LEISHDRUG Consortium

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Transmitted by the bite of an infected female phlebotomine sandfly, the leishmaniases are globally widespread diseases. Sandflies are primarily infected by animal reservoir hosts such as dogs and rodents (zoonotic infectious cycle), but humans are also a reservoir for some forms (autochtonous infectious cycle). The life-cycle starts when a parasitized female sandfly takes a blood meal from a human host. As the sandfly feeds, highly infectious, flagellate metacyclic promastigote forms of the leishmanial parasite enter the human host via the proboscis. Within the human host, this metacyclic form are ingested by phagocytic cells of the endo-reticular system, including macrophages, where they differentiate into aflagellate amastigote forms and reproduce by binary fission. They increase in number until the cell eventually bursts, then infect other phagocyctic cells and continue the cycle. Leishmaniasis presents itself in human in two main forms with a broad range of devastating clinical manifestations. Cutaneous forms of leishmaniasis (CL) are most common. The lesions remain localized in the skin and skin ulcers develop. CL can produce many skin ulcers on exposed skin causing serious disability and permanent scarring when they heal. Widespread parasite infection in the lymphatics causes another form of the disease, visceral leishmaniasis (VL). VL is characterized by irregular bouts of fever, substantial weight loss, swelling of the spleen and liver, and anaemia. VL is the most severe form of the disease which, if untreated, has a mortality rate of almost 100%. The infected host is bitten by another female sandfly. Parasites are picked up by the fly during the blood meal. The parasites are transformed inside the fly and delivered to a new host, and the life-cycle continues. (adapted from http://www.who.int/tdr/diseases/leish/lifecycle.htm)