Plasmodium Knowlesi - Life Cycle

Life Cycle

Plasmodium knowlesi parasite replicates and completes its blood stage cycle in 24 hour cycles resulting in fairly high loads of parasite densities in a very short period of time. This makes it a potentially very severe disease if it remains untreated. Life cycle: merozoite → trophozoites → schizont → merozoite. These stages of Plasmodium knowlesi are microscopically indistinguishable from Plasmodium malariae and the early trophozoites are identical to those of Plasmodium falciparum .

Mosquito stages: A mosquito ingests gametocytes, which have been formed in the mammalian host. These are either microgametocytes (which are male gametocytes) or macrogametocytes (which are female gametetocytes). These gametocytes mature into microgametes and macrogametes respectively, and then fertilize to form zygotes within the midgut of the mosquito. The zygotes mature into ookinetes, then into oocysts. Finally, the oocysts mature to release sporozoites which move to salivary gland of the mosquito.

Summary: gametocyte → (microgamete or macrogamete) → zygote → ookinete → oocyst → sporozoites.

In man: exoerythrocytic stage (in the liver): The sporozoites are injected into humans when the mosquito bites and they travel to the liver through blood stream and undergo asexual reproduction to become merozoites through schizonts in the liver cell. Hypnozoites in the liver has not yet been found.

Summary: sporozoites → schizonts → merozoites.

In man: erythrocytic stage (in the blood): Merozoites are unleashed into the blood stream to infect erythrocytes constituting one asexual cycle of infection of the erythrocytes. Within the red blood cells some merozoites develop into trophozoites, which in turn mature into schizonts that rupture to release merozoites, while others develop into microgametocytes or macrogametocytes. These gametocytes remain in the blood to be ingested by mosquitoes.

Summary: Merozoite → trophozoite → schizont → merozoites.