Resources : Meetings and Symposia

It's been with us since 1967 at the latest. In all likelihood it arrived earlier. But Chronic Wasting Disease wasn't identified as such until the 1970s, and little testing ensued until its apparent spread caused alarm two decades later. Now confirmed on both sides of the Mississippi and as far south as New Mexico, CWD threatens deer and elk across several states and into central Canada. It's been found in wild populations of deer and elk far removed from infected game farms and the "endemic" area of northeastern Colorado.

On August 6 and 7, 2002, 453 wildlife biologists, pathologists and veterinarians, with university scientists, natural resource administrators and the press, met in Denver to discuss CWD. This is a summary of that symposium, written in lay terms but hewing to the meetings format. It is not an exhaustive overview of CWD, partly because this disease seems to make news every week. Since August it has cropped up for the first time in Minnesota, and in Colorado south of Denver. State wildlife agencies have ratcheted up their commitments to testing. The popular press has spewed warnings, data and advice to outdoorsmen. Hunters are being polled to establish the probable effect of CWD on hunting license sales. There's no cure yet, no easy way to test live animals. We don't even know for sure the main means of transmission. The August symposium established what we have found out about this disease. It also confirmed that CWD will remain a wildlife research priority, promising headlines - and headaches - for many months to come.

The symposium at a glance

The August, 2002 CWD symposium in Denver delivered an overview of the known history of CWD, a degenerative and ultimately fatal TSE, or transmissible spongiform encepalopathy. To date, CWD in its natural form affects only cervids. It has been found in whitetail and mule deer and Yellowstone (Rocky Mountain) elk, in North America. Speakers agreed that the earliest recorded cases of the disease, in Colorado and Wyoming, were not recognized as such until years later. They acknowledged that the incidence of CWD is still not great in wild populations, making studies difficult and expensive. Only about 1 percent of the elk and, on average, fewer than 7 percent of the deer tested in the endemic region have been found with the infection. Incubation can take months, however, and in the absence of clinical signs, testing is a random effort. It is also costly. Until recently, the only sure test was immunohistochemistry, or IHC, performed on sectioned brain tissue. Signature brain vacuoles are not otherwise detectable. Outward signs - emaciation, lethargy, frequent drinking and urination, excessive salivation and other uncharacteristic behaviors - do not occur until the latter stages. A live test on deer, using IHC with tonsil biopsy, has proven accurate. Of course, because the deer must be captured, sedated and handled by people expert at performing this difficult procedure, it is an expensive test. Elk tonsils apparently do not show signs of CWD until later, so this new option is of no value in early diagnosis of CWD in elk.

Biologists and veterinarians pointed out that the "spread" of CWD from deer on the east slope of the Rockies to wild animals in Wisconsin and western Colorado, and the increasing incidence of CWD in captive elk herds may result directly from heightened awareness of the disease and more vigorous testing. It would be presumptuous and probably inaccurate, they said, to identify CWD as more active and threatening now than before state wildlife agencies established surveillance programs. Still, it is occurring in places not previously know to be infected. Efforts to arrest the spread of CWD have been limited because the natural mode of transmission is unclear. Speakers concurred that the probable route was through physical contact, possibly through ingesting grass tainted by infected animals.

The causative agent is known. Prions, a type of protein found in normal brain cells, can be changed to a mutant form that appears only in CWD-positive animals. Unlike bacteria and viruses, infectious prions do not themselves replicate to "flood" the animal's organs. Instead they cause normal prions to change. The process is not fully understood. Nor is it evident tht CWD will jump species boundaries as did BSE, the bovine type of transmissible spongiform encepalopathy known as mad cow disease. During the 1990s several hundred thousand cattle in Great Britain were diagnosed with BSE, and more than 100 people who ate meat (perhaps sweetbreads) from infected animals died. The lethal malady: variant CJD, a form of a naturally occurring but very rare human TSE. Creutzfeld-Jacob disease strikes randomly about once for every million people in a population, while variant CJD springs from BSE. Both are fatal. Though laboratory injection of brain homogenates from CWD-positive animals can induce the disease in other species, contact transmission has proven difficult. Scientists differ in their assessment of CWD's ability to jump species boundaries. No substantiated cases of CWD in humans have been reported; however lethal human brain disorders in three Wisconsin men who shared venison have kept speculation alive. The recent finding of infectious prions in the leg muscle of a laboratory mouse calls into question the long-held assumption that CWD confines itself to soft tissues: brain, tonsils, eyes, spleen, pancreas.

