CWD found near Wyoming's winter elk feeding grounds

Wyoming elk winter feeding grounds
Wyoming elk winter feeding grounds

Elk winter feeding grounds near Jackson Hole, Wyoming., Rawpixel, Carol M. Highsmith / Flickr cc

A female elk harvested as part of Grand Teton National Park's elk reduction program was confirmed positive for chronic wasting disease (CWD) on Dec 16, reports the Wyoming Game and Fish Department (WGFD). This is the first elk to test positive near the area's 23 winter elk feeding grounds, raising concern over the escalation of future transmissions.

"This is not going to be good, that's my gut feeling," WGFD Supervisor Hank Edwards told the Jackson Hole News & Guide. "How bad it's going to be? I don't know."

In 2018, a mule deer tested positive for CWD in the Grand Tetons, and other mule deer infections were reported near Pinedale (2016), Star Valley (2017), and in the Wyoming Range (2018), says the WGFD. Prior to this case, the farthest west an elk infection had been reported in Wyoming was in hunt unit 66, east of Cody, according to an Associated Press article.

The new CWD case comes after GWFD and its partnering federal agencies recently began a public collaborative effort to discuss the future management of elk feeding grounds in Wyoming, the department said.

CWD is a lethal prion disease among deer, elk, moose, and other members of the cervidae family that is transmitted through infected body fluids, antler velvet, and prions shed in the environment.

According to the News & Guide story, a 2017 study predicts CWD will take 5 years to reach 10% prevalence within the Jackson elk herd. The same study says population decline will occur when female elk have a viral prevalence of 7%; however, the upper bound could be as high as 23%.

While these values provide potential benchmarks, the researchers note that the model does not factor in current herd reduction goals and hunting.

Increased surveillance for feeding program

Because of CWD's growing threat, this year Jackson Hole's century-old feeding program will have increased surveillance, and any elk exhibiting symptoms of CWD will be quickly culled and removed from the area, according to the News & Guide article. Future plans to change the feeding program are being discussed, but changes will be incremental.

Continuing the park's feeding program has already been under debate: Each year, 20,000 elk pass through the feeding grounds, making it a potential transmission hot spot.

Besides the cervid-to-cervid contact, a 2004 Emerging Infectious Diseases study suggests infectious prions can remain in the environment for at least 2 years, and the Virginia Department of Wildlife Resources says they probably can remain between 16 months and 4 years

In Wisconsin, one of the states with a large burden of CWD, the state's Department of Natural Resources (DNR) has required stricter management around cervid feeding. The department banned baiting and feeding deer in 52 of 72 counties (72.2%); CWD cases have been found in wild deer across 31 counties (43.0%) since 1991.

Unusual hot spot in southeast Minnesota

Since CWD's discovery in the late 1960s, surveillance has increased to track the disease, but a recent hot spot in Minnesota reminds researchers there is still much unknown.

For the past three hunting seasons, a 90-acre private property near La Crescent has had five white-tail deer test positive after being harvested or found dead, reports the Minneapolis Star Tribune, yet no other positive cases among wild deer have been found in Houston County (approximately 569 square miles). A 5-mile sampling radius around the property—which included 900 tests—found no other cases, either.

One possible explanation is that someone dumped infected deer carcasses there years ago, but the family had not been notified or discovered any evidence to support this, according to the story. Minnesota Department of Natural Resource officials investigated old salt deposits, ponds, and depressions, with no leads. A past CWD outbreak about 9 miles north was also a potential cause, but no surveillance over the past years has found any connection.

The family has continued to follow Centers for Disease Control and Prevention guidelines and has not eaten any venison from CWD-positive specimens. Although no evidence conclusively indicates the disease can be transmitted from cervids to humans, public health officials are closely monitoring the situation because bovine spongiform encephalitis ("mad cow" disease), for example, has made the jump. The CDC notes the data on CWD are insufficient to draw conclusions, citing studies with differing results about transmission to macaques.

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