Classification: ICD-9 84.4; IDC-10 B53.1
Synonym: Knowlesi malaria, simian malaria
Agent: Plasmodium knowlesi, an intacellular protozoan parasite in the Phylum Apicomplexa. P. knowlesi is an Old World simian malaria parasite.
Reservoir: Long-tailed and pigtailed macaques, and banded leaf monkeys. P. knowlesi can also infect other primates, including New World marmosets (Callithrix jacchus), African olive baboons (Papio anubis), Old World macaques, and humans by blood passage and mosquito bites.
Vector: P. knowlesi transmission is restricted to the Leucosphyrus group of anophelines, consisting of 20 species.
Transmission: By mosquito bite. Experiments demonstrated human to human transmission with the mosquito as vector, but there is no direct human-to-human transmission.
Cycle: Monkey–mosquito–monkey; P. knowlesi has a short (24-hour) asexual lifeycle; humans are incidental hosts.