Key facts
Human African trypanosomiasis (HAT) is caused by protozoan parasites transmitted by infected tsetse flies. It is endemic in sub-Saharan Africa. Without treatment, HAT is generally fatal.
Most exposed people live in rural areas and depend on agriculture, fishing, animal husbandry or hunting.
HAT takes 2 forms, depending on the subspecies of the infecting parasite: Trypanosoma brucei gambiense (92% of reported cases) and Trypanosoma brucei rhodesiense (8%).
Sustained control efforts have reduced the number of new cases by 97% in the last 20 years.
Diagnosis and treatment are complex and require specific skills.
Overview
Human African trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease. It is caused by protozoans of the genus Trypanosoma, transmitted to humans by bites of tsetse flies (glossina) which have acquired the parasites from infected humans or animals.
Tsetse flies inhabit sub-Saharan Africa and only certain species transmit the disease. Rural populations which depend on agriculture, fishing, animal husbandry or hunting are the most exposed. In many regions where tsetse flies are found, HAT is not. The disease has a focal distribution ranging from single villages to entire regions, and the incidence can vary from one village to the next.
Forms of human African trypanosomiasis
HAT takes 2 forms, depending on the parasite subspecies:
Trypanosoma brucei gambiense, found in 24 countries of west and central Africa, currently accounts for 92% of reported cases and causes a chronic illness. A person can be infected for months or even years without major signs or symptoms. When evident symptoms emerge, often the disease is advanced with the central nervous system already affected.
Trypanosoma brucei rhodesiense, found in 13 countries of eastern and southern Africa accounts for 8% of reported cases and causes an acute disease. First signs and symptoms emerge a few weeks or months after infection. The disease develops rapidly with multi-organ invasion, including the brain.
American trypanosomiasis, or Chagas disease, occurs mainly in Latin America. It is caused by a different Trypanosoma subgenus, transmitted by another vector and the disease characteristics are very different from HAT.
Animal trypanosomiasis
Other trypanosomes cause disease in wild and domestic animals. In African cattle, it is called Nagana. Trypanosomiasis in domestic animals is a major obstacle to rural economic development.
Domestic and wild animals are the main reservoir of human-pathogenic T. b. rhodesiense. Animals can also be infected with T. b. gambiense and possibly act as a reservoir to a lesser extent not precisely known.
Disease burden and distribution
HAT threatens mainly populations of remote rural areas with limited health services, which complicates its diagnosis and treatment. These populations are also affected by war, displacement and poverty, factors favoring transmission.
Several epidemics occurred over the la
