The two known types of human trypanosomiasis, endemic in two regions of the world, are sleeping sickness in Africa, caused by the parasites Trypanosoma brucei gambiense or T. b. rhodiense, and Chagas' disease in South America induced by T. cruzi. Everywhere else, normally only animals are infected by trypanosomes that, although specific for humans are not pathogenic for them. Yet, in 2004, the first case of human trypanosomiasis was formally identified in India by IRD researcher Philippe Truc, working with the WHO and the Maharashtra State Department of Health (1). The patient was a farmer living in this State who proved to be infected by a trypanosome, T. evansi, usually a parasite of camels and cattle. In South America, North Africa and in a great part of Asia including India, where this parasite is present, many human populations are currently living in contact with infected animals. Scientists from the Universit Libre de Bruxelles , in conjunction with Philippe Truc and Indian medical specialists, under an agreement with WHO (2), carried out analyses on blood serum from the infected patient, which led them to identify the cause of this first case of human trypanosomiasis in India.
Humans possess natural resistance to this parasite, as they have towards related African trypanosomes, like T. brucei. In the latter case, the innate immunity results from the trypanolytic activity of a specific human protein, apolipoprotein L-1 (APOL-1). Once absorbed inside the parasite, this protein forms pores in the parasite's organelle membrane, thus inducing the destruction of the trypanosome. However, the two subspecies T. brucei rhodesiense and T. b. gambiense have, with time, overcome human immune defences by acquiring resistance to APOL-1 and thereby causing sleeping sickness in Africa. In T. b. rhodesiense, this resistance mechanism involves a protein that is peculiar to this subspecies, named SRA (Serum Resistance-associated protein), which interacts strongl
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Contact: Marie Guillaume-Signoret
fichesactu@paris.ird.fr
33-014-803-7607
Institut de Recherche Pour le Dveloppement
19-Jan-2007