F&S Update: CWD

10 crucial facts every big-game hunter must know about chronic wasting disease.

Field & Stream Online Editors

** 1. What is chronic wasting disease? **
Chronic wasting disease, or CWD, is a member of the transmissible spongiform encephalopathy (TSE) family of brain diseases that affects deer and elk. Even scientists on the front lines of research don't fully understand TSE diseases. The most widely accepted theory is that they are caused by an abnormal type of protein called a prion, which acts upon normal proteins in the brain and causes them to form toxic aggregates that destroy brain cells and tissue. The brain tissue becomes riddled with spongelike holes, hence the term spongiform. These diseases can be transmitted from animal to animal, although in most cases, scientists are not certain how it occurs.

Other TSE diseases include: Scrapie, which kills domestic sheep and has been known for more than 200 years.
Bovine spongiform encephalopathy, or "mad cow disease," which kills domestic cattle.
Creutzfeldt-Jakob disease, or CJD, which affects humans and has been documented since at least the 1920s. CJD is a disease of old or late middle age and has always been a rare ailment-probably killing about one in 1 million people around the world every year. New variant CJD (vCJD), which appeared in Europe in the 1990s, is linked to the mad cow epidemic. Of those affected, many were much younger than traditional victims of CJD.

2. Where is CWD found? Scientists first discovered CWD in captive mule deer at a wildlife research facility near Fort Collins, Colorado, in 1977. Shortly thereafter, it appeared in mule deer at a sister research station near Wheatland, Wyoming. Whether CWD existed in the wild before that is unknown, but it has now been found in a 14,600-square-mile area of Wyoming, Colorado, and a small part of Nebraska. This area is the heart of the disease problem-rates of infection are as high as 15 percent in mule deer, and 1 to 2 percent in the sparse population of elk that roam there. At the southern perimeter of this area, Colorado wildlife officials say that they have found a hotspot where infection rates in mule deer may be as high as 30 percent. No other TSE disease has ever been found at those rates of infection.

In February 2002, random testing of hunter-killed whitetails showed that CWD was present in an area of south-central Wisconsin around the town of Mount Horeb. It is now believed that the infection rate in this area is around 3 percent, according to Tom Hauge of the Wisconsin Department of Natural Resources.

Last year, the disease appeared in apparently isolated cases in southern New Mexico, in South Dakota, and in Illinois just south of the infected area in Wisconsin. Most recently, a case was confirmed in northeastern Utah.

Game farms in Montana, South Dakota, Minnesota, Nebraska, Colorado, Kansas, Oklahoma, and the Canadian provinces of Alberta and Saskatchewan have also been found to carry CWD.

3. How fast is CWD spreading?
In the area of Colorado and Wyoming where the disease has been seen in wild deer and elk for decades, it has spread very slowly, but it has spread. Nobody knows the extent of the spread in Wisconsin. Outbreaks in the wild in Saskatchewan, South Dakota, and Nebraska are believed to be related to infected game farms. So is the appearance of CWD in the wild on Colorado's West Slope.

** 4. Can I get CWD or a related disease from eating the meat of an animal with CWD?**
At this time, scientists believe that chronic wasting disease has not produced CJD or other disease in people who eat deer or elk meat. Researchers have been alert to the possibility that it could, because during and after the outbreak of mad cow disease in Europe, vCJD appeared and was almost certainly caused by eating beef products taken from infected cattle.

Researchers point out that as many as 80 million people consumed products contaminatedy mad cow disease, and so far 131 people have died of vCJD. Skeptics say that the incubation period of all TSE diseases is very long, and we may not have seen the last of vCJD deaths.

Sheep scrapie apparently does not produce disease in humans-people have been eating every part of sheep for centuries, and no case of human scrapie has been documented.

**5. But didn't some people die of a brain disease after eating game meat? **
Yes. In 1999, CJD was diagnosed in three Americans in their late 20s and 30s, all of whom had eaten deer or elk. Extensive investigation of the cases by Dr. Ermias Belay, of the Center for Disease Control in Atlanta, failed to find a concrete connection to meat contaminated with CWD. "We focused on these three cases because the disease is so rare in these age groups, and because they had venison consumption in common," says Belay. "The venison was not from an area where we knew there was CWD, so we collaborated with the USDA to take deer brain samples from the areas where the patients obtained their venison. In over 1,000 samples, we found no CWD. The data we have argues against a link between venison consumption and these CJD cases."

In 2002, after CWD had been discovered in south-central Wisconsin, the Milwaukee Journal Sentinel ran a story about three Wisconsin hunters who died of brain diseases after a lifelong tradition of sharing wild game feasts. Another extensive investigation failed to discover a link to CWD-the men shared many habits other than just wild game feasts-and it was later reported that only one of them actually died of CJD. A report from the Center for Disease Control concludes: "The risk of infection with the CWD agent among hunters is extremely small, if it exists at all."

**6. Is CWD different from mad cow disease? **
Yes. There are technical differences-the pattern of destruction in the brain tissue looks different, for one. But the most interesting differences are also the most disturbing. The mad cow epidemic is believed to have been caused by the feeding of rendered sheep and cattle proteins back to cattle. Somewhere, a cow with a previously unknown TSE, or a sheep with scrapie, went into the mix. CWD has no such origin that anyone can point to at this time.

More disturbing, mad cow disease affected only about 3 percent of cattle at the height of the outbreak. It is not believed that it was contagious between cows, or from cows to people, unless it was eaten. But CWD clearly is contagious among deer-whether from prions in feces, saliva, dander, or something totally overlooked. And it has shown infection rates of 15 percent or higher in deer. (It is interesting to note that elk are infected at a rate of only about 2 to 3 percent at the highest.)

