African Trypanosomiasis (Sleeping Sickness; Trypanosoma brucei Complex)

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Chapter 278 African Trypanosomiasis (Sleeping Sickness; Trypanosoma brucei Complex)

Over 60 million people in nearly 40 countries are at risk for infection with Trypanosoma brucei complex, the causative agent of sleeping sickness. Also known as human African trypanosomiasis (HAT), this disease is restricted to sub-Saharan Africa, the range of the tsetse fly vector, where at least 300,000 people are infected. It is a disease of extreme poverty, with an increasing burden observed in remote rural areas. HAT comes in 2 geographically and clinically distinct forms. Trypanosoma brucei gambiense causes a chronic infection lasting years and mostly affects people who live in Western and Central Africa (West African sleeping sickness, Gambian trypanosomiasis). Trypanosoma brucei rhodesiense, a zoonosis, presents as an acute illness lasting several weeks and usually occurs in residents of eastern and southern Africa (East African sleeping sickness, Rhodesian trypanosomiasis).

Epidemiology

HAT is a major public health problem in sub-Saharan Africa. It occurs in the region between latitudes 15 degrees north and 15 degrees south, corresponding roughly to the area where the annual rainfall creates optimal climatic conditions for Glossina flies to thrive.

Thirty-two thousand cases of HAT are reported annually, although an incidence of up to 70,000 cases/yr is estimated to occur; 24,000 deaths per year are attributed to HAT. By far, the bulk of reported cases are made up of T. brucei gambiense, with approximately two thirds of the cases coming from the Democratic Republic of the Congo. The incidence of HAT has been dropping in recent years, reflecting more aggressive and cohesive control programs, but these programs need to be sustained before the possibility of elimination can be considered realistic. Over 1.5 million disability-adjusted life years were lost to HAT in 2002, although this number does not take into account morbidity from acute and chronic infection, toxic side effects of treatment, or economic burden from losses of trypanosome-infected livestock.

T. brucei rhodesiense infection is restricted to the eastern third of the endemic area in tropical Africa, stretching from Ethiopia to the northern boundaries of South Africa. T. brucei gambiense occurs mainly in the western half of the continent’s endemic region. Glossina captured in endemic foci show a low rate of infection, usually <5%. Rhodesian HAT, which has an acute and often fatal course, greatly reduces chances of transmission to tsetse flies. The ability of T. brucei rhodesiense to multiply rapidly in the bloodstream and infect other species of mammals helps maintain its life cycle. The insect vector is able to transmit disease for up to 6 mo.

Clinical Manifestations

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