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PROTOZOAL INFECTIONS

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AFRICAN TRYPANOSOMIASIS (SLEEPING SICKNESS)

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ESSENTIALS OF DIAGNOSIS

  • Exposure to tsetse flies; chancre at bite site uncommon.

  • Hemolymphatic disease: Irregular fever, headache, joint pain, rash, edema, lymphadenopathy.

  • Meningoencephalitic disease: Somnolence, severe headache, progressing to coma.

  • Trypanosomes in blood or lymph node aspirates; positive serologic tests.

  • Trypanosomes and increased white cells and protein in cerebrospinal fluid.

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General Considerations
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African trypanosomiasis is caused by the hemoflagellates Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense. The organisms are transmitted by bites of tsetse flies (genus Glossina), which inhabit shaded areas along streams and rivers. Trypanosomes ingested in a blood meal develop over 18–35 days in the fly; when the fly feeds again on a mammalian host, the infective stage is injected. Human disease occurs in rural areas of sub-Saharan Africa from south of the Sahara to about 30 degrees south latitude. T b gambiense causes West African trypanosomiasis, and is transmitted in the moist sub-Saharan savannas and forests of west and central Africa. T b rhodesiense causes East African trypanosomiasis, and is transmitted in the savannas of east and southeast Africa.

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T b rhodesiense infection is primarily a zoonosis of game animals and cattle; humans are infected sporadically. Humans are the principal mammalian host for T b gambiense, but domestic animals can be infected (eFigure 35–1). The number of reported cases increased from the 1960s to the 1990s and has since decreased by about 80%. Total incidence has been estimated at about 20,000 cases per year, most of which are due to T b gambiense, and the largest number in the Democratic Republic of the Congo. Infections are rare among travelers, including visitors to game parks.

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eFigure 35–1.

Life cycle of Trypanosoma brucei gambiense. The agent of chronic (West African) sleeping sickness has no clearly identified alternative or reservoir final hosts other than humans—thus, the disease appears to be chiefly an anthroponosis. The human final host provides infective blood to the tsetse vector, chiefly Glossina palpalis and other riverine species. The trypomastigotes in human blood (1), ingested by the tsetse, change from trypomastigotes (chiefly as "stumpy forms") (2) to epimastigotes, which move to the salivary glands, multiply (3), and change to infective metacyclic trypomastigotes (4), the infective stage to the human host. (Reproduced, with permission, from Goldsmith R, Heyneman D [editors]. Tropical Medicine and Parasitology. Originally published by Appleton & Lange. Copyright © 1989 by The McGraw-Hill Companies, Inc.)

Graphic Jump Location
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Clinical Findings
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A. Symptoms and Signs
++ 1. West African trypanosomiasis
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Chancres at the site of the bite are uncommon. After an asymptomatic period that may last for months, hemolymphatic disease presents with fever, headache, myalgias, arthralgias, weight loss, and lymphadenopathy, with discrete, nontender, rubbery nodes, ...

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