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Life cycle

Infected sandfly inoculates the promastigote (flagellated form) into the skin during blood meal. The promastigote enters into the macrophages where it converts to amastigote form (non-flagellated). The multiplication of the amastigotes leads to bursting of the host cells and spread of the infection to other cells. When another sandfly bites the infected person, the infected cells will be ingested. The amastigotes transform into promastigotes and attach to the microvilli of the insect intestine. They produce chitinase that degrades the chitin coating between the esophagus and the stomach and weaken the valve (stomodeum valve). As a result there will be backflows of parasites into the mouth parts and accumulate in 7-10 days in the insect’s proboscis. The insect will be infectious after 7-10 days of infected blood meal and has to survive that long to infect the next person. 


Van Griensven, Diro E, Visceral leishmaniasis. Infect Dis Clin N AM 26 (2012) 309-322


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