CWD background & resources

How does CWD affect wildlife populations?

CWD can affect deer populations over time, especially when the disease becomes more common in an area. Research suggests that as CWD prevalence increases, the disease can contribute to declines in deer populations.

CWD may also affect the age structure of deer herds. Because the disease takes years to develop and is always fatal, infected deer may die before reaching older ages. Research has shown that CWD is more common in bucks than does, with prevalence in bucks often two to three times higher. This may contribute to fewer older bucks in affected populations and a younger age structure within deer herds.

Wildlife managers continue to study CWD to better understand how the disease affects deer populations and what steps can help maintain healthy wildlife populations.

What are the signs of CWD in deer, elk, and moose?

CWD is a slow, progressive disease. In the early stages, infected deer show no visible signs of illness but can still spread the disease to other animals and contaminate the environment. The majority of harvested animals that test positive for CWD show no outward signs of disease. It can take months to years before signs appear and these may include:

• Weight loss, emaciation
• Increased drinking and urination
• Lethargy and reluctance to move
• Loss of awareness, may not notice or respond to human presence normally
• Drooping head or ears

How is CWD spread?

CWD can spread directly from one animal to another and indirectly through the environment. Infected animals shed prions through saliva, urine, blood, and feces. Additionally, carcasses from dead infected deer can serve as a source of further infection. When people feed deer or provide attractants such as salt licks, more deer gather in one place. This increases the chances that CWD will spread through direct contact between animals or through contaminated soil, plants, and other parts of the environment.

How do you test for CWD?

Testing is conducted by collecting specific tissues including lymph nodes and the brain stem and sending them to a certified laboratory where they test for prions.

History of CWD in Minnesota

The DNR conducts yearly surveillance for CWD in wild cervid populations in Minnesota. Since 2002, more than 165,000 wild deer have been tested for CWD in Minnesota. The disease was first detected in wild deer in Minnesota in 2010. CWD has also been detected in deer/elk farms in the state. In Minnesota, farmed cervids are classified as livestock.

The DNR regulates captive white-tailed deer. The Minnesota Board of Animal Health regulates all other cervids.

