Life cycle
Leishmaniasis is a vector-borne disease and it is transmitted by small dipterans called sandflies. Female sandflies are hematophagous and, if infected, they inject the flagellated stage (promastigote) into the skin of the vertebrate host while feeding. Several cell types ingest the parasites in the infection site, but they will only survive inside macrophages, where they withdraw their external flagellum and become intracellular (amastigote). Intracellular amastigotes divide by binary fission until they either rupture or are released by the host cell. The released parasites are ingested by other macrophages and the infection spreads by movement of infected cells in the vascular system. Sandflies become infected when they ingest infected cells from the skin on an infected host. Inside the gut of the fly the amastigotes are released and transform back into promastigotes. Sandflies are not mechanical vectors: After a developmental period the promastigotes migrate to the hypostome of the sand fly and are inoculated into a new host when the fly feeds.