Asymptomatic Natural Human Infections With the Simian Malaria Parasites Plasmodium cynomolgi and Plasmodium knowlesi. (8th October 2018)

• Record Type: Journal Article
• Authors: Imwong, Mallika; Madmanee, Wanassanan; Suwannasin, Kanokon; Kunasol, Chanon; Peto, Thomas J; Tripura, Rupam; von Seidlein, Lorenz; Nguon, Chea; Davoeung, Chan; Day, Nicholas P J; Dondorp, Arjen M; White, Nicholas J
• Is Part Of: Journal of infectious diseases. Volume 219:Number 5(2019)
• Page Start: 695
• Page End: 702
• Publication Date: 2018-10-08
• Subjects: Asymptomatic -- natural -- human infections -- Plasmodium cynomolgi; Communicable diseases -- Periodicals; Diseases -- Causes and theories of causation -- Periodicals; Medicine -- Periodicals; Communicable Diseases -- Periodicals; Electronic journals; 616.9
• DOI: 10.1093/infdis/jiy519
• Languages: English
• ISSNs: 0022-1899

Abstract

Abstract: Background: In Southeast Asia, Plasmodium knowlesi, a parasite of long-tailed macaques ( Macaca fascicularis ), is an important cause of human malaria. Plasmodium cynomolgi also commonly infects these monkeys, but only one naturally acquired symptomatic human case has been reported previously. Methods: Malariometric studies involving 5422 subjects (aged 6 months to 65 years) were conducted in 23 villages in Pailin and Battambang, western Cambodia. Parasite detection and genotyping was conducted on blood samples, using high-volume quantitative PCR (uPCR). Results: Asymptomatic malaria parasite infections were detected in 1361 of 14732 samples (9.2%). Asymptomatic infections with nonhuman primate malaria parasites were found in 21 individuals living close to forested areas; P. cynomolgi was found in 11, P. knowlesi was found in 8, and P. vivax and P. cynomolgi were both found in 2. Only 2 subjects were female, and 14 were men aged 20–40 years. Geometric mean parasite densities were 3604 parasites/mL in P. cynomolgi infections and 52488 parasites/mL in P. knowlesi infections. All P. cynomolgi isolates had wild-type dihydrofolate reductase genes, in contrast to the very high prevalence of mutations in the human malaria parasites. Asymptomatic reappearance of P. cynomolgi occurred in 2 subjects 3 months after the first infection. Conclusions: Asymptomatic naturally acquired P. cynomolgi and P. knowlesi infections can both occur in humans. Clinical Trials Registration: NCT01872702. Abstract : Epidemiological studies in western Cambodia identified 21 subjects with asymptomatic monkey malaria parasite infections (8 with P. knowlesi infection and 13 with P. cynomolgi infection). These parasites represented 1.9% of all identified malaria parasites.