African trypanosomiasis, also known as sleeping sickness, is a severe disease that is fatal if left untreated. The causative agents are protozoan parasites of the genus Trypanosoma, which enter the bloodstream via the bite of blood-feeding tsetse flies (Glossina spp.). The acute form of the disease attributable to Trypanosoma brucei rhodesiense, widespread in eastern and southern Africa, is closely related to a common infection of cattle known as N'gana, which restricts cattle-rearing in many prime areas of Africa. The chronic form caused by T.b. gambiense is found in western and central Africa.
Cattle and other wild mammals act as reservoir hosts of the parasites. Tsetse flies can acquire parasites by feeding on these animals or on an infected person. Incubation time usually varies from three days to a few weeks for T.b. rhodesiense, and several weeks to months for T.b. gambiense. Inside the human host, trypanosomes multiply and invade most tissues. Infection leads to malaise, lassitude and irregular fevers. Early symptoms, which include fever and enlarged lymph glands and spleen, are more severe and acute in T.b. rhodesiense infections. Advanced symptoms include neurological and endocrine disorders. As the parasites invade the CNS, mental deterioration begins, leading to coma and death.
Sleeping sickness claims comparatively few lives annually, but the risk of major epidemics means that surveillance and ongoing control measures must be maintained, especially in sub-Saharan Africa where 36 countries have epidemiological risk. Control relies mainly on systematic surveillance of at-risk populations, coupled with treatment of infected people. In addition, reduction of tsetse fly numbers plays a significant role, especially against the rhodesiense form of the disease. In the past, this has involved extensive clearance of bush to destroy tsetse fly breeding and resting sites, and widespread application of insecticides. More recently, efficient traps and screens have been developed that, usually with community participation, can keep tsetse populations at low levels in a cost-effective manner (38).
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