Because of human health concerns, federal money has been allocated to states for accelerated CWD research and testing. Twenty-one states now have testing programs in place. Many have restricted importation and transport of captive deer and elk. Disease-free certification programs, like those used to maintain livestock health, are apparently in the offing for privately owned herds. Facilities where captive herds have tested positive have been depopulated and sanitized. Apparently, however, the infectious agents can remain for some years in the environment, as the disease has been found in animals kept on sanitized grounds. Captive herds of deer and elk have come under increased scrutiny as CWD evidently made its way from the U.S. to Canada and then to Korea in captive elk. Confined animals in close contact with each other are assumed more susceptible to any transmissible disease; several speakers from both Canada and the U.S. stressed the need for increased surveillance around game farms and on wild animals with access to penned cervids.

Colorado and now Wisconsin have embarked on aggressive culling programs aimed at substantially reducing deer densities where CWD has been found. Other states have accelerated random testing of hunter-killed animals. Veterinarians reported that new facilities for IHC tests are planned and would be needed to meet anticipated demands even for hunters voluntarily submitting specimens.

It was clear that the states will bear the responsibility for implementing CWD surveillance programs, and for disposing of infected carcasses. Among several disposal options that have been considered, controlled burial at landfills seems least objectionable. Most incineration and hydrolysis facilities have limited carcass capacity, and impose higher costs than mass burial. Air and water contamination remain concerns.

Speakers acknowledged that public perception of CWD and control efforts could profoundly affect hunting, game management and funding for other conservation programs. Several scientists pointed out the need for accurate, up-to-date CWD information in lay form. The CWD Alliance, supported mainly by the Boone and Crockett Club, Mule Deer Foundation and Rocky Mountain Elk Foundation, has established a website to that end. Hunters remain not only an integral part of big game management but an important tool in combating CWD. State wildlife managers reported on policy drafts that affirmed the continuation of sport hunting in infected areas but cautioned that disease control now matters more than hunting opportunity. They warned that unless wildlife agencies - state and federal - attacked CWD with vigor, control programs could fall under the jurisdiction of animal health people. Witness the brucellosis threat in Yellowstone Park bison. While speaker views concerning the role of science in CWD programs differed, and wildlife agencies have adopted a number of tactical responses, all scientists and wildlife managers present seemed committed to a united control effort. They expressed a resolve and optimism in future efforts to determine CWD's causal pathway, accelerate testing, inform the public and, ultimately, arrest and eradicate CWD.

Session I - Opening Remarks/Welcome

"The spread of Chronic Wasting Disease is of national concern," said U.S. Fish and Wildlife Service Director Steve Williams. But he emphasized that states would take the lead in both research and control efforts. Secretary of the Interior Gale Norton has "committed to working closely with the Department of Agriculture and the States to control and eradicate the disease in free-ranging deer and elk." Williams is co-chairing a CWD task force with Bobby Acord of the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS). The task force, comprising also top animal scientists from universities and government agencies, has developed recommendations to arrest the spread of CWD. It is now working to implement them. "The Department of Defense has $42.5 million available for research into this type of disease; $15 million more is on the table as supplemental appropriations for use by states."

Glenn Telling, from the University of Kentucky's Department of Microbiology, reviewed the nature of CWD. "It belongs to a group of fatal neurodegenerative disorders, transmissible spongiform encepalopathies or TSEs," he said. "They're characterized in late stages by the spongy appearance of the brains of infected animals. The causative agent is a mutant protein called a prion. These proteins don't replicate themselves in the manner of bacteria or viruses; rather, they force the normal prions in the host animal to change. This can take two to eight years." He conceded that "the origin and mode of transmission of CWD remain unclear," and that we don't know if it will cross species boundaries. He noted that Creutzfeld-Jakob Disease, a human form of TSE, occurs randomly in one of every million or so people. It is usually fatal within six weeks. Variant CJD, cautioned Telling, can apparently result from exposure to BSE (Bovine Spongiform Encepalopathy or mad cow disease), which infected more than 100 people in Britain during the late 1990s. "Nearly 178,000 British cattle were diagnosed with BSE through the year 2000," he said, adding that confirmed cases, once occurring at the rate of 1000 a week, have since diminished in number to about 30 a week. Telling reported that other TSEs seem less apt than BSE to jump species boundaries.

