July 13, 2021
Commonly (and wrongly) referred to as the zombie deer disease, chronic wasting disease (CWD) is a very real and serious threat, unlike mythological corporeal revenants. One thing the two have in common, though, is that both are undead, meaning that the disease isn’t alive or dead. It just exists. That’s crazy, but more on that later.
After consulting with dozens of wildlife biologists and other leading authorities on CWD, we’ve come to the conclusion that CWD is quite mysterious, a tremendous threat, poses very real problems to cervids, and could end hunting as we know it.
In this two-part series, we’ll explore the history of CWD, how it’s affecting deer hunters, what state wildlife agencies are doing to mitigate the effects of CWD and what the future holds for deer and deer hunting.
The History of CWD
Those unfamiliar with CWD should understand that it’s an always-fatal disease located within the nervous system of many cervids. Deer, elk, moose and reindeer are capable of contracting the disease. And according to the CWD Alliance, it’s transmitted through direct animal-to-animal contact, as well as carcass parts, feces, and saliva. To date, it’s known to exist in 26 states ranging throughout the nation, four Canadian provinces, Norway and South Korea. In some, it’s in captive herds only. In others, it’s also amongst wild cervids.
While this disease is not caused by bacteria or viruses, it is part of the family called transmissible spongiform encephalopathies (TSEs). A misfolded prion, called a prion, resists being broken down by the body as is normally done. Then, when these misfolded prions enter a healthy cervid’s body, the process starts over, replicates, and the animal’s health declines.
Currently, there is no known cure for CWD. It’s untreatable, and once contracted, always fatal. Sadly, the CWD Alliance reports that is has a population-level impact once the prevalence rate in a herd exceeds 27%.
“The disease starts to kill nerve cells with leads to encephalopathy, or holes, in the brain. The best laymen description I've heard for CWD is transmissible spongy brain,” said Tyler Harms, biometrician for the Iowa Department of Natural Resources. “Once these holes start to develop in the brain, it affects the behavior of the deer including its ability to feed, which ultimately leads to emaciation, excessive salivation, excessive urination, and loss of control of body movements and fear of humans. Ultimately, the disease results in death 100% of the time. Once CWD takes hold in a population, it consistently increases in prevalence (the number of deer infected in a population) and geographic spread, and once prevalence levels reach greater than or equal to 50% of the population, research has demonstrated an annual population decrease of 10%. CWD is a non-discriminative disease, meaning it infects and affects all animals the same.”
But where did it come from? No one really knows with certainty. But Brian Murphy, a wildlife biologist with HuntStand, says it was first described in 1967 at the Colorado State research facility. He says that facility had a prior history of housing sheep in the same location as they housed deer.
“The TSEs — of which scrapie is one, mad cow, CWD, etc. — that family of prion diseases is known to mutate and occasionally jump species,” Murphy said. “But we don’t know, and likely will never know, where CWD came from. I think the prevailing theory is that it mutated from scrapie in sheep. But the bottom line is it really doesn’t matter.”
CWD and Cervids
It doesn’t matter because it’s already impacting cervids, regardless of how it originally spread to them. According to Kip Adams, chief conservation officer with the National Deer Association (NDA), there is no cure or vaccine yet. It’s continuing to spread and impact deer herds.
Granted, many people — and even some scientists with special interests — will tell you that CWD is no threat to whitetails and other cervids. They’ll say it’s all a political sham. That just isn’t the case.
“At the highest level — both in mule deer and whitetails — peer-reviewed research shows where there is a long history of the disease that it is affecting population-level dynamics,” Murphy said. “We’re seeing long-term effects. Unlike where it’s newly discovered in an area, it doesn’t typically have population-level impacts. Instead, it affects a few individuals if they live long enough to die from CWD and not to some other mortality cause.”
Of course, variables include how long the disease has been in a deer herd and the age structure of it. If the deer generally reach older age classes, and the disease has been there a long time, the prevalence rate will be higher and will start being the cause of death, effectively having a population-level effect. But if it’s relatively new to the area, both bucks and does are heavily harvested, and the age structure is lower, then it generally isn’t a common cause of death.
The Money Conundrum
So while it isn’t sucking the life out of most deer, yet, it is draining the life out of budgets.
