Borrelia sp. in naturally infected Didelphis aurita (Wied, 1826) (Marsupialia: Didelphidae).

Fifty-six opossums (Didelphis aurita) were captured on the campus of Universidade Federal Rural do Rio de Janeiro, Seropedica county, Rio de Janeiro state, in order to investigate the occurrence of Borrelia sp among them in relation with the study of spirochaetemia and its ectoparasites. Blood tests were made through dark field and phase contrast microscopy, as well as the obtainment of blood smears. Smears were stained with Giemsa stain, which did not prove efficacy. There was no relation between results obtained through blood tests (13 opossum positive for Borreliasp.), and this technique (two positive animals). Parasitaemia studies of 37 animals kept in captivity as well as of several recaptures in which animals once negative proved to be positive days later, showed that haemoscopical studies could be used as an effective diagnosis tool. Ectoparasites from nine animals were classified; with the occurrence of nymphal Amblyomma cajennense and adult Ctenocephalides sp..