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Enyaru J.C.,Makerere University | Ouma J.O.,Kenya Agricultural Research Institute | Malele I.I.,Tsetse and Trypanosomiasis Research Institute
Trends in Parasitology | Year: 2010

Understanding what the trypanosome pathogens are, their vectors and mode of transmission underpin efforts to control the disease they cause in both humans and livestock. The risk of transmission is estimated by determining what proportion of the vector population is carrying the infectious pathogens. This risk also depends on the infectivity of the trypanosomes to humans and livestock. Most livestock pathogens are not infective to humans, whereas the two sub-species that infect humans also infect livestock. As with other infectious diseases, we can therefore trace the foundation of many continuing disease control programs for trypanosomiasis to the discovery of the pathogens and their vectors more than a century ago. Over this period, methods for detecting and identifying trypanosomes have evolved through various landmark discoveries. This review describes the evolution of methods for identifying African trypanosomes in their tsetse fly vectors. © 2010 Elsevier Ltd.

Ouma J.O.,Kenya Agricultural Research Institute | Malele I.I.,Tsetse and Trypanosomiasis Research Institute | Ngure R.M.,Egerton University | Rutto J.J.,Kenya Agricultural Research Institute | Enyaru J.,Makerere University
PLoS ONE | Year: 2011

Tsetse flies are notoriously difficult to observe in nature, particularly when populations densities are low. It is therefore difficult to observe them on their hosts in nature; hence their vertebrate species can very often only be determined indirectly by analysis of their gut contents. This knowledge is a critical component of the information on which control tactics can be developed. The objective of this study was to determine the sources of tsetse bloodmeals, hence investigate their feeding preferences. We used mitochondrial cytochrome c oxidase 1 (COI) and cytochrome b (cytb) gene sequences for identification of tsetse fly blood meals, in order to provide a foundation for rational decisions to guide control of trypanosomiasis, and their vectors. Glossina swynnertoni were sampled from Serengeti (Tanzania) and G. pallidipes from Kenya (Nguruman and Busia), and Uganda. Sequences were used to query public databases, and the percentage identities obtained used to identify hosts. An initial assay showed that the feeds were from single sources. Hosts identified from blood fed flies collected in Serengeti ecosystem, included buffaloes (25/40), giraffes (8/40), warthogs (3/40), elephants (3/40) and one spotted hyena. In Nguruman, where G. pallidipes flies were analyzed, the feeds were from elephants (6/13) and warthogs (5/13), while buffaloes and baboons accounted for one bloodmeal each. Only cattle blood was detected in flies caught in Busia and Uganda. Out of four flies tested in Mbita Point, Suba District in western Kenya, one had fed on cattle, the other three on the Nile monitor lizard. These results demonstrate that cattle will form an integral part of a control strategy for trypanosomiasis in Busia and Uganda, while different approaches are required for Serengeti and Nguruman ecosystems, where wildlife abound and are the major component of the tsetse fly food source. © 2011 Muturi et al.

Adams E.R.,University of Bristol | Adams E.R.,Koninklijk Instituut Voor Of Tropen Kit Biomedical Research | Hamilton P.B.,University of Exeter | Rodrigues A.C.,University of Sao Paulo | And 4 more authors.
Parasitology | Year: 2010

Salivarian trypanosomes pose a substantial threat to livestock, but their full diversity is not known. To survey trypanosomes carried by tsetse in Tanzania, DNA samples from infected proboscides of Glossina pallidipes and G. swynnertoni were identified using fluorescent fragment length barcoding (FFLB), which discriminates species by size polymorphisms in multiple regions of the ribosomal RNA locus. FFLB identified the trypanosomes in 65 of 105 (619%) infected proboscides, revealing 9 mixed infections. Of 7 different FFLB profiles, 2 were similar but not identical to reference West African Trypanosoma vivax; 5 other profiles belonged to known species also identified in fly midguts. Phylogenetic analysis of the glycosomal glyceraldehyde phosphate dehydrogenase gene revealed that the Tanzanian T. vivax samples fell into 2 distinct groups, both outside the main clade of African and South American T. vivax. These new T. vivax genotypes were common and widespread in tsetse in Tanzania. The T. brucei-like trypanosome previously described from tsetse midguts was also found in 2 proboscides, demonstrating a salivarian transmission route. Investigation of mammalian host range and pathogenicity will reveal the importance of these new trypanosomes for the epidemiology and control of animal trypanosomiasis in East Africa. © 2009 Cambridge University Press.

