Distribution Of Tsetse Flies And Significance To The Control Of African Trypanosomiasis In Busia County, Kenya

Background : Tsetse flies are the cyclical vectors of both human and animal diseases in Sub-Saharan Africa. Since 2012, Kenya has not recorded a case of human trypanosomiasis. However, African animal trypanosomiasis continues to be a major challenge to livestock production despite decades of control efforts. This study aimed to determine the prevalence of tsetse flies in Busia County post intervention and to build the capacity of local inhabitants in vector control activities. Methods : This cross-sectional study was conducted between May 2018 and December 2018 in Teso South and Teso North sub-counties. Odour-baited biconical traps were deployed for 48 hours in each sampling area and captured tsetse flies were analysed for trypanosome infections. Additionally, training and field demonstrations were conducted as part of capacity building to enhance participation of local inhabitants in tsetse control activities. Results : In Teso South sub-county, 62 tsetse flies were captured in Kwangamor, six in Obekai and 14 in Ngelechom sites. All the captured tsetse flies were classified as G. fuscipes fuscipes . In Teso North sub-county sites of Kapesur, three G. pallidipes were captured, while the Ikapolok sites yielded 12 tsetse flies all G. fuscipes fuscipes. The apparent density of tsetse flies was between 0.08 and 1.55 flies-per trap-per-day across the five study areas with G. fuscipes fuscipes being the dominant species. Microscopic examination of 72 G. fuscipes fuscipes identified three T vivax and one T. congolense positive tsetse flies. No trypanosomes were observed in all the G. pallidipes . Overall infection rate of 1.39% and 4.17% was observed for T. congolense and T. vivax respectively. With regards to capacity building, a total of 26 community members were trained on tsetse fly control activities. Out of which five were selected as focal persons and were further trained on integrated vector management techniques and tsetse survey methods. Conclusions : Tsetse in South low density, harbour

Trypanosome parasites transmitted mainly through bites of infected tsetse flies (Glossina spp) are known causes of both humans and animals diseases affecting the poor and marginalised populations of Sub-Saharan Africa. In humans, two protozoan parasites: Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense (1) cause Human African Trypanosomiasis (HAT) also called "sleeping sickness". Infections with T. b. gambiense (gHAT) are usually chronic and mainly found in Western and Central Africa, while infections with T. b. rhodesiense (rHAT) are acute in nature and mainly found in East and South Africa (2). The role of animals in the maintenance of gHAT transmission is still unclear, while rHAT transmission, conversely, involves both wild animals and domestic animals as reservoirs (3)(4)(5)(6)(7). Furthermore, Game parks and animal conservation areas have become the main sources of exposure to travellers and tourists (8)(9)(10)(11). Over the years, through the concerted efforts of the World Health Organization (WHO) and other stakeholders such as National governments, Non-governmental Organizations and pharmaceutical companies, have substantially reduced the number of HAT cases. This success has necessitated the current WHO target of eliminating gHAT in endemic foci by the year 2030 (7,(12)(13)(14). Kenya has no recent autochthonous case of HAT apart from two cases detected in non-endemic countries from tourists who had visited the Masai-Mara National Reserve in 2012 (10,13).
On the contrary, most of the Sub-Sahara Africa tsetse endemic countries still suffer huge economic losses due to African Animal Trypanosomiasis (AAT) also called "nagana" that is caused by three Trypanosoma species: Trypanosoma brucei brucei, Trypanosoma congolense and Trypanosoma vivax.
The disease continues to affect the economic welfare and livelihoods of many farmers and imposing major constraints to livestock health and productivity (15,16). Furthermore, the surge in human population in many parts of Africa has led to increased land pressure and encroachment into tsetse infested areas for settlement and farming thereby increasing animal/human-fly contacts and potential for contracting trypanosomiasis (17).
In Kenya agriculture accounts for over 24% of the country's Gross Domestic Product (GDP); of which 12% is from the livestock sector. Therefore, AAT effects on agricultural production translates to a direct threat to the economy, food security and human welfare (18,19). The Kenya tsetse and trypanosomiasis eradication council (KENTTEC) recognises distinct diverse zones or "tsetse fly belts" in the country that are occupied by eight tsetse fly species. For instance, the Lake Victoria basin tsetse fly belt encompasses three counties in the western Kenya i.e. Busia, Bungoma and Siaya, and extends to parts of Uganda and Tanzania. This region is characterised by forested riverbanks, patches of dense vegetation and forested wetlands which are ideal habitats for tsetse flies (20,21). It is a common practice for businessmen in this region to acquire livestock for beef from the cattle markets of Eastern Uganda, a practice that potentially could lead to the introduction of new trypanosomes and other animal diseases. Not long ago, cases of chemo-resistance to existing trypanocides have been reported in Uganda (22)(23)(24). Therefore, there is need for regular monitoring and surveillance of African animal trypanosomiasis and resistance to trypanocide drugs in the region.
Previous studies have shown that climate change coupled with human activities tend to modify environmental and biological conditions that affect the vector, host and parasites interactions (25)(26)(27). In addition, existing socio-economic and cultural factors also contribute to disease incidence and outcomes (28,29). Over the past decade, Busia County has undergone rapid environmental changes, increased encroachment and use of wetlands and riverine for farming activities. Changes in land-use, deforestation, erosion and loss of biodiversity may affect the prevalence, distribution of tsetse flies, and disease transmission dynamics. Current data on tsetse distribution and population density given the new epidemiological settings in the county is lacking. To substantially achieve reduction in AAT and to maintain a downward trend in disease incidence, training of local inhabitants in vector control activities among other measures is paramount. This study set out to determine the current status with regards to tsetse distribution and to enhance local capacity in vector control activities.

