Health topics

Human African trypanosomiasis

 

Human African trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease caused by infection with protozoan parasites belonging to the genus Trypanosoma. The parasites are transmitted to humans through the bite of tsetse flies (Glossina genus), which have acquired their infection from humans or from animals harbouring the human pathogenic parasites.

Human African trypanosomiasis occurs only in 36 sub-Sahalan African countries where there are tsetse flies that transmit the disease. The disease takes two forms, depending on the parasite involved.

Trypanosoma brucei gambiense is found in 24 countries in western and central Africa. This form currently accounts for over 98% of reported cases of sleeping sickness and causes a chronic infection. A person can be infected for months or even years without major signs or symptoms of the disease. When more evident symptoms emerge, the patient is often already in an advanced disease stage where the central nervous system is affected.

Trypanosoma brucei rhodesiense is found in 13 countries in eastern and southern Africa. Nowadays, this form represents fewer than 2% of reported cases and causes an acute infection. First signs and symptoms are observed a few months or weeks after infection. The disease develops rapidly and invades the central nervous system. Only Uganda presents both forms of the disease, but in separate zones.

Another form of trypanosomiasis occurs mainly in Latin America. It is known as American trypanosomiasis or Chagas disease. The causal organism belongs to a different Trypanosoma subgenus and is transmitted by a different vector.

Disease management is composed of four steps: (1) screening for potential infection (serological tests or clinical examination); (2) diagnosis by establishing whether the parasite is present in body fluids; (3) staging the state of disease progression (by examination of the cerebrospinal fluid obtained by lumbar puncture); and (4) treatment. Only four drugs are registered for the treatment of human African trypanosomiasis and none of them are anodyne as all have a certain level of toxicity.

Human African trypanosomiasis is not endemic in the Western Pacific Region. However, a case of infection in an individual who travelled back from an endemic country has been reported in China. Also, atypical human trypanosomiasis of zoonotic origin has been recently reported in Viet Nam.