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1

Trypanosomiasis vector control in Africa and Latin America  

PubMed Central

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

Schofield, Chris J; Kabayo, John P

2008-01-01

2

Shifting priorities in vector biology to improve control of vector-borne disease  

E-print Network

, dengue, trypanosomiasis, filariasis, leishmaniasis, and Chagas disease. Current control strategies, trypanosomiasis, filariasis, leishmaniasis, and Chagas disease (Gubler 1998). History shows that vector control

3

HUMAN/VECTOR RELATIONSHIPS DURING HUMAN AFRICAN TRYPANOSOMIASIS: INITIAL SCREENING OF IMMUNOGENIC SALIVARY  

E-print Network

HUMAN/VECTOR RELATIONSHIPS DURING HUMAN AFRICAN TRYPANOSOMIASIS: INITIAL SCREENING OF IMMUNOGENIC immunogenic proteins in humans residing in an area endemic for human African trypanosomiasis in the Democratic

Paris-Sud XI, Université de

4

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

PubMed Central

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

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

1963-01-01

5

Trypanosomiasis Control, Democratic Republic of Congo, 1993–2003  

PubMed Central

In the Democratic Republic of Congo (DRC), human African trypanosomiasis (HAT) reached unprecedented levels in the 1990s. To assess recent trends and evaluate control efforts, we analyzed epidemiologic and financial data collected by all agencies involved in HAT control in DRC from 1993 to 2003. Funds allocated to control populations, as well as to the population screened, doubled from 1993 to 1997 and from 1998 to 2003. The number of cases detected decreased from 26,000 new cases per year in 1998 to 11,000 in 2003. Our analysis shows that HAT control in DRC is almost completely dependent on international aid and that sudden withdrawal of such aid in 1990 had a long-lasting effect. Since 1998, control efforts intensified because of renewed donor interest, including a public-private partnership, and this effort led to a major reduction in HAT incidence. To avoid reemergence of this disease, such efforts should be sustained. PMID:16229766

Lutumba, Pascal; Robays, Jo; Bilenge, Constantin Miaka mia; Mesu, Victor Kande Betu Ku; Molisho, Didier; Declercq, Johan; Van der Veken, Wim; Meheus, Filip; Jannin, Jean

2005-01-01

6

Interactions between tsetse and trypanosomes with implications for the control of trypanosomiasis  

Microsoft Academic Search

Tsetse flies (Diptera: Glossinidae) are vectors of several species of pathogenic trypanosomes in tropical Africa. Human African trypanosomiasis (HAT) is a zoonosis caused by Trypanosoma brucei rhodesiense in East Africa and T. b. gambiense in West and Central Africa. About 100 000 new cases are reported per year, with many more probably remaining undetected. Sixty million people living in 36

Serap Aksoy; Wendy C. Gibson; Michael J. Lehane

2003-01-01

7

Human African trypanosomiasis.  

PubMed

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. PMID:23829907

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

2013-01-01

8

Trypanosomiasis and Tsetse Control with Insecticidal Pour-ons— Fact and Fiction?  

Microsoft Academic Search

Insecticidal pour-ons that are applied directly to cattle have been promoted widely in the last decade as a new means of controlling tsetse flies in Africa. Tsetse attracted to treated cattle get a lethal dose of insecticide and die. Following a large trial in Kenya, Matthew Baylis and Peter Stevenson argue here that the reduction in trypanosomiasis incidence caused by

M. Baylis; P. Stevenson

1998-01-01

9

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

Microsoft Academic Search

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, Cote d'Ivoire, the

Jacques Pepin; Nzambi Khonde; Faustine Maiso; Felix Doua; Shabbar Jaffar; Stephane Ngampo; Bokelo Mpia; Dawson Mbulamberi; Felix Kuzoe

10

[Control of human African trypanosomiasis: back to square one].  

PubMed

The natural history of sleeping sickness is cyclic. The first epidemic outbreak in the 19th century devastated the population and resolved spontaneously for lack of victims. Intensive development during the colonial period and the movement of population that it spawned led to another epidemic in the early 1920s that reached such severe proportions that drastic steps had to be taken. At that time, Jamot was given complete political, administrative, and financial freedom to combat the disease. This program led to the development of the mobile team concept and so-called vertically structured vector control strategy and was so successful that sleeping sickness ceased to be considered as a major public health problem at the beginning of the 1960s. In the ensuing years sleeping sickness was largely neglected. Monitoring the disease required specialized teams that were no longer considered as cost-effective. One by one the measures that had been implemented to control the disease disappeared, thus setting the scene for a new outbreak grew. In 1995, the incidence of sleeping sickness reached the same levels as in the 1920s. The current situation is a classic example of a neglected disease with a paucity of competent specialists, diagnostic tests, effective drugs, and operational facilities. It was not until 2001 that new hope appeared thanks to a combined public- and private-sector initiative allowing restructuring of treatment teams, renovation of facilities, free distribution of drugs, and research to develop new therapeutic agents. Also thanks to the PATTEC initiative, the governments of the African affected nations are showing new in interest in sleeping sickness. However the battle is far from won and much effort will be required. Time is running out and the stakes are high. PMID:11803838

Jannin, J; Louis, F J; Lucas, P; Simarro, P P

2001-01-01

11

African trypanosomiasis.  

PubMed

Trypanosomiasis remains one of the most serious constraints to economic development in sub-Saharan Africa and, as a consequence, related research has been subject to strong social and political as well as scientific influences. The epidemics of sleeping sickness that occurred at the turn of the 20th Century focussed research efforts on what became known as 'the colonial disease'. This focus is thought to have produced 'vertical' health services aimed at this one disease, while neglecting other important health issues. Given the scale of these epidemics, and the fact that the disease is fatal if left untreated, it is unsurprising that sleeping sickness dominated colonial medicine. Indeed, recent evidence indicates that, if anything, the colonial authorities greatly under-estimated the mortality attributable to sleeping sickness. Differences in approach to disease control between Francophone and Anglophone Africa, which in the past have been considered ideological, on examination prove to be logical, reflecting the underlying epidemiological divergence of East and West Africa. These epidemiological differences are ancient in origin, pre-dating the colonial period, and continue to the present day. Recent research has produced control solutions, for the African trypanosomiases of humans and livestock, that are effective, affordable and sustainable by small-holder farmers. Whether these simple solutions are allowed to fulfil their promise and become fully integrated into agricultural practice remains to be seen. After more than 100 years of effort, trypanosomiasis control remains a controversial topic, subject to the tides of fashion and politics. PMID:17227648

Maudlin, I

2006-12-01

12

American trypanosomiasis.  

PubMed

American trypanosomiasis is a parasitic disease caused by the flagellate protozoan Trypanosoma cruzi. Chagas disease is endemic in Latin America, where an estimated 10-14 million people are infected, and an emerging disease in Europe and the USA. Trypanosoma cruzi is transmitted by blood-sucking bugs of the family Reduviidae. Rhodnius prolixus, Panstrongylus megistus, Triatoma infestans, and T. dimidiata are the main vectors in the sylvatic cycle. Non vector-borne transmission includes blood transfusion, congenital and oral transmission, transplantation, and accidental infections. Most cases of acute infection occur in childhood and are usually asymptomatic, although severe myocarditis and meningoencephalitis may occur. Approximately 30% of T. cruzi-infected people will develop the chronic stage of the disease. Chronic chagasic cardiomyopathy is characterized by progressive heart failure, arrhythmias, intraventricular conduction defects, sudden death, and peripheral thromboembolism. Acute exacerbation can occur in individuals with involvement of cellular immunity such as advanced AIDS (acquired immunodeficiency syndrome), and transplant-associated immunosuppression. Neurological involvement may present with encephalitis, meningoencephalitis, or a space-occupying cerebral lesion called chagoma. Chagas disease is a major cause of ischemic stroke in Latin America. Several epidemiological studies have found an association between T. cruzi infection and cardioembolic ischemic stroke. Benznidazole and nifurtimox are the two available trypanocide drugs against T. cruzi. PMID:23829903

Carod-Artal, Francisco Javier

2013-01-01

13

American Trypanosomiasis (Also Known as Chagas Disease) Prevention and Control  

MedlinePLUS

... as Chagas Disease) Parasites Home Share Compartir Prevention & Control In endemic areas of Mexico, Central America, and ... disease is now found but is not endemic, control strategies are focused on preventing transmission from blood ...

14

Evaluation of a novel method for controlling bovine trypanosomiasis   

E-print Network

The problem of controlling tsetse flies in Africa is an old one. The tsetse fly transmits the trypanosome parasites which cause sleeping sickness in humans and disease in cattle. Because cattle are a favoured food source ...

Brownlow, Andrew C.

2007-11-27

15

Modeling the Control of Trypanosomiasis Using Trypanocides or Insecticide-Treated Livestock  

PubMed Central

Background In Uganda, Rhodesian sleeping sickness, caused by Trypanosoma brucei rhodesiense, and animal trypanosomiasis caused by T. vivax and T. congolense, are being controlled by treating cattle with trypanocides and/or insecticides. We used a mathematical model to identify treatment coverages required to break transmission when host populations consisted of various proportions of wild and domestic mammals, and reptiles. Methodology/Principal Findings An Ro model for trypanosomiasis was generalized to allow tsetse to feed off multiple host species. Assuming populations of cattle and humans only, pre-intervention Ro values for T. vivax, T. congolense, and T. brucei were 388, 64 and 3, respectively. Treating cattle with trypanocides reduced R0 for T. brucei to <1 if >65% of cattle were treated, vs 100% coverage necessary for T. vivax and T. congolense. The presence of wild mammalian hosts increased the coverage required and made control of T. vivax and T. congolense impossible. When tsetse fed only on cattle or humans, R0 for T. brucei was <1 if 20% of cattle were treated with insecticide, compared to 55% for T. congolense. If wild mammalian hosts were also present, control of the two species was impossible if proportions of non-human bloodmeals from cattle were <40% or <70%, respectively. R0 was <1 for T. vivax only when insecticide treatment led to reductions in the tsetse population. Under such circumstances R0<1 for T. brucei and T. congolense if cattle make up 30% and 55%, respectively of the non-human tsetse bloodmeals, as long as all cattle are treated with insecticide. Conclusions/Significance In settled areas of Uganda with few wild hosts, control of Rhodesian sleeping sickness is likely to be much more effectively controlled by treating cattle with insecticide than with trypanocides. PMID:22616017

Hargrove, John W.; Ouifki, Rachid; Kajunguri, Damian; Vale, Glyn A.; Torr, Stephen J.

2012-01-01

16

Ecology of a vector-borne zoonosis in a complex ecosystem: trypanosomiasis in Serengeti, Tanzania   

E-print Network

Unravelling the complexities of a disease with multiple wildlife host and multiple tsetse vector species is no easy task. After over a century of field observations, experimental studies, anecdotal evidence and conjecture, ...

Auty, Harriet K.

2009-01-01

17

New therapeutic strategies against trypanosomiasis and leishmaniasis.  

E-print Network

??Leishmaniasis and African Trypanosomiasis are diseases caused by the Kinetoplastida parasites of Leishmania sp. and Trypanosoma sp. respectively. Control and management of these diseases, which… (more)

Ibrahim, Hasan Mohamed Saleh

2009-01-01

18

The history of African trypanosomiasis  

PubMed Central

The prehistory of African trypanosomiasis indicates that the disease may have been an important selective factor in the evolution of hominids. Ancient history and medieval history reveal that African trypanosomiasis affected the lives of people living in sub-Saharan African at all times. Modern history of African trypanosomiasis revolves around the identification of the causative agents and the mode of transmission of the infection, and the development of drugs for treatment and methods for control of the disease. From the recent history of sleeping sickness we can learn that the disease can be controlled but probably not be eradicated. Current history of human African trypanosomiasis has shown that the production of anti-sleeping sickness drugs is not always guaranteed, and therefore, new, better and cheaper drugs are urgently required. PMID:18275594

Steverding, Dietmar

2008-01-01

19

Vector control in leishmaniasis.  

PubMed

Indoor residual spraying is a simple and cost effective method of controlling endophilic vectors and DDT remains the insecticide of choice for the control of leishmaniasis. However resistance to insecticide is likely to become more widespread in the population especially in those areas in which insecticide has been used for years. In this context use of slow release emulsified suspension (SRES) may be the best substitute. In this review spraying frequencies of DDT and new schedule of spray have been discussed. Role of biological control and environment management in the control of leishmaniasis has been emphasized. Allethrin (coil) 0.1 and 1.6 per cent prallethrin (liquid) have been found to be effective repellents against Phlebotomus argentipes, the vector of Indian kalaazar. Insecticide impregnated bednets is another area which requires further research on priority basis for the control of leishmaniasis. Role of satellite remote sensing for early prediction of disease by identifying the sandflygenic conditions cannot be undermined. In future synthetic pheromons can be exploited in the control of leishmaniasis. PMID:16778324

Kishore, K; Kumar, V; Kesari, S; Dinesh, D S; Kumar, A J; Das, P; Bhattacharya, S K

2006-03-01

20

Control vectors for splines  

E-print Network

. Introduction Splines have their roots in the lofting technique used in the shipbuilding and aircraft industries throughout the first half of the 20th century. The first mathematical reference to the notion of splines is accredited to the work of Schoenberg [1... associated with control vectors have been raised to a power of 1, 2, . . . , 10 (coloured from red to blue). Note that this curve cannot be generated using quartic B-splines. (For interpretation of the references to colour in this figure legend, the reader...

Kosinka, Ji?i; Sabin, Malcolm A.; Dodgson, Neil A.

2014-09-03

21

Potential demand for a mixed public-private animal health input: evaluation of a pour-on insecticide for controlling tsetse-transmitted trypanosomiasis in Ethiopia  

Microsoft Academic Search

The new pour-on insecticides that can be used to control tsetse-transmitted trypanosomiasis confer benefits to the owners of the cattle given treatments and other people keeping cattle in areas affected by the control. A study was conducted in southwest Ethiopia to assess farmers' perceptions of the public and private benefits of the pour-on and identify the household-level factors affecting its

Brent M. Swallow; Woudyalew Mulatu; Stephen G. A. Leak

1995-01-01

22

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

PubMed Central

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

Busvine, J. R.; Pal, R.

1969-01-01

23

Vector control after malaria eradication  

PubMed Central

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

Micks, D. W.

1963-01-01

24

Progress in malaria vector control*  

PubMed Central

Malaria control, except in tropical Africa, will probably continue to be based to a large extent on the use of insecticides for many years. However, the development of resistance to insecticides in the vectors has caused serious difficulties and it is necessary to change the strategy of insecticide use to maximize their efficacy. A thorough knowledge of the ecology and behaviour of each vector species is required before the control strategy can be adapted to different epidemiological situations. The behavioural differences between sibling species have been recognized for several years, but study of this problem has recently been simplified by improved means of identification that involve chromosomal banding patterns and electrophoretic analysis. Behavioural differences have also been associated with certain chromosomal rearrangements. New records of insecticide resistance among anophelines continue to appear and the impact of this on antimalaria operations has been seriously felt in Central America (multi-resistance in Anopheles albimanus), Turkey (A. sacharovi), India and several Asian countries (A. culicifacies and A. stephensi), and some other countries. Work continues on the screening and testing of newer insecticides that can be used as alternatives, but DDT, malathion, temephos, fenitrothion, and propoxur continue to be used as the main insecticides in many malaria control projects. The search for simpler and innovative approaches to insecticide application also continues. Biological control of vectors is receiving increased attention, as it could become an important component of integrated vector control strategies, and most progress has been made with the spore-forming bacterium, serotype H-14 of Bacillus thuringiensis. Larvivorous fish such as Gambusia spp. and Poecilia spp. continue to be used in some programmes. Application of environmental management measures, such as source reduction, source elimination, flushing of drainage and irrigation channels, and intermittent irrigation have been re-examined and currently a great deal of interest is being shown in these approaches. There has been limited interest in the genetic control of mosquitos and the phenomenon of refractoriness in some strains of the disease vectors, with the idea of replacing the vector species with the refractory strain. More research is needed before this approach can become a practical tool. It is apparent that in future a more integrated approach will have to be used for vector control within the context of antimalaria programmes. Training of staff, research, and cooperation at all levels will be an essential requirement for this approach. PMID:6976842

Pant, C. P.; Rishikesh, N.; Bang, Y. H.; Smith, A.

1981-01-01

25

Epidemiology of human African trypanosomiasis  

PubMed Central

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, where the animal reservoir plays a key role, the interruption of the disease’s transmission is not deemed feasible. PMID:25125985

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

2014-01-01

26

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

E-print Network

duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were and African trypanosomiasis [3]. All these diseases have severe impacts on many tropical and subtropical

Paris-Sud XI, Université de

27

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

PubMed Central

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

2014-01-01

28

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

PubMed

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

Zofou, Denis; Nyasa, Raymond B; Nsagha, Dickson S; Ntie-Kang, Fidele; Meriki, Henry D; Assob, Jules Clement N; Kuete, Victor

2014-01-01

29

Insecticide resistance and vector control.  

PubMed

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:19785227

Brogdon, William G; McAllister, Janet C

2004-01-01

30

Vector control activities. Fiscal year, 1982  

SciTech Connect

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.

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

1983-06-01

31

Integrated vector management for malaria control  

PubMed Central

Integrated vector management (IVM) is defined as "a rational decision-making process for the optimal use of resources for vector control" and includes five key elements: 1) evidence-based decision-making, 2) integrated approaches 3), collaboration within the health sector and with other sectors, 4) advocacy, social mobilization, and legislation, and 5) capacity-building. In 2004, the WHO adopted IVM globally for the control of all vector-borne diseases. Important recent progress has been made in developing and promoting IVM for national malaria control programmes in Africa at a time when successful malaria control programmes are scaling-up with insecticide-treated nets (ITN) and/or indoor residual spraying (IRS) coverage. While interventions using only ITNs and/or IRS successfully reduce transmission intensity and the burden of malaria in many situations, it is not clear if these interventions alone will achieve those critical low levels that result in malaria elimination. Despite the successful employment of comprehensive integrated malaria control programmes, further strengthening of vector control components through IVM is relevant, especially during the "end-game" where control is successful and further efforts are required to go from low transmission situations to sustained local and country-wide malaria elimination. To meet this need and to ensure sustainability of control efforts, malaria control programmes should strengthen their capacity to use data for decision-making with respect to evaluation of current vector control programmes, employment of additional vector control tools in conjunction with ITN/IRS tactics, case-detection and treatment strategies, and determine how much and what types of vector control and interdisciplinary input are required to achieve malaria elimination. Similarly, on a global scale, there is a need for continued research to identify and evaluate new tools for vector control that can be integrated with existing biomedical strategies within national malaria control programmes. This review provides an overview of how IVM programmes are being implemented, and provides recommendations for further development of IVM to meet the goals of national malaria control programmes in Africa. PMID:19091038

Beier, John C; Keating, Joseph; Githure, John I; Macdonald, Michael B; Impoinvil, Daniel E; Novak, Robert J

2008-01-01

32

Vector control operations in the African context  

PubMed Central

In order to define the scope of vector control as a component of malaria control in the WHO African Region, examples of recent experiences with different vector control methods in this region are reviewed. Residual house spraying applied alone or in combination with mass drug administration has failed to interrupt malaria transmission in savanna areas for several technical and administrative reasons. Nevertheless, there is evidence that residual house spraying has led to an improvement in general health. However, the existence of DDT and dieldrin/HCH and lately malathion resistance in the Sudan in Anopheles gambiae s.l. would militate against the use of residual house spraying as a main tool for long-term malaria control. It should therefore be used only to reduce malaria prevalence to an acceptable level until integrated control methods can be developed and become operational. Experience with larval control, space spraying, and biological control of vectors is also reviewed, and the value of self-help methods of reducing man—vector contact under African conditions is examined. All these methods need to be more thoroughly assessed. Several proposals are made for applied field research. PMID:6397279

Zahar, A. R.

1984-01-01

33

CONTRIBUTIONS OF INVERTEBRATE PATHOLOGY TO VECTOR CONTROL  

Technology Transfer Automated Retrieval System (TEKTRAN)

Control of the invertebrate host is an integral part of any integrated program to prevent the spread of vector borne diseases of man and animals. This includes important mosquito borne arboviruses such as yellow fever, dengue and the various types of encephalitis including West Nile Virus, St. Loui...

34

Electromechanical actuation for thrust vector control applications  

Microsoft Academic Search

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

Mary Ellen Roth

1990-01-01

35

Thrust vector control using electric actuation  

Microsoft Academic Search

Presently, gimbaling of launch vehicle engines for thrust vector control is generally accomplished using a hydraulic system. In the case of the space shuttle solid rocket boosters and main engines, these systems are powered by hydrazine auxiliary power units. Use of electromechanical actuators would provide significant advantages in cost and maintenance. However, present energy source technologies such as batteries are

Robert T. Bechtel; David K. Hall

1995-01-01

36

Impacts of trypanosomiasis on African agriculture  

Microsoft Academic Search

African animal trypanosomiasis constrains agricultural production in areas of Africa that hold the continent's greatest potential for expanded agricultural production. Compared to animals kept in trypanosomiasis free areas, animals kept in areas of moderate risk of trypanosomiasis have lower calving rates, lower milk yields, higher rates of calf mortality, and require more frequent treatment with preventive and curative doses of

Brent M. Swallow

37

Thrust vector control using electric actuation  

NASA Astrophysics Data System (ADS)

Presently, gimbaling of launch vehicle engines for thrust vector control is generally accomplished using a hydraulic system. In the case of the space shuttle solid rocket boosters and main engines, these systems are powered by hydrazine auxiliary power units. Use of electromechanical actuators would provide significant advantages in cost and maintenance. However, present energy source technologies such as batteries are heavy to the point of causing significant weight penalties. Utilizing capacitor technology developed by the Auburn University Space Power Institute in collaboration with the Auburn CCDS, Marshall Space Flight Center (MSFC) and Auburn are developing EMA system components with emphasis on high discharge rate energy sources compatible with space shuttle type thrust vector control requirements. Testing has been done at MSFC as part of EMA system tests with loads up to 66000 newtons for pulse times of several seconds. Results show such an approach to be feasible providing a potential for reduced weight and operations costs for new launch vehicles.

Bechtel, Robert T.; Hall, David K.

1995-01-01

38

African bovine trypanosomiasis: the problem of drug resistance  

Microsoft Academic Search

The three trypanocides used to control tsetse-transmitted trypanosomiasis in domestic animals in Africa have been in use for over 40 years and, not surprisingly, resistance of trypanosomes to these drugs has emerged. Because of the relatively limited market in Africa and the high costs of developing and licensing new drugs, international pharmaceutical companies have shown little interest in the development

Stanny Geerts; Peter H Holmes; Mark C Eisler; Oumar Diall

2001-01-01

39

Management of trypanosomiasis and leishmaniasis  

PubMed Central

Background The current treatments for human African trypanosomiasis (HAT), Chagas disease and leishmaniasis (collectively referred to as the kinetoplastid diseases) are far from ideal but, for some, there has been significant recent progress. For HAT the only advances in treatment over the past two decades have been the introduction of an eflornithine/nifurtimox co-administration and a shorter regime of the old standard melarsoprol. Sources of data PubMed. Areas of Agreement There is a need for new safe, oral drugs for cost-effective treatment of patients and use in control programmes for all the trypanosomatid diseases. Areas of controversy Cutaneous leishmaniasis is not on the agenda and treatments are lagging behind. Growing points There are three compounds in development for the treatment of the CNS stage of HAT: fexinidazole, currently due to entry into phase II clinical studies, a benzoxaborole (SCYX-7158) in phase I trials and a diamidine derivative (CPD-0802), in advanced pre-clinical development. For Chagas disease, two anti-fungal triazoles are now in clinical trial. In addition, clinical studies with benznidazole, a drug previously recommended only for acute stage treatment, are close to completion to determine the effectiveness in the treatment of early chronic and indeterminate Chagas disease. For visceral leishmaniasis new formulations, therapeutic switching, in particular AmBisome, and the potential for combinations of established drugs have significantly improved the opportunities for the treatment in the Indian subcontinent, but not in East Africa. Areas timely for developing research Improved diagnostic tools are needed to support treatment, for test of cure in clinical trials and for monitoring/surveillance of populations in control programmes. PMID:23137768

Barrett, Michael P.; Croft, Simon L.

2012-01-01

40

Controlling Vector Bessel Beams with Metasurfaces  

NASA Astrophysics Data System (ADS)

Unprecedented control of an electromagnetic wave front is demonstrated with reflectionless metasurfaces that can manipulate vector Bessel beams: cylindrical vector beams with a Bessel profile. First, two metasurfaces are developed to convert linearly and circularly polarized Gaussian beams into vector Bessel beams. Each unit cell of the metasurfaces provides polarization and phase control with high efficiency. Next, the reciprocal process is demonstrated: an incident radially polarized Bessel beam is transformed into collimated, linearly and circularly polarized beams. In this configuration, a planar Bessel beam launcher is integrated with a collimating metasurface lens to realize a low-profile lens-antenna. The lens-antenna achieves a high directivity (exceeding 20 dB) with a subwavelength overall thickness. Finally, a metasurface providing isotropic polarization rotation is used to transform a radially polarized Bessel beam into an azimuthally polarized Bessel beam. This work demonstrates that metasurfaces can be used to generate arbitrary combinations of radial and azimuthal polarizations for applications such as focus shaping or generating tractor beams.

Pfeiffer, Carl; Grbic, Anthony

2014-10-01

41

Electromechanical actuation for thrust vector control applications  

NASA Technical Reports Server (NTRS)

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.

Roth, Mary Ellen

1990-01-01

42

Vector ecology and integrated control procedures  

PubMed Central

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

Laird, Marshall

1963-01-01

43

The Biological Control of the Malaria Vector  

PubMed Central

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

Kamareddine, Layla

2012-01-01

44

The effects of trypanosomiasis on rural economy*  

PubMed Central

Trypanosomiasis, both of humans and of livestock, is one of the most important factors restricting economic development in Africa today. The present paper outlines how this disease is limiting agricultural, veterinary and forestry development in the Sudan, Bechuanaland and West Africa. The present tsetse-fly distribution is reviewed. Glossina palpalis and G. morsitans occur in the south Sudan and G. morsitans in the Ngamiland district of Bechuanaland; G. morsitans, G. palpalis and G. tachinoides are the most important species in West Africa. These tsetse flies have altered the cattle distribution in all three regions and, in addition to causing widespread disease, have created local overstocking problems in the tsetse-free grazing areas, and have enforced nomadism on breeding herds and economic loss in slaughter cattle along the trade cattle routes in West Africa. Human trypanosomiasis is not now such an urgent problem and public health measures have led to its control in all three areas. Increased agricultural development, which can be a successful and economic method of reclaiming land from tsetse flies, must be intensified in all three areas. Forest conservation policy comes into conflict with tsetse control measures only in West Africa. Detailed tsetse-fly surveys and research, on which future plans can be firmly based, are now urgently required. ImagesFIG. 6 PMID:14001093

Wilson, S. G.; Morris, K. R. S.; Lewis, I. J.; Krog, E.

1963-01-01

45

Electromechanical actuation for thrust vector control applications  

NASA Technical Reports Server (NTRS)

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 control algorithms. Integrated testing of the controller and actuator will be conducted at a facility yet to be named. The EMA system described above is discussed in detail.

Roth, Mary Ellen

1990-01-01

46

Electromechanical actuation for thrust vector control applications  

NASA Astrophysics Data System (ADS)

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 control algorithms. Integrated testing of the controller and actuator will be conducted at a facility yet to be named. The EMA system described above is discussed in detail.

Roth, Mary Ellen

47

Using Cell Phones for Mosquito Vector Surveillance and Control  

E-print Network

Using Cell Phones for Mosquito Vector Surveillance and Control S. Lozano-Fuentes, S. Ghosh, J. M--Novel, low-cost approaches to improving prevention and control of vector-borne diseases, such as mosquito the use of cell phones for field capture and rapid transfer of mosquito vector surveillance data

Bieman, James M.

48

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

PubMed

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

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

49

Thrust vector control using electric actuation  

SciTech Connect

Presently, gimbaling of launch vehicle engines for thrust vector control is generally accomplished using a hydraulic system. In the case of the space shuttle solid rocket boosters and main engines, these systems are powered by hydrazine auxiliary power units. Use of electromechanical actuators would provide significant advantages in cost and maintenance. However, present energy source technologies such as batteries are heavy to the point of causing significant weight penalties. Utilizing capacitor technology developed by the Auburn University Space Power Institute in collaboration with the Auburn CCDS, Marshall Space Flight Center (MSFC) and Auburn are developing EMA system components with emphasis on high discharge rate energy sources compatible with space shuttle type thrust vector control requirements. Testing has been done at MSFC as part of EMA system tests with loads up to 66000 newtons for pulse times of several seconds. Results show such an approach to be feasible providing a potential for reduced weight and operations costs for new launch vehicles. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}

Bechtel, R.T.; Hall, D.K. [Marshall Space Flight Center, Marshall Space Flight Center, Alabama 35812 (United States)

1995-01-25

50

Modeling Tsetse Fly Host Preference and African Trypanosomiasis in Cameroon.  

E-print Network

?? African Trypanosomiasis causes many problems in both public healthand agricultural production in Africa. Tsetse flies transmit Trypanosomiasis;targets for the fly are vertebrates, including humans.… (more)

Park, Suh Yeong

2011-01-01

51

The organization of vector control in Poland  

PubMed Central

International co-operation for the protection of health against communicable diseases originated in the 19th century. The constant development of international transport and trade increases the hazards of the spread of pests carrying diseases and causing economic losses: this can be avoided only by the collaboration of all countries. New methods are now available to control diseases transmitted by rodents and arthropods, but in view of the complexity of the biological, geophysical and technical factors involved it is desirable to investigate the way in which public health authorities in different countries deal with their problems in this field. This paper describes the development of sanitation measures in Poland, and in particular the administrative organization of vector control. Recommendations are made as to how best this may be achieved by countries newly attacking the problem. PMID:20604167

Brodniewicz, A.

1963-01-01

52

The generalized theory of indirect vector control for AC machines  

Microsoft Academic Search

The instantaneous torque produced by an AC machine is controllable when vector control is applied. However, the published papers on vector control deal with either induction machines or synchronous machines. A generalized vector-control theory is developed, considering a generalized AC machine as a salient-pole synchronous machine having three kinds of torque, i.e., the field torque, the reluctance torque, and the

S. Ogasawara; H. Akagi; A. Nabae

1988-01-01

53

Toxic Side Effects of Drugs Used to Treat Chagas’ Disease (American Trypanosomiasis)  

Microsoft Academic Search

Chagas’ disease (American trypanosomiasis) is an endemic parasitic disease in some areas of Latin America. About 16-18 million persons are infected with the aetiological agent of the disease, Trypanosoma cruzi, and more than 100 million are living at risk of infection. There are different modes of infection: 1) via blood sucking vector insects infected with T. cruzi, accounting for 80-90%

José A Castro; María Montalto deMecca; Laura C Bartel

2006-01-01

54

Thrust Vector Control for Nuclear Thermal Rockets  

NASA Technical Reports Server (NTRS)

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.

Ensworth, Clinton B. F.

2013-01-01

55

Chemical control of the heartwater vectors.  

PubMed

This paper reviews available literature on the efficacy of acaricides against Amblyomma hebraeum and other tick species, and presents information on tests done with registered chemicals in the laboratory. Little published information is available on the efficacy of chemicals specifically against A. hebraeum. A host of formulations are registered for use as acaricides on cattle, sheep, and goats in South Africa and thus, by implication, against this species. Resistance has only been described to arsenic and toxaphene in Southern Africa; the other registered products are generally considered to be effective. In contrast, many efficacy tests of various chemicals in different formulations against other Amblyomma spp. have been described. These publications have mainly emanated from the USA, where bite-wounds of these ticks serve as oviposition sites for screwworm flies. In this paper, Amblyomma maculatum and Amblyomma variegatum are included as potential heartwater vectors. The acaricidal efficacy of a number of compounds, representative of different chemical classes, was tested in South Africa against an arsenic and organochlorine resistant strain of A. hebraeum. The engorged adult female immersion method was used. A disconcerting discovery was that several of these registered products failed to control this tick when used at their recommended concentrations. It is concluded that many chemicals which fail against A. hebraeum on cattle do so because of insufficient persistence. Exposure of this tick to lower levels of existing chemicals, but for longer periods, ought to provide satisfactory control for many years. PMID:3329335

Schröder, J

1987-09-01

56

A Rotor Flux Estimation During Zero and Active Vector Periods Using Current Error Space Vector From a Hysteresis Controller for a Sensorless Vector Control of IM Drive  

Microsoft Academic Search

This paper proposes a sensorless vector control scheme for general-purpose induction motor drives using the current error space phasor-based hysteresis controller. In this paper, a new technique for sensorless operation is developed to estimate rotor voltage and hence rotor flux position using the stator current error during zero-voltage space vectors. It gives a comparable performance with the vector control drive

Chintan Patel; Rijil Ramchand; K. Sivakumar; Anandarup Das; K. Gopakumar

2011-01-01

57

Exploiting the potential of vector control for disease prevention.  

PubMed Central

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

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

2005-01-01

58

Cerebral trypanosomiasis in a renal transplant recipient.  

PubMed

Chagas disease is a lifelong, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi. The main form of disease transmission is vector borne, but vertical transmission, such as by organ transplantation from a chronically infected donor, is also possible. The brain tumor-like form can occur years after infection and has been described in patients with acquired immunodeficiency syndrome, and in a very few cases in transplant recipients. We describe the case of a kidney transplant patient who was human immunodeficiency virus negative and infected with T. cruzi, and developed cerebral trypanosomiasis that was successfully treated with benznidazole at 7 mg/kg/day for 60 days. The risk of Chagas disease transmission should not be underestimated in renal transplant patients, even in non-endemic areas. Chagas disease can present as a tumor-like brain lesion, very difficult to differentiate from other opportunistic infectious or neoplastic processes. Frequent monitoring for T. cruzi infection is essential to promptly implement treatment, which, in our patient, proved to be effective and safe. PMID:25040263

Cicora, F; Escurra, V; Bibolini, J; Petroni, J; González, I; Roberti, J

2014-10-01

59

Substituted 2Phenylimidazopyridines: A New Class of Drug Leads for Human African Trypanosomiasis  

E-print Network

Substituted 2Phenylimidazopyridines: A New Class of Drug Leads for Human African Trypanosomiasis brucei, the causative agent of human African trypanosomiasis, led to the identification of substituted 2 trypanosomiasis. INTRODUCTION Two protozoan agents cause human African trypanosomiasis (HAT): Trypanosoma brucei

Gelb, Michael

60

PMSM vector control performance improvement by using pulse with modulation and anti-windup PI controller  

Microsoft Academic Search

This paper presents the simulation results in Matlab\\/Simulink of three versions of permanent magnet synchronous machine (PMSM) vector control. In order to choose the most suitable pulse width modulation (PWM) strategy for controlling the voltage inverter, in term of electromagnetic torque ripple minimization, three modulation techniques associated with the vector control are investigated i.e. sinusoidal PWM and Space Vector Modulation

Khalid Chikh; Abdallah Saad; Mohamed Khafallah; Driss Yousfi

2011-01-01

61

Addressing malaria vector control challenges in South Sudan: proposed recommendations  

PubMed Central

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. PMID:23394124

2013-01-01

62

American Trypanosomiasis (Also Known as Chagas Disease) Diagnosis  

MedlinePLUS

... visit this page: About CDC.gov . Parasites - American Trypanosomiasis (also known as Chagas Disease) Parasites Home Share ... see the DPDx Web site: Chagas disease (American Trypanosomiasis) Diagnostic Procedures: Blood Specimens Print page Get email ...

63

Vector Control Of An AC Brushless Servomotor Using A Custom-Designed Motion Control Card  

Microsoft Academic Search

In this study, vector control of an AC brushless servomotor is performed using the current controlled, voltage source inverter and hysteresis PWM method. Using vector control, three phase variables are transformed on the synchronously rotating d and q axis, and control can be performed as in the DC motor. In order to generate PWM signals, an error value is calculated

Sibel ZORLU; Ibrahim SENOL; A. F. Bakan

2006-01-01

64

Chemotherapy of human African trypanosomiasis: current and future  

E-print Network

Chemotherapy of human African trypanosomiasis: current and future prospects Alan H. Fairlamb- ment of African trypanosomiasis (sleeping sickness) were developed over 50 years ago. All for the development of safer, effective drugs are discussed. The chemotherapy of human African trypanosomiasis (HAT

Schnaufer, Achim

65

Implementation of a new fuzzy vector control of induction motor.  

PubMed

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. PMID:24629620

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

2014-05-01

66

Adaptive support vector regression for UAV flight control  

Microsoft Academic Search

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

Jongho Shin; H. Jin Kim; Youdan Kim

2011-01-01

67

Robust nonlinear control of vectored thrust aircraft  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

68

Vector Control and Surveillance Operations in the Republic of Singapore  

PubMed Central

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

Yoshikawa, Minako Jen

2013-01-01

69

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...

70

Chattering-Free Support Vector Regression Sliding Mode Control  

Microsoft Academic Search

According to an uncertain discrete system with input saturation, a new chattering free support vector regression sliding mode control (SVR-SMC) law based on Linear Matrix Inequalities (LMIs) is presented. The output of SVR is used for replacing sign function of the reaching law in traditional sliding mode control (SMC). An equivalent matrix is constructed for input saturation condition in the

Linsheng Li; Jianning Li

2008-01-01

71

Dengue in Cape Verde: vector control and vaccination  

E-print Network

In 2009, for the first time in Cape Verde, an outbreak of dengue was reported and over twenty thousand people were infected. Only a few prophylactic measures were taken. The effects of vector control on disease spreading, such as insecticide (larvicide and adulticide) and mechanical control, as well as an hypothetical vaccine, are estimated through simulations with the Cape Verde data.

