Monkeys and apes are considered edible game in many parts of Africa. As people from these regions have emigrated to other parts of the world, some have retained their love of this and other types of bushmeat. A new study now finds that meat from nonhuman primates — from chimps to monkeys — can host potentially dangerous viruses. Tested samples were confiscated at U.S. airports.
Veterinarian Kristine Smith of EcoHealth Alliance, a wildlife conservation and health group in New York City, led the new analysis, published Jan. 10 in PLoS ONE. Her team analyzed primate and rodent bushmeat that had been serendipitously caught at New York’s John F. Kennedy Airport and eventually at four others (in Philadelphia, Washington, Atlanta and Houston) over the past five years.
“These products ranged from raw and bloody to well smoked,” Smith says, “and we found virus even in the well-smoked pieces.” That’s a big concern, she and her coauthors maintain, since nearly 75 percent of emerging infectious diseases in humans comes from animals, mostly wildlife.
No one knows how much bushmeat enters the United States, although the new study points to one European account that estimated Air France planes alone ferry more than 270 tons of bushmeat into Charles de Gaulle Airport, in Paris, each year.
In the United States, most such contraband food is promptly incinerated, Smith notes. But in a few cases, some bushmeat had been stored at between -20 and -80 °Celsius. This provided Smith’s group portions of 44 rats and primates to screen for germs. The researchers focused on wildlife pathogens with a known potential to infect people. And although the 35 rats hosted none of the germs they scouted for (including anthrax, coronaviruses and more), the nine primates did show viral contamination — sometimes with multiple types of germs.
The good news: This survey turned up none of the infectious agents that over the years have given rise to HIV/AIDS — simian immunodeficiency viruses — and to human T-lymphotropic viruses.
But Smith is not sanguine about these non-detects. Both types of viruses are so common in African primates that she had expected to see them in the bushmeat. She now attributes her group’s failure to find them to the few samples available for testing.
The new analysis did turn up substantial contamination of the non-human primates with herpesviruses — ones known as cytomegalovirus and lymphocryptovirus. Cytomegalovirus normally causes few symptoms in people except when infection occurs during fetal development or among individuals with a compromised immune system. Lymphocryptoviruses includes a family of germs (the best-known being Epstein-Barr virus) that have been associated with serious infections and tumors in people.
Most Americans will find simian foamy virus the most curious germ identified in the bushmeat samples. A retrovirus, it belongs to the same overarching family of disease-causing agents as HIV and human T-lymphotropic viruses (which has been linked with neurological impairments and blood cancers). Both HIV and HTLV appear to have arisen when infection with largely benign primate versions of the viruses didn’t prove so benign in our species.
Retroviruses tend to become lifelong infections that develop slowly and may be hard to spread. In the case of simian foamy virus, William Switzer of the Centers for Disease Control and Prevention has been following groups of people that picked up foamy virus infections in the United States and Africa from monkeys and apes that they had hunted, butchered, eaten or had frequent contact with (such as vets, zookeepers or pet owners).
In more than a dozen years of followup, no one with simian foamy virus has yet exhibited disease symptoms — which could be taken as a sign that these bugs aren’t very dangerous, says Switzer, a coauthor of the new paper. But he cautions that this is only a suspicion as infected patients may not have been followed long enough yet to identify any slowly developing disease or immune impairment.
“Other retroviral diseases like HTLV can take decades to cause disease,” including leukemia, lymphoma, inflammatory diseases such as arthritis and potentially debilitating neurologic disorders affecting the spinal cord (such as tropical spastic paraparesis), Switzer points out.
Moreover, human foamy virus infections have only been followed in largely healthy individuals. That may downplay true risks if this virus does the most damage in people who are sick with other illnesses — or who were born with genes that can’t effectively manage effects of this virus.
Until simian foamy virus can be demonstrated to be benign, Switzer says it pays to work toward limiting its spread. And that includes screening blood donations. His team has already identified U.S. patients who had donated blood prior to being diagnosed with foamy virus. And in lab studies using infected macaque monkeys, he observes, “it’s been shown that this virus can be infective and spread from animal to animal via blood donation.”
“The pathogens we found in this study are not something I think everyone should be hugely alarmed about,” Smith says — “but they are very concerning.”
Before conducting the new pilot study, scientists had volunteered that confiscated bushmeat will be so degraded that geneticists will never find evidence of viruses because the germs' DNA will have been destroyed. In fact, Smith now points out, viruses and their genetic material survived just fine.
Her group, which was led by CDC scientists, now wants to test the infectiousness of such viruses and to broaden the search for disease contamination of bushmeat arriving at ports throughout the United States.
K.M. Smith, et al. Zoonotic viruses associated with illegally imported wildlife products. PLoS ONE, Vol. 7, Jan. 10, 2012. doi: 10.1371/journal.pone.0029505
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