The parasite responsible for a form of malaria now spreading from macaques to humans in South Asia could evolve to infect humans more efficiently, a step towards enhanced transmission between humans, according to a new study from Harvard T.H. Chan School of Public Health. The researchers say that defining the means by which the Plasmodium knowlesi parasite invades red blood cells could lead to interventions to prevent emergence of the zoonosis into the human population.

The researchers identified a sugar variant on the surface of human red blood cells that currently limits the ability of P. knowlesi to invade, and demonstrated that the monkey malaria parasite has the ability to evolve to get around this barrier and pass into the human population in a more virulent form.

The study will appear online April 4, 2016 in Nature Communications.

“With increasing concern about the spread of P. knowlesi into human populations, it is great to be able to gain insight into what the molecular stumbling blocks are for P. knowlesi infection of humans, and how the parasite can potentially overcome them,” said first author Selasi Dankwa, who carried out the work while a doctoral student in the Department of Immunology and Infectious Diseases at the Harvard Chan School.

The macaque malaria parasite P. knowlesi has emerged as a major source of human infections in Southeast Asia, as the monkey’s habitats are encroached upon through logging and farming. While most human infections are mild, increasing numbers of severe infections are being reported.

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