Rodrigues, Helena Sofia; Torres, Delfim F M

2012-01-01

72

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

PubMed

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. PMID:21382664

Ohaeri, C C; Eluwa, M C

2011-05-11

73

The distribution of the vectors of African pathogenic trypanosomes*  

PubMed Central

The author lists the species, subspecies and races of tsetse fly now recognized in three morphologically distinct groups. The distribution of each group is mapped and described in relation to climate and vegetation, with some indication of the part played by past climates and orogenies in determining the modern pattern. The importance of different species as vectors of human or bovine trypanosomiasis, or both, is noted, and examples are given of the part played by human settlement as a secondary limiting factor. The author suggests that many modern problems of control are the consequences of the recent invasion of the African ecosystem by the outside world. Although there are local exceptions, the broad pattern of Glossina distribution has not been significantly changed by the entomological approach to the trypanosomiasis problem. PMID:13958704

Ford, J.

1963-01-01

74

A Quasioptical Vector Interferometer for Polarization Control  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

75

Population mobility and trypanosomiasis in Africa*  

PubMed Central

Population mobility has long been established as a feature of life in Africa south of the Sahara. Even though it appears to be a factor in the spread of sleeping-sickness there do not seem to have been serious epidemics until the latter part of the nineteenth century and the early decades of the twentieth century. Various types of population movement of the present day and their possible relevance to trypanosomiasis are discussed. Density of population and settlement patterns are also important. Some of the changes in these which are relevant to trypanosomiasis are outlined and the need for more detailed information on these and on population mobility is emphasized. PMID:13986384

Prothero, R. Mansell

1963-01-01

76

The future of microbial insecticides as vector control agents.  

PubMed

Insect vectors of human diseases are subject to diseases of their own caused by viruses, bacteria, fungi, protozoans, and nematodes. Over the past 30 years, many members of these groups have been evaluated as vector control agents, particularly for mosquito control. Most pathogens and nematodes occur primarily in larvae, and are only effective against this stage. The principal candidate control agents studied include iridescent and nuclear polyhedrosis viruses, the bacteria Bacillus thuringiensis and Bacillus sphaericus, the fungi Lagenidium giganteum, Culicinomyces clavosporus, and species of the genus Coelomomyces, the protozoan Nosema algerae, and the mermithid nematode Romanomermis culicivorax. Of these, the only one considered an operational success is the bacterium, Bacillus thuringiensis subsp. israelensis (B.t.i.), which has proven useful for control of both mosquito and blackfly larvae in programs where larviciding has been traditionally employed as a vector control tactic. The reasons for the success of B.t.i. are its cost-effectiveness and relative ease of use, which are due, respectively, to the ability of B.t.i. to be grown on artificial media and the development of formulations that can be applied using conventional insecticide application technology. Because few microbial insecticides are cost-effective, and those that are are only effective against larvae, these agents will likely play only a minor, but in some cases important, role in most future vector control programs. PMID:7595459

Federici, B A

1995-06-01

77

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 ...

78

Parameter estimation of vector controlled induction machine  

E-print Network

constant of a machine has more deviant nature than the stator time constant. The former is also an Achilles' heal in maintaining a field oriented control because of the slip frequency calculation. Leakage inductance incase of a 4 pole machine may vary...

Rahman, Tahmid Ur

2002-01-01

79

Vector-borne disease problems in rapid urbanization: new approaches to vector control.  

PubMed Central

Owing to population growth, poor levels of hygiene, and increasing urban poverty, the urban environment in many developing countries is rapidly deteriorating. Densely packed housing in shanty towns or slums and inadequate drinking-water supplies, garbage collection services, and surface-water drainage systems combine to create favourable habitats for the proliferation of vectors and reservoirs of communicable diseases. As a consequence, vector-borne diseases such as malaria, lymphatic filariasis and dengue are becoming major public health problems associated with rapid urbanization in many tropical countries. The problems in controlling these diseases and eliminating vectors and pests can be resolved by decision-makers and urban planners by moving away from the concept of "blanket" applications of pesticides towards integrated approaches. Sound environmental management practices and community education and participation form the mainstay of some of the most outstanding successes in this area. On the basis of these examples, it is argued that the municipal authorities need to apply a flexible methodology, which must be based on the possibilities of mobilizing community resources, with minimal reliance on routine pesticidal spraying. In this way, vector control becomes a by-product of human development in the city environment. This is now a true challenge. PMID:1568273

Knudsen, A. B.; Slooff, R.

1992-01-01

80

Application of Lanczos vectors to control design of flexible structures  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

81

Genetics and evolution of triatomines: from phylogeny to vector control  

PubMed Central

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

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

2012-01-01

82

Model predictive flight control using adaptive support vector regression  

Microsoft Academic Search

This paper explores an application of support vector regression (SVR) to model predictive control (MPC). SVR is employed to identify a dynamic system from input–output data, and the identified model is used for predicting the future states in the MPC framework. In order to deal with constant and dynamic uncertainties, an online adaptation algorithm is designed using the gradient descent

Jongho Shin; H. Jin Kim; Youdan Kim

2010-01-01

83

Vector disparity sensor with vergence control for active vision systems.  

PubMed

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. PMID:22438737

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

2012-01-01

84

Attitude control of a spinning rocket via thrust vectoring  

SciTech Connect

Two controllers are developed to provide attitude control of a spinning rocket that has a thrust vectoring capability. The first controller has a single-input/single-output design that ignores the gyroscopic coupling between the control channels. The second controller has a multi-input/multi-output structure that is specifically intended to account for the gyroscopic coupling effects. A performance comparison between the two approached is conducted for a range of roll rates. Each controller is tested for the ability to track step commands, and for the amount of coupling impurity. Both controllers are developed via a linear-quadratic-regulator synthesis procedure, which is motivated by the multi-input/multi-output nature of second controller. Time responses and a singular value analysis are used to evaluate controller performance. This paper describes the development and comparison of two controllers that are designed to provide attitude control of a spinning rocket that is equipped with thrust vector control. 12 refs., 13 figs., 2 tabs.

White, J.E.

1990-12-19

85

Design of high power electromechanical actuator for thrust vector control  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

86

Velocity vector control system augmented with direct lift control  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

87

Experimental therapy of African trypanosomiasis with a nanobody-conjugated human trypanolytic factor  

E-print Network

Experimental therapy of African trypanosomiasis with a nanobody-conjugated human trypanolytic prevalence of drug resistance hampers efficient treatment of human African trypanosomiasis (HAT). Hence manmade type of immunotoxin with potential for trypanosomiasis therapy. Treatment with this engineered

Arnold, Jonathan

88

Edinburgh Research Explorer A longitudinal survey of African animal trypanosomiasis in  

E-print Network

Edinburgh Research Explorer A longitudinal survey of African animal trypanosomiasis in domestic trypanosomiasis in domestic cattle on the Jos Plateau, Nigeria: prevalence, distribution and risk factors. 2014 #12;RESEARCH Open Access A longitudinal survey of African animal trypanosomiasis in domestic

Millar, Andrew J.

89

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

90

Vectors  

NSDL National Science Digital Library

This lesson was created by Larry Friesen and Anne Gillis for Butler Community College. It will help physics and calculus students differentiate between the uses of vectors in mathematics vs. physics. This website provides two PDF documents that give detailed lessons about vectors, including an overview of terminology, sample problems, and an HTML worksheet is also provided. For educators or students, this site offers well laid-out lessons and/or practice with vectors.

Friesen, Larry; Gillis, Anne

2008-04-18

91

vectors  

NSDL National Science Digital Library

The word vector comes from the Latin term vehere, to carry. In Biology, a vector is an agent which carries disease, such as a mosquito carrying infected blood from one patient to the next. In physics, a vector is a quantity which has both a magnitude and a direction associated with it. The most commonly used example of vectors in everyday life is velocity. When you drive your car, your speedometer tells you the speed of your car, but it doesn't tell you where you are going. The combination of both where you are going and how fast you are going there is your car's velocity.

David Joiner

92

Veterinary Parasitology 115 (2003) 125145 Control of tsetse flies and trypanosomes  

E-print Network

Elsevier B.V. All rights reserved. Keywords: African trypanosomiasis; Tsetse flies; Symbiosis; Commensal, trypanosomiasis, and leishmaniasis has re-emerged as an important priority for biomedical and public health Tel trypanosomiasis. Tsetse flies (Diptera: Glossinidae) are the sole vectors of several species of pathogenic

Aksoy, Serap

93

Adaptive support vector regression for UAV flight control.  

PubMed

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. PMID:20970303

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

2011-01-01

94

Fault tolerant vector control of induction motor drive  

NASA Astrophysics Data System (ADS)

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.

Odnokopylov, G.; Bragin, A.

2014-10-01

95

Design and test of electromechanical actuators for thrust vector control  

NASA Technical Reports Server (NTRS)

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.

Cowan, J. R.; Weir, Rae Ann

1993-01-01

96

A Research Agenda for Malaria Eradication: Vector Control  

PubMed Central

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

2011-01-01

97

Vectors  

NSDL National Science Digital Library

This web page introduces vectors as an extension of numbers having both magnitude and direction. The initial motivation is to describe velocity but the material includes a general discussion of vector algebra and an application to forces for the inclined plane. The page contains links to a related lesson plan and further opportunities to explore vectors. This is part of the extensive web site "From Stargazers to Starships", that uses space exploration and space science to introduce topics in physics and astronomy. Translations in Spanish and French are available.

Stern, David

2006-07-16

98

[Control Program of Chagas disease in São Paulo, Brazil: the control and surveillance of vector transmission].  

PubMed

The control of the vectors of Chagas' disease in the State of Sao Paulo are discussed, mainly those activities that led to the elimination of Triatoma infestans. Secondary factors that helped the control such as rural exodus are also analyzed. The article shows that since 1965 the control became a campaign with different phases due to the epidemiological situation, the acquired knowledge and the entomological surveillance. After 25 years of work, the elimination of all the focus of Triatoma infestans was finally reached and the campaign was ended. However, due to the possibility of reintroduction of the vector in rural areas by passive transportation besides the presence of secondary vectors (Triatoma sordida and Panstrongylus megistus) in several localities, the vector control activities were not interrupted and the surveillance is continuous. PMID:21584361

Silva, Eduardo Olavo da Rocha e; Rodrigues, Vera Lúcia Cortiço Corrêa; Silva, Rubens Antonio da; Wanderley, Dalva Marli Valério

2011-01-01

99

Harnessing mosquito-Wolbachia symbiosis for vector and disease control.  

PubMed

Mosquito species, members of the genera Aedes, Anopheles and Culex, are the major vectors of human pathogens including protozoa (Plasmodium sp.), filariae and of a variety of viruses (causing dengue, chikungunya, yellow fever, West Nile). There is lack of efficient methods and tools to treat many of the diseases caused by these major human pathogens, since no efficient vaccines or drugs are available; even in malaria where insecticide use and drug therapies have reduced incidence, 219 million cases still occurred in 2010. Therefore efforts are currently focused on the control of vector populations. Insecticides alone are insufficient to control mosquito populations since reduced susceptibility and even resistance is being observed more and more frequently. There is also increased concern about the toxic effects of insecticides on non-target (even beneficial) insect populations, on humans and the environment. During recent years, the role of symbionts in the biology, ecology and evolution of insect species has been well-documented and has led to suggestions that they could potentially be used as tools to control pests and therefore diseases. Wolbachia is perhaps the most renowned insect symbiont, mainly due to its ability to manipulate insect reproduction and to interfere with major human pathogens thus providing new avenues for pest control. We herein present recent achievements in the field of mosquito-Wolbachia symbiosis with an emphasis on Aedes albopictus. We also discuss how Wolbachia symbiosis can be harnessed for vector control as well as the potential to combine the sterile insect technique and Wolbachia-based approaches for the enhancement of population suppression programs. PMID:24252486

Bourtzis, Kostas; Dobson, Stephen L; Xi, Zhiyong; Rasgon, Jason L; Calvitti, Maurizio; Moreira, Luciano A; Bossin, Hervé C; Moretti, Riccardo; Baton, Luke Anthony; Hughes, Grant L; Mavingui, Patrick; Gilles, Jeremie R L

2014-04-01

100

Underpinning Sustainable Vector Control through Informed Insecticide Resistance Management  

PubMed Central

Background There has been rapid scale-up of malaria vector control in the last ten years. Both of the primary control strategies, long-lasting pyrethroid treated nets and indoor residual spraying, rely on the use of a limited number of insecticides. Insecticide resistance, as measured by bioassay, has rapidly increased in prevalence and has come to the forefront as an issue that needs to be addressed to maintain the sustainability of malaria control and the drive to elimination. Zambia's programme reported high levels of resistance to the insecticides it used in 2010, and, as a result, increased its investment in resistance monitoring to support informed resistance management decisions. Methodology/Principal Findings A country-wide survey on insecticide resistance in Zambian malaria vectors was performed using WHO bioassays to detect resistant phenotypes. Molecular techniques were used to detect target-site mutations and microarray to detect metabolic resistance mechanisms. Anopheles gambiae s.s. was resistant to pyrethroids, DDT and carbamates, with potential organophosphate resistance in one population. The resistant phenotypes were conferred by both target-site and metabolic mechanisms. Anopheles funestus s.s. was largely resistant to pyrethroids and carbamates, with potential resistance to DDT in two locations. The resistant phenotypes were conferred by elevated levels of cytochrome p450s. Conclusions/Significance Currently, the Zambia National Malaria Control Centre is using these results to inform their vector control strategy. The methods employed here can serve as a template to all malaria-endemic countries striving to create a sustainable insecticide resistance management plan. PMID:24932861

Hemmings, Kay; Hughes, Angela J.; Chanda, Emmanuel; Musapa, Mulenga; Kamuliwo, Mulakwa; Phiri, Faustina N.; Muzia, Lucy; Chanda, Javan; Kandyata, Alister; Chirwa, Brian; Poer, Kathleen; Hemingway, Janet; Wondji, Charles S.; Ranson, Hilary; Coleman, Michael

2014-01-01

101

ParatransgenesisAppliedfor Control of TsetseTransmittedSleepingSickness  

E-print Network

Weiss and GeoffreyAttardo Abstract A frican trypanosomiasis (sleeping sickness) is a major cause of morbidity functions and lead to the control of trypanosomiasis by blocking trypanosome transmission in the tsetse

Aksoy, Serap

102

Cluster of African trypanosomiasis in travelers to Tanzanian national parks  

Microsoft Academic Search

Game parks in Tanzania have long been considered to be at low risk for African trypanosomiasis; however, nine cases of the disease associated with these parks were recently reported. The outbreak was detected through TropNetEurop, a sentinel surveillance network of clinical sites throughout Europe. frican trypanosomiasis (sleeping sickness), a serious infection caused by a protozoan (Trypanosoma brucei), is usually spread

Tomas Jelinek; Zeno Bisoffi; Lucio Bonazzi; Thiel van P. P. A. M; Ulf Bronner; Albie de Frey; Svein Gunnar Gundersen; Paul McWhinney; Diego Ripamonti

2002-01-01

103

Genetically Distinct Glossina fuscipes fuscipes Populations in the Lake Kyoga Region of Uganda and Its Relevance for Human African Trypanosomiasis  

PubMed Central

Tsetse flies (Glossina spp.) are the sole vectors of Trypanosoma brucei—the agent of human (HAT) and animal (AAT) trypanosomiasis. Glossina fuscipes fuscipes (Gff) is the main vector species in Uganda—the only country where the two forms of HAT disease (rhodesiense and gambiense) occur, with gambiense limited to the northwest. Gff populations cluster in three genetically distinct groups in northern, southern, and western Uganda, respectively, with a contact zone present in central Uganda. Understanding the dynamics of this contact zone is epidemiologically important as the merger of the two diseases is a major health concern. We used mitochondrial and microsatellite DNA data from Gff samples in the contact zone to understand its spatial extent and temporal stability. We show that this zone is relatively narrow, extending through central Uganda along major rivers with south to north introgression but displaying no sex-biased dispersal. Lack of obvious vicariant barriers suggests that either environmental conditions or reciprocal competitive exclusion could explain the patterns of genetic differentiation observed. Lack of admixture between northern and southern populations may prevent the sympatry of the two forms of HAT disease, although continued control efforts are needed to prevent the recolonization of tsetse-free regions by neighboring populations. PMID:24199195

Echodu, Richard; Sistrom, Mark; Hyseni, Chaz; Enyaru, John; Okedi, Loyce; Aksoy, Serap; Caccone, Adalgisa

2013-01-01

104

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

PubMed Central

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 key funders. These analyses would be of use, as HAT is currently being prioritized as a neglected tropical disease (NTD) to reach elimination by 2020. PMID:25654605

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

2015-01-01

105

Tsetse and trypanosomiasis survey of Southern Darfur province, Sudan. II. Entomological aspects.  

PubMed

Atsetse survey of Southern Darfur province, Sudan showed that the distribution of the only species present, Glossina morsitans submorsitans, had not appreciably altered over 10 years. Fly populations are most dense south of the Wadi Umbelasha but light infestations are found in the woodlands north of this riverine system to a latitude of about 10 degrees 15' N. Data are given on host availability which is thought to be the major factor determining tsetse distribution. The relative importance of tsetse and of tabanids as transmitters of bovine trypanosomiasis in the province is discussed. The evidence indicates that tsetse are very much more important and that cattle are most at risk of contracting infections during their dry season southerly migrations to the tsetse belts especially during their "Rushash" migration at first rains. Possibilities of tsetse control are discussed but in the short term trypanosomiasis control is most likely best achieved by chemical prophylaxis/therapy of cattle at risk. PMID:6485102

Hall, M J; Kheir, S M; Rahman, A H; Noga, S

1984-08-01

106

Mixture for Controlling Insecticide-Resistant Malaria Vectors  

PubMed Central

The spread of resistance to pyrethroids in the major Afrotropical malaria vectors Anopheles gambiae s.s. necessitates the development of new strategies to control resistant mosquito populations. To test the efficacy of nets treated with repellent and insecticide against susceptible and insecticide-resistant An. gambiae mosquito populations, we impregnated mosquito bed nets with an insect repellent mixed with a low dose of organophosphorous insecticide and tested them in a rice-growing area near Bobo-Dioulasso, Burkina Faso. During the first 2 weeks posttreatment, the mixture was as effective as deltamethrin alone and was more effective at killing An. gambiae that carried knockdown resistance (kdr) or insensitive acetylcholinesterase resistance (Ace1R) genes. The mixture seemed to not kill more susceptible genotypes for the kdr or Ace1R alleles. Mixing repellents and organophosphates on bed nets could be used to control insecticide-resistant malaria vectors if residual activity of the mixture is extended and safety is verified. PMID:18976553

Costantini, Carlo; Corbel, Vincent; Licciardi, Séverine; Dabiré, Roch K.; Lapied, Bruno; Chandre, Fabrice; Hougard, Jean-Marc

2008-01-01

107

Challenges and future perspective for dengue vector control in the Western Pacific Region  

PubMed Central

Dengue remains a significant public health issue in the Western Pacific Region. In the absence of a vaccine, vector control is the mainstay for dengue prevention and control. In this paper we describe vector surveillance and vector control in the Western Pacific countries and areas. Vector surveillance and control strategies used by countries and areas of the Western Pacific Region vary. Vector control strategies include chemical, biological and environmental management that mainly target larval breeding sites. The use of insecticides targeting larvae and adult mosquitoes remains the mainstay of vector control programmes. Existing vector control tools have several limitations in terms of cost, delivery and long-term sustainability. However, there are several new innovative tools in the pipeline. These include Release of Insects Carrying a Dominant Lethal system and Wolbachia, an endosymbiotic bacterium, to inhibit dengue virus in the vector. In addition, the use of biological control such as larvivorous fish in combination with community participation has potential to be scaled up. Any vector control strategy should be selected based on evidence and appropriateness for the entomological and epidemiological setting and carried out in both inter-epidemic and epidemic periods. Community participation and interagency collaboration are required for effective and sustainable dengue prevention and control. Countries and areas are now moving towards integrated vector management. PMID:23908883

Christophel, Eva Maria; Gopinath, Deyer; Abdur, Rashid Md.; Vectorborne, Other; Diseases, Parasitic

2011-01-01

108

Genetic control of resistance to trypanosomiasis  

Microsoft Academic Search

To map the genetic sources of trypanotolerance in mice, a linkage analysis of survival following trypanosome challenge was performed by selective genotyping in a large F2 population produced by crossing the resistant C57BL6 and susceptible BALBc inbred mouse lines. We report evidence of a chromosomal region of large effect, possibly comprising more than one resistance locus, on Chromosome 17; and

S. J. Kemp; A. Darvasi; M. Soller; A. J. Teale

1996-01-01

109

Human African Trypanosomiasis Diagnosis in First-Line Health Services of Endemic Countries, a Systematic Review  

PubMed Central

While the incidence of Human African Trypanosomiasis (HAT) is decreasing, the control approach is shifting from active population screening by mobile teams to passive case detection in primary care centers. We conducted a systematic review of the literature between 1970 and 2011 to assess which diagnostic tools are most suitable for use in first-line health facilities in endemic countries. Our search retrieved 16 different screening and confirmation tests for HAT. The thermostable format of the Card Agglutination Test for Trypanosomiasis (CATT test) was the most appropriate screening test. Lateral flow antibody detection tests could become alternative screening tests in the near future. Confirmation of HAT diagnosis still depends on visualizing the parasite in direct microscopy. All other currently available confirmation tests are either technically too demanding and/or lack sensitivity and thus rather inappropriate for use at health center level. Novel applications of molecular tests may have potential for use at district hospital level. PMID:23209860

Mitashi, Patrick; Hasker, Epco; Lejon, Veerle; Kande, Victor; Muyembe, Jean-Jacques; Lutumba, Pascal; Boelaert, Marleen

2012-01-01

110

African trypanosome control in the insect vector and mammalian host.  

PubMed

The life cycle of African trypanosomes involves adaptations to the defense mechanisms of two completely different hosts, the insect vector Glossina and the mammalian host. This interplay ultimately determines host resistance and/or tolerance to parasite infection. In the tsetse fly, the immune deficiency (IMD)-regulated pathway, the scavenger receptor peptidoglycan-recognition protein LB (PGRP-LB), and the reactive oxygen species (ROS)-mediated response modulate the insect's capacity to transmit the parasite. In experimental mice, control of parasite burden and tissue pathogenicity relies on timely regulated interactions between myeloid cells exhibiting distinct activation states (M1 versus M2 type). Tsetse fly saliva and various trypanosome components including adenylate cyclases, DNA, a kinesin heavy chain, and variant surface glycoprotein (VSG) interfere with resistance and tolerance to infection. PMID:25246021

Beschin, Alain; Van Den Abbeele, Jan; De Baetselier, Patrick; Pays, Etienne

2014-11-01

111

Model Predictive Control of an SP100 Space Reactor Using Support Vector Regression and Genetic Optimization  

Microsoft Academic Search

In this work, a model predictive control method combined with support vector regression and genetic optimization is applied to the design of the thermoelectric (TE) power control in the SP-100 space reactor. The future TE power is predicted by using the support vector regression. The objectives of the proposed model predictive controller are to minimize both the difference between the

Man Gyun Na; B. R. Upadhyaya

2006-01-01

112

Status and prospects of plant virus control through interference with vector transmission.  

PubMed

Most plant viruses rely on vector organisms for their plant-to-plant spread. Although there are many different natural vectors, few plant virus-vector systems have been well studied. This review describes our current understanding of virus transmission by aphids, thrips, whiteflies, leafhoppers, planthoppers, treehoppers, mites, nematodes, and zoosporic endoparasites. Strategies for control of vectors by host resistance, chemicals, and integrated pest management are reviewed. Many gaps in the knowledge of the transmission mechanisms and a lack of available host resistance to vectors are evident. Advances in genome sequencing and molecular technologies will help to address these problems and will allow innovative control methods through interference with vector transmission. Improved knowledge of factors affecting pest and disease spread in different ecosystems for predictive modeling is also needed. Innovative control measures are urgently required because of the increased risks from vector-borne infections that arise from environmental change. PMID:23663003

Bragard, C; Caciagli, P; Lemaire, O; Lopez-Moya, J J; MacFarlane, S; Peters, D; Susi, P; Torrance, L

2013-01-01

113

African Trypanosomiasis Detection using Dempster-Shafer Theory  

E-print Network

World Health Organization reports that African Trypanosomiasis affects mostly poor populations living in remote rural areas of Africa that can be fatal if properly not treated. This paper presents Dempster-Shafer Theory for the detection of African trypanosomiasis. Sustainable elimination of African trypanosomiasis as a public-health problem is feasible and requires continuous efforts and innovative approaches. In this research, we implement Dempster-Shafer theory for detecting African trypanosomiasis and displaying the result of detection process. We describe eleven symptoms as major symptoms which include fever, red urine, skin rash, paralysis, headache, bleeding around the bite, joint the paint, swollen lymph nodes, sleep disturbances, meningitis and arthritis. Dempster-Shafer theory to quantify the degree of belief, our approach uses Dempster-Shafer theory to combine beliefs under conditions of uncertainty and ignorance, and allows quantitative measurement of the belief and plausibility in our identificat...

Maseleno, Andino

2012-01-01

114

MODEL PREDICTIVE CONTROL OF A THRUST-VECTORED FLIGHT CONTROL EXPERIMENT  

Microsoft Academic Search

Model predictive control (MPC) is applied to the Caltech ducted fan, a thrust-vectored ?ight experiment. A real-time trajectory generation software based on spline theory and sequential quadratic programming is used to implement the MPC controllers. Timing issues related to the computation and implementation of repeatedly updated optimal trajectories are discussed. Results show computational speeds greater than 10 Hz, 2.5 times

William B. Dunbar; Mark B. Milam; Ryan Franz; Richard M. Murray

2002-01-01

115

Using a geographical-information-system-based decision support to enhance malaria vector control in zambia.  

PubMed

Geographic information systems (GISs) with emerging technologies are being harnessed for studying spatial patterns in vector-borne diseases to reduce transmission. To implement effective vector control, increased knowledge on interactions of epidemiological and entomological malaria transmission determinants in the assessment of impact of interventions is critical. This requires availability of relevant spatial and attribute data to support malaria surveillance, monitoring, and evaluation. Monitoring the impact of vector control through a GIS-based decision support (DSS) has revealed spatial relative change in prevalence of infection and vector susceptibility to insecticides and has enabled measurement of spatial heterogeneity of trend or impact. The revealed trends and interrelationships have allowed the identification of areas with reduced parasitaemia and increased insecticide resistance thus demonstrating the impact of resistance on vector control. The GIS-based DSS provides opportunity for rational policy formulation and cost-effective utilization of limited resources for enhanced malaria vector control. PMID:22548086

Chanda, Emmanuel; Mukonka, Victor Munyongwe; Mthembu, David; Kamuliwo, Mulakwa; Coetzer, Sarel; Shinondo, Cecilia Jill

2012-01-01

116

The Burden of Human African Trypanosomiasis  

PubMed Central

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

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

2008-01-01

117

Research on a support-vector-machine-based Variable Speed Limits control model  

Microsoft Academic Search

This paper studied the existing freeway main line variable speed control mechanisms. Since the Variable Speed Limits (VSL) control for freeway main line is a nonlinear system, it is difficult to predict its behavior using quantitative model. Based on the research for Support Vector Machine (SVM), the paper proposed a novel model which used support vector to build segmental variable

Wei Wang; Wei Xu; Zhao-sheng Yang; Ding-xuan Zhao

2011-01-01

118

Study and simulation of space vector PWM control of double-star induction motors  

Microsoft Academic Search

This paper deals with a comparison between different structures of double-star induction motors (DSIMs), controlled by space vector PWM. The modelling of the DSIM is made using an arbitrary shift angle between the two three-phase windings. A new transformation matrix is proposed to develop a suitable dynamic model and to elaborate the space vector PWM control strategy for different values

D. Hadiouche; H. Razik; A. Rezzoug

2000-01-01

119

Animal indicators for side-effects of chemical vector control.  

PubMed

In many places in the tropics pesticides are applied in the natural environment to control insects either for crop protection, or for human health. The present study concerns the side-effects of insecticides that are applied in West Africa against tsetseflies (Glossina spp), which are the vectors of human and animal sleeping sickness. Pyrethroids and endosulfan were sprayed either by helicopter or by ground spraying on riverine forests and on forests around villages.Because of the complexity of the terrestrial and aquatic ecosystems under study, a selection was made of populations in which side-effects were assessed (so-called indicators). Fish and benthic arthropods were studied in the rivers; Diptera, Hymenoptera and spiders in the forest. Observations on short-term effects revealed the most vulnerable populations (indicators for effects) depending on the insecticide and the method of application. Long-term studies, up to two years, revealed the differences amongst these populations in ability to recover from local depletion. The populations which recovered most slowly were regarded as indicators for recovery.Differences in hydrological regime between climatic zones are regarded to be highly related to differences in vulnerability of ecosystems to irreversible damage by pesticides. PMID:24259087

Everts, J W

1983-09-01

120

A simple design method based on vector control of AC machines with LC filter  

Microsoft Academic Search

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.

Ryosuke SAITO; Hisao KUBOTA

2007-01-01

121

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

Microsoft Academic Search

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.

Ryosuke Saito; Hisao Kubota

2009-01-01

122

Direct torque control scheme of IM drive with 12-sided polygonal voltage space vectors  

Microsoft Academic Search

The application like electric vehicles requires frequent torque control to control speed of IM Drives. The direct torque control is very good control scheme for fast torque control and it is easy to implement and decoupling of motor variables along rotor flux axis is not required. In this paper, direct torque control scheme is proposed using 12-sided polygonal space vector

Chintan Patel; Rijil Ramchand; P. P. Rajeevan; K. Sivakumar; Anandarup Das; K. Gopakumar; Marian P. Kazmierkowski

2011-01-01

123

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

PubMed

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

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

2014-01-01

124

Investigation into the ecology of trypanosomiasis in the Lungawa Valley, Zambia   

E-print Network

keeping is almost non-existent due to losses from trypanosomiasis and predation by wild animals. The aim of this study was to investigate the ecology of trypanosomiasis in this mult-host wildlife community, relatively free from anthropogenic influences...

Anderson, Neil Euan

2009-01-01

125

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

NASA Astrophysics Data System (ADS)

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 ?1 control theory in conjunction with the Popov-Tsypkin multiplier. The resulting optimization problem was solved using a real coded genetic-algorithm.

Dores, Delfim Zambujo Das

2005-11-01

126

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

PubMed Central

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 included how the Ecuadorian MCP relies heavily on the community for vector control while the American MCP relies on technologies and research. Conclusion IVM based recommendations direct health policy leaders toward improving surveillance systems both entomologically and epidemiologically, improving community risk perceptions by integrating components of community participation, maximizing resources though the use of applied research, and protecting the environment by selecting low-risk pesticides. Outcomes of the research revealed that inter-sectorial and multidisciplinary interventions are critical to improve public health. PMID:24990155

2014-01-01

127

FocusSpecific Clinical Profiles in Human African Trypanosomiasis Caused by Trypanosoma brucei  

E-print Network

Focus­Specific Clinical Profiles in Human African Trypanosomiasis Caused by Trypanosoma brucei in human African trypanosomiasis (HAT) foci caused by Trypanosoma brucei rhodesiense (T Profiles in Human African Trypanosomiasis Caused by Trypanosoma brucei rhodesiense. PLoS Negl Trop Dis 4

Schnaufer, Achim

128

Chemical Validation of Trypanothione Synthetase A POTENTIAL DRUG TARGET FOR HUMAN TRYPANOSOMIASIS*S  

E-print Network

Chemical Validation of Trypanothione Synthetase A POTENTIAL DRUG TARGET FOR HUMAN TRYPANOSOMIASIS for the treatment of human African trypanosomiasis, many potential drug targets in Trypa- nosoma brucei have been validation of TryS as a drug target in T. brucei. Human African trypanosomiasis (HAT)2 is endemic in sub

Schnaufer, Achim

129

Multichannel vector field control module for LLRF control of superconducting cavities  

SciTech Connect

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.

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

2007-06-01

130

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

PubMed Central

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. PMID:23271973

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

131

[Human African trypanosomiasis: report of three cases].  

PubMed

Prolonged fever is an important cause of morbidity in pediatric practice, especially in tropical areas. It is above all a problem of etiological diagnosis given the vast number of etiologies. In sub-Saharan Africa, practitioners more often focus on bacterial infections and malaria at the expense of other infectious diseases such as human African trypanosomiasis (HAT), most often leading to overuse of antibiotics and antimalarials. A dramatic resurgence of HAT, also called sleeping sickness, has been reported during the last few decades in large areas of Central Africa. Furthermore, with the development of air transport, cases of children infected during a trip to Africa can be exported outside endemic areas, making diagnosis even more difficult. This parasitic infection causes a protracted, often initially unrecognized, illness with episodes of fever, headache, and malaise, accompanied by progressive lymphadenopathy, before the development of a progressive meningoencephalitis. These three case reports aim to remind practitioners of clinical and biological signs suggestive of HAT diagnosis in children living in endemic areas or having stayed there during the months prior to visiting the doctor. The prognosis is largely dependent on the precocity of diagnosis and therapeutic support. PMID:23827376

Koko, J; Ategbo, S J; Gahouma, D; Engohan-Aloghe, E; Moussavou, A

2013-08-01

132

Determining the spatial autocorrelation of dengue vector populations: influences of mosquito sampling method, covariables, and vector control.  

PubMed

We investigated spatial autocorrelation of female Aedes aegypti L. mosquito abundance from BG-Sentinel trap and sticky ovitrap collections in Cairns, north Queensland, Australia. BG-Sentinel trap collections in 2010 show a significant spatial autocorrelation across the study site and over a smaller spatial extent, while sticky ovitrap collections only indicate a non-significant, weak spatial autocorrelation. The BG-Sentinel trap collections were suitable for spatial interpolation using ordinary kriging and cokriging techniques. The uses of Premise Condition Index and potential breeding container data have helped improve our prediction of vector abundance. Semiovariograms and prediction maps indicate that the spatial autocorrelation of mosquito abundance determined by BG-Sentinel traps extends farther compared to sticky ovitrap collections. Based on our data, fewer BG-Sentinel traps are required to represent vector abundance at a series of houses compared to sticky ovitraps. A lack of spatial structure was observed following vector control treatment in the area. This finding has implications for the design and costs of dengue vector surveillance programs. PMID:24820568

Azil, Aishah H; Bruce, David; Williams, Craig R

2014-06-01

133

Trypanosoma cruzi: adaptation to its vectors and its hosts  

PubMed Central

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

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

2009-01-01

134

Importance of L-tryptophan metabolism in trypanosomiasis.  

PubMed

African trypanosomiasis or sleeping sickness is caused by extracellular trypanosomes. The presence of seric antibodies directed to a tryptophan-like epitope in trypanosome infected patients and animals led us to investigate the roles of tryptophan in trypanosomiasis. These antibodies are directed against a tryptophan-rich conserved sequence inside the major parasite surface glycoprotein. In vitro, a rapid uptake of tryptophan by trypanosomes is measured. Seric tryptophan levels are decreased during trypanosomiasis. This decrease may be linked with an increase in indoleamine 2,3-dioxygenase (IDO) induced by Interferon-gamma. In vivo inhibition of IDO by norharman provokes a dramatic increase in circulating parasite number. All these data show the essential role of tryptophan in parasite growth. Moreover, antibodies against tryptophan, the decreased concentration of the neurotransmitter serotonin in the brain following infection and the tryptophan metabolites (tryptophol) produced by trypanosomes may participate to the pathophysiological mechanisms provoking sleeping sickness. PMID:10721096

Vincendeau, P; Lesthelle, S; Bertazzo, A; Okomo-Assoumou, M C; Allegri, G; Costa, C V

1999-01-01

135

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...

136

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

NASA Technical Reports Server (NTRS)

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.

Bates, Lisa B.; Young, David T.

2012-01-01

137

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

NASA Astrophysics Data System (ADS)

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.

Saito, Ryosuke; Kubota, Hisao

138

Controllable scattering of vector Bose-Einstein solitons  

SciTech Connect

We show the possibility of producing matter-wave switching devices by using Manakov interactions between vector matter-wave solitons using two-species Bose-Einstein condensates (BECs). Our results establish the experimental parameters for three interaction regimes in two-species BECs: symmetric and asymmetric splitting, down-switching, and up-switching. We have studied the dependence upon the initial conditions and the kind of interaction between the two matter-wave solitons.

Babarro, Judit; Paz-Alonso, Maria J.; Michinel, Humberto; Salgueiro, Jose R.; Olivieri, David N. [Area de Optica, Facultade de Ciencias de Ourense, Universidade de Vigo, As Lagoas s/n, Ourense, ES-32004 (Spain); Escola Tecnica Superior de Enxeneria Informatica, Universidade de Vigo, As Lagoas s/n, Ourense, ES-32004 (Spain)

2005-04-01

139

GIS Initiatives in Improving the Dengue Vector Control  

Microsoft Academic Search

The Hong Kong Government has been conducting a dengue fever surveillance program using ovitraps for several years. In the\\u000a current practice, the disease patterns and vector trends are mapped with the use of a Geographical Information System (GIS)\\u000a and analyses are then performed to identity buildings having potential danger of a higher Aedes Albopictus infestation. This\\u000a chapter has two objectives:

Mandy Tang; Cheong-wai Tsoi

140

Support vector machine model based predictive pid control system for cement rotary kiln  

Microsoft Academic Search

The rotary kiln calcination is the most important part of cement production including complicated physical and chemical reaction processes with large inertia, pure hysteresis, nonlinearity and strong coupling characteristics. Considering the need of advanced process control in cement industry, this paper presents the application of support vector machine modeling and generalized predictive control PID control algorithm to the conventional cement

Zheng Li

2010-01-01

141

A Novel PID Controller Based on Immune Networks Model Utilizing Vector Distance  

Microsoft Academic Search

To solve conflicts between track and restrain disturbance, robustness and control performance, the immune genetic algorithms (IGA) PID controller based on information entropy is used. Nevertheless, this method needs complex calculation. Its constants are determined by experience and redundant information will slow the speed of convergence. In this paper, a novel PID controller based on immune networks model utilizing vector

Sheng Meng-gang; Huang Hui-xian

2009-01-01

142

Vector controlled induction machines for stand-alone wind energy applications  

Microsoft Academic Search

This paper describes the system and control structures for vector controlled induction generators used for variable speed, wind energy conversion (WEC) systems. The paper focuses on WEC systems feeding an isolated load or weak grid since for such systems the generated voltage and power flow must be regulated by the WEC system itself and the control structures are not trivial.

