The distribution and epidemiology of bovine trypanosomosis in Malawi

A survey to update the distribution and clarify the epidemiology of bovine trypanosomosis in Malawi was conducted between 1995-97. Use was made of parasitological and serological (anti-trypanosomal antibody-detection Enzyme-Linked Immunosorbent Assay (ELISA) diagnostic methods. Trypanosomal infections were detected in cattle sampled adjacent to known tsetse foci. The distribution of cattle with anti-trypanosomal antibodies indicated that the distribution of bovine trypanosomosis was more widespread than the parasitological prevalence data suggested. This is attributed to the seasonal movement of tsetse (mainly Glossina morsitans morsitans and G. pallidipes) from its prime habitat and the presence of localized foci of G. brevipalpis. The odour-baited, insecticide-treated, target barriers along the edge of Kasungu National Park and the Nkhotakota Game Reserve appeared to be effective in preventing tsetse from moving outside the game areas and contacting cattle. The anti-trypanosomal antibody-detection ELISA proved to be a useful tool in establishing the distribution of bovine trypanosomosis. Moreover, the distribution and prevalence of cattle with anti-trypanosomal antibodies was instrumental in clarifying the epidemiology of bovine trypanosomosis in Malawi. The anti-trypanosomal antibody-detection ELISA had high sensitivity in detecting Trypanosoma congolense infections. In parasitologically negative animals, the average packed cell volume was higher in those that had no anti-trypanosomal antibodies. The packed cell volume decreased with increasing antibody titre.