Published by Whitetails Unlimited, Inc /02

Transcription

1 By Jeff Davis, Editor Whitetails Unlimited Magazine Sixteen-year-old Thomas Schulenberg missed the buck with his first shot while hunting near Mt. Horeb, Wis. last fall. His second shot was dead-on, not only because of the distance, only 50 yards, but because the buck did not react at all to the first shot. When Schulenberg and his father approached the downed animal it was obvious that there was something very, very wrong. The buck was noticeably ill so sick the pair didn t even field dress the animal. They loaded the buck into their vehicle and delivered it to a Department of Natural Resources field station where the DNR was gathering random samples for disease testing. The Schulenbergs had no idea, but that second bullet had just ignited a hot zone. Tom Hauge, Director of the Bureau of Wildlife Management with the Wisconsin DNR, was in the middle of a meeting in February when he was handed a note. He looked at the piece of paper, got up and quickly left the room. He, and many other DNR employees, suddenly had much more important work to do. Three deer, including Thomas Schulenberg s buck, had tested positive for Chronic Wasting Disease (CWD), an always fatal brain disease that had never been found east of the Mississippi River. In fact, the closest case of CWD previous to this had occurred 900 miles away in western South Dakota, and to date the disease had affected mostly mule deer and elk in several western states. Chronic Wasting Disease is menacing, in great extent because of what is not known about it. The first question on everyone s mind is can it be transmitted to humans? So far, the answer is encouraging. Both the World Health Organization and the federal Centers for Disease Control agree that there is no evidence CWD can infect humans. Having said that, it is now recommended that hunters take precautions when field dressing and processing their deer, and as with any animal, it is recommended no one consume any part of a deer that appears diseased. What isn t clearly known is how CWD spreads, how long it takes to show clinical signs of illness, how long it lasts in the environment, or how many infected deer are in the woods. Also not known is whether white-tailed deer are more or less susceptible than elk or mule deer, and how the disease moved from western states and appeared in a southern Wisconsin deer herd hundreds of miles away from any known infected area. The Wisconsin DNR had instituted a screening program looking for the disease in 1999, but the appearance of three animals with the disease sent the DNR into overdrive. In what was stunning speed for a large, high-profile wildlife Photo by John R. Ford department that answers not only to the governor, but also in a unique way to the state legislature and a citizen Natural Resources Board, the DNR used computer models and statistical techniques to plan and execute a hunt to determine the extent of the problem. And there was more bad news. The hunt harvested 516 adult whitetails from an area of 415 square-miles, centered on the three deer that already tested positive for CWD. Initial tests found 11 more positive cases, and more sensitive tests eventually identified four more deer with CWD, for a total of 18 positive cases. Armed with this data, examining the locations where the positive animals were killed, and factoring in deer dispersion patterns, the DNR made a very difficult decision. As many deer as possible within a 290 square-mile area need to be killed, some 15,000 to 25,000 animals. The announced goal was to remove every deer in the center area, and also reduce the deer population in an area around the hot zone from the current population of 50 deer per square mile to five per square mile. This reduction program is expected to take up to five years. While the announced decision seemed drastic, it was based on a simple public health concept isolate the contagious animals so they cannot continue to infect healthy individuals. Tragically, there is no way to isolate wild deer, and there is no way to identify diseased animals outside of a brain tissue biopsy. Published by Whitetails Unlimited, Inc /02 Photo by Neal & MJ Mishler

