Introduced to amuse tourists, the monkeys pose a public health risk, scientists warn. In the 1930s and 40s, the captain of a glass-bottom boat released a dozen or so rhesus macaques on an island in Floridas Silver River, which snakes through Marion county in the center of the state. The idea was that the monkeys, native to Asia, would be a laugh for tourists passing by. But it seems the monkeys may be the ones to get the last laugh. For one thing, macaques are excellent swimmers and promptly got themselves off the island. In the decades since, their population has exploded to upward of 800 in the surrounding Silver Spring State Park and nearby Ocala National Forest. A new study, out in the February issue of Emerging Infectious Diseases, reveals that the population is also spreading a dangerous type of herpes. The virus— macacine herpesvirus 1 (McHV-1), aka herpes B or monkey B virus—is common and causes mild infections in macaques. But in humans, it can lead to severe, often lethal, illnesses. The study authors, led by Samantha Wisely of the University of Florida, Gainesville, concluded that the monkeys must be considered a public health concern and "adequate public health measures should be taken." For the study, Wisely and her colleagues analyzed blood data collected from 317 monkeys by private trappers between 2000 and 2012. The researchers also examined 121 oral swabs, 23 fecal samples, and 10 soil samples that they collected between 2015 and 2016. Based on the blood tests, the researchers estimated that about 25 percent of the population carried the virus annually between 2000 and 2012. From the saliva swabs, about four to 14 percent of the infected were actively shedding the virus during the stressful fall mating season of 2015. Like the herpes viruses that infect humans (HSV-1 and HSV-2), McHV-1 infects nerves and can go dormant. If the animals are stressed or have a weakened immune system, the virus can reemerge and seep from the mucus membranes of the mouth, nose, or genitals. This is similar to how HSV-1 and HSV-2 periodically erupt in humans, typically around the mouth and genitals, respectively. But when McHV-1 gets into humans, it can cause serious problems in the central nervous system. The virus can be spread to humans by monkey bites and scratches, as well as infectious fluids/feces getting splashed into the eyes ( which happened once). Depending on the route of infection and the number of virus particles transferred, the infection in humans can progress from flu-like symptoms to neurological problems. These include double vision, lack of voluntary control of muscle movements, and paralysis. If neurological symptoms develop, the infected person will likely die even with antiviral therapy. Since McHV-1 was identified in 1932, researchers have only documented 50 cases of human infections, all from captive macaques. Of those cases, 21 resulted in death. So far, there have been no documented cases of humans getting McHV-1 from wild monkeys, in Florida or elsewhere. This, the researchers speculate, may be because captive monkeys are more stressed and therefore shed more virus, and/or that humans have contracted McHV-1 from wild monkeys but those cases were unreported or misdiagnosed. Wisely and colleagues say the threat of transmission in Florida is real. They note that between 1977 and 1984, the Florida Fish and Wildlife Commission recorded at least 23 cases of monkeys biting humans in the Silver Spring State Park. After private trapping collected hundreds of monkeys between 2000 and 2012, the population is lower now, with an estimated 175 monkeys in Silver Spring State Park in 2015. Still, the researchers note, the primates have "high reproductive capacity" and are accustomed to getting close to and interacting with humans. The bottom line is that "these macaques can shed McHV-1, putting humans at risk for exposure to this potentially fatal pathogen," the researchers conclude. Emerging Infectious Diseases, 2017. DOI: 10.3201/eid2402.171439 ( About DOIs).
If you see a monkey in Florida, dont touch it. It seems like pretty basic advice, especially now that scientists have found that more than a quarter of these adorable, feral invaders carry the deadly herpes B virus. Though at least 25 percent of the population carries the virus — which causes mild disease in macaques, but can be deadly to humans — fewer were actually infectious. The virus lies dormant in nerves in between flare-ups, similar to cold sores in humans. Between 4 and 14 percent of the monkeys released the virus in their spit during their fall breeding season, researchers report in the journal Emerging Infectious Diseases. And the wild monkeys poop turned out to be pristine — at least, as far as herpes B was concerned. The headlines have already taken off about this, but theres really a lot we still dont know about herpes B in wild monkeys, says study author Samantha Wisely, a wildlife biologist at the University of Florida. The virus is what she calls low-risk, but high-consequence — like rabies, she says. Theres really a low risk of you getting it, but if you get it, there are going to be very high consequences. Floridas feral rhesus macaque monkeys are native to southern and eastern Asia, and are particularly adorable and effective invaders. They got to the state the usual way — by hitching a ride with misguided humans who thought the cute little creatures could draw tourists. Between 1930 and 1950, a dozen rhesus macaques were introduced to central Floridas Silver Springs State Park, where they multiplied. By 2012, 1,000 rhesus macaques had been trapped and removed before public outcry stopped the control effort. (People sure love furry, feral, ecosystem-endangering mammals.) At last count in 2015, some 175 macaques were living in Silver Springs State Park. Macaques can become a nuisance in new environments. They destroy crops, contaminate water, and chow down on native birds eggs and chicks. They also can carry herpes B, which usually doesnt do anything to the monkeys, but sometimes causes cold sores, mouth ulcers, and eye irritation. After the initial infection, the virus hides out in the animals nerves, flaring up only when the monkey gets sick or stressed. When it does, the monkey can become contagious, secreting the virus in its spit, pee, or poop. Thats how the virus can spread to people. In humans, herpes B causes a devastating brain disease that the CDC says is deadly about 70 percent of the time — especially without treatment. The weird thing is that the reported cases of herpes B are mainly in lab workers or veterinarians who caught the virus from a bite or exposure to infected bodily fluids at work. None have been reported in people who were bitten by a wild monkey, Wisely says. (That happened at least 23 times near Silver Springs State Park between 1977 and 1984.) The wild monkeys also poop everywhere, Wisely says, so there could be plenty of chances for exposure that way. To be honest with you, we found feces on childrens slides, and in the playground, she says. To find out exactly how common the herpes B virus was in Floridas feral monkeys, Wiselys team analyzed blood tests collected by trappers trying to control the population. They found that roughly 25 percent of the monkeys contained antibodies to the virus, which was probably an underestimate, Wisely says. Trappers tended to target younger monkeys who probably hadnt been exposed to the virus yet. If the researchers only analyzed the adults, infections became much more common: 75 percent of the older monkeys they tested carried the virus. Carrying the virus doesnt necessarily mean a monkey was infectious, so the team also tested the monkeys spit a couple times during 2015. To get the spit, they dipped cotton swabs in sugar water, and lobbed them at the monkeys. It was kind of a targeted toss at particular monkeys, Wisely says. And then they chew on it for awhile and go, Wait, this isnt food, and then spit it out. Since the researchers couldnt always track a spitball back to the monkey who made it, the exact numbers are a little vague. But they estimate that between 4 and 14 percent of the monkeys shed the virus during the breeding season, which is stressful for both the males and the females. They didnt detect the virus in the spit at any of the other times they checked, or in the fresh feces they sampled. So how worried should people actually be about those herpes B-infected monkeys in Florida? Not terrified, but cautious, Wisely says. The Florida Fish and Wildlife Commission said in a statement that it supports active management to remove these threats. In the meantime, Wisely says, if you are tempted to feed, snuggle, or attempt a selfie with the wildlife, just dont. It doesnt do the wildlife any good, Wisely says, and it doesnt do you any good.