The malaria parasite is a microscopic, single-celled organism belonging to the genus Plasmodium. Human malaria is caused by five main species: Plasmodium falciparum, P. vivax, P. malariae, P. ovale (including P. ovale curtisi and P. ovale wallikeri), and P. knowlesi. These species differ in their geographical distribution, life-cycle characteristics, and potential to cause severe disease.
The parasite is transmitted to humans mainly through the bite of an infected female Anopheles mosquito. After entering the body, the parasites travel through the bloodstream to the liver, where they enter liver cells and multiply. They then leave the liver and infect red blood cells, where they continue to multiply. Repeatedly, infected red blood cells rupture, each time releasing parasites into the bloodstream, which contributes to symptoms such as fever, chills, and anemia.
Malaria parasites have a complex life cycle involving both humans and mosquitoes. In humans, they develop first in liver cells and then in red blood cells. Some parasites develop into sexual forms called gametocytes, which can be taken up by another female Anopheles mosquito when it feeds on an infected person. Inside the mosquito, the parasites undergo sexual reproduction and further development, eventually producing forms that can be transmitted to another person through a subsequent bite.
The severity and course of malaria vary by species and other factors, including the person’s immunity and general health. P. falciparum is particularly associated with severe and potentially fatal malaria. P. vivax and P. ovale can form dormant liver stages called hypnozoites, which may reactivate and cause relapses weeks, months, or even years after the initial infection. Unlike these two species, P. falciparum, P. malariae, and P. knowlesi do not form hypnozoites.
QUICK FACT
- Malaria is caused by a parasite, not a virus or bacterium. The parasite changes form throughout its life cycle, adapting to different environments within the human body and the mosquito.
- Most human malaria infections result from the bite of an infected female Anopheles mosquito, although transmission can also occur through infected blood, such as during a blood transfusion.
COMMONLY CONFUSED WITH
- Malaria: The disease caused by infection with malaria parasites. It is distinct from the parasite itself.
- Malaria vector: An organism that transmits the malaria parasite. For human malaria, the principal vectors are infected female Anopheles mosquitoes.
- Hypnozoite: A dormant liver stage of P. vivax and P. ovale that can reactivate and cause a malaria relapse.
- Antimalarial: A medicine used to prevent or treat malaria.
SEE ALSO
- Malaria
- Plasmodium
- Plasmodium falciparum
- Plasmodium vivax
- Anopheles Mosquito
- Malaria Vector
- Hypnozoite
- Antimalarial
- Artemisinin-Based Combination Therapy