2 In addition to the culling program, the Wisconsin DNR instituted numerous emergency rulings to help stop the spread of CWD. One of the more contentious was banning the baiting and feeding of deer. The state legislature has appropriated $4 million in emergency funds, even as they face a $1 billion budget shortfall. In addition, the movement of cervids to and from game farms (suspected of being the way CWD arrived in Wisconsin) is now very tightly controlled. There will be extended hunting seasons with additional tags available, and the DNR plans to test 500 deer in each county in the state to determine the disease s actual prevalence and distribution within the state. The DNR plan is described as dynamic, and is constantly being refined as more information becomes available. The Wisconsin DNR has been in close consultation with agencies in other states, and they are all concerned. The federal government is likely to appropriate funds to help fight this disease. This is just the beginning of a long fight, and so far the reaction and decisions seem to have been based on science and research instead of hysteria and hype. The more individual hunters and sportsmen educate themselves and get involved, the more likely it is this problem can be managed and controlled. Q & A What is Chronic Wasting Disease? Chronic wasting disease is a progressive neurological disease and belongs to a family of diseases called transmissible spongiform encephalopathies. CWD is the variation that occurs in cervids (deer and elk). It is caused by an unusually shaped protein called a prion. Prions are not a living thing like a virus or bacteria, but are able to replicate and destroy the brain of an affected animal, causing a sponge-like appearance in the brain tissue. Once a deer contracts CWD, it will die from it. Researchers do not know exactly how deer contract the disease, or how the disease has moved into Wisconsin. Symptoms include abnormal behavior, loss of weight, excessive drooling, drooping ears, teeth grinding and holding the head in a lowered position. Where is it found? CWD was first identified in Colorado in It has since been found in areas in Wyoming, South Dakota, Nebraska, Kansas, Oklahoma, Montana, Alberta, Saskatchewan, and most recently in Wisconsin and New Mexico. The disease has been found in both wild and captive cervids. How can an infected deer be identified? The disease progresses slowly, and attacks the brain causing neurological damage. Deer under 18 months do not exhibit symptoms, and the only definitive method of diagnosis is a biopsy of the brain (a new test may be able to use tonsil tissue). Clinical symptoms include abnormal behavior, loss of bodily functions, weak and emaciated appearance, loss of appetite, excessive drooling and urination, teeth grinding and drooping head and ears, and death. Some of these symptoms can be caused by other diseases, and cannot be used to positively determine if an animal has CWD. How common is CWD? It is relatively rare, even in areas where it has been identified. In the Mt. Horeb area of Wisconsin it was found in about 3% of the sample. In Colorado, about 1% of elk in the core area are infected, with 5-15% of mule deer in the core area affected. What should I do if I see a sick deer? Note the location as precisely as possible and contact your local DNR, or appropriate agency for your state. Let the experts handle What is Whitetails Unlimited Doing? Whitetails Unlimited is leading the charge against Chronic Wasting Disease. WTU set up a $100,000 cost-share fund and is actively raising additional money to be used for research into the disease. WTU was a sponsor of a national CWD symposium in Denver, where top experts from federal and state agencies as well as universities, and independent researchers exchanged information and devised strategies to combat CWD. WTU has formulated plans to raise additional funds at events this fall, and insure the money gets directly to biologists at the grassroots level. Individual chapters are involved in supporting researchers by building deer traps, providing volunteer labor and providing other assistance under the direction of local wildlife professionals. WTU has developed a program called Operation CWD in cooperation with the Wisconsin DNR. The study of deer movement patterns will provide more accurate data to use in computer modeling. WTU has been active in presenting our concerns in Washington D.C. through members of the Congressional Sportsmen s Foundation and the International Association of Fish and Wildlife Agencies in regards to a unified approach to dealing with CWD. WTU has been active in urging state wildlife agencies in states where CWD has not yet been identified, to take a proactive approach by developing a random surveillance testing program for the upcoming hunting season. WTU is conducting a public outreach program to distribute accurate information about the disease and current methods to control its spread. Published by Whitetails Unlimited, Inc /02

