through the bird's digestive tract, crows represent a possible mechanism for the creation of environmental reservoirs of cwd. additionally, the crows' extensive geographic range presents ample opportunities for them to come in contact with cwd. this, coupled with the population density and longevity of communal roosting sites in both urban and rural locations, suggests that the fecal deposits at roosting sites may represent a cwd environmental reservoir. conservative estimates for crows' fecal deposits at one winter roosting site for one winter season ranged from 391,552 to 599,032 kg. cwd prions adhere so tightly to soil surface particles that the ground becomes a source of infection and may be a major route of transmission due to frequent ground contact when animals in the deer family graze. prevention by 2012, a voluntary system of control was published by aphis in the us federal register. it depended on voluntary minimum standards methodology, and herd certification programs to avoid interstate movement of the disease vector. it was based on a risk management framework. as of august 2019, aphis law in 9 cfr part 55 - control of chronic wasting disease dealt with this problem. introduced for the 2019 minnesota hunting season, a no-cost deer carcass-incineration program was rolled out by crow wing county officials hoping to stem the spread of cwd in the region. cwd was found among wild deer in crow wing county for the first time in january 2019. the voluntary program encourages both residents and visiting hunters to bring harvested deer carcasses to the county landfill east of brainerd, minnesota for incineration and disposal. diagnosis diagnosis is based on post mortem examination (necropsy) and testing; examination of the dead body is not definitive, as many animals die early in the course of the disease and conditions found are nonspecific; general signs of poor health and aspiration pneumonia, which may be the actual cause of death, are common. on microscopic examination, lesions of cwd in the cns resemble those of other tses. in addition, scientists use immunohistochemistry to test brain, lymph, and neuroendocrine tissues for the presence of the abnormal prion protein to diagnose cwd; positive ihc findings in the obex is considered the gold standard. conventional cwd diagnostic strategies and seeded amplification methods for amplifying cwd prions in vitro include: immunohistochemistry (ihc), western blotting (wb), enzyme immunoassay (eia), protein misfolding cyclic amplification (pmca), and real time quaking-induced conversion (rt-quic). available tests, as of july 2019, at the cfia were not sensitive enough to detect the prion in specimens from animals younger than a year old. strategies are being developed to allow for the quantification of prion burden in a tissue, body fluid, or environmental sample. as of 2015, no commercially feasible diagnostic tests could be used on live animals. as early as 2001 an antemortem test was deemed urgent. running a bioassay, taking fluids from animals in the deer family suspected of infection and incubating them in transgenic mice that express the cervid prion protein, can be used to determine whether the cervid is infected, but ethical issues exist with this, and it is not scalable. a tonsillar biopsy technique has been a reliable method of testing for cwd in live deer, but it only seems to be effective on mule deer and white-tailed deer, not elk. biopsies of the rectal mucosa have also been effective at detecting cwd in live mule deer, white-tailed deer, and elk, though detection efficacy may be influenced by numerous factors including animal age, genotype, and disease stage. it is possible for cwd prions to survive sterilization procedures involving an autoclave. epidemiology reported cases of chronic wasting disease in north america, as of 2018 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. the disease did not affect canada until 1996. in may 2001, cwd was also found in free-ranging deer in the southwestern corner of nebraska (adjacent to colorado and wyoming) and later in additional areas in western nebraska. the limited area of northern colorado, southern wyoming, and western nebraska in which free-ranging deer, moose, and/or elk positive for cwd have been found is referred to as the endemic area. the area in 2006 has expanded to six states, including parts of eastern utah, southwestern south dakota, and northwestern kansas. also, areas not contiguous (to the endemic area) areas in central utah and central nebraska have been found. the limits of the affected areas are not well defined, since the disease is at a low incidence and the amount of sampling may not be adequate to detect it. in 2002, cwd was detected in wild deer in south-central wisconsin and northern illinois and in an isolated area of southern new mexico. in 2005, it was found in wild white-tailed deer in new york and in hampshire county, west virginia. 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). europe 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 300 km north from the first case, in selbu. 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 environment agency of the norwegian government 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 (sva) 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