Little-known retrovirus jumps from primate to man

The monkey temples on the resort island of Bali are a perfect photo opportunity for tourists feeding bananas to man’s closest relative, but most visitors are likely unaware they’re at risk of contracting a little-known retrovirus recently found to jump from primates to people in Asia.

Simian foamy virus, called SFV, has not been known to cause disease, but a recent study triggers questions about its potential to possibly sicken people in the future just as scientists believe the HIV virus evolved decades after it jumped species.

In a study conducted at a popular monkey temple in Bali, lead researcher Lisa Jones-Engel of the University of Washington’s National Primate Research Centre in Seattle sampled 82 people working in or near the Sangeh temple just north of Denpasar. One farmer, who was bitten and scratched by macaques, tested positive for SFV, becoming Asia’s first known case.

“This is really a marker,” Jones-Engel said in a telephone interview.

“The virus itself doesn’t give us complications right now, but it speaks to the context and the mechanisms for transmission.”

She said SFV is commonly found in many primates—89,5% of the 38 macaques tested at the monkey temple were positive—but has not been known to cause disease in animals. However, little research has been conducted on how widespread it is among humans or its long-term effects.
So far, only about 40 people are known to carry the virus, including African bushmeat hunters and zoo and lab workers in North America.

The authors suspect many more people have been infected in Asia where humans and primates come in close contact. About 700 000 tourists visit four monkey temples just in Bali each year. Of those, an estimated 35 000 visitors are bitten, according to the study in last month’s Emerging Infectious Diseases, a journal of the United States Centres for Disease Control and Prevention.

About 45 monkey temples exist on Bali, and similar refuges are scattered across Asia in Hindu and Buddhist places of worship.

“We’re talking about a significant number of people, and we’re talking about people who then leave the next day and travel ... around the world,” said Gregory Engel, co-author of the study and a doctor at the Swedish/Providence Hospital in Seattle.

The authors say people who have been bitten or scratched by monkeys should not become alarmed, especially since there is no easy way to test for the virus in humans. However, scientists question how SFV could react when mixed with HIV, tuberculosis or other human diseases.

It’s also unclear how SFV could behave in humans over time. SFV is genetically different from the virus in primates that’s believed to have emerged as HIV, but the authors say there’s no guarantee SFV won’t alter and eventually become harmful to humans.

The virus that causes HIV/Aids is believed to have passed from primates to people in Africa decades before it began sickening people in the 1980s. There is no evidence SFV has been transmitted among people.

William Switzer of the CDC’s Division of HIV/Aids Prevention said more studies are needed on how widespread SFV is and on the likelihood of human-to-human transmission of cross-species infections.

“The public health implications of SFV in humans are also not fully known,” said Switzer, who has researched SFV but did not take part in this study.

The researchers say SFV may never become harmful to humans, but could be an indicator that other viruses may jump more easily from monkey to man.

Asia is familiar with cross-species infection from acute respiratory syndrome, or Sars, which is believed to have first jumped from animals to people in China; it killed nearly 800 people worldwide. The region is now battling avian flu in which poultry has infected humans, killing at least 60 people since 2003.

“We’ve opened up a whole new continent where we need to seriously consider that there are viruses and pathogens that can be communicated between primates and humans,” Engel said of the first SFV case found in Asia.

“We’re talking about billions of people and millions of primates and the possibility of unknown pathogens being out there and a very real mechanism whereby those pathogens can flow.”

The authors say people can still visit monkey temples, but close contact should be avoided. They advise wearing pants, not taking food inside and never coming between a mother monkey and her young.

The monkeys in Bali are conditioned to approach people for food and can become aggressive. Last month at the popular Monkey Forest in Ubud, monkeys casually jumped on tourists’ backs and grabbed for bananas. One primate lunged for a woman trying to retrieve a camera bag it was pilfering.

“Here in the States or in Europe, you don’t let your kid walk up to a wild animal generally and feed it—you move your child away from the raccoon if it’s rummaging through your garbage,” said Jones-Engel.

“But monkeys are so like us, they’re so endearing ... you’re momentarily befuddled. You lose a certain amount of common sense.” - Sapa-AP

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