leishmaniasis (lēshˌmənĪˈəsĭs) [key], any of a group of tropical diseases caused by parasitic protozoans of the genus Leishmania. The parasites live in dogs, foxes, rodents, and humans; they are transmitted by the bites of sand flies. There they infect the very white blood cells that normally would defend the body from such invaders. There are two forms of leishmaniasis. The more serious, called kala-azar or visceral leishmaniasis, affects the internal organs, causing fever, anemia, splenomegaly, and discoloration of the skin. Untreated, it can be fatal. The second, or cutaneous form, leaves deep, disfiguring sores at the site of the bite. Research suggests that the more serious form results at least in part from a genetic susceptibility. Treatment is mainly with meglumine antimoniate, sodium stibogluconate, and other drugs that contain antimony. Leishmaniasis is rarely seen in the United States, but is prevalent in South Asia, the Middle East, much of Africa, and parts of Central and South America.