the protection of troops through the minimization of arthropod vectors capable of disease transmission. Beginning in World War II, aerial application of pesticides by the military has effectively controlled vector and nuisance pest populations in a variety of environments. Currently, the military aerial spray capability resides in the US Air Force Reserve (USAFR), which operates and maintains C-130 airplanes capable of a variety of missions, including ultra low volume applications for vector and nuisance pests, as well as higher volume aerial applications of herbicides and oil-spill dispersants. The USAFR aerial spray assets are the only such fixed-wing aerial spray assets within the Department of Defense. In addition to troop protection, the USAFR Aerial Spray Unit has participated in a number of humanitarian/relief missions, most recently in the response to the 2005 Hurricanes Katrina and Rita, which heavily damaged the Gulf Coasts of Louisiana, Mississippi, and Texas. This article provides historical background on the Air Force Aerial Spray Unit and describes the operations in Louisiana in the aftermath of Hurricane Katrina.

  13. A current analysis of chemotherapy strategies for the treatment of human African trypanosomiasis.

    PubMed

    Babokhov, Peter; Sanyaolu, Adekunle O; Oyibo, Wellington A; Fagbenro-Beyioku, Adetayo F; Iriemenam, Nnaemeka C

    2013-07-01

    Despite the recent advances in drug research, finding a safe, effective, and easy to use chemotherapy for human African trypanosomiasis (HAT) remains a challenging task. The four current anti-trypanosomiasis drugs have major disadvantages that limit more widespread use of these drugs in the endemic regions of sub-Saharan Africa. Pentamidine and suramin are limited by their effectiveness against the only first stage of Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, respectively. In addition, melarsoprol and eflornithine (two second stage drugs) each have disadvantages of their own. The former is toxic and has increasing treatment failures while the latter is expensive, laborious to administer, and lacks efficacy against T. b. rhodesiense. Furthermore, melarsoprol's toxicity and decreasing efficacy are glaring problems and phasing out the drug as a frontline treatment against T. b. gambiense is now possible with the emergence of competent, safe combination chemotherapies such as nifurtimox-eflornithine combination treatment (NECT). The future of eflornithine, on the other hand, is more promising. The drug is useful in the context of combination chemotherapy and potential orally administered analogues. Due to the limits of monotherapies, greater emphasis should be placed on the research and development of combination chemotherapies, based on the successful clinical tests with NECT and its current use as a frontline anti-trypanosomiasis treatment. This review discussed the current and future chemotherapy strategies for the treatment of HAT.

  14. Human African trypanosomiasis with 7-year incubation period: clinical, laboratory and neuroimaging findings.

    PubMed

    Wengert, Oliver; Kopp, Marcel; Siebert, Eberhard; Stenzel, Werner; Hegasy, Guido; Suttorp, Norbert; Stich, August; Zoller, Thomas

    2014-06-01

    Human African trypanosomiasis (HAT), also referred to as "sleeping sickness", is caused by the parasite Trypanosoma brucei. Diagnosing imported HAT outside endemic areas is difficult and diagnosis is often delayed. We report a case of imported human African trypanosomiasis caused by Trypanosoma brucei gambiense with an unusually long incubation period of at least 7 years. A 33 year old male African patient, a former resident of Cameroon, presented with a 4-month history of progressive personality changes. A few weeks before presentation the patient had first been admitted to a psychiatric ward and received antidepressant treatment, until a lumbar puncture showed pleocytosis and then antibiotic treatment for suspected neuroborreliosis was initiated. The patient continued to deteriorate during antibiotic treatment and became increasingly lethargic. Under antiparasitic and anti-inflammatory treatment, the condition of the patient gradually improved over the following months and he recovered completely after 24 months of follow-up. This well-documented case illustrates typical difficulties in establishing the correct diagnosis outside endemic areas and provides an overview of typical clinical, neuropathological and neuroimaging findings in T. b. gambiense trypanosomiasis, guiding the clinician in establishing the correct diagnosis in this rare disease.

  15. The central role of macrophages in trypanosomiasis-associated anemia: rationale for therapeutical approaches.

    PubMed

    Stijlemans, Benoît; Vankrunkelsven, Ann; Caljon, Guy; Bockstal, Viki; Guilliams, Martin; Bosschaerts, Tom; Beschin, Alain; Raes, Geert; Magez, Stefan; De Baetselier, Patrick

    2010-03-01

    Bovine African trypanosomiasis causes severe economical problems on the African continent and one of the most prominent immunopathological parameters associated with this parasitic infection is anemia. In this report we review the current knowledge of the mechanisms underlying trypanosomiasis-associated anemia. In first instance, the central role of macrophages and particularly their activation state in determining the outcome of the disease (i.e. trypanosusceptibility versus trypanotolerance) will be discussed. In essence, while persistence of classically activated macrophages (M1) contributes to anemia development, switching towards alternatively activated macrophages (M2) alleviates pathology including anemia. Secondly, while parasite-derived glycolipids such as the glycosylphosphatidylinositol (GPI) induce M1, host-derived IL-10 blocks M1-mediated inflammation, promotes M2 development and prevents anemia development. In this context, strategies aimed at inducing the M1 to M2 switch, such as GPI-based treatment, adenoviral delivery of IL-10 and induction of IL-10 producing regulatory T cells will be discussed. Finally, the crucial role of iron-homeostasis in trypanosomiasis-associated anemia development will be documented to stress the analogy with anemia of chronic disease (ACD), hereby providing new insight that might contribute to the treatment of ACD.

  16. Lack of galectin-3 alleviates trypanosomiasis-associated anemia of inflammation.

    PubMed

    Vankrunkelsven, Ann; De Ceulaer, Kris; Hsu, Daniel; Liu, Fu-Tong; De Baetselier, Patrick; Stijlemans, Benoît

    2010-01-01

    A typical pathological feature associated with experimental African trypanosomiasis (Trypanosoma brucei infection in mice) is anemia of chronic disease (ACD), which is due to a sustained type 1 cytokine-mediated inflammation and hyperactivation of M1 macrophages. Galectin-3 (Gal-3) was amply documented to contribute to the onset and persistence of type 1 inflammatory responses and we herein document that this protein is strongly upregulated during T. brucei infection. We evaluated the involvement of Gal-3 in trypanosomiasis-associated anemia using galectin-3 deficient (Gal3(-/-)) mice. T. brucei infected Gal3(-/-) mice manifested significant lower levels of anemia during infection and survived twice as long as wild type mice. Moreover, such mice showed increased levels of serum IL-10 and reduced liver pathology (as evidenced by lower AST/ALT levels). In addition, there was also an increase in gene expression of iron export genes and a reduced expression of genes, which are associated with accumulation of cellular iron. Our data indicate that Gal-3 is involved in the development of inflammation-associated anemia during African trypanosomiasis, possibly due to a disturbed iron metabolism that in turn may also lead to liver malfunction.

  17. Haptoglobin (HP) and Haptoglobin-related protein (HPR) copy number variation, natural selection, and trypanosomiasis.

    PubMed

    Hardwick, Robert J; Ménard, Anne; Sironi, Manuela; Milet, Jacqueline; Garcia, André; Sese, Claude; Yang, Fengtang; Fu, Beiyuan; Courtin, David; Hollox, Edward J

    2014-01-01

    Haptoglobin, coded by the HP gene, is a plasma protein that acts as a scavenger for free heme, and haptoglobin-related protein (coded by the HPR gene) forms part of the trypanolytic factor TLF-1, together with apolipoprotein L1 (ApoL1). We analyse the polymorphic small intragenic duplication of the HP gene, with alleles Hp1 and Hp2, in 52 populations, and find no evidence for natural selection either from extended haplotype analysis or from correlation with pathogen richness matrices. Using fiber-FISH, the paralog ratio test, and array-CGH data, we also confirm that the HPR gene is copy number variable, with duplication of the whole HPR gene at polymorphic frequencies in west and central Africa, up to an allele frequency of 15 %. The geographical distribution of the HPR duplication allele overlaps the region where the pathogen causing chronic human African trypanosomiasis, Trypanosoma brucei gambiense, is endemic. The HPR duplication has occurred on one SNP haplotype, but there is no strong evidence of extended homozygosity, a characteristic of recent natural selection. The HPR duplication shows a slight, non-significant undertransmission to human African trypanosomiasis-affected children of unaffected parents in the Democratic Republic of Congo. However, taken together with alleles of APOL1, there is an overall significant undertransmission of putative protective alleles to human African trypanosomiasis-affected children.

  18. Women's knowledge and perceptions of malaria and use of malaria vector control interventions in Kersa, eastern Ethiopia.

