Chronic wasting disease continues to expand westward threatening deer populations

Chronic wasting disease affecting Alberta deer Officials are finding deer infected with chronic wasting disease further west than ever before. Bill Macfarlane reports.

Calgary — Alberta recorded an all-time high number of cases of chronic wasting disease (CWD) in 2019, finding infected deer further west than ever before.

Mandatory testing of deer heads from hunters last year turned up 1,158 cases of the fatal neurological disease, similar to BSE or 'mad cow disease.' The findings from last year alone now make up more than 43 per cent of all CWD cases on record since 2005.

The disease is caused by a misshapen protein called a prion. Deer shed them into the environment, mainly through saliva, urine and feces.

After an unknown amount of exposure, deer begin a fatal cycle that changes their healthy prions into diseased versions.

“It’s not just necessarily the spinal cord or the brain stem that have prions, it could be all parts of the deer that could be shedding prions, some could be shedding more than others,” said Matt Besko, director of wildlife for Alberta Environment and Parks.

For much of the infection, the animal will appear healthy. But it is always fatal and the final days of the deer’s life is spent in a stupor, severely emaciated and unable to move far.

It is one of the only wildlife diseases believed to be capable of causing long-term drops in populations.

“We’re starting to see prevalence rates in some units amongst male mule deer of around 30 per cent and that causes us a great deal of concern,” said Besko.

While CWD could cause a dramatic drop in deer populations, there is no treatment for it and the only effective way to slow its spread is by killing off deer in some areas to protect healthy populations in others.

The province suspended a helicopter cull program in 2008 after public outcry and has been only monitoring the disease ever since.

Now new cases have been found in the Calgary Zone, as well as nine other provincial Wildlife Management Units (WMUs) — pushing potential cases right against the foothills of the Rockies.

“We want to be able to determine how quickly and to what degree CWD is progressing on that western edge,” said Besko.

Besko says AEP is in discussions to come up with a plan to contain CWD that could include hunter-led culls in some WMUs — a move that is likely to be unpopular with both hunters and animal rights advocates.

CWD is also a food safety issue. Hunters are legally required to eat the meat from any animal they kill, unless it tests positive for the disease. There are no known cases of humans contracting the condition, but Health Canada research suggests that it is possible.

You don’t have to eat wild deer to come in contact with the prions responsible either -- they are extremely durable and could potentially survive on any agricultural crop that has been fed on by infected wildlife.

In recent years it can take more than three months for hunters to get CWD test results back. If the animal tests positive, it’s recommended the meat not be eaten.