Nakao R.,Hokkaido University | Stromdahl E.Y.,U.S. Army | Magona J.W.,Hokkaido University | Magona J.W.,National Livestock Resources Research Institute NaLIRRI | And 10 more authors.
BMC Microbiology | Year: 2010

Background. The rickettsial bacterium Ehrlichia ruminantium is the causative agent of heartwater, a potential zoonotic disease of ruminants transmitted by ticks of the genus Amblyomma. The disease is distributed in nearly all of sub-Saharan Africa and some islands of the Caribbean, from where it threatens the American mainland. This report describes the development of two different loop-mediated isothermal amplification (LAMP) assays for sensitive and specific detection of E. ruminantium. Results. Two sets of LAMP primers were designed from the pCS20 and sodB genes. The detection limits for each assay were 10 copies for pCS20 and 5 copies for sodB, which is at least 10 times higher than that of the conventional pCS20 PCR assay. DNA amplification was completed within 60 min. The assays detected 16 different isolates of E. ruminantium from geographically distinct countries as well as two attenuated vaccine isolates. No cross-reaction was observed with genetically related Rickettsiales, including zoonotic Ehrlichia species from the USA. LAMP detected more positive samples than conventional PCR but less than real-time PCR, when tested with field samples collected in sub-Saharan countries. Conclusions. Due to its simplicity and specificity, LAMP has the potential for use in resource-poor settings and also for active screening of E. ruminantium in both heartwater-endemic areas and regions that are at risk of contracting the disease. © 2010 Nakao et al; licensee BioMed Central Ltd.

Malele I.I.,Tsetse and Trypanosomiasis Research Institute | Manangwa O.,Tsetse and Trypanosomiasis Research Institute | Nyingilili H.H.,Tsetse and Trypanosomiasis Research Institute | Kitwika W.A.,Tsetse and Trypanosomiasis Research Center | And 5 more authors.
Journal of Invertebrate Pathology | Year: 2013

Sterile Insect technique is an important component in area-wide integrated tsetse control. The presence of the salivary glands hypertrophy virus (SGHV) in the wild tsetse, which are the seeds for colony adaptations in the laboratory has become a stumbling block in establishing and maintaining colonies in the laboratory. The virus is transmitted both vertically (in the wild) and horizontally (in the laboratory). However, its prevalence is magnified in the laboratory as a result of the use of in vitro membrane feeding regimen. Fly species of Glossina fuscipes fuscipes, G. pallidipes, G. morsitans and G. swynnertoni were collected from the coastal and inland areas of Tanzania and virus infection rates were assessed microscopically and by PCR. The data showed that in a period of 4. years, the virus was present in all species tested irrespective of their ages, sex, and season of the year. However, infection levels differed among species and from one location to another. Symptomatic infection determined by dissection was 1.2% (25/2164) from the coast as compared to 0.4% (6/1725) for inland collected flies. PCR analysis indicated a higher infection rate of 19.81% (104/525) of asymptomatic flies. From these observations, we conclude that care should be taken when planning to initiate tsetse laboratory colonies for use in SIT eradication program. All efforts should be made to select non-infected flies when initiating laboratory colonies and to try to minimize the infection with SGHV. Also management of SGHV infection in the established colony should be applied. © 2013 International Atomic Energy Agency.

