This is an easy article that aims to describe the life cycle of the malaria parasite known as Plasmodium which is transferred to man from Mosquito bites. Malaria life cycle varies according to the type of plasmodium parasite that is causing the infection. There are slight variations in the life cycle of the plasmodium are these variations are indicated in the steps for description of the plasmodium life cycle.
Facts about Malaria Life cycle in human body
- The Malaria Life cycle is the same as Plasmodium life cycle as the parasite is the cause of the malaria
- Gametocytes are the sexual forms of plasmodium parasites this simply means that the sexual forms represent the male and female forms that need to be taken in the blood by mosquitoes. The gametocytes are the ones that join to reproduce in the mosquito.
- The asexual forms of plasmodium parasites include any other form apart from the gametocytes. The asexual forms include merozoites, trophozoites, and sporozoites.
- Plasmodium vivax and Plasmodium ovale mainly attack reticulocytes and young erythrocytes (red blood cells) while Plasmodium malariae tends to attack older cells; Plasmodium falciparum attacks any stage of red blood cell
Steps in the Life cycle of Plasmodium Parasite (Simple Explanation of Malaria Life cycle)
- The female anopheles mosquito is the one responsible for causing malaria and it is this specie that sucks blood of humans and during this, it also infects humans with plasmodium parasite that cause malaria.
- The female anopheles mosquito sucks an infected blood containing the gametocytes from any infected individual
- In the gut of the mosquito, the gametocytes develop into Sporozoites. This takes duration of about 7 to 20 days for the gametocytes to develop into sporozoites.
- The sporozoites when formed move to the salivary gland of the mosquito.
- The sporozoites in the salivary gland are then inoculated into another human when the mosquito wants to bite and suck another blood. This new human host becomes infected with malaria (this is why sporozoites are said to be the infective forms of plasmodium).
- When your immune system is strong to destroy these infective forms, you can easily clear the infection and the malaria life cycle is terminated.
- When the immune system is unable to completely destroy and clear the sporozoites, they are then taken to the liver cells.
- Sporozoites develop and multiply to form Merozoites when they infect liver cells (this stage of the malaria life cycle is referred to as the Hepatic sporogeny). This stage of the hepatic sporogeny occurs before the release into blood and before they infect the red blood cells; hence this stage is also called the Pre-erythrocytic stage.
- After multiplication for few days inside the liver cells, the merozoites rupture the hepatocytes (liver cells) and are released into the blood stream. In the life cycle of Plasmodium vivax and Plasmodium ovale, some parasites remain dormant in the liver and are called Hypnozoites. These dormant forms can become active and released into the blood anytime and can cause malaria even after treatment. This may make it seem as if the antimalarial drug use for treatment of the malaria is not efficient this is the reason why malaria relapse may still occur a few days after treatment. In this case, drugs that destroy the hypnozoites in the liver should be in areas where plasmodium vivax and ovale are endemic.
- The released Merozoites in the blood then infect red blood cells.
- In the red blood cells, the parasites again develop and multiply into Trophozoite, and then to Schizont and finally into new merozoites again.
- When they form new merozoites, the erythrocyte (red blood cells) then rupture and release the new merozoites which then infect further red blood cells. (The cycle of merozoites changing and multiplying to schizonts and back to merozites is called erythrocytic schizogony). This stage takes about 48 hours in Plasmodium falciparum, Plasmodium vivax and Plasmodium ovale; whereas it takes about 72 hours in Plasmodium malariae.
- In the red blood cells, instead of all the merozoites to develop into trophozoites, some develop into gametocytes and are not released from the red cells pending when another female anopheles mosquito takes it up to complete the malaria life cycle.
There are other rare conditions through which the malaria life cycle can continue. These other conditions are not typical to the cycle and include blood transfusion and organ transplant these conditions can cause transmission of malaria but are not part of the malaria life cycle because it is not typical.