Researchers have discovered the first case of a virus related to HIV in a wild chimpanzee, strengthening their argument that chimps are the source of the AIDS virus in people.
A 1999 study of captive west central African chimps with a virus closely related to HIV concluded that chimpanzees were most likely the source of the human infection.
But because the disease was seen only in captive chimps that are not likely to have transmitted it, the researchers looked for a wild chimp with the infection.
Now, they report in the journal "Science" that they have found one in east Africa.
The animal's strain is not closely related to HIV, which rules out east African chimps as the natural source of the human infection. But the University of Alabama physician who led the study, Beatrice Hahn, says it bolsters the theory that a wild west central African animal was the source because it shows non-captive chimps do harbor the disease. "Yes, this virus infection can be detected in chimpanzees in the wild and thus means that chimpanzees are a natural host of this particular infection," she says. "That's just a formal proof. Not that we didn't suspect this before, but now we know for a fact."
The wild chimp with the virus is a 23-year-old male in Tanzania's Gombe Stream National Park. The researchers say the discovery of the virus in only one animal in not surprising, given the habitat destruction and decimation of chimpanzee populations throughout Africa.
Dr. Hahn and her colleagues continue to gather and analyze fecal and urine samples from chimps in Gombe and elsewhere in Africa to see if they can detect the virus in more wild animals.
They say their work is possible only because they were able to develop a very sensitive, non-invasive test that could detect the virus in wild chimp feces and urine deposits. Dr. Hahn says this means they did not have to capture the endangered animals to take blood samples. "It opens a new door for us that we didn't have before," she says. "It's the only way to do what we want to do, and that is a systematic survey of wild living chimpanzees as far as their infection levels are concerned and as far as the types of viruses that they harbor are concerned."
The researchers say that finding the HIV-related virus for the first time in the wild offers the opportunity to study the natural transmission of this family of viruses in their natural host. This, they add, may lead to better understanding of the cross-species transmission that brought about the AIDS pandemic.