Zoonotic malaria:  Plasmodium knowlesi, an emerging pathogen.
OBJECTIVE
The emergence of Plasmodium knowlesi, a parasite of Southeast Asian macaques, into the human population is ongoing and widespread across Southeast Asia. Humans entering P. knowlesi transmission areas are at risk. Patients present with uncomplicated, complicated and fatal disease, therefore prompt accurate diagnosis and treatment are essential. This review focuses on recent descriptions of asymptomatic and symptomatic infections in children, pathophysiology in adults, treatment and diagnosis, and highlights the importance of monitoring transmission and host-switch events.


RESULTS
New reports on P. knowlesi infections identify regional differences in aetiology and vector species. Parasitaemia is associated with disease severity and specific diagnostic tools are required. Treatment failures have not been reported. The severe form of P. knowlesi malaria can be compared with severe falciparum malaria to inform the pathophysiology of both infections.


CONCLUSIONS
P. knowlesi presents new challenges to malaria-control efforts in Southeast Asia. Sensitive and specific diagnostic tools are required for communities and travellers at risk. Currently P. knowlesi transmission appears to occur away from human settlements. However, ongoing host-switch events from macaques to humans cannot be excluded. Changes in P. knowlesi transmission across the region should be monitored to preempt outbreaks of this virulent pathogen.
Infection and Immunity Research Centre, Division of Clinical Sciences, St George's, University of London, Cranmer Terrace, London, UK. coxsingh@gmail.com
Janet
J
Cox-Singh
D000818:Animals; D000962:Antimalarials / Q000627:therapeutic use; D001208:Asia; D021821:Communicable Diseases, Emerging / Q000469:parasitology*; D004197:Disease Reservoirs / Q000469:parasitology; D004199:Disease Vectors; D006801:Humans; D008251:Macaca / Q000469:parasitology; D008288:Malaria / Q000175:diagnosis / Q000188:drug therapy / Q000469:parasitology* / Q000635:transmission; D018512:Parasitemia / Q000469:parasitology; D016790:Plasmodium knowlesi / Q000472:pathogenicity
D000962:Antimalarials