    PubMed

    Gobena, Tesfaye; Berhane, Yemane; Worku, Alemayehu

    2013-01-01

    Background Ethiopia has a long history of controlling malaria using vector control tools. Community knowledge and perceptions of malaria and use of malaria vector control interventions vary. Objective The aim of this study was to determine malaria-related knowledge and perceptions among women and to determine the use of malaria vector control interventions, mainly indoor residual spraying (IRS) and insecticide-treated nets (ITNs), among households in Kersa, Eastern Ethiopia. Design A cross-sectional survey was conducted in Kersa Demographic Surveillance and Health Research Center (KDS-HRC) site from October to November 2010. A total of 2,867 households were involved in the study. The data was collected via face-to-face interviews with the women of the household using a pre-tested questionnaire. The questionnaire contained closed, semiclosed, and open-ended questions to explore the reasons for non-use of the interventions. Each knowledge, perception, and practice question was analyzed separately. Results Of the total women, 2,463 (85.9%) had heard of malaria. Of them, 1,413 (57.4%) mentioned malaria as a communicable disease. But, only 793 (56.1%) of them associated mosquito bites with malaria transmission. Seven hundred and ninety-eight of the respondents (27.8%) had IRS coverage, and of these, 59 (7.4%) had re-plastered their interior walls following the application of insecticides. Of net-owning households, 33.5% had used at least one long-lasting insecticide-treated net (LLIN) the night before the survey. Societal reasons such as holy days and dislike of the insecticide mainly due to fear of its effects on their livestock, were the main reasons for re-spondents replastering their walls. Conclusions A substantial number of women had heard about malaria, but there was a knowledge gap regarding the route of malaria transmission. Less than one-third of the surveyed household houses were sprayed with insecticides, and a low proportion of net-owning households

  19. Simulation comparison of a decoupled longitudinal control system and a velocity vector control wheel steering system during landings in wind shear

    NASA Technical Reports Server (NTRS)

    Kimball, G., Jr.

    1980-01-01

    A simulator comparison of the velocity vector control wheel steering (VCWS) system and a decoupled longitudinal control system is presented. The piloting task was to use the electronic attitude direction indicator (EADI) to capture and maintain a 3 degree glide slope in the presence of wind shear and to complete the landing using the perspective runway included on the EADI. The decoupled control system used constant prefilter and feedback gains to provide steady state decoupling of flight path angle, pitch angle, and forward velocity. The decoupled control system improved the pilots' ability to control airspeed and flight path angle during the final stages of an approach made in severe wind shear. The system also improved their ability to complete safe landings. The pilots preferred the decoupled control system in severe winds and, on a pilot rating scale, rated the approach and landing task with the decoupled control system as much as 3 to 4 increments better than use of the VCWS system.

  20. Evaluation of Antigens for Development of a Serological Test for Human African Trypanosomiasis

    PubMed Central

    Biéler, Sylvain; Waltenberger, Harald; Barrett, Michael P.; McCulloch, Richard; Mottram, Jeremy C.; Carrington, Mark; Schwaeble, Wilhelm; McKerrow, James; Phillips, Margaret A.; Michels, Paul A.; Büscher, Philippe; Sanchez, Jean-Charles; Bishop, Richard; Robinson, Derrick R.; Bangs, James; Ferguson, Michael; Nerima, Barbara; Albertini, Audrey; Michel, Gerd; Radwandska, Magdalena; Ndung’u, Joseph Mathu

    2016-01-01

    Background Control and elimination of human African trypanosomiasis (HAT) can be accelerated through the use of diagnostic tests that are more accurate and easier to deploy. The goal of this work was to evaluate the immuno-reactivity of antigens and identify candidates to be considered for development of a simple serological test for the detection of Trypanosoma brucei gambiense or T. b. rhodesiense infections, ideally both. Methodology/Principal Findings The reactivity of 35 antigens was independently evaluated by slot blot and ELISA against sera from both T. b. gambiense and T. b. rhodesiense infected patients and controls. The antigens that were most reactive by both tests to T. b. gambiense sera were the membrane proteins VSG LiTat 1.3, VSG LiTat 1.5 and ISG64. Reactivity to T. b. rhodesiense sera was highest with VSG LiTat 1.3, VSG LiTat 1.5 and SRA, although much lower than with T. b. gambiense samples. The reactivity of all possible combinations of antigens was also calculated. When the slot blot results of 2 antigens were paired, a VSG LiTat 1.3- ISG75 combination performed best on T. b. gambiense sera, while a VSG LiTat 1.3-VSG LiTat 1.5 combination was the most reactive using ELISA. A combination of SRA and either VSG LiTat 1.3 or VSG LiTat 1.5 had the highest reactivity on T. b. rhodesiense sera according to slot blot, while in ELISA, pairing SRA with either GM6 or VSG LiTat 1.3 yielded the best results. Conclusions This study identified antigens that were highly reactive to T. b. gambiense sera, which could be considered for developing a serological test for gambiense HAT, either individually or in combination. Antigens with potential for inclusion in a test for T. b. rhodesiense HAT were also identified, but because their reactivity was comparatively lower, a search for additional antigens would be required before developing a test for this form of the disease. PMID:27936225

  1. Impact of combined vector-control and vaccination strategies on transmission dynamics of dengue fever: a model-based analysis.

    PubMed

    Knerer, Gerhart; Currie, Christine S M; Brailsford, Sally C

    2015-06-01

    Dengue fever is a vector-borne disease prevalent in tropical and subtropical regions. It is an important public health problem with a considerable and often under-valued disease burden in terms of frequency, cost and quality-of-life. Recent literature reviews have documented the development of mathematical models of dengue fever both to identify important characteristics for future model development as well as to assess the impact of dengue control interventions. Such reviews highlight the importance of short-term cross-protection; antibody-dependent enhancement; and seasonality (in terms of both favourable and unfavourable conditions for mosquitoes). The compartmental model extends work by Bartley (2002) and combines the following factors: seasonality, age-structure, consecutive infection by all four serotypes, cross-protection and immune enhancement, as well as combined vector-host transmission. The model is used to represent dengue transmission dynamics using parameters appropriate for Thailand and to assess the potential impact of combined vector-control and vaccination strategies including routine and catch-up vaccination strategies on disease dynamics. When seasonality and temporary cross-protection between serotypes are included, the model is able to approximate the observed incidence of dengue fever in Thailand. We find vaccination to be the most effective single intervention, albeit with imperfect efficacy (30.2 %) and limited duration of protection. However, in combination, control interventions and vaccination exhibit a marked impact on dengue fever transmission. This study shows that an imperfect vaccine can be a useful weapon in reducing disease spread within the community, although it will be most effective when promoted as one of several strategies for combating dengue fever transmission.

  2. Development and Evaluation of a Pyriproxyfen-treated Device to Control the Dengue Vector, Aedes aegypti (L.) (Diptera: Culicidae)

    DTIC Science & Technology

    2013-03-01

    embryogenesis and adult emergence of sweet - potato whitefly (Ho- moptera, Aleyrodidae). J Econ Entomol 1992; 85: 2113-7. Itoh T. Control of DF/DHF vector...deposition. Ishaaya and Horowitz (1992) found newly deposited eggs (0-1 day old) from female sweet - A PyriProxyfen TreATed device for Ae. Aegypti...Treatment period M e a n m o s q u it o e s p e r h o u s e ( ± S E ) Weeks post-treatment potato whiteflies exposed to pyriproxyfen were less likely to

  3. Development and Assessment of Plant-Based Synthetic Odor Baits for Surveillance and Control of Malaria Vectors

    PubMed Central

    Nyasembe, Vincent O.; Tchouassi, David P.; Kirwa, Hillary K.; Foster, Woodbridge A.; Teal, Peter E. A.; Borgemeister, Christian; Torto, Baldwyn

