ST. PAUL — As bowhunting season officially opened this past weekend, hunters in CWD hot zones are checking regulations and figuring out where to drop off the head and neck of their deer for testing.
CWD, or chronic wasting disease, is a contagious, fatal neurological disorder affecting deer, moose, caribou and reindeer. Since its discovery in 1960, those in the hunting industry have watched it spread despite multistate efforts and millions of dollars in aid.
The science is making progress, but tracking and stopping its spread has required cooperation with hunters who struggle with the inconvenience of getting the necessary lymph nodes from their catch to the few drop sites while they are still viable.
What’s needed is a faster, easier testing method, something the University of Minnesota hopes to develop in two years.
The newly formed Minnesota Center for Prion Research and Outreach (MNPRO) within the College of Veterinary Medicine, is the school’s first step in developing real-time diagnostic tests to help stop the contagion.
“You don’t have the luxury of time to wait,” said Lou Cornicelli, wildlife research manager at the Minnesota Department of Natural Resources, about the continued contamination that takes place between the kill and the test results. “Waiting is a bad idea.”
A complex disease
At a recent talk at the Bell Museum in Falcon Heights, Dr. Roxanne Larsen, a University of Minnesota biologist, held up a multi-colored plastic Slinky, letting it spring gently in her hands.
“This is a normal protein,” she explained.
CWD attacks microscopic proteins, which actually look like little springs, and causes them to fold unnaturally.
To demonstrate, Larsen folded the Slinky in on itself, tangling it into a bundle.
“It can turn into a very different shaped protein,” she said. “It no longer functions like it normally should in the animal.”
Once folded, the proteins, called prions, turn into contagious pathogens that recruit any other prions they come into contact with, grouping together in clumps that eventually destroy the animal’s brain.
Unlike a virus or bacteria, a prion is not easy to detect and it can take up to two years before enough prions build up in the animal’s brain to cause death.
“(The deer) don’t turn white or black or gray when they get sick; they look like any other deer,” Cornicelli said.
Prions are not alive, contain no DNA, and can survive being boiled and treated with disinfectants. For this reason, they are especially concerning to meat processing businesses.
With no known cure, scientists, such as those involved with MNPRO, are focusing on early detection and containment.
Since 2016, 37 cases of infected deer have been confirmed in Minnesota.
Testing is cumbersome
In June, the state approved funding the University of Minnesota’s project, granting more than $1.8 million from the Minnesota Environmental Trust Fund to support the development of a rapid and reliable diagnostic test for CWD. The project also received about $200,000 from the Rapid Agricultural Response Fund.
The University currently tests for CWD in deer farms, a laborious process that takes up to two weeks to get results.
The lab receives the animal head, surgically removes the lymph node, soaks it in formaldehyde for five days, uses a $200,000 machine called a designated stainer to flag and dye folded prions, and then requires a technician to study the samples, looking for evidence of the disease.
“I’d love to take a sample at a deer farm and know today that, yes this deer tests positive,” said Jeremy Schefers, an assistant professor who runs the CWD testing lab. “Practically, if we’re going to measure this disease, we need better tools; we need quicker tools.”
The DNR sends its samples of wild deer to Colorado for a three-day turn-around. Colorado was one of the first states that discovered the disease and is further along in development.
Minnesota’s testing is “all based on technology designed decades ago,” said Dr. Peter Larsen, assistant professor in the College of Veterinary Medicine who leads MNPRO, a group of 12 to 15 core faculty studying CWD.
The group’s proposed tool would use flow cells, which are used in Alzheimer’s and Parkinson’s disease research in humans. And the handheld device would detect CWD prions in samples of blood, saliva, urine or deer droppings, rather than just lymph nodes.
The microfluidic flow cells are small glass “chips” that can hold thin lines of fluid from different sources in order to view multiple specimens at a time under a microscope.
Hunters' help needed
In the meantime, hunters will need to check the regulations to know which areas have tested positive for CWD. If they get a deer within those areas, the hunters are required to get them tested. There are currently four control zones, most in southeast Minnesota.
Cornicelli said once a deer tests positive, the DNR draws a 15-mile circle around the area, hoping to create boundaries to contain CWD.
“We’re trying to avoid this,” he said, putting up a map of Wisconsin whose southwestern counties are riddled with CWD positives.
“What they’re seeing is a massive increase in prevalence over time because they have taken a passive approach,” he said. “Our Legislature has taken this (CWD) seriously for a very long time.”
It’s taken a toll on hunters and those in the industry.
“I think it was handled poorly,” said Brian Bengry, a hunter from Iowa County, Wis. He’s had eight deer test positive in the past 10 years.
Scientists say there is no known case of CWD transitioning to humans. But the fact that bovine spongiform encephalopathy, also called “mad cow” disease, another prion-type contagion, did transfer to humans, has hunters concerned.
“I have gotten all my deer tested for CWD since it gained attention, but I then have a meat processor do the processing,” he said. He’d been told the meat he gets back is the deer he shot, but learned later that some meat, such as hamburger, sausage or brats can be a combination of his deer and other deer.
“Even if you test for CWD, you get contamination anyway,” he said. “We no longer eat the venison, but donate it.”