Can We Breed Our Way Out of CWD? Oklahoma Wants to Try.

Update (5/1/2024): The full Oklahoma legislature passed this bill and sent it to Governor Kevin Stitt on May 1, 2024. Concerned Oklahoma residents should contact the governor and voice their opinion.

The Oklahoma state legislature is rapidly advancing a first-in-the-nation bill that would allow captive-raised whitetail deer to be released onto the landscape if they possess CWD-resistant genetic markers.

Dubbed the “Chronic Wasting Disease Genetic Improvement Act” (HB 3462), the measure received near unanimous support in the Oklahoma state house and most recently passed a senate committee on a 10-0 vote.

Its rapid progress indicates the excitement some biologists and hunters feel about the promise of eliminating chronic wasting disease via selective breeding. Others aren’t so sure.

“There is no credible wildlife professional who works with wild deer that I know of who agrees with this,” Kip Adams, chief conservation officer for the National Deer Association (NDA), told MeatEater. The NDA has come out in opposition to HB 3462, and Adams worries it will catalyze further CWD spread in the state.

“This would open the floodgates to move live animals, which is just terrible,” he said. “It’s bad enough to move to another high fence operation where wild deer can make nose-to-nose contact. Taking that deer and putting it into the wild is a whole other layer of risk and idiocy.”

The Proponents

Proponents for the Oklahoma bill–and for breeding CWD-resistant whitetail more generally–rely heavily on the experience of sheep farmers and their fight against a disease called scrapie. Like CWD, scrapie is a fatal, degenerative disease, and it affects the central nervous system of sheep and goats. Though the agent responsible for the disease has not been completely characterized, the most widely accepted theory is that, like CWD, it’s caused by an infectious protein, or prion.

Farmers have been fighting scrapie for centuries, but in recent decades, the National Scrapie Eradication Program has reduced the prevalence of scrapie by about 85% in the U.S. Part of the program includes genetic testing to identify high-risk animals and breeding programs that seek to create scrapie-resistant sheep.

Deer breeders hope a similar strategy can be used to reduce the prevalence of CWD. In 2020, Dr. Christopher Seabury, an associate professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences, released a paper that identified what he said were the genes that predict whether a deer will be more or less susceptible to CWD (PRNP codon 96 (G96S), for you geneticists out there).

“One of the most important things from this initial study is the mean genomic prediction accuracy, which hovers around 81%,” Seabury said. “This means that we can predict with about 81% accuracy the phenotype of a tested animal, and that we can accurately estimate the genetic merit of each animal, as it relates to CWD, by producing something called genomically-estimated breeding values.”

The theory goes that those values can then be used to breed deer that are less likely to contract CWD or less symptomatic when they do.

From there, it’s easy to see how legislators might support something like the “Chronic Wasting Disease Genetic Improvement Act.” Under this bill, a pilot program would be launched that includes several components.

First, the Oklahoma Department of Wildlife Conservation would collect samples from native, free-ranging Oklahoma white-tailed deer to “establish a baseline of average genetic codon markers and genomic breeding values.” The bill doesn’t specify how many deer this would involve, but the bill’s authors have mentioned that 1,000 deer would be tested from 10 regions of the state. This baseline would be used to determine the current resistance level of the wild population.

Then, the Oklahoma Department of Agriculture, Food, and Forestry would determine which deer from captive breeding facilities possessed enough CWD resistance to be eligible for release.

Finally, beginning in February 2026, landowners with both low and high fences would be able to purchase male and female whitetail deer from breeding facilities. The Department of Agriculture would develop the rules governing the program, and the Department of Wildlife Conservation would charge a one-time permit fee to participating landowners.

The bill’s authors have tried to reassure concerned deer hunters that the legislation does not mandate the release of deer. The final paragraph in Section B states that deer “may” be released, which appears to give the Department of Wildlife the option to release deer without requiring them to do so.

“We’re a long ways off from [releasing deer],” Oklahoma Senator Grant Green told a Senate committee last week. “That’s why I left the ‘may’s’ in here, to make sure the science backs this. There’s nobody out there that enjoys hunting whitetails more than me, and I don’t want to jeopardize that.”

The Opponents

Opponents of the bill point out that very little research has been done to investigate whether addressing CWD in wild deer is possible via selective breeding of captive deer. While scrapie was indeed reduced in part through selective breeding, there were a host of additional protocols that worked in tandem with genetic selection, including strict surveillance, culling of infected animals, tagging requirements, and movement restrictions. None of these protocols would be possible among wild deer, and even among captive deer, the comparison isn’t perfect.

“One big fallacy with the analogy is that few livestock models mirror a feedlot operation like deer breeding. And if a sheep rancher had scrapie, there wouldn’t be any releasing or turning any part into profiting. The USDA would depopulate the entire flock and pay indemnity money,” Brian Treadwell told MeatEater. Treadwell owns the Treadwell Cattle Company, where his family raises sheep and cattle in Christoval, Texas.

