North America The disease was first identified in 1967 in a closed herd of captive
mule deer in contiguous portions of northeastern Colorado. In 1980, the disease was determined to be a TSE. It was first identified in wild
elk and mule deer and
white-tailed deer in the early 1980s in Colorado and Wyoming, and in farmed elk in 1997. In 2008, the first confirmed case of CWD in
Michigan was discovered in an infected deer on an enclosed deer-breeding facility. It is also found in the Canadian provinces of
Alberta and
Saskatchewan. In February 2011, the
Maryland Department of Natural Resources reported the first confirmed case of the disease in that state. The affected animal was a white-tailed deer killed by a hunter. CWD has also been diagnosed in farmed elk and deer herds in a number of states and in two Canadian provinces. The first positive farmed-elk herd in the United States was detected in 1997 in South Dakota. Since then, additional positive elk herds and farmed white-tailed deer herds have been found in South Dakota (7), Nebraska (4), Colorado (10),
Oklahoma (1), Kansas (1),
Minnesota (3),
Montana (1), Wisconsin (6), and New York (2). As of fall of 2006, four positive elk herds in Colorado and a positive white-tailed deer herd in Wisconsin remain under state
quarantine. All of the other herds have been depopulated or have been slaughtered and tested, and the quarantine has been lifted from one herd that underwent rigorous surveillance with no further evidence of disease. CWD also has been found in farmed elk in the Canadian provinces of
Saskatchewan and
Alberta. A retrospective study also showed mule deer exported from
Denver to the
Toronto Zoo in the 1980s were affected. In June 2015, the disease was detected in a male white-tailed deer on a breeding ranch in
Medina County, Texas. State officials euthanized 34 deer in an effort to contain a possible outbreak. In February 2018, the Mississippi Department of Wildlife, Fisheries, and Parks announced that a
Mississippi deer tested positive for chronic wasting disease. Another Mississippi whitetail euthanized in
Pontotoc County on 8 October 2018 tested positive for CWD. The disease was confirmed by the
National Veterinary Services Laboratory in
Ames, Iowa on 30 October 2018. Species that have been affected with CWD include elk, mule deer, white-tailed deer,
black-tailed deer, and moose. Other
ruminant species, including wild ruminants and domestic
cattle,
sheep, and
goats, have been housed in wildlife facilities in direct or indirect contact with CWD-affected deer and elk, with no evidence of disease transmission. However, experimental transmission of CWD into other ruminants by intracranial inoculation does result in disease, suggesting only a weak molecular species barrier exists. Research is ongoing to further explore the possibility of transmission of CWD to other species. By April 2016, CWD had been found in captive animals in South Korea; the disease arrived there with live elk that were imported from Canada for farming in the late 1990s. In the summer of 2018, cases were discovered in the Harpur Farm herd in
Grenville-sur-la-Rouge,
Quebec. Over the course of 2018, 12% of the
mule deer that were tested in
Alberta, had a positive result. More than 8% of Alberta deer were deemed
seropositive. In 2022, it had been recorded that outbreaks of CWD had shown themselves in both the United States and Canada. CWD was present in 29 states, infecting herds of moose, deer and elk in 391 different counties. Alabama (1), Arkansas (19), Colorado (27), Idaho (1), Illinois (19), Iowa (12), Kansas (49), Louisiana (1), Maryland (1), Michigan (9), Minnesota (7), Mississippi (9), Missouri (21), Montana (23), Nebraska (43), New Mexico (3), New York (1), North Carolina (1), North Dakota (7), Ohio (2), Pennsylvania (14), South Dakota (19), Tennessee (14), Texas (7), Utah (7), Virginia (10), West Virginia (5), Wisconsin (37) and Wyoming (22). In June 2023, as the spread continued, CWD was found in Oklahoma (1) in the wild and Florida (1) for the first time. A case in October 2023 in
Yellowstone National Park, Wyoming, whose ecosystem supports the greatest and most diverse array of large wild mammals in the continental US, was reported. The first case in Kentucky was confirmed in December 2023. In January 2024, British Columbia's surveillance program identified its first two positive deer samples from the Kootenay region of the province. In April 2025, the Georgia Department of Natural Resources confirmed a second case of CWD in a 4.5-year-old male deer in Berrien County, approximately 400 yards from the first detected case.
