Figure 1.

Life-cycle of L. infantum and L. donovani. Leishmaniasis transmission occurs through the bite of female phlebotomine sand flies that are carrying parasites. In the Old World, visceral leishmaniasis (VL) is anthroponotic, with L. donovani circulating among humans. However, in Europe, West Africa, and the Americas, VL is a zoonosis, primarily caused by L. infantum, which affects humans and dogs, which are considered as the main parasite reservoir. The transmission process begins when sand flies feed on blood (1) and inject the infective metacyclic form of Leishmania promastigotes (2) into the host’s dermis. Once inside the body, promastigotes are engulfed by macrophages (3) and other types of mononuclear phagocytic cells. Within these cells, promastigotes transform into amastigotes (4), the tissue stage of the parasite. Amastigotes multiply through simple division (5) and proceed to infect other mononuclear phagocytic cells, leading to the development and manifestation of the infection.