R. S. Pena; R. J. Cardenas; G. M. Asher; J. C. Clare

2000-01-01

143

Multiaxis aircraft control power from thrust vectoring at high angles of attack  

NASA Technical Reports Server (NTRS)

Extensive research programs conducted at the Langley Research Center have shown that thrust vectoring can be provided by multifunction (nonaxisymmetric) nozzles. Most of this research has been conducted on pitch vectoring at both static and forward flight conditions. Recent efforts have been aimed at evaluating yaw vectoring concepts at static (wind off) conditions. This paper summarizes results for three different twin-engine fighter configurations tested over a Mach number range of 0.15 to 2.47 at angles of attack up to 35 deg. The objective of these investigations was to determine the multiaxis control power characteristics provided by thrust vectoring. All three configurations employed two-dimensional convergent-divergent nozzles which provided pitch vectoring by differential deflection of the upper and lower nozzle divergent flaps. Three different means of yaw vectoring were tested: (1) a translating nozzle sidewall; (2) yaw flaps located in the nozzle sidewalls; and (3) canted nozzles. These investigations were conducted in the Langley 16-Foot Transonic Tunnel and the Lewis 10x10-Foot Supersonic Tunnel. Longitudinal and direction control power from thrust vectoring was greater than that provided by aerodynamic control effectors at low speed or at high angles of attack.

Capone, F. J.; Mason, M. L.

1986-01-01

144

Quasi-optimal decentralized astatic automatic control system for asynchronous motor velocity control based on Lyapunov vector functions procedure  

Microsoft Academic Search

A procedure permitting the synthesis of an automatic control system of asynchronous motor velocity control using Bellman-Lyapunov\\u000a functions, as well as methods of decomposition, decentralization, and aggregation and Lyapunov functions has been developed;\\u000a it has resulted in suboptimal control. The system does not use vector control methods for motor control. Compared with frequency\\u000a control systems with velocity-closed loops, the proposed

V. F. Kudin; O. I. Kiselichnik

2008-01-01

145

Chemotherapy of human African trypanosomiasis: current and future prospects  

Microsoft Academic Search

Three of the four currently approved drugs for the treatment of African trypanosomiasis (sleeping sickness) were developed over 50 years ago. All of the current therapies are unsatisfactory for various reasons, including unacceptable toxicity, poor efficacy, undesirable route of administration, and drug resistance. The possible modes of action of these drugs are briefly reviewed, as are the possible mechanisms of

Alan H. Fairlamb

2003-01-01

146

Diagnostic and neuropathogenesis issues in human African trypanosomiasis  

Microsoft Academic Search

Human African trypanosomiasis, also known as sleeping sickness, is caused by protozoan parasites of the genus Trypanosoma, and is a major cause of human mortality and morbidity. The East African and West African variants, caused by Trypanosma brucei rhodesiense and Trypanosoma brucei gambiense, respectively, differ in their presentation but the disease is fatal if untreated. Accurate staging of the disease

Peter G. E. Kennedy

2006-01-01

147

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

148

Predicted distribution and movement of Glossina palpalis palpalis (Diptera: Glossinidae) in the wet and dry seasons in the Kogo trypanosomiasis focus (Equatorial Guinea).  

PubMed

The aim of this study was to predict the distribution and movement of populations of the tsetse fly, Glossina palpalis palpalis (Diptera: Glossinidae), in the wet and dry seasons and to analyze the impact of the use of mono-pyramidal traps on fly populations in the Kogo focus in 2004 and 2005. Three Glossina species are present in Kogo: Glossina palpalis palpalis, major HAT vector in West-Central Africa, Glossina caliginea, and Glossina tabaniformis. The apparent density (AD) of G. p. palpalis clearly fell from 1.23 tsetse/trap/day in July 2004 to 0.27 in December 2005. A significant reduction in the mean AD for this species was noted between seasons and years. The diversity of Glossina species was relatively low at all the sampling points; G. p. palpalis clearly predominated over the other species and significantly dropped as a consequence of control activities. The predictive models generated for the seasonal AD showed notable differences not only in the density but in the distribution of the G. p. palpalis population between the rainy and dry season. The mono-pyramidal traps have proven to be an effective instrument for reducing the density of the tsetse fly populations, although given that the Kogo trypanosomiasis focus extends from the southern Equatorial Guinea to northern Gabon, interventions need to be planned on a larger scale, involving both countries, to guarantee the long-term success of control. PMID:18260511

Cano, Jorge; Descalzo, Miguel Angel; Ndong-Mabale, Nicolás; Ndong-Asumu, Pedro; Bobuakasi, Leonardo; Nzambo-Ondo, Sisinio; Benito, Agustín; Roche, Jesús

2007-12-01

149

Virtual Laboratory for Intelligent Vector Control of AC Machines  

Microsoft Academic Search

This paper provides a description of an educational software for the application of neural network control to one case of nonlinear and unmodeled dynamic system as electrical drive for induction machines. This software facilitates practical teaching and learning about indirect field orientation control (IFOC) of induction machines and about intelligent control of induction machines with Real Time Recurrent Neural Networks

L. F. Zorzano; J. Zorzano; A. Martinez; A. Zorzano; J. Vicuna

2007-01-01

150

A lazy learning control method using support vector regression  

Microsoft Academic Search

Lazy Learning is a new modeling method using memory-based learning. It is applied to control methods using a modeling technique. This paper proposes a new method that can be applied to position control. This method provides a way of setting the query point. Lazy Learning thus performs as a controller in the proposed method, not as an inverse model of

M. Kobayashi; Y. Konishi; H. Ishigaki

2007-01-01

151

Global Trends in the Use of Insecticides to Control Vector-Borne Diseases  

PubMed Central

Background: Data on insecticide use for vector control are essential for guiding pesticide management systems on judicious and appropriate use, resistance management, and reduction of risks to human health and the environment. Objective: We studied the global use and trends of insecticide use for control of vector-borne diseases for the period 2000 through 2009. Methods: A survey was distributed to countries with vector control programs to request national data on vector control insecticide use, excluding the use of long-lasting insecticidal nets (LNs). Data were received from 125 countries, representing 97% of the human populations of 143 targeted countries. Results: The main disease targeted with insecticides was malaria, followed by dengue, leishmaniasis, and Chagas disease. The use of vector control insecticides was dominated by organochlorines [i.e., DDT (dichlorodiphenyltrichloroethane)] in terms of quantity applied (71% of total) and by pyrethroids in terms of the surface or area covered (81% of total). Global use of DDT for vector control, most of which was in India alone, was fairly constant during 2000 through 2009. In Africa, pyrethroid use increased in countries that also achieved high coverage for LNs, and DDT increased sharply until 2008 but dropped in 2009. Conclusions: The global use of DDT has not changed substantially since the Stockholm Convention went into effect. The dominance of pyrethroid use has major implications because of the spread of insecticide resistance with the potential to reduce the efficacy of LNs. Managing insecticide resistance should be coordinated between disease-specific programs and sectors of public health and agriculture within the context of an integrated vector management approach. PMID:22251458

van den Berg, Henk; Zaim, Morteza; Soares, Agnes; Ameneshewa, Birkinesh; Mnzava, Abraham; Hii, Jeffrey; Dash, Aditya Prasad; Ejov, Mikhail

2012-01-01

152

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

NASA Astrophysics Data System (ADS)

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.

Hida, Hajime; Tomigashi, Yoshio; Kishimoto, Keiji

153

A Review of Ecological Factors Associated with the Epidemiology of Wildlife Trypanosomiasis in the Luangwa and Zambezi Valley Ecosystems of Zambia  

PubMed Central

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. PMID:22693499

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

2012-01-01

154

Adaptive self-tuning MTPA vector controller for IPMSM drive system  

Microsoft Academic Search

This paper presents an adaptive self-tuning maximum torque per ampere (MTPA) vector controller for an interior permanent-magnet synchronous motor (IPMSM) drive system. The control scheme consists of a synchronous frame decoupling current controller, MTPA torque controller, and adaptive parameter estimator. The estimator is applied to the q-axis current dynamics as the d-axis inductance can be assumed to be constant without

Yasser Abdel-Rady Ibrahim Mohamed; Tsing K. Lee

2006-01-01

155

Omni-axis secondary injection thrust vector control system  

NASA Technical Reports Server (NTRS)

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.

Kirkley, D. J.

1973-01-01

156

A new space vector based control method for UPS systems powering nonlinear and unbalanced loads  

Microsoft Academic Search

In this paper a new real time space vector based control strategy is presented for 3-phase UPS systems powering nonlinear and unbalanced loads. The proposed control strategy generates the inverter reference and gating signals in closed loop and guarantees high quality output voltages at the load terminals. The approach, which is implemented on a DSP, adapts to a wide variation

Uffe Bomp Jensen; Prasad N. Enjeti; Frede Blaabjerg

2000-01-01

157

High-Performance Vector-Controlled AC Motor Drives: Applications and New Technologies  

Microsoft Academic Search

A high-performance ac motor control has been developed by employing the vector control concept. Its versatility has been proven through the six years of experience in applications to pinch roll drives of continuous casting plants, machine tool spindle drives, and other drive systems in industry. Equivalent torque characteristics are achieved with ac motors compared to dc motors without direct detection

Tsuneo Kume; Takanobu Iwakane

1987-01-01

158

Dynamic emulation of mechanical loads using a vector-controlled induction motor-generator set  

Microsoft Academic Search

This paper addresses the problem of electronic emulation of both linear and nonlinear mechanical loads using a vector-controlled induction machine dynamometer. It is shown that a basic emulation scheme where the dynamometer torque demand is derived from the inverse dynamics of the emulated load is not generally viable, especially if the emulated load is part of a closed-loop speed control

Z. Hakan Akpolat; Greg M. Asher; Jon C. Clare

1999-01-01

159

Smart vector-decoupling control of three phase rectifiers for grid connectivity of sustainable energy sources  

Microsoft Academic Search

In this paper, some of the aspects related to the connectivity of DC microgrids to the main grid are investigated. The system under study is dependent mainly on sustainable energy sources. A fully controlled rectifier has been designed to tie the DC grid with the AC one. A vector decoupling controlled sinusoidal pulse width modulation (SPWM) technique has been used

Ahmed Mohamed; Osama A. Mohammed

2011-01-01

160

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...

161

Direct torque control of induction machines using space vector modulation  

Microsoft Academic Search

A direct induction machine torque control method based on predictive, deadbeat control of the torque and flux is presented. By estimating the synchronous speed and the voltage behind the transient reactance, the change in torque and flux over the switching period is calculated. The stator voltage required to cause the torque and flux to be equal to their respective reference

Thomas G. Habetler; Francesco Profumo; Michele Pastorelli; Leon M. Tolbert

1992-01-01

162

Challenges encountered using standard vector control measures for dengue in Boa Vista, Brazil  

PubMed Central

Abstract Problem In 2010, dengue virus (DENV) serotype–4 was detected during a dengue outbreak in the Amazonian city of Boa Vista. At that time Brazil was already endemic for DENV-1, DENV-2 and DENV-3. This was the first time DENV-4 was observed in the country after it was initially detected and eliminated in 1981. Approach To hinder the spread of DENV-4 throughout Brazil, standard vector control measures were intensified. Vector control professionals visited 56?837 households in 22 out of 31 districts of Boa Vista, to eliminate mosquito-breeding sites. Water storage containers were treated with the larvicide diflubenzuron, and deltamethrin was sprayed for adult Aedes aegypti mosquitoes. Fifteen days later, a second larvae survey and additional deltamethrin applications were performed. Local setting In Brazil, dengue vector control is managed at all three government levels. Regular surveillance of Aedes aegypti is done four to six times a year to strengthen mosquito control activities in areas with high-vector density. Educational dengue control campaigns in communities are scarce, especially between outbreaks. Relevant changes In spite of extensive implementation of all standard control actions recommended by the Brazilian dengue control programme, only a slight decrease in mosquito density was detected. Lessons learnt There is a need to redesign all levels of dengue control. Public consultation and engagement, behaviour change and actions that go beyond technical impositions are required. Vector control programme managers need to reflect on what constitutes good practices and whether intermittent information campaigns are effective measures for dengue prevention and control. PMID:25378760

Valle, Denise

2014-01-01

163

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

PubMed Central

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

Gürtler, Ricardo E

2011-01-01

164

Trypanosoma brucei gambiense trypanosomiasis in Terego county, northern Uganda, 1996: a lot quality assurance sampling survey.  

PubMed

We estimated the pre-intervention prevalence of Trypanosoma brucei gambiense (Tbg) trypanosomiasis using the lot quality assurance sampling (LQAS) methods in 14 parishes of Terego County in northern Uganda. A total of 826 participants were included in the survey sample in 1996. The prevalence of laboratory confirmed Tbg trypanosomiasis adjusted for parish population sizes was 2.2% (95% confidence interval =1.1-3.2). This estimate was consistent with the 1.1% period prevalence calculated on the basis of cases identified through passive and active screening in 1996-1999. Ranking of parishes in four categories according to LQAS analysis of the 1996 survey predicted the prevalences observed during the first round of active screening in the population in 1997-1998 (P < 0.0001, by chi-square test). Overall prevalence and ranking of parishes obtained with LQAS were validated by the results of the population screening, suggesting that these survey methods may be useful in the pre-intervention phase of sleeping sickness control programs. PMID:15100452

Hutin, Yvan J F; Legros, Dominique; Owini, Vincent; Brown, Vincent; Lee, Evan; Mbulamberi, Dawson; Paquet, Christophe

2004-04-01

165

A network population model of the dynamics and control of African malaria vectors  

PubMed Central

A more robust assessment of malaria control through mosquito larval habitat destruction will come from a better understanding of the distribution, productivity and connectivity of breeding sites. The present study examines the significance of vector dispersal ability, larval habitat stability and productivity on the persistence and extinction of a mosquito population inhabiting a dynamic network of breeding sites. We use this novel method of vector modelling to show that when dispersal is limited or vector distribution is patchy, the spread and growth of a mosquito population at the onset of a rainy season is delayed and extinction through larval habitat destruction is more readily achieved. We also determine the impact of two alternative dry-season survival strategies on mosquito dynamics. Simulations suggest that if adult vectors remain dormant throughout the dry season, the stage structure of the population will be synchronized at the onset of the wet season and its growth will be delayed. In contrast, a population that continues to breed throughout the dry season grows more rapidly and is more difficult to control. Our findings have important implications on the development of integrative malaria vector management strategies and on the understanding of dry-season survival mechanisms of African malaria vectors. PMID:20813387

Yakob, Laith; Yan, Guiyun

2010-01-01

166

A set of ontologies to drive tools for the control of vector-borne diseases  

PubMed Central

We are developing a set of ontologies dealing with vector-borne diseases as well as the arthropod vectors that transmit them. After building ontologies for mosquito and tick anatomy we continued this project with an ontology of insecticide resistance followed by a series of ontologies that describe malaria as well as physiological processes of mosquitoes that are relevant to, and involved in, disease transmission. These will later be expanded to encompass other vector-borne diseases as well as non-mosquito vectors. The aim of the whole undertaking, which is worked out in the frame of the international IDO (Infectious Disease Ontology) project, is to provide the community with a set of ontological tools that can be used both in the development of specific databases and, most importantly, in the construction of decision support systems (DSS) to control these diseases. PMID:20363364

Topalis, Pantelis; Dialynas, Emmanuel; Mitraka, Elvira; Deliyanni, Elena; Siden-Kiamos, Inga; Louis, Christos

2010-01-01

167

Determination of the role of cytokines using gene deficient mice in African trypanosomiasis infection.  

E-print Network

??African trypanosomiasis encompasses diseases caused by pathogenic trypanosomes, infecting both humans and animals alike. To determine the immunological role of IL=12 family members in Trypanosoma… (more)

Barkhuizen, Mark

2008-01-01

168

Spin vector control of a spinning space station  

NASA Technical Reports Server (NTRS)

Digital computer program simulates system and related functions. Program is intended for, but not limited to, altitude control studies of rotating space station. Russel's method of formulating and solving motion equations for system of rigid bodies connected by movable joints is applied. Program features are listed.

Hendricks, T.

1971-01-01

169

Cholesteric diffraction devices with a field-controlled grating vector  

Microsoft Academic Search

Electrically-controlled diffraction gratings are developed on the basis of a cholesteric liquid crystal confined between two transparent electrodes. The electrodes are coated with unidirectionally treated alignment layers. The initial state is planar, with the helix axis oriented normally to the electrodes. The applied field causes reorientation of molecules and creates structures modulated in the plane of the cell. Surface alignment

Sergey V. Shiyanovskii; Darius Subacius; Dmitry Voloschenko; Philip J. Bos; Oleg D. Lavrentovich

1998-01-01

170

Treatment options for second-stage gambiense human African trypanosomiasis.  

PubMed

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

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

2014-11-01

171

Towards the genetic control of insect vectors: An overview  

PubMed Central

Insects are responsible for the transmission of major infectious diseases. Recent advances in insect genomics and transformation technology provide new strategies for the control of insect borne pathogen transmission and insect pest management. One such strategy is the genetic modification of insects with genes that block pathogen development. Another is to suppress insect populations by releasing either sterile males or males carrying female-specific dominant lethal genes into the environment. Although significant progress has been made in the laboratory, further research is needed to extend these approaches to the field. These insect control strategies offer several advantages over conventional insecticide-based strategies. However, the release of genetically modified insects into the environment should proceed with great caution, after ensuring its safety, and acceptance by the target populations.

Abraham, Eappen G.; Cha, Sung-Jae; Jacobs-Lorena, Marcelo

2014-01-01

172

Eflornithine for the treatment of human African trypanosomiasis  

Microsoft Academic Search

Eflornithine is the only new molecule registered for the treatment of human African trypanosomiasis over the last 50 years. It is the drug used mainly as a back-up for melarsoprol refractory Trypanosoma brucei gambiense cases. The most commonly used dosage regimen for the treatment of T. b. gambiense sleeping sickness consists of 100 mg kg–1 body weight at intervals of 6 h for

Christian Burri; Reto Brun

2003-01-01

173

A Cluster-Randomized Trial of Insecticide-Treated Curtains for Dengue Vector Control in Thailand  

PubMed Central

The efficacy of insecticide-treated window curtains (ITCs) for dengue vector control was evaluated in Thailand in a cluster-randomized controlled trial. A total of 2,037 houses in 26 clusters was randomized to receive the intervention or act as control (no treatment). Entomological surveys measured Aedes infestations (Breteau index, house index, container index, and pupae per person index) and oviposition indices (mean numbers of eggs laid in oviposition traps) immediately before and after intervention, and at 3-month intervals over 12 months. There were no consistent statistically significant differences in entomological indices between intervention and control clusters, although oviposition indices were lower (P < 0.01) in ITC clusters during the wet season. It is possible that the open housing structures in the study reduced the likelihood of mosquitoes making contact with ITCs. ITCs deployed in a region where this house design is common may be unsuitable for dengue vector control. PMID:23166195

Lenhart, Audrey; Trongtokit, Yuwadee; Alexander, Neal; Apiwathnasorn, Chamnarn; Satimai, Wichai; Vanlerberghe, Veerle; Van der Stuyft, Patrick; McCall, Philip J.

2013-01-01

174

A Vector Control for Grid-connected Wind Power Generation with Doubly Fed Induction Generator  

NASA Astrophysics Data System (ADS)

Recently, doubly fed induction generator (DFIG) and synchronous generator are mostly applied for wind power generation due to high efficiently for wind energy capture. An inverter system is required to control wind turbine speed and power factor in those generators. The inverter rating of the synchronous generator equals to generator rating. However, DFIG has the advantage that the inverter rating is about 25% to the generator rating. The paper describes a vector control of DFIG inter-connected to power line. The performance of proposed vector control is examined using power system simulation software PSCAD/EMTDC for the DFIG inter-connected to 6.6kv distribution line. The results show good dynamic responses and high accuracy to the stator active power control and the stator reactive power control.

Kai, Takaaki; Tanaka, Yuji; Kaneda, Hirotoshi; Kobayashi, Daichi; Tanaka, Akio

175

Heritable strategies for controlling insect vectors of disease  

PubMed Central

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

Burt, Austin

2014-01-01

176

Certifying achievement in the control of Chagas disease native vectors: what is a viable scenario?  

PubMed

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

Hashimoto, Ken; Yoshioka, Kota

2014-09-01

177

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...

178

Space Vector PWM Control Synthesis for a H-Bridge Drive in Electric Vehicles  

E-print Network

Space Vector PWM Control Synthesis for a H-Bridge Drive in Electric Vehicles A. Kolli1 , Student Magnet Synchronous Machine in Electric Vehicle application. First, a short survey of existing power regarding compactness and vehicle integration. More specifically electric vehicles (EVs) require a high

Paris-Sud XI, Université de

179

MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATIN AMERICA - A 16TH SYMPOSIUM  

Technology Transfer Automated Retrieval System (TEKTRAN)

The 16th Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 72nd Annual Meeting in Detroit, Michigan in February 2006. The principal objective, as for the previous 15 symposia, was to promote participation in the AMCA by vector cont...

180

Control of a Biped Robot With Support Vector Regression in Sagittal Plane  

Microsoft Academic Search

This paper describes the control of an autonomous biped robot that uses the support vector regression (SVR) method for its sagittal balance. This SVR uses the zero moment point (ZMP) position and its variation as input and the torso correction of the robot's body as output. As the robot model used segments the robot into eight parts, it is difficult

João P. Ferreira; Manuel Marques Crisóstomo; A. Paulo Coimbra; Bernardete Ribeiro

2009-01-01

181

An error control scheme for transmission of vector quantization data over noisy channels  

Microsoft Academic Search

This paper presents an error control scheme for transmitting vector-quantized data over noisy channels. First, we review a self-organizing feature map (SOFM) based approach to construct the mapping from the codebook of the quantizer to the channel signal set of the communication system. This approach is robust with respect to channel noise even if we do not use any error

Chi-Sing Leung; Lai-Wan Chan

1998-01-01

182

Speed sensorless vector control of induction motor using extended Kalman filter  

Microsoft Academic Search

A vector control of an induction motor by an estimated speed using an extended Kalman filter is proposed. With this method, the states are composed of stator current and rotor flux. The rotor speed is regarded as a parameter, and the composite states consist of the original states and the rotor speed. The extended Kalman filter is employed to identify

Young-Real Kim; Seung-Ki Sul; Min-Ho Park

1994-01-01

183

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

PubMed Central

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

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

184

Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction  

NASA Astrophysics Data System (ADS)

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

Ono, Hiroshi; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

2014-03-01

185

A simple solution for vector control in vertical alveolar distraction osteogenesis.  

PubMed

One of the important and frequent complications in alveolar distraction osteogenesis is vectorial change of the transport segment. This report presents a simple solution for vector angulation control by placing intermaxillary fixation screws intraoperatively. Advantages of the technique are also discussed. PMID:25295887

Kocyigit, Ismail Doruk; Tuz, Hakan H; Ozgul, Ozkan; Coskunses, Fatih Mehmet; Kisnisci, Reha S

2014-10-01

186

Characterization of Spatial Repellent, Contact Irritant and Toxicant Chemical Actions of Standard Vector Control Compounds  

Technology Transfer Automated Retrieval System (TEKTRAN)

A previously described modular high-throughput screening system (HITTS) was used to characterize the spatial repellent, contact irritant and toxicant chemical actions of 14 compounds with a history of use in vector control. The response of F1-F4 Aedes aegypti to various concentrations of four organo...

187

Investigations on the control of bilharziasis vectors in Israel*  

PubMed Central

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

Saliternik, Z.; Witenberg, G.

1959-01-01

188

A new space-vector-based control method for UPS systems powering nonlinear and unbalanced loads  

Microsoft Academic Search

In this paper, a new real-time space-vector-based control strategy is presented for three-phase uninterruptible power supply systems powering nonlinear and unbalanced loads. The proposed control strategy generates the inverter reference and gating signals in closed loop and guarantees high-quality output voltages at the load terminals. The approach, which is implemented on a digital signal processor, adapts to a wide variation

U. Burup; Prasad N. Enjeti; Frede Blaabjerg

2001-01-01

189

Park vector based sliding mode control of UPS with unbalanced and nonlinear load  

Microsoft Academic Search

The main contribution of this chapter is a new Park vector based variable structure control (VSC) method. In this chapter\\u000a an inverter is taken to be a member of Variable Structure Multy Imput Multy Output System.\\u000a \\u000a The design of a sliding mode controller consists of two main steps. Firstly, the design of the sliding surface, secondly,\\u000a the design of the

Péter Korondi; Hideki Hashimoto

190

Legal aspects of public health: difficulties in controlling vector-borne and zoonotic diseases in Brazil.  

PubMed

In recent years, vector-borne and zoonotic diseases have become a major challenge for public health. Dengue fever and leptospirosis are the most important communicable diseases in Brazil based on their prevalence and the healthy life years lost from disability. The primary strategy for preventing human exposure to these diseases is effective insect and rodent control in and around the home. However, health authorities have difficulties in controlling vector-borne and zoonotic diseases because residents often refuse access to their homes. This study discusses aspects related to the activities performed by Brazilian health authorities to combat vector-borne and zoonotic diseases, particularly difficulties in relation to the legal aspect, which often impede the quick and effective actions of these professionals. How might it be possible to reconcile the need to preserve public health and the rule on the inviolability of the home, especially in the case of abandoned properties or illegal residents and the refusal of residents to allow the health authority access? Do residents have the right to hinder the performance of health workers even in the face of a significant and visible focus of disease transmission? This paper argues that a comprehensive legal plan aimed at the control of invasive vector-borne and zoonotic diseases including synanthropic animals of public health importance should be considered. In addition, this paper aims to bridge the gap between lawyers and public health professionals and to facilitate communication between them. PMID:25051187

Mendes, Marcílio S; de Moraes, Josué

2014-11-01

191

Impact of vector control on a dengue fever outbreak in Trinidad, West Indies, in 1998.  

PubMed

In 1998, Trinidad experienced its first major outbreak of dengue haemorrhagic fever. Data from the Trinidad Public Health Laboratory, the National Surveillance Unit and Insect Vector Control Division, Ministry of Health, Trinidad and Tobago were analysed to determine the impact of vector control measures on the dengue outbreak. Geographical Information Systems (GIS)/Global Positioning Systems (GPS) were used to map cases and to distinguish epidemiological clusters. The Aedes aegypti population densities were higher than the 5% transmission threshold in all counties. The spatial distribution of dengue fever cases was significantly correlated with the heavily populated east-west corridor in the north and several distinctly separate clusters in the western part of the island. The temporal distribution patterns showed significantly more dengue fever cases occurring during the rainy season than during the dry season. This study documents the importance of vector control in the prevention of dengue transmission since no vaccine is currently available, and emphasizes the urgent need to understand better the environmental factors which contribute to the proliferation of this disease vector Ae. aegypti. PMID:16045461

Chadee, Dave D; Williams, Fiona L R; Kitron, Uriel D

2005-08-01

192

Immunosuppression in bovine trypanosomiasis: Field studies using foot-and-mouth disease vaccine and clostridial vaccine  

Microsoft Academic Search

The immunosuppressive effect of naturally acquired trypanosomiasis was investigated in four groups of zebu cattle maintained in an area of high tsetse fly challenge in Western Ethiopia. Two of the groups remained without chemoprophylaxis against trypanosomiasis and became parasitaemic. The animals of one of these two groups received a polyvalent foot-and-mouth disease vaccine and the cattle of the other group

J. M. Scott; R. G. Pegram; P. H. Holmes; T. W. F. Pay; P. A. Knight; F. W. JENurbros; G. M. Urquhart

1977-01-01

193

Prevention and control of neglected tropical diseases: overview of randomized trials, systematic reviews and meta-analyses  

PubMed Central

Abstract Objective To analyse evidence from randomized controlled trials (RCTs) on the prevention and control of neglected tropical diseases (NTDs) and to identify areas where evidence is lacking. Methods The Cochrane Central Register of Controlled Trials and PubMed were searched for RCTs and the Cochrane Database of Systematic Reviews and PubMed were searched for meta-analyses and systematic reviews, both from inception to 31 December 2012. Findings Overall, 258 RCTs were found on American trypanosomiasis, Buruli ulcer, dengue, geohelminth infection, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, rabies, schistosomiasis or trachoma. No RCTs were found on cysticercosis, dracunculiasis, echinococcosis, foodborne trematodes, or human African trypanosomiasis. The most studied diseases were geohelminth infection (51 RCTs) and leishmaniasis (46 RCTs). Vaccines, chemoprophylaxis and interventions targeting insect vectors were evaluated in 113, 99 and 39 RCTs, respectively. Few addressed how best to deliver preventive chemotherapy, such as the choice of dosing interval (10) or target population (4), the population coverage needed to reduce transmission (2) or the method of drug distribution (1). Thirty-one publications containing 32 systematic reviews (16 with and 16 without meta-analyses) were found on American trypanosomiasis, dengue, geohelminths, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis or trachoma. Together, they included only 79 of the 258 published RCTs (30.6%). Of 36 interventions assessed, 8 were judged effective in more than one review. Conclusion Few RCTs on the prevention or control of the principal NTDs were found. Trials on how best to deliver preventive chemotherapy were particularly rare. PMID:24839325

Kappagoda, Shanthi

2014-01-01

194

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

195

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

PubMed Central

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. PMID:18667091

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

2008-01-01

196

Integrated vector management for malaria control in Uganda: knowledge, perceptions and policy development  

PubMed Central

Background Integrated vector management (IVM) is increasingly being recommended as an option for sustainable malaria control. However, many malaria-endemic countries lack a policy framework to guide and promote the approach. The objective of the study was to assess knowledge and perceptions in relation to current malaria vector control policy and IVM in Uganda, and to make recommendations for consideration during future development of a specific IVM policy. Methods The study used a structured questionnaire to interview 34 individuals working at technical or policy-making levels in health, environment, agriculture and fisheries sectors. Specific questions on IVM focused on the following key elements of the approach: integration of chemical and non-chemical interventions of vector control; evidence-based decision making; inter-sectoral collaboration; capacity building; legislation; advocacy and community mobilization. Results All participants were familiar with the term IVM and knew various conventional malaria vector control (MVC) methods. Only 75% thought that Uganda had a MVC policy. Eighty percent (80%) felt there was inter-sectoral collaboration towards IVM, but that it was poor due to financial constraints, difficulties in involving all possible sectors and political differences. The health, environment and agricultural sectors were cited as key areas requiring cooperation in order for IVM to succeed. Sixty-seven percent (67%) of participants responded that communities were actively being involved in MVC, while 48% felt that the use of research results for evidence-based decision making was inadequate or poor. A majority of the participants felt that malaria research in Uganda was rarely used to facilitate policy changes. Suggestions by participants for formulation of specific and effective IVM policy included: revising the MVC policy and IVM-related policies in other sectors into a single, unified IVM policy and, using legislation to enforce IVM in development projects. Conclusion Integrated management of malaria vectors in Uganda remains an underdeveloped component of malaria control policy. Cooperation between the health and other sectors needs strengthening and funding for MVC increased in order to develop and effectively implement an appropriate IVM policy. Continuous engagement of communities by government as well as monitoring and evaluation of vector control programmes will be crucial for sustaining IVM in the country. PMID:22243516

2012-01-01

197

Evaluation of the Diagnostic Accuracy of Prototype Rapid Tests for Human African Trypanosomiasis  

PubMed Central

Background Diagnosis of human African trypanosomiasis (HAT) remains a challenge both for active screening, which is critical in control of the disease, and in the point-of-care scenario where early and accurate diagnosis is essential. Recently, the first field deployment of a lateral flow rapid diagnostic test (RDT) for HAT, “SD BIOLINE HAT” has taken place. In this study, we evaluated the performance of “SD BIOLINE HAT” and two new prototype RDTs. Methodology/Principal Findings The performance of “SD BIOLINE HAT” and 2 prototype RDTs was tested using archived plasma from 250 Trypanosoma brucei gambiense patients, and 250 endemic controls. As well as comparison of the sensitivity and specificity of each device, the performance of individual antigens was assessed and the hypothetical performance of novel antigen combinations extrapolated. Neither of the prototype devices were inferior in sensitivity or specificity to “SD BIOLINE HAT” (sensitivity 0.82±0.01, specificity 0.97±0.01, 95% CI) at the 5% margins, while one of the devices (BBI) had significantly superior sensitivity (0.88±0.03). Analysis of the performance of individual antigens was used to model new antigen combinations to be explored in development of the next generation of HAT RDTs. The modelling showed that an RDT using two recombinant antigens (rLiTat1.5 and rISG65) would give a performance similar to the best devices in this study, and would also offer the most robust performance under deteriorating field conditions. Conclusions/Significance Both “SD BIOLINE HAT” and the prototype devices performed comparably well to one another and also to the published performance range of the card agglutination test for trypanosomiasis in sensitivity and specificity. The performance of individual antigens enabled us to predict that an all-recombinant antigen RDT can be developed with an accuracy equivalent to “ SD BIOLINE HAT.” Such an RDT would have advantages in simplified manufacture, lower unit cost and assured reproducibility. PMID:25521120

Sternberg, Jeremy M.; Gierli?ski, Marek; Biéler, Sylvain; Ferguson, Michael A. J.; Ndung'u, Joseph M.

2014-01-01

198

Method for Estimating Maximum Torque Control Axis of Interior Permanent Magnet Synchronous Motors for an Arbitrary Current Vector  

NASA Astrophysics Data System (ADS)

A method for directly estimating the axis corresponding to the current phase in maximum torque per ampere (MTPA) control is proposed for sensorless vector control. This axis is called the maximum torque control (MTC) axis. In past studies concerning such methods, the behavior of the axis has been considered only for the case of MTPA control and not for an arbitrary current vector (with flux weakening control) that has a phase different from that for MTPA control. This paper enhances the definition of the MTC axis for an arbitrary current vector, describes an extended EMF model based on the MTC axis, and presents a method that can directly estimate the axis for an arbitrary current vector with flux weakening control. The effectiveness of the proposed method is confirmed by numerical analysis results.

Tomigashi, Yoshio; Ueyama, Kenji

199

Suppression of dengue transmission by application of integrated vector control strategies at sero-positive GIS-based foci.  

PubMed

A serological survey of primary school children from six schools in Chachoengsao Province, Thailand, was performed at the end of the peak of dengue transmission. GIS analysis of sero-positive cases was carried out to determine transmission foci. Vector control implementation was conducted in the foci and also within 100 meters around the foci in the treated areas by community participation in collaboration with the local government. Vector control strategies included source reduction together with the use of screen covers, a combination of Bacillus thuringiensis subsp. israelensis and Mesocyclops thermocyclopoides, and lethal ovitraps. Implementation of vector control strategies in the foci was continued until the end of the rainy season. Vector control effectiveness was monitored using entomological, serological, and clinical parameters. Results showed a significant reduction of dengue vectors as well as a decrease in sero-positive children and clinical cases in treated areas when compared with untreated areas. PMID:18187787

Kittayapong, Pattamaporn; Yoksan, Sutee; Chansang, Uruyakorn; Chansang, Chitti; Bhumiratana, Amaret

2008-01-01

200

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

NASA Technical Reports Server (NTRS)

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.

Lallman, F. J.

