[Behavior of Trypanosoma cruzi strains after passage in different triatominae species]

To study the influence of the intermediate host stage on the course of mouse infection, Trypanosoma cruzi belonging to the Peruvian (Type I), 12 SF (Type II) and Colombian (Type III) strains were passaged through either Rhodnius prolixus, Panstrongylus megistus or Triatoma infestans. T. cruzi metacyclic forms (dose 10(4)) from the different strains were obtained from each bug and inoculated into 8-10 gm mice. Comparison was made in mice inoculated with blood forms. Parasitaemia curves were plotted in the peripheral blood for each strain, reaching more elevated peaks with Peruvian strain parasites from P. megistus and R. prolixus, 12 SF strain from P. megistus and Colombian strain from R. prolixus. Tissue tropism and histopathological patterns were those usually seen in mice infected with each respective strain type. Peruvian virulence was the same for all groups. Slender forms predominate among mice inoculated with metacyclic forms of Colombian and 12 SF strains, probably an adaptative parasite change related to the intermediate host.