Didelphis marsupialis, an important reservoir of Trypanosoma (Schizotrypanum) cruzi and Leishmania (Leishmania) chagasi in Colombia.

The role of Didelphis marsupialis as a reservoir of zoonotic hemoflagellates was examined in two ecologically distinct settings in Colombia. While 72% (12 of 18) of the opossums collected in the tropical rain forest harbored Trypanosoma cruzi, other mammals in the area had lower infection rates: 1.3% (Proechymis semispinosus [spiny rat]; 13% Tylomys mirae [climbing rat]; and 6% Rattus rattus). Trypanosoma cruzi isolates from D. marsupialis were similar to zymodeme 1 (Z1), and two of four phenotypes were shared with Tylomys mirae, which is also predominantly arboreal. Terrestrial (P. semispinosus) and peridomestic (R. rattus) animals were infected with Z3 or other Z1 phenotypes, respectively. Schizodeme analysis showed polymorphisms among isolates from mammals, reflecting diverse modes of transmission, and a complex epidemiologic situation. Despite the lower infection rate of the opossum (14%) found in our study in the tropical dry forest as compared with the tropical wet forest, Chagas' disease has been reported only in the former area. This suggests that the lack of alternative blood sources for triatomines of the tropical dry forest, where mammals are less abundant than in the wet forest, may increase the risk of human infection. Among several species of mammals captured in the tropical dry forest, Leishmania chagasi was isolated from 22.7% (5 of 22) D. marsupialis. This finding confirms the important role of opossums in Colombian foci of visceral leishmaniasis, including those where the phlebotomine species involved in transmission is Lutzomyia evansi, an alternative vector to the more common Lutzomyia longipalpis.