HIV-Like Virus Found In
Only One Wild Chimp

By Amy Norton

NEW YORK (Reuters Health) - The scientists who first reported evidence that the HIV epidemic got its start in west-central African chimpanzees have found that the monkey counterpart to HIV does occur in chimps in the wild--but perhaps only rarely.
Dr. Beatrice H. Hahn and her colleagues had previously found that the west-central African chimpanzee subspecies Pan troglodytes (P. t.) troglodytes harbor strains of simian immunodeficiency virus (SIV) that are closely related genetically to HIV.
Researchers had long suspected that HIV arose as a result of a viral ``cross-species jump'' from primates to humans. The theory is that, through contact with chimpanzee blood--possibly through hunting them and eating the meat--humans were exposed to SIV. Some scientists speculate the HIV epidemic took off in Africa due to modern-day cultural changes such as increased population movement and breakdowns in traditional lifestyles.
Hahn told Reuters Health that her team's new finding ''confirms and extends'' the belief that an African chimp population--most likely the west-central population--are the origin of HIV.
Their original finding of the HIV-related SIV strains, called SIVcpz, were confined to chimpanzees in captivity, she explained.
``Our critics,'' she said, ``rightfully pointed out that we have no clue what's going on in the wild.''
In looking at urine and fecal samples from 58 wild chimpanzees in three African nations, her team found that SIVcpz does occur in the wild. But they found it in only one chimp, according to the report published in the January 18th issue of Science.
This one chimp lived in Gombe National Park in Tanzania, in the easternmost part of the chimpanzee range, the researchers report. The animal was also a member of the subspecies P. t. schweinfurthii--meaning, Hahn said, that her team's original findings have been extended to another African region and another chimp subspecies.
But the very low incidence of SIVcpz her team found was ''surprising,'' Hahn said.
She pointed to some possible explanations, however. For one, SIVcpz, by all appearances, does not spread very ''efficiently'' among chimps--a point that Hahn said will be the subject of more study.
And, she added, Gombe National Park, where the new case was found, has been isolated ``like an island'' for the past decade or so. This fact, coupled with a sharp decline in the chimp population, suggest that SIVcpz could have recently become uncommon in this region.
``We don't know what it was like 50 years ago,'' Hahn said.
But there is no indication that chimps in this area might be the origin of the current HIV epidemic. Hahn's team found that the Gombe chimp's strain of SIVcpz was quite different from both the west-central African SIV strains and the major HIV groups.
She said she believes the west-central chimps remain the ''most likely'' source of HIV.
SOURCE: Science 2002;295:465.

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