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The malaria parasite
life cycle involves two hosts. During a blood meal, a malaria-infected
female Anopheles mosquito inoculates sporozoites into the human host
.
Sporozoites infect liver cells
and mature
into schizonts
, which
rupture and release merozoites
. (Of
note, in P. vivax and P. ovale a dormant stage [hypnozoites]
can persist in the liver and cause relapses by invading the bloodstream
weeks, or even years later.) After this initial replication in the liver (exo-erythrocytic
schizogony
), the
parasites undergo asexual multiplication in the erythrocytes (erythrocytic
schizogony
).
Merozoites infect red blood cells
. The ring
stage trophozoites mature into schizonts, which rupture releasing merozoites
. Some
parasites differentiate into sexual erythrocytic stages (gametocytes)
. Blood
stage parasites are responsible for the clinical manifestations of the
disease. The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal . The parasites’ multiplication in the mosquito is known as the sporogonic cycle . While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes . The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts . The oocysts grow, rupture, and release sporozoites , which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle .
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