Alarming Rise Of CWD Threatens Northeast Montana’s Deer

Most of northeast Montana is seeing rising rates of chronic wasting disease (CWD), since the disease is spreading throughout the terrain.

Montana Fish, Wildlife & Parks has compiled CWD sample data from the big game season 2024.

2018 saw CWD first identified in northeast Montana. Hunter-harvested animal annual sampling shows that, particularly in mule deer, the frequency keeps rising.

"Region-wide, CWD prevalence in adult mule deer has increased from approximately 3 percent of the 2018-19 samples to almost 18 percent of 2024 samples," said Havre area biologist Scott Hemmer. "Prevalence is more marked for mule deer in the northern hunting districts that border Canada."

From deer numbers in Saskatchewan and Alberta, which have carried CWD for more than ten years, CWD most certainly first arrived in northern Montana.

With regard to adult mule deer, northern hunting district (HD) 600 has a prevalence rate of 28 percent following the most recent survey operations in 2024. With a prevalence of 34 percent in the northern-central portion of the territory, HD 670 reveals; on the eastern end of the region, HD 640 exhibits generally 30 percent prevalence rates in mule deer. In mule deer bucks, prevalence is considerably greater.

"We had early management goals to keep prevalence rates below 5 percent in the population; thus, this increase is rather alarming," Hemmer added. Other western states have documented decreases in deer populations linked with CWD prevalence exceeding 20 to 40 percent in a population.

Although CWD in whitetail deer in northeastern Montana has not been as high as in mule deer, most districts show rising frequency of whitetails throughout the region.

From 0 percent in 2018-2019 samples in the region to roughly 4 percent in 2024, the CWD prevalence trajectory has been slower and more erratic in adult whitetail deer, Hemmer stated. "The lower prevalence rate in whitetails could be due to a variety of factors, but one that may contribute is that whitetails are more common along the Milk and Missouri Rivers, which are 40 to 50 miles from the Canadian boundary."

CWD detection in Region 6 keeps expanding as well.

Two positive instances of CWD were found for the first time in HD 620 in central Phillips County during this hunting season. FWP employees observe CWD spread annually to both new places inside hunting districts in northeast Montana and to other hunting districts.

For the first time, CWD was found in a whitetail deer in HD 650, in McCone County.

Only two hunting districts in northeastern Montana—HD 621, in southern Phillips County, and HD 652, a permit-only area for mule deer buck hunting in McCone County along Fort Peck Reservoir—have yet to have CWD detected. Since fewer samples have come from these hunting zones, the absence of a detection does not imply that CWD is absent there either.

Handling CWD going forward

Monitoring and controlling the CWD spread mostly depends on hunting. FWP mostly watches the disease using hunter-harvested samples. The attempts of FWP to control CWD depend on these samples.

Visit fWP.mt.gov/cwd for the most recent data on CWD, including disease information, detection maps, and information on animal sample procedures.

What is CWD?

Affecting members of the deer family, including elk, moose, mule deer, and whitetail deer, CWD is a viral brain illness. The sick animal dies inevitably; there is no known treatment. Montana's wild herds first revealed CWD in 2017.

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No known human transmission of CWD exists. The Centers for Disease Control advise hunters gathering deer, elk, or moose from an area known to be CWD-positive to have their animal tested before eating the meat and not eat the meat should the animal test positive.