American Society of Tropical Medicine and Hygiene (ASTMH)
American Society of Tropical Medicine and Hygiene (ASTMH)
November 04, 2014
1 min read

P. knowlesi malaria cases increasing in Malaysia

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Sixty-eight percent of malaria patients hospitalized in Malaysian Borneo in 2013 were infected by the once-rare primate malaria parasite Plasmodium knowlesi, according to research data presented at the American Society of Tropical Medicine and Hygiene Annual Meeting in New Orleans.

Balbir Singh, PhD, of the University of Malaysia, Sarawak, and colleagues performed an epidemiologic study of the disease. Along with a review of host identification and laboratory diagnosis, they also examined historical data and treatment records for P. knowlesi within the region, including eight published studies on severe and fatal cases.

“This is a form of malaria that was once rarely seen in people, but today, in some remote areas of the country, all of the indigenous malaria cases we are seeing are caused by the P. knowlesi parasite,” Singh said in a press release. “If the number of cases continues to increase, human-to-human transmission by mosquitoes becomes possible. In fact, this may already have happened, which would allow P. knowlesi malaria to spread more easily throughout Southeast Asia.”

Singh said P. knowlesi malaria causes about 2,000 people to seek medical treatment each year, can multiply every 24 hours once in blood and causes severe malaria three times as often as the more common and deadly Plasmodium falciparum parasite.

The main hosts of the disease are the long-tailed and pig-tailed macaques that live within Malaysian tropical forests and other areas of Southeast Asia, although forest-dwelling mosquitoes act as vectors. The recent increase in cases over the past decade is likely due to logging or development activity currently removing these habitats, the researchers said. Additionally, this increased contact between humans and macaques could lead to more cases in the next few years.

Because of frequent complications and low samples in available data, more studies are required to determine the optimal treatment for P. knowlesi malaria, the researchers wrote. What’s more, the parasite’s recent discovery in Vietnamese mosquitoes could mean that human-to-human transmission is becoming more frequent.

“Clinicians and health care workers should be made aware of the potential for fatal outcomes in P. knowlesi infections, and there should be continued surveillance of knowlesi malaria,” the researchers concluded.

For more information:
Singh B. Symposium #33. Presented at: American Society of Tropical Medicine and Hygiene Annual Meeting; Nov. 2-6, 2014; New Orleans.

Disclosure: The researchers report no relevant financial disclosures.