| || What is it? | What are the symptoms? | How is CWD transmitted? | Are humans at risk? | Is the disease transmissible to domestic livestock? | Where has CWD occurred? | What is the Province's role once a case of CWD has been confirmed? | If CWD is diagnosed on a game farm | When animals are destroyed are owners compensated? | What policies does the Province have in place to prevent or control the further spread of CWD in Alberta?
What is it?
Chronic wasting disease (CWD) is a progressive, fatal, degenerative disease of the brain affecting elk, mule deer and white-tailed deer.
CWD belongs to a group of related diseases called Transmissible Spongiform Encephalopathies (TSEs), which include Scrapie in sheep and goats, Bovine Spongiform Encephalopathy (BSE) in cattle and Creutzfeldt-Jakob Disease (CJD) in humans. CWD is not the same as BSE.
TSEs are caused by abnormal proteins, called prions, which accumulate in the brain. There is currently no treatment or vaccine available.
What are the Symptoms?
Elk and deer with CWD may not exhibit observable symptoms of disease for a number of years. Eventually, as more brain tissue is affected, animals may exhibit loss of condition, excessive salivation, trouble swallowing, difficulty in judging distance, changes in behaviour and drooping ears.
Unfortunately, these symptoms are not specific to CWD and can occur with other diseases as well. Currently, the only way to diagnose CWD is by examining the brain tissue after the animal has died. Immunohistochemistry (IHC) staining is the universally accepted “gold standard” method of confirmation, although a number of rapid tests are able to screen for the disease.
How is CWD Transmitted?
The exact mechanism of transmission is unclear at this time, however, it is known that the disease can spread from one animal to another and females can pass it to their offspring.
Experimental and circumstantial evidence suggests infected deer and elk probably transmit the disease through contamination of water and feed by saliva and/or feces. CWD seems more likely to occur where elk or deer are crowded or where they congregate at man-made feed and water stations. A heavily contaminated environment can be a source of infection.
Are Humans at Risk?
There is no scientific evidence to suggest that CWD can affect humans. As a precaution, the World Health Organization advises against allowing any meat source possibly infected by prions into the human food system.
Is the Disease Transmissible to Domestic Livestock?
Scientific evidence suggests that it is unlikely that CWD can be passed to domestic cattle or bison under natural conditions. To date, research in the United States indicates cattle are not susceptible to oral exposure to CWD. However, the experiments still have some time to run. CWD has been experimentally transmitted by artificial means to mice, ferrets, mink, goats, squirrel monkeys and calves.
Where has CWD Occurred?
CWD has been diagnosed in wild deer and elk in at least 11 states in the United States and two Canadian provinces. Since 2001, CWD has been detected in several locations across Saskatchewan. Since 2005, CWD has been detected in Alberta in several locations along the Saskatchewan border.
In September 2005, Alberta’s first case of CWD was confirmed by the Canadian Food Inspection Agency (CFIA) in a wild mule deer found 30 kilometres southeast of Oyen. To reduce the spread of the disease, Alberta Sustainable Resource Development (ASRD) staff, with the cooperation of landowners and hunters, implemented a CWD control program in wild deer.
Please visit the Fish and Wildlife tab for additional information and maps, as well as information for hunters.
The disease has also been diagnosed in game farmed elk and deer in South Dakota, Oklahoma, Nebraska, Kansas, Montana, Colorado, Minnesota, New York, Michigan, Wyoming and Saskatchewan. One case of CWD in a farmed elk was detected in Alberta in the spring of 2002, and two farmed white-tailed deer were confirmed positive for the disease in November 2002. Both herds and traceout animals were depopulated.
What is the Province's Role Once a Case of CWD has Been Confirmed?
CWD is a reportable disease in Canada under the Health of Animals Act and therefore, falls under the jurisdiction of the CFIA.
Once a case of CWD is confirmed, the province’s role is to support the CFIA in applying their control measures, which includes placing the source farm under quarantine. The province also assists by providing animal movement information and priority lab analysis, as well as keeping the livestock industry and the public informed.
If CWD is Diagnosed on a Game Farm:
Present federal policy is to eradicate CWD from Canada, which may involve placing affected farms under quarantine and then evaluating, euthanizing, sampling and destroying remaining animals. Animals that have left the affected herd may also be euthanized or put under quarantine. The CFIA has depopulated over 7,500 farmed elk and deer because of CWD since 1996.
When Animals are Destroyed are Owners Compensated?
Yes, compensation will be paid for all animals ordered destroyed as set out by the Health of Animals Act. Disposal costs will also be paid.
What Policies Does the Province Have in Place to Prevent or Control the Further Spread of CWD in Alberta?
Alberta initiated a voluntary CWD surveillance program in October 1996. In August 2002, Alberta’s Mandatory CWD Surveillance Program was implemented. Elk and deer farmers are required to submit the heads, for CWD testing, from all farmed animals over one year of age that die or are slaughtered. Product from slaughtered animals must be held at abattoirs pending CWD test results.
In July 2004, the Alberta Government ended a moratorium on importing elk and deer, by approving a cervid import protocol that allows elk, white-tailed deer, and mule deer to be imported into the province from Saskatchewan for immediate slaughter at federally inspected abattoirs.
In September 2004, the Alberta Government began allowing elk, white-tailed deer, and mule deer from anywhere in Canada and the United States to live on Alberta farms. To qualify for importation into Alberta, cervids must meet strict criteria to ensure that CWD is not imported into the province. Both of these policies were developed based on a scientific risk assessment.
Since 1996, ASRD has conducted surveillance of wild elk and deer. Their efforts concentrate on areas where CWD has been discovered in domestic cervids and along the Alberta-Saskatchewan border. For information on the latest wild cervid surveillance initiatives, please go to the ASRD website.
Over 45,000 farmed and wild cervids have been tested in Alberta since 1996. Monthly CWD testing results in Alberta are available on the Chief Provincial Veterinarian website.
For more information about CWD, contact your local veterinarian, or consult the following web pages:
Canadian Food Inspection Agency website
Alberta Agriculture and Rural Development website
Alberta Sustainable Resources Development website
The Animal and Plant Health Inspection Service (APHIS) website for updates on CWD in the United States:
Source: Agdex 663-43. Revised June 2008.