1985-01-01

201

A current error space vector based hysteresis controller with constant switching frequency and simple online boundary computation for VSI fed IM drive  

Microsoft Academic Search

This paper proposes a simple current error space vector based hysteresis controller for two-level inverter fed Induction Motor (IM) drives. This proposed hysteresis controller retains all advantages of conventional current error space vector based hysteresis controllers like fast dynamic response, simple to implement, adjacent voltage vector switching etc. The additional advantage of this proposed hysteresis controller is that it gives

Rijil Ramchand; Chintan Patel; Anandarup Das; K. Sivakumar; K. Gopakumar; L. M. Patnaik

2010-01-01

202

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

PubMed Central

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

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

2014-01-01

203

Temephos Resistance in Aedes aegypti in Colombia Compromises Dengue Vector Control  

PubMed Central

Background Control and prevention of dengue relies heavily on the application of insecticides to control dengue vector mosquitoes. In Colombia, application of the larvicide temephos to the aquatic breeding sites of Aedes aegypti is a key part of the dengue control strategy. Resistance to temephos was recently detected in the dengue-endemic city of Cucuta, leading to questions about its efficacy as a control tool. Here, we characterize the underlying mechanisms and estimate the operational impact of this resistance. Methodology/Principal Findings Larval bioassays of Ae. aegypti larvae from Cucuta determined the temephos LC50 to be 0.066 ppm (95% CI 0.06–0.074), approximately 15× higher than the value obtained from a susceptible laboratory colony. The efficacy of the field dose of temephos at killing this resistant Cucuta population was greatly reduced, with mortality rates <80% two weeks after application and <50% after 4 weeks. Neither biochemical assays nor partial sequencing of the ace-1 gene implicated target site resistance as the primary resistance mechanism. Synergism assays and microarray analysis suggested that metabolic mechanisms were most likely responsible for the temephos resistance. Interestingly, although the greatest synergism was observed with the carboxylesterase inhibitor, DEF, the primary candidate genes from the microarray analysis, and confirmed by quantitative PCR, were cytochrome P450 oxidases, notably CYP6N12, CYP6F3 and CYP6M11. Conclusions/Significance In Colombia, resistance to temephos in Ae. aegypti compromises the duration of its effect as a vector control tool. Several candidate genes potentially responsible for metabolic resistance to temephos were identified. Given the limited number of insecticides that are approved for vector control, future chemical-based control strategies should take into account the mechanisms underlying the resistance to discern which insecticides would likely lead to the greatest control efficacy while minimizing further selection of resistant phenotypes. PMID:24069492

Grisales, Nelson; Poupardin, Rodolphe; Gomez, Santiago; Fonseca-Gonzalez, Idalyd; Ranson, Hilary; Lenhart, Audrey

2013-01-01

204

Algorithms of information authentication for the automatic control systems on the basis of structures in finite vector spaces  

Microsoft Academic Search

New algebraic structures differing from the existing ones in new kinds of operations over finite sets of m-dimensional vectors (m ? 2) with discrete components were developed to construct information authentication algorithms for the automatic control\\u000a systems. The operation of vector multiplication including multiplication and summation of the coordinates of the multiplied\\u000a vectors modulo simple number p was defined. Depending

N. A. Moldovyan

2008-01-01

205

Human African trypanosomiasis in non-endemic countries.  

PubMed

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. PMID:25650203

Sudarshi, Darshan; Brown, Mike

2015-02-01

206

Characterization of Spatial Repellent, Contact Irritant, and Toxicant Chemical Actions of Standard Vector Control Compounds 1  

Microsoft Academic Search

2 ABSTRACT. A previously described modular high-throughput screening system was used to characterize the spatial repellent, contact irritant, and toxicant chemical actions of 14 compounds historically used or under investigation for vector control. The response of F1-F4 Aedes aegypti (Thailand strain) to various concentrations of 4 organochlorines (chlordane, DDT, dieldrin, methoxychlor); 4 pyrethroids (alphacy- permethrin, cypermethrin, deltamethrin, permethrin); 3 organophosphates

Nicole L. Achee; Michael R. Sardelis; Isabelle Dusfour; Kamlesh R. Chauhan; John P. Grieco

2009-01-01

207

Robust vector control of induction motors using full-order observer in consideration of core loss  

Microsoft Academic Search

This paper proposes a method for designing a robust full-order observer for vector-controlled induction motors taking core loss into account. Although conventional research focuses on parameter identification, global stability of the identification remains questionable. Therefore, robustness against some parameters is required. This paper describes the design of a robust full-order observer which takes core loss into account, using both the

Masaru Hasegawa; Shinichi Furutani; Shinji Doki; Shigeru Okuma

2003-01-01

208

Robust vector control of induction motor using full-order observer in consideration of core loss  

Microsoft Academic Search

This paper proposes a method for designing a robust full-order observer for vector-controlled induction motors taking core loss into account.. Although most of the literature focuses on parameter identification, the global stability of the identification remains questionable. There is therefore a need for robustness with respect, to some parameters. This paper describes the design of a robust full-order observer which

Masaru Hasegawa; Shinichi Furutani; Shinji Doki; Shigeru Okuma

2002-01-01

209

Identification and characterization of field sites for genetic control of disease vectors  

Microsoft Academic Search

Genetic control of disease vectors consists of a large variety of approaches. Each of these bring along an often-substantial number of prerequisites in order to stand a chance of being successful. Of the large number of trials documented, only few have taken the scale and scope of operation to sustain long-term area-wide benefits. Broadly speaking, two categories of issues will

Bart G. J. Knolsand; Hervé Bossin

2003-01-01

210

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

PubMed Central

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

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

2009-01-01

211

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

PubMed Central

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

2014-01-01

212

All-in-One inducible lentiviral vector systems based on drug controlled FLP recombinase.  

PubMed

Site specific recombinases are frequently used as gene switches in transgenic animals where recombination is induced by drug treatment or by tissue specific recombinase expression. Alternatively, lentiviral gene transfer can be utilized for the genetic modification of a wide variety of cell types, albeit systems for tight control of transcriptional activity are scarce. Here, we combined lentiviral gene transfer and the development of a tightly drug-controlled FLP recombinase for the construction of "All-in-One" inducible gene expression systems. Tight control of FLP activity was achieved through N-terminal fusion with a FKBP12-derived conditional destruction domain and a C-terminal estrogen receptor binding domain making recombination dependent on the presence of Shield-1 and 4-hydroxytamoxifen. Exploiting the capacity of FLP to mediate excision and inversion, "All-in-One" lentiviral gene switch vector systems were generated where drug-induced recombination resulted in abrogation of FLP expression and subsequent overexpression or knockdown of the prototypical tumor suppressor phosphatase and tensin homolog PTEN. "All-in-One" vectors proved their functionality in a variety of hematopoietic cell lines, and primary murine bone marrow cells. Our new vector system thus combines the ease of lentiviral gene transfer and the power of site specific recombinases for analysis of gene function. PMID:24529624

Maetzig, Tobias; Kuehle, Johannes; Schwarzer, Adrian; Turan, Soeren; Rothe, Michael; Chaturvedi, Anuhar; Morgan, Michael; Ha, Teng Cheong; Heuser, Michael; Hammerschmidt, Wolfgang; Baum, Christopher; Schambach, Axel

2014-05-01

213

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

PubMed

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. PMID:22548779

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

2014-11-01

214

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

215

The digital autopilot for thrust vector control of the Shuttle Orbital maneuvering system  

NASA Technical Reports Server (NTRS)

This paper describes the requirements for and the design, development and performance of the digital autopilots (DAPs) for thrust vector control, utilizing the orbital maneuvering system (OMS) of the Space Shuttle Orbiter. The hardware and software requirements which caused the design to assume its current form are described. Also, the design synthesis, which considered rigid body stability margins, bending and slosh stabilization, guidance loop compensation, off-nominal performance and hardware and software limitations is presented. The performance of the OMS control system is summarized utilizing flight data from the first three Space Transportation System (STS) flights.

Penchuk, A.; Croopnick, S.

1982-01-01

216

Optical control of retrogradely infected neurons using drug-regulated "TLoop" lentiviral vectors.  

PubMed

Many approaches that use viral vectors to deliver transgenes have limited transduction efficiency yet require high levels of transgene expression. In particular, infection via axon terminals is relatively inefficient but is a powerful means of achieving infection of specific neuron types. Combining this with optogenetic approaches requires high gene expression levels that are not typically achieved with nontoxic retrogradely infecting vectors. We generated rabies glycoprotein-pseudotyped lentiviral vectors that use a positive feedback loop composed of a Tet promoter driving both its own tetracycline-dependent transcription activator (tTA) ("TLoop") and channelrhodopsin-2-YFP (ChR2YFP). We show that TLoop vectors strongly express proteins in a drug-controllable manner in neurons that project to injection sites within the mouse brain. After initial infection, the virus travels retrogradely, stably integrates into the host genome, and expresses gene products. The expression is robust and allows optogenetic studies of neurons projecting to the location of virus injection, as demonstrated by fluorescence-targeted intracellular recordings. ChR2YFP expression did not cause observable signs of toxicity and continued for up to 6 mo after infection. Expression can be reversibly blocked by administration of doxycycline, if necessary, for expression of gene products that might be more toxic. Overall, we present a system that will allow researchers to achieve high levels of gene expression even in the face of inefficient viral transduction. The particular vectors that we demonstrate may enhance efforts to gain a precise understanding of the contributions of specific types of projection neurons to brain function. PMID:24572099

Cetin, Ali; Callaway, Edward M

2014-05-01

217

African trypanosomiasis alters prostaglandin production by murine peritoneal macrophages.  

PubMed Central

Many factors contribute to the severe immunosuppression associated with African trypanosomiasis. Macrophages have been shown to be important target cells which after uptake of parasites, mediate immune dysfunction in vivo. We observed that infection of mice with Trypanosome brucei brucei (clone NIM 6) induces profound changes in arachidonic acid metabolism and prostaglandin (PG) secretion by macrophages. Normal macrophages release more PGI2 than PGE2 and production of both these prostaglandins is stimulated equally by endotoxin (LPS). Macrophages taken from NIM 6 infected mice at the peak of the first parasitaemia, release increased amounts of PGE2 and are hyperresponsive to LPS stimulation, while PGI2 secretion remains normal. As the infection progresses, there is a striking decrease in both basal PGE2 and PGI2 secretion and the ability of macrophages to respond to LPS. By the third week of infection, shortly before death, peritoneal macrophages resemble thioglycollate elicited macrophages in their inability to be stimulated by LPS to synthesize prostaglandins. Infection with a more virulent clone of T. brucei (NIM9) results in suppression of both PGE2 and PGI2 release by day 9 of infection. The increased production of PGE2 by macrophages during the height of infection is likely to contribute to the general immunosuppression associated with African trypanosomiasis. Images Fig. 1 PMID:6391763

Fierer, J; Salmon, J A; Askonas, B A

1984-01-01

218

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

PubMed

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 will be needed if current gains in malaria control are not to be reversed. PMID:24821917

Hemingway, Janet

2014-01-01

219

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

PubMed

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. PMID:25307219

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

2014-01-01

220

A Model Framework to Estimate Impact and Cost of Genetics-Based Sterile Insect Methods for Dengue Vector Control  

PubMed Central

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. PMID:21998654

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

2011-01-01

221

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

PubMed Central

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

2012-01-01

222

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

NASA Technical Reports Server (NTRS)

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.

Stoneking, Eric; Lebsock, Ken

2008-01-01

223

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

NASA Technical Reports Server (NTRS)

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.

Stoneking, Eric; Lebsock, Ken

2008-01-01

224

High-throughput sorting of mosquito larvae for laboratory studies and for future vector control interventions  

PubMed Central

Background Mosquito transgenesis offers new promises for the genetic control of vector-borne infectious diseases such as malaria and dengue fever. Genetic control strategies require the release of large number of male mosquitoes into field populations, whether they are based on the use of sterile males (sterile insect technique, SIT) or on introducing genetic traits conferring refractoriness to disease transmission (population replacement). However, the current absence of high-throughput techniques for sorting different mosquito populations impairs the application of these control measures. Methods A method was developed to generate large mosquito populations of the desired sex and genotype. This method combines flow cytometry and the use of Anopheles gambiae transgenic lines that differentially express fluorescent markers in males and females. Results Fluorescence-assisted sorting allowed single-step isolation of homozygous transgenic mosquitoes from a mixed population. This method was also used to select wild-type males only with high efficiency and accuracy, a highly desirable tool for genetic control strategies where the release of transgenic individuals may be problematic. Importantly, sorted males showed normal mating ability compared to their unsorted brothers. Conclusions The developed method will greatly facilitate both laboratory studies of mosquito vectorial capacity requiring high-throughput approaches and future field interventions in the fight against infectious disease vectors. PMID:22929810

2012-01-01

225

Human African Trypanosomiasis in South Sudan: How Can We Prevent a New Epidemic?  

PubMed Central

Human African trypanosomiasis (HAT) has been a major public health problem in South Sudan for the last century. Recurrent outbreaks with a repetitive pattern of responding-scaling down activities have been observed. Control measures for outbreak response were reduced when the prevalence decreased and/or socio-political crisis erupted, leading to a new increase in the number of cases. This paper aims to raise international awareness of the threat of another outbreak of sleeping sickness in South Sudan. It is a review of the available data, interventions over time, and current reports on the status of HAT in South Sudan. Since 2006, control interventions and treatments providing services for sleeping sickness have been reduced. Access to HAT diagnosis and treatment has been considerably diminished. The current status of control activities for HAT in South Sudan could lead to a new outbreak of the disease unless 1) the remaining competent personnel are used to train younger staff to resume surveillance and treatment in the centers where HAT activities have stopped, and 2) control of HAT continues to be given priority even when the number of cases has been substantially reduced. Failure to implement an effective and sustainable system for HAT control and surveillance will increase the risk of a new epidemic. That would cause considerable suffering for the affected population and would be an impediment to the socioeconomic development of South Sudan. PMID:22666506

Ruiz-Postigo, José A.; Franco, José R.; Lado, Mounir; Simarro, Pere P.

2012-01-01

226

Pastoral Livelihoods and the Epidemiology of Emergent Trypanosomiasis on the Jos Plateau, Nigeria   

E-print Network

African trypanosomiasis is a widespread disease of livestock which is a major constraint to livestock production, mixed farming and the rural economy. The Jos Plateau in Nigeria was historically free of tsetse flies and ...

Majekodunmi, Ayodele

2012-01-01

227

Pastoral livelihoods and the epidemiology of emergent trypanosomiasis on the Jos Plateau, Nigeria   

E-print Network

African trypanosomiasis is a widespread disease of livestock which is a major constraint to livestock production, mixed farming and the rural economy. The Jos Plateau in Nigeria was historically free of tsetse flies and ...

Majekodunmi, Ayodele Oluwakemi

2012-06-22

228

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...

229

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

SciTech Connect

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.

Miltiadis Alamaniotis; Vivek Agarwal

2014-10-01

230

Kynurenine pathway inhibition reduces central nervous system inflammation in a model of human African trypanosomiasis  

Microsoft Academic Search

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

Jean Rodgers; Trevor W. Stone; Michael P. Barrett; Barbara Bradley; Peter G. E. Kennedy

2009-01-01

231

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

PubMed Central

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 was found in Zindarou. Conclusion With a high abundance of neem plants in many villages in this area, the results of this study suggest that larval control using neem seed powder offers a sustainable additional tool for malaria vector control in the Sahel region of Niger. PMID:18651964

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

2008-01-01

232

A Pulsewidth Modulated Control of Induction Motor Drive Using Multilevel 12-Sided Polygonal Voltage Space Vectors  

Microsoft Academic Search

In this paper, a novel 12-sided polygonal space vector structure is proposed for an induction motor drive. The space vector pattern presented in this paper consists of two 12-sided concentric polygons with the outer polygon having a radius double the inner one. As compared to previously reported 12-sided polygonal space vector structures, this paper subdivides the space vector plane into

Anandarup Das; K. Sivakumar; Rijil Ramchand; Chintan Patel; K. Gopakumar

2009-01-01

233

Modelling the impact of vector control interventions on Anopheles gambiae population dynamics  

PubMed Central

Background Intensive anti-malaria campaigns targeting the Anopheles population have demonstrated substantial reductions in adult mosquito density. Understanding the population dynamics of Anopheles mosquitoes throughout their whole lifecycle is important to assess the likely impact of vector control interventions alone and in combination as well as to aid the design of novel interventions. Methods An ecological model of Anopheles gambiae sensu lato populations incorporating a rainfall-dependent carrying capacity and density-dependent regulation of mosquito larvae in breeding sites is developed. The model is fitted to adult mosquito catch and rainfall data from 8 villages in the Garki District of Nigeria (the 'Garki Project') using Bayesian Markov Chain Monte Carlo methods and prior estimates of parameters derived from the literature. The model is used to compare the impact of vector control interventions directed against adult mosquito stages - long-lasting insecticide treated nets (LLIN), indoor residual spraying (IRS) - and directed against aquatic mosquito stages, alone and in combination on adult mosquito density. Results A model in which density-dependent regulation occurs in the larval stages via a linear association between larval density and larval death rates provided a good fit to seasonal adult mosquito catches. The effective mosquito reproduction number in the presence of density-dependent regulation is dependent on seasonal rainfall patterns and peaks at the start of the rainy season. In addition to killing adult mosquitoes during the extrinsic incubation period, LLINs and IRS also result in less eggs being oviposited in breeding sites leading to further reductions in adult mosquito density. Combining interventions such as the application of larvicidal or pupacidal agents that target the aquatic stages of the mosquito lifecycle with LLINs or IRS can lead to substantial reductions in adult mosquito density. Conclusions Density-dependent regulation of anopheline larvae in breeding sites ensures robust, stable mosquito populations that can persist in the face of intensive vector control interventions. Selecting combinations of interventions that target different stages in the vector's lifecycle will result in maximum reductions in mosquito density. PMID:21798055

2011-01-01

234

Insecticide Resistance and Malaria Vector Control: The Importance of Fitness Cost Mechanisms in Determining Economically Optimal Control Trajectories  

PubMed Central

The evolutionary dynamics of insecticide resistance in harmful arthropods has economic implications, not only for the control of agricultural pests (as has been well studied), but also for the control of disease vectors, such as malaria-transmitting Anopheles mosquitoes. Previous economic work on insecticide resistance illustrates the policy relevance of knowing whether insecticide resistance mutations involve fitness costs. Using a theoretical model, this article investigates economically optimal strategies for controlling malaria-transmitting mosquitoes when there is the potential for mosquitoes to evolve resistance to insecticides. Consistent with previous literature, we find that fitness costs are a key element in the computation of economically optimal resistance management strategies. Additionally, our models indicate that different biological mechanisms underlying these fitness costs (e.g., increased adult mortality and/or decreased fecundity) can significantly alter economically optimal resistance management strategies. PMID:23448053

Brown, Zachary S.; Dickinson, Katherine L.; Kramer, Randall A.

2014-01-01

235

Benefit of Insecticide-Treated Nets, Curtains and Screening on Vector Borne Diseases, Excluding Malaria: A Systematic Review and Meta-analysis  

PubMed Central

Introduction Insecticide-treated nets (ITNs) are one of the main interventions used for malaria control. However, these nets may also be effective against other vector borne diseases (VBDs). We conducted a systematic review and meta-analysis to estimate the efficacy of ITNs, insecticide-treated curtains (ITCs) and insecticide-treated house screening (ITS) against Chagas disease, cutaneous and visceral leishmaniasis, dengue, human African trypanosomiasis, Japanese encephalitis, lymphatic filariasis and onchocerciasis. Methods MEDLINE, EMBASE, LILACS and Tropical Disease Bulletin databases were searched using intervention, vector- and disease-specific search terms. Cluster or individually randomised controlled trials, non-randomised trials with pre- and post-intervention data and rotational design studies were included. Analysis assessed the efficacy of ITNs, ITCs or ITS versus no intervention. Meta-analysis of clinical data was performed and percentage reduction in vector density calculated. Results Twenty-one studies were identified which met the inclusion criteria. Meta-analysis of clinical data could only be performed for four cutaneous leishmaniasis studies which together showed a protective efficacy of ITNs of 77% (95%CI: 39%–91%). Studies of ITC and ITS against cutaneous leishmaniasis also reported significant reductions in disease incidence. Single studies reported a high protective efficacy of ITS against dengue and ITNs against Japanese encephalitis. No studies of Chagas disease, human African trypanosomiasis or onchocerciasis were identified. Conclusion There are likely to be considerable collateral benefits of ITN roll out on cutaneous leishmaniasis where this disease is co-endemic with malaria. Due to the low number of studies identified, issues with reporting of entomological outcomes, and few studies reporting clinical outcomes, it is difficult to make strong conclusions on the effect of ITNs, ITCs or ITS on other VBDs and therefore further studies be conducted. Nonetheless, it is clear that insecticide-treated materials such as ITNs have the potential to reduce pathogen transmission and morbidity from VBDs where vectors enter houses. PMID:25299481

Wilson, Anne L.; Dhiman, Ramesh C.; Kitron, Uriel; Scott, Thomas W.; van den Berg, Henk; Lindsay, Steven W.

2014-01-01

236

Nanobody conjugated PLGA nanoparticles for active targeting of African Trypanosomiasis.  

PubMed

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. PMID:25445702

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

237

Comparison of Vector Competence of Aedes mediovittatus and Aedes aegypti for Dengue Virus: Implications for Dengue Control in the Caribbean  

PubMed Central

Background Aedes mediovittatus mosquitoes are found throughout the Greater Antilles in the Caribbean and often share the same larval habitats with Ae. Aegypti, the primary vector for dengue virus (DENV). Implementation of vector control measures to control dengue that specifically target Ae. Aegypti may not control DENV transmission in Puerto Rico (PR). Even if Ae. Aegypti is eliminated or DENV refractory mosquitoes are released, DENV transmission may not cease when other competent mosquito species like Ae. Mediovittatus are present. To compare vector competence of Ae. Mediovittatus and Ae. Aegypti mosquitoes, we studied relative infection and transmission rates for all four DENV serotypes. Methods To compare the vector competence of Ae. Mediovittatus and Ae. Aegypti, mosquitoes were exposed to DENV 1–4 per os at viral titers of 5–6 logs plaque-forming unit (pfu) equivalents. At 14 days post infectious bloodmeal, viral RNA was extracted and tested by qRT-PCR to determine infection and transmission rates. Infection and transmission rates were analyzed with a generalized linear model assuming a binomial distribution. Results Ae. Aegypti had significantly higher DENV-4 infection and transmission rates than Ae. mediovittatus. Conclusions This study determined that Ae. Mediovittatus is a competent DENV vector. Therefore dengue prevention programs in PR and the Caribbean should consider both Ae. Mediovittatus and Ae. Aegypti mosquitoes in their vector control programs. PMID:25658951

Poole-Smith, B. Katherine; Hemme, Ryan R.; Delorey, Mark; Felix, Gilberto; Gonzalez, Andrea L.; Amador, Manuel; Hunsperger, Elizabeth A.; Barrera, Roberto

2015-01-01

238

Trial of a minimal-risk botanical compound to control the vector tick of Lyme disease.  

PubMed

We compared the application of IC2, a minimal-risk (25B) botanical compound containing 10% rosemary oil, with bifenthrin, a commonly used synthetic compound, and with water for the control of Ixodes scapularis Say (= Ixodes dammini Spielman, Clifford, Piesman & Corwin), on tick-infested grids in Maine, in an area where Lyme disease is established and other tick-borne diseases are emerging. High-pressure sprays of IC2, bifenthrin, and water were applied during the peak nymphal (July) and adult (October) seasons of the vector tick. No ticks could be dragged on the IC2 grids within 2 wk of the July spray, and few adult ticks were found in October or the following April. Similarly, no adult ticks could be dragged 1.5 wk after the October IC2 spray, and few the following April. No ticks were found on the bifenthrin grids after either spray through the following April, whereas substantial numbers of ticks remained throughout on the grids sprayed with water. Thus, IC2 appears to be an effective, minimum-risk acaricide to control the vector tick of Lyme disease. PMID:20695287

Rand, Peter W; Lacombe, Eleanor H; Elias, Susan P; Lubelczyk, Charles B; St Amand, Theodore; Smith, Robert P

2010-07-01

239

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

Microsoft Academic Search

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

Hajime Hida; Yoshio Tomigashi; Keiji Kishimoto

2007-01-01

240

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

PubMed Central

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 demonstrated the antagonistic effect of PBO. Conclusion Laboratory studies with susceptible and resistant strains of An. culicifacies and An. stephensi, coupled with limited field studies with multiple insecticide-resistant An. culicifacies have shown that chlorfenapyr can be a suitable insecticide for malaria vector control, in multiple-insecticide-resistant mosquitoes especially in areas with pyrethroid resistant mosquitoes. PMID:21266037

2011-01-01

241

Optimization of Control Strategies for Non-Domiciliated Triatoma dimidiata, Chagas Disease Vector in the Yucatán Peninsula, Mexico  

PubMed Central

Background Chagas disease is the most important vector-borne disease in Latin America. Regional initiatives based on residual insecticide spraying have successfully controlled domiciliated vectors in many regions. Non-domiciliated vectors remain responsible for a significant transmission risk, and their control is now a key challenge for disease control. Methodology/Principal Findings A mathematical model was developed to predict the temporal variations in abundance of non-domiciliated vectors inside houses. Demographic parameters were estimated by fitting the model to two years of field data from the Yucatan peninsula, Mexico. The predictive value of the model was tested on an independent data set before simulations examined the efficacy of control strategies based on residual insecticide spraying, insect screens, and bednets. The model accurately fitted and predicted field data in the absence and presence of insecticide spraying. Pyrethroid spraying was found effective when 50 mg/m2 were applied yearly within a two-month period matching the immigration season. The >80% reduction in bug abundance was not improved by larger doses or more frequent interventions, and it decreased drastically for different timing and lower frequencies of intervention. Alternatively, the use of insect screens consistently reduced bug abundance proportionally to the reduction of the vector immigration rate. Conclusion/Significance Control of non-domiciliated vectors can hardly be achieved by insecticide spraying, because it would require yearly application and an accurate understanding of the temporal pattern of immigration. Insect screens appear to offer an effective and sustainable alternative, which may be part of multi-disease interventions for the integrated control of neglected vector-borne diseases. PMID:19365542

Barbu, Corentin; Dumonteil, Eric; Gourbière, Sébastien

2009-01-01

242

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

PubMed Central

Background Malaria is endemic with year-round transmission on Bioko Island. The Bioko Island Malaria Control Project (BIMCP) started in 2004 with the aim to reduce malaria transmission and to ultimately eliminate malaria. While the project has been successful in reducing overall malaria morbidity and mortality, foci of high malaria transmission still persist on the island. Results from the 2009 entomological collections are reported here. Methods Human landing collections (HLC) and light trap collections (LTC) were carried out on Bioko Island, Equatorial Guinea in 2009. The HLCs were performed in three locations every second month and LTCs were carried out in 10 locations every second week. Molecular analyses were performed to identify species, detect sporozoites, and identify potential insecticide resistance alleles. Results The entomological inoculation rates (EIR) on Bioko Island ranged from 163 to 840, with the outdoor EIRs reaching > 900 infective mosquito bites per year. All three human landing collection sites on Bioko Island had an annual EIR exceeding the calculated African average of 121 infective bites per year. The highest recorded EIRs were in Punta Europa in northwestern Bioko Island with human biting rates of 92 and 66 mosquito landings per person per night, outdoors and indoors, respectively. Overall, the propensity for mosquito biting on the island was significantly higher outdoors than indoors (p < 0.001). Both Anopheles gambiae s.s. and An. melas were responsible for malaria transmission on the island, but with different geographical distribution patterns. Sporozoite rates were the highest in An. gambiae s.s. populations ranging from 3.1% in Punta Europa and 5.7% in Riaba in the southeast. Only the L1014F (kdr-west) insecticide resistance mutation was detected on the island with frequencies ranging from 22-88% in An. gambiae s.s. No insecticide resistance alleles were detected in the An. melas populations. Conclusions In spite of five years of 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

2012-01-01

243

Thrust-vector control of a three-axis stabilized upper-stage rocket with fuel slosh dynamics  

NASA Astrophysics Data System (ADS)

This paper studies the thrust vector control problem for an upper-stage rocket with fuel slosh dynamics. The dynamics of a three-axis stabilized spacecraft with a single partially-filled fuel tank are formulated and the sloshing propellant is modeled as a multi-mass-spring system, where the oscillation frequencies of the mass-spring elements represent the prominent sloshing modes. The equations of motion are expressed in terms of the three-dimensional spacecraft translational velocity vector, the attitude, the angular velocity, and the internal coordinates representing the slosh modes. A Lyapunov-based nonlinear feedback control law is proposed to control the translational velocity vector and the attitude of the spacecraft, while attenuating the sloshing modes characterizing the internal dynamics. A simulation example is included to illustrate the effectiveness of the control law.

Rubio Hervas, Jaime; Reyhanoglu, Mahmut

2014-05-01

244

Online Computation of Hysteresis Boundary for Constant Switching Frequency Current-Error Space-Vector-Based Hysteresis Controller for VSI-Fed IM Drives  

Microsoft Academic Search

This paper proposes a current-error space-vector-based hysteresis controller with online computation of boundary for two-level inverter-fed induction motor (IM) drives. The proposed hysteresis controller has got all advantages of conventional current-error space-vector-based hysteresis controllers like quick transient response, simplicity, adjacent voltage vector switching, etc. Major advantage of the proposed controller-based voltage-source-inverters-fed drive is that phase voltage frequency spectrum produced is

Rijil Ramchand; K. Gopakumar; Chintan Patel; K. Sivakumar; Anandarup Das; Haitham Abu-Rub

2012-01-01

245

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

PubMed Central

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

Gürtler, Ricardo E.; Yadon, Zaida E.

2015-01-01

246

Vector field approximation: a computational paradigm for motor control and learning.  

PubMed

Recent experiments in the spinalized frog (Bizzi et al. 1991) have shown that focal microstimulation of a site in the premotor layers in the lumbar grey matter of the spinal cord results in a field of forces acting on the frog's ankle and converging to a single equilibrium position. These experiments suggested that the neural circuits in the spinal cord are organized in a set of control modules that "store" a few limb postures in the form of convergent force fields acting on the limb's end-point. Here, we investigate how such postural modules can be combined by the central nervous system for generating and representing a wider repertoire of control patterns. Our work is related to some recent investigations by Poggio and Girosi (1990a, b) who have proposed to represent the task of learning scalar maps as a problem of surface approximation. Consistent both with this view and with our experimental findings in the spinal frog, we regard the issue of generating motor repertoires as a problem of vector-field approximation. To this end, we characterize the output of a control module as a "basis field" (Mussa-Ivaldi 1992), that is as the vectorial equivalent of a basis function. Our theoretical findings indicate that by combining basis fields, the central nervous system may achieve a number of goals such as (1) the generation of a wide repertoire of control patterns and (2) the representation of these control patterns with a set of coefficients that are invariant under coordinate transformations. PMID:1472573

Mussa-Ivaldi, F A; Giszter, S F

1992-01-01

247

Control strategies for power smoothing using a flywheel driven by a sensorless vector-controlled induction machine operating in a wide speed range  

Microsoft Academic Search

This paper presents a novel control strategy for power smoothing. The system is based on a sensorless vector-controlled induction machine driving a flywheel. The problem of regulating the DC-link voltage against input power surges or sudden changes in load demand is addressed. The induction machine is controlled to operate in a wide speed range by using flux weakening above rated

Roberto Cárdenas; Rubén Peña; Greg M. Asher; Jon Clare; Ramón Blasco-Giménez

2004-01-01

248

Genetically Modifying the Insect Gut Microbiota to Control Chagas Disease Vectors through Systemic RNAi.  

PubMed

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 × 107 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. PMID:25675102

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

249

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

PubMed Central

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

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

250

Identification of critical infection parameters to control helper-dependent adenoviral vector production.  

PubMed

Helper-dependent adenoviral vectors (HDVs) are the most promising adenoviral vectors for gene therapy treatments as well as vaccination strategies. However, the lack of a robust and efficient strategy to produce the HDV at high titers constitutes a major obstacle hindering the use of this promising technology at the clinical level. The HDV production requires a double infection of a recombinase-expressing HEK293 cell line with the HDV and a helper virus (HV). To limit the contamination of viral HDV lots by HV, encapsidation of HV is prevented by the recombinase action. A real-time quantitative PCR assay was developed to accurately characterize the contamination of the final product by HV. Infection strategies to enhance the HDV yield and reduce the contamination by HV were investigated. The multiplicity of infection (MOI) was identified as a critical parameter to simultaneously improve the HDV yield and reduce the contamination by HV. HDV-to-HV MOI ratio dictated the HDV yield whereas the HV accumulation was controlled by the MOI of HV. Delaying infection with the HV did not improve the HDV yield. PMID:19501266

Dormond, E; Perrier, M; Kamen, A

2009-06-15

251

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

252

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

NASA Technical Reports Server (NTRS)

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.

Millard, Jon

2014-01-01

253

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

NASA Technical Reports Server (NTRS)

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.

Deere, Karen A.

1998-01-01

254

Biology and control of Taeniorhynchus (Mansonioides) uniformis Theobald, the chief vector of rural filariasis in Ceylon  

PubMed Central

Residual spraying of DDT for the control of Taeniorhynchus (Mansonioides) uniformis, the mosquito vector of rural filariasis in Ceylon, was carried out in Induruwa, a village on the west coast of the island. The results showed that the insecticide retained its effectiveness for a period of 4-6 months. During the course of this investigation, various observations were made on the behaviour of T. (M.) uniformis. Its host plants, day-time resting-places, feeding habits, and response to light—particularly moonlight—were recorded. An increase in T. (M.) uniformis prevalence was observed to coincide with the onset of the north-east and south-west monsoons, when the paddy-fields are inundated and become overgrown with Isachne australis, the most common aquatic plant in the area and a favourite breeding-place of this mosquito species. PMID:13585075

Antonipulle, P.; David, H. V.; Karunaratne, M. D. R.

1958-01-01

255

Evaluation of Nucleoside Hydrolase Inhibitors for Treatment of African Trypanosomiasis ? †  

PubMed Central

In this paper, we present the biochemical and biological evaluation of N-arylmethyl-substituted iminoribitol derivatives as potential chemotherapeutic agents against trypanosomiasis. Previously, a library of 52 compounds was designed and synthesized as potent and selective inhibitors of Trypanosoma vivax inosine-adenosine-guanosine nucleoside hydrolase (IAG-NH). However, when the compounds were tested against bloodstream-form Trypanosoma brucei brucei, only one inhibitor, N-(9-deaza-adenin-9-yl)methyl-1,4-dideoxy-1,4-imino-d-ribitol (UAMC-00363), displayed significant activity (mean 50% inhibitory concentration [IC50] ± standard error, 0.49 ± 0.31 ?M). Validation in an in vivo model of African trypanosomiasis showed promising results for this compound. Several experiments were performed to investigate why only UAMC-00363 showed antiparasitic activity. First, the compound library was screened against T. b. brucei IAG-NH and inosine-guanosine nucleoside hydrolase (IG-NH) to confirm the previously demonstrated inhibitory effects of the compounds on T. vivax IAG-NH. Second, to verify the uptake of these compounds by T. b. brucei, their affinities for the nucleoside P1 and nucleoside/nucleobase P2 transporters of T. b. brucei were tested. Only UAMC-00363 displayed significant affinity for the P2 transporter. It was also shown that UAMC-00363 is concentrated in the cell via at least one additional transporter, since P2 knockout mutants of T. b. brucei displayed no resistance to the compound. Consequently, no cross-resistance to the diamidine or the melaminophenyl arsenical classes of trypanocides is expected. Third, three enzymes of the purine salvage pathway of procyclic T. b. brucei (IAG-NH, IG-NH, and methylthioadenosine phosphorylase [MTAP]) were investigated using RNA interference. The findings from all these studies showed that it is probably not sufficient to target only the nucleoside hydrolase activity to block the purine salvage pathway of T. b. brucei and that, therefore, it is possible that UAMC-00363 acts on an additional target. PMID:20194690

Berg, Maya; Kohl, Linda; Van der Veken, Pieter; Joossens, Jurgen; Al-Salabi, Mohammed I.; Castagna, Valeria; Giannese, Francesca; Cos, Paul; Versées, Wim; Steyaert, Jan; Grellier, Philippe; Haemers, Achiel; Degano, Massimo; Maes, Louis; de Koning, Harry P.; Augustyns, Koen

2010-01-01

256

Iterative reconstruction of volumetric modulated arc radiotherapy plans using control point basis vectors  

NASA Astrophysics Data System (ADS)

Volumetric Modulated Arc Radiotherapy is an innovative technique currently utilized to efficiently deliver complex treatments. Dose rate, speed of rotation, and field shape are continuously varied as the radiation source rotates about the patient. Patient specific quality assurance is performed to verify that the delivered dose distribution is consistent with the plan formulated in a treatment planning system. The purpose of this work is to present novel methodology using a Gafchromic EBT3 film image of a patient plan in a cylindrical phantom and calculating the delivered MU per control point. Images of two dimensional plan dose matrices and film scans are analyzed using MATLAB with the imaging toolbox. Dose profiles in a ring corresponding to the film position are extracted from the plan matrices for comparison with the corresponding measured film dose. The plan is made up of a series of individual static Control Points. If we consider these Control Points a set of basis vectors, then variations in the plan can be represented as the weighted sum of the basis. The weighing coefficients representing the actual delivered MU can be determined by any available optimization tool, such as downhill simplex or non-linear programming. In essence we reconstruct an image of the delivered dose. Clinical quality assurance is performed with this technique by computing a patient plan with the measured monitor units and standard plan evaluation tools such as Dose Volume Histograms. Testing of the algorithm with known changes in the reference images indicated a correlation coefficient greater than 0.99.

Barbiere, Joseph C.; Kapulsky, Alexander; Ndlovu, Alois

2014-03-01

257

Electrospun nanofibrous scaffolds for controlled release of adeno-associated viral vectors.  

PubMed

The integration of viral gene delivery with key features of biomaterial scaffolds that modulate viral delivery in a controlled manner offers a promising strategy for numerous tissue engineering applications. In this study adeno-associated virus (AAV), which is widely utilized in human gene therapy as a gene carrier due to its safety and efficient gene delivery capability, was encapsulated within electrospun nanofibrous scaffolds composed of blended mixtures of elastin-like polypeptides (ELP) and poly (?-caprolactone) (PCL) and was employed to transduce fibroblasts adherent on the scaffolds. Combinatorial interactions between ELP and PCL chains upon physical blending significantly altered the mechanical properties (i.e. wettability, elastic modulus, strain, etc.) of the ELP/PCL composites, thus providing key tools to mediate controlled release of AAV vectors and robust cellular transduction on the fibrous scaffolds. The ability of ELP/PCL composites to manipulate the controlled release of AAV-mediated gene delivery for subsequent high-efficiency cellular transduction will provide tremendous opportunities for a variety of tissue engineering applications. PMID:21745607

Lee, Slgirim; Kim, Jung-Suk; Chu, Hun Su; Kim, Go-Woon; Won, Jong-In; Jang, Jae-Hyung

2011-11-01

258

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

PubMed

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 diseases. PMID:21432748

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

2011-04-01

259

Hepatic microsomal alterations during chronic trypanosomiasis in the field vole, Microtus montanus.  