Is CWD really spreading, or has it been with us for a long time, more visible now because of aggressive testing? Elizabeth Williams of the University of Wyoming said the disease may not be any more prevalent than before. "But it does seem to be spreading." She pointed out three reasons for increasing reports of CWD:

1) ecosystem (environmental) change
2) movement of pathogens (prions)
3) changes in our ability to recognize CWD

"We don't know the origins of CWD," she said. "It was first recognized as a symptom in a herd of confined deer at a Colorado research center in 1967. About 10 years later, that case was identified as a transmissible spongiform encepalopathy. It first appeared in elk in 1981." She ticked off the clinical signs: odd behavior, weight loss, increased drinking, salivation and urination, pneumonia (perhaps due to aspiration of rumen contents).

"Anecdotal evidence suggests that CWD can be transmitted by animal waste on infected ground," Williams explained. "Anything from feces to placentas to carcasses." She pointed out that the disease pathway seems to differ in deer and elk but that in both these cervids infection targets the brain, spinal cord, spleen, tonsils, eyes and lymph nodes. "Immunohisto-chemistry is the best diagnostic tool," she said of the laboratory procedure normally used to detect CWD evidence in sectioned brains. "A tonsil test for live deer shows promise. But while we look for better detection methods and ways to rein in this disease, it's good to remember that CWD is still relatively rare and that other animal maladies such as rabies, sylvatic plague, TB, Bangs and hemorrhagic disease deserve our attention too."

Session II - Chronic Wasting Disease in Free-Ranging Deer and Elk

Mike Miller of Colorado's Division of Wildlife reported that so far CWD surveillance has evolved to satisfy scientific interests in the disease and to gain information for the public on the status of CWD. "Regulatory and economic pressure have been absent." But he implied that may not remain the case. "Targeted surveillance - shooting suspect animals - is obviously biased but useful in tracking the distribution of CWD cases. In Colorado, we've been doing that since the 1970s. Random testing of all dead deer and elk available is much more aggressive and costly, but some states are adopting it to check farmed elk for CWD. Since 1991 testing hunter-killed game - we call it geographic targeting - has helped Colorado determine prevalence as well as the distribution of cases." Miller reiterated that detection is mainly through IHC applied to the animal's brainstem (the medulla oblongata at the obex). He noted that 19 game management units in northeastern Colorado seem to be the epicenter of CWD but that the disease has also been found in Routt County in the state's northwest sector. "We've examined more than 11,500 deer and elk so far. Prevalence in tested deer ranges to 11 percent but averages about 5 percent. It appears to be increasing. Fewer than 1 percent of tested elk showed signs of CWD." Miller said that the Division regularly updates CWD information on a public website:

www.wildlife.state.co.us/cwd/chronicupdate.asp

Wyoming's response to CWD has been less aggressive than Colorado's, reported Terry Kreeger of the Wyoming Game and Fish Department. "We've tested hunter-killed game since 1997, retrieving deer and elk heads from butchers and taxidermists in the endemic area of southeast Wyoming. There," he said, "about 12 percent of mule deer, 16 percent of whitetails and 3 percent of elk have tested positive."

"Nebraska's CWD program began in 1997 when we asked hunters to submit deer for testing," said Bruce Morrison of the Game and Parks Commission. "Recently our state Department of Agriculture made testing mandatory." He noted that 2900 wild deer and 150 wild elk have been tested, with 12 deer testing positive. There's now a restriction against the importation of any cervid from a county where CWD has been found in wild animals, or from any place that has not had a monitoring program for at least five years. "Three Nebraska elk farms have turned up CWD-positive," added Morrison. "One, in Sioux County, produced 11 positive tests by the time it was depopulated early in 2002. Also, 98 of 191 whitetail deer that happened to get in the pen came down with CWD. We'll test about 3500 hunter-killed deer this year, concentrating in the state's panhandle but including at least 100 animals from each of our other deer units."

