Fatal without treatment.
Infection by extracellular protozoan parasites, transmitted through the bite of an infected tsetse fly ( Glossina ).
Two forms of the disease exist, caused by 2 different subspecies of Trypanosoma brucei : T b gambiense occurs in central and west Africa and causes the chronic disease form; T b rhodesiense occurs in east and southern Africa and causes the acute form.
Two disease stages can be distinguished: the first or early stage (haemolymphatic), in which parasites are located in the blood, lymph, and peripheral organs; and the second, late, or advanced stage (meningoencephalitic), in which parasites have crossed the blood-brain barrier and invaded the central nervous system. Signs and symptoms vary according to the disease stage.
In T b gambiense -endemic regions, the card agglutination test for trypanosomiasis is used for population screening. Rapid serodiagnostic tests are suited for individual screening in order to detect the presence of antibodies.
Definite diagnosis is based on microscopic evidence of the trypanosome in body fluids. Disease staging is based on CSF examination.
Treatment depends on parasite subspecies and disease stage, but all drugs can have severe side effects and are complex to use.
Human African trypanosomiasis (HAT), or sleeping sickness, is a fatal disease caused by extracellular parasites (genus Trypanosoma ), which are transmitted by tsetse flies (genus Glossina ).
Two morphologically indistinguishable Trypanosoma brucei subspecies cause disease in humans. In west and central sub-Saharan Africa, infection with T b gambiense leads to a chronic disease that may last for years. In east and southern Africa, T b rhodesiense infection causes an acute disease that may be fatal within months. The parasite is initially found in lymph and blood (haemolymphatic stage), but after a variable period, it crosses the blood-brain barrier and invades the CNS (meningoencephalitic stage).      
Director of Research
Institut de Recherche pour le Développement
VL is an author of several references cited in this monograph. VL declares that he has no competing interests.
Control of Neglected Tropical Diseases
Human African Trypanosomiasis Control Program
World Health Organization
JRF is an author of several references cited in this monograph. JRF declares that he has no competing interests.
Former head of WHO HAT control and surveillance programme
WHO temporary advisor
World Health Organization
PPS is an author of several references cited in this monograph.
Professor of Molecular Parasitology and Medicine
Centre for Infection
Division of Cellular and Molecular Medicine
University of London
SK is a consultant for the Foundation for Innovative Diagnostics, a non-profit organization developing diagnostics for neglected diseases such as HAT. SK is an author of a reference cited in this monograph.
Division of Infection and Immunity
Institute of Biomedical and Life Sciences
The Glasgow Biomedical Research Centre
University of Glasgow
MB declares that he has no competing interests.
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