Chronic wasting disease confirmed in Yellowstone National Park for first time

Disease was first identified in Colorado, Wyoming in the 1960s and ‘70s but has spread to at least 24 states, as well as other countries

By: - November 16, 2023 10:34 am
mule deer buck travels through the wilderness near Montana's Garnet Hill Loop

A mule deer buck travels through the wilderness near Montana’s Garnet Hill Loop. (Neal Herbert/National Park Service)

Chronic wasting disease has been confirmed for the first time in Yellowstone National Park in a mule deer found dead near Yellowstone Lake, park officials said Tuesday.

The mule deer, an adult buck, died mid-October after making its way to the southeastern part of the national park during the past seven months, a Yellowstone National Park spokesperson said. The deer had been captured and collared by Wyoming Game and Fish Department crews in March as part of a population study.

Park spokesperson Morgan Warthin said multiple tests confirmed the deer had the disease, which affects the cervid family of white-tailed and mule deer, elk, and moose and is 100% fatal. There is no vaccine or cure for chronic wasting disease.

The disease is caused by a malformed prion protein, which accumulates in the animals’ brains and other tissue and leads to neurological and behavioral changes, then emaciation and death. The proteins are shed by live animals through saliva, urine, feces, blood, and antler velvet and spread through direct contact with other cervids. The prions can also last in the environment for up to decades, according to the National Park Service.

Chronic wasting disease first identified in the West, including high case counts in Wyoming

The disease was first identified in Colorado and Wyoming in the 1960s and ‘70s but has spread to at least 24 states, two provinces in Canada, South Korea, and some European countries.

It was first identified in Montana in 2017 but has spread across most of Wyoming during the past four decades. Yellowstone National Park says about 10-15% of mule deer that live near Cody, Wyoming, and migrate into the southeastern part of the park during the summer are estimated to have CWD.

Warthin said the park would revise its 2021 Chronic Wasting Disease Surveillance Plan after the detection of the disease and would complete the revision next year. She said the park will also increase its collaboration and sharing of information with Wyoming Game and Fish to look at areas of the park that are at an increased risk for the disease, bolster monitoring for the disease within the park, and increase investigations of animal carcasses and testing.

So far this year in Montana, just 3.5% of more than 2,400 animals tested in Montana for CWD have tested positive – all of them either white-tailed or mule deer, and most of them killed by hunters.

The largest number of samples (213) have been taken out of hunting district 322 in the Ruby Valley west of the park, which has been a hot spot for the disease during the past six years of testing. For several winters, Montana Fish, Wildlife and Parks has conducted a chronic wasting disease management hunt in the district for white-tailed deer to try to better manage the disease in the area. During the 2020-21 hunt, about 25% of the deer taken during the hunt tested positive for the disease.

Montana Fish, Wildlife and Parks map shows where samples have been collected in the state for chronic wasting disease
This Montana Fish, Wildlife and Parks map shows where samples have been collected in the state for chronic wasting disease over the past six years, and where positive cases have been discovered. (Courtesy of Montana Fish, Wildlife and Parks)

The state aims to keep the prevalence of the disease in the state’s wild cervid population below 5%, and during 6.5 years of monitoring, samples have turned up a positive rate of 3%.

The highest concentrations of the disease over the past six years have been found in the Ruby Valley, the Kootenai National Forest area around Libby, and along the north-central and northeastern borders with Canada.

Montana Fish, Wildlife and Parks Region 3 spokesperson Morgan Jacobsen said there have been very few detections of the disease in the hunting districts that border Yellowstone. He called the discovery of the disease in the park a “data point of interest,” but said it does not change the agency’s surveillance strategies for the year.

“We’re going to continue our monitoring and communication with the park and continue to work with hunters as the primary management tool for CWD in Montana,” Jacobsen said.

Fish, Wildlife and Parks has Priority Surveillance Areas for the disease in north-central, southwestern, south-central and eastern Montana, where they want hunters to voluntarily submit their harvests for chronic wasting disease sampling. But hunters statewide can submit animals for sampling at stations across the state.

The state covers the cost of testing for hunter-harvested animals. Hunters are asked to leave 2-4 inches of the animals neck to be sure the animal’s lymph nodes are present for testing. All carcasses have to be disposed of in class II landfills to help prevent the spread of the disease in Montana.

People are advised not to eat animals with the disease out of precaution and to report sick animals to Fish, Wildlife and Parks in Montana and to National Park Service employees inside Yellowstone National Park so they can diagnose the animal.

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Blair Miller
Blair Miller

Blair Miller is a reporter for The Daily Montanan based in Helena who primarily covers government, climate and courts. He's been a journalist for more than 12 years, previously based in Denver, Albuquerque and mid-Missouri.