Chronic Wasting Disease has made more headlines and garnered increasing attention in recent years as a significant concern for wildlife management and public health - especially among deer hunters. But how long has this disease actually been around? The answer is actually a long time - perhaps even longer than we know.
Discovery of Chronic Wasting Disease
CWD was first formally identified almost 6 decades ago in the late 1960s in captive mule deer at a research facility in Colorado. Initially, it was mistaken for a form of scrapie, a similar disease found in sheep. However, further research revealed that CWD was a distinct prion disease affecting cervids, including deer, elk, and moose.
Spread and Evolution of CWD
Since its discovery, CWD has spread across several regions in North America, affecting both wild and captive cervid populations. CWD is now present in 32 states (that we know of) in all regions of the United States, and on both coasts.
History of Testing for CWD
Testing for CWD has evolved significantly over the years. Initially, diagnosis relied on post-mortem examination of brain tissues, which limited the ability to detect the disease in live animals. However, advances in testing methodologies, including the development of rapid diagnostic tests and the use of lymphoid tissues for detection, have improved our ability to identify CWD in both living and deceased animals. It’s a great advancement, however the vast majority of testing today still occurs post-mortem.
Until about 20 years ago, there was very little CWD testing at all. It existed, but not with any scale, and it really wasn’t done unless there was a suspected CWD positive deer. In the last 5 or so years, many states have drastically increased their volume and reach in their CWD testing protocols.
A Critical Correlation
When looking at the areas with CWD vs. those without, and doing the same analysis on testing, there seems to be a pattern. We contend that the policies and strategies around testing - especially on a state-by-state basis - is directly correlated to which states “have” CWD and when they got it. My dad never got Covid-19. It just so happens he also never got tested for it any of the times he was sick. This is the approach some states are taking as well.
Should it be any wonder that when states started testing programs for CWD, that seems to be right around the same time when CWD “spread to their state”. It turns out you can’t detect something you don’t test for. Now that the majority of states have robust testing procedures in place and are testing thousands of deer, positive results are coming in in most of them. Does this mean it’s spreading? Or has it actually been around forever and we’ve just never known it?
For example, Nevada is CWD-free (to the best of our knowledge). However, to date, they’ve tested a tiny percentage of the number of deer that other states like Wisconsin do. When Wisconsin tests 20,000 deer and Nevada tests 270 deer, is it a big surprise Wisconsin had positives and Nevada didn’t? With Nevada looking to ramp up its testing program this year though, we’ll see if they can still wear that “CWD-free” badge for much longer. Call me doubtful.
Why Does It Matter?
Knowledge of how the disease spreads, how and when it was introduced to populations, and a history of the disease is crucially important in crafting policy to control it. Laws are being passed and regulations are being put in place based on what we think we know about the spread and effects of the disease. The running assumption of the DNR and most wildlife agencies is still that the disease is “100% fatal” and “extremely contagious”. However, if CWD has in fact been around a lot longer than we think, it challenges both of those narratives and would call into question the effectiveness of many of the common management and control strategies.