    2014-01-01

    Background Recent malaria vector control measures have considerably reduced indoor biting mosquito populations. However, reducing the outdoor biting populations remains a challenge because of the unavailability of appropriate lures to achieve this. This study sought to test the efficacy of plant-based synthetic odor baits in trapping outdoor populations of malaria vectors. Methodology and Principal Finding Three plant-based lures ((E)-linalool oxide [LO], (E)-linalool oxide and (E)-β-ocimene [LO + OC], and a six-component blend comprising (E)-linalool oxide, (E)-β-ocimene, hexanal, β-pinene, limonene, and (E)-β-farnesene [Blend C]), were tested alongside an animal/human-based synthetic lure (comprising heptanal, octanal, nonanal, and decanal [Blend F]) and worn socks in a malaria endemic zone in the western part of Kenya. Mosquito Magnet-X (MM-X) and lightless Centre for Disease Control (CDC) light traps were used. Odor-baited traps were compared with traps baited with either solvent alone or solvent + carbon dioxide (controls) for 18 days in a series of randomized incomplete-block designs of days × sites × treatments. The interactive effect of plant and animal/human odor was also tested by combining LO with either Blend F or worn socks. Our results show that irrespective of trap type, traps baited with synthetic plant odors compared favorably to the same traps baited with synthetic animal odors and worn socks in trapping malaria vectors, relative to the controls. Combining LO and worn socks enhanced trap captures of Anopheles species while LO + Blend F recorded reduced trap capture. Carbon dioxide enhanced total trap capture of both plant- and animal/human-derived odors. However, significantly higher proportions of male and engorged female Anopheles gambiae s.l. were caught when the odor treatments did not include carbon dioxide. Conclusion and Significance The results highlight the potential of plant-based odors and specifically linalool oxide, with or

  4. New Recombinant Mycobacterium bovis BCG Expression Vectors: Improving Genetic Control over Mycobacterial Promoters

    PubMed Central

    Kanno, Alex I.; Goulart, Cibelly; Rofatto, Henrique K.; Oliveira, Sergio C.; Leite, Luciana C. C.

    2016-01-01

    The expression of many antigens, stimulatory molecules, or even metabolic pathways in mycobacteria such as Mycobacterium bovis BCG or M. smegmatis was made possible through the development of shuttle vectors, and several recombinant vaccines have been constructed. However, gene expression in any of these systems relied mostly on the selection of natural promoters expected to provide the required level of expression by trial and error. To establish a systematic selection of promoters with a range of strengths, we generated a library of mutagenized promoters through error-prone PCR of the strong PL5 promoter, originally from mycobacteriophage L5. These promoters were cloned upstream of the enhanced green fluorescent protein reporter gene, and recombinant M. smegmatis bacteria exhibiting a wide range of fluorescence levels were identified. A set of promoters was selected and identified as having high (pJK-F8), intermediate (pJK-B7, pJK-E6, pJK-D6), or low (pJK-C1) promoter strengths in both M. smegmatis and M. bovis BCG. The sequencing of the promoter region demonstrated that it was extensively modified (6 to 11%) in all of the plasmids selected. To test the functionality of the system, two different expression vectors were demonstrated to allow corresponding expression levels of the Schistosoma mansoni antigen Sm29 in BCG. The approach used here can be used to adjust expression levels for synthetic and/or systems biology studies or for vaccine development to maximize the immune response. PMID:26850295

  5. New Recombinant Mycobacterium bovis BCG Expression Vectors: Improving Genetic Control over Mycobacterial Promoters.

    PubMed

    Kanno, Alex I; Goulart, Cibelly; Rofatto, Henrique K; Oliveira, Sergio C; Leite, Luciana C C; McFadden, Johnjoe

    2016-04-01

    The expression of many antigens, stimulatory molecules, or even metabolic pathways in mycobacteria such as Mycobacterium bovis BCG or M. smegmatis was made possible through the development of shuttle vectors, and several recombinant vaccines have been constructed. However, gene expression in any of these systems relied mostly on the selection of natural promoters expected to provide the required level of expression by trial and error. To establish a systematic selection of promoters with a range of strengths, we generated a library of mutagenized promoters through error-prone PCR of the strong PL5 promoter, originally from mycobacteriophage L5. These promoters were cloned upstream of the enhanced green fluorescent protein reporter gene, and recombinant M. smegmatis bacteria exhibiting a wide range of fluorescence levels were identified. A set of promoters was selected and identified as having high (pJK-F8), intermediate (pJK-B7, pJK-E6, pJK-D6), or low (pJK-C1) promoter strengths in both M. smegmatis and M. bovisBCG. The sequencing of the promoter region demonstrated that it was extensively modified (6 to 11%) in all of the plasmids selected. To test the functionality of the system, two different expression vectors were demonstrated to allow corresponding expression levels of the Schistosoma mansoni antigen Sm29 in BCG. The approach used here can be used to adjust expression levels for synthetic and/or systems biology studies or for vaccine development to maximize the immune response.

  6. Centers for Disease Control light traps for monitoring Anopheles arabiensis human biting rates in an area with low vector density and high insecticide-treated bed net use.

    PubMed

    Fornadel, Christen M; Norris, Laura C; Norris, Douglas E

    2010-10-01

    Human landing catches (HLCs) are currently the preferred method to determine vector human biting rates (HBRs), which are key determinants of entomologic inoculation rates and important measures for assessing the impact of vector control efforts. Although HLCs are the most direct means of establishing HBRs, they are labor-intensive, and their use is facing increasing ethical concerns. The relationship between Centers for Disease Control (CDC) light traps and HLC collections was evaluated in Macha, Zambia during the 2007-2008 and 2008-2009 rainy seasons. A CDC light trap captured on average 1.91 (95% confidence interval = 1.16-2.28) times as many An. arabiensis per night as an indoor HLC. Additionally, nets treated with deltamethrin did not affect the numbers of An. arabiensis collected. Our results suggest that in regions where use of vector control interventions is high and vector densities are low, CDC light traps can be used to monitor An. arabiensis HBRs.

  7. Novel, Meso-Substituted Cationic Porphyrin Molecule for Photo-Mediated Larval Control of the Dengue Vector Aedes aegypti

    PubMed Central

    Lucantoni, Leonardo; Magaraggia, Michela; Lupidi, Giulio; Ouedraogo, Robert Kossivi; Coppellotti, Olimpia; Esposito, Fulvio; Fabris, Clara; Jori, Giulio; Habluetzel, Annette

    2011-01-01

    Background Control of the mosquito vector population is the most effective strategy currently available for the prevention of dengue fever and the containment of outbreaks. Photo-activated oxidants may represent promising tools for developing effective, safe and ecofriendly novel larvicides. The purpose of this study was to evaluate the potential of the synthetic meso-substituted porphyrin meso-tri(N-methylpyridyl), meso-mono(N-tetradecylpyridyl)porphine (C14) as a photoactivatable larvicide against the dengue vector Aedes (Stegomyia) aegypti. Methodology The photophysical and photochemical properties of the C14 molecule were assessed spectrophotometrically. Photomediated larvicidal efficacy, route of intake and site of action were determined on Ae. aegypti larvae by laboratory bioassays and fluorescence microscopy. Using powdered food pellet for laboratory rodents (a common larval food used in the laboratory) as a carrier for C14, loading-release dynamics, larvicidal efficacy and residual activity of the C14-carrier complex were investigated. Main Findings The C14 molecule was found to exert a potent photosensitizing activity on Ae. aegypti larvae. At irradiation intervals of 12 h and 1 h, at a light intensity of 4.0 mW/cm2, which is 50–100 times lower than that of natural sunlight, LC50 values of 0.1 µM (0.15 mg/l) and 0.5 µM (0.77 mg/l) were obtained, respectively. The molecule was active after ingestion by the larvae and caused irreversible, lethal damage to the midgut and caecal epithelia. The amphiphilic nature of C14 allowed a formulate to be produced that not only was as active against the larvae as C14 in solution, but also possessed a residual activity of at least two weeks, in laboratory conditions. Conclusions The meso-substituted synthetic porphyrin C14, thanks to its photo-sensitizing properties represents an attractive candidate for the development of novel photolarvicides for dengue vector control. PMID:22206031

  8. Vector control improves survival of three species of prairie dogs (Cynomys) in areas considered enzootic for plague

    USGS Publications Warehouse

    Biggins, Dean E.; Godbey, Jerry L.; Gage, Kenneth L.; Carter, Leon G.; Montenieri, John A.

    2010-01-01

    Plague causes periodic epizootics that decimate populations of prairie dogs (PDs) (Cynomys), but the means by which the causative bacterium (Yersinia pestis) persists between epizootics are poorly understood. Plague epizootics in PDs might arise as the result of introductions of Y. pestis from sources outside PD colonies. However, it remains possible that plague persists in PDs during interepizootic periods and is transmitted at low rates among highly susceptible individuals within and between their colonies. If this is true, application of vector control to reduce flea numbers might reduce mortality among PDs. To test whether vector control enhances PD survival in the absence of obvious plague epizootics, we reduced the numbers of fleas (vectors for Y. pestis) 96–98% (1 month posttreatment) on 15 areas involving three species of PDs (Cynomys leucurus, Cynomys parvidens in Utah, and Cynomys ludovicianus in Montana) during 2000–2004 using deltamethrin dust delivered into burrows as a pulicide. Even during years without epizootic plague, PD survival rates at dusted sites were 31–45% higher for adults and 2–34% higher for juveniles compared to survival rates at nondusted sites. Y. pestis was cultured from 49 of the 851 flea pools tested (6882 total fleas) and antibodies against Y. pestis were identified in serum samples from 40 of 2631 PDs. Although other explanations are possible, including transmission of other potentially fatal pathogens by fleas, ticks, or other ectoparasites, our results suggest that plague might be maintained indefinitely in PD populations in the absence of free epizootics and widespread mortality among these animals. If PDs and their fleas support enzootic cycles of plague transmission, there would be important implications for the conservation of these animals and other species.

