Recombinant DNA probes reveal simultaneous infection of tsetse flies with different trypanosome species.

The utility of recombinant DNA probes in the detection of natural trypanosome infection of tsetse flies has been assessed in Lambwe Valley, near the shores of Lake Victoria, Kenya. The tsetse flies were surveyed during two different seasons in 1988. Three different probes used each contained highly repetitive DNA sequences specific for a species or subspecies of trypanosomes of the Nanomonas subgenus. A fourth probe contained repetitive sequences common to trypanosome species of the Trypanozoon subgenus. Mixed mature or immature infections were detected in a variety of combinations in different individual tsetse flies. Such infections were detected in both the guts and mouthparts of some tsetse flies. Simultaneous natural infection of tsetse with the savannah type Trypanosoma congolense and Kilifi type T. congolense, T. congolense and Trypanosoma brucei or T. congolense and Trypanosoma simiae were demonstrated. The probes have thus been used to demonstrate the presence of Lambwe Valley, south-western Kenya, of a type of T. congolense first observed among trypanosome isolates obtained from sentinel cattle exposed to natural infection on a ranch at Kilifi on the Kenya coast. This type of T. congolense appears not to be confined to the coastal region nor to any particular species of tsetse flies and may contribute significantly to livestock morbidity in other areas of eastern Africa. In the Kilifi area, T. congolense was found primarily in Glossina austeni; in Lambwe valley, it was found in Glossina pallidipes.