"Trypanosoma cruzi" : comparative studies of infectivity of parasites ingested by "Triatoma infestans" and those present in their feces

Artificial feeding of the insects with whole blood containing trypomastigotes resulted in triatome infection; the parasites were present in the host feces after 15--30 days and, when inoculated into mice, elicited parasitemia in 100% of the cases and deaths in 20--70%. This mortality indicates a reduction of the original infective capacity of the bloodstream form, which kills 100% of the mice even when inoculated with a single trypomastigote. When triatomes were fed whole normal mouse blood containing culture forms of low infective capacity (TulL), mice inoculated with feces containing the progeny of the culture forms failed to develop a parasitemia. The absence of any infective capacity of these parasites was proven when the mice challenged with lethal doses of trypomastigotes 30 days after the fecal inoculations died at the same time as the controls. Mice injected with feces from triatomes fed culture forms with high infectivity for mice (TulB) developed patent parasitemia, indicating that triatomes may be infected by parasite forms other than bloodstream trypomastigotes. Experiments on infectivity of parasites present in the feces of triatomes fed TulL and TulB culture forms, also showed a single passage through the digestive tract of the insects did not significantly modify the infective capacity of the parasite population. When stomachs and intestines from insects fed TulB were processed separately, parasites obtained from the latter showed higher infectivity for mice than those obtained from the former.