Chronic wasting disease (CWD) is a fatal, infectious disease of deer, elk, reindeer and moose (cervids) that affects the central nervous system. Caribou, a subspecies of reindeer in Canada, can likely also be affected. An infected cervid may appear normal for several years before it develops changes in behaviour, such as weight loss, poor co-ordination and other signs before it dies. Infected cervids are also more prone to being killed by other means such as hunting or vehicle collisions.
CWD is a prion disease in the same family of diseases as scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle (also known as "mad cow disease") and Creutzfeldt-Jakob disease in humans. Prions are infectious abnormal proteins that accumulate in the brain and other tissues.
CWD Discovery and Spread
CWD was first identified in a wildlife research facility in Colorado in the 1960s, but was not identified as a scrapie-like disease until 1978. The disease was subsequently found in wild deer in the same area. It is speculated CWD was derived from a mutation of scrapie, which existed in the area, or the CWD prion was caused by a spontaneous mutation within a cervid.
CWD has now been found in Saskatchewan, Alberta and 24 states. The National Wildlife Health Centre’s CWD map shows affected farmed cervid herds and general regions where CWD is in the wild. CWD has also been found in South Korea and, more recently, Norway.
For additional information on CWD in Saskatchewan wild cervids, see the Canadian Wildlife Health Cooperative's CWD page. CWD has been detected in wild cervids throughout most of the western and central portions of the province, as well as the northeastern areas around Nipawin and Carrot River. However, testing has been limited and CWD may also be present in other areas.
CWD was likely brought into Saskatchewan through the importation of infected elk from South Dakota in the 1980s. The disease was first detected in a Saskatchewan farmed cervid in 1996 and in wild cervids in 2000. It has since spread to other areas of Saskatchewan through farmed and wild cervids.
CWD and Human Health
A human case of CWD has never been identified, but transmission to humans cannot be excluded. Preliminary results of a recent experimental study show that macaque monkeys, which are closely related to humans, developed the disease over time when fed muscle meat from CWD-infected deer that appeared healthy. The study is ongoing and the results will be subject to scientific peer review.
As a precaution, Health Canada and the World Health Organization recommend that people not eat meat or other parts of a CWD-infected animal.
The Government of Canada conducts national surveillance for all human prion diseases, and reviews and monitors CWD-related scientific literature. It will provide updated recommendations and positions as new scientific evidence indicates.