GLASGOW – Chronic wasting disease (CWD) prevalence is increasing in most of northeast Montana, as is the spread of the disease across the landscape.
Montana Fish, Wildlife & Parks recently tallied results of CWD samples taken during the 2024 big game season.
CWD was first detected in northeast Montana in 2018. Annual sampling of hunter-harvested animals, show the prevalence continues to increase, especially in mule deer.
“Region-wide, CWD prevalence in adult mule deer has increased from around 3 percent of the 2018-19 samples to almost 18 percent of 2024 samples,” said Scott Hemmer, Havre-area biologist, who helps keep tabs on CWD in the region. “Prevalence is more pronounced for mule deer in the northern hunting districts that border Canada.”
CWD likely first reached northern Montana from deer populations in Saskatchewan and Alberta, which have had CWD for more than a decade.
Following the latest sampling efforts in 2024, northern hunting district (HD) 600 has an annual prevalence rate of 28 percent for adult mule deer. HD 670, in the north-central area of the region, shows an annual prevalence of 34 percent, and HD 640, on the eastern end of the region, has overall annual prevalence rates in mule deer of 30 percent. Prevalence in mule deer bucks is even higher.
“This increase is rather concerning, as we had early management objectives to keep prevalence rates below 5 percent in the population,” Hemmer said. “Other western states have reported deer population declines correlated with CWD prevalence surpassing 20 to 40 percent in a population.”
CWD in whitetail deer in northeast Montana hasn’t been as high as in mule deer, but whitetails also show prevalence increasing across the region in most districts.
“In adult whitetail deer, the CWD prevalence trend has been slower and more sporadic, from 0 percent in 2018-2019 samples in the region, to around 4 percent in 2024,” Hemmer said. “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 border.”
Detection of CWD in Region 6 continues to spread as well.
This hunting season, CWD was detected for the first time in HD 620 in central Phillips County, with two positive cases. Every year, FWP staff see CWD spread both to new hunting districts and to new areas within hunting districts in northeast Montana.
In addition, for the first time, CWD was detected in a whitetail deer in HD 650, which is in McCone County.
Only two hunting districts in northeast Montana have yet to have a CWD detection: HD 621, which is in southern Phillips County, and HD 652, which is a permit-only area for mule deer buck hunting in McCone County along Fort Peck Reservoir. The absence of a detection doesn’t mean that CWD is not in these hunting districts, as fewer samples have come from these areas.
Managing CWD in the future
Hunting is the primary tool for monitoring and managing the spread of CWD. Hunter-harvested samples are the primary way FWP monitors the disease. These samples are critical to FWP’s efforts to manage CWD.
For the latest information on CWD, including detection maps, disease information and information on how to get your animal sampled please go to fwp.mt.gov/cwd.
What is CWD?
CWD is a contagious neurological disease that infects members of the deer family, including elk, moose, mule deer, and whitetail deer. It is always fatal to the infected animal, and there is no known cure. CWD was first detected in Montana’s wild herds in 2017.
There is no known transmission of CWD to humans. However, the Centers for Disease Control recommends that hunters harvesting deer, elk or moose from an area where CWD is known to exist have their animal tested prior to consuming the meat and do not consume the meat if the animal tests positive.
