Malaria parasites are micro-organisms that belong to the genus Plasmodium. There are more than 100 species of Plasmodium, which can infect many animal species such as birds, reptiles, and various mammals. Human malaria is transmitted by females mosquitoes of the genus Anopheles. Four species of Plasmodium (P. falciparum, P. malariae, P. vivax, and P. ovale) have long been recognized to infect humans in nature. In addition there is one species (P. knowlesi) that naturally infects macaques which has recently been recognized to be a cause of zoonotic malaria in humans. Infection with malaria parasites may result in a wide variety of symptoms, ranging from absent or very mild symptoms to severe disease and even death.