  9. Cultivation-Independent Methods Reveal Differences among Bacterial Gut Microbiota in Triatomine Vectors of Chagas Disease

    PubMed Central

    da Mota, Fabio Faria; Marinho, Lourena Pinheiro; Moreira, Carlos José de Carvalho; Lima, Marli Maria; Mello, Cícero Brasileiro; Garcia, Eloi Souza; Carels, Nicolas; Azambuja, Patricia

    2012-01-01

    Background Chagas disease is a trypanosomiasis whose agent is the protozoan parasite Trypanosoma cruzi, which is transmitted to humans by hematophagous bugs known as triatomines. Even though insecticide treatments allow effective control of these bugs in most Latin American countries where Chagas disease is endemic, the disease still affects a large proportion of the population of South America. The features of the disease in humans have been extensively studied, and the genome of the parasite has been sequenced, but no effective drug is yet available to treat Chagas disease. The digestive tract of the insect vectors in which T. cruzi develops has been much less well investigated than blood from its human hosts and constitutes a dynamic environment with very different conditions. Thus, we investigated the composition of the predominant bacterial species of the microbiota in insect vectors from Rhodnius, Triatoma, Panstrongylus and Dipetalogaster genera. Methodology/Principal Findings Microbiota of triatomine guts were investigated using cultivation-independent methods, i.e., phylogenetic analysis of 16s rDNA using denaturing gradient gel electrophoresis (DGGE) and cloned-based sequencing. The Chao index showed that the diversity of bacterial species in triatomine guts is low, comprising fewer than 20 predominant species, and that these species vary between insect species. The analyses showed that Serratia predominates in Rhodnius, Arsenophonus predominates in Triatoma and Panstrongylus, while Candidatus Rohrkolberia predominates in Dipetalogaster. Conclusions/Significance The microbiota of triatomine guts represents one of the factors that may interfere with T. cruzi transmission and virulence in humans. The knowledge of its composition according to insect species is important for designing measures of biological control for T. cruzi. We found that the predominant species of the bacterial microbiota in triatomines form a group of low complexity whose structure

  10. Microbial symbiosis and the control of vector-borne pathogens in tsetse flies, human lice, and triatomine bugs.

    PubMed

    Sassera, Davide; Epis, Sara; Pajoro, Massimo; Bandi, Claudio

    2013-09-01

    Symbiosis is a widespread biological phenomenon, and is particularly common in arthropods. Bloodsucking insects are among the organisms that rely on beneficial bacterial symbionts to complement their unbalanced diet. This review is focused on describing symbiosis, and possible strategies for the symbiont-based control of insects and insect-borne diseases, in three bloodsucking insects of medical importance: the flies of the genus Glossina, the lice of the genus Pediculus, and triatomine bugs of the subfamily Triatominae. Glossina flies are vector of Trypanosoma brucei, the causative agent of sleeping sickness and other pathologies. They are also associated with two distinct bacterial symbionts, the primary symbiont Wigglesworthia spp., and the secondary, culturable symbiont Sodalis glossinidius. The primary symbiont of human lice, Riesia pediculicola, has been shown to be fundamental for the host, due to its capacity to synthesize B-group vitamins. An antisymbiotic approach, with antibiotic treatment targeted on the lice symbionts, could represent an alternative strategy to control these ectoparasites. In the case of triatominae bugs, the genetic modification of their symbiotic Rhodococcus bacteria, for production of anti-Trypanosoma molecules, is an example of paratransgenesis, i.e. the use of symbiotic microorganism engineered in order to reduce the vector competence of the insect host.

  11. Microbial symbiosis and the control of vector-borne pathogens in tsetse flies, human lice, and triatomine bugs

    PubMed Central

    Sassera, Davide; Epis, Sara; Pajoro, Massimo; Bandi, Claudio

    2013-01-01

    Symbiosis is a widespread biological phenomenon, and is particularly common in arthropods. Bloodsucking insects are among the organisms that rely on beneficial bacterial symbionts to complement their unbalanced diet. This review is focused on describing symbiosis, and possible strategies for the symbiont-based control of insects and insect-borne diseases, in three bloodsucking insects of medical importance: the flies of the genus Glossina, the lice of the genus Pediculus, and triatomine bugs of the subfamily Triatominae. Glossina flies are vector of Trypanosoma brucei, the causative agent of sleeping sickness and other pathologies. They are also associated with two distinct bacterial symbionts, the primary symbiont Wigglesworthia spp., and the secondary, culturable symbiont Sodalis glossinidius. The primary symbiont of human lice, Riesia pediculicola, has been shown to be fundamental for the host, due to its capacity to synthesize B-group vitamins. An antisymbiotic approach, with antibiotic treatment targeted on the lice symbionts, could represent an alternative strategy to control these ectoparasites. In the case of triatominae bugs, the genetic modification of their symbiotic Rhodococcus bacteria, for production of anti-Trypanosoma molecules, is an example of paratransgenesis, i.e. the use of symbiotic microorganism engineered in order to reduce the vector competence of the insect host. PMID:24188239

  12. Vector control measures failed to affect genetic structure of Aedes aegypti in a sentinel metropolitan area of Brazil.

    PubMed

    Souza, Kathleen R; Ribeiro, Gilmar; Silva dos Santos, Carlos Gustavo; de Lima, Eliaci Couto; Melo, Paulo R S; Reis, Mitermayer G; Blanton, Ronald E; Silva, Luciano K

    2013-12-01

    In order to evaluate subpopulation differentiation, effective population size (Ne) and evidence for population bottlenecks at various geographic levels, Aedes aegypti larvae were collected longitudinally from 2007 to 2009 from four areas in the city of Salvador, Brazil. The DNA from each larva was isolated and genotyped with five independent microsatellite markers. FST and Jost's D revealed significant population structuring (P<0.05) at the municipal and regional levels, while only RST was able to detect genetic differentiation at the level of strata within these areas. Ne analysis from longitudinal data did not show any evidence of significant change in population structure. The census population measured by the house index, however, showed a significant trend toward decrease in these areas. Active vector control measures did contribute to vector reduction, but this was not enough to decrease A. aegypti population genetic diversity in Salvador. The understanding of A. aegypti population dynamics may be helpful for planning and evaluation of control measures to make them more effective.

  13. A Method for Integrating Thrust-Vectoring and Actuated Forebody Strakes with Conventional Aerodynamic Controls on a High-Performance Fighter Airplane

    NASA Technical Reports Server (NTRS)

    Lallman, Frederick J.; Davidson, John B.; Murphy, Patrick C.

    1998-01-01

    A method, called pseudo controls, of integrating several airplane controls to achieve cooperative operation is presented. The method eliminates conflicting control motions, minimizes the number of feedback control gains, and reduces the complication of feedback gain schedules. The method is applied to the lateral/directional controls of a modified high-performance airplane. The airplane has a conventional set of aerodynamic controls, an experimental set of thrust-vectoring controls, and an experimental set of actuated forebody strakes. The experimental controls give the airplane additional control power for enhanced stability and maneuvering capabilities while flying over an expanded envelope, especially at high angles of attack. The flight controls are scheduled to generate independent body-axis control moments. These control moments are coordinated to produce stability-axis angular accelerations. Inertial coupling moments are compensated. Thrust-vectoring controls are engaged according to their effectiveness relative to that of the aerodynamic controls. Vane-relief logic removes steady and slowly varying commands from the thrust-vectoring controls to alleviate heating of the thrust turning devices. The actuated forebody strakes are engaged at high angles of attack. This report presents the forward-loop elements of a flight control system that positions the flight controls according to the desired stability-axis accelerations. This report does not include the generation of the required angular acceleration commands by means of pilot controls or the feedback of sensed airplane motions.

  14. The role of the United States military in the development of vector control products, including insect repellents, insecticides, and bed nets.

