Several people working or living around monkeys in South and Southeast Asian countries have been infected with simian foamy virus (SFV), according to a new study.
Led by University of Washington scientists, the study gives force to the suggestion that Asia, where interaction between people and monkeys is common and widespread, could be an important setting for future primate-to-human viral transmission.
A research article in the journal Emerging Infectious Disease says, though SFV has not been found to cause any human disease to date, it is a slow-acting retrovirus and thus it may take many years before scientists determine the effects of infection.
It is believed that a similar process occurred with HIV, which probably originated as a virus in non-human primates in Africa.
During the study, the researchers visited several countries in Asia, where they interviewed and tested about 300 people who lived or worked closely with any one of several species of small-bodied monkeys called macaques.
Eight of the participants tested positive for SFV, they said.
One of such persons lived in an urban area in Bangladesh that had a large monkey population, while two other people lived near a monkey temple in Thailand.
The infected population also included a farmer in Thailand who had trained monkeys to help him harvest coconuts.
Monkey temples are places of religious worship that have become refuges for populations of primates.
UW researcher Dr. Lisa Jones-Engel, who led multiple studies in Asia, says that some Asian countries are prime areas for viral transmission between monkeys and humans because of the huge populations of both, and the widespread interaction between the species.
She points out that Asian people are in close contact with monkeys, who are kept as pets in cities, religious temples, open-air markets, street performances, nature preserves, hunting areas, zoos, and even homes.
"So much of the focus on this issue has been in Africa, but there, the interface between humans and other primates is decreasing. The intensity of bush meat hunting and infectious diseases have taken a huge toll on primate populations there. Individuals in Africa who are interacting with other primates are often very isolated from other humans - they live in small, rural villages, which limits the potential spread of pathogens," said Jones-Engel, a senior research scientist in the Division of International Programs at the UW's Washington National Primate Research Center.
The researchers says that the rapid expansion of cities and the decline of wild habitats have driven many monkey populations into urban areas, where they interact more closely with human populations.
They say that rhesus macaques and other species of monkeys are very adaptable to new habitats, unlike great apes like chimpanzees or gorillas.
"Some macaque species thrive in human-altered environments, given the tolerance of the local people," said Dr. Gregory Engel, clinical assistant professor of family medicine at the UW and a co-author on this study.
The new findings support the notion that viral transmission could occur in any one of many settings in Asia, from religious temples to urban areas, and that the issue could affect many different people, from temple workers to pet owners.
"This is a heterogeneous sample - subjects reported contact with primates in a variety of contexts. It seems that some of these contexts are going to be very important, but they haven't been studied much. Zoo workers and bush meat hunters have been typically considered at the highest risk for viral transmission, but none of the zoo workers or hunters in our sample tested positive for SFV," said Gregory Engel, who is also a physician at Swedish Medical Center in Seattle.
The researchers suggest that better disease monitoring and further study of monkey-human interaction may help reduce the risks associated with viral transmission.
They also say that people living, working, or visiting areas of Asia with monkey populations can also reduce their risk by limiting their close contact with the animals.
For tourists, their suggestion is to wear long pants around monkeys, and not try to feed, pet or hold the animals.