ABSTRACT
Human African trypanosomiasis (HAT), which is also known as sleeping sickness, has for several decades been one of the most important parasitic infections affecting man in the African continent. The disease is caused by protozoan parasites of the Trypanosoma species, with the East African form of the disease caused by Trypanosoma brucei rhodesiense and the West African form caused by Trypanosoma brucei gambiense. The disease is fatal if left untreated. The parasites in both cases are transmitted by the tsetse fly of the genus Glossina so that the control of this insect vector is a major challenge in the fight against HAT. A landmark World Health Organization (WHO) report published in 1986 (1) estimated that 50 million people worldwide are at risk of developing HAT, and it is likely that the current figure is closer to 60 million. The disease is a major health problem in Africa and occurs in no less than 36 countries in subSaharan Africa between latitudes 14(N and 29(S reflecting the distribution of the tsetse fly (2) (Fig. 1). The area of land which is effectively “held captive” by the tsetse fly is massive and in the region of 10 million square km (3). Precise figures for the incidence of HAT are very difficult to define in large part because only a small percentage (about 5-15%) of the susceptible population is usually under active surveillance and the disease is often inadequately reported (2). In an insightful analysis of the problem, Kuzoe (2) reported in 1993 that
about 25,000 new cases are reported annually. However, it is likely that the true incidence of the disease is in the region of 300,000 cases per year (4).
