Do radically dissimilar Trypanosoma cruzi strains (zymodemes) cause Venezuelan and Brazilian forms of Chagas' disease?

316 isolates of Trypanosoma cruzi, the causative organism of Chagas' disease, were collected from three geographical areas: Venezuela, where Chagas' disease does not cause megacardia, megaoesophagus, and megacolon; the Brazilian Amazon basin, where T. cruzi is silvatic and human infection is rare; and central and eastern Brazil, where T. cruzi infection is commonly associated with "mega" syndromes. The distribution in these regions of three radically dissimilar enzymic strains or "zymodemes" of T. cruzi (Z1, Z2, and Z3) was compared. Endemic Chagas' disease in Venezuela ws predominantly due to T. cruzi Z1 and rarely to T. cruzi Z3. T. cruzi Z1 and Z3 also caused the sporadic cases of Chagas' disease in the Brazilian Amazon basin. A quite distinct T. cruzi zymodeme, Z2, not found in either Venezuela or the Amazon basin, was isolated from the vast majority of patients in central and eastern Brazil. These observations suggest that different aetiological agents might account for the difference between the Venezuelan and Brazilian forms of Chagas' disease.