Then the researchers began noticing the much higher death rate among the SIV-positive chimpanzees. And infected females, it turned out, were much less likely to give birth. When they did, their babies had a very low chance of survival.
Other symptoms of the AIDS-like syndrome remain unknown, though preliminary results suggest weight loss and lethargy may be among the side effects. "Again, this will be the focus of intensive study over the next several years, since we just discovered the death hazard," Lonsdorf said.
"Just Like AIDS"
Searching for the culprit, veterinary pathologist Karen Terio, looked at tissue samples from an SIV-positive female chimpanzee that had died at Gombe.
"As I was looking through her tissues I was completely taken aback," said Terio, also a co-author of the study, published today in the journal Nature.
"I couldn't believe what I was seeing, as the tissue changes looked just like those of AIDS. I kept looking for another reason and couldn't find one. ... " recalled Terio, of the University of Illinois.
Study co-author Dominic Travis remains cautious.
"We don't really know how bad this is in Gombe, let alone if or how it happens elsewhere," said Travis, a veterinary epidemiologist at the Lincoln Park Zoo.
Hope for Fighting AIDS in Humans?
The researchers are optimistic that their potentially dispiriting study could hold blessings in disguise, in the form of increased funding for ape-health research—or potential medical advances for humans.
(Also see "Search for a Cure: AIDS Turns 20" from National Geographic magazine.)
"We can learn a lot about disease mechanisms by studying the same disease in different species," the University of Illinois's Terio said.
Study leader Beatrice Hahn, of the University of Alabama, added, "Chimps may be one [evolutionary] step ahead of us humans in managing the disease. And figuring out how they deal with their infection may ultimately help people infected with HIV."
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