Almost 175 free-roaming rhesus macaques (Macaca mulatta) inhabit the park, descended from a population of around a dozen animals that were brought in from an unknown source in 2 separate introduction events in the 1930s to increase tourism.
By the 1980s, the population had grown to a peak of about 400 animals and spread into adjacent forests along the Ocklawaha River. The rhesus macaque is an invasive species in the United States with a high reproductive capacity, the ability to spread in geographic distribution, and the potential to threaten native fauna with extinction, according to the CDC.
Researchers from the Centers for Disease Control and Prevention (CDC) report that about 25 percent of the monkeys carry macacine herpesvirus 1 (McHV-1), also known as herpes B virus, which causes only mild symptoms, if any, in monkeys but can be deadly in people.
The researchers found that at least 25 percent of the monkeys carry the virus, which can cause mild disease in macaques but can be deadly to humans. About 14 percent of the macaques shed the virus orally during the fall mating season. Researchers did not observe viral shedding during the spring or summer or from fecal samples.
“The headlines have already taken off about this, but there’s really a lot we still don’t 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. “There’s really a low risk of you getting it, but if you get it, there are going to be very high consequences.”
Human cases of Herpes B virus are extremely rare, with only 50 documented cases worldwide. There have been no known transmissions of it to people from wild rhesus macaques in Florida or elsewhere.
But even so, the results of the study prompted researchers from the universities of Florida and Washington to warn Florida’s wildlife agency that the infected monkeys should be considered a public health concern.
And the state is taking this very seriously. “Without management action, the presence and continued expansion of non-native rhesus macaques in Florida can result in serious human health and safety risks including human injury and transmission of disease,” Thomas Eason, assistant executive director of the Florida Fish and Wildlife Conservation Commission, said in a statement.
Eason did not get specific on what measures the department was considering, but a spokesperson said the commission supports ridding the state of the invasive creatures. “The commission supports the removal of these monkeys from the environment to help reduce the threat they pose. This can be done in a variety of ways,” spokeswoman Carli Segelson said in an email.
At least 23 visitors to Silver Springs State Park were bitten by macaques between 1977 and 1984, according to Wisely. And she says the wild monkeys’ poop everywhere, so exposure is increased. “To be honest with you, we found feces on children’s slides, and in the playground,” she says.
The CDC’s findings were reported in the February 2018 issue of the journal, Emerging Infectious Diseases, entitled Macacine Herpesvirus 1 Antibody Prevalence and DNA Shedding among Invasive Rhesus Macaques, Silver Springs State Park, Florida, USA