Six new counties had positive cases of chronic wasting disease, DNR says

Six new Iowa counties have been added to the list of places where chronic wasting disease -- a neurological illness that affects deer, elk and moose -- is confirmed.

First-time detections of chronic wasting disease were found in Shelby, Pottawattamie, Davis, Wapello, Cedar and Story counties during the 2024-25 surveillance season.

This comes after the Iowa Department of Natural Resources anticipated a “significant rise” in positive cases of the disease before hunting season in December.

This past surveillance season — which ran from April 1, 2024, to March 31, 2025 — brought the number of Iowa counties with positive detections to 29.

Rachel Ruden, a wildlife veterinarian with the DNR, said this year’s count was about what she expected.

“I would say [the number of cases] is on par to even a little lower than what I anticipated given the growth we’ve seen since 2021,” she said.

That is an increase from previous years. During the 2023-24 surveillance season, the DNR recorded 128 positive cases, up from 96 the previous season, 52 the season before that, and 21 in 2020-21.

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Ruden, who also is an affiliate assistant professor for the College of Veterinary Medicine at ISU, said many of the counties that recorded new detections neighbor counties that have had positive cases of the disease.

Davis and Wapello counties in southern Iowa are examples of this, Ruden said. They are adjacent to five other south central Iowa counties that the DNR considers an “endemic area.”

The area includes Appanoose, Monroe, Lucas, Wayne and Decatur counties, all of which had previous positive detections.

In Eastern Iowa, Cedar County joins Jones, Muscatine and several other counties that have recorded positive cases.

Ruden said the DNR recorded 135 individual positive detections through the 2024-25 surveillance season — a number not currently reflected on the DNR’s interactive dashboard for tracking the disease. Ruden said the total number of cases will be reflected in the database soon.

Adam Janke, an associate professor in the Department of Natural Resource Ecology and Management at Iowa State University, said Iowa researchers typically study the annual surveillance results in two ways: the prevalence — or, the number of infected deer in areas of known occurrence — and the extent of the disease, or where it is found.

Janke, who also is a wildlife extension specialist with ISU’s Extension and Outreach, said both categories increased this year.

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“It's more notable or surprising to discuss extent than prevalence because in general we still see very low prevalence but we're finding it in low numbers in a lot of places,” Janke said.

Janke said that among nearly 106,000 deer tested in Iowa since 2002, a total of 521 deer have tested positive.

During the most recent surveillance year, 5,493 deer were tested and only about 2.4 percent were found to be positive for the disease, he said.

“That does not mean that two out of every 100 deer in Iowa has CWD,” Janke said. “Rather, it's likely lower since the DNR strategically targets surveillance testing in places where they think the disease may be or is known to occur, and toward deer that are more likely to have it (which is) adult males.”

Ruden said the DNR has been arranging incentive deer hunts in specific areas of the state since 2021 to help manage CWD prevalence and increase carcass testing for the disease.

As a result, Ruden said some of the counties with more CWD cases are a bit “inflated” because hunters are targeting those areas specifically. The targeted hunts this last surveillance season were in Allamakee, Dubuque and Wayne counties.

What is chronic wasting disease?

Chronic wasting disease — which is uniformly fatal and highly contagious — is caused when misfolded proteins, called prions, attack the brain and the nervous systems of animals as it accumulates in their tissues.

The disease predominately occurs in white-tailed deer, elk, moose and reindeer, and has been growing in Iowa and other Midwest and northern states.

CWD typically has a long incubation period, ranging between 16 months to three years before an infected animal begins showing symptoms.

A deer showing symptoms of CWD can look sick in a variety of ways, including drooling, poor balance and emaciation, however, animals can be without symptoms and still be infected. To date, there is no cure or vaccine viable to treat the disease.

“We generally advise hunters and consumers of deer meat to test animals harvested in counties where the disease has been detected. That was once quite easy to remember with just a few counties on that list,” Janke said, adding that it is now in nearly a third of Iowa’s counties.

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

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Comments: olivia.cohen@thegazette.com