Julia Langenberg from Wisconsin's Department of Natural Resources reported that its CWD surveillance program started in 1999, on deer "over 18 months of age showing signs compatible with CWD." Currently, testing also includes hunter- and sharpshooter-killed deer from high-density populations. Other targeted areas: any of Wisconsin's 975 game farms that received animals from infected Colorado and Nebraska game farms and wherever the DNR plans to introduce wild elk. From 1999 to 2001 about 1000 deer were tested via IHC at the National Veterinary Services Laboratory at Ames, Iowa. But the first positive test results came from three whitetail bucks shot near each other during the 2001 hunting season. These were the first wild deer found with CWD east of the Mississippi. "Subsequently, 15 more deer tested positive (of 505 shot within the area); but only seven showed outward symptoms of CWD." The DNR then established a 361-square-mile eradication zone, declaring an open deer season one week a month for landowners and contract shooters. The aim: kill 25,000 deer in the next three years. Langenberg added that "the DNR's long-range goal includes testing 500 deer from each of Wisconsin's counties to determine the extent of the disease."

In nearby South Dakota, tests from 1997 through 1999 yielded no signs of CWD in 519 whitetails, 128 mule deer and 368 elk. According to Ron Fowler from South Dakota's Department of Game, Fish and Parks, these animals were shot by hunters, the heads collected from meat processors. No tests were done in 2000. "The next year," he said, "in a sampling of 241 whitetails, 95 mule deer and 166 elk, a single whitetail in extreme southwestern South Dakota tested positive. We'll continue testing of hunter-killed game and any animals showing symptoms of CWD."

Infected game farm elk have apparently speeded the movement of CWD north. Saskatchewan reported its first case - a captive elk - in 1996. "Testing of 283 wild deer and 46 captive animals over the next three years turned up no new cases," said Ron Lind, of the Fish and Wildlife Branch of Saskatchewan Environment. "In 2000, Environment identified to its satisfaction the source of CWD entry into the province. We accelerated surveillance, testing 1500 animals in the west-central target area and 3300 animals province-wide. We found only three wild deer with CWD." If further testing reveals more cases, the most likely response will be herd reductions. In 2001, hunters in a herd reduction area comprising 10 wildlife management zones were issued special tags and required to submit deer heads for testing. None tested positive.

John Fischer of the Southeastern Cooperative Wildlife Disease Study summarized testing in states with little or no proven incidence of CWD. "From 1997 through 2001, more than 6800 deer and elk were tested in Kansas, Oklahoma, Nebraska, South Dakota and Montana, plus 3000 in Wyoming and 10,500 in Colorado," he said. "In all, nearly 29,000 animals from 29 states have been sampled; 21 states have reported no testing." He noted that even in endemic areas, CWD-infected animals have shown up very rarely.

"The low numbers of CWD-positive animals in some wild herds of deer and elk makes tracking the disease difficult," said Colorado's Mike Miller. "But in captive animals and in a few wild populations we've seen it spread fast. That suggests efficient transmission, direct (by contact) or indirect (animals eating where infected herdmates have grazed). Deer and elk migrations speed up both kinds of delivery. If a female has CWD, her offspring will be exposed right away; however this maternal transmission alone won't sustain an epidemic."

Predicting how CWD will affect deer and elk herds locally or nationwide depends on knowing how it spreads. "Based on anecdotal evidence, we've fashioned a computer model," reported John Cary, from the University of Wisconsin's Department of Wildlife Ecology. "We included all the variables we could think of for a herd of up to 300,000 animals. Using this model, we can predict the course of CWD in herds with densities of 1 to 100 deer per square mile." Unchecked, he said, CWD could cause a deer population to collapse in 20 years.

Session III - Chronic Wasting Disease and Scrapie in Farmed Hoofstock

Since 1997, when CWD was found in game farm elk in South Dakota, 23 additional game farms in six states have been found to have infected animals. Lynn Creekmore of USDA-APHIS said 20 of these herds have been depopulated - half since mid-2000. "Only one of the remaining three herds has been declared CWD-free after four years of quarantine," reported Creekmore, adding that of 3600 farmed elk killed since 1997, 195 have tested positive. Of these, 119 or 61 percent came from two herds. USDA funds have been allocated to compensate owners of condemned herds. The agency plans a herd certification program similar to that already used by 20 states. It would apply to red deer as well as to elk, mule deer and whitetails.

