The complex epidemiology of Rhodesian sleeping sickness in Kenya and Uganda. III. The epidemiology in the endemic areas along the lake shore between the Nile and the Yala swamp.

The endemic Rhodesian sleeping sickness belt along the shore of Lake Victoria between the Nile and the Yala swamp consists of two ecologically different areas: the Busoga belt and the Samia belt. The Busoga belt is a country of forest and forest relics, full of game, with a high density of Glossina fuscipes fuscipes but also inhabited by G. pallidipes, and with a people encroaching on the northern border who pass the forest on their way to the lake to catch and buy fish, but who seldom penetrate deep in the forest to hunt. The Samia belt is a country of dense bush in savanna, with less and smaller game, with forest, but with a relatively high density of G. pallidipes, and with a people who will not only pass the bush on their way to catch and buy fish at the lake, bur who also like hunting in bush and forest. From sex-, age-, seasonal and tribal incidence, from the incidence among different professions such as fishermen, fishmongers and cultivators, and from the differences in incidence encountered between the Busoga belt and the Samia belt, it is concluded: that nearly all women and children, most cultivators and part of the fishermen who contract sleeping sickness in these areas, become infected near their homes by G. pallidipes: this occurs mainly in the dense bush area. that most fishmongers, some cultivators and some fishermen become infected on their way to the lake shore, mainly by G. pallidipes; this occurs not only in the dense bush area, but also in the forest area. that fishermen, who become infected during trips, mainly contract their infection some distance away from the lake shore where they meet G.pallidipes. that transmission at the lake shore itself is rare and that G. fuscipes fuscipes only plays a minor role in the transmission of the disease in the areas under consideration. that man is not a good reservoir for Rhodesian sleeping sickness and that man-fly-man transmission is a rare occurrence. that game animals, particularly bushbuck and duiker, are the main source of infection for the flies which transmit the disease to man. that the sleeping incidence in man might merely be a reflexion of the incidence in the natural reservoir and that the factors influencing the latter will have to be studied to understand the former.