3 it. As with any diseased animal, do not approach it or put yourself at risk. Can infected deer or elk be treated? No. Once an animal contracts CWD it is fatal. It is not known how long it takes the disease to progress, if there is a latency period, or if other factors are involved. How is CWD transmitted? While it is not known definitively circumstantial, observational and experimental evidence suggest direct animal-to-animal contact, mother-to-offspring, contamination of feed or water via saliva, urine or feces, and environmental contamination may all be factors. In addition, deer are known to gnaw bones found in the wild, and this may transfer the disease from a deer that has died of CWD to a new deer. CWD seems to be more prevalent in areas with high animal densities (like the Mt. Horeb, Wis. area), and areas where animals congregate at artificial feeding or water stations. Is it safe to eat venison from infected deer? It s common sense that you should not consume any part of any animal known to be sick from any disease. If you didn t know that a deer had CWD and you ate it, current evidence suggests that you would be safe. There is no evidence so far that CWD can jump species to humans. Prions accumulate in certain parts of infected animals, parts that are not normally consumed. These Testing For CWD The Gold Standard is the most accurate testing method. It is very complicated on a number of levels, and involves a number of highly trained professionals. First, a specific part of the brain stem must be extracted, and specific lymph nodes must be dissected from under the jaw. The sample must be preserved in a chemical, sliced into extremely thin sections using a special machine and then prepared for examination under a microscope. A series of specialized stains that bind to the prions (if there are any) are applied and then rinsed in a series of specific steps. The process of slide preparation, staining and rinsing, can take more than 50 hours total, because an individual sample must soak and rinse for specific periods of time. When the slide is ready, it is usually examined by a veterinary or human pathologist and evaluated for the presence of CWD. The USDA-APHIS is working to bring at least 5 more labs on line to test for CWD by this fall, making a total of 11 labs accredited for CWD testing. Lab selection is being conducted by a multi-agency team from the federal government and state wildlife agencies. The USDA recently announced that they will not license any private labs to do this Gold Standard testing. If anyone tells you they have a quick, reliable and easy test, you should be very suspicious. parts include the brain, eyes, spinal cord, lymph nodes, tonsils and spleen. Follow the new instructions for field dressing and processing. Can CWD infect livestock or other wildlife? CWD has been a problem in several states for up to three decades, and there is no evidence that it has or can be transmitted to livestock or other (non-cervid) animals. Bighorn sheep and pronghorn antelope have not come down with the disease, even though they have been exposed to it under research conditions in western states. Is there a field test that I can use when hunting? Not yet. While there is great interest in such a test it does not yet exist, and there won t be one in the near future. There are clinical trials underway evaluating a test using a tonsil biopsy, but it is not expected to be validated for some time. What should I do? Deer experts stress the importance of reducing the current recordsize deer herds, and recommend hunters try to harvest as many deer as is legally allowed in Wisconsin this fall. As with any game animal, you should not eat or handle any deer you believe to be diseased. If you observe or harvest a deer you are suspicious of, immediately call your local appropriate local state wildlife agency, so they can analyze the animal. Finding out how deer move within their environment is critical to understanding how CWD spreads. Attaching radio collars to deer by live-trapping them is a method used to study deer dispersement. Published by Whitetails Unlimited, Inc /02

4 Can a Processing Plant Become Infected? If a plant handles venison, does that pose a significant risk of build-up of infectious prions within the plant environment, which could affect other meat products? That question is impossible to answer with absolute certainty at this time, but it seems unlikely for the following reasons: Venison from few, if any, CWD affected deer would be processed in any plant. By not cutting into spinal cord or brain, and by removing lymph nodes, the suspected source of infectivity is not released into the plant environment. Prions are not airborne, nor do they grow in number or amount. Thorough cleaning of plant equipment with a detergent to remove protein materials should eliminate most prions which could be present. Meat inspection regulations already require strict separation of inspected traditional meats from uninspected venison, including thorough cleaning and sanitizing of equipment. Effective sanitizing of food contact surfaces with a bleach and water solution has been shown to greatly reduce the infectivity of any prions. If prions were adhering to equipment surfaces so tenaciously as to survive scrubbing with soapy water and a strong sanitizer, it seems unlikely they would transfer to future meat contacting the surface. How Can any Potential Food Safety Risk Be Minimized? As always, do not process or consume venison from a deer which appears unhealthy in any way (emaciation, visible infections, other outward signs or