Life cycle of plasmodium parasites causing malaria in humansThe malaria parasite life cycle involves two hosts. During a blood meal, a plasmodium-infected female Anopheles mosquito inoculates
sporozoites into the human host (1).
Sporozoites infect liver cells (2) and mature into
schizonts (3), which rupture and release
merozoites (4). (Note that in P. vivax and P. ovale, a dormant stage [hypnozoite] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years, later.) After this initial replication in the liver, a process known as exo-erythrocytic
schizogony (A), the parasites undergo asexual multiplication in the erythrocytes (red blood cells), a process known as erythrocytic
schizogony (B).
Merozoites infect red blood cells (5). The ring stage
trophozoites mature into
schizonts, which rupture and release
merozoites (6). Some parasites differentiate into sexual erythrocytic stages (
gametocytes) (7). Blood stage parasites are responsible for the clinical manifestations of the disease. The
gametocytes, both male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal (8). The parasites’ multiplication in the mosquito is known as the sporogonic cycle (C). While in the mosquito's stomach, the
haploid microgametes penetrate the
haploid macrogametes, generating
diploid zygotes (9). The zygotes in turn become motile and elongated stages known as
ookinetes (10), which invade the midgut wall of the mosquito, where they develop into oocysts (11). The oocysts grow, rupture, and release
sporozoites (12), which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle (1).From
Centers for Disease Control Parasites and Health website.