Reporting on CWD in Canada, Lynn Bates of the Canadian Food Inspection Agency said the disease may have entered the country in 1974, through an infected mule deer imported to a zoo. The appearance of CWD in game farm elk came two decades later. "Since February, 2000," she said, "this disease has been found in 40 Saskatchewan captive herds and one in Alberta. Thirty-eight of those herds have been traced to one source in Saskatchewan. We think the first infected elk arrived in 1989, an import from South Dakota." Result: more than 8400 elk have been destroyed in a surveillance program that has now tested 10,278 farmed cervids and 7411 in the wild. Of these, 228 captive and three wild animals have tested positive. "Canada made CWD a reportable disease in 2000," said Bates, "following up with surveillance and eradication strategies and a certification plan for trade in cervids."

Session IV - Diagnosing CWD

Certification presumes a practical test for CWD on live animals. "Right now, immunohistochemistry is our best diagnostic tool," said Katherine O'Rourke of the USDA's Agricultural Research Service in Pullman, Washington. "However, it is time-consuming, expensive and requires the skills of a pathologist." Lisa Wolfe, a DVM with Colorado's Division of Wildlife, agrees. "Several other tests, on blood, urine and lymph tissue, have been tried. The only one that works on live animals is a tonsil biopsy. It's not currently useful on elk because lymphoid accumulation of prions occurs much later during the course of the disease in elk than in deer." Wolfe stressed that while the tonsil test has given accurate results, it requires anesthesia, specialized equipment and a veterinarian's skills. "It is more expensive and no faster than IHC analysis of brain stems. Besides, only about 92 percent of tonsil samples are usable, because the operation is done by feel. You can't know if you got the target tissue until afterward." Wolfe concurred with O'Rourke that hunter demands for testing could easily flood the system.

Mo Salmar emphasized that for any CWD test, capacity, as well as accuracy, matters. "We need a rapid screening procedure to compliment existing tests." Two commercial firms, BioRad and Prionics, have begun work on screening and confirmation tests, using brain samples and lymph nodes from Colorado deer and elk.

One premise basic to all diagnostic work is that it apply to a specific disease. Terry Spraker reported that his analysis of brain, eye and lymph tissues suggests that CWD and spongiform encepalopathy in captive and free-ranging deer respectively, are clinically identical. Spraker has investigated the progress of CWD in deer and has identified four categories or stages of infection, ranging from clinical signs in the tonsil only to extensive spongiform evidence in the brain and spinal cord.

"The biggest public concern with CWD has to do with possible transmission to humans," said Richard Race of the U.S. Department of Health and Human Services. "To assess that threat, we must know more specifically the differences among various TSEs, and how each is most commonly transmitted." He reported that tests with domestic sheep in Europe have been inconclusive in differentiating BSE from scrapie, the most common TSE in sheep (and one that may have entered the U.S. with the Conquistadors!). Likewise, distinctions among TSEs in sheep, deer and elk have not been adequately described. "Laboratory rodents may be of some help as we try to sort out differences in clinical signs and means of transmission," concluded Race.

Glenn Telling reported on experiments with transgenic mice. "We're working on a way to detect infectious CWD prions and to identify species barriers," he said. "Mice are already being used in research aimed at determining the prevalence of CWD in wild and captive deer and elk. They'll certainly play a part in our work on species barriers."

Another small mammal being considered for CWD studies is the ferret. Mike Miller and Terry Spraker explained that captive ferrets inoculated (orally or through brain injection) with the saliva, brain homogenates or white blood cells of infected deer soon showed signs of the disease. IHC tests confirmed brain vacuoles. "We may well be able to study infectivity of CWD using this small animal," said Miller.

Session V - Assessing the Potential for Interspecies Transmission

Gregory Raymond from the U.S. Department of Health and Human Services (USDHHS) reported on successful test-tube conversion of protease-sensitive prions to protease-resistant prions. "In other words, we can change normal host prions into the CWD-specific prions in a laboratory." He added, however, that the conversion is "significantly less efficient" across species boundaries. Using protein from CWD-positive cervids, it's difficult to produce the conversion in humans, cattle, sheep or rodents. "There seems to be a transmission barrier at the molecular level," he said.