Minnesota CWD Timeline

2002	A CWD-positive elk farm found in Aitkin County. This marks the first CWD positive animal in Minnesota and DNR's first concentrated surveillance effort in wild white-tailed deer.
2003	A CWD-positive elk farm in Stearns County discovered. This is a trace-out from the Aitkin County farm.
	DNR granted legal authority to open and close seasons, restrict feeding and impose rules to limit disease spread.
2004	DNR completes 3-year statewide surveillance project. In total, 28,000 deer were tested and the disease was not found.
2006	A CWD-positive white-tailed deer farm is discovered in a mixed deer/elk farm in Lac Qui Parle County.
2009	A CWD-positive elk farm in Olmsted County is discovered. The United States Department of Agriculture (USDA) determines there has been an apparent long-standing infection within the herd. DNR implements the response plan, which calls for three years of surveillance in the area around the facility.
2010	A wild CWD positive white-tailed deer is discovered within two miles of the CWD positive elk farm in Olmsted County. DNR's response plan requires that intense surveillance be conducted around the area of infection. This deer was discovered during the second year of the surveillance program.
2011	A new CWD management zone (deer permit area 602) is created and DNR begins three years of surveillance around the infected farm.
2012	A farmed European red deer is found infected with CWD in a facility in Ramsey County. DNR's response plan is implemented, which calls for three years of surveillance in the area around the facility.
2013	DNR completes three-year intensive CWD surveillance around the Olmsted County elk farm. More than 4,000 wild deer are tested in the immediate area and no additional positives are detected.
2014	CWD discovered in wild deer in Allamakee County, Iowa, which borders Minnesota's Houston County. DNR tests 400 deer along the border but detects no disease. DNR completes three years of CWD surveillance around the Ramsey County European red deer farm with no positives found.
2016	Ongoing detections of CWD positive wild deer in southwestern Wisconsin and northeastern Iowa prompted DNR to conduct voluntary surveillance in southeast Minnesota. During the 2016 deer season, three positive wild deer (adult males) are found in Fillmore County near Preston. DNR implements its response plan, which calls for an aerial survey of the area to assess deer numbers in the area and the collection of additional samples to assess disease prevalence and distribution.
	CWD Management Zone (deer permit area 603) is created to enforce additional restrictions on deer feeding and carcass export restrictions.
	A CWD-positive deer farm is discovered in Crow Wing County. DNR implements its response plan, which calls for three years of surveillance in the area around the facility.
2017	Winter: Eight additional CWD positive wild deer are found in DPA 603 during the special late hunts, landowner shooting permit phase and USDA agency culling during winter 2017.
	Spring: A CWD-positive deer farm is discovered in Meeker County. This farm is a trace-out from the Crow Wing County farm. The DNR implements its response plan, which calls for three years of surveillance in the area around the facility.
	Fall: Mandatory surveillance is conducted during the opening weekend of the firearm season in north-central and central Minnesota surrounding the recently detected CWD positive farms in Crow Wing and Meeker counties. Mandatory surveillance also occurs in southeast Minnesota in all deer permit areas surrounding and including DPA 603. Six additional CWD-positive wild deer are discovered within DPA 603. No positives are found in the north-central or central surveillance areas. Another CWD-positive deer farm is discovered in Winona County. All nine captive deer on this farm were infected. This farm is within the southeast surveillance area, but three years of surveillance will be conducted around this facility.
2018	Fall: Mandatory surveillance during the opening weekend of the firearm season continues in the north-central and central parts of the state around the Crow Wing and Meeker County positive deer farms. Since no disease was found in 2017, the surveillance zone is a smaller area directly around the farms.
	Fall: Mandatory surveillance is expanded in the southeast due to the CWD positive deer farm in Winona County, new positive wild deer found in Eau Claire County, Wisconsin, and the ongoing detection of positive wild deer in DPA 603.
	CWD detected in 16 wild deer in Fillmore County, one wild deer in Houston County, and found again in the deer farm in Crow Wing County where positive captive deer were found in 2016.
2019	Winter: CWD is first found in one wild deer in Crow Wing County near a CWD-positive deer farm. Seventeen additional CWD-positive wild deer are found in southeastern Minnesota during the landowner shooting permit phase and USDA agency culling.
	Fall: Mandatory surveillance during the opening weekend of the firearm season took place in central Minnesota around the Meeker County positive deer farm. In total, 544 samples were collected and none tested positive for CWD. Because no wild deer positives were detected in its third consecutive year of testing, there will be no more testing in this area during the 2020 hunting season.
