Polymorphism in trypomastigotes of Trypanosoma (Megatrypanum) minasense inthe blood of experimentally infected squirrel monkey and marmosets

Experimental infections by Trypanosoma (Megatrypanum) minasense were perfor med in primates - Saimiri sciureus and Callithrix penicillata - with the ob jective of searching for morphological variations of the blood trypomastigo tes with respect to hosts and time of infection. We carried out morphologic al and morphometric analysis of blood trypomastigotes. Illustrations are gi ven. Both the squirrel monkey and marmoset became infected after the injection o f blood trypomastigotes of T. minasense, although the parasitaemia were bri efer in the squirrel monkey. The parasites detected in the later host were narrower and shorter than hose found in th inoculated marmoset. In the marm oset, the blood stream parasites derived from culture metacyclic trypomasti gotes were considerable smaller than those derived from the inoculation inf ected blood. Stronger evidence of polymorphism was found when, at the same time of infec tion, the blood trypomastigotes found in squirrel monkey had smaller length , body width and the distance from posterior end of the body to the kinetop last almost four times smaller than the parasite found in the marmoset. The refore, conflicting results on morphology and morphometry of T. minasense o btained by previous investigators could be due to polymorphism.