Question

Describe the life-cycle of plasmodium in human.

Answer 1

The primary causative organism, Plasmodium falciparum, requires both the Anopheles mosquito and humans to complete its life cycle. The sexual cycle of the protozoan occurs in the mosquito. Immature sporozoites in the saliva of the mosquito are transmitted to the human when the mosquito bites the skin to feed on the blood of man.

In the body of man, the parasites reach the liver, multiply and enter the blood where it attacks red blood cells for their haemoglobin. The red blood cells rupture to release the merozoites to attack more red blood cells. Haemozoin, a toxin is also released when the RBC ruptures. This causes chill and high fever. Some of the merozoites are transformed into gametocytes which are sexually mature and are transmitted back to another biting mosquito. In the mosquito, the gametocytes start the sexual cycle. The details of the life cycle is summarized in the figure. The other three species of Plasmodium also infect humans. The cycles of fever coming every two (Plasmodium falciparum) or three days (Plasmodium vivax) arise due to the release of the merozoites from the red blood cells.