    PubMed

    Kitchen, Lynn W; Lawrence, Kendra L; Coleman, Russell E

    2009-06-01

    Arthropod-borne diseases such as malaria, dengue, scrub typhus, and leishmaniasis continue to pose a significant threat to U.S. military forces deployed in support of operational and humanitarian missions. These diseases are transmitted by a variety of arthropods, including mosquitoes, ticks, chiggers, sand flies, and biting midges. In addition to disease threats, biting arthropods can cause dermatitis, allergic reactions, and sleep loss; therefore, monitoring of vector impact and integrated use of personal protective measures (PPM) and methods to reduce the vector populations are needed to protect service members. The U.S. military has played a vital role in vector identification tools and the development and testing of many of the most effective PPM and vector control products available today, including the topical repellent DEET and the repellent/insecticide permethrin, which is applied to clothing and bed nets. Efforts to develop superior products are ongoing. Although the U.S. military often needs vector control products with rather specific properties (e.g., undetectable, long-lasting in multiple climates) in order to protect its service members, many Department of Defense vector control products have had global impacts on endemic disease control.

  15. Design of smart composite platforms for adaptive trust vector control and adaptive laser telescope for satellite applications

    NASA Astrophysics Data System (ADS)

    Ghasemi-Nejhad, Mehrdad N.

    2013-04-01

    This paper presents design of smart composite platforms for adaptive trust vector control (TVC) and adaptive laser telescope for satellite applications. To eliminate disturbances, the proposed adaptive TVC and telescope systems will be mounted on two analogous smart composite platform with simultaneous precision positioning (pointing) and vibration suppression (stabilizing), SPPVS, with micro-radian pointing resolution, and then mounted on a satellite in two different locations. The adaptive TVC system provides SPPVS with large tip-tilt to potentially eliminate the gimbals systems. The smart composite telescope will be mounted on a smart composite platform with SPPVS and then mounted on a satellite. The laser communication is intended for the Geosynchronous orbit. The high degree of directionality increases the security of the laser communication signal (as opposed to a diffused RF signal), but also requires sophisticated subsystems for transmission and acquisition. The shorter wavelength of the optical spectrum increases the data transmission rates, but laser systems require large amounts of power, which increases the mass and complexity of the supporting systems. In addition, the laser communication on the Geosynchronous orbit requires an accurate platform with SPPVS capabilities. Therefore, this work also addresses the design of an active composite platform to be used to simultaneously point and stabilize an intersatellite laser communication telescope with micro-radian pointing resolution. The telescope is a Cassegrain receiver that employs two mirrors, one convex (primary) and the other concave (secondary). The distance, as well as the horizontal and axial alignment of the mirrors, must be precisely maintained or else the optical properties of the system will be severely degraded. The alignment will also have to be maintained during thruster firings, which will require vibration suppression capabilities of the system as well. The innovative platform has been

  16. Preliminary Characterization of the Altair Lunar Lander Slosh Dynamics and Some Implications for the Thrust Vector Control Design

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.; Strahan, Alan; Tanimoto, Rebekah; Casillas, Arturo

    2010-01-01

    This paper describes a conceptual design of the Thrust Vector Control (TVC) system and preliminary modeling of propellant slosh, for the Altair Lunar Lander. Altair is a vehicle element of the NASA Constellation Program aimed at returning humans to the moon. Guidance, Navigation, and Control (GN&C) is the measurement and control of spacecraft position, velocity, and attitude in support of mission objectives. One key GN&C function is the commanding of effectors that control attitude and impart delta V on the vehicle, utilizing both reaction control system (RCS) thrusters and throttling and TVC gimbaling of the vehicle main engine. Both the Altair descent and ascent modules carry fuel tanks. During thrusting maneuvers, the sloshing of liquid fuels in partially filled tanks can interact with the controlled system in such a way as to cause the overall system to be unstable. These fuel tanks must be properly placed, relative to the spacecraft's c.m., to avoid any unstable interactions. Following this will be a discussion of propellant slosh modeling work performed for the present vehicle configuration, including slosh frequency and participatory fluid mass predictions. Knowing the range of slosh mode frequencies over mission phases, the TVC bandwidth must be carefully selected so as not to excite the slosh modes at those frequencies. The likely need to increase the damping factor of slosh modes via baffles will also be discussed. To conclude, a discussion of operations procedures aimed at minimizing TVC-slosh interactions will be given.

  17. wFlu: Characterization and Evaluation of a Native Wolbachia from the Mosquito Aedes fluviatilis as a Potential Vector Control Agent

    PubMed Central

    Gonçalves, Daniela da Silva; Moreira, Luciano Andrade

    2013-01-01

    There is currently considerable interest and practical progress in using the endosymbiotic bacteria Wolbachia as a vector control agent for human vector-borne diseases. Such vector control strategies may require the introduction of multiple, different Wolbachia strains into target vector populations, necessitating the identification and characterization of appropriate endosymbiont variants. Here, we report preliminary characterization of wFlu, a native Wolbachia from the neotropical mosquito Aedes fluviatilis, and evaluate its potential as a vector control agent by confirming its ability to cause cytoplasmic incompatibility, and measuring its effect on three parameters determining host fitness (survival, fecundity and fertility), as well as vector competence (susceptibility) for pathogen infection. Using an aposymbiotic strain of Ae. fluviatilis cured of its native Wolbachia by antibiotic treatment, we show that in its natural host wFlu causes incomplete, but high levels of, unidirectional cytoplasmic incompatibility, has high rates of maternal transmission, and no detectable fitness costs, indicating a high capacity to rapidly spread through host populations. However, wFlu does not inhibit, and even enhances, oocyst infection with the avian malaria parasite Plasmodium gallinaceum. The stage- and sex-specific density of wFlu was relatively low, and with limited tissue distribution, consistent with the lack of virulence and pathogen interference/symbiont-mediated protection observed. Unexpectedly, the density of wFlu was also shown to be specifically-reduced in the ovaries after bloodfeeding Ae. fluviatilis. Overall, our observations indicate that the Wolbachia strain wFlu has the potential to be used as a vector control agent, and suggests that appreciable mutualistic coevolution has occurred between this endosymbiont and its natural host. Future work will be needed to determine whether wFlu has virulent host effects and/or exhibits pathogen interference when

  18. Control algorithm for the inverter fed induction motor drive with DC current feedback loop based on principles of the vector control

    SciTech Connect

    Vuckovic, V.; Vukosavic, S. )

    1992-01-01

    This paper brings out a control algorithm for VSI fed induction motor drives based on the converter DC link current feedback. It is shown that the speed and flux can be controlled over the wide speed and load range quite satisfactorily for simpler drives. The base commands of both the inverter voltage and frequency are proportional to the reference speed, but each of them is further modified by the signals derived from the DC current sensor. The algorithm is based on the equations well known from the vector control theory, and is aimed to obtain the constant rotor flux and proportionality between the electrical torque, the slip frequency and the active component of the stator current. In this way, the problems of slip compensation, Ri compensation and correction of U/f characteristics are solved in the same time. Analytical considerations and computer simulations of the proposed control structure are in close agreement with the experimental results measured on a prototype drive.

  19. Sexual chemoecology of mosquitoes (Diptera, Culicidae): Current knowledge and implications for vector control programs.

    PubMed

    Vaníčková, Lucie; Canale, Angelo; Benelli, Giovanni

    2017-04-01

    Mosquitoes (Diptera: Culicidae) act as vectors of medical and veterinary importance, due to their ability to transmit many pathogens and parasites. Renewed interest has been recently devoted to the potential of sterile insect technique (SIT) for mosquito suppression. However, the success of the SIT is mostly dependent on the ability of sterile males to compete for mates with the wild ones in the field. Nevertheless, little is known on the sexual chemical ecology of mosquitoes, with special reference to the role of chemical signals in males. We reviewed the current knowledge on mosquito sexual chemical ecology and other key cues affecting courtship and mating behavior. The information available on the aggregation and sex pheromones in mosquito males is rather limited. To the best of our knowledge, the components of the aggregation pheromone stimulating swarming mechanisms have been fully characterized only for Aedes aegypti, while evidence for aggregation pheromones in other mosquito species remains elusive. Further research on this issue is needed, as well as to dissect the relative importance of visual (with special reference to swarming landmarks), vibrational, olfactory and tactile cues perceived during swarming and mate. On the other hand, more knowledge is available for cuticular hydrocarbons, which modulate mating behavior in several species of economic importance. These compounds, coupled with volatile aggregation components, have potential interest for the development of monitoring and trapping systems. In addition, the analyses of cuticular hydrocarbons are essential for discrimination between closely related mosquito species and/or populations.