7. How can I tell if a deer or elk has CWD?
Deer and elk in the late stages of CWD look sick-they hang their heads, stagger, salivate, and lose weight and hair. They experience excessive thirst, and may die near water sources.

It is the early stages that worry most hunters. No one knows how long an animal is infected before symptoms show. In captivity, early symptoms are those of a brain disturbance: Animals become confused and afraid, drink a lot of water, have muscular tremors. In the wild, many of these animals would probably be taken by predators, which might limit the spread of the disease.

Hunters have killed healthy-looking animals that turned out to test positive for CWD, but that is not the norm.

Tests for CWD require brain or lymph tissue. They can determine, with a great deal of accuracy, whether or not a harvested animal has CWD. The problem is that these tests are not yet commercially available, and they are not simple. They are used by wildlife agencies with access to good laboratory facilities.

8. What precautions should I take?
Here's what the Chronic Wasting Disease Alliance (www.cwd-info.org) has to say:

  • Do not shoot, handle, or consume any animal that is acting abnormally or appears to be sick. Contact your state wildlife department if you see or harvest an animal that appears unhealthy.
  • Wear latex gloves when field dressing your deer or elk.
  • Bone out the meat from your animal. Don't saw through the brain or spinal cord.
  • Minimize the handling of brain and spinal tissues.
  • After field dressing an animal, wash hands thoroughly and clean knives and saws with a strong chlorine bleach.
  • Avoid consuming the brain, spinal cord, eyes, spleen, tonsils, and lymph nodes of harvested animals. (Normal field dressing coupled with boning out a carcass will remove most, if not all, of these body parts. Cutting away all fatty tissue will remove remaining lymph nodes.)
  • If you keep the entire skull (for a European mount), you should remove all meat while wearing latex or rubber gloves and soak the head in a strong chlorine bleach.
  • If you have your deer or elk commercially processed, request that your animal be processed individually, without meat from other animals being mingled with the meat from your animal.

9. What is being done to prevent or minimize the spread of CWD?
Colorado has an extensive (and controversial) eradication program under way. By issuing extra tags to hunters and conducting sharpshooter operations, wildlife officials hope to reduce the number of deer in the CWD problem area and hold the population at around 20,000 animals. The belief is that fewer deer will produce a lower incidence of the disease and thus a lower chance of spreading it.

The province of Saskatchewan has so far killed more than 3,000 wild deer after finding CWD-infected wild mule deer outside the fences of a heavily infected game farm there.

Wisconsin is engaged in perhaps the most dramatic and controversial effort to control CWD. Wildlife officials there hope to eradicate all whitetails from a designated area around Mount Horeb, killing at least 25,000 animals. So far, they have found it extremely difficult to find and kill that many animals, and the goal will not be reached for some time, if ever.

Most states now prohibit the shipping of game-farm animals. Because there is no way to test a live animal for CWD, game farmers cannot know if their animals are infected unless symptoms of the disease appear. Some states, Wisconsin among them, have banned the feeding of big-game animals, because researchers are almost certain that nose-to-nose contact and the concentrating of deer is a factor in the spread of the disease.

Wildlife agencies in several states have new regulations about transporting harvested game animals. Colorado and Wyoming, for example, prohibit the removal of whole carcasses of deer or elk from the Chronic Wasting Disease Alliance (www.cwd-info.org) has to say:

  • Do not shoot, handle, or consume any animal that is acting abnormally or appears to be sick. Contact your state wildlife department if you see or harvest an animal that appears unhealthy.
  • Wear latex gloves when field dressing your deer or elk.
  • Bone out the meat from your animal. Don't saw through the brain or spinal cord.
  • Minimize the handling of brain and spinal tissues.
  • After field dressing an animal, wash hands thoroughly and clean knives and saws with a strong chlorine bleach.
  • Avoid consuming the brain, spinal cord, eyes, spleen, tonsils, and lymph nodes of harvested animals. (Normal field dressing coupled with boning out a carcass will remove most, if not all, of these body parts. Cutting away all fatty tissue will remove remaining lymph nodes.)
  • If you keep the entire skull (for a European mount), you should remove all meat while wearing latex or rubber gloves and soak the head in a strong chlorine bleach.
  • If you have your deer or elk commercially processed, request that your animal be processed individually, without meat from other animals being mingled with the meat from your animal.

9. What is being done to prevent or minimize the spread of CWD?
Colorado has an extensive (and controversial) eradication program under way. By issuing extra tags to hunters and conducting sharpshooter operations, wildlife officials hope to reduce the number of deer in the CWD problem area and hold the population at around 20,000 animals. The belief is that fewer deer will produce a lower incidence of the disease and thus a lower chance of spreading it.

The province of Saskatchewan has so far killed more than 3,000 wild deer after finding CWD-infected wild mule deer outside the fences of a heavily infected game farm there.

Wisconsin is engaged in perhaps the most dramatic and controversial effort to control CWD. Wildlife officials there hope to eradicate all whitetails from a designated area around Mount Horeb, killing at least 25,000 animals. So far, they have found it extremely difficult to find and kill that many animals, and the goal will not be reached for some time, if ever.

Most states now prohibit the shipping of game-farm animals. Because there is no way to test a live animal for CWD, game farmers cannot know if their animals are infected unless symptoms of the disease appear. Some states, Wisconsin among them, have banned the feeding of big-game animals, because researchers are almost certain that nose-to-nose contact and the concentrating of deer is a factor in the spread of the disease.

Wildlife agencies in several states have new regulations about transporting harvested game animals. Colorado and Wyoming, for example, prohibit the removal of whole carcasses of deer or elk from