What Missouri Hunters Need To Know About CWD
September 30, 2010
Missouri has dodged the chronic wasting disease bullet so far. To keep it that way, every hunter should take responsibility for helping to prevent this scourge from afflicting our deer. (January 2007)
Photo by Curt Helmick
Missouri is bounded on the east and west by states that have reported outbreaks of chronic wasting disease, an incurable, 100-percent-fatal infection that strikes members of the deer family. However, while it has infected wild deer in Illinois, Kansas and Nebraska, and captive elk in Oklahoma, Missouri Department of Conservation officials have yet to find CWD in the Show-Me State.
"We took more than 22,000 samples (of brain tissue and lymph nodes from deer) over three years, including up to 200 samples from every county in the state, and everything we've submitted has come back negative," said Jeff Beringer, an MDC resource scientist, during an interview last summer.
That's good news for everyone in Missouri, but that doesn't mean we can all relax. Beringer and his colleagues intend to continue watching for signs of the disease, and you can help, too.
To arm you with facts about this complex topic, we've rounded up the latest research to explain CWD, how it could affect you and the deer you hunt, and what you can do to fight this devastating wildlife illness.
CWD, like mad cow disease and scrapie in sheep, is classified as a transmissible spongiform encephalopathy that damages the brains of white-tailed, blacktailed and mule deer, Rocky Mountain elk and moose. It gained its descriptive name in the 1960s after captive mule deer in Colorado became disoriented and gradually lost weight until their emaciated bodies collapsed, but scientists believe it's been around for much longer.
Since then, CWD has stricken free-ranging and captive herds in 13 other states: Illinois, Kansas, Minnesota, Montana, Nebraska, New Mexico, New York, Oklahoma, South Dakota, Utah, West Virginia, Wisconsin and Wyoming. Additional outbreaks hit Alberta and Saskatchewan in Canada and a South Korean elk ranch.
While the disease's geographic breadth is breathtaking, the number of affected animals can be low in some places. For example, fewer than 5 percent of wild deer and only 1 percent of wild elk have CWD in endemic areas of Colorado and Wyoming. In contrast, the infection rate in and around one Nebraska deer enclosure reached 37 percent. Only one CWD-positive moose, taken by a bowhunter in Colorado in 2005, had been reported at press time. Infection rates for captive cervids are typically 50 percent or greater.
Because no treatment exists, captive herds with CWD are typically destroyed. When it attacks wild cervids, authorities establish disease reduction or eradication zones and authorize special hunts to thin the population and thus reduce the potential for disease transmission. Such hunts have occurred in Colorado, Nebraska, Wisconsin and Saskatchewan in recent years, where experts say it could take years for local populations to recover to pre-outbreak levels.
As awareness of CWD has increased, wildlife agenciesacross the country have enacted plans to monitor wild and captive cervids. The MDC's comprehensive sampling program through the 2004-05 deer season was, Beringer said, "a pretty concerted effort. We considered our plan done by then. If we don't find CWD with this (intensive sampling program), we don't believe it could exist at a prevalence greater than 1 percent."
There are no plans to continue mandatory testing of hunter-harvested deer for now, but that doesn't mean the search has stopped.
"Now we'll get the biggest bang for our buck by sampling sick deer," Beringer said. "We want to hear from anyone who's seeing abnormally behaving deer, especially if the deer are thin. CWD-infected deer are emaciated and are sick for a long time."
Such animals often have dull, blank expressions, listless movements and allow people to approach more closely than would a healthy deer.
Beringer noted that Missouri's deer sometimes suffer from epizoÖtic hemorrhagic disease, a disease passed on by small biting insects. "It's worse in dry years," he stated, "because they breed in mudflats. Typically, EHD deer die looking healthy, and they'll be near a creek when they die, because they're dehydrated. It's worst from August through November, but it's very different from CWD. You may see some hemorrhaging, and internally, blood vessels will be leaking in the body."
Whether you're hunting or out watching wildlife, report any sick deer you see. "Contact your local Conservation representative, and we'll investigate it," Beringer said.
The MDC has followed up about 100 reports of sick deer to date. If CWD became prevalent in areas near Missouri's border, the MDC would resume sampling, Beringer said.
HOW DOES IT SPREAD?
Scientists aren't sure how CWD spreads, but they're positive that infection rates rise when animals are close to another. In experiments, healthy deer that were moved into areas previously occupied by infected deer became ill. These results suggest that animal-to-animal transmission likely involves contact with feces, urine or saliva. Those results also mean that folks who like to feed deer may increase the chances of spreading CWD in local populations.
"Feeding stations are good places for disease to spread," said Beringer.
Food plots that hunters and farmers plant don't concentrate deer as closely and pose less risk. "Food plots don't have deer eating in a 2 square-foot area, where a deer may pick up some corn, chew on it and half of it falls out of its mouth and saliva gets on it, and then another deer comes along and eats it," Beringer explained. "Although transmission is related to interaction, food plots won't cause CWD."
The MDC has no formal regulations directly related to CWD, according to Beringer. But the agency does encourage hunters who harvest cervids from other states to properly dispose of waste in licensed landfills or incinerators.
The MDC does impose some regulatory responsibilities on shooting preserves, which must supply tissue samples from captive deer harvested within their grounds, Beringer said. In October, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service established a federal program to help cervid ranchers certify their healthy herds as CWD-free and to regulate the interstate movement of farmed cervids with a goal of eliminating CWD from captive deer, elk and moose herds.
IS THE MEAT SAFE?
In recent years, hunters have had plenty of reasons to wonder whether it's still safe to eat venison. Most experts would respond with a qualified "yes," because there's no proof -- so far -- that humans are vulnerable to CWD. However, because research continues, you should take a few precautions to minimize any possible risk of picking up an animal-borne disease.
For several years, the World Health Organization has advised hunters to avoid touching and eating brains, spinal cords, eyes, lymph nodes and nerve tissue of cervids, regardless of where animals were harvested. That's because prions -- the rogue protein molecules that damage the brains of CWD-infected animals -- are found in those tissues. Because such parts are offal to most, it's easy advice to follow.
However, when a University of Kentucky professor reported last year that he'd found prions in edible muscle, things changed. A collective shiver rippled through the nation, along with plenty of rumors and misinformation.
While the Kentucky study's results are unsettling, we need to remember that it used the most sensitive CWD testing technology available. Other studies suggest that a species barrier exists, meaning that humans just aren't the right sort of animal to become infected.
However, as a precaution against many diseases, the MDC recommends the use of gloves when you field-dress any game. "You need to avoid eating meat from any animal that's sick," Beringer warned. "That's just common sense. We suggest you wear field gloves to avoid situations where maybe a buck was gored by another buck and there's a systemic infection or you could pick up a tick-borne disease."
While CWD is a genuine threat to the nation's wild and captive cervids, there's plenty of good news for Missouri outdoorsmen. So far the illness hasn't been found in the state, and a program is in place to monitor high-risk animals. You can participate by watching for thin, sickly deer and protecting yourself from animal-borne illness by simply wearing gloves as you field-dress game.
As long as we all do our part, we may not be able to stop CWD, but we can track and contain it.