Posted for Mico Tatalovic
Malaria was originally a chimp disease that jumped to humans sometime between 3 million and 10,000 years ago, a new study suggests. This cross from chimps to humans might even have been down to a single infected mosquito.
Of the 500 million people malaria infects each year, 85% of cases are down to the malaria parasite Plasmodium falciparum, whose closest known relative is a chimpanzee parasite Plasmodium reichenowi. Until now scientists thought that both parasites evolved from a common ancestor that then diverged separately into human and chimp lineages (press release).
In the new study, published in PNAS, researchers analysed genes from eight new strains of P. reichenowi, from wild and wild-born captive chimpanzees in Cameroon and Côte d’Ivoire, and compared them to human P. falciparum. They found that human malaria descended directly from the chimp malaria, and that this jump likely happened only once. A lack of genetic variations between different examples of the human parasite further suggests the species barrier could have been crossed as recently as 10,000 years ago.
“For me, this is the microbiological equivalent of discovering the origins of HIV,” says study author Nathan Wolfe, of the Global Viral Forecasting Initiative (CNN). “It jumped over just like SARS did, just like avian flu did, just like HIV did. What is really crucial, what is significant, is it continuing to jump over?”
Human agriculture and closer contact with wild animals as agriculture impinges on the wild habitats can create conditions for a species jump.
“Today, human encroachment into the last forest habitats has further extended, leading to a higher risk of transfer of new pathogens, including new malaria parasites” Wolfe says. “What this finding demonstrates is that the kinds of jumps we’re having right now—HIV, SARS, etc.—could very well be the beginning of something that lasts for thousands of years.” [BBC, National Geographic]
As if to back up Wolfe’s warning, the first case of a new strain of HIV was recently reported, this time found to come from gorillas.
Image: Nathan Wolfe, Global Viral Forecasting Initiative.