Trypanosoma rangeli is a protozoan hemoflagellate able to infect insects of the subfamily Triatominae (Hemiptera: Reduviidae), mammals, and humans in the American continent. Although the human infection by T. rangeli is non-pathogenic, the importance of the study of this parasite resides in the fact that it shares the same vectors and mammal reservoirs with T. cruzi, the pathogenic parasite causative of Chagas disease. This situation commonly results in misdiagnosis of Chagas disease in patients living in areas where the two parasites overlap spatially and temporarily.
The occurrence of T. rangeli in Ecuador had not been documented prior to this study and only sporadic reports of T. rangeli-like organisms had been published. This study was divided in two sections: the objective of the first was to establish the presence of T. rangeli in Ecuador and to carry out an investigation of the relationship of the parasite with its Triatominae vectors and mammal hosts in two regions of the country. Rhodnius ecuadoriensis, Panstrongylus howardi, and Triatoma carrioni were found naturally infected with T. rangeli. Mixed infections with T. rangeli and T. cruzi were also observed in those vectors. Analysis of host preferences for blood meal revealed that the triatomines analyzed had fed on several species of mammals (common rat, mice, dog, cat, goat, guinea pig, human) and an avian species (chicken). The identification of the blood meal sources can contribute to the understanding of the epidemiology of T. cruzi and T. rangeli transmission cycles.
The objective of the second part of the study was to investigate the mechanism that T. rangeli uses to invade mammalian cells. Immunofluorescence assays were used for this purpose. The Choachi strain of T. rangeli and BALB/c fibroblasts were chosen to evaluate the cell invasion process. T. rangeli invades cells primarily by a lysosome-dependent fashion similar to that of T. cruzi, although T. rangeli seems to lack the alternative lysosome-independent pathway that has been described for T. cruzi. Cells infected with T. rangeli did not show signs of intracellular division up to 288 hours post-infection and parasitemia in BALB/c mice was transient and declined rapidly overtime.