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Malaria is a vector-borne illness; the vector in this case is the female Anopheles Mosquito which carries the parasite from and to the human hosts.  Several strains of malarial parasites exist, but Plasmodium Falciparum, Plasmodium Malariae, Plasmodium Ovale, and Plasmodium Vivax are capable of infecting humans. Malaria caused by each strain differs with respect to the duration of incubation and severity of illness. While feeding on human blood, female mosquitoes secrete parasite-infected saliva into the human blood stream to prevent agglutination of blood. As malarial parasites are found in Red Blood Cells, they may also, though very rarely, be transmitted through blood transfusion, organ transplants and from mother to fetus during pregnancy or delivery (USACHPPM, 2007).

Stages of Plasmodium Development within Humans

The parasite enters the human blood in the infections form from the mosquito’s saliva. This form is called Sporozoite and invades liver cells in the human host. Sporozoites develop into Schizonts which rupture when mature to release countless structures called Merozoites into the blood stream. The time it takes the parasite to mature within the blood stream depends upon the species of Plasmodium. In the case of P. Vivax and P. Ovale Sporozoites convert into Hypnozoites, a dormant form that remains in the liver for months or years with the possibility of becoming active and causing a relapse of Malaria in the host. Once released into the blood stream, Merozoites invade RBCs and feed on hemoglobin and undergo a round of asexual reproduction forming Merozoite-filled Schizonts which repeat same cycle of maturation and rupture or RBCs as in the liver cells; this causes the infection to build up within the host (U.S. Department of Health and Human Services, 2007).

Some Merozoites within the RBCs do not develop asexually, but instead convert into Gametocytes (male and female sexual forms of the parasite) which circulate in the blood stream and are picked up by a female anopheles mosquito which feeds on the infected hosts’ blood.

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