Induction and detection of leishmanial infections in Rattus norvegicus.

Weanling Sprague-Dawley rats were injected intradermally with Leishmania major or with L. donovani promastigotes. Parasites could be cultivated from the skin at times from 2 to 28 days after infection. At necropsy, no parasites were observed in spleen or liver impression smears, nor could they be cultivated from heart blood or spleen, even when skin cultures were positive. Rats were not highly susceptible to infection with L. donovani, since parasites could be cultured from skin only at 2 days after infection. L. major could establish an infection in rat skin, elicit antibodies, and in some cases, metastasize from the inoculation site. At necropsy, anti-leishmanial antibodies were detected in rats with parasites in their skin, although cutaneous lesions were not observed. These findings suggest that commonly used survey techniques are relatively insensitive, and might indicate possible involvement of Rattus norvegicus in the transmission cycle of cutaneous leishmaniasis.