February 21, 2014
An international team of scientists has traced the origin of Plasmodium vivax, the second-worst malaria parasite of humans, to Africa, according to a study published this week in Nature Communications. Until recently, the closest genetic relatives of human P. vivax were found only in Asian macaques, leading researchers to believe that P. vivax originated in Asia.
The study, led by researchers from the Perelman School of Medicine at the University of Pennsylvania, found that wild-living apes in central Africa are widely infected with parasites that, genetically, are nearly identical to humanP. vivax.
This finding overturns the dogma that P. vivax originated in Asia, despite being most prevalent in humans there now, and also solves other vexing questions about P. vivax infection: how a mutation conferring resistance to P. vivax occurs at high frequency in the very region where this parasite seems absent and how travelers returning from regions where almost all humans lack the receptor for P. vivax can be infected with this parasite…
Ape P. vivax infects both gorillas and chimpanzees, unlike the ape precursor of P. falciparum, the deadliest human malaria parasite, which only infects gorillas. The origin of P. falciparum in gorillas was discovered several years ago by the same international group of investigators. The team continued its widespread screen of malaria parasite DNA in wild-living primates, and noted that P. vivax was also endemic in gorillas and chimpanzees in central Africa.
From these evolutionary relationships, the team concluded that P. vivax is of African — not Asian — origin, and that all existing human P. vivax parasites evolved from a single ancestor that spread out of Africa. The high prevalence of P. vivax in wild-living apes, along with the recent finding of ape P. vivax in a European traveler, indicates the existence of a substantial natural reservoir of P. vivax in Africa…
As a next step, the team will compare and contrast the molecular and biological properties of human and ape parasites to identify host-specific interactions and transmission requirements, thereby uncovering vulnerabilities that can be exploited to combat human malaria.
Weimin Liu, et al. African origin of the malaria parasite Plasmodium vivax. Nature Communications, 2014; 5 DOI:10.1038/ncomms4346