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AIDS Can Sicken, Kill, Chimpanzees After All, Researchers Find
  By Rob Waters
July 23 (Bloomberg) -- Chimpanzees, the closest animal relatives to humans, aren?t immune to the deadly impact of AIDS as scientists long believed, researchers reported in the journal Nature.
Wild chimpanzees infected with a version of the simian immunodeficiency virus, or SIV, had a 10-to-16-fold higher risk of dying early than uninfected chimps, said the scientists, who followed 94 chimps for nine years at a national park in Tanzania. Infected females were less likely to give birth and had a higher infant mortality rate when they did, the authors found.
Scientists had long believed that primates infected with one of the 40 strains of the simian virus didn?t develop symptoms. While that?s true of two species that have been closely studied -- African green monkeys and sooty mangabeys -- chimps are an exception, said lead study author Beatrice Hahn, an AIDS researcher at the University of Alabama at Birmingham.
"SIVcpz, like HIV-1 in humans, has a substantial negative impact on the health, reproduction and lifespan of chimpanzees in the wild," Hahn wrote in the journal. "The assumption was made that all primates are the same and it isn?t true," she said yesterday in a telephone interview.
Studying disease in chimpanzees had been difficult because AIDS is slow to develop and apes are hard to track in the wild, Hahn said. The development of new tests that detect antibodies to the virus in stool and urine samples allowed Hahn and her colleagues to begin tracking infection rates in chimps in 2000.
Infected Chimps
The team identified 17 chimps in Gombe National Park in Tanzania that were infected and found a 10-to-16-fold greater risk of death over nine years compared with 77 uninfected chimps. They provided the wide range of risk because they couldn?t be certain in some cases whether chimps that disappeared had actually died or whether some chimps were definitely infected.
There was "definitive" evidence that SIV was spread through sexual contact among the chimps and "suggestive" evidence that it was transmitted from mother to infant, Hahn said. One mother and her daughter each became infected with the same genetic version of the virus. Hahn said there was a chance that both became infected by having sex with the same male.
The findings will allow scientists to study why some primates don?t get sick, others get sick sometimes, and still others are highly susceptible, Hahn said. Sooty mangabeys, for example, appear immune to the disease, yet they are believed to be the origin of HIV2, the second of two viruses that cause AIDS in humans.
Humans who aren?t treated with drugs are much more likely to get ill or die from an infection with one of the HIV viruses than chimps, Hahn said.
"Now we have three different species and systems to study and we can look at how these viruses interact with the host in each," she said. "We expect to get new insights as to why HIV is so pathogenic in humans."
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