Infection with different species of Leishmania causes distinct forms of leishmaniasis. For example, VL is caused by infection with either L. infantum or L. donovani; whereas CL is caused by infection with any one of several different Leishmania spp. Sandflies are the vectors that transmit the disease-causing protozoan parasites, injecting infective promastigotes when they take a blood meal. The parasites invade mammalian macrophages by receptor-mediated endocytosis, where they transform into amastigotes that multiply by binary fission. Sandflies become infected by ingesting infected cells when they take a meal of parasite-containing blood from an infected human or animal. The amastigotes transform into promastigotes and develop in the gut into metacyclic promastigotes that are infective to humans. Figure modified with permission from Alexander J. da Silva and Melanie Moser, Centers for Disease Control Public Health Image Library.