As new questions are raised over the risk to humans of chronic wasting disease carried by deer, researchers are scraping for data on the health of herds in Wisconsin.
The Canadian Food Inspection Agency conducted a study in which it exposed monkeys to meat from CWD-infected animals. The results, released this summer, suggest the disease may be more contagious than previously thought, though what that means for Wisconsin hunters is unclear.
“That’s the $64,000 question,” said University of Wisconsin veterinarian and Wisconsin Veterinary Diagnostic Laboratory outreach coordinator Keith Paulsen. “Really what it shows us is that we don’t know enough about this disease and the argument that ‘This has been around forever and has never been a problem’ is really short-sighted. And this is new information that it could affect more than just one species and we need to know more.”
Chronic wasting disease is a spongiform encephalopathy, meaning a disease caused by a prion, a protein that is neither a bacteria or a virus, and can survive exposed to the elements outside of a host animal.
The Wisconsin Department of Natural Resources warns hunters that the disease has been found at a higher rate in southern Wisconsin and should take precautions when taking animals for game meat. Estimated infection rates have been developed based on positive tests in Wisconsin labs, but those numbers are flawed, particularly since 2015 with the widespread use of remote animal registration by phone.
“It’s not a random sample; it’s convenience,” Paulsen said of the system in which hunters are advised to have animals tested if they show strange behavior or if meat is suspicious, skewing samples toward animals appearing to already be sick, coming from areas already known for the presence of CWD.
In 2016, the WVDL’s total tally of tested animals included about 8,500 white-tail deer from Wisconsin. This is from a population of animals taken estimated upwards of 100,000.
“Nobody really knows, on the public side, what the prevalence is or what is going to change to make personnel in Wisconsin to say, ‘Yeah, we need to spend more time or money on it,’” Paulsen said. “What we are saying now is that testing is free and we would really like to know more and if you have any questions, here are your resources. If you can’t get your deer tested at a sampling site for gun season, here are your options.”
“It has been increasing over the past few years as people become more educated about CWD and becomes less of a factor in processing venison,” said Larry Clark, president of the Lodi Sausage Company and Meat Market. “We process whole deer and people bring us a lot of trimming material to make sausage too.”
Although CWD has not stopped the company from dealing in venison, there have been precautions put in place when handling the 600-700 deer it handles each year.
“We do our deer at the end of the day after we have done all of our other animals and cleanup,” Clark said. “And during the rifle season, we shut down our beef and pork and just do deer for 10 days.”
“Actually, we at this point are not requiring that people show that they have had them tested,” said Ginny Wyttenbach of Wyttenbach Meats in Prairie du Sac. “We saw the article in October, so our sausage maker takes all the venison that looks bad or doesn’t look clean and throws it away. At this point, it’s not an issue.
“We have a meat inspector here six days a week, so that’s never been an issue for them. And let me tell you, they’re looking at everything else. With venison, it isn’t a for-sale product unless venison is raised on a registered deer farm.”
“We don’t have any regulatory authority over the processing of venison,” said Raechelle Cline-Belli, spokeswoman for the Wisconsin Department of Agriculture Trade and Consumer Protection. “The only authority that we do have is related to making sure that the processing of venison is separated and cleaned prior to processing red meat.”
When game does come in contact with commercial production, state regulations require that a processor go through a process of a dry cleaning period, a rinse, wash, another rinse and sanitizing.
“It’s a time-consuming process to go through all that cleaning and that’s why many meat establishments shut down their red meat processing during deer season, because they don’t need to worry about switching back and forth,” Cline-Bell said.
She said the department does not track the numbers of venison processors. “It’s primarily because all the venison is processed for the consumption by the hunter and that hunter’s family and not sold on the open market,” Cline-Bell said.
The WVDL’s Paulsen agreed with an oft-cited response among those who continue to process venison that risk is significantly lowered by the fact that brain, lymph and spinal tissue is typically avoided. To what degree that risk is lowered has yet to be determined, but according to Paulsen, it is not zero. More research, more data and more tested deer are needed, he said, to determine what that risk actually is.
Adding yet another layer of complication to this search for clarity is that the prions that cause chronic wasting disease do not simply arrive and kill the animal, but lay dormant before the animal begins to show symptoms. In the case of elk, it can be five years and in white-tailed deer more toward two years.
“If the prevalence of the disease reaches a certain point, the population won’t survive,” Paulsen said, briefly taking the personal food safety question out of the equation. “A study out of Colorado suggests that with elk, once prevalence reaches 40 or 50 percent, it will wipe the whole herd out and we don’t know what that is in white-tailed deer.”