Plasmodium

Genus of parasitic protozoa that cause malaria. The life-cycle is complex, involving several changes in cellular morphology and behaviour. Intermediate host is female mosquito (Anopheles) that infects vertebrate host when taking a blood meal. Predominant form of the organism in humans is the intracellular parasite (the merozoite) in the erythrocyte, where it undergoes a form of multiple cell division termed schizogony. As a result the erythrocyte bursts and the progeny infect other erythrocytes. Eventually some cells develop into gametes that, when ingested by a female mosquito, will fuse in her gut to form a zygote (ookinete). Multiple cell division within the resultant oocyte, attached to the gut wall, gives rise to infective sporozoites; these migrate to the salivary glands and are ejected with the saliva the next time the mosquito takes a blood-meal.