TUESDAY, SEPTEMBER 27, 2016

Researchers trace origins of malaria parasite

An international research team traced the origin of Plasmodium vivax, the second-worst malaria parasite to humans, to Africa, according to a study recently published in Nature Communications.

The team, led by researchers from the Perelman School of Medicine at the University of Pennsylvania, challenged conventional beliefs that P. vivax originated in Asia. Researchers previously surmised that the closest genetic relatives of human P. vivax came from Asian macaques.

The researchers determined that wild-living apes in central Africa are widely infected with parasites that are almost genetically identical to P. vivax.

After testing over 5,000 ape fecal samples from dozens of field stations and sanctuaries in Africa and constructing a family tree of the parasite's DNA sequences, the researchers determined that P. vivax is of African origin. This solved a paradox related to a human mutation that confers resistance to the parasite in Africa.

"Our finding that wild-living apes in central Africa show widespread infection with diverse strains of P. vivax provides new insight into the evolutionary history of human P. vivax and resolves the paradox that a mutation conferring resistance to P. vivax occurs with high frequency in the very region where this parasite is absent in humans," Beatrice Hahn, one of the study authors, said.

The researchers determined that the Duffy negative mutation began to spread around 30,000 years ago in Africa, eliminating P. vivax from humans there.

The team said the reservoir of P. vivax in Africa has public health implications, as Duffy positive humans could come into close proximity with infected primates and become infected with ape P. vivax. They said the parasite could also spread via international travel to countries where P. vivax is actively transmitted.

The researchers plan to compare and contrast the biological and molecular properties of ape and human parasites to uncover vulnerabilities that can be exploited to battle human malaria.