Geospatial Analysis of Tsetse Infestation and Animal African Trypanosomiasis in Busia County, Kenya.

Abstract

African trypanosomiasis (AT) is a vector-borne disease caused by protozoan parasites of the genus Trypanosoma, primarily transmitted through the bite of infected tsetse flies in the genus Glossina. The disease is a major constraint to livestock production, causing reduced productivity, anemia, and mortality in affected animals. A cross-sectional study was conducted from November to December 2024 to assess the spatial prevalence of AAT in cattle as well as tsetse fly abundance in Busia County, Kenya. A total of 762 cattle randomly selected from seven villages in Busia County were screened for AAT using the quantitative buffy coat technique. Packed cell volume (PCV) values were also determined. A tsetse survey was done by deploying 60 tsetse odor-baited biconical traps in thickets and along streams in Funyula, Butula, and Teso North subcounties to estimate tsetse flies' distribution and density. Overall reported prevalence of AAT was 6.82% (95% CI: 5.2-8.80). Trypanosoma vivax reported the highest prevalence amongst the reported species at 4.72%, which was significant (p = 0.006). Age, grazing system and breed significantly (p < 0.05) increased odds for trypanosome infection in cattle. Overall mean PCV for the study population was 24.82%. AAT-positive cattle registered significantly lower PCV (22.7 ± 3.38%) compared with 26.94 ± 1.71.0% in the trypanosome-negative cattle (p = 0.027). Two tsetse fly species were captured, with an apparent density ranging from 0.00 to 0.35 across the study sites. Species-wise, tsetse catches were not statistically different in fly trap densities (FTD) between Glossina pallidipes (Gpd) and Glossina fuscipes fuscipes (p = 0.429), despite Gpd exhibiting a higher mean FTD (0.117, SD = 0.175). The study confirmed that AAT is still endemic in Busia County, with evidence that transmission is localized rather than widespread.