Inoculations of CWD-positive material from mule deer into the brains of living cattle began at the National Animal Disease Center in 1997, according to Amir Hamir. "We started tests on sheep and raccoons two years later. These experiments are ongoing, but interim results show little evidence of transmission." Three of 13 cattle showed TSE symptoms. Two others were later killed and turned up CWD-negative. The remaining eight are still apparently healthy. One of eight sheep was tested by IHC and declared "clean." All remaining sheep and all the raccoons appear healthy three years into the study. Elizabeth Williams noted that exposing cattle to CWD-infected animals without inoculation has been notably unsuccessful in producing the disease. "Cattle seem more resistant to CWD than to scrapie," she observed.

Acknowledging species boundaries, Richard Race from USDHHS pointed out that scrapie agent can evolve or adapt to a new host. "Over several generations, mice infected with hamster scrapie showed scrapie symptoms." Repeated passage of CWD prions through a new host species might eventually cause a TSE in that species. Patrick Bosque from the University of Colorado Health Sciences Center added that prion amino acid sequences play a big part in confining CWD to cervids. "Our experiments show mice to be CWD-resistant, even when inoculated with brain homogenates from infected animals," he said, but warned that findings with mice may not apply to other species.

To collect, characterize and store the results of TSE research, Case Western Reserve University established the National Prion Disease Pathology Surveillance Center in 1997. "Mainly, this was in response to public concerns over variant CJD," said the University's Shu Ghen. "As of March 31, 2002, we'd examined 787 cases, of which 576 showed prion infection." Of these 423 were "sporadic." No case of variant CJD was documented. Ermais Belay of the Center for Disease Control pointed out that while the apparent spread of CWD has heightened concern about variant CJD, "there's no strong evidence for a causal link between CWD and recent CJD in young patients."

Surveillance for TSE in humans began in Colorado five years ago. "At that time the state Board of Health made TSE a reportable disease in people under age 55," said John Pape with Colorado's Department of Public Health and Environment. "From 1998 through 2001, we found 18 cases of human TSE, plus three in visitors from other states (NE, KS, NC). Ages ranged from 40 to 79. Ten victims were women. No connection with CWD could be established."
Should hunters be concerned about CWD? Gary Wolfe of the CWD Alliance pointed out that even in the "endemic areas" of Wyoming and Colorado, where the disease has been known for 30 years, fewer than 6 percent of the deer and 1 percent of the resident elk have tested positive for CWD. He reiterated that there's "no scientific evidence that CWD can be spread to humans either by contact with infected animals or by eating their meat." But he noted the Center for Disease Control's ambiguous caveat "However, there is not yet strong evidence that such transmissions could not occur." Wolfe advised hunters to:

1. Avoid shooting, handling or eating any animal with CWD symptoms or that has tested positive.
2. Wear latex gloves when field dressing deer and elk.
3. Bone out meat; avoid touching meat with a knife used on the brain, spleen, eyes, lymph nodes, tonsils, pancreas or spinal cord.
4. Wash hand and knife thoroughly after field dressing.
5. Insist that meat processor not mix your venison with that of other hunters.

The Western Colorado Sportsman's Council, represented by Dick Steele,
presented a number of reasons why sportsmen should not be required to eat meat from deer and elk shot in CWD-endemic areas. In summary:

1. While chances of human infection appear remote, the consequences would almost certainly be severe.
2. Carelessness in field dressing can taint meat and is impossible to prevent.
3. One CWD-positive carcass could contaminate a locker-plant full of meat. "A pound of sheep brain infected with scrapie contains 454 million infective doses," said Steele.
4. Laboratory tests have shown that conversion of human prions by CWD and BSE occur at about the same level of efficiency (7 and 10 percent).
5. Human exposure to CWD has been so limited that if the disease could jump species boundaries, it's unlikely we'd have seen a human case yet.

Steele pointed out that fewer than 3300 deer and elk have been shot by hunters in the endemic area of Colorado during the last 30 years. "In Britain, 120 people died of BSE but 60 million were exposed. That's one case per 500,000 people. If each of Colorado's 3300 hunters shooting a CWD-positive deer shared his meat with 10 people, we'd have 33,000 exposures - or 467,000 fewer than might be expected to produce one case of human TSE, if the rate of transmission equaled that of mad cow disease. So it's no surprise we have no evidence of cross-species infection. Our sample size is too small to tell, one way or the other."