PubMed

The field vole, Microtus montanus, was used as a model system to evaluate the chronic effects of infection by Trypanosoma brucei gambiense on hepatic mixed-function oxidase activity. At day 28 post inoculation there was a 97% increase in liver wet weight per g body weight. A portion of the increase (21%) was accounted for by tissue edema which occurred after day 14 of infection. Total hepatic cytochrome P-450 content and related total tissue mixed-function oxidase activities were decreased to about 60% of control levels at day 28 post inoculation. The decrease in total tissue mixed-function oxidase activity was partly due to a small decrease in microsomal protein per cell, and partly to a large decrease in cytochrome P-450 concentration in the endoplasmic reticulum. Although the decrease in total liver monooxygenase activity in several substrates roughly paralleled the loss in cytochrome P-450 content, several other microsomal enzyme markers not related to cytochrome P-450 monooxygenation were elevated in proportion to total liver microsomal protein content. The results suggest that in M. montanus during trypanosomiasis, there is proliferation of hepatic cells with normal content of endoplasmic reticulum. Furthermore, there appears to be selective toxicity for hepatic cytochrome P-450 and related monooxygenase activities. This may compromise the animals' ability to metabolize and dispose of other drugs to which the animal may be exposed in the course of infection. PMID:7050701

Shertzer, H G; Hall, J E; Seed, J R

1982-07-01

260

Proposed use of spatial mortality assessments as part of the pesticide evaluation scheme for vector control  

PubMed Central

Background The WHO Pesticide Evaluation Scheme to evaluate the efficacy of insecticides does not include the testing of a lethal effect at a distance. A tool was developed to evaluate the spatial mortality of an insecticide product against adult mosquitoes at a distance under laboratory and field conditions. Operational implications are discussed. Methods Insecticide paint, Inesfly 5A IGR™, containing two organophosphates (OPs): chlorpyrifos and diazinon, and one insect growth regulator (IGR): pyriproxyfen, was the product tested. Laboratory tests were performed using “distance boxes” with surfaces treated with one layer of control or insecticide paint at a dose of 1 kg/6 sq m. Field tests were conducted up to 12 months in six experimental huts randomly allocated to control or one or two layers of insecticide paint at 1 kg/6 sq m. All distance tests were performed using reference-susceptible strains of Anopheles gambiae and Culex quinquefasciatus left overnight at a distance of 1 m from control or treated surfaces. Results After an overnight exposition at distances of 1 m, field and laboratory evaluations at 0 months after treatment (T0) yielded 100% mortality rates on surfaces treated with one layer at 1 kg/6 sq m against susceptible strains of An. gambiae and Cx. quinquefasciatus. Testing for long-term efficacy in the field gave mortality rates of 96-100% after an overnight exposition at a distance of 1 m for up to 12 months in huts where a larger volume was treated (walls and ceilings) with one or two layers of insecticide paint. Conclusion A comprehensive evaluation of the full profile of insecticide products, both upon contact and spatially, may help rationalize vector control efforts more efficiently. Treating a large enough volume may extend a product’s mortality efficacy in the long-term, which contact tests would fail to assess. It is hereby proposed to explore the development of cost effective methods to assess spatial mortality and to include them as one additional measurement of insecticide efficacy against mosquitoes and other arthropod vectors in WHOPES Phase I and Phase II studies. PMID:24139513

2013-01-01

261

Micro-counterimmunoelectrophoresis: a rapid screening technique for trypanosomiasis.  

PubMed

A rapid and economical micro-counterimmunoelectrophoresis (MCIE) test, for antibody to trypanosome antigens, has been developed which may prove useful in trypanosomiasis surveillance. MCIE was more sensitive and more rapid than immunodiffusion (ID). Serum samples from trypanosome-infected rabbits and cattle (Nigerian and Gambian), from Kuwaiti dogs and camels, from Ivory Coast sleeping sickness patients, from Brazilian patients with Chagas's disease, plus mouse-anti-malaria sera have been tested by MCIE with Trypanosoma brucei, T. vivax, T. congolense and T. cruzi antigens. A few of the rabbit and the mice sera were also tested against Trichomonas vaginalis, Entamoeba histolytica, Plasmodium berghei or P. chabaudi antigens. Whenever possible the MCIE results were compared with parasitological or other serological tests (ID; indirect fluorescent antibody test, IFAT; enzyme-linked immunosorbent assay, ELISA; complement fixation test, CFT or indirect haemagglutination test, IHAT). The MCIE test was not species specific but the homologous species reactions were more often positive than heterologous ones. Homologous species reactions, with rabbit sera, detected antibodies as early as 10 days after infection and developed more precipitin lines as the infection progressed. Trypanosomal antigens and antisera cross-reacted with those of other protozoa (E. histolytica, Tr. vaginalis, P. chabaudi, P. berghei, and Babesia sp. and Leishmania sp.) but such reactions required an antigen concentration 4 to 16 times greater than that required for homologous trypanosome reactions (a factor which might be exploited for identification of different species of trypanosome).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6415874

Taylor, A E; Smith, V

1983-01-01

262

Dyes, trypanosomiasis and DNA: a historical and critical review.  

PubMed

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. PMID:21080764

Wainwright, M

2010-12-01

263

Human African trypanosomiasis in endemic populations and travellers.  

PubMed

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. PMID:21901632

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

2012-06-01

264

Monitoring the aquatic toxicity of mosquito vector control spray pesticides to freshwater receiving waters.  

PubMed

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. Toxicity testing can provide useful risk information about unidentified, unmeasured toxicants or mixtures of toxicants. In this case, toxicity testing provided information that could lead to the inclusion of dichlorvos monitoring as a permit requirement. PMID:24659580

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

265

Influence of stimuli colour in SSVEP-based BCI wheelchair control using support vector machines.  

PubMed

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. PMID:24533888

Singla, Rajesh; Khosla, Arun; Jha, Rameshwar

2014-04-01

266

Sustainable vector control and management of Chagas disease in the Gran Chaco, Argentina  

PubMed Central

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

Gürtler, Ricardo E.; Kitron, Uriel; Cecere, M. Carla; Segura, Elsa L.; Cohen, Joel E.

2007-01-01

267

Proteomic Selection of Immunodiagnostic Antigens for Human African Trypanosomiasis and Generation of a Prototype Lateral Flow Immunodiagnostic Device  

PubMed Central

Background The diagnosis of Human African Trypanosomiasis relies mainly on the Card Agglutination Test for Trypanosomiasis (CATT). While this test is successful, it is acknowledged that there may be room for improvement. Our aim was to develop a prototype lateral flow test based on the detection of antibodies to trypanosome antigens. Methodology/Principal Findings We took a non-biased approach to identify potential immunodiagnostic parasite protein antigens. The IgG fractions from the sera from Trypanosoma brucei gambiense infected and control patients were isolated using protein-G affinity chromatography and then immobilized on Sepharose beads. The IgG-beads were incubated with detergent lysates of trypanosomes and those proteins that bound were identified by mass spectrometry-based proteomic methods. This approach provided a list of twenty-four trypanosome proteins that selectively bound to the infection IgG fraction and that might, therefore, be considered as immunodiagnostic antigens. We selected four antigens from this list (ISG64, ISG65, ISG75 and GRESAG4) and performed protein expression trials in E. coli with twelve constructs. Seven soluble recombinant protein products (three for ISG64, two for ISG65 and one each for ISG75 and GRESAG4) were obtained and assessed for their immunodiagnostic potential by ELISA using individual and/or pooled patient sera. The ISG65 and ISG64 construct ELISAs performed well with respect to detecting T. b. gambiense infections, though less well for detecting T. b. rhodesiense infections, and the best performing ISG65 construct was used to develop a prototype lateral flow diagnostic device. Conclusions/Significance Using a panel of eighty randomized T. b. gambiense infection and control sera, the prototype showed reasonable sensitivity (88%) and specificity (93%) using visual readout in detecting T. b. gambiense infections. These results provide encouragement to further develop and optimize the lateral flow device for clinical use. PMID:23469310

Sullivan, Lauren; Wall, Steven J.; Carrington, Mark; Ferguson, Michael A. J.

2013-01-01

268

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...

269

Feasibility of both vector control and displacement factor correction by voltage source type AC-AC matrix converter  

Microsoft Academic Search

This paper shows that by transforming both sides of the matrix converter to the d-q-o frames of their respective frequencies, there is significant simplification in the transformation matrix which enables the network of one side to be integrated to the other. Thus, it is possible to design for operation with field vector control on the motor side and unity displacement

Mehrdad Kazerani; Boon-Teck Ooi

1995-01-01

270

Linear Test Bed. Volume 2: Test Bed No. 2. [linear aerospike test bed for thrust vector control  

NASA Technical Reports Server (NTRS)

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.

1974-01-01

271

Evaluation of the effectiveness of malaria vector control measures in urban settings of Dakar by a specific anopheles salivary biomarker.  

PubMed

Standard entomological methods for evaluating the impact of vector control lack sensitivity in low-malaria-risk areas. The detection of human IgG specific to Anopheles gSG6-P1 salivary antigen reflects a direct measure of human-vector contact. This study aimed to assess the effectiveness of a range of vector control measures (VCMs) in urban settings by using this biomarker approach. The study was conducted from October to December 2008 on 2,774 residents of 45 districts of urban Dakar. IgG responses to gSG6-P1 and the use of malaria VCMs highly varied between districts. At the district level, specific IgG levels significantly increased with age and decreased with season and with VCM use. The use of insecticide-treated nets, by drastically reducing specific IgG levels, was by far the most efficient VCM regardless of age, season or exposure level to mosquito bites. The use of spray bombs was also associated with a significant reduction of specific IgG levels, whereas the use of mosquito coils or electric fans/air conditioning did not show a significant effect. Human IgG response to gSG6-P1 as biomarker of vector exposure represents a reliable alternative for accurately assessing the effectiveness of malaria VCM in low-malaria-risk areas. This biomarker tool could be especially relevant for malaria control monitoring and surveillance programmes in low-exposure/low-transmission settings. PMID:23840448

Drame, Papa Makhtar; Diallo, Abdoulaye; Poinsignon, Anne; Boussari, Olayide; Dos Santos, Stephanie; Machault, Vanessa; Lalou, Richard; Cornelie, Sylvie; LeHesran, Jean-Yves; Remoue, Franck

2013-01-01

272

Control strategies for enhanced power smoothing in wind energy systems using a flywheel driven by a vector-controlled induction machine  

Microsoft Academic Search

This paper presents a novel control strategy for power smoothing in wind energy applications, especially those feeding a stand-alone load. The system is based on a vector-controlled induction machine driving a flywheel and addresses the problem of regulating the DC-link system voltage against both input power surges\\/sags from a wind turbine or sudden changes in load demand. The control is

Roberto Cárdenas; Rubén Peña; Greg Asher; Jon Clare

2001-01-01

273

Control of tripod-scheme cold-atom wavepackets by manipulating a non-Abelian vector potential  

SciTech Connect

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.

Zhang Qi, E-mail: cqtzq@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Gong Jiangbin, E-mail: phygj@nus.edu.s [Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, 117542 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, Singapore 117597 (Singapore); Oh, C.H., E-mail: phyohch@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Institute of Advanced Studies, Nanyang Technological University, Singapore 639798 (Singapore)

2010-06-15

274

Independent Orbiter Assessment (IOA): Assessment of the ascent thrust vector control actuator subsystem FMEA/CIL  

NASA Technical Reports Server (NTRS)

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.

Wilson, R. E.

1988-01-01

275

Tsetse Fly Control in Kenya's Spatially and Temporally Dynamic Control Reservoirs: A Cost Analysis  

PubMed Central

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

McCord, Paul F.; Messina, Joseph P.; Campbell, David J.; Grady, Sue C.

2011-01-01

276

House-scale evaluation of bifenthrin indoor residual spraying for malaria vector control in India.  

PubMed

In an area of India where the main rural malaria vector, Anopheles culicifacies Giles, has developed triple resistance to DDT, HCH, and malathion sprayed indoors in antimalaria program, bifenthrin (10% wettable powder) was evaluated in a randomized house-scale trial between July 1999 and March 2000. Entomological impact of four serial doses of bifenthrin (25, 50, 100, and 200 mg/m2) sprayed in rooms in five villages was compared with malathion (2 g/m2) and unsprayed control. An. culicifacies was 100% susceptible to bifenthrin (0.1%), but only 57% to malathion (5%) test papers. Contact bioassays were carried out on sprayed surfaces for 24 wk, and 24 h mortality in An. culicifacies was recorded. Bifenthrin 100- and 200-mg doses caused > or = 80% mortality until 24 wk. The 50-mg dose caused > or = 80% mortality on tin, wood, and mud surfaces for 24 wk, and on brick walls for 16 wk. Bifenthrin 25-mg dose produced > or = 80% mortality for 24 wk on tin, 20 wk on mud walls, 16 wk on brick walls, and 8 wk on wood surfaces. Persistence of > or = 80% mortality did not differ for 25- and 50-mg doses on any surface except on wood (P < 0.05). Malathion sprayed in three rounds of 6 wk apart caused > or = 80% mortality for 16 wk on the brick and mud walls, and for 20 wk on the tin and wood surfaces. Bifenthrin 25- and 50-mg doses produced a similar impact on the densities of An. culicifacies and other mosquitoes but a superior one to malathion or control. Bifenthrin 25-mg dose caused least excitorepellency. Overall, efficacy of bifenthrin was superior to malathion. Considering the duration of the persistence of significant insecticidal action of bifenthrin on the most common surfaces (mud and brick walls), least excito-repellency and a relative impact on the mosquito densities, the 25-mg dose was the most superior among all the four doses evaluated. PMID:12597653

Yadav, Rajpal S; Srivastava, H C; Adak, T; Nanda, N; Thapar, B R; Pant, C S; Zaim, Morteza; Subbarao, Sarala K

2003-01-01

277

Simulation development and evaluation of an improved longitudinal velocity vector control wheel steering mode and electronic display format  

NASA Technical Reports Server (NTRS)

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.

Steinmetz, G. G.

1980-01-01

278

Application of eco-friendly tools and eco-bio-social strategies to control dengue vectors in urban and peri-urban settings in Thailand  

PubMed Central

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 programme was successfully implemented in urban and peri-urban settings in Thailand, through intersectoral collaboration and practical action at household level, with a significant reduction in vector densities. PMID:23318236

Kittayapong, Pattamaporn; Thongyuan, Suporn; Olanratmanee, Phanthip; Aumchareoun, Worawit; Koyadun, Surachart; Kittayapong, Rungrith; Butraporn, Piyarat

2012-01-01

279

Malaria Vector Species  

NSDL National Science Digital Library

A sub-page of the extremely informative VectorBase. This is a worldwide listing of malaria vectors divided into 12 geographic regions following the 1957 classic The Epidemiology and Control of Malaria by MacDonald.

0002-11-30

280

Risk factors for treatment failure after melarsoprol for Trypanosoma brucei gambiense trypanosomiasis in Uganda  

Microsoft Academic Search

We evaluated the treatment failure rate among late-stage human African trypanosomiasis (HAT) patients treated with melarsoprol in Arua, northern Uganda, between September 1995 and August 1996, and identified the risk factors for treatment failure. We conducted a retrospective cohort study in October 1998, and performed a survival analysis. A treatment failure was defined as a late-stage HAT patient fully treated

D. Legros; S. Evans; F. Maiso; J. C. K. Enyaru; D. Mbulamberi

1999-01-01

281

Indigenous knowledge system for treatment of trypanosomiasis in Kaduna state of Nigeria  

Microsoft Academic Search

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

S. E Atawodi; D. A Ameh; S Ibrahim; J. N Andrew; H. C Nzelibe; E. O Onyike; K. M Anigo; E. A Abu; D. B James; G. C Njoku; A. B Sallau

2002-01-01

282

HUMAN TRYPANOSOMIASIS CAUSED BY TRYPANOSOMA EVANSI IN INDIA: THE FIRST CASE REPORT  

Microsoft Academic Search

We report an Indian farmer who had fluctuating trypanosome parasitemia associated with febrile episodes for five months. Morphologic examination of the parasites indicated the presence of large numbers of trypanosomes belonging to the species Trypanosoma evansi, which is normally a causative agent of animal trypanosomiasis known as surra. Basic clinical and biologic examinations are described, using several assays, including parasitologic,

PRASHANT P. JOSHI; VIJAY R. SHEGOKAR; RAJARAM M. POWAR; STEPHANE HERDER; RAHUL KATTI; HARSHA R. SALKAR; VIBHAWARI S. DANI; ARADHANA BHARGAVA; JEAN JANNIN; PHILIPPE TRUC

283

Studies on the epidemiology of trypanosomiasis in sheep and goats in Kenya  

Microsoft Academic Search

The epidemiology of trypanosomiasis in a tsetse-infested range area of Kenya was studied for 2 years in various breeds of sheep and goats. Observations, including infection rates, PCV, temperature and weight loss indicated that the exotic breeds were more susceptible to natural trypanosomal infection than the indigenous breeds and that the infection may be severely debilitating and in many cases

L. Griffin; E. W. Allonby

1979-01-01

284

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

E-print Network

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 ...

Gianotti, Rebecca Louise

285

Potential for entomopathogenic fungi to control Triatoma dimidiata (Hemiptera: Reduviidae), a vector of Chagas disease in Mexico.  

PubMed

Introduction The use of entomopathogenic fungi to control disease vectors has become relevant because traditional chemical control methods have caused damage to the environment and led to the development of resistance among vectors. Thus, this study assessed the pathogenicity of entomopathogenic fungi in Triatoma dimidiata. Methods Preparations of 108 conidia/ml of Gliocladium virens, Talaromyces flavus, Beauveria bassiana and Metarhizium anisopliae were applied topically on T. dimidiata nymphs and adults. Controls were treated with the 0.0001% Tween-80 vehicle. Mortality was evaluated and recorded daily for 30 days. The concentration required to kill 50% of T. dimidiata (LC50) was then calculated for the most pathogenic isolate. Results Pathogenicity in adults was similar among B. bassiana, G. virens and T. flavus (p>0.05) and differed from that in triatomine nymphs (p=0.009). The most entomopathogenic strains in adult triatomines were B. bassiana and G. virens, which both caused 100% mortality. In nymphs, the most entomopathogenic strain was B. bassiana, followed by G. virens. The native strain with the highest pathogenicity was G. virens, for which the LC50 for T. dimidiata nymphs was 1.98 x108 conidia/ml at 13 days after inoculation. Conclusions Beauveria bassiana and G. virens showed entomopathogenic potential in T. dimidiata nymphs and adults. However, the native G. virens strain presents a higher probability of success in the field, and G. virens should thus be considered a potential candidate for the biological control of triatomine Chagas disease vectors. PMID:25626650

Vázquez-Martínez, María Guadalupe; Cirerol-Cruz, Blanca Elva; Torres-Estrada, José Luis; López, Mario Henry Rodríguez

2014-12-01

286

Space vector control and current harmonics in quasi-resonant soft-switching PWM conversion  

Microsoft Academic Search

The paper presents an analysis of the behaviour of the modulation schemes useful for the soft-switched, quasi-resonant VSI power inverter in comparison with standard PWM techniques (sine-triangle and space-vector). Although the presence of a purely capacitive snubber across each power device allows true PWM in such converters, the switching sequence constraints due to the load current vector may result in

L. Malesani; P. Tomasin; V. Toigo

1994-01-01

287

Toxic side effects of drugs used to treat Chagas' disease (American trypanosomiasis).  

PubMed

Chagas' disease (American trypanosomiasis) is an endemic parasitic disease in some areas of Latin America. About 16-18 million persons are infected with the aetiological agent of the disease, Trypanosoma cruzi, and more than 100 million are living at risk of infection. There are different modes of infection: (1) via blood sucking vector insects infected with T. cruzi, accounting for 80-90% of transmission of the disease; (2) via blood transfusion or congenital transmission, accounting for 0.5-8% of transmission; (3) other less common forms of infection, eg, from infected food or drinks or via infected organs used in transplants. The acute phase of the disease can last from weeks to months and typically is asymptomatic or associated with fever and other mild nonspecific manifestations. However, life-threatening myocarditis or meningoencephalitis can occur during the acute phase. The death rate for persons in this phase is about 10%. Approximately 10-50% of the survivors develop chronic Chagas' disease, which is characterized by potentially lethal cardiopathy and megacolon or megaoesophagus. There are two drugs available for the aetiological treatment of Chagas' disease: nifurtimox (Nfx) and benznidazole (Bz). Nfx is a nitrofurane and Bz is a nitroimidazole compound. The use of these drugs to treat the acute phase of the disease is widely accepted. However, their use in the treatment of the chronic phase is controversial. The undesirable side effects of both drugs are a major drawback in their use, frequently forcing the physician to stop treatment. The most frequent adverse effects observed in the use of Nfx are: anorexia, loss of weight, psychic alterations, excitability, sleepiness, digestive manifestations such as nausea or vomiting, and occasionally intestinal colic and diarrhoea. In the case of Bz, skin manifestations are the most notorious (e.g., hypersensitivity, dermatitis with cutaneous eruptions, generalized oedema, fever, lymphoadenopathy, articular and muscular pain), with depression of bone marrow, thrombocytopenic purpura and agranulocytosis being the more severe manifestations. Experimental toxicity studies with Nfx evidenced neurotoxicity, testicular damage, ovarian toxicity, and deleterious effects in adrenal, colon, oesophageal and mammary tissue. In the case of Bz, deleterious effects were observed in adrenals, colon and oesophagus. Bz also inhibits the metabolism of several xenobiotics biotransformed by the cytochrome P450 system and its reactive metabolites react with fetal components in vivo. Both drugs exhibited significant mutagenic effects and were shown to be tumorigenic or carcinogenic in some studies. The toxic side effects of both nitroheterocyclic derivatives require enzymatic reduction of their nitro group. Those processes are fundamentally mediated by cytochrome P450 reductase and cytochrome P450. Other enzymes such as xanthine oxidoreductase or aldehyde oxidase may also be involved. PMID:16937919

Castro, José A; de Mecca, Maria Montalto; Bartel, Laura C

2006-08-01

288

Development and Assessment of Plant-Based Synthetic Odor Baits for Surveillance and Control of Malaria Vectors  

PubMed Central

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)-?-ocimene [LO + OC], and a six-component blend comprising (E)-linalool oxide, (E)-?-ocimene, hexanal, ?-pinene, limonene, and (E)-?-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 without carbon dioxide, for surveillance and mass trapping of malaria vectors. PMID:24587059

Nyasembe, Vincent O.; Tchouassi, David P.; Kirwa, Hillary K.; Foster, Woodbridge A.; Teal, Peter E. A.; Borgemeister, Christian; Torto, Baldwyn

2014-01-01

289

The control of malaria vectors in the context of the Health for All by the Year 2000 Global Strategy.  

PubMed

The changing picture of malaria worldwide needs to be viewed in the context of other developments before we can determine the directions to take to be able to provide the thrusts required in malaria vector control. As a result of population growth, increasing urbanization and continuing pressure on scarce natural resources, the epidemiology of malaria and its manifestation as a public health problem are undergoing profound modifications, indeed in several parts of the world. This picture is further complicated by the spread of resistance to pesticides in the vector and to drugs in Plasmodium falciparum. In the immediate future, these trends will continue. In addition, the appearance of suitable vaccines is a highly probable event to be taken into consideration. The WHO Global Strategy of Health For All by the Year 2000 aims at the improvement of levels of health through primary health care. Among other things, this implies a greater reliance on community involvement and on intersectoral collaboration for health. In this light, the major malaria problems in the year 2000 will be: (1) "hard core" endemic areas with inadequate infrastructure and poor socio-economic development; (2) resource development areas, in particular those under illegal or poor controlled exploitation; (3) expanding urban areas and (4) increased mobility of non-immunes, particularly if uncontrolled. In order to cope with these problems, thrusts are required towards the development of vector control strategies, covering the following fields: (1) tools for vector control integrated in primary health care, (2) new chemicals, (3) improved and new biologicals, (4) environmental management and the adoption of health safeguards in resource development projects and (5) manpower development. PMID:3504941

Slooff, R

1987-12-01

290

Preliminary Investigation on Battery Sizing Investigation for Thrust Vector Control on Ares I and Ares V Launch Vehicles  

NASA Technical Reports Server (NTRS)

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.

Miller, Thomas B.

2011-01-01

291

Multiaxis control power from thrust vectoring for a supersonic fighter aircraft model at Mach 0.20 to 2.47  

NASA Technical Reports Server (NTRS)

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.

Capone, Francis J.; Bare, E. Ann

1987-01-01

292

Loss of genetic diversity in Culex quinquefasciatus targeted by a lymphatic filariasis vector control program in Recife, Brazil.  

PubMed

Recife is one of the largest cities in north-eastern Brazil and is endemic for lymphatic filariasis transmitted by Culex quinquefasciatus. Since 2003 a control program has targeted mosquito larvae by elimination of breeding sites and bimonthly application of Bacillus sphaericus. To assess the impact of this program on the local vector population we monitored the genetic diversity and differentiation of Cx. quinquefasciatus using microsatellites and a B. sphaericus-resistance associated mutation (cqm1(REC)) over a 3-year period. We detected a significant but gradual decline in allelic diversity, which, coupled with subtle temporal genetic structure, suggests a major impact of the control program on the vector population. Selection on cqm1(REC) does not appear to be involved with loss of neutral diversity from the population, with no temporal trend in resistant allele frequency and no correlation with microsatellite differentiation. The evidence for short-term genetic drift we detected suggests a low ratio of effective population size: census population size for Cx. quinquefasciatus, perhaps coupled with strong geographically-restricted population structure. Spatial definition of populations will be an important step for success of an expanded vector control program. PMID:21737112

Cartaxo, Marina F S; Ayres, Constância F J; Weetman, David

2011-09-01

293

Safety, Pharmacokinetic, and Efficacy Studies of Oral DB868 in a First Stage Vervet Monkey Model of Human African Trypanosomiasis  

E-print Network

There are no oral drugs for human African trypanosomiasis (HAT, sleeping sickness). A successful oral drug would have the potential to reduce or eliminate the need for patient hospitalization, thus reducing healthcare costs of HAT. The development...

Thutia, John K.; Wolf, Kristina K.; Murilla, Grace A.; Liu, Qiang; Mutuku, James N.; Chen, Yao; Bridges, Arlene S.; Mdachi, Raymond E.; Ismail, Mohamed A.; Ching, Shelley; Boykin, David W.; Hall, James E.; Tidwell, Richard R.; Paine, Mary F.; Brun, Reto; Wang, Michael Z.

2013-06-06

294

Programmable Memory Controller for Vector System-on-ChipProgrammable Memory Controller for Vector System-on-Chip Tassadaq HussainTassadaq Hussain  

E-print Network

of CPU Number of Clocks are dependent: Computation Delay Address/Data Management Delay On-chip/Off-chip are required to have a Programmable Memory Controller which includes: Manage processing elements without

Chaudhuri, Surajit

295

A review of the vector management methods to prevent and control outbreaks of West Nile virus infection and the challenge for Europe  

PubMed Central

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

2014-01-01

296

Screening Mosquito House Entry Points as a Potential Method for Integrated Control of Endophagic Filariasis, Arbovirus and Malaria Vectors  

PubMed Central

Background Partial mosquito-proofing of houses with screens and ceilings has the potential to reduce indoor densities of malaria mosquitoes. We wish to measure whether it will also reduce indoor densities of vectors of neglected tropical diseases. Methodology The main house entry points preferred by anopheline and culicine vectors were determined through controlled experiments using specially designed experimental huts and village houses in Lupiro village, southern Tanzania. The benefit of screening different entry points (eaves, windows and doors) using PVC-coated fibre glass netting material in terms of reduced indoor densities of mosquitoes was evaluated compared to the control. Findings 23,027 mosquitoes were caught with CDC light traps; 77.9% (17,929) were Anopheles gambiae sensu lato, of which 66.2% were An. arabiensis and 33.8% An. gambiae sensu stricto. The remainder comprised 0.2% (50) An. funestus, 10.2% (2359) Culex spp. and 11.6% (2664) Mansonia spp. Screening eaves reduced densities of Anopheles gambiae s. l. (Relative ratio (RR) ?=?0.91; 95% CI?=?0.84, 0.98; P?=?0.01); Mansonia africana (RR?=?0.43; 95% CI?=?0.26, 0.76; P<0.001) and Mansonia uniformis (RR?=?0.37; 95% CI?=?0.25, 0.56; P<0.001) but not Culex quinquefasciatus, Cx. univittatus or Cx. theileri. Numbers of these species were reduced by screening windows and doors but this was not significant. Significance This study confirms that across Africa, screening eaves protects households against important mosquito vectors of filariasis, Rift Valley Fever and O'Nyong nyong as well as malaria. While full house screening is required to exclude Culex species mosquitoes, screening of eaves alone or fitting ceilings has considerable potential for integrated control of other vectors of filariasis, arbovirus and malaria. PMID:20689815

Ogoma, Sheila B.; Lweitoijera, Dickson W.; Ngonyani, Hassan; Furer, Benjamin; Russell, Tanya L.; Mukabana, Wolfgang R.; Killeen, Gerry F.; Moore, Sarah J.

2010-01-01

297

Diagnostic Accuracy and Feasibility of Serological Tests on Filter Paper Samples for Outbreak Detection of T.b. gambiense Human African Trypanosomiasis  

PubMed Central

Control of human African trypanosomiasis (HAT) in the Democratic Republic of Congo is based on mass population screening by mobile teams; a costly and labor-intensive approach. We hypothesized that blood samples collected on filter paper by village health workers and processed in a central laboratory might be a cost-effective alternative. We estimated sensitivity and specificity of micro-card agglutination test for trypanosomiasis (micro-CATT) and enzyme-linked immunosorbent assay (ELISA)/T.b. gambiense on filter paper samples compared with parasitology-based case classification and used the results in a Monte Carlo simulation of a lot quality assurance sampling (LQAS) approach. Micro-CATT and ELISA/T.b. gambiense showed acceptable sensitivity (92.7% [95% CI 87.4–98.0%] and 82.2% [95% CI 75.3–90.4%]) and very high specificity (99.4% [95% CI 99.0–99.9%] and 99.8% [95% CI 99.5–100%]), respectively. Conditional on high sample size per lot (? 60%), both tests could reliably distinguish a 2% from a zero prevalence at village level. Alternatively, these tests could be used to identify individual HAT suspects for subsequent confirmation. PMID:20682885

Hasker, Epco; Lutumba, Pascal; Mumba, Dieudonné; Lejon, Veerle; Büscher, Phillipe; Kande, Victor; Muyembe, Jean Jacques; Menten, Joris; Robays, Jo; Boelaert, Marleen

2010-01-01

298

Diagnostic accuracy and feasibility of serological tests on filter paper samples for outbreak detection of T.b. gambiense human African trypanosomiasis.  

PubMed

Control of human African trypanosomiasis (HAT) in the Democratic Republic of Congo is based on mass population screening by mobile teams; a costly and labor-intensive approach. We hypothesized that blood samples collected on filter paper by village health workers and processed in a central laboratory might be a cost-effective alternative. We estimated sensitivity and specificity of micro-card agglutination test for trypanosomiasis (micro-CATT) and enzyme-linked immunosorbent assay (ELISA)/T.b. gambiense on filter paper samples compared with parasitology-based case classification and used the results in a Monte Carlo simulation of a lot quality assurance sampling (LQAS) approach. Micro-CATT and ELISA/T.b. gambiense showed acceptable sensitivity (92.7% [95% CI 87.4-98.0%] and 82.2% [95% CI 75.3-90.4%]) and very high specificity (99.4% [95% CI 99.0-99.9%] and 99.8% [95% CI 99.5-100%]), respectively. Conditional on high sample size per lot (> or = 60%), both tests could reliably distinguish a 2% from a zero prevalence at village level. Alternatively, these tests could be used to identify individual HAT suspects for subsequent confirmation. PMID:20682885

Hasker, Epco; Lutumba, Pascal; Mumba, Dieudonné; Lejon, Veerle; Büscher, Phillipe; Kande, Victor; Muyembe, Jean Jacques; Menten, Joris; Robays, Jo; Boelaert, Marleen

2010-08-01

299

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)

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.

Kimball, G., Jr.

1980-01-01

300

Interactive Visualization of Three-Dimensional Vector Fields with Flexible Appearance Control  

E-print Network

with enhanced structural perception using various visual cues can be rendered in real time. A myriad of existing. First, flow lines are generated from the 3D vector data. Various geometric properties of the flow paths. In the second phase of the algorithm, the attributes stored in the volume are used as texture coordinates

Utah, University of

301

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. ...

302

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...

303

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...

304

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...

305

VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE Laboratory and Field Evaluation of the Entomopathogenic Fungus  

E-print Network

, blacklegged tick, Lyme disease, entomopathogenic fungi Ixodes scapularis SAY is the principal vector in North species (Pancholi et al. 1995, Walker and Dumler 1996); the pathogens that cause Lyme disease, babesiosis, and human granulocytic ehrlichiosis, respectively. The prevalence of Lyme disease and other tick-borne dis

306

Influence of source and quantity of protein on the development of immunity and resistance to African trypanosomiasis.  

PubMed Central

Although it is well documented that severe protein deprivation inhibits the development of the immune response and exacerbates certain infections, little has been done to study the effects of native diets on endemic diseases or immunity. Therefore, protein-restricted diets were formulated for mice to mimic the sources and amounts measured in human diets of the Batouri region of Cameroon, endemic for African trypanosomiasis. Weanling C57BL/6 female mice were fed a diet that contained 73% of the recommended daily allowance (RDA) of protein. The sources of protein were all plant (cornmeal), all animal (casein), or a ratio that reflected the native diet (2.2 parts plant to 1 part animal protein). Diets were isocaloric on a weight basis, equal in lipids, and adequate in vitamins and minerals. Control mice were fed laboratory chow or two times the RDA of animal protein (casein). Mice fed only cornmeal or the native diets consumed as much food but did not gain as much weight as mice fed only animal protein, indicating the poorer quality of protein in their diets. Upon infection with Trypanosoma brucei gambiense, however, significantly higher numbers of these mice controlled the first peak of parasitemia and survived the infection as compared with mice fed the other three diets. Since all mice developed patent infections and the parasite growth rate was unaffected by diet, innate immune factors were ruled out as the cause for the higher level of resistance to the parasite. To determine whether diet affected the development of the immune system, weanling mice were maintained on diets for 30 days before immunization with sheep erythrocytes or trinitrophenylated Ficoll. Mice fed only plant protein or native diets elicited higher direct plaque-forming-cell responses to both the T-cell-dependent and T-cell-independent antigens. Since variant-specific immunity which controls levels of African trypanosomes in the blood is a T-cell-independent humoral immunoglobulin M response, this suggests that cornmeal, a protein of poor quality, was adequate for the development of humoral immunity and resistance to African trypanosomiasis while casein, an animal protein of high quality, was not. This provides more evidence that diet plays an important role in infection and immunity. PMID:3484725

Norton, J D; Yang, S P; Diffley, P

1986-01-01

307

An alternative to killing? Treatment of reservoir hosts to control a vector and pathogen in a susceptible species.  

PubMed

Parasite-mediated apparent competition occurs when one species affects another through the action of a shared parasite. One way of controlling the parasite in the more susceptible host is to manage the reservoir host. Culling can cause issues in terms of ethics and biodiversity impacts, therefore we ask: can treating, as compared to culling, a wildlife host protect a target species from the shared parasite? We used Susceptible Infected Recovered (SIR) models parameterized for the tick-borne louping ill virus (LIV) system. Deer are the key hosts of the vector (Ixodes ricinus) that transmits LIV to red grouse Lagopus lagopus scoticus, causing high mortality. The model was run under scenarios of varying acaricide efficacy and deer densities. The model predicted that treating deer can increase grouse density through controlling ticks and LIV, if acaricide efficacies are high and deer densities low. Comparing deer treated with 70% acaricide efficacy with a 70% cull rate suggested that treatment may be more effective than culling if initial deer densities are high. Our results will help inform tick control policies, optimize the targeting of control methods and identify conditions where host management is most likely to succeed. Our approach is applicable to other host-vector-pathogen systems. PMID:22939093

Porter, R; Norman, R A; Gilbert, L

2013-02-01

308

Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania  

PubMed Central

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 indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it. As work begins in the SFS in Ifakara and others around the world, the major opportunities and challenges to the successful application of this tool for malaria vector research and control are discussed. PMID:18715508

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

309

Characterisation and semi-mechanistic modelling of eflornithine pharmacokinetics and evalutation of prodrugs in oral treatment against late-stage human African trypanosomiasis.  

E-print Network

??The present thesis explores the hypothesis that treatment of human African trypanosomiasis can be improved by characterising the enantioselective pharmacokinetics of eflornithine, and investigating the… (more)

Johansson, Carl

2013-01-01

310

Can malaria vector control accelerate the interruption of lymphatic filariasis transmission in Africa; capturing a window of opportunity?  

