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Brief Summary

Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense are protozoan parasites that are the cause of nearly all human African trypanosomiasis (HAT, or African sleeping sickness); the subspecies Trypanosoma brucei brucei infects domestic and wild animals but usually not humans (but see the phylogeographic analysis by Balmer et al. 2011, which concludes that these three "subspecies" are not actually genetically or historically distinct lineages). These extracellular parasites are transmitted by the bite of Glossina tsetse flies. For the most part, at least, Trypanosoma brucei gambiense (which accounts for most cases of HAT) occurs in central and western Africa and Trypanosoma brucei rhodesiense occurs in eastern and southern Africa--although continued expansion of T. brucei rhodesiense to the northwest (e.g., by trade in infected cattle) may eventually result in overlapping ranges (Picozzi et al. 2005). HAT is limited to sub-Saharan Africa by the range of its tsetse fly vector. As of 2010, the best available estimates suggested a total of about 50,000 to 70,000 cases of HAT in the world. Left untreated, HAT leads to coma and death. Trypanosoma brucei gambiense infection is characterised by a chronic progressive course. The estimated average duration of infection is around 3 years, evenly divided between an initial haemolymphatic stage and a subsequent meningoencephalitic stage, during which the central nervous system is invaded. Abnormal sleep patterns are a leading symptom of the second stage (and account for the disease's colloquial name). Trypanosoma brucei rhodesiense disease is typically acute, with death occurring within weeks or months. Human African trypanosomiasis due to T. b. gambiensee is very rare in short-term tourists, but has been reported in immigrants, refugees, and expatriates resident for long periods in rural areas. Because of its long incubation time and chronic nature, the disease should be considered even if a patient’s last stay in an endemic region occurred many years ago. The number of tourists infected in countries that report the most local patients is low, probably because these countries are rarely visited by travelers. (Fevre et al. 2008; Brun et al. 2010 and references therein)


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© Shapiro, Leo

Source: EOL Rapid Response Team


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