African trypanosomiasis epidemiology and demographics


 * Pilar Almonacid

Epidemiology and Demographics
The disease is found in two forms, depending on the parasite, either Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense. T. b. gambiense is found in central and western Africa; it causes a chronic condition that can extend in a passive phase for months or years before symptoms emerge. T. b. rhodesiense, is the acute form of the disease but has a much more limited range. It is found in southern and eastern Africa; its infection emerges in a few weeks and is more virulent and faster developing. According to recent estimates, the disability adjusted life years (9 to 10 years) (DALYs) lost due to sleeping sickness are 2.0 million. Recent estimates indicate that over 60 million people living in some 250 foci are at risk of contracting the disease, and there are about 300,000 new cases each year. The disease has been recorded as occurring in 36 countries, all in sub-Saharan Africa.

Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in pigs and other animals. Wild game animals and cattle are the main reservoir of T. b. rhodesiense.

Horse-flies (Tabanidae) and Stomoxydinae possibly could play a role by mechanical transmission (in special situations) not only of Nagana (the animal form of sleeping sickness) but also of the human disease form.

East african trypanosomiasis
Worldwide, approximately 25,000 new cases of both East and West African trypanosomiasis are reported to the World Health Organization each year. However, many cases are not reported due to a lack of infrastructure and the true number of new cases is undoubtedly much higher. Since 1967, thirty-six cases of East African trypanosomiasis have been reported within the United States, all among individuals who had traveled to Africa.

East African trypanosomiasis is found in parts of Eastern and Central Africa, including Uganda, Kenya, Tanzania, Malawi, Ethiopia, Zaire, Zimbabwe, and Botswana. Areas where infection is spread are largely determined by the location of the infected tsetse fly and wild animal population.

West african trypanosomiasis
Worldwide, approximately 40,000 new cases of both East and West African trypanosomiasis are reported to the World Health Organization each year. However, the majority of cases are not reported due to a lack of infrastructure and it is likely that there are more than 100,000 new cases annually. Few cases of West African trypanosomiasis have been reported in the United States.

West African trypanosomiasis can be contracted in parts of Western and Central Africa. The tsetse fly lives only in Africa; areas where infection is spread are largely determined by where the infected tsetse fly is found.