Figure 1.

The Leishmania life cycle. The Leishmania life cycle begins when the vertebrate host is bitten by the infected insect. Then the inoculated parasites are phagocyted by the reticuloendothelial cells, the intracellular parasites replicate, and eventually burst free from the infected macrophages, spreading the disease within the mammal host. As a new insect bites an infected vertebrate host, it swallows infected macrophages, the parasites are then released, differentiate into promastigotes, migrate into the midgut, become metacyclic (infective parasites) during the next four to seven days and migrate to the cardial valve ready to be re-inoculated into a vertebrate host.