Plasmodium Life Cycle

Plasmodium is a genus of protozoan parasites that has life cycle consisting of two distinct phases. The first involves a mosquito which acts as a vector for the disease. The second phase is infection of the vertebrate host. There are approximately 150 species of plasmodium, four of which have been identified as human parasites. Plasmodium is the infectious agent that causes malaria in humans.

The Vertebrate Stage: Initial Infection

• There are two distinct phases within the vertebrate stage; the hepatic phase and the blood phase. When a mosquito carrying the disease bites a host, sporozoites enter into the bloodstream.

The Hepatic Phase

• Sporozoites infect liver cells and mature into capsules called schizonts. These eventually rupture to release merozoites, which continue to multiply in the liver.

The Blood Phase

• Merozoites eventually infect red blood cells where they become trophozoites. These will then mature into schizonts that will rupture, releasing more merozoites. This process will continue repeatedly. Some trophozoites mature into gametocytes that will eventually be ingested by a mosquito.

The Mosquito Stage: Infection

• Within the mosquito, male and female gametocytes combined to form zygotes. These mature into mobile ookinetes that move to the mosquito's midgut and develop into a oocysts. The oocysts than grow and rupture, releasing sporozoites.

The Mosquito Stage: Transmission

• The sporozoites travel to the mosquito's salivary glands, where they will wait until the mosquito bites a host. The sporozoites are transmitted to the host through the mosquito's saliva, restarting the life cycle.