  20. Turning cigarette butt waste into an alternative control tool against an insecticide-resistant mosquito vector.

    PubMed

    Dieng, Hamady; Rajasaygar, Sudha; Ahmad, Abu Hassan; Ahmad, Hamdan; Rawi, Che Salmah Md; Zuharah, Wan Fatma; Satho, Tomomitsu; Miake, Fumio; Fukumitsu, Yuki; Saad, Ahmad Ramli; Ghani, Idris Abd; Vargas, Ronald Enrique Morales; Majid, Abdul Hafiz Ab; Abubakar, Sazaly

    2013-12-01

    Annually, 4.5 trillion cigarette butts (CBs) are flicked into our environment. Evidence exists that CB waste is deadly to aquatic life, but their lethality to the aquatic life of the main dengue vector is unknown. CBs are full of toxicants that occur naturally, during planting and manufacturing, which may act as larvicidal agents. We assessed Aedes aegypti vulnerability to Marlboro butts during its development. Overall, CBs showed insecticidal activities against larvae. At early phases of development, mortality rates were much higher in two CBs solution (2CBSol) and 3CBSol microcosms (MICRs). Larval survival gradually decreased with development in 1CBSol-MICRs. However, in great presence of CBs, mortality was high even for the late developmental stages. These results suggest that A. aegypti larvae are vulnerable to CB presence in their habitats, but this effect was seen most during the early developmental phases and in the presence of increased amounts of cigarette remnants. CB filters are being used as raw material in many sectors, i.e., brick, art, fashion, plastic industries, as a practical solution to the pollution problem, the observed butt waste toxicity to mosquito larvae open new avenues for the identification of novel insecticide products.

  1. Current Perspectives on Plague Vector Control in Madagascar: Susceptibility Status of Xenopsylla cheopis to 12 Insecticides.

    PubMed

    Miarinjara, Adélaïde; Boyer, Sébastien

    2016-02-01

    Plague is a rodent disease transmissible to humans by infected flea bites, and Madagascar is one of the countries with the highest plague incidence in the world. This study reports the susceptibility of the main plague vector Xenopsylla cheopis to 12 different insecticides belonging to 4 insecticide families (carbamates, organophosphates, pyrethroids and organochlorines). Eight populations from different geographical regions of Madagascar previously resistant to deltamethrin were tested with a World Health Organization standard bioassay. Insecticide susceptibility varied amongst populations, but all of them were resistant to six insecticides belonging to pyrethroid and carbamate insecticides (alphacypermethrin, lambdacyhalothrin, etofenprox, deltamethrin, bendiocarb and propoxur). Only one insecticide (dieldrin) was an efficient pulicide for all flea populations. Cross resistances were suspected. This study proposes at least three alternative insecticides (malathion, fenitrothion and cyfluthrin) to replace deltamethrin during plague epidemic responses, but the most efficient insecticide may be different for each population studied. We highlight the importance of continuous insecticide susceptibility surveillance in the areas of high plague risk in Madagascar.

  2. Current Perspectives on Plague Vector Control in Madagascar: Susceptibility Status of Xenopsylla cheopis to 12 Insecticides

    PubMed Central

    Miarinjara, Adélaïde; Boyer, Sébastien

    2016-01-01

    Plague is a rodent disease transmissible to humans by infected flea bites, and Madagascar is one of the countries with the highest plague incidence in the world. This study reports the susceptibility of the main plague vector Xenopsylla cheopis to 12 different insecticides belonging to 4 insecticide families (carbamates, organophosphates, pyrethroids and organochlorines). Eight populations from different geographical regions of Madagascar previously resistant to deltamethrin were tested with a World Health Organization standard bioassay. Insecticide susceptibility varied amongst populations, but all of them were resistant to six insecticides belonging to pyrethroid and carbamate insecticides (alphacypermethrin, lambdacyhalothrin, etofenprox, deltamethrin, bendiocarb and propoxur). Only one insecticide (dieldrin) was an efficient pulicide for all flea populations. Cross resistances were suspected. This study proposes at least three alternative insecticides (malathion, fenitrothion and cyfluthrin) to replace deltamethrin during plague epidemic responses, but the most efficient insecticide may be different for each population studied. We highlight the importance of continuous insecticide susceptibility surveillance in the areas of high plague risk in Madagascar. PMID:26844772

  3. Dopamine Receptor Antagonists as New Mode-of-Action Insecticide Leads for Control of Aedes and Culex Mosquito Vectors

    PubMed Central

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

    2015-01-01

    Background 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. Methods/Results 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. Conclusions 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

  4. Constructing of DNA vectors with controlled nanosize and single dispersion by block copolymer coating gold nanoparticles as template assembly

    NASA Astrophysics Data System (ADS)

    Li, Junbo; Wu, Wenlan; Gao, Jiayu; Liang, Ju; Zhou, Huiyun; Liang, Lijuan

    2017-03-01

    Synthesized vectors with nanoscale size and stable colloid dispersion are highly desirable for improving gene delivery efficiency. Here, a core-shell template particle was constructed with polyethylene glycol- b-poly1-(3-aminopropyl)-3-(2-methacryloyloxy propylimidazolium bromine) (PEG- b-PAMPImB) coating gold nanoparticles (PEG- b-PAMPImB-@-Au NPs) for loading DNA and delivering in vitro. Data from transmission electron microscopy (TEM) and dynamic light scattering (DLS) suggest that these nanoplexes, by forming an electrostatic complex with DNA at the inner PAMPImB shell, offer steric protection for the outer PEG corona leading to single dispersion and small size. Notably, higher colloid stability and lower cytotoxicity were achieved with these nanoplexes when compared with PAMPImB monolayer-coated gold nanoparticles (Au NPs). Confocal laser scanning microscopy and intracellular trafficking TEM further indicate that the nanoplexes can translocate across the cell membrane and partly enter the nucleus for high efficient expression. Thus, template assembly represents a promising approach to control the size and colloid stability of gene vectors and ensure safety and efficiency of DNA delivery.

  5. International network for capacity building for the control of emerging viral vector-borne zoonotic diseases: ARBO-ZOONET.

    PubMed

    Ahmed, J; Bouloy, M; Ergonul, O; Fooks, Ar; Paweska, J; Chevalier, V; Drosten, C; Moormann, R; Tordo, N; Vatansever, Z; Calistri, P; Estrada-Pena, A; Mirazimi, A; Unger, H; Yin, H; Seitzer, U

    2009-03-26

    Arboviruses are arthropod-borne viruses, which include West Nile fever virus (WNFV), a mosquito-borne virus, Rift Valley fever virus (RVFV), a mosquito-borne virus, and Crimean-Congo haemorrhagic fever virus (CCHFV), a tick-borne virus. These arthropod-borne viruses can cause disease in different domestic and wild animals and in humans, posing a threat to public health because of their epidemic and zoonotic potential. In recent decades, the geographical distribution of these diseases has expanded. Outbreaks of WNF have already occurred in Europe, especially in the Mediterranean basin. Moreover, CCHF is endemic in many European countries and serious outbreaks have occurred, particularly in the Balkans, Turkey and Southern Federal Districts of Russia. In 2000, RVF was reported for the first time outside the African continent, with cases being confirmed in Saudi Arabia and Yemen. This spread was probably caused by ruminant trade and highlights that there is a threat of expansion of the virus into other parts of Asia and Europe. In the light of global warming and globalisation of trade and travel, public interest in emerging zoonotic diseases has increased. This is especially evident regarding the geographical spread of vector-borne diseases. A multi-disciplinary approach is now imperative, and groups need to collaborate in an integrated manner that includes vector control, vaccination programmes, improved therapy strategies, diagnostic tools and surveillance, public awareness, capacity building and improvement of infrastructure in endemic regions.

  6. Clinical presentation of human African trypanosomiasis in Zambia is linked to the existence of strains of Trypanosoma brucei rhodesiense with varied virulence: two case reports

    PubMed Central

    2014-01-01

    Introduction Trypanosoma brucei rhodesiense typically causes acute and severe human African trypanosomiasis in Zambia and other countries in Eastern and Southern Africa. Although a few atypical cases of chronic and mild forms of this disease were reported in Zambia more than 40 years ago, no such cases have been diagnosed over the last four decades. Case presentations For the first case, a 19-year-old Black African woman from the Eastern Province of Zambia presented with symptoms and signs of an atypical chronic and mild form of the disease for a period of 2 years. For the second case, a 16-year-old Black African boy from the Northern Province presented with symptoms and signs of a typical acute and severe form of the disease for 3 weeks. Conclusion Two strains of T. b. rhodesiense with varying degrees of virulence still do exist in Zambia. This has implications for control strategies at the national level. PMID:24529084

  7. Tripartite interactions between tsetse flies, Sodalis glossinidius and trypanosomes--an epidemiological approach in two historical human African trypanosomiasis foci in Cameroon.

