Plasmodium knowlesi

Plasmodium knowlesi is a primate malaria parasite commonly found in Southeast Asia. It causes malaria in long-tailed macaques (Macaca fascicularis), but it may also infect humans, either naturally or artificially.

Plasmodium knowlesi is the sixth major human malaria parasite (following the division of Plasmodium ovale into 2 species). It may cause severe malaria as indicated by its asexual erythrocytic cycle of about 24 hours, with an associated fever that typically occurs at the same frequency (i.e. the fever is quotidian). This is an emerging infection that was reported for the first time in humans in 1965. It accounts for up to 70% of malaria cases in certain areas in South East Asia where it is mostly found. This parasite is transmitted by the bite of an Anopheles mosquito. Plasmodium knowlesi has health, social and economic consequences for the regions affected by it.