Rare, deadly "zombie" deer disease found in Yellowstone, officials say

LI COHEN
November 17, 2023 

NPS/Neal Herbert


A rare "zombie" disease that causes deer to excessively drool, droop their ears and become reluctant to move before eventually killing them has been detected in Yellowstone National Park for the first time, officials say. Once established, officials say there is "no effective way to eradicate" the fatal illness, called chronic wasting disease.

National Park Service officials said earlier this week the disease was found in a dead adult mule deer found near Yellowstone Lake. The deer had originally been captured in Cody, Wyoming, by the state's Game and Fish Department in March as part of a population study, and according to a GPS collar that had been placed on the animal, officials said it died around mid-October.

"This is the first confirmed positive detection of the disease in Yellowstone National Park," a press release from the government agency said, adding they conducted "multiple diagnostics tests" to confirm its presence.

What is "zombie" deer disease, or chronic wasting disease?

Deer, elk, reindeer and moose can all be affected by chronic wasting disease, which has been found in North America, Norway and South Korea, according to the CDC. The agency says that it can take more than a year for animals to show symptoms and that some animals may die without ever fully developing the prion disease, a "rare progressive neurodegenerative disorder" that impacts prion proteins mostly found in brains.

Chronic wasting disease, sometimes called "zombie deer disease" according to Wyoming Public Media, impacts the central nervous system of animals. When animals do show symptoms, the Wyoming Game and Fish Department says they will typically lose weight, be reluctant to move, excessively salivate, will drink and urinate more frequently, their ears will droops, and eventually, they'll die.

"The majority of CWD positive animals that are harvested appear completely normal and healthy," the Wyoming agency says.

Typically, chronic wasting disease is transmitted through bodily fluids and waste, including saliva, urine, feces and even carcasses, WGFD says. Animals can also become infected if their feed or pasture is contaminated with the prions carrying it.

As of now, the National Park Service says "there is no effective strategy to eradicate" the disease once it has been established. The service said it will now work with other agencies to identify areas that are most at-risk for its spread and will increase monitoring and sample testing. Yellowstone is also working on revising its surveillance plan that was last reviewed in 2021, and is hoping to complete the revision next year.


Can humans get chronic wasting disease?

The CDC says that "there have been no reported cases of CWD infection in people."

However, there is some concern that a risk still exists. Some studies have suggested chronic wasting disease is a risk to monkeys that eat infected animal meat or come in contact with infected animal brains or bodily fluids.

"Since 1997, the World Health Organization has recommended that it is important to keep the agents of all known prion diseases from entering the human food chain," the CDC says.

The agency said additional studies are also being conducted to find out if prion diseases such as CWD can occur at a higher rate in people more at risk of coming into contact with an infected animal or its meat.

"Because of the long time it takes before any symptoms of disease appear, scientists expect the study to take many years before they will determine what the risk, if any, of CWD is to people," the agency said.