PubMed Central

Background The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000, and nearly all endemic countries in the Americas, Eastern Mediterranean and Asia-Pacific regions have now initiated the WHO recommended mass drug administration (MDA) campaign to interrupt transmission of the parasite. However, nearly 50% of the LF endemic countries in Africa are yet to implement the GPELF MDA strategy, which does not include vector control. Nevertheless, the recent scale up in insecticide treated /long lasting nets (ITNs/LLINs) and indoor residual spraying (IRS) for malaria control in Africa may significantly impact LF transmission because the parasite is transmitted mainly by Anopheles mosquitoes. This study examined the magnitude, geographical extent and potential impact of vector control in the 17 African countries that are yet to or have only recently started MDA. Methods National data on mosquito bed nets, ITNs/LLINs and IRS were obtained from published literature, national reports, surveys and datasets from public sources such as Demographic Health Surveys, Malaria Indicator Surveys, Multiple Indicator Cluster Surveys, Malaria Report, Roll Back Malaria and President’s Malaria Initiative websites. The type, number and distribution of interventions were summarised and mapped at sub-national level. and compared with known or potential LF distributions, and those which may be co-endemic with Loa loa and MDA is contraindicated. Results Analyses found that vector control activities had increased significantly since 2005, with a three-fold increase in ITN ownership and IRS coverage. However, coverage varied dramatically across the 17 countries; some regions reported >70% ITNs ownership and regular IRS activity, while others had no coverage in remote rural populations where the risk of LF was potentially high and co-endemic with high risk L.loa. Conclusions Despite many African countries being slow to initiate MDA for LF, the continued commitment and global financial support for NTDs, and the concurrent expansion of vector control activities for malaria, is promising. It is not beyond the capacity of GPELF to reach its target of global LF elimination by 2020, but monitoring and evaluating the impact of these activities over the next decade will be critical to its success. PMID:23433078

2013-01-01

311

Women's knowledge and perceptions of malaria and use of malaria vector control interventions in Kersa, eastern Ethiopia  

PubMed Central

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 actually used their nets. Efforts must be made to ensure the correct channeling of information about malaria, particularly regarding the importance of using malaria vector control interventions. Furthermore, to maximize the benefit of the intervention in the district, IRC coverage and LLIN use need to be stronger. PMID:23706162

Gobena, Tesfaye; Berhane, Yemane; Worku, Alemayehu

2013-01-01

312

Space vector control and current harmonics in quasi-resonant soft-switching PWM conversion  

Microsoft Academic Search

The paper presents an analysis of the behavior of the modulation schemes useful for the soft-switched, quasi-resonant VSI power inverter in comparison with standard PWM techniques (sine-triangle and space-vector). Although the presence of a purely capacitive snubber across each power device in such kinds of converters allows true PWM, this is affected by some constraints in the switching sequence depending

Luigi Malesani; Paolo Tomasin; Vanni Toigo

1996-01-01

313

Advanced solid rocket motor nozzle thrust vector control flexseal development status  

NASA Astrophysics Data System (ADS)

The advanced solid rocket motor (ASRM) flexseal development status is reviewed focusing on design goals and requirements, design configuration, analysis activities, and verification tests. It is concluded that the ASRM flexseal incorporates flight-proven materials in an innovative design configuration. Variable thickness shims and efficient packaging of the flexseal make it possible to achieve a significant weight reduction. A flexseal insulator design derived from strategic solid rocket motor experience will provide the necessary bearing thermal protection while minimizing vectoring torque variability.

Prins, William S.; Meyer, Scott A.; Cox, Paul D.

1992-07-01

314

Indigenous knowledge system for treatment of trypanosomiasis in Kaduna state of Nigeria.  

PubMed

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. PMID:11801393

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

315

Spatial orientation and balance control changes induced by altered gravitoinertial force vectors  

NASA Technical Reports Server (NTRS)

To better understand the mechanisms of human adaptation to rotating environments, we exposed 19 healthy subjects and 8 vestibular-deficient subjects ("abnormal"; four bilateral and four unilateral lesions) to an interaural centripetal acceleration of 1 g (resultant 45 degrees roll-tilt of 1.4 g) on a 0.8-m-radius centrifuge for periods of 90 min. The subjects sat upright (body z-axis parallel to centrifuge rotation axis) in the dark with head stationary, except during 4 min of every 10 min, when they performed head saccades toward visual targets switched on at 3- to 5-s intervals at random locations (within +/- 30 degrees) in the earth-horizontal plane. Eight of the normal subjects also performed the head saccade protocol in a stationary chair adjusted to a static roll-tilt angle of 45 degrees for 90 min (reproducing the change in orientation but not the magnitude of the gravitoinertial force on the centrifuge). Eye movements, including voluntary saccades directed along perceived earth- and head-referenced planes, were recorded before, during, and immediately after centrifugation. Postural center of pressure (COP) and multisegment body kinematics were also gathered before and within 10 min after centrifugation. Normal subjects overestimated roll-tilt during centrifugation and revealed errors in perception of head-vertical provided by directed saccades. Errors in this perceptual response tended to increase with time and became significant after approximately 30 min. Motion-sickness symptoms caused approximately 25% of normal subjects to limit their head movements during centrifugation and led three normal subjects to stop the test early. Immediately after centrifugation, subjects reported feeling tilted 10 degrees in the opposite direction, which was in agreement with the direction of their earth-referenced directed saccades. Postural COP, segmental body motion amplitude, and hip-sway frequency increased significantly after centrifugation. These postural effects 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.

Kaufman, G. D.; Wood, S. J.; Gianna, C. C.; Black, F. O.; Paloski, W. H.

2001-01-01

316

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)

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.

Lallman, Frederick J.; Davidson, John B.; Murphy, Patrick C.

1998-01-01

317

Intrathecal Immune Response Pattern for Improved Diagnosis of Central Nervous System Involvement in Trypanosomiasis  

Microsoft Academic Search

(95%) marker for inflammation of the brain. We propose to replace the World Health Organization (WHO) criteria (white blood cell count 15 cells\\/mL and presence of trypanosomes in CSF) with a new approach for stage determination in trypanosomiasis: CNS involvement is diagnosed only in patients with 120 cells\\/m Lo r with intrathecal IgM synthesis, independent of the presence of trypanosomes

Veerle Lejon; Hansotto Reiber; Dominique Legros; Norbert Djé; Eddy Magnus; Ingrid Wouters; Philippe Büscher

2003-01-01

318

A current analysis of chemotherapy strategies for the treatment of human African trypanosomiasis.  

PubMed

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. PMID:23916333

Babokhov, Peter; Sanyaolu, Adekunle O; Oyibo, Wellington A; Fagbenro-Beyioku, Adetayo F; Iriemenam, Nnaemeka C

2013-07-01

319

A current analysis of chemotherapy strategies for the treatment of human African trypanosomiasis  

PubMed Central

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. PMID:23916333

Babokhov, Peter; Sanyaolu, Adekunle O; Oyibo, Wellington A; Fagbenro-Beyioku, Adetayo F; Iriemenam, Nnaemeka C

2013-01-01

320

Vector control improves survival of three species of prairie dogs (Cynomys) in areas considered enzootic for plague.  

PubMed

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. PMID:20158328

Biggins, Dean E; Godbey, Jerry L; Gage, Kenneth L; Carter, Leon G; Montenieri, John A

2010-01-01

321

Dengue Vector Dynamics (Aedes aegypti) Influenced by Climate and Social Factors in Ecuador: Implications for Targeted Control  

PubMed Central

Background Dengue fever, a mosquito-borne viral disease, is now the fastest spreading tropical disease globally. Previous studies indicate that climate and human behavior interact to influence dengue virus and vector (Aedes aegypti) population dynamics; however, the relative effects of these variables depends on local ecology and social context. We investigated the roles of climate and socio-ecological factors on Ae. aegypti population dynamics in Machala, a city in southern coastal Ecuador where dengue is hyper-endemic. Methods/Principal findings We studied two proximate urban localities where we monitored weekly Ae. aegypti oviposition activity (Nov. 2010-June 2011), conducted seasonal pupal surveys, and surveyed household to identify dengue risk factors. The results of this study provide evidence that Ae. aegypti population dynamics are influenced by social risk factors that vary by season and lagged climate variables that vary by locality. Best-fit models to predict the presence of Ae. aegypti pupae included parameters for household water storage practices, access to piped water, the number of households per property, condition of the house and patio, and knowledge and perceptions of dengue. Rainfall and minimum temperature were significant predictors of oviposition activity, although the effect of rainfall varied by locality due to differences in types of water storage containers. Conclusions These results indicate the potential to reduce the burden of dengue in this region by conducting focused vector control interventions that target high-risk households and containers in each season and by developing predictive models using climate and non-climate information. These findings provide the region's public health sector with key information for conducting time and location-specific vector control campaigns, and highlight the importance of local socio-ecological studies to understand dengue dynamics. See Text S1 for an executive summary in Spanish. PMID:24324542

Stewart Ibarra, Anna M.; Ryan, Sadie J.; Beltrán, Efrain; Mejía, Raúl; Silva, Mercy; Muñoz, Ángel

2013-01-01

322

Novel, Meso-Substituted Cationic Porphyrin Molecule for Photo-Mediated Larval Control of the Dengue Vector Aedes aegypti  

PubMed Central

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

Lucantoni, Leonardo; Magaraggia, Michela; Lupidi, Giulio; Ouedraogo, Robert Kossivi; Coppellotti, Olimpia; Esposito, Fulvio; Fabris, Clara; Jori, Giulio; Habluetzel, Annette

2011-01-01

323

The Changing Epidemiology of Human African Trypanosomiasis among Patients from Nonendemic Countries –1902–2012  

PubMed Central

Background Although human African trypanosomiasis (HAT) is uncommon among patients from non-endemic countries (NEC), there has been an increase in the number of cases reported in recent years. Methods A systematic review of the literature was performed. The number of incoming tourists to HAT endemic countries was obtained from the United Nations World Tourism Organization. All HAT cases diagnosed in patients from NEC were included. Immigrants and refugees were excluded. We compared patients during and after the colonial period, and analyzed the relationship between the number of incoming travellers and the number of HAT cases. Results Between 1902 and 2012, HAT was reported in 244 patients. Most HAT cases were reported before 1920, and after the year 2000. In the colonial era the average age of patients was lower (32.5±7.8 vs. 43.0±16.1 years, P<0.001), the proportion of females was lower (10.0% vs. 23.9%, P<0.01], most cases were diagnosed in expatriates, missionaries and soldiers (74.3%), and Gambian trypanosomiasis accounted for 86/110, (78%) of cases. In the post-colonial era most patients 91/125 (72.8%) were short-term tourists to game parks in Eastern and South-Eastern Africa (mainly in Tanzania); Rhodesian trypanosomiasis accounted for 94/123 (76.4%) of cases. Between 1995 and 2010 there has been a constant linear increase in the number of incoming tourists to Tanzania, and HAT cases occurred in small outbreaks rather than following a similar linear pattern. Conclusions In recent decades HAT patients from NEC are older, and more likely to be tourists who acquired the disease while visiting game-parks in Eastern and South-Eastern Africa. While Rhodesian trypanosomiasis is relatively uncommon among Africans, it now accounts for most cases reported among patients from NEC. Returning febrile travellers without an alternative diagnosis should be evaluated for HAT. Cases among travellers may serve as sentinels for Rhodesian trypanosomiasis “hot spots” in Africa. PMID:24586363

Neuberger, Ami; Meltzer, Eyal; Leshem, Eyal; Dickstein, Yaakov; Stienlauf, Shmuel; Schwartz, Eli

2014-01-01

324

A bloodstream Trypanosoma congolense sialidase could be involved in anemia during experimental trypanosomiasis.  

PubMed

The release of Sialic acid (SA) into the serum by Trypanosoma congolense infected BalbC mice was investigated. A progressive increase in the level of serum SA corresponding to anemia and parasitemia was observed. At maximum parasitemia, the level of total SA from the red blood cells (RBC) dropped by about 45%. Solved polynomials revealed an association between free serum SA and RBC-SA. Positive roots of quadratics were used to predict complete cleavage of RBC-SA on day 7.01 and maximum accumulation of free serum SA on day 6.6. A steady rise in the level of serum sialidase (SD) activity and a low packed cell volume (PCV) with an increase in parasitemia were observed. Mice infused with galactose, methyl-beta-gal, lactose, mannose, or L-arabinose and challenged by intraperitoneal inoculation with Trypanosoma congolense neither developed anemia nor secreted free SA above the control level even though there was detectable SD activity. Bloodstream Trypanosoma congolense parasites were isolated using DEAE cellulose from heparinized blood of experimentally infected BalbC mice. The parasites were lysed with 0.2% Triton-CF 54 to release membrane bound SD. The activity of the SD was proportional to the number of parasites. The enzyme was partially purified on Q-Sepharose and Fetuin agarose columns successively. The final active fraction from the latter column was used as the partially purified SD. The enzyme had an optimum pH of 6 and was maximally active at 37 degrees C with a requirement for the divalent ions Ca(2+) and Mg(2+). The enzyme was highly specific for NeuAc5alpha2,3 lac and Methylumbelliferyl-Neu5Ac (4-MU-Neu5Ac) with K(M) values of 0.34 and 0.025 mM, respectively. It was inhibited competitively by 2,3-didehydroneuraminic acid (Neu5Ac2en) and para-nitro-phenyloxamic acid (pNPO) with inhibition binding constants K(i) of 65 and 215 micro M, respectively. In deviation from the procyclic trypanosomal SD, it lacked trans-sialidase (TS) activity. The possible role of a secreted bloodstream Trypanosoma congolense SD and the development of anemia in the pathogensesis of trypanosomiasis are discussed. PMID:12869528

Nok, Andrew J; Balogun, Emmanuel O

2003-06-01

325

Control algorithm for the inverter fed induction motor drive with DC current feedback loop based on principles of the vector control  

SciTech Connect

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.

Vuckovic, V.; Vukosavic, S. (Electrical Engineering Inst. Nikola Tesla, Viktora Igoa 3, Belgrade, 11000 (Yugoslavia))

1992-01-01

326

Microbial symbiosis and the control of vector-borne pathogens in tsetse flies, human lice, and triatomine bugs  

PubMed Central

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

Sassera, Davide; Epis, Sara; Pajoro, Massimo; Bandi, Claudio

2013-01-01

327

Cultivation-Independent Methods Reveal Differences among Bacterial Gut Microbiota in Triatomine Vectors of Chagas Disease  

PubMed Central

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 differs according to the vector genus. PMID:22563511

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

328

On noninferior performance index vectors  

Microsoft Academic Search

The noninferior vector index problem of optimal control theory is investigated in an effort to establish some basic properties of the noninferior index surface in the generalN-dimensional index problem. The vector performance index problem is first converted to a family of scalar index problems by forming an auxiliary scalar index as a function of the vector index and a vector

R. W. Reid; S. J. Citron

1971-01-01

329

Research of multi ingredients system control method based on fuzzy support vector machine  

Microsoft Academic Search

This paper analyzed shortcomings of multi ingredients control methods. The four-group Ingredient system of certain marked cement was adopted to prove that, improper proportional control of each ingredient will lose quality. Aimed at solve the problem of limited samples, strong real time, unstable flow speed of raw meal, through reforming the mouth of input of raw meal, adding the control

Yi Tang

2010-01-01

330

Identification and expression of the CCAP receptor in the Chagas' disease vector, Rhodnius prolixus, and its involvement in cardiac control.  

PubMed

Rhodnius prolixus is the vector of Chagas' disease, by virtue of transmitting the parasite Trypanosoma cruzi. There is no cure for Chagas' disease and therefore controlling R. prolixus is currently the only method of prevention. Understanding the physiology of the disease vector is an important step in developing control measures. Crustacean cardioactive peptide (CCAP) is an important neuropeptide in insects because it has multiple physiological roles such as controlling heart rate and modulating ecdysis behaviour. In this study, we have cloned the cDNA sequence of the CCAP receptor (RhoprCCAPR) from 5(th) instar R. prolixus and found it to be a G-protein coupled receptor (GPCR). The spatial expression pattern in 5(th) instars reveals that the RhoprCCAPR transcript levels are high in the central nervous system, hindgut and female reproductive systems, and lower in the salivary glands, male reproductive tissues and a pool of tissues including the dorsal vessel, trachea, and fat body. Interestingly, the RhoprCCAPR expression is increased prior to ecdysis and decreased post-ecdysis. A functional receptor expression assay confirms that the RhoprCCAPR is activated by CCAP (EC50?=?12 nM) but not by adipokinetic hormone, corazonin or an extended FMRFamide. The involvement of CCAP in controlling heartbeat frequency was studied in vivo and in vitro by utilizing RNA interference. In vivo, the basal heartbeat frequency is decreased by 31% in bugs treated with dsCCAPR. Knocking down the receptor in dsCCAPR-treated bugs also resulted in loss of function of applied CCAP in vitro. This is the first report of a GPCR knock-down in R. prolixus and the first report showing that a reduction in CCAPR transcript levels leads to a reduction in cardiac output in any insect. PMID:23874803

Lee, Dohee; Vanden Broeck, Jozef; Lange, Angela B

2013-01-01

331

Cytokine profiles in the central nervous system and the spleen during the early course of experimental African trypanosomiasis.  

PubMed

Cytokines are important signalling proteins, which have been shown to contribute to immunopathogenesis of several inflammatory and infectious diseases such as African trypanosomiasis. The present study was conducted in order to evaluate the early induction of five potential cytokines in the central nervous system (CNS) and spleens from Trypanosoma brucei brucei (T. b. brucei)-inoculated and uninfected control Sprague-Dawley rats. In brain, choroid plexus and spleen, cytokine levels were examined by in situ hybridization and immunohistochemistry, while ELISA was used to measure cytokine levels in cerebrospinal fluid (CSF). Our results showed that interferon (IFN)-gamma and transforming growth factor (TGF)-beta were highly expressed in all compartments, but low interleukin (IL)-4, IL-10 and tumour necrosis factor (TNF)-alpha mRNA levels were registered. The pattern of these cytokines is in context with the severity of the disease because (i) IFN-gamma was previously demonstrated to promote parasite growth (ii) TNF-alpha was previously demonstrated to kill the parasites and (iii) IL-4 was previously demonstrated to promote antibody production necessary for elimination of the infection. These data support the hypothesis that cytokines may have a role in developing the disease either by enhancing the parasite growth or by suppressing the immune response. PMID:10447934

Sharafeldin, A; Hamadien, M; Diab, A; Li, H; Shi, F; Bakhiet, M

1999-09-01

332

wFlu: Characterization and Evaluation of a Native Wolbachia from the Mosquito Aedes fluviatilis as a Potential Vector Control Agent  

PubMed Central

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 artificially-transfected to the novel mosquito hosts that are the vectors of human pathogens. PMID:23555728

Gonçalves, Daniela da Silva; Moreira, Luciano Andrade

2013-01-01

333

Simon J. Foote is the Joint Head of the  

E-print Network

at the International Livestock Research Institute, Nairobi, Kenya. Keywords: trypanosomiasis trypanosomosis, malaria-mail: Simon.Foote@utas.edu.au Controlling malaria and African trypanosomiasis: The role of the mouse Simon J and trypanosomiasis are vector-borne protozoal diseases which disproportionately affect the poor. Both give rise

Steve Kemp

334

Severity of Human African Trypanosomiasis in East Africa Is Associated with Geographic Location, Parasite Genotype, and Host Inflammatory Cytokine Response Profile  

Microsoft Academic Search

The mechanisms underlying virulence in human African trypanosomiasis are poorly understood, although studies with experimental mice suggest that unregulated host inflammatory responses are associated with disease severity. We identified two trypanosomiasis foci with dramatically different disease virulence profiles. In Uganda, infections followed an acute profile with rapid progression to the late stage (meningoencephalitic infection) in the majority of patients (86.8%).

Lorna MacLean; John E. Chisi; Martin Odiit; Wendy C. Gibson; Vanessa Ferris; Kim Picozzi; Jeremy M. Sternberg

2004-01-01

335

Follow-up of Card Agglutination Trypanosomiasis Test (CATT) positive but apparently aparasitaemic individuals in Cote d'Ivoire: evidence for a complex and heterogeneous population  

Microsoft Academic Search

Summary The aetiological diagnosis of human African trypanosomiasis (HAT) is based on the detection of the para- site, but currently available parasitological tests have low sensitivity and are hampered by fluctuating para- sitaemia. The identification of seropositive individuals on whom to focus parasitological examination is based on antibody detection by means of the Card Agglutination Trypanosomiasis Test (CATT\\/T.b.gambi- ense). A

Andre Garcia; Vincent Jamonneau; Eddy Magnus; Claude Laveissiere; Veerle Lejon; Paul N'guessan; Louis N'dri; Nestor Van Meirvenne; Philippe Buscher

2000-01-01

336

[Social representations concerning dengue, dengue vectors, and control activities among residents of São Sebastião on the northern coast of São Paulo State, Brazil].  

PubMed

This study sought to identify people's knowledge on dengue and its vector biology, aimed at promoting a communications channel between technical and lay reasoning in order to foster community involvement in dengue and dengue vector control activities. A survey was conducted in an Aedes aegypti-infested area with dengue transmission in São Sebastião on the northern coast of São Paulo State, Brazil. One hundred interviews were held, with five open questions on topics related to dengue and vector control. Collective Subject Discourse methodology was used in the analysis. People were not able to properly identify the kinds of accumulated water sources that serve as breeding places for mosquitoes and were unaware of the egg phase in vector development. There was inadequate awareness of vector biology and a need for greater government-community integration. Educational activities should incorporate the study results as insight for improving the social efficiency and efficacy of joint actions to fight dengue and control the mosquito vector. PMID:17572820

Lefèvre, Ana Maria Cavalcanti; Ribeiro, Andressa Francisca; Marques, Gisela Rita de Alvarenga Monteiro; Serpa, Lígia Leandro Nunes; Lefèvre, Fernando

2007-07-01

337

Effective control of dengue vectors with curtains and water container covers treated with insecticide in Mexico and Venezuela: cluster randomised trials  

Microsoft Academic Search

Objectives To measure the impact on the dengue vector population (Aedes aegypti) and disease transmission of window curtains and water container covers treated with insecticide. Design Cluster randomised controlled trial based on entomological surveys and, for Trujillo only, serological survey. In addition, each site had a non-randomised external control. Setting 18 urban sectors in Veracruz (Mexico) and 18 in Trujillo

Axel Kroeger; Audrey Lenhart; Manuel Ochoa; Elci Villegas; Michael Levy; Neal Alexander; P J McCall

2006-01-01

338

Key Source Habitats and Potential Dispersal of Triatoma infestans Populations in Northwestern Argentina: Implications for Vector Control  

PubMed Central

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 study illustrates a demographic approach that may be applied to other regions and triatomine species for the design of innovative, improved vector control strategies. PMID:25299653

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

339

Optimal control of a universal rotating magnetic vector for petal-shaped capsule robot in curve environment  

NASA Astrophysics Data System (ADS)

Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely. A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented, and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed. To realize quick and non-contact steering swimming, a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation, achieving the initial optimal orientation of a universal magnetic spin vector. To further reduce robotic magnetic vibration, a main target method for optimizing its final orientation, which is used for fine adjustment, is employed under the constrains of the magnetic moments. Swimming experimental results in curve pipe verified the effectiveness of the optimization method, which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.

Zhang, Yongshun; Bai, Jianwei; Chi, Minglu; Cheng, Cunxin; Wang, Dianlong

2014-08-01

340

Optimal control of a universal rotating magnetic vector for petal-shaped capsule robot in curve environment  

NASA Astrophysics Data System (ADS)

Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely. A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented, and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed. To realize quick and non-contact steering swimming, a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation, achieving the initial optimal orientation of a universal magnetic spin vector. To further reduce robotic magnetic vibration, a main target method for optimizing its final orientation, which is used for fine adjustment, is employed under the constrains of the magnetic moments. Swimming experimental results in curve pipe verified the effectiveness of the optimization method, which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.

Zhang, Yongshun; Bai, Jianwei; Chi, Minglu; Cheng, Cunxin; Wang, Dianlong

2014-09-01

341

Population size and migration of Anopheles gambiae in the Bancoumana Region of Mali and their significance for efficient vector control.  

PubMed

We present results of two intensive mark-release-recapture surveys conducted during the wet and dry seasons of 2008 in the villages of Fourda and Kenieroba, Mali. The former is a small fishing village by the Niger River with a moderate to high densities of Anopheles gambiae Giles s.s. (Diptera: Culicidae) throughout the year, while the latter is a large agricultural community 2 km inland that experiences strong seasonal fluctuation in An. gambiae densities. We estimate the population size of female An. gambiae in Fourda to be in less than 3,000 during the dry season. We found evidence of large population size and migration from Fourda in Kenieroba during the wet season, but very low numbers and no sign of migrants during the dry season. We suggest that malaria vector control measures aimed at adult mosquitoes might be made more efficient in this region and other seasonal riparian habitats by targeting disruption of mosquito populations by the river during the dry season. This would decrease the size of an already small population, and would be likely to delay the explosive growth in vector numbers in the larger inland villages as rainfall increases. PMID:20422013

Baber, Ibrahima; Keita, Moussa; Sogoba, Nafomon; Konate, Mamadou; Diallo, M'Bouye; Doumbia, Seydou; Traoré, Sékou F; Ribeiro, José M C; Manoukis, Nicholas C

2010-01-01

342

Population Size and Migration of Anopheles gambiae in the Bancoumana Region of Mali and Their Significance for Efficient Vector Control  

PubMed Central

We present results of two intensive mark-release-recapture surveys conducted during the wet and dry seasons of 2008 in the villages of Fourda and Kenieroba, Mali. The former is a small fishing village by the Niger River with a moderate to high densities of Anopheles gambiae Giles s.s. (Diptera: Culicidae) throughout the year, while the latter is a large agricultural community 2 km inland that experiences strong seasonal fluctuation in An. gambiae densities. We estimate the population size of female An. gambiae in Fourda to be in less than 3,000 during the dry season. We found evidence of large population size and migration from Fourda in Kenieroba during the wet season, but very low numbers and no sign of migrants during the dry season. We suggest that malaria vector control measures aimed at adult mosquitoes might be made more efficient in this region and other seasonal riparian habitats by targeting disruption of mosquito populations by the river during the dry season. This would decrease the size of an already small population, and would be likely to delay the explosive growth in vector numbers in the larger inland villages as rainfall increases. PMID:20422013

Baber, Ibrahima; Keita, Moussa; Sogoba, Nafomon; Konate, Mamadou; Diallo, M'Bouye; Doumbia, Seydou; Traoré, Sékou F.; Ribeiro, José M. C.; Manoukis, Nicholas C.

2010-01-01

343

Receding Horizon Control of a Vectored Thrust Flight Experiment Mark B. Milam Ryan Franz  

E-print Network

, computational method developed and implemented by Milam et al., that combines nonlinear control theory, B-spline convergent stability if not implemented properly. These difficulties have largely prevented its application for a good review of recent work in this field. To implement the receding horizon control strategy

Murray, Richard M.

344

West-African trypanosomiasis in a returned traveller from Ghana: an unusual cause of progressive neurological decline.  

PubMed

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. PMID:25123570

Elliott, Ivo; Patel, Trupti; Shah, Jagrit; Venkatesan, Pradhib

2014-01-01

345

False Positivity of Non-Targeted Infections in Malaria Rapid Diagnostic Tests: The Case of Human African Trypanosomiasis  

PubMed Central

Background In endemic settings, diagnosis of malaria increasingly relies on the use of rapid diagnostic tests (RDTs). False positivity of such RDTs is poorly documented, although it is especially relevant in those infections that resemble malaria, such as human African trypanosomiasis (HAT). We therefore examined specificity of malaria RDT products among patients infected with Trypanosoma brucei gambiense. Methodology/Principal Findings Blood samples of 117 HAT patients and 117 matched non-HAT controls were prospectively collected in the Democratic Republic of the Congo. Reference malaria diagnosis was based on real-time PCR. Ten commonly used malaria RDT products were assessed including three two-band and seven three-band products, targeting HRP-2, Pf-pLDH and/or pan-pLDH antigens. Rheumatoid factor was determined in PCR negative subjects. Specificity of the 10 malaria RDT products varied between 79.5 and 100% in HAT-negative controls and between 11.3 and 98.8% in HAT patients. For seven RDT products, specificity was significantly lower in HAT patients compared to controls. False positive reactions in HAT were mainly observed for pan-pLDH test lines (specificities between 13.8 and 97.5%), but also occurred frequently for the HRP-2 test line (specificities between 67.9 and 98.8%). The Pf-pLDH test line was not affected by false-positive lines in HAT patients (specificities between 97.5 and 100%). False positivity was not associated to rheumatoid factor, detected in 7.6% of controls and 1.2% of HAT patients. Conclusions/Significance Specificity of some malaria RDT products in HAT was surprisingly low, and constitutes a risk for misdiagnosis of a fatal but treatable infection. Our results show the importance to assess RDT specificity in non-targeted infections when evaluating diagnostic tests. PMID:23638201

Gillet, Philippe; Mumba Ngoyi, Dieudonné; Lukuka, Albert; Kande, Viktor; Atua, Benjamin; van Griensven, Johan; Muyembe, Jean-Jacques; Jacobs, Jan; Lejon, Veerle

2013-01-01

346

A Randomized Longitudinal Factorial Design to Assess Malaria Vector Control and Disease Management Interventions in Rural Tanzania  

PubMed Central

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. PMID:24840349

Kramer, Randall A.; Mboera, Leonard E. G.; Senkoro, Kesheni; Lesser, Adriane; Shayo, Elizabeth H.; Paul, Christopher J.; Miranda, Marie Lynn

2014-01-01

347

A randomized longitudinal factorial design to assess malaria vector control and disease management interventions in rural Tanzania.  

PubMed

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. PMID:24840349

Kramer, Randall A; Mboera, Leonard E G; Senkoro, Kesheni; Lesser, Adriane; Shayo, Elizabeth H; Paul, Christopher J; Miranda, Marie Lynn

2014-05-01

348

Flight-Determined Subsonic Longitudinal Stability and Control Derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) with Thrust Vectoring  

NASA Technical Reports Server (NTRS)

The subsonic longitudinal stability and control derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) are extracted from dynamic flight data using a maximum likelihood parameter identification technique. The technique uses the linearized aircraft equations of motion in their continuous/discrete form and accounts for state and measurement noise as well as thrust-vectoring effects. State noise is used to model the uncommanded forcing function caused by unsteady aerodynamics over the aircraft, particularly at high angles of attack. Thrust vectoring was implemented using electrohydraulically-actuated nozzle postexit vanes and a specialized research flight control system. During maneuvers, a control system feature provided independent aerodynamic control surface inputs and independent thrust-vectoring vane inputs, thereby eliminating correlations between the aircraft states and controls. Substantial variations in control excitation and dynamic response were exhibited for maneuvers conducted at different angles of attack. Opposing vane interactions caused most thrust-vectoring inputs to experience some exhaust plume interference and thus reduced effectiveness. The estimated stability and control derivatives are plotted, and a discussion relates them to predicted values and maneuver quality.

Iliff, Kenneth W.; Wang, Kon-Sheng Charles

1997-01-01

349

Dynamics of the “Popcorn” Wolbachia Infection in Outbred Aedes aegypti Informs Prospects for Mosquito Vector Control  

PubMed Central

Forty percent of the world's population is at risk of contracting dengue virus, which produces dengue fever with a potentially fatal hemorrhagic form. The wMelPop Wolbachia infection of Drosophila melanogaster reduces life span and interferes with viral transmission when introduced into the mosquito Aedes aegypti, the primary vector of dengue virus. Wolbachia has been proposed as an agent for preventing transmission of dengue virus. Population invasion by Wolbachia depends on levels of cytoplasmic incompatibility, fitness effects, and maternal transmission. Here we characterized these traits in an outbred genetic background of a potential target population of Ae. aegypti using two crossing schemes. Cytoplasmic incompatibility was strong in this background, and the maternal transmission rate of Wolbachia was high. The infection substantially reduced longevity of infected adult females, regardless of whether adults came from larvae cultured under high or low levels of nutrition or density. The infection reduced the viability of diapausing and nondiapausing eggs. Viability was particularly low when eggs were laid by older females and when diapausing eggs had been stored for a few weeks. The infection affected mosquito larval development time and adult body size under different larval nutrition levels and densities. The results were used to assess the potential for wMelPop-CLA to invade natural populations of Ae. aegypti and to develop recommendations for the maintenance of fitness in infected mosquitoes that need to compete against field insects. PMID:21135075

Yeap, H. L.; Mee, P.; Walker, T.; Weeks, A. R.; O'Neill, S. L.; Johnson, P.; Ritchie, S. A.; Richardson, K. M.; Doig, C.; Endersby, N. M.; Hoffmann, A. A.

2011-01-01

350

Harmonic domain modelling of three phase thyristor-controlled reactors by means of switching vectors and discrete convolutions  

SciTech Connect

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.

Rico, J.J.; Acha, E.; Miller, T.J.E. [Univ. of Glasgow (United Kingdom). Dept. of Electronics and Electrical Engineering] [Univ. of Glasgow (United Kingdom). Dept. of Electronics and Electrical Engineering

1996-07-01

351

Monitoring of larval habitats and mosquito densities in the Sudan savanna of Mali: implications for malaria vector control.  

PubMed

In Mali, anopheline mosquito populations increase sharply during the rainy season, but are barely detectable in the dry season. This study attempted to identify the dry season mosquito breeding population in and near the village of Bancoumana, Mali, and in a fishing hamlet 5 km from this village and adjacent to the Niger River. In Bancoumana, most larval habitats were human made, and dried out in January-February. In contrast, in the fishing hamlet, productive larval habitats were numerous and found mainly during the dry season (January-May) as the natural result of drying riverbeds. Adult mosquitoes were abundant during the dry season in the fishermen hamlet and rare in Bancoumana. To the extent that the fishermen hamlet mosquito population seeds Bancoumana with the advent of the rainy season, vector control in this small hamlet may be a cost-effective way to ameliorate malaria transmission in the 40-times larger village. PMID:17620634

Sogoba, Nafomon; Doumbia, Seydou; Vounatsou, Penelope; Baber, Ibrahima; Keita, Moussa; Maiga, Mamoudou; Traoré, Sékou F; Touré, Abdoulaye; Dolo, Guimogo; Smith, Thomas; Ribeiro, José M C

2007-07-01

352

Spatial Orientation and Balance Control Changes Induced by Altered Gravito-Inertial Force Vectors  

NASA Technical Reports Server (NTRS)

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-tilt during 90 minutes of both tilt and centrifugation stimuli. Subjective estimates of head-horizontal, provided by directed saccades, revealed significant errors after approximately 30 minutes that tended to increase only in the group who underwent centrifugation. Immediately after centrifugation, subjects reported feeling tilted on average 10 degrees in the opposite direction, which was in agreement with the direction of their earth-directed saccades. In vestibular deficient (VD) subjects, postural sway was measured using a sway-referenced or earth-fixed support surface, and with or without a head movement sequence. 'Me protocol was selected for each patient during baseline testing, and corresponded to the most challenging condition in which the patient was able to maintain balance with eyes closed. Bilaterally VD subjects showed no postural decrement after centrifugation, while unilateral VD subjects had varying degrees of decrement. Unilateral VD subjects were tested twice; they underwent centrifugation both with right ear out and left ear out. Their post-centrifuation center of sway shifted at right angles depending on the centrifuge GIF orientation. Bilateral VD subjects bad shifts as well, but no consistent directional trend. VD subjects underestimated roll-tilt during centrifugation, These results suggest that orientation of the gravito-inertial vector and its magnitude arc both used by the central nervous system for calibration of multiple orientation systems. A change in the background gravito-inertial force (otolith input) can rapidly initiate postural and perceptual adaptation in several sensorimotor systems, independent of a structured visual surround.

Kaufman, Galen D.; Wood, Scott J.; Gianna, Claire C.; Black, F. Owen; Paloski, William H.; Dawson, David L. (Technical Monitor)

1999-01-01

353

Insecticide resistance in Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Anopheles gambiae Giles (Diptera: Culicidae) could compromise the sustainability of malaria vector control strategies in West Africa.  

PubMed

Insecticides from the organophosphate (OP) and pyrethroid (PY) chemical families, have respectively, been in use for 50 and 30 years in West Africa, mainly against agricultural pests, but also against vectors of human disease. The selection pressure, with practically the same molecules year after year (mainly on cotton), has caused insecticide resistance in pest populations such as Bemisia tabaci, vector of harmful phytoviruses on vegetables. The evolution toward insecticide resistance in malaria vectors such as Anopheles gambiae sensus lato (s.l.) is probably related to the current use of these insecticides in agriculture. Thus, successful pest and vector control in West Africa requires an investigation of insect susceptibility, in relation to the identification of species and sub species, such as molecular forms or biotypes. Identification of knock down resistance (kdr) and acetylcholinesterase gene (Ace1) mutations modifying insecticide targets in individual insects and measure of enzymes activity typically involved in insecticide metabolism (oxidase, esterase and glutathion-S-transferase) are indispensable in understanding the mechanisms of resistance. Insecticide resistance is a good example in which genotype-phenotype links have been made successfully. Insecticides used in agriculture continue to select new resistant populations of B. tabaci that could be from different biotype vectors of plant viruses. As well, the evolution of insecticide resistance in An. gambiae threatens the management of malaria vectors in West Africa. It raises the question of priority in the use of insecticides in health and/or agriculture, and more generally, the question of sustainability of crop protection and vector control strategies in the region. Here, we review the susceptibility tests, biochemical and molecular assays data for B. tabaci, a major pest in cotton and vegetable crops, and An. gambiae, main vector of malaria. The data reviewed was collected in Benin and Burkina Faso between 2008 and 2010 under the Corus 6015 research program. This review aims to show: (i) the insecticide resistance in B. tabaci as well as in An. gambiae; and (ii) due to this, the impact of selection of resistant populations on malaria vector control strategies. Some measures that could be beneficial for crop protection and vector control strategies in West Africa are proposed. PMID:23792227

Gnankiné, Olivier; Bassolé, Imael H N; Chandre, Fabrice; Glitho, Isabelle; Akogbeto, Martin; Dabiré, Roch K; Martin, Thibaud

2013-10-01

354

Design Specification for a Thrust-Vectoring, Actuated-Nose-Strake Flight Control Law for the High-Alpha Research Vehicle  

NASA Technical Reports Server (NTRS)

Specifications for a flight control law are delineated in sufficient detail to support coding the control law in flight software. This control law was designed for implementation and flight test on the High-Alpha Research Vehicle (HARV), which is an F/A-18 aircraft modified to include an experimental multi-axis thrust-vectoring system and actuated nose strakes for enhanced rolling (ANSER). The control law, known as the HARV ANSER Control Law, was designed to utilize a blend of conventional aerodynamic control effectors, thrust vectoring, and actuated nose strakes to provide increased agility and good handling qualities throughout the HARV flight envelope, including angles of attack up to 70 degrees.

