Trypanosome infection rates inGlossina swynnertoniandG. pallidipesin Ikoma, Musoma District, Tanzania

Abstract

In a survey of animal trypanosomiasis in Musoma District, carried out in October and November 1970, 6344G. swynnertoniwere collected from six different localities of the Ikoma-Serengeti area and 623G. pallidipesfrom Ikoma. These were dissected and examined for trypanosome infections. The mean infection rates ofvivax-type inG. swynnertoniandG. pallidipeswere 12.6% and 7.5%, respectively. Thecongolensegroup infection rates were 2.0% inG. swynnertoniand 1.8% inG. pallidipes. No salivary gland infection was encountered. The incidence of vivax- and congolense-type infections in general increased with age of both the tsetse species, suggesting that the latter can become infected with these trypanosome types at all ages. The infection rate among female tsetse was higher than among males in the six wing-fray categories. This was due to the slower rate of fraying of the wings with age of the former, so that at each wing-fray category the females were generally older than the males.Vivax-type greatly exceededcongolense-type infection rate in bothG. swynnertoniandG. pallidipes. It is suggested that this probably reflects the known greater infectivity of the former group of trypanosomes toGlossina. It is concluded that in Ikoma, where game functions as the reservoir of animal trypanosomiasis and where infected tsetse are abundant, the domestic animals are exposed to a continuous trypanosome challenge.