Leishmania

These are intracellular parasites of tissue macrophages of mammals. Their location in the vertebrate host varies among species of this parasite, but the general details of the life cycle are similar. The amastigote stage is found within the mammalian macrophage. It divides by fission. Infected macrophages rupture and release amastigotes, which infect other macrophages in the vicinity. If infected macrophages are taken up by a feeding sandfly, they transform into promastigotes and multiply by fission in the gut of the sandfly. The promastigotes migrate to the pharynx and can be inoculated when the fly feeds on another host. The promastigotes infect macrophages near the site of infection and become amastigotes. In L. major and L. tropica the infections tend to remain in subcutaneous tissues, but in L. donovani the infection spreads to macrophages in internal organs.