Mramba F.,Tsetse and Trypanosomiasis Research Institute | Oloo F.,Tsecon Consultants | Byamungu M.,Tsetse and Trypanosomiasis Research Institute | Krober T.,University of Neuchatel | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2013

Background: Here we set out to standardize long-lasting, visually-attractive devices for Glossina swynnertoni, a vector of both human and animal trypanosomiasis in open savannah in Tanzania and Kenya, and in neighbouring conservation areas used by pastoralists. The goal was to determine the most practical device/material that would induce the strongest landing response in G. swynnertoni for use in area-wide population suppression of this fly with insecticide-impregnated devices. Methods and Findings: Trials were conducted in wet and dry seasons in the Serengeti and Maasai Mara to measure the performance of traps and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a simple enumerator at these remote locations to compare trapping efficiencies of devices. Independent of season or presence of chemical baits, targets in phthalogen blue or turquoise blue cloth with adhesive film were the best devices for capturing G. swynnertoni in all situations, catching up to 19 times more flies than pyramidal traps. Baiting with chemicals did not affect the relative performance of devices. Fly landings were two times higher on 1 m2 blue-black targets as on pyramidal traps when equivalent areas of both were covered with adhesive film. Landings on 1 m2 blue-black targets were compared to those on smaller phthalogen blue 0.5 m2 all-blue or blue-black-blue cloth targets, and to landings on all-blue plastic 0.32-0.47 m2 leg panels painted in phthalogen blue. These smaller targets and leg panels captured equivalent numbers of G. swynnertoni per unit area as bigger targets. Conclusions: Leg panels and 0.5 m2 cloth targets show promise as cost effective devices for management of G. swynnertoni as they can be used for both control (insecticide-impregnated cloth) and for sampling (rigid plastic with insect glue or adhesive film) of populations. © 2013 Mramba et al.

Auty H.K.,University of Edinburgh | Auty H.K.,University of Glasgow | Picozzi K.,University of Edinburgh | Malele I.,Tsetse and Trypanosomiasis Research Institute | And 3 more authors.
PLoS Neglected Tropical Diseases | Year: 2012

Background: Measuring the prevalence of transmissible Trypanosoma brucei rhodesiense in tsetse populations is essential for understanding transmission dynamics, assessing human disease risk and monitoring spatio-temporal trends and the impact of control interventions. Although an important epidemiological variable, identifying flies which carry transmissible infections is difficult, with challenges including low prevalence, presence of other trypanosome species in the same fly, and concurrent detection of immature non-transmissible infections. Diagnostic tests to measure the prevalence of T. b. rhodesiense in tsetse are applied and interpreted inconsistently, and discrepancies between studies suggest this value is not consistently estimated even to within an order of magnitude. Methodology/Principal Findings: Three approaches were used to estimate the prevalence of transmissible Trypanosoma brucei s.l. and T. b. rhodesiense in Glossina swynnertoni and G. pallidipes in Serengeti National Park, Tanzania: (i) dissection/microscopy; (ii) PCR on infected tsetse midguts; and (iii) inference from a mathematical model. Using dissection/microscopy the prevalence of transmissible T. brucei s.l. was 0% (95% CI 0-0.085) for G. swynnertoni and 0% (0-0.18) G. pallidipes; using PCR the prevalence of transmissible T. b. rhodesiense was 0.010% (0-0.054) and 0.0089% (0-0.059) respectively, and by model inference 0.0064% and 0.00085% respectively. Conclusions/Significance: The zero prevalence result by dissection/microscopy (likely really greater than zero given the results of other approaches) is not unusual by this technique, often ascribed to poor sensitivity. The application of additional techniques confirmed the very low prevalence of T. brucei suggesting the zero prevalence result was attributable to insufficient sample size (despite examination of 6000 tsetse). Given the prohibitively high sample sizes required to obtain meaningful results by dissection/microscopy, PCR-based approaches offer the current best option for assessing trypanosome prevalence in tsetse but inconsistencies in relating PCR results to transmissibility highlight the need for a consensus approach to generate meaningful and comparable data. © 2012 Auty et al.

