Pathology and Mechanism of Disease in Kala-Azar and Post-kala-azar Dermal Leishmaniasis

Abstract

The transmission of Leishmania donovani in humans is carried out via the bite of the infected female sandfly of the genus Phlebotomus. Flagellated promastigotes enter the skin, are engulfed by resident macrophages, and develop into amastigotes known as Leishman-Donovan bodies. These amastigotes are ingested by the sandfly along with a blood meal; they develop into promastigote form in the midgut of the sandfly, and become infective in about 9 days. The average incubation period in humans is 3–6 months, but it may be as long as 2 years. Kala-azar manifests with fever lasting more than 2 weeks, splenomegaly, anemia, weight loss, and increased pigmentation of the skin. Post-kala-azar dermal leishmaniasis is a sequel to kala-azar that usually develops 6 months to 5 years following an attack of untreated or incompletely cured visceral leishmaniasis.