Chimpanzees can develop AIDS

Posted on March 9, 2011


As I spend more time learning about research carried out in the scientific world, I realise there are a wealth of stories that just never manage to penetrate the mainstream media.

The attitude of so many news editors is surprising blinkered and aloof, as I found out last year when I tried to pitch my piece about the chimpanzees in the Budongo Forest Reserve. In this particular case, the subject of possible extinction was clearly not significant enough for some of the newsroom fat controllers, who told me they’d already run a story on gorillas the week before.

A recent conference this year organised by the American Association for the Advancement of Science (AAAS) in Washington DC, brought together the great and the good to discuss their latest findings and theories. Among the guest speakers was Beatrice Hahn, professor of medicine and microbiology at the University of Alabama in Birmingham. As part of a talk – Disease without Borders – she spoke about her work understanding the pathogenicity and species-to-species transmission of immunodeficiency viruses.

Echo with her infant Emela in March 2006. Echo was infected with an HIV-related virus for at least four years before dying. (Copyright: Michael Wilson)

Until recently HIV, the virus that causes AIDS appeared to pose a serious health hazard primarily to humans; but Professor Hahn and her team  found that a similar strain of the disease – Simian Immunodeficiency Virus (SIV) –  found in some chimpanzees was also causing them to die, something that was previously not realised and came as a surprise.

These findings were published in 2009, but the British mainstream media hardly touched the subject. Almost three years on it’s now being mentioned after it was brought up at the recent US conference.

Professor Hahn told me: “Since 2000, our results show that the strain of SIV found in some Gombe chimps has a substantial negative impact on the health, reproduction and life-span of wild chimpanzees.” She estimates that a quarter of the 100 animals in Gombe now have the disease. It is of concern and it gives conservationists yet another worry in the struggle to save a species already at risk of extinction.

Human DNA is more than 98 per cent identical to chimpanzee DNA. There are at least 40 different types of SIV African primates but two of these crossed the species barrier to generate HIV-1 and HIV-2, the human form of the virus. HIV-1 currently infects approximately 42 million people worldwide.

Professor Hahn said: “Retrospectively you hit yourself on the head, because of course it makes sense that it could be pathogenic in chimpanzees. But you can’t generalise, each species is different. We looked at small groups of wild habituated chimpanzees and saw an increased risk to them that can cause an AIDS-like illness. At Gombe where we studied them, they are an ideal wild animal model for HIV; but this research is restricted because you can’t ask them to come to the clinic for a check up. We study them using non invasive methods.”

For years scientists believed all non human primates were resistant to SIV. Primates like the greater spot-nosed monkey (Cercopithecus nictitans) and red-capped mangbeys (Cercocebus torquatus) are the perfect hosts for the virus as it doesn’t affect them. But chimps in Gombe who’ve become infected by either eating these particular monkeys or being bitten are suffering the same consequences as humans. Their lives are being shortened by the virus.

The sick chimps are from a population of the chimp subspecies (Pan troglodytes schweinfurthii) that live in Gombe National Park in Tanzania. The Gombe study site established by the world renown primatologist, Dr Jane Goodall, has provided Professor Hahn and her team an area to monitor the infected apes at a distance. It’s provided an opportunity to look through databases detailing the parentage and history of dozens of animals and to be able to check for the virus in the droppings of present populations to compare infection rates.

The researchers found that infected chimpanzees in their study group were 10-16 times more likely to die than those who were uninfected. Infected females were less likely to give birth and infants born to infected mothers were unlikely to survive. The virus, they learned, was transmitted sexually and through mother’s milk. Over the nine-year study period, 10-20 percent of the 94 chimpanzees were infected at any one time. Although there have been mortalities, the main study community has managed to maintain its size.

There are still so many questions still unanswered but it’s hoped that with continued research, a better understanding of the virus will hopefully benefit both humans and chimpanzees.