Malele I.I.,Tsetse and Trypanosomiasis Research Institute
Tanzania Journal of Health Research | Year: 2011

Tsetse flies are the vectors of trypanosomes, the causative organisms of trypanosomiasis, nagana, in animals and sleeping sickness in man. In Tanzania, tsetse transmitted trypanosomiasis is one of the most important disease affecting both animals and humans. About 40% of land suitable for grazing and areas with high agricultural potential are currently tsetse infested. It is estimated that about 4.4 million livestock and 4 million people are at risk of contracting tsetse borne trypanosomiasis. African animal trypanosomiasis (AAT) causes loss in animals due to mortality and reduced milk yield, which is estimated at US$ 7.98 million annually. Even after 50 years of independence, Human African Trypanosomiasis (HAT) or Sleeping Sickness is still one of the major public health problems with about 300 cases being reported annually. Tsetse control has been sporadic and uncoordinated hence no tangible results have been accrued since independence despite the fact that technologies which have facilitated tsetse control in other places are available. Fifty years of independence have seen shrinkage of tsetse belt to 43% in 16 surveyed regions. Opportunities for future are wide open if tsetse control will involve all stakeholders, who are directly or indirectly affected by the tsetse problem; if tsetse and trypanosomiasis eradication will adopt an area wide and participatory approach with emphasis on environmentally and user friendly techniques for expanded livestock sector; improved food security and livelihood in affected communities, for achievement of the millennium development goals.

Malele I.,Tsetse and Trypanosomiasis Research Institute | Nyingilili H.,Tsetse and Trypanosomiasis Research Institute | Msangi A.,Tsetse and Trypanosomiasis Research Institute
African Journal of Agricultural Research | Year: 2011

Tsetse survey to re-define its distribution limit in Tanzania was conducted from 2005 to 2009. Based on the old tsetse infestation map, tsetse sampling using odour baited biconical traps were deployed and emptied after 24 h during the onset of dry season. The survey covered the southern, western, northern and north eastern regions of the country. Obtained results indicated that Glossina morsitans sl and G. pallidipes were the dominant and widely distributed tsetse species, although their boundaries had shrank. Changes in land use, which include human settlement and associated activities, infrastructure development and land reform policies, were the major reason for the new tsetse distribution limit. Movement and settlement of huge stocks of insecticide baited livestock in once tsetse infested areas significantly altered the ecology of favored tsetse habitats and their hosts leading to the disappearance of tsetse breeding sites and tsetse species. Human population increase in formally tsetse infested areas also contributed to the disappearance of tsetse. The most affected regions were found to be Rukwa and Mtwara. Chi square test indicated a significant difference on number of collected tsetse in different location; highest density observed in game reserve and the lower in areas near wild animal migratory corridor and protected forest areas. Tsetse flies were confined to protected areas, which include national parks, game and forest reserves. The new tsetse distribution limit is set to influence the epidemiology of African Trypanosomiasis, tsetse control initiatives and the future of livestock sector in Tanzania. © 2011 Academic Journals.

PubMed | Tsetse and Trypanosomiasis Research Institute
Type: Journal Article | Journal: Journal of vector borne diseases | Year: 2011

Different methods have been developed for tsetse and trypanosomiasis control or eradication but all these have their specific advantages and limitations. However, a combination of methods could be used as part of an Area-wide Integrated Pest Management (AWPM). The sterile insect technique (SIT) as a technique of choice for eradication of tsetse flies requires mass production of flies in the laboratories. Since tsetses are exclusively haemotophogous insects, a quality blood diet is needed for maintenance of flies with optimum production. The aim of this study was to establish the optimum storage time of blood diet for tsetse colonies.A total of 450 flies Glossina austeni were fed on different batches of blood (collected in 2004, 2005, 2006, 2007 and 2008) three times a week. Pupae were collected daily and mortality checks were done on weekly basis. The quality of the blood diet was measured by observation of tsetse production parameters including survival, pupae production and size.The survival of flies fed on 2004 and 2006 batches had lower survival compared to the rest of the batches. Also the 2005 batch had a significant higher number of pupae compared to the production in other treatments. The 2004 and 2005 batches had more of small pupae (class A & B) compared to the other batches.There was a significant difference between the blood batches and the production parameters were better in the last three years, i.e. 2008, 2007 and 2006. Therefore, this study recommends three years to be an optimum storage time for blood diet under regional conditions. Also the storage temperature conditions should remain stable at -20C.

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