leishmaniasis, 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. Treatment is with amphotericin B and other drugs. Leishmaniasis is rarely seen in the United States, but is prevalent in South Asia, the Middle East, North Africa, and parts of the Mediterranean.

Human protozoal infection spread by the bite of a bloodsucking sand fly. It occurs worldwide but is especially prevalent in tropical areas. It is caused by various species of the flagellate protozoan Leishmania, which infect rodents and canines. Visceral leishmaniasis, or kala-azar, occurs throughout the world but is especially prevalent in the Mediterranean area, Africa, Asia, and Latin America; it affects the liver, spleen, and bone marrow and is usually fatal if not treated. Cutaneous leishmaniasis is endemic in areas around the Mediterranean, in central and northern Africa, and in southern and western Asia; it is also found in Central and South America and parts of the southern U.S. It is characterized by lesions on the skin of the legs, feet, hands, and face, most of which heal spontaneously after many months.

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