|L. donovanii in bone marrow cell|
It is spread by sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World.
Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents, and humans. Leishmania currently affects 12 million people in 98 countries. The parasite was named in 1903 after the Scottish pathologist William Boog Leishman.
The parasite causes three kinds of disease. Each type of disease is caused by different species of the parasite.
- Skin disease: the Oriental sore
- Mucous membrane leishmaniasis: can be fatal
- Visceral disease of the liver and spleen, and anaemia. So-called kala-azar
Leishmania possess a lipophosphoglycan coat over the outside of the Leishmania cell. Lipophosphoglycan is a trigger for Toll-like receptor 2, a signalling receptor involved in triggering an innate immune response in mammals. The parasite is able to withstand the counter-attack by the immune system. There are treatments, which consist in helping the immune system to respond.