Chronic wasting disease (CWD) fact sheet
What is chronic wasting disease?
Chronic wasting disease (CWD) is a progressive, fatal nervous system disease known to naturally infect white-tailed deer, mule deer, moose, red deer, elk and reindeer.
CWD belongs to the family of diseases known as transmissible spongiform encephalopathies (TSEs), or prion disease. Though it shares features with other TSEs, such as bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep, it is a distinct disease only known at this time to naturally affect members of the deer (cervid) family.
Is CWD a risk to human health?
At this time there is no direct scientific evidence to suggest that CWD may be transmitted to humans.
As a precautionary measure, it is recommended that any tissue that may have come from a known CWD-infected animal not be used or consumed by humans.
Measures have been taken at both the federal and provincial/territorial levels to reduce human exposure to products potentially contaminated by CWD by preventing known infected animals from entering the food chain.
Health Canada recommends that people avoid consuming meat from animals known to be infected with any TSEs. In areas where CWD is known to exist in wild cervids, hunters are encouraged to take precautions when handling carcasses and should consider having those animals tested before eating the meat, preparing trophies or tanning hides. Any further questions related to human health and food safety can be directed to Health Canada.
If members of the public have concerns, they should contact provincial or territorial officials where they live or hunt.
- Information for hunters:
What are the clinical signs of CWD?
Animals with CWD may show a number of different signs as the disease slowly damages their brain. They may include:
- difficulty swallowing
- excess salivation
- increased thirst
- lack of coordination
- separation from the other animals in the herd
- unusual behaviour
- excessive urination and
- weight loss
Signs can last for weeks to months before the animal dies; however, some animals may not show clinical signs. Animals are usually three to four years old before clinical signs appear, but signs have been seen in animals as young as 15 months or as old as 13 years.
Where is CWD found?
First recognized as a "wasting syndrome" in a research facility in Colorado in 1967, CWD has only been found in captive and wild cervids in North America, the Republic of Korea, Norway and Finland.
In Canada, CWD was first detected on a Saskatchewan elk farm in 1996. The disease has been routinely detected in parts of Saskatchewan and Alberta and, more recently, on a red deer farm in Quebec.
How is CWD transmitted and spread?
Both direct (animal-to-animal) and indirect environmental (animal-to-premises-to-animal) transmission occur in cervids. It is believed that direct transmission occurs via shedding of the infectious agent in saliva, milk and feces. The incubation period typically lasts from 16 to 36 months.
How is CWD diagnosed?
CWD is tentatively diagnosed based on clinical signs, but can only be confirmed by testing of tissue from the affected animal after it is dead. A negative test result does not guarantee that an individual animal is not infected with CWD, but it does make it considerably less likely and may reduce your risk of exposure to CWD, for example through contact with that animal's tissues.
How is CWD treated?
No treatment is available for animals with CWD. No vaccine is available to prevent CWD infection.
What is done to protect Canadian livestock from CWD?
The management of CWD in Canada is a joint responsibility of farmed cervid producers, provinces/territories and the federal government. CWD is a "reportable disease" under the Health of Animals Act. This means that all suspected cases must be reported immediately to the CFIA.
All cervids slaughtered in abattoirs in Saskatchewan, Alberta, Manitoba, Yukon and Quebec are required to be tested for CWD. This applies to federal, provincial and territorial abattoirs in those provinces.
Some provinces and territories offer testing services to hunters if they choose to have their carcasses tested for CWD. A negative test result does not guarantee that an individual animal is not infected with CWD, but it does make it considerably less likely and may reduce your risk of exposure to CWD. If members of the public have concerns, they should contact the provincial or territorial officials where they live or hunt.
The CFIA implemented a CWD eradication policy in October 2000. In 2002, the CFIA established national standards for a Voluntary Herd Certification Program (VHCP), which lays out requirements for biosecurity measures to prevent CWD and mitigate the risk of infection. Risk-mitigation measures for farmed cervids also include mandatory testing and limits on which animals may be added to the herd.
The CFIA sets the national standards, provides oversight and audits the third-party administrators of the VHCPs. In 2015 and 2016, the CFIA consulted with stakeholders regarding enhancements to the VHCP National Standards. Updated national standards were published in 2017, and fully implemented in all participating areas of Canada in 2018.
How would the CFIA respond to an outbreak of CWD in Canada?
CWD is a "reportable disease" under the Health of Animals Act. This means that all suspected cases must be reported to the CFIA for immediate investigation.
If the CFIA determines that CWD may be a cause of disease, the animal(s) will be ordered destroyed.
A confirmed positive CWD case triggers the CFIA’s CWD disease response. Response actions depend on whether a herd is enrolled in a VHCP. Only herds that are enrolled in a VHCP and compliant at level D or higher are eligible for the CWD VHCP disease response Herds that are not enrolled in a VHCP will be placed under initial movement controls and restrictions on movement of live cervids, cervid products and by-products into the marketplace. In addition, the CFIA will investigate trace-in and trace-out animals. Provinces and territories may have their own disease control requirements and measures.
Owners whose animals are ordered destroyed may be eligible for compensation.
Why has the CFIA changed its CWD disease response?
Since the CFIA's original CWD eradication program started in 2000, the North American CWD picture has changed dramatically. Wild and farmed cases of CWD have continued to increase despite the CFIA’s aggressive attempts to eradicate it. A significant re-occurrence rate has also been seen in Canadian herds that were previously depopulated, cleaned, decontaminated, and permitted to re-stock. This led to a program review and to the ultimate conclusion that eradication measures, using quarantines and stamping-out actions in areas where the disease is endemic in wild cervids, are both ineffective and unsustainable. Based on all available information, a decision was made to switch from an eradication policy to one of control.
The CFIA's new disease control program is based on the OIE (World Organisation for Animal Health) concept of compartmentalization. Compartmentalization identifies a group of animals having a distinct health status based on biosecurity management and husbandry practices. Herds enrolled on a VHCP and compliant at level D or higher are considered to be the compartment for CWD in Canada.
Only a few viable tools exist to deal with CWD. As a result, disease prevention is the most effective control measure. By participating in a VHCP, individual producers mitigate the risk through immaculate inventory control, rigorous herd testing, restricting herd entry to cervids at a similar or higher VHCP level, and enhanced on-farm biosecurity measures. Promoting compartmentalization in the national disease response program supports producers who are taking measures to keep CWD out of their farm.
To learn more about CFIA's CWD disease response, please consult what to expect if your animals may be infected.
To learn more about the implementation timeline of the CWD disease response program, please consult the notice to industry.
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