PLASMODIUM

Life cycle of malarial parasite

Plasmodium is a genus, belonging to the parasitic group of protozoa. At present, more than 200 species of this genus are identified, out of which about 10 species infect humans. Among several species, Plasmodium falciparum is reported to cause maximum health complications and mortality in humans. Acute plasmodium infections, if left untreated, can progress to life-threatening conditions, whereas chronic infections can lead to severe anemia. It also infects animals like rodents, monkeys as well as birds. Plasmodium requires two hosts to complete its life cycle, namely, a mosquito vector and a vertebrate host. Extensive studies have been conducted on P. falciparum, as this protozoa causes malaria. Let's discuss in brief about the life cycle of P. falciparum.

The Vertebrate Stage: Initial InfectionThere 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 PhaseSporozoites infect liver cells and mature into capsules called schizonts. These eventually rupture to release merozoites, which continue to multiply in the liver.

The Blood PhaseMerozoites 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: InfectionWithin 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: TransmissionThe 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.

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