Researchers at the University of Pennsylvania Perelman School of Medicine published study findings on Thursday that showed the Plasmodium vivax malaria parasite originated in Africa. and not Asia as previously believed.
The closest genetic relatives of human P. vivax had been found only in Asian macaques, which led researchers to believe the virus originated in Asia.
The Penn researchers found wild-living apes in central Africa that were infected with parasites identical to human P. vivax, which overturned the long-held understanding of the virus.
Researchers said the discovery solves other questions about the virus, such as how resistance to the virus in the area occurs at such a high rate, and how travelers returning from the area are infected with the virus when the residents of the area are not.
The project researchers included professors of medicine and microbiology at Penn Beatrice Hahn and George Shaw, Paul Sharp of the University of Edinburgh and Martine Peeters from the Institut de Recherche pour le Developpement and the University of Montpellier.
The group collected more than 5,000 ape fecal samples from dozens of locations in Africa to find P. vivax DNA.
"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," Hahn said.
The researchers said that ancestral P. vivax was able to infect humans, gorillas and chimpanzees in Africa until the Duffy negative mutation began to spread.
"The existence of a P. vivax reservoir within the forests of central Africa has public health implications," Peeters said. "First, it solves the mystery of P. vivax infections in travelers returning from regions where 99 percent of the human population is Duffy negative. It also raises the possibility that Duffy positive humans whose work may bring them in close proximity to chimpanzees and gorillas may become infected by ape P. vivax. This has already happened once and may happen again, with unknown consequences."
The researchers will compare the molecular and biological makeup of the parasites to identify host-specific interactions and transmission requirements. They hope this will uncover vulnerabilities in the virus that can be used to create a vaccine and treatment options for human malaria.