BEHAVIOR IN A MOUSE MODEL OF ISOLATES OF LEISHMANIA-DONOVANI SENSU-LATO CULTURED FROM THE BLOOD OF PATIENTS WITH CHRONIC CUTANEOUS LESIONS

Our objective was to characterize biologically in an animal model two isolates of Leishmania parasites unexpectedly encountered in the circu lating blood of two patients with chronic cutaneous leishmaniasis. Bot h isolates were classified by cellulose acetate electrophoresis as bel onging to the L. donovani sense late complex. We elected to use BALB/c mice, an inbred strain that has been proven to be very sensitive to t he dermotropic parasite L, major. This study demonstrated that for the same number of parasites, the course of infection with the L. donovan i strain was different from that developed in similar animals that rec eived the L. major strain. After a protracted incubation period, L. do novani produced scanty cutaneous lesions and mainly a systemic disease . This is in contrast to the rapidly spreading skin lesion that kills L. major-infected animals within a few months. It is concluded that BA LB/c mice are an adequate animal model for the L. donovani strain, whi ch had an unusual clinical presentation in humans. The prolonged incub ation period, such as observed here, may lead to erroneous conclusions of host resistance if the experiment were terminated based on L. majo r activity in the same model. Finally, the unusual behavior in humans and mice of certain strains (such as the one encountered in these pati ents) must reflect peculiar intrinsic features of the parasite, which are best understood using animal models in the laboratory.