	Fall: Mandatory surveillance is expanded in the southeast due to the CWD-positive wild deer in Houston County. The previous disease management area (deer permit area 603) is dissolved back to the historic deer permit areas and replaced by a 600-series of deer permit areas that signify disease management areas. A control zone (deer permit areas 255, 343 and 344) is established on the border of the disease management zone; carcass movement restrictions are in place in both these zones. In total, 13,181 samples were collected from hunter harvested deer in the southeast with 26 additional positive cases.
	Fall: A new CWD management zone (deer permit area 604) is created in north-central Minnesota, in a 15-mile radius around the CWD-positive wild deer found in February 2019 and the CWD-positive deer farm in Crow Wing County. In total, 3,966 deer were sampled with no additional positives detected.
	Winter: Confirmation of a CWD-positive doe on a deer farm in Douglas County in December. That month, the DNR issues an emergency rule that temporarily prohibits the movement of all farmed white-tailed deer within the state for 30 days to give the state time to evaluate the outbreak, generate potential solutions to containing and eliminating the disease, and protect the wild deer herd.
2020	Winter: Seven additional CWD-positive wild deer are found during management operations in the southeast within 2 miles of known CWD-positive wild deer. Landowner shooting permits collected 10 samples with no detections of disease and USDA agency culling collected 463 samples with seven positives.
	Winter: A new CWD-positive deer farm was confirmed in Pine County in January.
	Winter: CWD is first found in Dakota County in March, in a wild deer that was reported sick by the public as emaciated, circling/stumbling and not afraid of people. The deer was euthanized and the necropsy showed positive for CWD. The DNR implements its response plan, which calls for a new CWD management zone in the immediate area where the deer was collected.
	Fall: The DNR shifted to voluntary sampling due to the COVID-19 pandemic, using unstaffed sampling stations in all surveillance areas and zones to facilitate social distancing. Two new surveillance areas, one in west-central Minnesota and one in east-central Minnesota, were created following detection of CWD in deer at farms in Douglas and Pine counties. In west-central Minnesota, 446 samples were collected with no CWD detections; in east-central Minnesota 361 samples were collected with no CWD detections. In total, 4,582 samples were collected from hunter-harvested deer in the southeast management and control zones, with 19 additional positive cases. In deer permit area 604, 951 samples were collected and no additional positives were detected. In the new, metro-area CWD management zone (deer permit area 605) and its accompanying surveillance area, 1,423 samples were collected, with four additional positive cases.
2021	Winter: Five additional CWD-positive wild deer are found during management operations in the southeast and metro areas, within 2 miles of known CWD-positive wild deer: Landowner shooting permits collected 37 samples with no detections of disease and USDA agency culling collected 542 samples with 5 positives.
	Spring: A new CWD-positive deer farm was confirmed in Beltrami County in April.
	Fall: A hunter harvested a wild deer with CWD near Climax in northwestern Minnesota. Additional CWD-positive wild deer are found from hunter harvested deer; 27 in the southeast, two in DPA 605, one in DPA 604 and one in DPA 261.
2022	Winter: A resident within the Grand Rapids city limits reported a sick deer. That deer tested positive for CWD. Additional culling within the Grand Rapids city limits discovers a second positive deer within a mile of the first one. Eighteen additional CWD-positive wild deer are found during management operations in the southeast all within 2 miles of known CWD-positive wild deer through USDA agency culling.
	Summer: A new CWD-positive deer farm was confirmed in Winona County in August.
	Fall: Two new CWD management zones were created where the disease was detected within wild deer; DPA 661 near Climax and DPA 679 near Grand Rapids. Additional CWD-positive wild deer are found from hunter harvested deer; 19 in the southeast, 5 in DPA 605, and 2 in DPA 184.
2023	Winter: A dead doe found near Brainerd tests positive. Culling in the south metro area resulted in two CWD-positive wild deer. Additional culling within the southeast discovers 18 CWD-positive wild deer. One reported sick doe tests positive for CWD in the southeast.
	Fall: A dead buck found in the south metro area tests positive. A hunter-harvested buck tests positive for CWD from DPA 342 – the first detection in this DPA. Additional CWD-positive wild deer are found from hunter-harvested deer: Two from the Climax area. Two from the Grand Rapids area. Two from the south metro. 36 from the southeast.
2024	Winter: A shooting permit in DPA 661 resulted in an additional positive deer. Additional culling within the southeast discovers 17 CWD-positive wild deer.
	Fall: Hunter harvested deer in DPA 266, 271, and 701 result in the detections of CWD in the wild deer herd for these DPAs. Additional CWD-positive wild deer are found from hunter harvested deer: One from the south metropolitan area. One from the Climax area. 86 from the southeast.
2025	Winter: A reported sick deer was collected in DPA 604 testing positive for CWD.
	Fall: A hunter harvested deer in DPA 285 resulted in the detection of CWD in the wild deer herd. An additional 122 CWD-positive wild deer were found within management zone DPAs: 604, 605, 643, 644, 645, 646, 647, 648, 649, 655, 666, 671, 684. These cases were the first CWD positive detections in DPAs 644 and 655.