Which protist causes malaria?

The protist that causes malaria is Plasmodium. This genus contains single-celled parasitic eukaryotes whose complex life cycle alternates between vertebrate hosts and blood-feeding mosquitoes.

An infected female Anopheles mosquito injects Plasmodium sporozoites while feeding. The parasites first travel to the liver, where they multiply. They then enter the bloodstream as merozoites and invade red blood cells. Repeated infection and destruction of those cells produces the fever, chills, anemia, and other symptoms associated with malaria.

Plasmodium is a genus rather than one single species. Plasmodium falciparum causes the most dangerous form of human malaria and is responsible for most malaria deaths. Other human-infecting species include P. vivax, P. malariae, P. ovale, and P. knowlesi. Some Plasmodium species infect birds, reptiles, and other mammals.

A common mistake is to answer “mosquito.” Mosquitoes transmit malaria, but they are the vector, not the pathogen. Amoeba and Giardia are also protists, yet they cause different diseases; Trypanosoma causes diseases such as sleeping sickness and Chagas disease.