One of the biggest hurdles researchers and state-level biologists are facing is having the funding necessary to do their jobs. And when money for CWD is limited, it has to come from somewhere.
“It concerns me how much money the state agencies have to divert to CWD and what that takes away from what they can do for hunters and landowners,” Murphy said. “Those dollars have to come from somewhere. It comes from staff, programs, food plots, and wherever it has to in order to fill that gap. In most cases, stage agencies that are dealing with CWD are spending millions of dollars.”
Unfortunately, this is generally not extra state-appropriated funding. It isn’t coming via federal support, either. The USDA greatly reduced available dollars, especially since 2016.
Some Regulations Help More Than Others
While money is a problem, so are some bad practices that are still being done, including moving animals. One aspect of limiting the transportation of live cervids is the captive industry, and that’s a hard thing to control. Sure, regulations are in place, but these aren’t enough. Take Texas, for example. It is already very regulated, but the current system isn’t doing a good enough job. CWD keeps spreading and showing up in new locations.
The emergency rule just passed by Texas Parks and Wildlife was because CWD was discovered in a couple of captive deer herds that had moved nearly 1,800 deer to 151 other breeder facilities and 101 release sites in 95 counties," Murphy said. "Prior to 2016, release sites could include low-fenced sites. However, regulations passed that year restricted future releases to high-fenced enclosures. However, significant risks remain. Deer fences are not deer-proof. Trees, storms, floods, and vandalism are potential avenues for escape. Also, evidence suggests that CWD can spread between fenced and unfenced deer herds via saliva, urine, and feces.
In Texas, the deer breeding business is a multi-billion dollar industry. Naturally, it has a lot of power and political weight. Still, it needs monitoring and keeping in check. That’s why Murphy was among 40 wildlife experts who pushed for this new emergency ruling which further curtails the movement of deer, if only temporarily.
On the flip side, some point to wildlife agencies and DNRs as culprits of moving live cervids, too. Did wildlife agencies and DNRs spread CWD when restocking their herds? In most cases, the likelihood is very low.
“Looking at the pattern of disease spread since we first recognized it in the 60s, the vast majority of states had already restocked their herds by then,” Murphy said. “What we’re seeing based on the spread of disease — almost in every instance — is that it hadn’t been there that long. It couldn’t have been there for 50 years or we’d have a much wider spread, because we can measure that.”
There is one exception, though — Arkansas. When it was first discovered a few years ago, the infection rate was already over 20%, which is incredibly high.
“That particular area does have a history,” Murphy said. “The state of Arkansas went out West, got some elk, and brought them in. There’s a possibility that introduction of elk is behind that [pocket] of CWD. I don’t think we’ll ever prove that, but there’s some anecdotal, back-of-the-napkin research that makes it a distinct possibility.”
Furthermore, Murphy says we’re not out of the woods yet elsewhere. Some states are still relocating both elk and mule deer. He believes some state programs should be challenged, and that they should ensure animals they are moving — if they move them at all — are CWD-free.
While regulating and limiting the movement of live and dead deer is the most important things state agencies and DNRs can be doing, there are other things in play that states are attempting to do, such as outlawing the use of deer urine.
According to Murphy, banning the use of scents and lures is a “mixed can of worms.” He and Adams believe the return on investment for such a policy is very low, and time would be better suited on other things.
“The likelihood of a deer contracting CWD from urine is so low that I’d prefer state wildlife agencies spend time and resources stopping the more likely routes of transmission – stop moving live deer and the high-risk parts of harvested deer,” Adams said.
“There’s good data that would suggest that it’s not impossible, but it’s highly unlikely,” Murphy concurred. “It’s probably not going to make much difference in CWD spread, but I do recognize it’s something a state agency can do.”
Murphy is glad the scent industry has created numerous synthetic options, though. Using these bypasses this concern. Also, he says the biggest and most important players within the scent industry have joined the Deer Protection Program, which helps make sure their products are CWD-free.
Ultimately, he thinks that some states that have banned the use of urine have “gaping holes” in their policies, especially involving captive deer and the movement of deer carcasses. So, while their efforts to ban urine might be in a good faith attempt to battle CWD, energy would be better spent elsewhere along the front.