Leishmania is a protozoan that causes a disease called leishmaniasis. Leishmania species are classified into Old World species and New World species. Old World species include L. major, L. tropica, and L. aethiopica commonly found in Africa and Asia, and are known to cause cutaneous or visceral leishmaniasis.
The New World species include L. mexicana, L. venezuelensis, and L. amazonensis found in Central and South America, which are associated with cutaneous or visceral disease plus mucosal leishmaniasis. Leishmaniasis presents with varying symptoms depending on the affected organs and the culprit agent, but the common symptoms include skin sores, fever, weight loss, anemia, lymphadenopathy, and damage to the nasopharyngeal mucosae.