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Malaria may have come from chimps: study

(Xinhua)
Updated: 2009-08-04 13:17

WASHINGONT: Researchers have identified what they believe is the original source of malignant malaria: a parasite found in chimpanzees in equatorial Africa, University of California Irvine (UCI) said in a press release on Monday.

UCI's biologist Francisco Ayala and colleagues think the deadly parasite was transmitted to humans from chimpanzees perhaps as recently as 5,000 years ago, and possibly through a single mosquito, genetic analyses indicate. The study appears online Monday in the Proceedings of the National Academy of Sciences.

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This discovery could aid the development of a vaccine for malaria, which sickens about 500 million people and kills about 1.5 million each year. It also furthers understanding of how infectious diseases such as HIV, SARS, and avian and swine flus can be transmitted to humans from animals.

"When malaria transferred to humans, it became very severe very quickly," said Ayala, co-author of the study that reports these findings. "The disease in humans has become resistant to many drugs. It's my hope that our discovery will bring us closer to making a vaccine."

Human malignant malaria is caused by a parasite called Plasmodium falciparum, which is responsible for 85 percent of all infections and nearly all malaria deaths.

Chimpanzees were known to carry a closely related parasite called Plasmodium reichenowi, but most scientists assumed the two had existed separately in humans and chimpanzees for the last five million years.

Scientists in the current study examined several new strains of the parasite found in blood taken from wild and wild-born chimpanzees in Cameroon and Cote d'Ivorie sanctuaries during routine health exams.

A gene analysis linked one chimpanzee strain to all worldwide strains of the human malaria parasite. This connection suggests that one mosquito may have transferred malaria to humans. Because there is little genetic variance among strains of the human parasite, scientists believe the transmission occurred in the recent past -- maybe 5,000 to 2 million years ago -- though an exact time could not be determined.