About a month ago a good friend from Alberta forwarded me an article he found written by Angus M. Thuermer Jr., reporting on a a study on Chronic Wasting Disease (CWD) in Wyoming. CWD is an infectious disease known to occur in white-tailed deer, mule deer, moose and elk. It’s part of a family of diseases known as Transmissible Spongiform Encephalopathies (TSEs) where the infectious agent is thought to be a malformed protein known as a prion. Prions are not a bacteria nor are they a virus; they are a very strange and poorly understood entity. There is a human form of TSE called Creutzfeldt-Jakob Disease (CJD). To date, no humans are known to have contracted CJD from a CWD infected animal, although there is a variant CJD people have got from eating cattle infected with Bovine Spongiform Encephalopathy (BSE), another TSE. CWD is thought to have originated from Scrapie, the TSE sheep can be infected with.
CWD is a large and growing concern in North America because it’s a relatively new disease (the first known occurrence was documented in the latter part of the last century), it’s spreading and it’s wreaking havoc to deer herds in some areas. There’s no known cure for the dsease and once an animal contracts it the end result is always death. It’s spread into the area of Alberta where I hunt so it’s a particular concern for me and my hunting partners.
Thuermer Jr.’s article said that a study by a University of Wyoming doctoral student Melia DeVivo led her to believe the mule deer herd she was studying could potentially become extinct because of CWD in 41 years. The herd numbered some 14,000 in the early 2000s but had dwindled to half that in about a decade.
There was a lot of information in the article, but a couple of factoids were most interesting. One was that researchers found that deer with different genes react differently to CWD exposure; a key gene found with three combinations of alleles can make a deer up to 30 times more likely to be CWD-positive, depending on which genotype the deer is. That’s good news, because it suggests that over time, it’s possible if not probable that deer herds will become dominated by CWD resistant strains of deer (however, as the researchers point out, the strains that are resistant seem to be relatively rare, which might mean they might not be ‘good’ for the survival of deer in other ways; e.g., deer with the resistant strain might be bad mothers). Still, I think the news there are CWD resistant deer is very good news indeed.
The other good news is that studies have shown that free-ranging elk don’t seem to get high rates of CWD infection, unlike mule deer – and penned or ranched elk. No one seems to know why that is the case. Plus, in 2002, a penned elk herd of 39, purposely exposed to CWD, had all withered away and died or been put down within 10 years – except for a lone cow nicknamed Lucky. Apparently she’s still alive, doesn’t look sick, doesn’t test positive for CWD and has had a calf. So it looks like elk also have natural, genetic or other resistance to CWD.
Interestingly, the area I hunt in Alberta where CWD is problematic in mule deer, also has free-ranging elk (that’s one of them in the photograph) – that haven’t as yet, at least as far as I know, tested positive for CWD. That would seem to be consistent with what researchers have observed elsewhere.
To date, the results of the studies Theurmer Jr. reported on have not been published in refereed journals. That needs to happen; otherwise, these important findings risk being dismissed as mere speculation or musings.
CWD is a terrible disease likely to get much worse before it gets better. For a long time, all the news about CWD was bad. But now there at least appears to be a glimmer of hope that all will not be lost.
And that’s a good thing.