Bovine Trypanosomiasis

Abstract

African trypanosomiasis in cattle represents a major constraint to agricultural and socio-economic development in vast areas of Africa. The disease is caused principally by three species of trypanosome (Trypanosoma congolense, T. vivax and T. brucei) which are transmitted by several species of tsetse flies (Glossina) Trypanosomiasis in cattle results in poor productivity and mortality. The widespread nature of the disease is due to the distribution of tsetse, the ability of the trypanosomes to escape host defense mechanisms by undergoing antigenic variation and by their capacity to infect a large variety of other hosts, including wild game. Cattle can also act as carriers of the human pathogen T. b. rhoclesiense. Following the intradermal inoculation of trypanosomes by the tsetse fly into a susceptible host, there is proliferation of trypanosomes within the skin resulting in a localized skin reaction, known as the chancre, which develops before the appearance of parasites in the bloodstream.

Infected animals suffer from a severe anemia and there is widespread tissue damage affecting organs such as the heart, skeletal muscles, endocrine system and reproductive tract. The lymphoid system undergoes marked changes characterized initially, by intense proliferation associated with hypergammaglobulinemia and later, by depletion. Definitive diagnosis depends on demonstration of the trypanosome in blood samples. No field vaccine is available for bovine trypanosomiasis, and the methods currently employed for control include chemotherapeutic and chemoprophylactic drugs, tsetse eradication or control and the use of trypanotolerant cattle.