Malarial parasites are microorganisms belonging to the genus Plasmodium. To date, there are more than 100 species of Plasmodium, which can infect many animal species such as reptiles, birds, and various mammals. There are four species of Plasmodium that have been recognized to infect humans in nature as well as a fifth that is a cause of zoonotic malaria in humans. The four species that infect humans are: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. The fifth species naturally infects macaques, can cause zoonotic malaria in humans, and is called Plasmodium knowlesi.