To illustrate his point, Treadwell sent MeatEater a letter he received from the Texas Animal Health Commission after he dropped some of his sheep off at a sale barn. The letter reminded him that he must have official ear tags fitted to all sheep as soon as they leave his farm. Even though scrapie has been all but eradicated, health officials still strictly enforce the kinds of tagging requirements that many deer breeders oppose.

The business models of the two industries also differ on one important point: ultimately, deer breeders seek to release their stock (or, at least, some part of their stock) while sheep farmers seek to retain it. That makes the comparison between sheep and deer as it relates to disease mitigation far less compelling.

“There is wool involved, it’s just the deer breeders trying to pull it over our eyes,” Treadwell said.

Other opponents worry that releasing deer from captive facilities will invariably lead to introducing more CWD into the wild. The most reliable CWD tests are conducted postmortem, that is, after the deer has died. Antemortem tests are available, but they’re less reliable.

“One of the biggest problems with the captive industry is that there’s not a practical and reliable live animal test,” the NDA’s Kip Adams said. “Deer that are CWD-positive are unknowingly moved from facility to facility right now. This will be catastrophic if those deer are unknowingly moved into the wild.”

Antemortem testing requires taking a biopsy of the tonsil or rectum, which is expensive and time-consuming (not to mention no fun for the deer). But because the incubation period for CWD is 18 to 24 months, a deer that has recently contracted the illness may not test positive.

“With antemortem tests, just as with the postmortem tests, we have problems with false negatives, the sensitivity not being high enough,” Dr. Walt Cook told the Texas Parks and Wildlife Commission in November of last year. Cook is a Clinical Associate Professor in the Department of Veterinary Pathobiology at Texas A&M. “So deer can be positive without us recognizing it because we get a false negative on our tests and so that deer might be sold or moved before we even recognize that the deer had CWD and obviously in a captive situation, that's a problem.”

No one, including Dr. Seabury, claims that deer with CWD-resistant genetics are unable to contract the disease. If those deer are then released into the wild, it could introduce CWD into an otherwise healthy population.

“The longer an infected deer lives, the more contact it will have with other deer, and the more prions it will shed on the landscape,” Dr. Mike Samuel told MeatEater contributor Pat Durkin. Samuel is a professor emeritus in the Department of Forest and Wildlife Ecology at the University of Wisconsin–Madison. “CWD prevalence in that herd would likely go up and you’d get more infections in younger deer. And if that happens, those younger deer would spread it farther and faster when dispersing.”

Seabury has argued that CWD-resistant deer shed fewer prions than normal deer, and so there is less cause for concern. But it’s unclear whether a CWD-positive deer shedding only some prions is a net positive for wild populations if it’s also spreading its CWD-resistant genes.

And that uncertainty lies at the heart of the opposition to this Oklahoma bill. Catherine Appling-Pooler, the director of policy for the NDA, pointed out that the legislation turns Oklahoma’s whitetail population into a “guinea pig.” And it won’t be just Oklahoma’s deer.

“The bill is incredibly vague, and it creates a lot more questions than problems solved,” she said. “Once these deer are released, it’s not just going to impact Oklahoma. It’s going to impact the surrounding states as well as set a precedent for legislation in other states, which is incredibly concerning to me.”

Right now, landowners with low-fence properties are not allowed to purchase deer from breeders. This bill would change that. It would also make Oklahoma the first state in the nation to attempt to use selective breeding to combat CWD in wild populations.

For their part, those wild populations have already weighed in. The CWD-resistant genes identified by Seabury exist in low densities in the wild. For reasons that remain unclear, natural selection has not seen fit to allow those deer to propagate.

“The genotype that they’re selecting for exists in the wild at very, very low frequencies. Mother Nature weeds them out. They can’t survive outside the fence. That reason alone makes it a bad idea to release those deer,” Adams said.

The Way Forward

The Oklahoma legislature might be moving forward anyway. The bill passed the full house on an overwhelming 89-2 vote, and it most recently passed the Senate Tourism and Wildlife Committee unanimously. Appling-Pooler said the bill could go before the full Senate any day, where it stands a good chance of passing.

The bill has garnered high levels of support in part because its authors have claimed that it’s more of an exploratory pilot program than a mandate to release deer. But right now the Department of Wildlife has an interim director, and it’s unclear who will head the agency in two years when deer are allowed to be released. Appling-Pooler worries that policymakers won’t be able to resist the opportunity even if the science says otherwise.

“There’s no ‘shall’ for the stocking program. However, I think when people can, they will,” she said. “And even with the ‘may,’ it sets a precedent and a pathway for this to come to fruition and be established in other states.”

Oklahoma residents can weigh in by contacting their state senator here and the chamber’s leadership here. For everyone else, Adams encourages hunters to continue following the practices we know help slow the spread of CWD–until a more robust solution can be found.

“We have a huge opportunity and responsibility to make sure we’re doing our part to not move the disease, talk to the people we hunt with to make sure they’re not moving the disease either. We have a lot of skin in this game, too,” he said.