    PubMed

    Farikou, Oumarou; Njiokou, Flobert; Mbida Mbida, Jean A; Njitchouang, Guy R; Djeunga, Hugues Nana; Asonganyi, Tazoacha; Simarro, Pere P; Cuny, Gérard; Geiger, Anne

    2010-01-01

    Epidemiological surveys were conducted in two historical human African trypanosomiasis foci in South Cameroon, Bipindi and Campo. In each focus, three sampling areas were defined. In Bipindi, only Glossina palpalis was identified, whereas four species were identified in Campo, G. palpalis being highly predominant (93%). For further analyses, 75 flies were randomly chosen among the flies trapped in each of the six villages. Large and statistically significant differences were recorded between both (1) the prevalence of Sodalis glossinidius (tsetse symbiont) and the prevalence of trypanosome infection of the major fly species G. p. palpalis and (2) the respective prevalence of symbiont and infection between the two foci. Despite these differences, the rate of infected flies harbouring the symbiont was very similar (75%) in both foci, suggesting that symbionts favour fly infection by trypanosomes. This hypothesis was statistically tested and assessed, showing that S. glossinidius is potentially an efficient target for controlling tsetse fly vectorial competence and consequently sleeping sickness.

  8. Key Source Habitats and Potential Dispersal of Triatoma infestans Populations in Northwestern Argentina: Implications for Vector Control

    PubMed Central

    Gürtler, Ricardo E.; Cecere, María C.; Fernández, María del Pilar; Vazquez-Prokopec, Gonzalo M.; Ceballos, Leonardo A.; Gurevitz, Juan M.; Kitron, Uriel; Cohen, Joel E.

    2014-01-01

    Background Triatoma infestans —the principal vector of the infection that causes Chagas disease— defies elimination efforts in the Gran Chaco region. This study identifies the types of human-made or -used structures that are key sources of these bugs in the initial stages of house reinfestation after an insecticide spraying campaign. Methodology and Principal Findings We measured demographic and blood-feeding parameters at two geographic scales in 11 rural communities in Figueroa, northwest Argentina. Of 1,297 sites searched in spring, 279 (21.5%) were infested. Bug abundance per site and female fecundity differed significantly among habitat types (ecotopes) and were highly aggregated. Domiciles (human sleeping quarters) had maximum infestation prevalence (38.7%), human-feeding bugs and total egg production, with submaximal values for other demographic and blood-feeding attributes. Taken collectively peridomestic sites were three times more often infested than domiciles. Chicken coops had greater bug abundance, blood-feeding rates, engorgement status, and female fecundity than pig and goat corrals. The host-feeding patterns were spatially structured yet there was strong evidence of active dispersal of late-stage bugs between ecotopes. Two flight indices predicted that female fliers were more likely to originate from kitchens and domiciles, rejecting our initial hypothesis that goat and pig corrals would dominate. Conclusions and Significance Chicken coops and domiciles were key source habitats fueling rapid house reinfestation. Focusing control efforts on ecotopes with human-fed bugs (domiciles, storerooms, goat corrals) would neither eliminate the substantial contributions to bug population growth from kitchens, chicken coops, and pig corrals nor stop dispersal of adult female bugs from kitchens. Rather, comprehensive control of the linked network of ecotopes is required to prevent feeding on humans, bug population growth, and bug dispersal simultaneously. Our

  9. Spatial Orientation and Balance Control Changes Induced by Altered Gravito-Inertial Force Vectors

    NASA Technical Reports Server (NTRS)

    Kaufman, Galen D.; Wood, Scott J.; Gianna, Claire C.; Black, F. Owen; Paloski, William H.; Dawson, David L. (Technical Monitor)

    1999-01-01

    Seventeen healthy and eight vestibular deficient subjects were exposed to an interaural centripetal acceleration of 1 G (resultant 45 deg roll tilt of 1.4 G) on a 0.8 meter radius centrifuge for a period of 90 minutes in the dark. The subjects sat with head fixed upright, except every 4 of 10 minutes when instructed to rotate their head so that their nose and eyes pointed towards a visual point switched on every 3 to 5 seconds at random places (within +/- 30 deg) in the Earth horizontal plane. Motion sickness caused some subjects to limit their head movements during significant portions of the 90 minute period, and led three normal subjects to stop the test earlier. Eye movements, including directed saccades for subjective Earth- and head-referenced planes, were recorded before, during, and immediately after centrifugation using electro-oculography. Postural stability measurements were made before and within ten minutes after centrifugation. In normal subjects, postural sway and multisegment body kinematics were gathered during an eyes-closed head movement cadence (sway-referenced support platform), and in response to translational/rotational platform perturbations. A significant increase in postural sway, segmental motion amplitude and hip frequency was observed after centrifugation. This effect was short-lived, with a recovery time of several postural test trials. There were also asymmetries in the direction of post-centrifugation center of sway and head tilt which depended on the subject's orientation during the centrifugation adaptation period (left ear or right ear out). To delineate the effect of the magnitude of the gravito-inertial vector versus its direction during the adaptive centrifugation period, we tilted eight normal subjects in the roll axis at a 45 deg angle in the dark for 90 minutes without rotational motion. Their postural responses did not change following the period of tilt. Based on verbal reports, normal subjects overestimated roll

  10. Human African trypanosomiasis: a latex agglutination field test for quantifying IgM in cerebrospinal fluid.

    PubMed Central

    Lejon, V.; Büscher, P.; Sema, N. H.; Magnus, E.; Van Meirvenne, N.

    1998-01-01

    LATEX/IgM, a rapid agglutination test for the semi-quantitative detection of IgM in cerebrospinal fluid of patients with African trypanosomiasis, is described in this article. The lyophilized reagent has been designed for field use and remains stable at 45 degrees C for one year. The test has been evaluated on cerebrospinal fluid samples from trypanosome-infected and non-infected patients, by comparison with commercial latex agglutination, radial immunodiffusion, and nephelometry. All test systems yielded similar results. PMID:10191550

  11. Kynurenine pathway inhibition reduces central nervous system inflammation in a model of human African trypanosomiasis.

    PubMed

    Rodgers, Jean; Stone, Trevor W; Barrett, Michael P; Bradley, Barbara; Kennedy, Peter G E

    2009-05-01

    Human African trypanosomiasis, or sleeping sickness, is caused by the protozoan parasites Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense, and is a major cause of systemic and neurological disability throughout sub-Saharan Africa. Following early-stage disease, the trypanosomes cross the blood-brain barrier to invade the central nervous system leading to the encephalitic, or late stage, infection. Treatment of human African trypanosomiasis currently relies on a limited number of highly toxic drugs, but untreated, is invariably fatal. Melarsoprol, a trivalent arsenical, is the only drug that can be used to cure both forms of the infection once the central nervous system has become involved, but unfortunately, this drug induces an extremely severe post-treatment reactive encephalopathy (PTRE) in up to 10% of treated patients, half of whom die from this complication. Since it is unlikely that any new and less toxic drug will be developed for treatment of human African trypanosomiasis in the near future, increasing attention is now being focussed on the potential use of existing compounds, either alone or in combination chemotherapy, for improved efficacy and safety. The kynurenine pathway is the major pathway in the metabolism of tryptophan. A number of the catabolites produced along this pathway show neurotoxic or neuroprotective activities, and their role in the generation of central nervous system inflammation is well documented. In the current study, Ro-61-8048, a high affinity kynurenine-3-monooxygenase inhibitor, was used to determine the effect of manipulating the kynurenine pathway in a highly reproducible mouse model of human African trypanosomiasis. It was found that Ro-61-8048 treatment had no significant effect (P = 0.4445) on the severity of the neuroinflammatory pathology in mice during the early central nervous system stage of the disease when only a low level of inflammation was present. However, a significant (P = 0.0284) reduction in

  12. How can molecular diagnostics contribute to the elimination of human African trypanosomiasis?

    PubMed

    Büscher, Philippe; Deborggraeve, Stijn

    2015-05-01

    A variety of molecular diagnostic tests for human African trypanosomiasis (HAT) (sleeping sickness) has been developed. Some are effectively used for research and confirmation diagnosis in travel medicine, usually following non-standardized protocols. Others have become commercially available as diagnostic kits. WHO aims to eliminate HAT as a public health problem by the year 2020, and zero transmission by the year 2030. This article gives an overview of the recent progress in molecular diagnostics for sleeping sickness, including the most recent data on test performances. Also discussed is how molecular diagnostics can play an important role in the process toward the elimination of HAT.

