By Mark Heinz, outdoors reporter
There’s a glimmer of hope in the results of a wasting disease vaccine test in some Wyoming elk, a wildlife veterinarian said.
Seven of eight captive elk injected with an experimental vaccine showed “some immune response” to Chronic Wasting Disease (CWD), Peach Van Wick told the Wyoming Game and Fish Commission. She’s the Wyoming Game and Fish Department’s assistant state wildlife veterinarian.
That’s good news, but it’s still too early to tell how it might play out, Van Wick said.
“We don’t have any idea whether the immune response means we have any protection (against CWD infection and death in animals),” she said.
Van Wick and Game and Fish state wildlife veterinarian Samantha Allen presented their findings during a commission meeting in Buffalo late Wednesday morning. The commission is charged with setting policy for Game and Fish.
The vaccine trial was done in conjunction with the University of Alberta, Van Wick said. It involved 12 captive elk at the Game and Fish Tom Thorne and Beth Williams Wildlife Research Center. That’s in Sybille Canyon west of Wheatland and northeast of Laramie.
Four elk were injected with low doses of the vaccine, four were given high doses, and the remaining four were used as an unvaccinated control group, Van Wick said. Blood samples were tested at the University of Alberta.
“Notoriously Difficult” Disease
In the elk that had an immune response, “their blood recognized when they were exposed to CWD prions in a laboratory setting,” Van Wick said. “We don’t know how they might respond in a wild setting.”
Prions are malformed proteins that can cause diseases like CWD. In elk, deer and other species, CWD causes fatal nervous system and brain deterioration. Animals in the early stages of infection frequently show no symptoms. In the later stages, infected animals might be emaciated, disoriented and lethargic.
There are so far no documented cases of CWD being transmitted to humans. However, the Game and Fish and the Centers for Disease Control recommend against eating meat from infected animals.
The Game and Fish ordered mandatory testing of hunters’ kills for CWD in several deer hunt around Wyoming this year. https://cowboystatedaily.com/2022/08/22/chronic-wasting-disease-testing-mandatory-in-four-more-wyoming-deer-hunt-areas/
“Prion diseases are notoriously difficult to vaccinate for,” Van Wick said. She noted that the vaccine used in the elk test works by piggybacking on the structure of CWD prions. It’s hoped that will generate a strong enough immune response in elk, deer and other animals to eventually defeat the disease.
If more research proves that the vaccine works, the next challenge will be figuring out how to distribute it among wild herds, she said. Injection would be impractical; some sort of delivery system through food pellets might work.
Bobcat Scat Helps With Research
The vaccine trial was part of ongoing CWD studies at the wildlife research center, Allen said.
Researchers are trying to find ways to track the spread of the disease through predator scat and other means. They’re also trying to find ways to test live animals for infection. Currently, the best method of tracking CWD is to test animals’ lymph nodes after they’ve died or been killed by hunters.
Taking small tissue samples from the ears of live deer might work, and would not cause the deer much pain, Allen said.
“We want to focus on those earlier stages of infection,” she said. “What if we are missing a bunch?”
It also remains a mystery exactly when animals start spreading CWD prions, through urine, feces or saliva. That puts other animals at risk of infection, Allen said.
“It’s incredibly important to know when animals start shedding CWD,” she said. “Does it vary by species?”
To that end, captive bobcats at the research center are being fed ground game meat infected with CWD, Allen said.
“We put dye in the meat, so we can see when they are pooping out the CWD-infected material,” she said.
A similar study using mountain lions at another facility showed that the prevalence of CWD dropped as much as 96 percent in the big cats’ scat, Allen said. It’s not yet clear what the drop is in bobcats.
It’s also unclear whether the remaining percentage would still be enough to spread the disease. CWD prions shed by animals can linger in the soil for years and still possibly spread infection, Allen said.
In addition to Wyoming, 28 U.S. states and four Canadian provinces have widespread CWD infections in wildlife, she said. It’s also spreading in wild animals in South Korea and some Scandinavian countries (Finland, Norway, Sweden).