Epidemiology

Knowlesi Enters the Malaria Mix

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Science  06 May 2011:
Vol. 332, Issue 6030, pp. 643
DOI: 10.1126/science.332.6030.643-a

What if a new and devastating form of malaria emerges? This scenario may be occurring in Southeast Asia, where a significant number of reported malaria cases were identified as being caused by Plasmodium knowlesi, until recently thought to be a monkey infection. This parasite has recently been recognized to cause a wide spectrum of human diseases that can result in complications and death. Lee et al. surveyed monkeys in Sarawak, Malaysia, and found very high levels of P. knowlesi infection in long-tailed macaques. Genetic analysis of human cases and macaques did not show any clustering or distinct lineages associated with host species. A relatively recent population expansion of the parasite occurred about 30,000 to 40,000 years ago, roughly coincident with major human settlement in Southeast Asia. The genetic data thus indicate that this is a previously unrecognized parasite rather than a newly emerging one, and that infection is zoonotic, arising when humans penetrate macaque habitats during forestry activities. Caution is necessary because further forest destruction might prompt the parasite and its mosquito vector to adapt to a future more numerous primate host species.

PLoS Pathol. 7, e1002015 (2011).

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