Quebec farm outbreak Quebec's practiced 9500 tests in the period between 2007 and autumn 2018 before they detected a seropositive case in September 2018. A 400 km2 quarantine area was declared, in which all hunting and trapping activities were banned. The government slaughtered hundreds of wild animals over a two-month period. The routine cull for market was between 70 and 100 animals per week. When the producer was forced to close, the weekly slaughter neared 500 animals per week. The quarantine around Grenville was still in place, and the ministry specifically prohibited (only) the "removal" from the quarantine "enhanced monitoring area" zone of "the head, more specifically any part of the brain, the
eyes, the
retropharyngeal lymph nodes and the
tonsils, any part of the
spinal column, the internal organs (including the
liver and the
heart), and the
testicles."
Europe Nordics In 2016, the first case of CWD in Europe was from the Nordfjella wild reindeer herd in southern
Norway. Scientists found the diseased female reindeer as it was dying, and routine CWD screening at necropsy was unexpectedly positive. The origin of CWD in Norway is unknown, whereas import of infected deer from Canada was the source of CWD cases in
South Korea. Norway has strict legislation and rules not allowing importation of live animals and deer into the country. Norway has a
scrapie surveillance program since 1997; while no reports of scrapie within the range of Nordfjella reindeer population have been identified, sheep are herded through that region and are a potential source of infection. In May and June 2016, two infected wild moose (
Alces alces) were found around north from the first case, in
Selbu Municipality. By the end of August, a fourth case had been confirmed in a wild reindeer shot in the same area as the first case in March. In 2017, the
Norwegian Environment Agency released guidelines for hunters hunting reindeer in the Nordfjella areas. The guidelines contain information on identifying animals with CWD symptoms and instructions for minimizing the risk of contamination, as well as a list of supplies given to hunters to be used for taking and submitting samples from shot reindeer. In March 2018, Finnish Food Safety Authority EVIRA stated that the first case of CWD in Finland had been diagnosed in a 15-year-old moose (
Alces alces) that had died naturally in the municipality of
Kuhmo in the
Kainuu region. Before this case in Kuhmo,
Norway was the only country in the
European Economic Area where CWD has been diagnosed. The moose did not have the transmissible North American form of the disease, but similar to the Norwegian variant of CWD, an atypical or sporadic form which occurs incidentally in individual animals of the deer family. In Finland, CWD screening of fallen wild deer has been done since 2003. None of the roughly 2,500 samples analyzed so far have tested positive for the disease. The export of live animals of the deer family to other countries has been temporarily banned as a precautionary measure to stop the spread of the CWD, and moose hunters are going to be provided with more instructions before the start of the next hunting season, if appropriate. The export and sales of meat from deer will not be restricted and moose meat is considered safe to eat as only the brain and nervous tissue of infected moose contains prions. In March 2019, the
Swedish National Veterinary Institute diagnosed the first case of CWD in Sweden. A 16-year old emaciated female moose was found in the municipality of
Arjeplog in the county of
Norrbotten, circling and with loss of shyness towards humans, possibly blind. The moose was euthanized and the head was sent for CWD screening in the national CWD surveillance program. The brainstem tissue, but not lymph nodes, was positive for CWD (confirmed with Western Blot). A second case of CWD was diagnosed in May 2019, with very similar case history, about 70 km east of the first case. This second case, in the municipality of
Arvidsjaur, was also an emaciated and apathic 16-year-old female moose that was euthanized. The circumstances of these Swedish cases are similar to the CWD cases in moose in both Norway and Finland. The EU regulated CWD surveillance runs between 2018 – 2020. A minimum of 6,000 deer are to be tested, both free-ranging animals in the deer family, farmed red deer, and semi-domesticated reindeer. The finding of CWD-positive moose initiated an intensified surveillance in the affected municipalities. Adult hunter-harvested moose and slaughtered semi-domesticated reindeer from the area are tested for CWD. In September 2019, a third moose was found positive for CWD, a hunter-harvested 10-year-old apparently healthy female moose from Arjeplog. ==Research==