Experimental visceral leishmaniasis in the opossum.

Adult wild-trapped opossums were infected with Leishmania donovani (Khartoum strain, WR 378) and evaluated as an animal model of visceral leishmaniasis. All infected opossums died within 32 days. Loss of body fat, hepatomegaly, and petechiae of skin and abdominal musculature were seen at necropsy. Microscopically, numerous amastigote-laden macrophages were seen in histologic sections of liver, spleen, and lymph nodes; fewer parasite-laden macrophages were in the bronchial-associated lymphoid tissues and renal glomeruli. Hematological findings included thrombocytopenia (terminal), neutropenia, and lymphopenia. Blood lymphocyte blastogenesis in response to concanavalin A and phytohemagglutinin was decreased markedly at day 24 post-infection (PI). Serum antibodies (1:40 dilution) to promastigotes of L. donovani were detected in five of eight infected opossums tested on days 10 and 24 PI. Total bilirubin concentrations and alanine aminotransferase and aspartate aminotransferase activities were increased after day 25 PI. Activated partial thromboplastin times and one-stage prothrombin times were prolonged before death. Concurrently, factors V, VIII, and XII activities were decreased.