![]() ![]() Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites. During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host. The malaria parasite life cycle involves two hosts. Thus the infected mosquito carries the disease from one human to another (acting as a “vector”), while infected humans transmit the parasite to the mosquito, In contrast to the human host, the mosquito vector does not suffer from the presence of the parasites. When the Anopheles mosquito takes a blood meal on another human, anticoagulant saliva is injected together with the sporozoites, which migrate to the liver, thereby beginning a new cycle. After 10-18 days, a form of the parasite called a sporozoite migrates to the mosquito’s salivary glands. When certain forms of blood stage parasites (gametocytes, which occur in male and female forms) are ingested during blood feeding by a female Anopheles mosquito, they mate in the gut of the mosquito and begin a cycle of growth and multiplication in the mosquito. The blood stage parasites are those that cause the symptoms of malaria. In the blood, successive broods of parasites grow inside the red cells and destroy them, releasing daughter parasites (“merozoites”) that continue the cycle by invading other red cells. In humans, the parasites grow and multiply first in the liver cells and then in the red cells of the blood. The natural history of malaria involves cyclical infection of humans and female Anopheles mosquitoes. ![]()
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