The Malaria Life Cycle – A Complete Look

The malaria life cycle requires two hosts, as the malarial parasite, Plasmodium, must shift from mosquito to human, and vice versa. The mosquito is the intermediary invertebrate host, whereas the human is the perfect vertebrate host.

malaria life cycle

The malaria life cycle is quite similar in all the strains of Plasmodium that cause malaria.

A Look At The Malaria Life Cycle

Here’s a detailed look at the malaria life cycle, starting with the causes of malaria.

Exo-Erythrocytic Schizogony

When a person is bitten by a female Anopheles mosquito, sporozoites are introduced into his blood. Within 40 minutes, these sporozoites travel through the person’s blood stream into his liver cells, where they mature and develop into the next stage, known as schizonts. These schizonts then rupture to release thousands of tiny merozoites in the blood after a period of about 16 days.

The Plasmodium vivax and Plasmodium ovale strains of the parasite can continue to remain in the person’s liver in an inactive state for a long time. They are called hypnozoites. On re-activation of these parasites, the patient can suffer a relapse after several weeks, months, or years following the malarial infection. This preliminary reproduction of the malarial parasite in the liver is known as exo-erythrocytic schizogony.

Erythrocytic Schizogony

In this phase, the parasites undergo a phase of asexual multiplication in the red blood cells. This phase is called erythrocytic schizogony and it releases merozoites into the patient’s blood. The other red blood cells are invaded by merozoites and they develop into trophozoites.

During their developmental process, the trophozoites take in the hemoglobin present in the red cells, leaving behind a pigment known as hemozoin, which is a mixture of hematin and protein. This pigment contains iron and it is visualized as dark granules in the body of the parasite. These granules are more distinct in the later stages of the development of the parasite.

The Development Of Parasitemia

Following the division of the mature trophozoites in the red blood cells, the formation of separate merozoites occurs, causing a schizont. Following complete development, the schizont bursts out of the red blood cell containing it, releasing the merozoites into the bloodstream. Then new red blood cells are infected by these merozoites and the procedure of asexual division in the blood resumes. Some of the merozoites that enter the red blood cells do not develop into trophozoites, instead they develop into gametocytes.

This process occurs in the capillaries present in deep tissues. Female/macro-gametocytes or male/micro-gametocytes enter the mosquito as an ookinete, which penetrates the wall of the stomach. The development of an oocyst then takes place. The oocyst ruptures and releases sporozoites that break into the salivary glands. This cycle of erythrocytic schizogony is repeated time and again in due course of the infection, resulting in an aggravating a condition called parasitemia.

The Length Of The Malaria Life Cycle

Certain factors, like the species of Plasmodium, the ambient temperature, and the mosquito host, all play an important role in determining the duration of the developmental stage in the mosquito. This may last for about 8 days, as in Plasmodium vivax, or even for a month, as seen in Plasmodium malariae. The malaria life cycle is essentially very similar in all strains of the Plasmodium parasite.

Malaria affects millions of people worldwide, especially those hailing from tropical and sub-tropical regions, so it very important to be have up-to-date information about this disease. You can begin by studying the life cycle of the disease, along with other common malarial symptoms.

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