EPIDEMIOLOGY OF BOVINE TRYPANOSOMIASIS IN KILIFI AND KWALE COUNTIES, COASTAL KENYA

Abstract

Trypanosomiasis is a neglected tropical disease of human and animal populations in sub saharan Africa. Tsetse fly is the cyclical vector that transmits trypanosome parasites to animals and humans causing Animal African Trypanosomiasis (AAT) and Human African Trypanosomiasis (HAT) respectively. Biting flies like Stomoxys and Tabanids are the mechanical vectors of the parasites. The main objective of this study was to determine the factors influencing prevalence of trypanosomiasis among the bovine and determine its social economic impacts to the people in Coastal Kenya. Bovine blood samples were analyzed microscopically for the infection and the disease prevalence was determined using 593 bovines (329 and 264) during dry (Dec-Feb) and wet (Jul-Sep) seasons respectively. The bovine body condition, age, sex and Packed Cell Volume (PCV) were determined. The density of the tsetse vectors was determined by deploying NGU standard sampling trap device using a total of 112 traps, 56 during wet and dry seasons respectively in each sampling site. Fly numbers were recorded and categorized to species, sexed and sorted as either tenerals or non-tenerals. Socioeconomic impact of tsetse and trypanosomiasis was investigated using structured questionnaire administered to 138 consenting respondents during the study. Data was analyzed using SPSS Version 20.0. Descriptive statistics was used to summarize the data and qualitative data was presented using frequency tables and figures. Analytical statistics (t-test, chi-square, Kruskal Wallis test and linear regression) were used to compare quantitative data. Results identified two species of trypanosome parasites namely Trypanosome congolense and Trypanosome vivax infecting the bovine population in the study areas. The overall prevalence of the infection was 12.54% and 9.80% in Kilifi and Kwale respectively. There was no significant difference in the prevalence of T. vivax and T.congolense between the two counties. The occurrence of trypanosomiasis was significantly associated with season (P=0.000), Breed (P=0.000) , Sex (P=0.000),age (P=0.000) and the PCV(P=0.003). The cumulative infection rate was highest in cattle with poor body condition (64.29% and 42.11%) followed by fair body condition (29.35% and 11.88%) in Kilifi and Kwale respectively. Adult animals significanly had the higher rate of infection at 75.76% (Kilifi 42.42%; Kwale 33.34%).Wet season was associated with the higher infection rate at 65.16% (Kilifi 31.82% and Kwale 33.34%). The seasonal variations in the prevalence of infection was significant (P < 0.05).Three species of tsetse,namely Glosina longipennis, G. pallidipes, and G. austeni and two genera of biting flies Stomoxys and Tabanus were identified. Fly/Trap/Day (FTD) captured in Kilifi was:5.2 and 2.93 during the wet and dry seasons respectively, whereas in Kwale it was 27.98 and 1.43 during wet and dry seasons. Various vector control approaches are used by the farmers in the area and they include animal spraying, bush clearing, use of insecticde impregnated targets, netting of zero grazing units and restriction of animals from tsetse infested areas. Poverty in the study area is strongly associated with AT. The study recommends that the national and county governments should prioritize trypanosomiasis control to boost livestock production in the coastal region. There is need for further study to determine the level of purchase of the trypanocidal drugs from agro-vet shops to contribute to disease surveillence in the coastal counties.