TRYPANOSOMA-CRUZI IN THE OPOSSUM DIDELPHIS-MARSUPIALIS - A STUDY OF THE CORRELATIONS AND KINETICS OF THE SYSTEMIC AND SCENT GLAND INFECTIONS IN NATURALLY AND EXPERIMENTALLY INFECTED ANIMALS

The genus Didelphis (Marsupialia, Didelphidae) has the unique capacity of supporting both multiplication cycles of Trypanosoma cruzi simulta neously; besides the intracellular forms, the epimastigotes can be fou nd multiplying and differentiating abundantly in the lumen of the scen t glands. The biological significance of the life cycle of T. cruzi wi thin the scent glands of Didelphis marsupialis, as well as its contrib ution to the epidemiology of the disease, is presently unclear. In ord er to clarify the mechanisms involved in the colonization of this sing ular habitat by T. cruzi, as well as to understand its biological role , we have carried out a serological and parasitological follow-up of b oth natural and experimental infections of young and adult opossums. A lthough all natural infections were stable and long lasting, no infect ed scent glands were found, indicating that the stability of the syste mic infections does not depend on the presence of flagellates in the s cent gland. In 84% of the experimentally infected animals the coloniza tion of the scent glands was preceded by a period of patent parasitemi a. Parasitism of the scent glands was essentially permanent and bilate ral, and its maintenance was independent of circulating parasites. Mor eover, the course of the infection differed depending on the source (s cent glands versus axenic culture-derived) of the metacyclic forms. Ou r results suggest that parasitism of the SG of D. marsupialis is most likely a secondary acquisition, a step toward independence from the in sect vector, similarly to what is accepted for Trypanosoma equiperdum. (C) 1997 Academic Press.