It took over six weeks before I found out that the mature mule deer buck I harvested in SE Alberta was ‘fit’ for human consumption. SE Alberta has Chronic Wasting Disease (CWD) in its deer herd, and testing of hunter-killed deer for the presence of CWD is mandatory. While mine was OK, one of the 4 deer in total our party took (another adult buck) did have the disease. That was quite a shocker.
CWD is one of a family of diseases that are referred to as transmissible spongiform encephalopathies, also called contagious prion diseases. Other diseases in this family include so-called ‘mad cow’ disease (BSE), scrapie and Creutzfeldt-Jacobs, which occurs in humans. These are all brain degenerating diseases, with no known cure. The suspected causative agent of these diseases are prions, which are abnormal, very poorly understood, cellular proteins.
While I was waiting for the results of testing on my mule deer – a CWD infected deer is not recommended for human consumption, although no cases of transmission of the disease from deer to humans has been recorded – I spoke with Dr. Margo Pybus with Alberta Environment and Sustainable Resource Development. Dr. Pybus is the go-to expert in Alberta on CWD.
We discussed the disease, and I asked Dr. Pybus what she knew about the role of natural predation, and whether predators like wolves might help contain the disease. Dr. Pybus referred me to Dr. Michael Miller, who works at the Colorado Wildlife Research Center.
I contacted Dr. Miller and he provided me with a couple of published research papers that suggested cougars could detect a deer infected with CWD, even in early stages of infection. Although predation rates by cougars on CWD infected deer was found to be as much as four times that on non-infected deer, there did not seem to be any impact with respect to halting the spread of the disease.
All the deer species are believed to be susceptible to CWD (infected mule deer, whitetails, moose and elk have all been recorded – no caribou has been found with CWD, but experts think the disease just hasn’t spread yet to areas where caribou range). Every individual that become infected with CWD dies. In some areas of the USA, up to 40% of the deer are walking around infected with this disease. Where the disease is prevalent, the deer population – to date – always declines.
CWD continues to spread – relatively slowly – but there is no indication that it can be eradicated from an area once established. If detected early, concerted efforts at reducing the local deer population seems to have prevented new loci from being established.
The only other good news about this disease is that humans, as yet, don’t seem to get it. And one would have to assume many hunters have eaten CWD infected animals, given it’s now widespread distribution in western USA and Canada.