From the CFIA site.........
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.
https://www.inspection.gc.ca/animal-.../1330190096558