Leishmania tropica experimental infection in the rat using luciferase-transfected parasites

Leishmania tropica is the causative agent of zoonotic cutaneous leishmaniasis in different parts of the Old World. Although it is a common cause of disease in some areas of the world, there is insufficient knowledge on the pathogenicity of this parasite in mammalian hosts and animal models. L. tropica luciferase-transfected metacyclic-stage promastigotes were inoculated into the footpad or ear of Sprague Dawley (SD) rats. Parasite DNA was detected by kDNA real time PCR in the blood at varying levels from 2 days to 5 weeks post infection (PI) in the absence of clinical signs. Parasite DNA was found in the spleen of all rats at the end of the study, and the parasitic load was up to 40 times higher in the spleen when compared with inoculation sites. Parasites were cultured from the spleen, and skin inoculation sites 5 weeks PI. Bioluminescent parasites were observed by in vivo imaging at one day PI, but the technique was not sufficiently sensitive to follow parasite spread after this time. This study provides new evidence for the viscerotropic spread of L. tropica in the rat and demonstrates that the rat can serve as a model for persistent visceralizing infection with this parasite.