Epidemiology of tsetse flies and trypanosomes with a case study in Ethiopia

Abstract

The aim of this study was to quantify the abundance of tsetse flies using traditional traps and using anti-tsetse saliva ELISA test and the trypanosome infection prevalence in the tsetse flies and cattle. An area-wide tsetse fly and cattle trypanosomosis survey was conducted in Ethiopia. Groups of mice and pigs were experimentally exposed to G. m. morsitans bite to develop total saliva and rTsal ELISA tests that are capable to detect and monitor the induced anti-saliva antibodies of tsetse following host exposure to tsetse bite. A meta-analysis was conducted on prevalence of trypanosome infection in tsetse flies in the field or in laboratory-controlled conditions. Published information available since 1950s was reviewed. The findings indicated that tsetse flies and trypanosome infections of cattle are widely distributed in Ethiopia and their abundance is affected by spatial factors such as altitude, river drainage system, local factors at PA level (presence of game reserves and land use/encroachment). There was no significant association between tsetse density and prevalence of trypanosomes in cattle. Total tsetse saliva and recombinant Tsal1 protein coated indirect ELISA are sensitive immunological probes to detect contact with tsetse flies. The new serological test at hand is a sensitive indicator that can differentiate regimens of tsetse fly bites (various degree of exposure of animals) and that can also detect tsetse fly bite after a prolonged period without exposure. The overall prevalence of trypanosome infection in tsetse fly populations was 10.3% and 31.0% for the field survey data and laboratory experiment data, respectively. Both spatial (country) and temporal (year of publication) variation are noticed in trypanosome infection prevalence of field collected tsetse flies. The lack of association between tsetse density and prevalence of trypanosomes in cattle needs further investigation on the role of Tabanus and Stomoxys for mechanical trypanosome transmission. Due to the ongoing interventions, the vector could decline to a low level beyond the fly catching capacity by traps. The current serological ELISA test could be an important surveillance tool with sensitive diagnostic value.