Malaria parasite transmitted from chimpanzees to humans 5,000yrs ago

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Washington, Aug 4 (ANI): University of California researchers claim to have identified what they believe is the original source of malignant malaria-a parasite found in chimpanzees in equatorial Africa.

UC Irvine biologist Francisco Ayala says that genetic analyses have indicated that the deadly parasite was transmitted to humans from chimpanzees perhaps as recently as 5,000 years ago, and possibly through a single mosquito.

Previously, malaria's origin had been unclear.

The discovery could aid the development of a vaccine for malaria, which sickens about 500 million people and kills about 1.5 million each year.

The finding also deepens the understanding of how infectious diseases, such as HIV, SARS, and avian and swine flu, can be transmitted to humans from animals.

"When malaria transferred to humans, it became very severe very quickly. 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," said Ayala, co-author of the study report.

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 it was assumed that the two had existed separately in humans and chimpanzees for the last five million years.

In the current study, the researchers examined several new strains of the parasite found in blood taken from wild and wild-born chimpanzees in Cameroon and Ivory Coast sanctuaries during routine health exams.

A gene analysis linked one chimpanzee strain to all worldwide strains of the human malaria parasite.

The connection has indicated that one mosquito may have transferred malaria to humans.

As there is little genetic variance among strains of the human parasite, scientists believe that the transmission occurred in the recent past - maybe 5,000 to 2 million years ago - though an exact time could not be determined.

The results support an earlier hypothesis by Dr. Ajit Varki of UC San Diego and colleagues that genetic mutations made humans first resistant to sickness from the chimpanzee parasite, then extremely susceptible to illness from the human form.

They also corroborate an earlier finding that malignant malaria started spreading throughout the tropics and world about 5,000 years ago, when agriculture began in Africa.

The study has appeared online in the Proceedings of the National Academy of Sciences. (ANI)

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