abnormalities). Prevent entry of brain, spinal cord or lymph nodes into venison which will be consumed. Do not cut into the brain or spinal cord. Bone-out the deer without cutting through the backbone. Wear rubber or latex gloves when handling raw venison. This is a good practice for handling venison even without the CWD issue. Thoroughly clean knives and equipment after use with a warm detergent solution to effectively remove protein materials. Rinse or soak equipment in a 50/50 solution of bleach and water after cleaning (strong chlorine solutions have been shown to greatly decrease the infectivity of prions - allow to soak for one hour). How Can I Help Fight CWD? Most importantly, Get Out and Hunt. The deer herd is at an alltime high, and reducing the deer herd will slow the spread of CWD. It is ironic that at the time that hunters are needed the most to reduce the size of the deer herd, some are questioning whether they should hunt. Since the transfer of CWD to humans has never been known to occur, it is not possible to quantify any potential risk. Follow the new guidelines on field dressing and processing deer and elk. Need More Information? The internet hosts numerous websites about CWD. Doing a search for Chronic Wasting Disease will provide you with the latest information about CWD. State and federal agencies are also excellent sources of information about the disease. Whitetails Unlimited website: Wisconsin DNR website: Wisconsin Department of Agriculture website: datcp.state.wi.us Key word: chronic wasting disease. This information provided by: Contact Your Elected Representatives The federal government is expected to soon allocate funds to research and fight Chronic Wasting Disease. State officials have said so far there has been excellent cooperation among many different agencies, at all levels. They fear that when the federal money is available, very little of it will end up with the people on the ground where the actual research and work will be done. We encourage you to contact your elected representatives and let them know that: The fight against Chronic Wasting Disease needs to be funded now, to avoid spread of the disease to other areas. Federal money needs to fund state projects, so the people who are already in place can most efficiently and quickly conduct research and accomplish what needs to be done. Federal agencies that have professional and physical resources not available to states, should be enabled to provide those resources to support the state efforts. The most impact you can make with your elected representatives is by writing, ing or calling them to express your opinion in a brief, but clear, message. You can find the mail or address, or phone number of your senator or representative at the following websites: U.S. House of Representatives: or the official House site: U.S. Senate:

5 The Human Health Question There are questions about the potential human health risks associated with Wisconsin venison. Hunters want to know if there is a health risk from consuming venison, and meat processors want to know if there is any risk to the safety of their plant s environment if they handle venison. Since the transfer of CWD to humans has never been known to occur, it is not possible to quantify any potential risk. However, many things are currently known about the potential CWD risk to humans, and some recommendations are available to minimize that risk. Why the Concern About CWD and Human Health If CWD is a disease of deer and elk, why is there a concern for human safety? A human transmissible spongiform encephalopathy (TSE) exists, and it is termed Creutzfeld-Jakob Disease (CJD). It occurs worldwide, generally in older individuals (usually over 65 years of age), at the rate of about one case annually per 1,000,000 people. It had been previously thought that each distinct naturally occurring TSE only existed within a specific species; that is the disease could not cross the species barrier, and affect other types of animals or humans. However, in the wake of the bovine spongiform encephalopathy (BSE - Mad Cow Disease ) outbreak in British cattle in the 1980 s and 90 s, approximately 125 humans have contracted what is called new variant CJD, differing from the traditional form in that it occurs among younger adults and produces somewhat different pathological changes in nervous tissue than classical CJD. One possible explanation for the appearance of the nvcjd is that it was contracted by consuming beef nervous tissue (brains) containing the infectious prions, which were able to affect people. Although there is currently no evidence that this occurs with CWD, this threat is the basis of the potential food safety risk associated with venison from deer or elk having CWD. What Does This All Mean for Venison Safety? Given the above facts about the disease in deer and the potential (hypothetical) health implications for humans, and knowing that almost nothing in our