The old world L.tropica parasites produce dermal leishmaniasis, usually a self-healing lesion called "oriental sore", whereas Leishmania donovani parasites migrate to endothelial cells of the reticuloendothelial system and polymorphonuclear leukocytes of the blodd, spleen, lymph and bone marrow, and produce visceral leishmaniasis, which can be fatal if untreated.