Bacon, Barton J.; Carzoo, Susan W.; Davidson, John B.; Hoffler, Keith D.; Lallman, Frederick J.; Messina, Michael D.; Murphy, Patrick C.; Ostroff, Aaron J.; Proffitt, Melissa S.; Yeager, Jessie C.; Foster, John V.; Bundick, W. Thomas; Connelly, Patrick J.; Kelly, John W.; Pahle, Joseph W.; Thomas, Michael; Wichman, Keith D.; Wilson, R. Joseph

1996-01-01

355

The fog of war: why the environmental crusade for anadromous fish species in California could disarm the state's local vector control districts in their war against mosquitoes.  

PubMed

In California, local mosquito and vector control districts have successfully controlled mosquito and vector-borne diseases by improving drainage patterns and applying pesticides. The Bay-Delta Conservation Plan, which is a proposed habitat conservation plan for the Sacramento-San Joaquin Bay-Delta estuary, proposes to add over 70,000 acres of habitat in the Delta to improve conditions for threatened and endangered aquatic and terrestrial species. This habitat could also be a suitable mosquito breeding habitat, which will be located in close proximity to urban and suburban communities. Wetland management practices and continued pesticide applications in the Delta could mitigate the effects of a new mosquito breeding habitat. Recent legal developments, however, require districts to obtain and comply with Clean Water Act permits, which restrict the application of pesticides in or near waters of the United States. Moreover, the U.S. Environmental Protection Agency has taken the first step in a rulemaking process that could further limit or prohibit the use of certain vector control pesticides in the Delta. In the near term and until less harmful methods for mosquito control are available, local vector control districts' application of mosquito control pesticides should be exempt from Clean Water Act permit requirements. PMID:23856372

Siptroth, Stephen M; Shanahan, Richard P

2011-12-01

356

Development and evaluation of a pyriproxyfen-treated device to control the dengue vector, Aedes aegypti (L.) (Diptera:Culicidae).  

PubMed

The resurgence of dengue fever and the chikungunya epidemic make the control of Aedes aegypti mosquitoes, the vectors of these diseases, critically important. We developed and evaluated an Ae. aegypti control device that is visually-attractive to mosquitoes. This pyriproxyfen-treated device was evaluated for its impact on Ae. aegypti egg production and population dynamics in dengue-endemic areas in Thailand. The device consists of a "high rise" shaped ovitrap/ resting station covered with black cotton cloth. The device is easily collapsible and transportable. Ae. aegypti are generally drawn towards darker, shadier areas making this device physically attractive as a resting station to mosquitoes of all physiological stages. The results show this device suppressed Ae. aegypti populations after it was introduced into a village. The observed effect was primarily the result of the Ae. aegypti exposure to pyriproxyfen shortly after adult emergence or after taking a blood meal resulting in decreased egg production. We believe the device may be further improved physically and the formulation should be replaced to provide even better efficacy for controlling Ae. aegypti mosquito, populations. PMID:23691625

Ponlawat, Alongkot; Fansiri, Thanyalak; Kurusarttra, Somwang; Pongsiri, Arissara; McCardle, Patrick W; Evans, Brian P; Evans, Brain P; Richardson, Jason H

2013-03-01

357

Made-to-measure malaria vector control strategies: rational design based on insecticide properties and coverage of blood resources for mosquitoes.  

PubMed

Eliminating malaria from highly endemic settings will require unprecedented levels of vector control. To suppress mosquito populations, vector control products targeting their blood hosts must attain high biological coverage of all available sources, rather than merely high demographic coverage of a targeted resource subset, such as humans while asleep indoors. Beyond defining biological coverage in a measurable way, the proportion of blood meals obtained from humans and the proportion of bites upon unprotected humans occurring indoors also suggest optimal target product profiles for delivering insecticides to humans or livestock. For vectors that feed only occasionally upon humans, preferred animal hosts may be optimal targets for mosquito-toxic insecticides, and vapour-phase insecticides optimized to maximize repellency, rather than toxicity, may be ideal for directly protecting people against indoor and outdoor exposure. However, for vectors that primarily feed upon people, repellent vapour-phase insecticides may be inferior to toxic ones and may undermine the impact of contact insecticides applied to human sleeping spaces, houses or clothing if combined in the same time and place. These concepts are also applicable to other mosquito-borne anthroponoses so that diverse target species could be simultaneously controlled with integrated vector management programmes. Measurements of these two crucial mosquito behavioural parameters should now be integrated into programmatically funded, longitudinal, national-scale entomological monitoring systems to inform selection of available technologies and investment in developing new ones. PMID:24739261

Killeen, Gerry F; Seyoum, Aklilu; Gimnig, John E; Stevenson, Jennifer C; Drakeley, Christopher J; Chitnis, Nakul

2014-01-01

358

Made-to-measure malaria vector control strategies: rational design based on insecticide properties and coverage of blood resources for mosquitoes  

PubMed Central

Eliminating malaria from highly endemic settings will require unprecedented levels of vector control. To suppress mosquito populations, vector control products targeting their blood hosts must attain high biological coverage of all available sources, rather than merely high demographic coverage of a targeted resource subset, such as humans while asleep indoors. Beyond defining biological coverage in a measurable way, the proportion of blood meals obtained from humans and the proportion of bites upon unprotected humans occurring indoors also suggest optimal target product profiles for delivering insecticides to humans or livestock. For vectors that feed only occasionally upon humans, preferred animal hosts may be optimal targets for mosquito-toxic insecticides, and vapour-phase insecticides optimized to maximize repellency, rather than toxicity, may be ideal for directly protecting people against indoor and outdoor exposure. However, for vectors that primarily feed upon people, repellent vapour-phase insecticides may be inferior to toxic ones and may undermine the impact of contact insecticides applied to human sleeping spaces, houses or clothing if combined in the same time and place. These concepts are also applicable to other mosquito-borne anthroponoses so that diverse target species could be simultaneously controlled with integrated vector management programmes. Measurements of these two crucial mosquito behavioural parameters should now be integrated into programmatically funded, longitudinal, national-scale entomological monitoring systems to inform selection of available technologies and investment in developing new ones. PMID:24739261

2014-01-01

359

Review article Trypanosoma cruzi: adaptation to its vectors and its hosts  

E-print Network

2009) Abstract ­ American trypanosomiasis is a parasitic zoonosis that occurs throughout Latin America knowledge of the different components involved in elaborate system that is American trypanosomiasis (the

Paris-Sud XI, Université de

360

VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE, REPELLENTS Impact of Inorganic Pollutants Perchlorate and Hexavalent Chromium  

E-print Network

and Hexavalent Chromium on Efficacy of Bacillus sphaericus and Bacillus thuringiensis subsp. israelensis Against assessed on the efÃ?cacy of Bacillus thuringiensis subsp. israelensis (Bti) and Bacillus sphaericus (Bsph, Bacillus thuringiensis subsp. israelensis (Bti) and Bacillus sphaericus (Bsph) are commonly used control

Trumble, John T.

361

Spray characterization of thermal fogging equipment typically used in vector control  

Technology Transfer Automated Retrieval System (TEKTRAN)

The generation of insecticide laden fogs provides an effective method for controlling flying insects. One of the critical factors affecting the effectiveness of a thermal fogging application is the generation of droplets that will remain aloft in the fogging cloud and moves into the area where the ...

362

Sensorless vector control of PMSG for variable speed wind energy applications  

Microsoft Academic Search

This paper presents a sensorless control scheme for a permanent magnet synchronous generator (PMSG) in variable speed wind energy conversion system (WECS) applications. The rotor speed is estimated using recursive least square estimation (RLSE) algorithm using a simple equation which requires only the knowledge of rotor flux. A programmable low pass filter (PLPF) is implemented to obtain the rotor flux.

J. S. Thongam; P. Bouchard; V. Giurgiu; H. T. Bui; M. Ouhrouche

2010-01-01

363

IEEE Transactions on Evolutionary Computation 1 Abstract--Trial vector generation strategies and control  

E-print Network

, that these experiences have not yet systematically exploited in DE algorithm design. This motivates us to study whether generation strategies with some suitable control parameter settings. A novel method, called composite DE (Co is often very time-consuming, there has been an increasing interest in designing new DE variants

Zhang, Qingfu

364

Sustained Reduction of the Dengue Vector Population Resulting from an Integrated Control Strategy Applied in Two Brazilian Cities  

PubMed Central

Aedes aegypti has developed evolution-driven adaptations for surviving in the domestic human habitat. Several trap models have been designed considering these strategies and tested for monitoring this efficient vector of Dengue. Here, we report a real-scale evaluation of a system for monitoring and controlling mosquito populations based on egg sampling coupled with geographic information systems technology. The SMCP-Aedes, a system based on open technology and open data standards, was set up from March/2008 to October/2011 as a pilot trial in two sites of Pernambuco -Brazil: Ipojuca (10,000 residents) and Santa Cruz (83,000), in a joint effort of health authorities and staff, and a network of scientists providing scientific support. A widespread infestation by Aedes was found in both sites in 2008–2009, with 96.8%–100% trap positivity. Egg densities were markedly higher in SCC than in Ipojuca. A 90% decrease in egg density was recorded in SCC after two years of sustained control pressure imposed by suppression of >7,500,000 eggs and >3,200 adults, plus larval control by adding fishes to cisterns. In Ipojuca, 1.1 million mosquito eggs were suppressed and a 77% reduction in egg density was achieved. This study aimed at assessing the applicability of a system using GIS and spatial statistic analysis tools for quantitative assessment of mosquito populations. It also provided useful information on the requirements for reducing well-established mosquito populations. Results from two cities led us to conclude that the success in markedly reducing an Aedes population required the appropriate choice of control measures for sustained mass elimination guided by a user-friendly mosquito surveillance system. The system was able to support interventional decisions and to assess the program’s success. Additionally, it created a stimulating environment for health staff and residents, which had a positive impact on their commitment to the dengue control program. PMID:23844059

Regis, Lêda N.; Acioli, Ridelane Veiga; Silveira, José Constantino; Melo-Santos, Maria Alice Varjal; Souza, Wayner Vieira; Ribeiro, Cândida M. Nogueira.; da Silva, Juliana C. Serafim.; Monteiro, Antonio Miguel Vieira; Oliveira, Cláudia M. F.; Barbosa, Rosângela M. R.; Braga, Cynthia; Rodrigues, Marco Aurélio Benedetti; Silva, Marilú Gomes N. M.; Ribeiro Jr., Paulo Justiniano; Bonat, Wagner Hugo; de Castro Medeiros, Liliam César; Carvalho, Marilia Sa; Furtado, André Freire

2013-01-01

365

Sustained reduction of the dengue vector population resulting from an integrated control strategy applied in two Brazilian cities.  

PubMed

Aedes aegypti has developed evolution-driven adaptations for surviving in the domestic human habitat. Several trap models have been designed considering these strategies and tested for monitoring this efficient vector of Dengue. Here, we report a real-scale evaluation of a system for monitoring and controlling mosquito populations based on egg sampling coupled with geographic information systems technology. The SMCP-Aedes, a system based on open technology and open data standards, was set up from March/2008 to October/2011 as a pilot trial in two sites of Pernambuco -Brazil: Ipojuca (10,000 residents) and Santa Cruz (83,000), in a joint effort of health authorities and staff, and a network of scientists providing scientific support. A widespread infestation by Aedes was found in both sites in 2008-2009, with 96.8%-100% trap positivity. Egg densities were markedly higher in SCC than in Ipojuca. A 90% decrease in egg density was recorded in SCC after two years of sustained control pressure imposed by suppression of >7,500,000 eggs and >3,200 adults, plus larval control by adding fishes to cisterns. In Ipojuca, 1.1 million mosquito eggs were suppressed and a 77% reduction in egg density was achieved. This study aimed at assessing the applicability of a system using GIS and spatial statistic analysis tools for quantitative assessment of mosquito populations. It also provided useful information on the requirements for reducing well-established mosquito populations. Results from two cities led us to conclude that the success in markedly reducing an Aedes population required the appropriate choice of control measures for sustained mass elimination guided by a user-friendly mosquito surveillance system. The system was able to support interventional decisions and to assess the program's success. Additionally, it created a stimulating environment for health staff and residents, which had a positive impact on their commitment to the dengue control program. PMID:23844059

Regis, Lêda N; Acioli, Ridelane Veiga; Silveira, José Constantino; Melo-Santos, Maria Alice Varjal; Souza, Wayner Vieira; Ribeiro, Cândida M Nogueira; da Silva, Juliana C Serafim; Monteiro, Antonio Miguel Vieira; Oliveira, Cláudia M F; Barbosa, Rosângela M R; Braga, Cynthia; Rodrigues, Marco Aurélio Benedetti; Silva, Marilú Gomes N M; Ribeiro, Paulo Justiniano; Bonat, Wagner Hugo; de Castro Medeiros, Liliam César; Carvalho, Marilia Sa; Furtado, André Freire

2013-01-01

366

Pathophysiology of ovine trypanosomiasis: ferrokinetics and erythrocyte survival studies.  

PubMed

The haematological changes, erythrokinetics and ferrokinetics of sheep were investigated after infection with Trypanosoma congolense. Following the detection of parasites in blood, the infected sheep developed macrocytic hypochromic anaemia. Studies with 51Cr-red cells, 125I-albumin and 59Fe as ferric citrate 11 weeks after infection revealed that infected sheep had significantly lower mean circulating red cell volumes but higher plasma and blood volumes than control sheep. The infected sheep also had enhanced erythropoietic activity as judged by significantly higher plasma iron turnover rates, faster disappearance of radio-labelled iron and higher iron incorporation rates than control sheep. The rate of disappearance of 51Cr-labelled red cells was greater in infected than in control sheep. It was concluded that the anaemia observed at this stage of infection was due to an increased rate of removal of red cells from the circulation coupled with haemodilution, with no evidence of dyshaemopoiesis. PMID:1410823

Katunguka-Rwakishaya, E; Murray, M; Holmes, P H

1992-07-01

367

Geostatistical evaluation of integrated marsh management impact on mosquito vectors using before-after-control-impact (BACI) design  

PubMed Central

Background In many parts of the world, salt marshes play a key ecological role as the interface between the marine and the terrestrial environments. Salt marshes are also exceedingly important for public health as larval habitat for mosquitoes that are vectors of disease and significant biting pests. Although grid ditching and pesticides have been effective in salt marsh mosquito control, marsh degradation and other environmental considerations compel a different approach. Targeted habitat modification and biological control methods known as Open Marsh Water Management (OMWM) had been proposed as a viable alternative to marsh-wide physical alterations and chemical control. However, traditional larval sampling techniques may not adequately assess the impacts of marsh management on mosquito larvae. To assess the effectiveness of integrated OMWM and marsh restoration techniques for mosquito control, we analyzed the results of a 5-year OMWM/marsh restoration project to determine changes in mosquito larval production using GIS and geostatistical methods. Methods The following parameters were evaluated using "Before-After-Control-Impact" (BACI) design: frequency and geographic extent of larval production, intensity of larval production, changes in larval habitat, and number of larvicide applications. The analyses were performed using Moran's I, Getis-Ord, and Spatial Scan statistics on aggregated before and after data as well as data collected over time. This allowed comparison of control and treatment areas to identify changes attributable to the OMWM/marsh restoration modifications. Results The frequency of finding mosquito larvae in the treatment areas was reduced by 70% resulting in a loss of spatial larval clusters compared to those found in the control areas. This effect was observed directly following OMWM treatment and remained significant throughout the study period. The greatly reduced frequency of finding larvae in the treatment areas led to a significant decrease (~44%) in the number of times when the larviciding threshold was reached. This reduction, in turn, resulted in a significant decrease (~74%) in the number of larvicide applications in the treatment areas post-project. The remaining larval habitat in the treatment areas had a different geographic distribution and was largely confined to the restored marsh surface (i.e. filled-in mosquito ditches); however only ~21% of the restored marsh surface supported mosquito production. Conclusion The geostatistical analysis showed that OMWM demonstrated considerable potential for effective mosquito control and compatibility with other natural resource management goals such as restoration, wildlife habitat enhancement, and invasive species abatement. GPS and GIS tools are invaluable for large scale project design, data collection, and data analysis, with geostatistical methods serving as an alternative or a supplement to the conventional inference statistics in evaluating the project outcome. PMID:19549297

Rochlin, Ilia; Iwanejko, Tom; Dempsey, Mary E; Ninivaggi, Dominick V

2009-01-01

368

Chagas Disease Vector Control in a Hyperendemic Setting: The First 11 Years of Intervention in Cochabamba, Bolivia  

PubMed Central

Background Chagas disease has historically been hyperendemic in the Bolivian Department of Cochabamba. In the early 2000s, an extensive vector control program was implemented; 1.34 million dwelling inspections were conducted to ascertain infestation (2000–2001/2003–2011), with blanket insecticide spraying in 2003–2005 and subsequent survey-spraying cycles targeting residual infestation foci. Here, we assess the effects of this program on dwelling infestation rates (DIRs). Methodology/Principal Findings Program records were used to calculate annual, municipality-level aggregate DIRs (39 municipalities); very high values in 2000–2001 (median: 0.77–0.69) dropped to ?0.03 from 2004 on. A linear mixed model (with municipality as a random factor) suggested that infestation odds decreased, on average, by ?28% (95% confidence interval [CI95] 6–44%) with each 10-fold increase in control effort. A second, better-fitting mixed model including year as an ordinal predictor disclosed large DIR reductions in 2001–2003 (odds ratio [OR] 0.11, CI95 0.06–0.19) and 2003–2004 (OR 0.22, CI95 0.14–0.34). Except for a moderate decrease in 2005–2006, no significant changes were detected afterwards. In both models, municipality-level DIRs correlated positively with previous-year DIRs and with the extent of municipal territory originally covered by montane dry forests. Conclusions/Significance Insecticide-spraying campaigns had very strong, long-lasting effects on DIRs in Cochabamba. However, post-intervention surveys consistently detected infestation in ?3% of dwellings, underscoring the need for continuous surveillance; higher DIRs were recorded in the capital city and, more generally, in municipalities dominated by montane dry forest – an eco-region where wild Triatoma infestans are widespread. Traditional strategies combining insecticide spraying and longitudinal surveillance are thus confirmed as very effective means for area-wide Chagas disease vector control; they will be particularly beneficial in highly-endemic settings, but should also be implemented or maintained in other parts of Latin America where domestic infestation by triatomines is still commonplace. PMID:24699407

Espinoza, Natalisisy; Borrás, Rafael; Abad-Franch, Fernando

2014-01-01

369

Parasite Prolyl Oligopeptidases and the Challenge of Designing Chemotherapeuticals for Chagas Disease, Leishmaniasis and African Trypanosomiasis  

PubMed Central

The trypanosomatids Trypanosoma cruzi, Leishmania spp. and Trypanosoma brucei spp. cause Chagas disease, leishmaniasis and human African trypanosomiasis, respectively. It is estimated that over 10 million people worldwide suffer from these neglected diseases, posing enormous social and economic problems in endemic areas. There are no vaccines to prevent these infections and chemotherapies are not adequate. This picture indicates that new chemotherapeutic agents must be developed to treat these illnesses. For this purpose, understanding the biology of the pathogenic trypanosomatid-host cell interface is fundamental for molecular and functional characterization of virulence factors that may be used as targets for the development of inhibitors to be used for effective chemotherapy. In this context, it is well known that proteases have crucial functions for both metabolism and infectivity of pathogens and are thus potential drug targets. In this regard, prolyl oligopeptidase and oligopeptidase B, both members of the S9 serine protease family, have been shown to play important roles in the interactions of pathogenic protozoa with their mammalian hosts and may thus be considered targets for drug design. This review aims to discuss structural and functional properties of these intriguing enzymes and their potential as targets for the development of drugs against Chagas disease, leishmaniasis and African trypanosomiasis. PMID:23514419

Bastos, I.M.D; Motta, F.N; Grellier, P; Santana, J.M

2013-01-01

370

Closed-Loop Simulation Study of the Ares I Upper Stage Thrust Vector Control Subsystem for Nominal and Failure Scenarios  

NASA Technical Reports Server (NTRS)

As a replacement to the current Shuttle, the Ares I rocket and Orion crew module are currently under development by the National Aeronautics and Space Administration (NASA). This new launch vehicle is segmented into major elements, one of which is the Upper Stage (US). The US is further broken down into subsystems, one of which is the Thrust Vector Control (TVC) subsystem which gimbals the US rocket nozzle. Nominal and off-nominal simulations for the US TVC subsystem are needed in order to support the development of software used for control systems and diagnostics. In addition, a clear and complete understanding of the effect of off-nominal conditions on the vehicle flight dynamics is desired. To achieve these goals, a simulation of the US TVC subsystem combined with the Ares I vehicle as developed. This closed-loop dynamic model was created using Matlab s Simulink and a modified version of a vehicle simulation, MAVERIC, which is currently used in the Ares I project and was developed by the Marshall Space Flight Center (MSFC). For this report, the effects on the flight trajectory of the Ares I vehicle are investigated after failures are injected into the US TVC subsystem. The comparisons of the off-nominal conditions observed in the US TVC subsystem with those of the Ares I vehicle flight dynamics are of particular interest.

Chicatelli, Amy; Fulton, Chris; Connolly, Joe; Hunker, Keith

2010-01-01

371

Drug Discovery for Human African Trypanosomiasis: Identification of Novel Scaffolds by the Newly Developed HTS SYBR Green Assay for Trypanosoma brucei.  

PubMed

Human African trypanosomiasis (HAT) is a vector-transmitted tropical disease caused by the protozoan parasite Trypanosoma brucei. High-throughput screening (HTS) of small-molecule libraries in whole-cell assays is one of the most frequently used approaches in drug discovery for infectious diseases. To aid in drug discovery efforts for HAT, the SYBR Green assay was developed for T. brucei in a 384-well format. This semi-automated assay is cost- and time-effective, robust, and reproducible. The SYBR Green assay was compared to the resazurin assay by screening a library of 4000 putative kinase inhibitors, revealing a superior performance in terms of assay time, sensitivity, simplicity, and reproducibility, and resulting in a higher hit confirmation rate. Although the resazurin assay allows for comparatively improved detection of slow-killing compounds, it also has higher false-positive rates that are likely to arise from the assay experimental conditions. The compounds with the most potent antitrypanosomal activity were selected in both screens and grouped into 13 structural clusters, with 11 new scaffolds as antitrypanosomal agents. Several of the identified compounds had IC50 <1 µM coupled with high selectivity toward the parasite. The core structures of the scaffolds are shown, providing promising new starting points for drug discovery for HAT. PMID:25342146

Faria, Joana; Moraes, Carolina B; Song, Rita; Pascoalino, Bruno S; Lee, Nakyung; Siqueira-Neto, Jair L; Cruz, Deu John M; Parkinson, Tanya; Ioset, Jean-Robert; Cordeiro-da-Silva, Anabela; Freitas-Junior, Lucio H

2015-01-01

372

Outdoor host seeking behaviour of Anopheles gambiae mosquitoes following initiation of malaria vector control on Bioko Island, Equatorial Guinea  

Microsoft Academic Search

Background  Indoor-based anti-vector interventions remain the preferred means of reducing risk of malaria transmission in malaria endemic\\u000a areas around the world. Despite demonstrated success in reducing human-mosquito interactions, these methods are effective\\u000a solely against endophilic vectors. It may be that outdoor locations serve as an important venue of host seeking by Anopheles gambiae sensu lato (s.l.) mosquitoes where indoor vector suppression

Michael R Reddy; Hans J Overgaard; Simon Abaga; Vamsi P Reddy; Adalgisa Caccone; Anthony E Kiszewski; Michel A Slotman

2011-01-01

373

Value of the indirect fluorescent antibody test as a serological aid to diagnosis of glossina -transmitted bovine trypanosomiasis  

Microsoft Academic Search

Four hundred and sixty seven cattle were sampled for the presence of trypanosomiasis in two distinct areas of Eastern Uganda. Using sera collected, the agglutination test and two types of indirect fluorescent antibody test were used to examine their value as serological aids to diagnosis. The agglutination test was considered to be of limited use. The indirect fluorescent antibody tests

A. J. Wilson

1969-01-01

374

Molecular epidemiology of American trypanosomiasis in Brazil based on dimorphisms of rRNA and mini-exon gene sequences  

Microsoft Academic Search

American trypanosomiasis is transmitted in nature via a sylvatic cycle, where Trypanosoma cruzi interacts with wild triatomines and mammalian reservoirs, or via a domestic cycle where the parasite comes into contact with humans through domiciliated triatomines. The pool of T. cruzi isolates consists of sub-populations presenting a broad genetic diversity. In contrast to the heterogeneity suggested by isoenzyme analysis, PCR

B. Zingales; R. P. Souto; R. H. Mangia; C. V. Lisboa; D. A. Campbell; J. R. Coura; A. Jansen; O. Fernandes

1998-01-01

375

Potentiality of a New Minimum-Order Back-EMF State-Observer Taking Acceleration into Account for Sensorless Vector Control of Permanent-Magnet Synchronous Motors  

NASA Astrophysics Data System (ADS)

This paper proposes new sensorless vector control methods for permanent-magnet synchronous motors (PMSMs), which are based on a new minimum-order back-EMF state-observer taking acceleration into account, and examines potentiality of the improved back-EMF observer through experiments. Conventional sensorless vector control methods for PMSMs using an estimate of back-EMF are established under the assumption of constant speed or zero acceleration, consequently cannot operate properly at modes requiring rapid speed change especially in low speed region. On the other hand, the proposed back-EMF observer has the following features: 1) it is a new back-EMF state-observer taking acceleration into account and requiring no additional approximation to motor mathematical model; 2) it is a minimum order state-observer; 3) it utilizes motor parameters in the simplest manner; 4) it can be applied to both of salient-pole and non-salient-pole PMSMs; 5) it can be realized in both rotor and stator reference frames. Detailed designs and analyses for the improved state-observer and the sensorless vector control systems in both rotor and stator reference frames are given. In relation to the sensorless vector control systems, this paper newly proposes a double-integral type PLL method and an integral-feedback type acceleration/speed estimation method. Their potentialities are examined through experiments.

Shinnaka, Shinji; Saito, Yoji

376

Impact of Education Campaign on Community-Based Vector Control in Hastening the Process of Elimination of Lymphatic Filariasis in Tamil Nadu, South India  

ERIC Educational Resources Information Center

Globally mosquito-borne lymphatic filariasis (LF) is targeted for elimination by 2020. Towards this goal, the scope of community-based vector control as a supplementary strategy to mass drug administration (MDA) was assessed through an intensive education campaign and evaluated using pre- and post-educational surveys in an intervention and…

Nandha, B.; Krishnamoorthy, K.

2012-01-01

377

Exploring new thermal fog and ultra-low volume technologies to improve indoor control of the dengue vector, Aedes aegypti (Diptera: Culicidae).  

PubMed

Control of the mosquito vector, Aedes aegypti (L.), inside human habitations must be performed quickly and efficiently to reduce the risk of transmission during dengue outbreaks. As part of abroad study to assess the efficacy of dengue vector control tools for the U.S. Military, two pesticide delivery systems (ultra-low volume [ULV] and thermal fog) were evaluated for their ability to provide immediate control of Ae. aegypti mosquitoes with a contact insecticide inside simulated urban structures. An insect growth regulator was also applied to determine how well each sprayer delivered lethal doses of active ingredient to indoor water containers for pupal control. Mortality of caged Ae. aegypti, pesticide droplet size, and droplet deposition were recorded after applications. In addition, larval and pupal mortality was measured from treated water samples for 4 wk after the applications. The ULV and the thermal fogger performed equally well in delivering lethal doses of adulticide throughout the structures. The ULV resulted in greater larval mortality and adult emergence inhibition in the water containers for a longer period than the thermal fogger. Therefore, the ULV technology is expected to be a better tool for sustained vector suppression when combined with an effective insect growth regulator. However, during a dengue outbreak, either delivery system should provide an immediate knockdown of vector populations that may lower the risk of infection and allow other suppression strategies to be implemented. PMID:25118418

Harwood, James F; Farooq, Muhammad; Richardson, Alec G; Doud, Carl W; Putnam, John L; Szumlas, Daniel E; Richardson, Jason H

2014-07-01

378

[Method of biological control of Triatominae, vectors of Chagas disease, using entomopathogenic Hyphomycetes. Preliminary study].  

PubMed

Bioassays determined the pathogenic activity of 14 strains of 5 entomopathogenic hyphomycetous species (Fungi imperfecti), Beauveria bassiana, Beauveria brongniartii, Metarhizium anisopliae, Nomuraea rileyi and Paecilomyces fumosoroseus to Rhodnius prolixus. Treatments consisted of direct spraying with conidial titrated suspensions on first instar larvae. When tested at 3 X 10(5) conidia/cm2, only 2 strains, B. bassiana n. 297 and B. bassiana n. 326 killed 100% of larvae at 10 days post-exposure. In the same time their LD50 and their LD90 did not differ significantly. After 3 weeks, the mortality caused by either dose of spores of B. bassiana n. 297 was very high. In contrast, in the case of B. bassiana n. 326 mortality due to reduced doses remained at low rates. This laboratory study demonstrated that the isolate, B. bassiana n. 297 might have potential as microbial control agent against the assassin bugs. PMID:3111731

Romaña, C A; Fargues, J; Pays, J F

1987-01-01

379

Immunization of mice against African trypanosomiasis using anti- idiotypic antibodies  

PubMed Central

Anti-idiotypic (anti-Id) antibodies were raised against three protective monoclonal antibodies, each with specificity for the variable antigen type (VAT) of a clone of Trypanosoma rhodesiense. The IgG1 fractions of each were pooled and administered to BALB/c mice 3-4 wk before homologous challenge. The course of primary parasitemia was altered in 19 of 30 anti-Id-treated animals. The immunity was manifested as either: (a) complete protection, (b) reduced parasitemia, or (c) selection against parasites bearing the original VAT. The three idiotypes (Id) were found in variable levels in serum during the course of infection in control animals. However, in all anti-Id-treated mice that displayed immunity, one Id in particular (7H11) was detectable much earlier in infection and in higher levels than in control mice or anti-Id-treated, nonimmune mice. Six of nine mice treated with the anti- 7H11 Id alone also displayed immunity, manifested in this case exclusively as selection against parasites bearing the original VAT. The effect was again associated with the more rapid appearance of the Id after infection. Specificity of the anti-Id-induced immunity was supported by the failure of anti-7H11 Id treatment to alter the course of infection with a heterologous clone of T. rhodesiense. To our knowledge, this is the first report of the antigen-independent induction of antimicrobial immunity using anti-Id antibodies. PMID:6977615

1982-01-01

380

Vector Voyage!  

NSDL National Science Digital Library

In this activity, students will use vector analysis to understand the concept of dead reckoning. Students will use vectors to plot their course based on a time and speed. They will then correct the positions with vectors representing winds and currents.

Jeff White

2004-01-01

381

Fascioliasis Control: In Vivo and In Vitro Phytotherapy of Vector Snail to Kill Fasciola Larva  

PubMed Central

Snail is one of the important components of an aquatic ecosystem, it acts as intermediate host of Fasciola species. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. Life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria in the snail body. In vivo and in vitro toxicity of the plant products and their active component such as citral, ferulic acid, umbelliferone, azadirachtin, and allicin against larva of Fasciola in infected snail Lymnaea acuminata were tested. Mortality of larvae were observed at 2?h, 4?h, 6?h, and 8?h, of treatment. In in vivo treatment, azadirachtin caused highest mortality in redia and cercaria larva (8?h, LC50 0.11, and 0.05?mg/L) whereas in in vitro condition allicin was highly toxic against redia and cercaria (8?h, LC50 0.01, and 0.009?mg/L). Toxicity of citral was lowest against redia and cercaria larva. PMID:22132306

Sunita, Kumari; Singh, D. K.

2011-01-01

382

Actigraphy in Human African Trypanosomiasis as a Tool for Objective Clinical Evaluation and Monitoring: A Pilot Study  

PubMed Central

Background Human African trypanosomiasis (HAT) or sleeping sickness leads to a complex neuropsychiatric syndrome with characteristic sleep alterations. Current division into a first, hemolymphatic stage and second, meningoencephalitic stage is primarily based on the detection of white blood cells and/or trypanosomes in the cerebrospinal fluid. The validity of this criterion is, however, debated, and novel laboratory biomarkers are under study. Objective clinical HAT evaluation and monitoring is therefore needed. Polysomnography has effectively documented sleep-wake disturbances during HAT, but could be difficult to apply as routine technology in field work. The non-invasive, cost-effective technique of actigraphy has been widely validated as a tool for the ambulatory evaluation of sleep disturbances. In this pilot study, actigraphy was applied to the clinical assessment of HAT patients. Methods/Principal Findings Actigraphy was recorded in patients infected by Trypanosoma brucei gambiense, and age- and sex-matched control subjects. Simultaneous nocturnal polysomnography was also performed in the patients. Nine patients, including one child, were analyzed at admission and two of them also during specific treatment. Parameters, analyzed with user-friendly software, included sleep time evaluated from rest-activity signals, rest-activity rhythm waveform and characteristics. The findings showed sleep-wake alterations of various degrees of severity, which in some patients did not parallel white blood cell counts in the cerebrospinal fluid. Actigraphic recording also showed improvement of the analyzed parameters after treatment initiation. Nocturnal polysomnography showed alterations of sleep time closely corresponding to those derived from actigraphy. Conclusions/Significance The data indicate that actigraphy can be an interesting tool for HAT evaluation, providing valuable clinical information through simple technology, well suited also for long-term follow-up. Actigraphy could therefore objectively contribute to the clinical assessment of HAT patients. This method could be incorporated into a clinical scoring system adapted to HAT to be used in the evaluation of novel treatments and laboratory biomarkers. PMID:22348168

Njamnshi, Alfred K.; Seke Etet, Paul F.; Perrig, Stephen; Acho, Alphonse; Funsah, Julius Y.; Mumba, Dieudonné; Muyembe, Jean-Jacques; Kristensson, Krister; Bentivoglio, Marina

2012-01-01

383

A Capsid-Modified Helper-Dependent Adenovirus Vector Containing the ?-Globin Locus Control Region Displays a Nonrandom Integration Pattern and Allows Stable, Erythroid-Specific Gene Expression  

PubMed Central

Gene therapy for hemoglobinopathies requires efficient gene transfer into hematopoietic stem cells and high-level erythroid-specific gene expression. Toward this goal, we constructed a helper-dependent adenovirus vector carrying the ?-globin locus control region (LCR) to drive green fluorescent protein (GFP) expression, whereby the LCR-GFP cassette is flanked by adeno-associated virus (AAV) inverted terminal repeats (Ad.LCR-?-GFP). This vector possesses the adenovirus type 35 fiber knob that allows efficient infection of hematopoietic cells. Transduction and vector integration studies were performed in MO7e cells, a growth factor-dependent CD34+ erythroleukemic cell line, and in cord blood-derived human CD34+ cells. Stable transduction of MO7e cells with Ad.LCR-?-GFP was more efficient and less subject to position effects and silencing than transduction with a vector that did not contain the ?-globin LCR. Analysis of integration sites indicated that Ad.LCR-?-GFP integration in MO7e cells was not random but tethered to chromosome 11, specifically to the globin LCR. More than 10% of analyzed integration sites were within the chromosomal ?-globin LCR. None of the Ad.LCR-?-GFP integrations occurred in exons. The integration pattern of a helper-dependent vector that contained X-chromosomal stuffer DNA was different from that of the ?-globin LCR-containing vector. Infection of primary CD34+ cells with Ad.LCR-?-GFP did not affect the clonogenic capacity of CD34+ cells. Transduction of CD34+ cells with Ad.LCR-?-GFP resulted in vector integration and erythroid lineage-specific GFP expression. PMID:16103151

Wang, Hongjie; Shayakhmetov, Dmitry M.; Leege, Tobias; Harkey, Michael; Li, Qiliang; Papayannopoulou, Thalia; Stamatoyannopolous, George; Lieber, André

2005-01-01

384

Large fluctuations in the effective population size of the malaria mosquito Anopheles gambiae s.s. during vector control cycle  

PubMed Central

On Bioko Island, Equatorial Guinea, indoor residual spraying (IRS) has been part of the Bioko Island Malaria Control Project since early 2004. Despite success in reducing childhood infections, areas of high transmission remain on the island. We therefore examined fluctuations in the effective population size (Ne) of the malaria vector Anopheles gambiae in an area of persistent high transmission over two spray rounds. We analyzed data for 13 microsatellite loci from 791 An. gambiae specimens collected at six time points in 2009 and 2010 and reconstructed the demographic history of the population during this period using approximate Bayesian computation (ABC). Our analysis shows that IRS rounds have a large impact on Ne, reducing it by 65%–92% from prespray round Ne. More importantly, our analysis shows that after 3–5 months, the An. gambiae population rebounded by 2818% compared shortly following the spray round. Our study underscores the importance of adequate spray round frequency to provide continuous suppression of mosquito populations and that increased spray round frequency should substantially improve the efficacy of IRS campaigns. It also demonstrates the ability of ABC to reconstruct a detailed demographic history across only a few tens of generations in a large population. PMID:24478799

Hodges, Theresa K; Athrey, Giridhar; Deitz, Kevin C; Overgaard, Hans J; Matias, Abrahan; Caccone, Adalgisa; Slotman, Michel A

2013-01-01

385

Pharmacology of DB844, an Orally Active aza Analogue of Pafuramidine, in a Monkey Model of Second Stage Human African Trypanosomiasis  

E-print Network

Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites...