Study area
The study was conducted in Busia County located in western Kenya. Based on the historical burden of African trypanosomiasis, Teso South and Teso North sub-counties were selected for the survey. As mentioned earlier, Busia is within the Lake Victoria basin tsetse fly belt that includes other counties such as Bungoma to the north and Siaya to the southwest. It also borders Lake Victoria to the southeast and the Republic of Uganda to the west (Additional file 1). The tsetse surveys were carried out in five administrative villages namely: Kwangamor, Obekai and Ngelechom in Teso South subcounty; Kapesur and Ikapolok in Teso North sub-county. Subsistence farming and traditional rearing of livestock (cattle and small ruminants) are the main economic activities in the sampled areas.

Study Design
This cross-sectional survey was conducted as part of post intervention evaluation to determine the prevalence of tsetse flies in the five sites following past control activities by the Farming in Tsetse Controlled Areas (FITCA) project. In addition, capacity building of the local communities in tsetse control activities was done to enhance participation and for sustainability of tsetse control activities.

Results
Local community participation and capacity building A total of 26 community members (mostly representatives of farmers) were trained on integrated vector management and trypanosomiasis control approaches. In addition, a team of five focal persons was further trained on basic tsetse biology, vector control and survey methods.

Tsetse Fly Apparent Density
The tsetse fly survey activities were carried out in five study sites. Three in Teso South sub-county, namely: Kwangamor, Obekai and Ngelechom; two in Teso North sub-county namely: Kapesur and Ikapolok (Fig. 1). A total of twenty trapping points were identified for each site where the odour-baited biconical tsetse traps were deployed for a period of 48 hours before harvesting the catches.
In Teso South sub-county, Kwangamor trapping site, a total of 62 tsetse flies and 23 biting flies of Stomoxys spp were captured. In the Obekai trapping site, six tsetse flies, two Tabanidae and two  (Table 1). Kwangamor site had the highest apparent tsetse fly density of (1.55) while Kapesur site was the lowest (0.08). Details of the location of traps with tsetse flies is shown in Fig. 2.
The respective GPS coordinates for the traps is also provided (Additional file 2).

Trypanosome Infection Rates
To determine tsetse fly infections with Trypanosoma spp, a total of 75 non teneral tsetse flies from the five study sites were dissected. Four (4) tsetse flies were positive for the Trypanosoma spp ( Table 2) Kwangamor and Obekai sites is indicated in (Fig. 3). Table 2 Trypanosoma parasite positivity rates identified by dissection of all non teneral tsetse flies The Kenya National Council for Science Technology and Innovation provided a research permit (Ref: NACOSTI/P/18/76628/18964) for the study to be conducted in Busia County.

Consent to publish
Not applicable flies in the five study sites after 48 hours deployment.

Supplementary Files
This is a list of supplementary files associated with this preprint. Click to download.