New concepts in the epidemiology of Rhodesian sleeping sickness.

The results from recent studies of a number of outbreaks of T. rhodesiense sleeping sickness have enabled workers in this field to reconsider the epidemiology of the disease.The known limits of the distribution of the disease are defined and its extension to 2 new areas in Teso district, Uganda, and to the south-western district of Ethiopia are reported. Human reaction to the T. rhodesiense infection is discussed in detail and the importance of healthy carriers is emphasized. The old belief that transmission of the disease is restricted to Glossina of the morsitans group is discounted, as recent evidence shows that G. fuscipes is an equally efficient transmitter. The susceptibility of Glossina to infection with T. rhodesiense and the factors which play a role in the transmissibility of the parasite to animal hosts are outlined.The economic, social, and climatic factors which operate to increase man-fly contact in various endemic areas are described and the ecological relationship of the 3 components of the host-vector-parasite complex is reviewed. The fact that Rhodesian sleeping sickness is a zoonosis is stressed, and the role of the movements of man, game and domestic animals in spreading the infection is discussed. The need for further study of the recent epidemic in Ethiopia is urged as it seems likely to provide further new information. The merits of the immunological approach to the control of the disease in both man and his beasts is discussed, but at present this appears to be impracticable.