Thrombocytopenia: a uniform complication of African trypanosomiasis.

Because an increasing number of reports have indicated that thrombocytopenia may occur during the course of African trypanosomiasis, a comprehensive study was designed to analyse the variables influencing the incidence and severity of this complication. Thrombocytopenia occurred in all of 40 infected domestic livestock and wildlife that were studied. The magnitude of the platelet reduction was independent of the route of inoculation (intravenous or transmission by tsetse), the genus or breed of livestock, and the species or variable antigen type (VAT) of trypanosome (several VATs of Trypanosoma (Trypanozoon) rhodesiense, T. (T.) brucei, T. (Nannomonas) congolonse, and T. (Duttonella) vivax. All 51 rats studied also became severely thrombocytopenic at the peak of parasitaemia with each of these 4 species and T. (T.) gambiense. The only variable that caused a statistically significant difference in the severity of thrombocytopenia was the height of parasitaemia, which was directly related to the reduction in the number of platelets. Rat platelets were more resistant than those of livestock to a given number of trypanosomes per ml of blood but became equally depressed during the course of the infection because the peak parasitaemia of rats was much higher. The data indicate that thrombocytopenia is a universal complication of African trypanosomiasis and underscore the potential importance of platelet damage in the pathogenesis of the coagulopathies, hemorrhage, vasoconstriction, and tissue damage that complicate this disease.