Research into the relative importance of Tabanidae (Diptera) in mechanical disease transmission. IV. A contribution to the epidemiology of bovine trypanosomiasis in Africa.

The incidence of trypanosomiasis was studied in a herd of dairy cattle near Dar es Salaam over a period of 4 months. The apparent density of tsetse flies and prevalence of various species of Tabanidae were measured. There was no statistical correlation between the disease incidence and the seasonal occurrence of Tabanidae. Although anaplasmosis was concurrently transmitted by Tabanus taeniola on an economically significant scale in this herd and there was a high incidence of Trypanosoma vivax infections it was thought, however, that trypanosomes were transmitted by Tabanidae at an insignificant rate. The only measureable result of such mechanical transmission was a change of the T. vivax/T. congolense ratio in favour of T. vivax (69 per cent of the infections).