WASHINGTON – It sounds like a plot out of “The Walking Dead.”
Deer contract a mysterious disease. Symptoms include vacant stares, thick saliva, exposes ribs, drooping heads – but no behavior outside the normal range of deer activity. They can live two years like that. Then, one day, they snap, becoming overly aggressive – thus the “zombie” caricature – before dying.
The big worry is that people have eaten the meat of infected deer, raising fears the plague could cross over species.
The real name for what is being called “zombie deer disease” is “chronic wasting disease.” It was first observed in 1967 in Fort Collins, Colorado, and has infected herds in 24 states and Canada, South Korea and Norway, according to the Centers for Disease Control and Prevention.
Chronic wasting disease, or CWD, passes from animal to animal through prions, misfolded proteins that cause other proteins to misfold around them. Different prion diseases tend to only harm certain species, but can evolve to overcome those limitations.
The following states have reported the disease: Arkansas, Colorado, Illinois, Iowa, Kansas, Maryland, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Mexico, New York, North Dakota, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Virginia, West Virginia, Wisconsin and Wyoming. A whopping 42 counties in Nebraska reported CWD as of Feb. 19.
In some herds, as many as half of the animals carry prions.
But direct contact isn’t the only way prions are transmitted. Sick animals and cadavers can spread prions through plants and soil, which could be coated with deformed proteins for years, perhaps even decades.
While there have been no reported human illnesses due to the disease, and scientists don’t have conclusive evidence that infected meat has ever harmed people, wildlife officials in Colorado and Pennsylvania are pushing for hunting regulations just to be safe.
And there’s more reason for concern.
A Canadian study has added to concern that consumption of infected deer could spread the disease to other species – including people. A prominent prion researcher, Stefanie Czub of the Canadian Food Inspection Agency, found three out of five monkeys fed infected meat tested positive for chronic wasting disease.
In the research, 18 macaque monkeys were exposed to CED in a variety of ways – injection of the material into the brain, through contact with the skin and by feeding them infected meat. It’s reported to be the first time the disease has been spread to primates through consumption of deer meat.
“The assumption was for the longest time that chronic wasting disease was not a threat to human health,” said Czub. “But with the new data it seems we need to revisit this view to some degree.”
The research was funded by the Alberta Prion Research Institute at the University of Calgary and began in 2009.
Prions were behind “mad cow disease.” According to the Food and Drug Administration, 231 people died from eating beef infected with “mad cow disease.”
Mark Zabel, associate director at Colorado State University’s Prion Research Center, said prions involved in the “zombie disease,” which scientists have only known about for 50 years, are probably still evolving. Zabel believes the only way to get rid of CWD prions is to set controlled fires.
According to Michael Miller, senior wildlife veterinarian for Colorado Parks and Wildlife, mule deer infection more than tripled toward the end of 2017, and CWD continues to be prevalent in Colorado.
“What we’ve seen over the last few decades is that it’s slowly spreading in wild deer populations,” said Peter Larsen, an assistant professor in veterinary sciences at the University of Minnesota. It’s also spreading among captive deer, elk, and reindeer, which are transported around the country and overseas to hunting ranches, petting zoos, and Christmas-themed farms. That’s how the disease ended up in South Korea, Larsen explained.
On March 13, 2005, a fire company in Oneida County, New York, fed the meat of a deer that tested positive for chronic wasting disease to 200 to 250 people. The company didn’t know the meat was from a diseased deer. Lab tests for one of the deer served came back later — positive for CWD.
Over time, the Oneida County Health Department monitored the group’s health through a surveillance project. About 80 people who ate the venison agreed to participate. Together with the State University of New York-Binghamton, health experts checked in with the group over the course of six years to see whether they developed any unusual symptoms.
In a study published in the peer-reviewed medical journal Public Health, researchers found the group had “no significant changes in health conditions,” though they did report eating less venison after the whole ordeal. Otherwise, observed conditions, including vision loss, heart disease, type 2 diabetes, weight changes, hypertension and arthritis, were all credited to old age.