Thutia, John K.; Wang, Michael Z.; Kagira, John M.; Denton, Cathrine L.; Paine, Mary F.; Mdachi, Raymond E.; Murilla, Grace A.; Ching, Shelley; Boykin, David W.; Tidwell, Richard R.; Hall, James E.; Brun, Reto

2012-07-24

386

Effectiveness and feasibility of long-lasting insecticide-treated curtains and water container covers for dengue vector control in Colombia: a cluster randomised trial  

PubMed Central

Background Long-lasting insecticide-treated net (LLIN) window and door curtains alone or in combination with LLIN water container covers were analysed regarding effectiveness in reducing dengue vector density, and feasibility of the intervention. Methods A cluster randomised trial was conducted in an urban area of Colombia comparing 10 randomly selected control and 10 intervention clusters. In control clusters, routine vector control activities were performed. The intervention delivered first, LLIN curtains (from July to August 2013) and secondly, water container covers (from October to March 2014). Cross-sectional entomological surveys were carried out at baseline (February 2013 to June 2013), 9 weeks after the first intervention (August to October 2013), and 4–6 weeks after the second intervention (March to April 2014). Results Curtains were installed in 922 households and water container covers in 303 households. The Breteau index (BI) fell from 14 to 6 in the intervention group and from 8 to 5 in the control group. The additional intervention with LLIN covers for water containers showed a significant reduction in pupae per person index (PPI) (p=0.01). In the intervention group, the PPI index showed a clear decline of 71% compared with 25% in the control group. Costs were high but options for cost savings were identified. Conclusions Short term impact evaluation indicates that the intervention package can reduce dengue vector density but sustained effect will depend on multiple factors. PMID:25604762

Quintero, Juliana; García-Betancourt, Tatiana; Cortés, Sebastian; García, Diana; Alcalá, Lucas; González-Uribe, Catalina; Brochero, Helena; Carrasquilla, Gabriel

2015-01-01

387

Metabolic signatures of triatomine vectors of Trypanosoma cruzi unveiled by metabolomics.  

PubMed

Chagas disease is a trypanosomiasis whose causative agent is the protozoan parasite Trypanosoma cruzi, which is transmitted to humans by hematophagous insects known as triatomines and affects a large proportion of South America. The digestive tract of the insect vectors in which T. cruzi develops constitutes a dynamic environment that affects the development of the parasite. Thus, we set out to investigate the chemical composition of the triatomine intestinal tract through a metabolomics approach. We performed Direct Infusion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry on fecal samples of three triatomine species (Rhodnius prolixus, Triatoma infestans, Panstrongylus megistus) fed with rabbit blood. We then identified groups of metabolites whose frequencies were either uniform in all species or enriched in each of them. By querying the Human Metabolome Database, we obtained putative identities of the metabolites of interest. We found that a core group of metabolites with uniform frequencies in all species represented approximately 80% of the molecules detected, whereas the other 20% varied among triatomine species. The uniform core was composed of metabolites of various categories, including fatty acids, steroids, glycerolipids, nucleotides, sugars, and others. Nevertheless, the metabolic fingerprint of triatomine feces differs depending on the species considered. The variable core was mainly composed of prenol lipids, amino acids, glycerolipids, steroids, phenols, fatty acids and derivatives, benzoic acid and derivatives, flavonoids, glycerophospholipids, benzopyrans, and quinolines. Triatomine feces constitute a rich and varied chemical medium whose constituents are likely to affect T. cruzi development and infectivity. The complexity of the fecal metabolome of triatomines suggests that it may affect triatomine vector competence for specific T. cruzi strains. Knowledge of the chemical environment of T. cruzi in its invertebrate host is likely to generate new ways to understand the factors influencing parasite proliferation as well as methods to control Chagas disease. PMID:24204787

Antunes, Luis Caetano M; Han, Jun; Pan, Jingxi; Moreira, Carlos J C; Azambuja, Patrícia; Borchers, Christoph H; Carels, Nicolas

2013-01-01

388

Alternative Treatments for Indoor Residual Spraying for Malaria Control in a Village with Pyrethroid- and DDT-Resistant Vectors in The Gambia  

PubMed Central

Background Malaria vector control is threatened by resistance to pyrethroids, the only class of insecticides used for treating bed nets. The second major vector control method is indoor residual spraying with pyrethroids or the organochloride DDT. However, resistance to pyrethroids frequently confers resistance to DDT. Therefore, alternative insecticides are urgently needed. Methodology/Principal Findings Insecticide resistance and the efficacy of indoor residual spraying with different insecticides was determined in a Gambian village. Resistance of local vectors to pyrethroids and DDT was high (31% and 46% mortality, respectively) while resistance to bendiocarb and pirimiphos methyl was low (88% and 100% mortality, respectively). The vectors were predominantly Anopheles gambiae s.s. with 94% of them having the putative resistant genotype kdr 1014F. Four groups of eight residential compounds were each sprayed with either (1) bendiocarb, a carbamate, (2) DDT, an organochlorine, (3) microencapsulated pirimiphos methyl, an organophosphate, or (4) left unsprayed. All insecticides tested showed high residual activity up to five months after application. Mosquito house entry, estimated by light traps, was similar in all houses with metal roofs, but was significantly less in IRS houses with thatched roofs (p=0.02). Residents participating in focus group discussions indicated that IRS was considered a necessary nuisance and also may decrease the use of long-lasting insecticidal nets. Conclusion/Significance Bendiocarb and microencapsulated pirimiphos methyl are viable alternatives for indoor residual spraying where resistance to pyrethroids and DDT is high and may assist in the management of pyrethroid resistance. PMID:24058551

Tangena, Julie-Anne A.; Adiamoh, Majidah; D’Alessandro, Umberto; Jarju, Lamin; Jawara, Musa; Jeffries, David; Malik, Naiela; Nwakanma, Davis; Kaur, Harparkash; Takken, Willem; Lindsay, Steve W.; Pinder, Margaret

2013-01-01

389

Parasitic Central Nervous System Infections in Immunocompromised Hosts: Malaria, Microsporidiosis, Leishmaniasis, and African Trypanosomiasis  

PubMed Central

Immunosuppression associated with HIV infection or following transplantation increases susceptibility to central nervous system (CNS) infections. Because of increasing international travel, parasites that were previously limited to tropical regions pose an increasing infectious threat to populations at risk for acquiring opportunistic infection, especially people with HIV infection or individuals who have received a solid organ or bone marrow transplant. Although long-term immunosuppression caused by medications such as prednisone likely also increases the risk for acquiring infection and for developing CNS manifestations, little published information is available to support this hypothesis. In an earlier article published in Clinical Infectious Diseases, we described the neurologic manifestations of some of the more common parasitic CNS infections. This review will discuss the presentation, diagnosis, and treatment of the following additional parasitic CNS infections: malaria, microsporidiosis, leishmaniasis, and African trypanosomiasis. PMID:16323101

Walker, Melanie; Kublin, James G.; Zunt, Joseph R.

2009-01-01

390

New Insights in Staging and Chemotherapy of African Trypanosomiasis and Possible Contribution of Medicinal Plants  

PubMed Central

Human African trypanosomiasis (HAT) is a fatal if untreated fly-borne neuroinflammatory disease caused by protozoa of the species Trypanosoma brucei (T.b.). The increasing trend of HAT cases has been reversed, but according to WHO experts, new epidemics of this disease could appear. In addition, HAT is still a considerable burden for life quality and economy in 36 sub-Saharan Africa countries with 15–20 million persons at risk. Following joined initiatives of WHO and private partners, the fight against HAT was re-engaged, resulting in considerable breakthrough. We present here what is known at this day about HAT etiology and pathogenesis and the new insights in the development of accurate tools and tests for disease staging and severity monitoring in the field. Also, we elaborate herein the promising progresses made in the development of less toxic and more efficient trypanocidal drugs including the potential of medicinal plants and related alternative drug therapies. PMID:22593674

Seke Etet, Paul F.; Fawzi Mahomoodally, M.

2012-01-01

391

Prevalence of human African trypanosomiasis in the Democratic Republic of the Congo.  

PubMed

Human African Trypanosomiasis (HAT) is a major public health problem in the Democratic Republic of the Congo (DRC). Active and passive surveillance for HAT is conducted but may underestimate the true prevalence of the disease. We used ELISA to screen 7,769 leftover dried blood spots from a nationally representative population-based survey, the 2007 Demographic and Health Survey. 26 samples were positive by ELISA. Three of these were also positive by trypanolysis and/or PCR. From these data, we estimate that there were 18,592 people with HAT (95% confidence interval, 4,883-32,302) in the DRC in 2007, slightly more than twice as many as were reported. PMID:21829736

Mumba, Dieudonne; Bohorquez, Elaine; Messina, Jane; Kande, Victor; Taylor, Steven M; Tshefu, Antoinette K; Muwonga, Jeremie; Kashamuka, Melchior M; Emch, Michael; Tidwell, Richard; Büscher, Philippe; Meshnick, Steven R

2011-08-01

392

Prevalence of Human African Trypanosomiasis in the Democratic Republic of the Congo  

PubMed Central

Human African Trypanosomiasis (HAT) is a major public health problem in the Democratic Republic of the Congo (DRC). Active and passive surveillance for HAT is conducted but may underestimate the true prevalence of the disease. We used ELISA to screen 7,769 leftover dried blood spots from a nationally representative population-based survey, the 2007 Demographic and Health Survey. 26 samples were positive by ELISA. Three of these were also positive by trypanolysis and/or PCR. From these data, we estimate that there were 18,592 people with HAT (95% confidence interval, 4,883–32,302) in the DRC in 2007, slightly more than twice as many as were reported. PMID:21829736

Mumba, Dieudonne; Bohorquez, Elaine; Messina, Jane; Kande, Victor; Taylor, Steven M.; Tshefu, Antoinette K.; Muwonga, Jeremie; Kashamuka, Melchior M.; Emch, Michael; Tidwell, Richard; Büscher, Philippe; Meshnick, Steven R.

2011-01-01

393

[Arsenical resistance and difluoromethylornithine in the treatment of human African trypanosomiasis].  

PubMed

Human African trypanosomiasis (HAT) in Zaïre is a medical problem of first importance, particularly in endemic areas where sleeping sickness threatens about 10 millions of human beings almost the third of the whole population. Used since about forty years as the main trypanocidal drug, melarsoprol is accompanied with a more and more important rate of failures (10%) during the last ten years. 86 patients from whom 51 were refractory with melarsoprol have been treated with difluoromethylornithine (DFMO) since May 1984. Results which have been obtained seem to be encouraging because desperate cases are considered cured after 2 years of set-back. Side effects (disorders of intestinal function, anaemia, drug administration over a long period of time) may be considered as minor. PMID:3143492

Kazyumba, G L; Ruppol, J F; Tshefu, A K; Nkanga, N

1988-01-01

394

Importance of the horse and financial impact of equine trypanosomiasis on cattle raising in Venezuela.  

PubMed

In Venezuela, horses are indispensable for extensive cattle raising, and extensive cattle raising prevails in all regions. This determines the numerical relationship between horses and cattle (r?=?0.93) to be relatively constant nationwide. At regional level, the average extension of cattle ranches varies greatly. However, in relation to the area covered by pastures, the numbers of horses (r?=?0.95) and cattle (r?=?0.93) are relatively uniform nationwide. Water buffalo occupy small fractions of the territory; therefore, their numbers are related to the area of pastures less strongly (r?=?0.56). There is no information on the numerical relationship between the numbers of horses and water buffalo. In the Llanos region of the country, equine trypanosomiasis is responsible for a high mortality in horses, causing considerable financial losses to cattle ranches. So far, such losses have not been assessed. For this region, in 2008, it can be calculated that: (1) with no treatment, losses owing to horse mortality caused by this hemoparasitosis would have amounted to US$7,486,000; (2) the diagnosis and treatment of affected horses would have required an investment of US$805,000; and (3) in terms of horses saved, this investment would have resulted in benefit of US$6,232,000. Therefore, for every monetary unit invested, there would be a benefit 7.75 times greater, this ratio being applicable to any year and all regions of the country. It follows that the profitability of investing in the diagnosis and treatment of equine trypanosomiasis is guaranteed. PMID:23666515

Moreno, S Andrea; Concepción, Juan Luis; Nava, Mayerly; Molinari, Jesús

2013-11-01

395

Domestic pigs as potential reservoirs of human and animal trypanosomiasis in Northern Tanzania  

PubMed Central

Background Pig keeping is becoming increasingly common across sub-Saharan Africa. Domestic pigs from the Arusha region of northern Tanzania were screened for trypanosomes using PCR-based methods to examine the role of pigs as a reservoir of human and animal trypanosomiasis. Methods A total of 168 blood samples were obtained from domestic pigs opportunistically sampled across four districts in Tanzania (Babati, Mbulu, Arumeru and Dodoma) during December 2004. A suite of PCR-based methods was used to identify the species and sub-species of trypanosomes including: Internally Transcribed Sequence to identify multiple species; species specific PCR to identify T. brucei s. l. and T. godfreyi and a multiplex PCR reaction to distinguish T. b. rhodesiense from T. brucei s. l. Results Of the 168 domestic pigs screened for animal and human infective trypanosome DNA, 28 (16.7%) were infected with one or more species of trypanosome; these included: six pigs infected with Trypanosoma vivax (3.6%); three with Trypanosoma simiae (1.8%); two with Trypanosoma congolense (Forest) (1%) and four with Trypanosoma godfreyi (2.4%). Nineteen pigs were infected with Trypanosoma brucei s. l. (10.1%) of which eight were identified as carrying the human infective sub-species Trypanosoma brucei rhodesiense (4.8%). Conclusion These results show that in Tanzania domestic pigs may act as a significant reservoir for animal trypanosomiasis including the cattle pathogens T. vivax and T. congolense, the pig pathogen T. simiae, and provide a significant reservoir for T. b. rhodesiense, the causative agent of acute Rhodesian sleeping sickness. PMID:24499540

2013-01-01

396

Identification of sVSG117 as an Immunodiagnostic Antigen and Evaluation of a Dual-Antigen Lateral Flow Test for the Diagnosis of Human African Trypanosomiasis  

PubMed Central

Background The diagnosis of human African trypanosomiasis (HAT) caused by Trypanosoma brucei gambiense relies mainly on the Card Agglutination Test for Trypanosomiasis (CATT). There is no immunodiagnostic for HAT caused by T. b. rhodesiense. Our principle aim was to develop a prototype lateral flow test that might be an improvement on CATT. Methodology/Principle Findings Pools of infection and control sera were screened against four different soluble form variant surface glycoproteins (sVSGs) by ELISA and one, sVSG117, showed particularly strong immunoreactivity to pooled infection sera. Using individual sera, sVSG117 was shown to be able to discriminate between T. b. gambiense infection and control sera by both ELISA and lateral flow test. The sVSG117 antigen was subsequently used with a previously described recombinant diagnostic antigen, rISG65, to create a dual-antigen lateral flow test prototype. The latter was used blind in a virtual field trial of 431 randomized infection and control sera from the WHO HAT Specimen Biobank. Conclusion/Significance In the virtual field trial, using two positive antigen bands as the criterion for infection, the sVSG117 and rISG65 dual-antigen lateral flow test prototype showed a sensitivity of 97.3% (95% CI: 93.3 to 99.2) and a specificity of 83.3% (95% CI: 76.4 to 88.9) for the detection of T. b. gambiense infections. The device was not as good for detecting T. b. rhodesiense infections using two positive antigen bands as the criterion for infection, with a sensitivity of 58.9% (95% CI: 44.9 to 71.9) and specificity of 97.3% (95% CI: 90.7 to 99.7). However, using one or both positive antigen band(s) as the criterion for T. b. rhodesiense infection improved the sensitivity to 83.9% (95% CI: 71.7 to 92.4) with a specificity of 85.3% (95% CI: 75.3 to 92.4). These results encourage further development of the dual-antigen device for clinical use. PMID:25033401

Sullivan, Lauren; Fleming, Jennifer; Sastry, Lalitha; Mehlert, Angela; Wall, Steven J.; Ferguson, Michael A. J.

2014-01-01

397

Potential of contact insecticides to control Xyleborus glabratus (Coleoptera: Curculionidae), a vector of laurel wilt disease in avocados.  

PubMed

Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae) is an invasive ambrosia beetle that vectors laurel wilt, a new disease that threatens avocado and other species in the Lauraceae Family. The lethal concentrations (LC50 & 90) of nine commercial insecticides to X. glabratus were determined by using a bolt-dip bioassay. Different formulations of bifenthrin, permethrin, fenpropathrin, z-cypermethrin + bifenthrin, 1-cyhalothrin + thiamethoxam, malathion, chlorpyrifos, carbaryl, and methomyl were tested. Four concentrations of each insecticide were tested (0.5, 0.1, 0.03, and 0.01 of the label rate) and with water as a control. Beetles were exposed to treated bolts and mortality registered 48 h later. After 2 wk, bolts were destructively sampled to determine the number of beetles that constructed galleries and were alive inside the wood. Probit analysis was used to determine the LC50 & 90. Six pesticides were applied directly to the trunk and limbs of avocado trees in a commercial grove. Limbs of treated trees were cut weekly after the application and exposed to X. glabratus to determine the number of beetles boring into the logs. The toxicity of pesticides to X. glabratus was greatly reduced 2 wk after application. Among the tested pesticides, malathion and z-cypermethrin + bifenthrin provided the best suppression of X. glabratus. Among the insecticides registered for use in avocado, fenpropathrin and malathion were the most effective in protecting trees from attack by X. glabratus. Other pesticides that are currently not registered for use in avocados could be useful for managing this ambrosia beetle. PMID:24498726

Carrillo, Daniel; Crane, Jonathan H; Peña, Jorge E

2013-12-01

398

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

PubMed Central

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

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

2015-01-01

399

Endemic type of animal trypanosomiasis is not associated with lower genotype variability of Trypanosoma congolense isolates circulating in livestock  

PubMed Central

In order to verify whether the low impact on livestock production in endemic areas is related to a low number of trypanosome strains circulating in livestock, 37 Trypanosoma congolense isolates collected from cattle in 11 sites in an endemic trypanosomiasis area in Eastern Zambia were characterised for genotype variability using a modified amplified fragment length polymorphism technique (AFLP). Isolates were further cloned to evaluate the occurrence of mixed infections in individuals. The results obtained revealed a high genotype diversity (94.6%) among these isolates. Apart from one site, all isolates gave different AFLP profiles in each of the sites. When clones were compared, three (8%) of the 37 isolates had mixed infections. These results indicate the circulation of a high number of strains in this trypanosomiasis endemic area despite the low impact the disease has on livestock production. PMID:19356778

Masumu, J.; Geysen, D.; Bossche, P. Van den

2009-01-01

400

Eco-ethological heterogeneity of the members of the Anopheles minimus complex (Diptera: Culicidae) in Southeast Asia and its consequences for vector control.  

PubMed

The presence of cryptic species within Anopheles minimus s.l. Theobald, one of the most widespread malaria vectors in Southeast Asia, was suggested on the basis of behavioral heterogeneities observed within this taxon. Subsequently, two species, A and C, were recognized. However, the existence of these cryptic species did not explain all observed behavioral heterogeneities within this complex. Besides, data on the behavior of vectors are essential to understand the dynamics of disease transmission and thus evaluate the appropriateness of vector control measures. Different collection methods were used to collect Anopheles species from several localities in Southeast Asia to assess the inter- and intraspecific behavioral divergences of An. minimus A and C. Collection results were subjected to a correspondence analysis. The members of the An. minimus complex were identified by use of the octanol dehydrogenase allozyme profiles or the polymerase chain reaction-restriction fragment length polymorphism assay. Large intraspecific behavioral differences were observed among populations of An. minimus A. These populations belong to the same species on the basis of the applied genetic markers. In northern Vietnam, species A tended to be more zoophilic, whereas in the study sites of south central Vietnam, Cambodia, and Laos it showed marked antropophilic behavior when cattle were scarce. In the most northern study site, An. minimus A showed noteworthy endophilic behavior. An. minimus C was primarily zoophilic and based on this behavior, its role in malaria transmission is questionable. However, it was only found in one locality, so that intraspecific behavioral variation could not be assessed. An. minimus A is able to change its host preference in function of local situations in host availability. Hence, its role in malaria transmission can differ from region to region. Similarly, the impact of vector control on this species may differ between localities. In conclusion, intraspecific behavioral differences in Anopheles species can occur and these behavioral heterogeneities, albeit important for disease transmission and control, are not a priori indicative for the presence of cryptic species. PMID:15185937

Van Bortel, Wim; Trung, Ho Dinh; Sochantha, Tho; Keokenchan, Kalouna; Roelants, Patricia; Backeljau, Thierry; Coosemans, Marc

2004-05-01

401

The importance of veterinary policy in preventing the emergence and re-emergence of zoonotic disease: examining the case of human african trypanosomiasis in Uganda.  

PubMed

Rapid changes in human behavior, resource utilization, and other extrinsic environmental factors continue to threaten the current distribution of several endemic and historically neglected zoonoses in many developing regions worldwide. There are numerous examples of zoonotic diseases which have circulated within relatively localized geographical areas for some time, before emerging into new regions as a result of changing human, environmental, or behavioral dynamics. While the world's focus is currently on the Ebola virus gaining momentum in western Africa, another pertinent example of this phenomenon is zoonotic human African trypanosomiasis (HAT), endemic to south and eastern Africa, and spread via infected cattle. In recent years, the ongoing northwards spread of this disease in the country has posed a serious public health threat to the human population of Uganda, increasing the pressure on both individual families and government services to control the disease. Moreover, the emergence of HAT into new areas of Uganda in recent years exemplifies the important role of veterinary policy in mitigating the severe human health and economic impacts of zoonotic disease. The systemic challenges surrounding the development and enforcement of veterinary policy described here are similar across sub-Saharan Africa, highlighting the necessity to consider and support zoonotic disease control in broader human and animal health systems strengthening and associated development programs on the continent. PMID:25405148

Okello, Anna L; Welburn, Susan C

2014-01-01

402

The Importance of Veterinary Policy in Preventing the Emergence and Re-Emergence of Zoonotic Disease: Examining the Case of Human African Trypanosomiasis in Uganda  

PubMed Central

Rapid changes in human behavior, resource utilization, and other extrinsic environmental factors continue to threaten the current distribution of several endemic and historically neglected zoonoses in many developing regions worldwide. There are numerous examples of zoonotic diseases which have circulated within relatively localized geographical areas for some time, before emerging into new regions as a result of changing human, environmental, or behavioral dynamics. While the world’s focus is currently on the Ebola virus gaining momentum in western Africa, another pertinent example of this phenomenon is zoonotic human African trypanosomiasis (HAT), endemic to south and eastern Africa, and spread via infected cattle. In recent years, the ongoing northwards spread of this disease in the country has posed a serious public health threat to the human population of Uganda, increasing the pressure on both individual families and government services to control the disease. Moreover, the emergence of HAT into new areas of Uganda in recent years exemplifies the important role of veterinary policy in mitigating the severe human health and economic impacts of zoonotic disease. The systemic challenges surrounding the development and enforcement of veterinary policy described here are similar across sub-Saharan Africa, highlighting the necessity to consider and support zoonotic disease control in broader human and animal health systems strengthening and associated development programs on the continent. PMID:25405148

Okello, Anna L.; Welburn, Susan C.

2014-01-01

403

Vector processing  

SciTech Connect

An apparatus is described for adapting a scalar data processor having a cache memory connected between main memory and a central processing unit, for efficient vector processing including: means for defining separate scalar and vector data areas in the cache memory, vector mode selection means for selectively enabling access to either the vector or scalar data areas of the cache memory, cache memory addressing means including separate vector and scalar addressing means responsive to the vector mode selection means and the central processing unit for accessing either the vector or scalar data areas of the cache memory, wherein the central processing unit includes: a pair of operand registers, and a result register, coupling means for providing a data path from the operand registers to an ALU and a further data path from an ALU to the result register, second coupling means for providing a data path from the cache memory to one of the operand registers and to the result register; an output buffer; third coupling means providing a data path from either of the operand registers to the second coupling means and to the output buffer; fourth coupling means providing a data path from the second coupling means or the output buffer to the cache memory; and fifth coupling means providing a data path from the result register to either of the operand registers.

Drimak, E.G.

1986-06-10

404

Control of human filarial vector, Culex quinquefasciatus Say 1823 (Diptera: Culicidae) through bioactive fraction of Cayratia trifolia leaf  

PubMed Central

Objective To investigate the mosquito larvicidal activity of Cayratia trifolia (L.) Domin (Vitaceae: Vitales) (C. trifolia) which is distributed in many parts of India with medicinal properties as vector control is facing threat due to the emergence of resistance to synthetic insecticides. Methods Young and mature leaves of C. trifolia were investigated for larvicidal activity against 3rd instars larvae of Culex quinquefasciatus in different seasons throughout the year. The active fractions were extracted using six different solvents in a non-polar to polar fashion viz petroleum-ether, benzene, chloroform: methanol (1:1 v/v), acetone, absolute alcohol and distilled water. Dose dependent mortality was recorded against each solvent extract. Determination of LD50 and LD90 were executed through log-probit analysis using the most bioactive fraction. The fluctuations in mortality were statistically co-related through ANOVA analyses concerning different seasons and types of leaves as random variables. Justification of larvicidal activity was established through student's t-test. Costing effects were evaluated on the non-target water fauna under laboratory conditions. Thin layer chromatographic techniques were performed for phytochemical analysis and categorization of chemical personality of the active fractions using the most effective solvent extract following standard methods. Results Significant variations in mortality rate were noted with respect to the type of leaves (mature and senescence), concentration of leaf extract and between seasons. The water extract among all the solvent extracts was found to induce cent percent mortality at 50 mg/L in test mosquito species within 24 h with a LD50 and LD90 value of 10.70 mg/L and 27.64 mg/L respectively. No significant mortality was recorded in non-target water population. Chromatographic analyses of the water extract revealed the presence of steroids, triterpene glycosides, essential oil, phenolics and diterpenes as secondary phytochemicals. Conclusions Water extract of C. trifolia leaf promised as a cost effective and potent larvicidal agent against Culex quinquefasciatus. PMID:24093790

Chakraborty, Sumanta; Singha, Someshwar; Bhattacharya, Kuntal; Chandra, Goutam

2013-01-01

405

Vector Fields  

NSDL National Science Digital Library

Vector fields are vectors which change from point to point. A standard example is the velocity of moving air, in other words, wind. For instance, the current wind pattern in the San Francisco area can be found at . This site has a 2-dimensional representation; careful reading of the webpage will tell you at what elevation the wind is shown. How would you represent a vector field in 3 dimensions? What features are important? Some simple examples are shown. Each can be rotated by clicking and dragging with the mouse. Explore!

Ay, Tevian

2006-01-01

406

Cloning vector  

DOEpatents

A vector comprising a filamentous phage sequence containing a first copy of filamentous phage gene X and other sequences necessary for the phage to propagate is disclosed. The vector also contains a second copy of filamentous phage gene X downstream from a promoter capable of promoting transcription in a bacterial host. In a preferred form of the present invention, the filamentous phage is M13 and the vector additionally includes a restriction endonuclease site located in such a manner as to substantially inactivate the second gene X when a DNA sequence is inserted into the restriction site. 2 figures.

Guilfoyle, R.A.; Smith, L.M.

1994-12-27

407

Gene expression in Asian citrus psyllid adults feeding from Florida citrus: Application to biology and vector control  

Technology Transfer Automated Retrieval System (TEKTRAN)

We used a genomics approach to identify some of the genetic basis of D. citri biology, identifying in particular genes associated with feeding, reproduction, pathology, and insecticide resistance. The Asian citrus psyllid (AsCP), Diaphorina citri (Hemiptera: Psyllidae), is a highly competent vector ...

408

Effects of plant water stress on vector feeding behaviors that control acquisition and inoculation of Xylella fastidiosa  

Technology Transfer Automated Retrieval System (TEKTRAN)

Xylella fastidiosa (Xf) is an economically important pathogen of grapevine (Pierce’s disease), stone fruits, nursery trees, and ornamental plants (various scorch diseases) in California. The bacterium is transmitted by sharpshooter leafhopper vectors, such as the glassy-winged sharpshooter (GWSS),...

409

Entomopathogenic fungi as a biological control for the vector of the laurel wilt disease: the redbay ambrosia beetle  

Technology Transfer Automated Retrieval System (TEKTRAN)

The redbay ambrosia beetle (RAB), Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae) vectors the fungal pathogen, Raffaelea lauricola, which causes laurel wilt (LW), a lethal disease of trees in the family Lauraceae, including the most commercially important crop in this family, avocado, Pe...

410

The elimination of the onchocerciasis vector from the island of Bioko as a result of larviciding by the WHO African Programme for Onchocerciasis Control.  

PubMed

The island of Bioko is part of the Republic of Equatorial Guinea and is the only island in the World to have endemic onchocerciasis. The disease is hyperendemic and shows a forest-type epidemiology with low levels of blindness and high levels of skin disease, and the whole population of 68,000 is estimated to be at risk. Control of onchocerciasis began in 1990 using ivermectin and this yielded significant clinical benefits but transmission was not interrupted. Feasibility and preparatory studies carried out between 1995 and 2002 confirmed the probable isolation of the vector on the island, the high vectorial efficiency of the Bioko form of Simulium yahense, the seasonality of river flow, blackfly breeding and biting densities, and the distribution of the vector breeding sites. It was proposed that larviciding should be carried out from January to April, when most of the island's rivers were dry or too low to support Simulium damnosum s.l., and that most rivers would not need to be treated above 500 m altitude because they were too small to support the breeding of S. damnosum s.l. Larviciding (with temephos) would need to be carried out by helicopter (because of problems of access by land), supplemented by ground-based delivery. Insecticide susceptibility trials showed that the Bioko form was highly susceptible to temephos, and insecticide carry was tested in the rivers by assessing the length of river in which S. damnosum s.l. larvae were killed below a temephos dosing point. Regular fly catching points were established in 1999 to provide pre-control biting densities, and to act as monitoring points for control efforts. An environmental impact assessment concluded that the proposed control programme could be expected to do little damage, and a large-scale larviciding trial using ground-based applications of temephos (Abate 20EC) throughout the northern (accessible) part of the island was carried out for five weeks from 12 February 2001. Following this, a first attempt to eliminate the vectors was conducted using helicopter and ground-based applications of temephos from February to May 2003, but this was not successful because some vector populations persisted and subsequently spread throughout the island. A second attempt from January to May 2005 aimed to treat all flowing watercourses and greatly increased the number of treatment points. This led to the successful elimination of the vector. The last biting S. damnosum s.l. was caught in March 2005 and none have been found since then for more than 3 years. PMID:19619686

Traoré, S; Wilson, M D; Sima, A; Barro, T; Diallo, A; Aké, A; Coulibaly, S; Cheke, R A; Meyer, R R F; Mas, J; McCall, P J; Post, R J; Zouré, H; Noma, M; Yaméogo, L; Sékétéli, A V; Amazigo, U V

2009-09-01

411

Characterisation of the Wildlife Reservoir Community for Human and Animal Trypanosomiasis in the Luangwa Valley, Zambia  

PubMed Central

Background Animal and human trypanosomiasis are constraints to both animal and human health in Sub-Saharan Africa, but there is little recent evidence as to how these parasites circulate in wild hosts in natural ecosystems. The Luangwa Valley in Zambia supports high densities of tsetse flies (Glossina species) and is recognised as an historical sleeping sickness focus. The objective of this study was to characterise the nature of the reservoir community for trypanosomiasis in the absence of influence from domesticated hosts. Methodology/Principal Findings A cross-sectional survey of trypanosome prevalence in wildlife hosts was conducted in the Luangwa Valley from 2005 to 2007. Samples were collected from 418 animals and were examined for the presence of Trypanosoma brucei s.l., T. b. rhodesiense, Trypanosoma congolense and Trypanosoma vivax using molecular diagnostic techniques. The overall prevalence of infection in all species was 13.9% (95% confidence interval [CI]: 10.71–17.57%). Infection was significantly more likely to be detected in waterbuck (Kobus ellipsiprymnus) (Odds ratio [OR]?=?10.5, 95% CI: 2.36–46.71), lion (Panthera leo) (OR?=?5.3, 95% CI: 1.40–19.69), greater kudu (Tragelaphus strepsiceros) (OR?=?4.7, 95% CI: 1.41–15.41) and bushbuck (Tragelaphus scriptus) (OR?=?4.5, 95% CI: 1.51–13.56). Bushbucks are important hosts for T. brucei s.l. while the Bovidae appear the most important for T. congolense. The epidemiology of T. vivax was less clear, but parasites were detected most frequently in waterbuck. Human infective T. b. rhodesiense were identified for the first time in African buffalo (Syncerus caffer) and T. brucei s.l. in leopard (Panthera pardus). Variation in infection rates was demonstrated at species level rather than at family or sub-family level. A number of significant risk factors interact to influence infection rates in wildlife including taxonomy, habitat and blood meal preference. Conclusion and Significance Trypanosoma parasites circulate within a wide and diverse host community in this bio-diverse ecosystem. Consistent land use patterns over the last century have resulted in epidemiological stability, but this may be threatened by the recent influx of people and domesticated livestock into the mid-Luangwa Valley. PMID:21713019

Anderson, Neil E.; Mubanga, Joseph; Fevre, Eric M.; Picozzi, Kim; Eisler, Mark C.; Thomas, Robert; Welburn, Susan C.

2011-01-01

412

Vector ecology of equine piroplasmosis.  

PubMed

Equine piroplasmosis is a disease of Equidae, including horses, donkeys, mules, and zebras, caused by either of two protozoan parasites, Theileria equi or Babesia caballi. These parasites are biologically transmitted between hosts via tick vectors, and although they have inherent differences they are categorized together because they cause similar pathology and have similar morphologies, life cycles, and vector relationships. To complete their life cycle, these parasites must undergo a complex series of developmental events, including sexual-stage development in their tick vectors. Consequently, ticks are the definitive hosts as well as vectors for these parasites, and the vector relationship is restricted to a few competent tick species. Because the vector relationship is critical to the epidemiology of these parasites, we highlight current knowledge of the vector ecology of these tick-borne equine pathogens, emphasizing tick transmissibility and potential control strategies to prevent their spread. PMID:25564746

Scoles, Glen A; Ueti, Massaro W

2015-01-01

413

Vector quantization  

NASA Technical Reports Server (NTRS)

During the past ten years Vector Quantization (VQ) has developed from a theoretical possibility promised by Shannon's source coding theorems into a powerful and competitive technique for speech and image coding and compression at medium to low bit rates. In this survey, the basic ideas behind the design of vector quantizers are sketched and some comments made on the state-of-the-art and current research efforts.

Gray, Robert M.

1989-01-01

414

Robotic application of a dynamic resultant force vector using real-time load-control: simulation of an ideal follower load on Cadaveric L4-L5 segments.  

PubMed

Standard in-vitro spine testing methods have focused on application of isolated and/or constant load components while the in-vivo spine is subject to multiple components that can be resolved into resultant dynamic load vectors. To advance towards more in-vivo like simulations the objective of the current study was to develop a methodology to apply robotically-controlled, non-zero, real-time dynamic resultant forces during flexion-extension on human lumbar motion segment units (MSU) with initial application towards simulation of an ideal follower load (FL) force vector. A proportional-integral-derivative (PID) controller with custom algorithms coordinated the motion of a Cartesian serial manipulator comprised of six axes each capable of position- or load-control. Six lumbar MSUs (L4-L5) were tested with continuously increasing sagittal plane bending to 8 Nm while force components were dynamically programmed to deliver a resultant 400 N FL that remained normal to the moving midline of the intervertebral disc. Mean absolute load-control tracking errors between commanded and experimental loads were computed. Global spinal ranges of motion and sagittal plane inter-body translations were compared to previously published values for non-robotic applications. Mean TEs for zero-commanded force and moment axes were 0.7 ± 0.4N and 0.03 ± 0.02 Nm, respectively. For non-zero force axes mean TEs were 0.8 ± 0.8 N, 1.3 ± 1.6 Nm, and 1.3 ± 1.6N for Fx, Fz, and the resolved ideal follower load vector FL(R), respectively. Mean extension and flexion ranges of motion were 2.6° ± 1.2° and 5.0° ± 1.7°, respectively. Relative vertebral body translations and rotations were very comparable to data collected with non-robotic systems in the literature. The robotically coordinated Cartesian load controlled testing system demonstrated robust real-time load-control that permitted application of a real-time dynamic non-zero load vector during flexion-extension. For single MSU investigations the methodology has potential to overcome conventional follower load limitations, most notably via application outside the sagittal plane. This methodology holds promise for future work aimed at reducing the gap between current in-vitro testing and in-vivo circumstances. PMID:23809771

Bennett, Charles R; Kelly, Brian P

2013-08-01

415

7/9/10 2:34 PMWHO | Human African trypanosomiasis: number of new cases drops to historically low level in 50 years Page 1 of 2http://www.who.int/neglected_diseases/integrated_media/integrated_media_hat_june_2010/en/index.html  

E-print Network

7/9/10 2:34 PMWHO | Human African trypanosomiasis: number of new cases drops to historically low tropical diseases > Integrated media related to NTD printable version Human African trypanosomiasis: number of human African trypanosomiasis (also known as sleeping sickness) reported to WHO has dropped below 10 000

Cross, George