  13. Optimal efficiency vector control of induction motor drive system for drum washing machine

    NASA Astrophysics Data System (ADS)

    Lee, Won Cheol; Yu, Jae Sung; Jang, Bong An; Won, Chung Yuen

    2005-12-01

    In home appliances, electric energy is optimally controlled by using power electronics technology, creating a comfortable environment in terms of energy saving, low sound generation, and reduced time consumption. Usually simplicity and robustness make the three phase induction motor attractive for use in domestic appliance, including washing machines. Two main types of domestic washing machine have evolved. We focus on efficiency of the front loading machine favored in Europe, which has a horizontal drum axis. This paper presents the control algorithm for optimal efficiency drives of an induction motor for drum washing machine. This system uses a simple model of the induction motor that include equations of the iron losses. The proposed optimal efficiency control algorithm calculates commands of the reference torque and flux currents for the flux oriented control of the induction motor. The proposed algorithm is verified through digital simulation.

  14. Harmonic domain modelling of three phase thyristor-controlled reactors by means of switching vectors and discrete convolutions

    SciTech Connect

    Rico, J.J.; Acha, E.; Miller, T.J.E.

    1996-07-01

    The main objective of this paper is to report on a newly developed three phase Thyristor Controlled Reactor (TCR) model which is based on the use of harmonic switching vectors and discrete convolutions. This model is amenable to direct frequency domain operations and provides a fast and reliable means for assessing 6- and 12-pulse TCR plant performance at harmonic frequencies. The use of alternate time domain and frequency domain representations is avoided as well as the use of FFTs. In this approach, each single phase unit of the TCR is modelled as a voltage-dependent harmonic Norton equivalent where all the harmonics and cross-couplings between harmonics are explicitly shown. This model is suitable for direct incorporation into the harmonic domain frame of reference where all the busbars, phases, harmonics and cross-couplings between harmonics are combined together for a unified iterative solution through a Newton-Raphson technique exhibiting quadratic convergence.

  15. A randomized longitudinal factorial design to assess malaria vector control and disease management interventions in rural Tanzania.

    PubMed

    Kramer, Randall A; Mboera, Leonard E G; Senkoro, Kesheni; Lesser, Adriane; Shayo, Elizabeth H; Paul, Christopher J; Miranda, Marie Lynn

    2014-05-16

    The optimization of malaria control strategies is complicated by constraints posed by local health systems, infrastructure, limited resources, and the complex interactions between infection, disease, and treatment. The purpose of this paper is to describe the protocol of a randomized factorial study designed to address this research gap. This project will evaluate two malaria control interventions in Mvomero District, Tanzania: (1) a disease management strategy involving early detection and treatment by community health workers using rapid diagnostic technology; and (2) vector control through community-supported larviciding. Six study villages were assigned to each of four groups (control, early detection and treatment, larviciding, and early detection and treatment plus larviciding). The primary endpoint of interest was change in malaria infection prevalence across the intervention groups measured during annual longitudinal cross-sectional surveys. Recurring entomological surveying, household surveying, and focus group discussions will provide additional valuable insights. At baseline, 962 households across all 24 villages participated in a household survey; 2,884 members from 720 of these households participated in subsequent malariometric surveying. The study design will allow us to estimate the effect sizes of different intervention mixtures. Careful documentation of our study protocol may also serve other researchers designing field-based intervention trials.

  16. S argassum muticum-synthesized silver nanoparticles: an effective control tool against mosquito vectors and bacterial pathogens.

    PubMed

    Madhiyazhagan, Pari; Murugan, Kadarkarai; Kumar, Arjunan Naresh; Nataraj, Thiyagarajan; Dinesh, Devakumar; Panneerselvam, Chellasamy; Subramaniam, Jayapal; Mahesh Kumar, Palanisamy; Suresh, Udaiyan; Roni, Mathath; Nicoletti, Marcello; Alarfaj, Abdullah A; Higuchi, Akon; Munusamy, Murugan A; Benelli, Giovanni

    2015-11-01

    Mosquito-borne diseases represent a deadly threat for millions of people worldwide. Furthermore, pathogens and parasites polluting water also constitute a severe plague for populations of developing countries. In this research, silver nanoparticles (AgNP) were synthesized using the aqueous extract of the seaweed Sargassum muticum. The production of AgNP was confirmed by surface plasmon resonance band illustrated in UV-vis spectrophotometry. AgNP were characterized by FTIR, SEM, EDX, and XRD analyses. AgNP were mostly spherical in shape, crystalline in nature, with face-centered cubic geometry, and mean size was 43-79 nm. Toxicity of AgNP was assessed against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. In laboratory, AgNP were highly toxic against larvae and pupae of the three mosquito species. Maximum efficacy was observed against A. stephensi larvae, with LC50 ranging from 16.156 ppm (larva I) to 28.881 ppm (pupa). In the field, a single treatment with AgNP (10 × LC50) in water storage reservoirs was effective against the three mosquito vectors, allowing complete elimination of larval populations after 72 h. In ovicidal experiments, egg hatchability was reduced by 100% after treatment with 30 ppm of AgNP. Ovideterrence assays highlighted that 10 ppm of AgNP reduced oviposition rates of more than 70% in A. aegypti, A. stephensi, and C. quinquefasciatus (OAI = -0.61, -0.63, and -0.58, respectively). Antibacterial properties of AgNP were evaluated against Bacillus subtilis, Klebsiella pneumoniae, and Salmonella typhi using the agar disk diffusion and minimum inhibitory concentration protocol. AgNP tested at 50 ppm evoked growth inhibition zones larger than 5 mm in all tested bacteria. Overall, the chance to use S. muticum-synthesized AgNP for control of mosquito vectors seems promising since they are effective at low doses and may constitute an advantageous alternative to build newer and safer mosquito control tools. This is the first

  17. Nonlinear control design for stressed power systems using normal forms of vector fields

    NASA Astrophysics Data System (ADS)

    Jang, Gilsoo

    Large stressed interconnected power systems exhibit complicated dynamic behavior when subjected to disturbances. This nonlinear complex behavior is not well analyzed with present tools, and a complete theoretical analysis of this is not feasible in large systems. In stressed power systems, due to the presence of increased nonlinearity and the existence of nonlinear modal interactions, there exist some limitation to the use of conventional linear control design techniques. Therefore there is a need to understand the nature of nonlinear modal interactions and their influences on control performance for optimal controller setting. This work deals with control design in power systems using the method of normal forms. The objective of this work is to understand the effect of the nonlinear modal interaction on control performance and to develop a procedure to design controls incorporating the nonlinear information. For power systems equipped with fast exciters, the exciter gains have crucial influence on the system dynamic behavior. In order to be able to tune the exciter gains for optimal system performance, one has to understand, how the system response changes with different gain settings. In linear analysis, this consists of determining the eigenvalues for various gains, and computing the sensitivity of the eigenvalues under gain variations. If one takes into account the influence of the second order normal forms on the system response, then the corresponding interaction coefficients and their sensitivity with respect to gain variations has to be studied as well. This is the topic of the study presented here. The concept of nonlinear participation factors, and sensitivity of the normal forms coefficient, together with linear participation factors and eigenvalue sensitivity are used to vary control settings. The control settings are varied to obtain improved stability and to reduce the nonlinearity in the system. The proposed procedure was applied to the 50-generator

  18. The skin is a significant but overlooked anatomical reservoir for vector-borne African trypanosomes

    PubMed Central

    Capewell, Paul; Cren-Travaillé, Christelle; Marchesi, Francesco; Johnston, Pamela; Clucas, Caroline; Benson, Robert A; Gorman, Taylor-Anne; Calvo-Alvarez, Estefania; Crouzols, Aline; Jouvion, Grégory; Jamonneau, Vincent; Weir, William; Stevenson, M Lynn; O'Neill, Kerry; Cooper, Anneli; Swar, Nono-raymond Kuispond; Bucheton, Bruno; Ngoyi, Dieudonné Mumba; Garside, Paul

    2016-01-01

    The role of mammalian skin in harbouring and transmitting arthropod-borne protozoan parasites has been overlooked for decades as these pathogens have been regarded primarily as blood-dwelling organisms. Intriguingly, infections with low or undetected blood parasites are common, particularly in the case of Human African