Scientists say they may have tracked down the origins of the deadly disease malaria — chimpanzees.
In recent years diseases like HIV-AIDS and Ebola have been traced to chimpanzees, and a study being released Tuesday shows that this is nothing new, according to Dr. Nathan D. Wolfe, an author of the report in Proceedings of the National Academy of Sciences.
"Malaria has been a human disease as long as history," Wolfe, of Stanford University and the Global Viral Forecasting Initiative, said in a telephone interview.
"It is now clear that a new disease that successfully jumps from an animal to a human can last not just for decades, but millennia or more," Wolfe said. "This makes the task of stopping future disease spillovers from animals to humans vital, not only for saving lives today, but for the health of people for many generations to come."
According to the U.S. Centers for Disease Control and Prevention, each year more than a million people, mostly children, die of malaria worldwide.
Malaria is caused by a parasite, Plasmodium falciparum, which is transmitted from person to person via mosquitoes.
It was known that chimpanzees could harbor a related parasite, Plasmodium reichenowi. The researchers, led by Wolfe and Francisco Ayala of the University of California, Irvine, studied chimps in Cameroon and Ivory Coast and found it is more common than had been thought.
Conventional wisdom had been that the two parasites diverged from a common origin, Wolfe said, but a comparison of the two indicates that the human version more likely developed from the chimpanzee type.
"We now know that malaria, while at least thousands of years old, did not originate in humans but rather was introduced into our species, presumably by the bite of a mosquito that had previously fed on a chimpanzee."
Now, Wolfe said, the goal is to learn more about the chimp parasites and try to figure out how they spread to people.
The researchers said the shift of the malaria parasite to humans could have taken place as long as 2 million to 3 million years ago, or as recently as 10,000 years ago.
A better understanding of these chimp parasites might lead to improved treatments for malaria or even development of a vaccine, Wolfe said, noting early smallpox vaccines were developed from the related cowpox.
The research was funded by the National Institutes of Health, Tufts University and the National Geographic Society.
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Proceedings of the National Academy of Science: http://www.pnas.org