Trypanosoma species

Abstract

Trypanosomiasis describes a group of conditions caused by flagellated protozoan parasites of the genus Trypanosoma. African trypanosomiasis is caused by two subspecies of the T.brucei complex, T.brucei gambiense (West African), and T.brucei rhodesiense (East African). Organisms are transmitted from a range of wild and domestic animals and other human cases by flies of the genus Glossina (tsetse), whose geographical distribution determines the epidemiology of the infection. Ingested ‘short form’ trypomastigotes undergo change to procyclic forms which undergo division and migrate to the salivary glands and become epimastigotes. Ultimately after further cycles of division and multiplication, these yield infective non-dividing metacyclic forms. Following inoculation by fly bite, local multiplication occurs. Multiplying trypomastigotes invade the bloodstream, often weeks after initial infection, and produce fever, general malaise, myalgias, headache, generalised lymphadenopathy, splenomegaly and hepatomegaly. Fever is episodic in nature at this time, with the level of parasitaemia fluctuating in response to variation in parasite surface antigens circumventing the humoral immune response. Ultimately meningoencephalitis supervenes with persistent headache, disturbance of sleep pattern, ataxia, abnormal behaviour and decreased consciousness which progresses to coma and death.