A new study has shed light on why a monkey malaria parasite that typically caused only mild infection in humans is now beginning to cause severe disease and death—and how it has the potential to become a dangerous human-to-human pathogen. In a multidisciplinary study using experimental and modeling approaches, researchers at Harvard School of Public Health (HSPH) showed that while the parasite usually prefers only young red blood cells, it can adapt over time to invade both younger and older cells—thus greatly increasing its virulence.

The study appeared March 27, 2013 online in Nature Communications. Senior authors were Manoj Duraisingh, associate professor of immunology and infectious diseases, and Caroline Buckee, assistant professor of epidemiology at HSPH.

“We are excited to be able to culture this parasite for the first time in human red blood cells, but also to explore the population-level implications with mathematical models,” said Duraisingh. “This study identifies a likely mechanism for virulence evolution of a recent human parasite.”

The study is the first to provide a mechanistic explanation of the virulence of Plasmodium knowlesi, a macaque malaria parasite. This parasite usually proliferates poorly in human blood because it prefers only the youngest of red blood cells. (Red blood cells live for three months in the bloodstream.)

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