Leishmaniasis refers to a group of disorders caused by members of the genus Leishmania. The manifestations may be visceral, mucocutaneous or cutaneous depending on the species of Leishmania and the immune status of the host. The life cycle and transmission vary depending on the species. All species of Leishmania pass through two stages. The amastigote stage is a rounded form (Leishman-Donovan Body) found in the vacuoles of reticuloendothelial cells. The promastigote stage is a flagellate form found in the gut of the infected insects.
Transmission is by the bite of sandflies of the genus Phlebotomus or genus Lutzomyia. In most areas leishmaniasis is a zoonosis with reservoir hosts that vary with the geographical region but include gerbils and other rodents, domestic and wild dogs, cats, opposums and other marsupials.
The parasite is not easily recovered from blood and is also difficult to observe in the bone marrow. Therefore serology can play an important role in supporting the diagnosis especially in the visceral form. The indirect immunofluorescence assay becomes positive in as little as two weeks after infection while other less sensitive techniques such as complement fixation usually take at least six weeks to show seroconversion. All species crossreact to a large degree and any Leishmania species can be used as an antigen.