Plasmodium ovale is rare and generally occur in West Africa. Both P.malariae and P. ovale, like P. vivax, can cause relapses. .
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The life cycle of malaria parasite is fairly complex (see diagram). They require both a human and Anopheles mosquito host. Malaria parasites are picked up by the mosquito from the blood of an infected human when feeding. The parasite then undergoes sexual reproduction in the gut of the mosquito. When an infected female Anopheles mosquito feed on the blood of a human, it injects into the person's bloodstream, its saliva which contains the infectious thread-like form of the parasite, the sporozoite. The sporozoites then migrate to the liver and invade the liver cells where it reproduces asexually to form thousands of merozoites contained in a schizont. The matured and ruptured schizont releases the merozoites into the bloodstream to invade red blood cells and consume hemoglobin (blood oxygen carrier) as fuel. This is where symptoms become noticeable. On the other hand, some P. vivax and P. ovale sporozoites may remain in resting phase as hypnozoites, in the liver for months to years and cause relapses when it becomes active again. Within the red blood cell, parasites reproduce all over again to infect even more red blood cells, and infection will continue until the body's immune system begins to control them or medication come in to bring it under control. Some merozoites, instead of developing sexually into schizonts, develop to form gametocytes. These gametocytes circulate in the human host bloodstream, waiting for the next female Anopheles mosquito to pick it up. The gametocytes, once in the mosquito's gut, develop into male and female gametes, which ultimately develop into an ookinete. Fertilization occurs and sporozoites filled oocyst is produced. Upon maturing, oocyst ruptures and thousands of sporozoites migrate to the salivary glands of the mosquito ready for transfer into new human host.