lives can attain risk-free absolute safety, what available information exists to help hunters and processors make informed choices about venison safety? Consider the following: The World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have found no scientific evidence to date that CWD can be transmitted to humans. No link has been found between CWD in deer and elk and Creutzfeld-Jakob Disease (CJD) in humans. Infectious prions haven t been found in meat (muscle tissue) of BSE-infected cattle or scrapie-infected sheep (scrapie is a TSE of sheep). These agents have only been found in the brain, spinal cord, eyes, lymph nodes, tonsils and spleen. CWD infected deer and elk have existed in Colorado and Wyoming for over 30 years, with no apparent association of CWD with other TSEs of man or other animals. The incidence of the human form of this disease (CJD) has remained level at the expected annual rate of about one case per 1,000,000 people in that area. This includes individuals who have slaughtered deer and elk, and workers in research facilities studying CWD. Surveillance information collected thus far in Wisconsin has found CWD-infected animals only in the area west of Madison (infection rate of about 3% among deer harvested). Deer tested in all other regions of the state have not been found infected with CWD. A much larger surveillance sampling of deer from throughout the state during the 2002 hunting season will provide additional information on the distribution of infected animals. Other Safety-Related Observations Scrapie has been present in sheep for over 200 years, with no evidence of transmission to humans via the meat. Incidence of CJD in humans in Wisconsin occurs annually at about the same rate of one case per million people as is found worldwide. Annual reported cases of CJD among Wisconsin s nearly 5 million inhabitants averaged 4.3 cases per year for the period 1991 to 2000 (high of 7 in 1993; low of 1 in 2000). Evaluating the Risk Everyone evaluates risks in life from their own unique perspective. For example, some people always wear seat belts in a car to reduce the risk of being injured or killed in an accident. Other people never wear seat belts because they feel the risk is not great enough to merit the discomfort of wearing them. Risk specialists have found that certain outrage factors associated with a situation will intensify people s concern about the magnitude of a risk. These factors include diseases that are regarded as exotic, poorly understood as to their cause and transmission, and have a dreaded health consequence, as well as situations where an individual has little personal control. The CWD issue has all those factors associated with it, increasing our awareness of any potential problem. Being struck by lightning, involved in an auto or plane crash, contracting foodborne illness or having a heart attack are all very real risks which create harmful outcomes, but these may have less perceived risk (seem less threatening) than CWD because they are more common and better understood. Information supplied by the Dennis Buege, Animal Science Department, University of Wisconsin-Madison

6 Common-Sense Precautions for Handling and Processing Deer Chronic Wasting Disease is a fatal neurodegenerative illness of deer and elk. It is characterized by accumulations of abnormal prions forms of protein that differ in shape from normal proteins that occur naturally in the brains of deer and elk. The abnormal prions are very difficult to destroy; they can survive many traditional sterilization techniques, including gamma and ultraviolet radiation. While they don t have DNA nor RNA, they are able to transform normal proteins to their own image, creating spongelike holes in the brain. Because of their long incubation periods, prion diseases have been mistaken for slow viruses. According to the World Health Organization, there is no evidence that the disease passes to humans. To reduce the risk of exposure the Wisconsin Department of Agriculture, Trade and Consumer Protection recommends the following guidelines for removing prions from venison. FIELD DRESSING Wear rubber or latex gloves. Do not use household knives or utensils. Remove all internal organs and minimize contact with them. Clean knives, counters, and equipment of residue, and disinfect with a 50/50 solution of household chlorine bleach and water, and dry. Soak knives in disinfectant one hour. CUTTING AND PROCESSING (Follow field dressing guidelines as well) Do not cut into or through bones. Do not cut through the spinal column, except to remove the head. Use a knife designated only for that purpose. Bone out the meat and remove all fat and connective tissue (the weblike membranes attached to the meat). If processing deer from the CWD management or eradication zones, keep meat and trimmings from each deer separate. CONSUMPTION Never eat a deer s brain, eyeballs, tonsils, spinal cord, spleen or lymph nodes.