Phylum – Protozoa
Class – Mastigophora
Order – Protomonadina
Genus – Leishmania
Species — donovani
Leishmania is a genus of trypanosomes that are responsible for the disease leishmaniasis.Leishmania donovani is a species of intracellular parasites belonging to the genus Leishmania, a group of haemoflagellate kinetoplastids that cause the disease leishmaniasis Leishmania donovani is a protozoan endoparasite inhabiting the cells of reticulo-endothelial system of human beings causing kala-azar or visceral leishmaniasis. It infects the mononuclear phagocyte system including spleen, liver and bone marrow. Infection is transmitted by species of sandfly belonging to the genus Phlebotomus in Old World and Lutzomyia in New World.Therefore, the parasite is prevalent throughout tropical and temperate regions including Africa (mostly in Sudan), China, India, Nepal, southern Europe, Russiaand South America. It is named after the discoverer, Leishman and Donovan. Leishman in May, 1903 from London and Donovan in July, 1903 from Madras, independently discovered the parasite in the spleen of the patients suffering from kala- azar.
- The amastigote form is found in the mononuclear phagocytes and circulatory systems of humans. It is an intracellular and nonmotile form, being devoid of external flagella. The short flagellum is embedded at the anterior end without projecting out. It is oval in shape, and measures 3–6 µm in length and 1–3 µm in breadth. The kinetoplast and basal body lie towards the anterior end.
The promastigote form is found in the alimentary tract of sandflies. It is an extracellular and motile form. It is considerably larger and highly elongated, measuring 15-30 µm in length and 5 µm in width. It is spindle-shaped, tapering at both ends. A long flagellum (about the body length) is projected externally at the anterior end. The nucleus lies at the centre, and in front of it are the kinetoplast and the basal body.