Chronic wasting disease continued to spread and increase in prevalence in 2024, according to DNR data.

Twenty-three years after the first detections were reported, chronic wasting disease continues to spread geographically and increase in prevalence in Wisconsin’s white-tailed deer herd, according to data from the Department of Natural Resources.

In the last three weeks the DNR announced CWD findings in wild deer in two new counties, Chippewa and Menominee. The agency now classifies 64 of the state’s 72 counties as “CWD-affected.”

And 10.4% of the 16,321 deer tested in 2024 were CWD-positive, the highest statewide rate since surveillance for the fatal deer disease began in 1999.

Although the CWD testing is conducted on deer submitted voluntarily by hunters and not part of a controlled study, wildlife health experts say such an increasing prevalence rate is to be expected with the disease.

When assessed by county, the highest rate in 2024 was in Richland County, where 33% of 1,301 samples were CWD-positive, followed by Sauk (32% in 815 samples), Iowa (26% in 664) and Dane (18% in 851).

Chronic wasting disease is a prion disease that affects white-tailed deer, mule deer, elk, moose and reindeer, according to the Centers for Disease Control. It has been found in the United States, Canada, Norway, Finland and Sweden. Imported cases have also been reported in South Korea.

First recognized in a Colorado animal research facility in the late 1960s, CWD has now been identified in 32 states, according to the CDC.

The disease has not been documented to cause illness in humans or livestock. However health experts including at the CDC recommend meat from CWD-positive deer not be consumed by humans.

Wisconsin was the first state east of the Mississippi River to have CWD-positive deer. The first CWD detections in Wisconsin were reported in 2002 both in wild deer near Mt. Horeb and in farmed deer at a facility in Portage County.

After a period of aggressive tactics such as the use of sharp-shooters in an effort to eradicate the disease in wild deer, the DNR adopted a strategy of testing and monitoring.

Hunters in Wisconsin can submit deer for CWD testing by the state; the process is voluntary and no fee is charged.

Over the last 25 years the DNR has documented a continued geographical spread of the disease, underscored by the announcements in the last month of CWD-positive wild deer in two additional counties.

The disease can spread through infected saliva, feces, blood or in contaminated soil and other substrates, according to the CDC. There is no known treatment or vaccine.

It may take more than a year before an infected animal develops symptoms, which can include drastic weight loss (wasting), stumbling, listlessness and other neurologic symptoms, according to the CDC.

It’s expected the disease will eventually be found in all 72 Wisconsin counties.

The disease has been linked to population level declines in mule deer in a Wyoming herd. It’s not yet known whether it will lead to a reduction in the deer population in Wisconsin whitetails. A DNR study on deer, CWD and predators in southern Wisconsin is expected to release results this year.

The 10.4% CWD-positive deer tested statewide in 2024 compares to: In 2023, 17,343 deer tested and 1,587 (9.2%) CWD-positive; 2022, 17,207 and 1,492 (8.7%); 2021, 17,149 and 1,327 (7.7%); 2020, 18,917 and 1,578 (8.3%); 2019, 19,368 and 1,338 (6.9%); and 2018, 17,216 and 1,064 (6.2%).

For additional perspective, the percent positive CWD detections were 5.3% in 2013. 1.5% in 2008, 0.8% in 2003 and 0.1% in samples pooled from 1999 through 2002, the first years of CWD testing.

The CWD-positive deer in Menominee County was a 2-year-old buck taken by a hunter. The finding won’t change regulations in Menominee County, which were under a baiting and feeding ban put in place by Menominee Indian Reservation.

It also won’t affect the three-year baiting and feeding bans already in place due to CWD-positive deer reported in adjacent Oconto and Shawano counties.

The CWD-positive deer in Chippewa County was a hunter-harvested, 1-year-old buck. The finding will renew a three-year baiting and feeding ban in Chippewa County and a two-year ban in Barron County.

The DNR and the Chippewa County Deer Advisory Council are hosting a public meeting at 6:30 p.m. Feb. 6 to provide information about CWD in Wisconsin and local testing efforts in the county.

State law requires the DNR enact a three-year baiting and feeding ban in counties where CWD has been detected, as well as a two-year ban in adjoining counties within 10 miles of a CWD detection. If additional CWD cases are found during the lifetime of a baiting and feeding ban, the ban will renew for an additional two or three years.

Baiting or feeding deer encourages them to congregate unnaturally around a shared food source where infected deer can spread CWD through direct contact with healthy deer or indirectly by leaving behind infectious prions in their saliva, blood, feces and urine. More information regarding baiting and feeding regulations is available on the DNR’s Baiting and Feeding webpage.

More general information about CWD can be found on the DNR’s CWD webpage.

Officials with the Wisconsin Department of Agriculture Trade and Consumer Protection did not supply information last week after repeated requests for 2024 CWD data on deer farms and shooting preserves in the state.

In data last updated Sept. 25, 2023, DATCP’s webpage shows 46 deer farms with a CWD-positive animal since 2001. The agency says 24 of those facilities have been depopulated.