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, elk and reindeer.
CWD belongs to the family of diseases known as transmissible spongiform encephalopathies (TSEs). Though it shares features with other TSEs, such as bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep, it is a distinct disease known at this time to only 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. However, 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 and, in areas where CWD is known to exist in wild cervids, providing warnings and precautions to 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 except for acute pneumonia. Animals are usually three to four years old before clinical signs appear, but signs have been seen in animals as young as 18 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 and Norway.
CWD was first detected in Canada on a Saskatchewan elk farm in 1996. The disease has been routinely detected in Saskatchewan, with a few cases in Alberta.
How is CWD transmitted and spread?
Both direct (animal-to-animal) and indirect environmental (animal-to-premises-to-animal) transmission occurs in cervids. It is believed that direct transmission occurs via shedding of the infectious agent in saliva and feces. The average incubation period can last from 16 to 36 months.
There is no direct evidence that CWD-affected deer and elk can transmit the disease to other species.
How is CWD diagnosed?
CWD is tentatively diagnosed based on clinical signs, but is usually confirmed by testing of tissue from the affected animal after it is dead.
How is CWD treated?
No treatment is available for animals affected 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 and Yukon are required by provincial/territorial law to be tested for CWD. This applies to federal, provincial and territorial abattoirs in those provinces. Only carcasses that test negative are used for meat in AB, SK, MB and Yukon.
Some provinces and territories offer testing services to hunters if they choose to have their carcasses tested for CWD. If members of the public have concerns, they should contact the provincial or territorial officials where they live.
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 include mandatory testing and limits on what animals may be added to the herd.
The CFIA sets the national standards, provides oversight and audits the third-party administrators of the VHCP. In 2015 and 2016, the CFIA consulted with stakeholders regarding enhancements to the VHCP, and new updated national standards have been developed.
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 by inspectors.
The CFIA quarantines all herds in which an animal tests positive for CWD and tracks the movements of animals onto and off of the affected premises. Exposed animals are usually destroyed.
Owners whose animals are ordered destroyed may be eligible for compensation.
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