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, black-tailed deer, moose and elk.
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 affect members of the deer (cervid) family.
Is CWD a risk to human health?
At this time there is no scientific evidence to suggest that CWD in deer and elk can be transmitted to humans. However, it is recommended that any tissue which may have come from a CWD-infected animal not be used or consumed by humans.
Measures have been taken at both the federal and provincial levels to reduce human exposure to products potentially contaminated by CWD by preventing 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 and in captive cervids in South Korea.
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 incubation period can last from 16 to 36 months.
There is no 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?
A CWD disease control and eradication policy was implemented by the Canadian Food Inspection Agency (CFIA) in October 2000. Ongoing provincial surveillance, which has detected the recent cases, varies with each particular province’s perceived threat and infection status. Testing is mandatory in Manitoba, Saskatchewan, Alberta and the Yukon; it is voluntary elsewhere.
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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