(MILES CITY) – Even though the possibility of Chronic Wasting Disease remains a major concern in Montana, there is little funding available for testing efforts, so regional Fish, Wildlife & Parks staff are doing what they can at the local level.
The shop at FWP’s Region 7 headquarters was converted into a makeshift laboratory Thursday morning in order to collect samples for CWD testing. FWP Veterinarian Jennifer Ramsey, Disease Ecologist Emily Almberg and Technician Keri Carson were visiting from the FWP Wildlife Laboratory in Bozeman to walk staffers through the process.
What is CWD?
CWD is a progressive, fatal disease affecting the central nervous system of mule deer, white-tailed deer, elk and moose. It is part of a group of diseases called Transmissible Spongiform Encephalopathies. Infectious, abnormal proteins called “prions” accumulate in an animal’s brain, causing a spongy appearance to the tissue that is visible only under a microscope.
Almberg described symptomatic animals as “emaciated [thus the term wasting], often drooling, with their head hung down, ears drooping, having a weird gait, circling or staggering.”
Ramsey said it can take several years for an infected animal to develop symptoms. “A lot of them die of pneumonia because they can’t swallow, they aspirate and get pneumonia.”
Animals are thought to become infected by ingesting prions either directly from another animal or from the environment, Ramsey explained. There is no evidence that the disease is transmissible to humans, but people are advised to avoid eating meat from animals known to be infected. If hunters happen to harvest an animal that looks sick, she urges them to report it and have it looked at if there is a question.
Why the concern?
The only documented cases of CWD in Montana were in captive animals at a game farm in Philipsburg in 1999; however, CWD has been detected in free-ranging populations in 19 other states and two Canadian provinces – some very near the border with Montana. In fact, it has been detected in all of the states or provinces with which Montana shares a border, except for Idaho and British Columbia.
“CWD is uniformly fatal and has been documented as causing declines in survival rates in infected populations of wild deer and elk,” Almberg said. “Wyoming, for example, now has evidence of population-level declines in some of their mule deer herds with high prevalences of CWD. Models have predicted CWD-associated cervid [member of deer family] declines for years, and now we’re actually seeing evidence of that.”
Ramsey said, once CWD makes its way into an area, it poses a huge challenge for officials to try to contain it.
“The prions are very resistant to degredation, so once they’re in the environment, they stay there and remain infectious for many years” she said. “So, you can imagine that as more and more animals in an area become infected, the environment becomes more infected.”
Southeastern Montana’s Region 7 is considered a high-priority surveillance area because of its proximity to known CWD cases in Wyoming and elsewhere, and its relative high densities of deer.
“We’re ramping up sampling,” Almberg said. “We have good reason to believe it’s knocking on our door, if it’s not already here.”
How CWD is monitored
FWP has conducted CWD surveillance across Montana since 1998. By 2011, it had compiled more than 17,000 postmortem samples from free-ranging deer, elk and moose – all of which were negative. There is no non-invasive, reliable test for live animals. Unfortunately, federal funding for testing was cut back in 2012, so the agency now limits sampling to high-risk areas or symptomatic animals.
“There’s no extra funding, so we’re trying to find ways to get the most information on a small budget,” Ramsey said.
One way is for lab employees to train regional staff to collect their own samples, which is what brought the trio to Miles City Thursday.
In the FWP shop, four tables were covered with some of the 21 thawing mule deer heads collected at check stations, along with an array of scalpels, forceps, baggies and jars of formalin. Clad in white lab coats, 11 Region 7 staffers including biologists, wardens, and the regional supervisor listened as the experts outlined what makes the best CWD samples. Mule deer are the preferred test subject, and bucks are twice as likely to test positive for CWD, Almberg said. The first priority is symptomatic animals, followed by road-killed animals, whose symptoms may have contributed to their deaths. After that, they recommend healthy adult bucks and does.
The retropharyngeal lymph nodes, located behind the upper part of the pharynx, are the best tissues to sample because the prions show up earlier here in the course of the disease. Next is the obex, a piece of the brain stem. Ideally, both tissues are collected so the lab has a back-up or secondary sample if there is a positive result. Each item is carefully labeled so it can be traced back to the source animal, and to where that animal was harvested or found.
Ramsey demonstrated how to cut through and separate the foramen magnum, the bony collar at the base of the skull through which the spinal cord passes. Once deep enough, she was able to grasp the brainstem with forceps and cut it away from the connective tissue and the brain. From the brainstem, she trimmed the center or obex portion and placed it in a jar of formalin to preserve it.
She also showed how to locate retropharyngeal lymph nodes by color and texture and proximity to the salivary glands. Ramsey collected the right and left nodes and placed them in a small bag. The third item taken is a front lower tooth to help age the animal being tested.
Similar sampling is being conducted in high-priority surveillance areas in other FWP regions. Once the samples arrive at the lab, Ramsey said they generally can be processed in 10 days to two weeks. If a sample were to test positive, FWP has a CWD action team that is working on a more detailed response plan.
“That response may vary depending on where the disease shows up,” Ramsey said, “but the Department of Livestock and Department of Public Health and Human Services will be involved, and the public will be notified when we get our first confirmed detection. The initial response will likely involve ramping up testing around the location of the confirmed infection to try to get an idea of how prevalent and how widespread the disease is on the landscape.”
Some tools are already in place to try to combat the disease, such as a ban on full carcasses being brought into Montana from areas with CWD, and a ban on feeding deer, which causes them to congregate. The state also does not relocate cervids from one area to another, nor does it rehabilitate and release them back into the wild because of CWD concerns. Game farm animals are now classified as alternative livestock, and FWP is proposing revisions to the United States Department of Agriculture CWD program standards.
“Folks have been working on different ideas for control, but so far there’s no magic bullet,” Ramsey said.