Steele added that CWD has been successfully transmitted to a primate (squirrel monkey) by injection, and that scrapie prions have been found in muscle tissue - not just soft organs - of laboratory mice. The upshot: We can't yet know if eating meat from CWD-infected animals is safe, and we aren't yet testing meat to determine the presence of CWD. So consumption of venison should be a personal choice.

Session VI -- Managing CWD in Free-Ranging Cervids

Rick Kahn from Colorado's Division of Wildlife delivered a synopsis of the Division's CWD policy statement. "It details three classes of zones, each with its own management goals," he said. "Class III discovery areas have documented CWD, but the extent of the disease is unknown. Our goal there is to eradicate it. Class II or elimination areas hold wild populations with greater but still controllable levels of infection. Class I or established areas include the endemic range where we see little chance for eliminating the disease." Kahn reported that current plans emphasize CWD management over recreation, and that "we'll increase research as we step up surveillance and try to communicate better with hunters about CWD."

In some areas, said Kahn, Colorado will experiment with deer density reductions - to half of current densities, achieved over three years and held there for five. "DOW is also culling small groups of deer in target areas known for CWD. Where culling is impractical, we'll take tonsil biopsies from live deer, then, if they test positive, relocate them by telemetry and kill them. Telemetry will help us track deer and elk moving from endemic areas - and hunt them down. To reduce deer numbers on a large scale, the Division may offer more than one deer tag per license and boost the allocation of antlerless and landowner tags."

Wyoming's first case of CWD occurred in a captive deer at the Sybille Wildlife Research and Conservation Education Unit in 1978. It cropped up in free-ranging elk eight years later. Tom Thorne of the state's Game and Fish Department reported that CWD surveillance programs began in 1983. Control measures have since included research, transport restrictions on cervids, removal of suspect animals and education. In 2001 the Wyoming Legislature established a state Wildlife/Livestock Disease Research Partnership and identified CWD as a priority issue. A WG&F internal committee on CWD assisted in drafting the National Plan for Assisting States, Federal Agencies and Tribes in Managing Chronic Wasting Disease in Wild and Captive Cervids. Said Thorne: "Wyoming will need nearly $2 million to fund CWD control work in FY 2003. The following year, full participation in state, regional and national research will cost nearly $2.2 million."

The Nebraska Game and Parks Commission has adopted several strategies for throttling the spread of CWD and reducing levels of infection where it does occur. "The aim, of course, is to eradicate the disease from the state," reported the Commission's Bruce Morrison. "We're working with the state Department of Agriculture in research and monitoring at captive cervid facilities." Morrison emphasized that research is a first response, adding that restrictions are also necessary. There's now a freeze on transport of deer and elk to re-establish or augment herds in Nebraska. To keep the public informed about CWD measures, "we'll make every effort to provide clear, accurate information through guides, media releases and Commission literature." Hunting is an important part of CWD management, he said, and hunters will be encouraged to have game checked for CWD - as are all cervids shot by state personnel. "But," cautioned Morrison, "where disease control is at odds with recreational hunting, disease control will take priority."

Nebraska's neighbor, South Dakota, only recently became one of the states afflicted by CWD. "Our first case in wild animals appeared in 2001," reported Ron Fowler, from the Department of Game, Fish and Parks. "Since 1997, our policy was to conduct general surveillance, but not intensively. We stepped up the program in 2002, collecting additional deer outside of hunting season and reducing deer density targets in units along the Nebraska line. CWD was reported just 15 miles south of that line in 2001." Fowler also said the state would test more aggressively those animals showing signs of malaise, and he stressed the importance of factual, up-to-date public information.

Tom Hauge, speaking for Wisconsin's Department of Natural Resources, agreed that communicating the status of CWD and disease strategies is "a constant and critical challenge." Since three infected whitetails were identified in February of this year, Wisconsin has acted aggressively to curb the spread of CWD. "As outlined in other sessions at this meeting, we've committed to reducing deer densities in areas where the disease has been found and to monitor hunter-killed deer on a large scale," said Hauge. "Most states will need financial and technical assistance from the federal government to deal with CWD." He implied that such help would likely follow, as this disease may have human health aspects.

Lloyd Fox from the Kansas Department of Wildlife and Parks emphasized that the biological effects of CWD are not its only threat. "Public confidence in game management, historically strong among hunters, depends partly upon the continued health of deer and elk populations." Kansas is now one of 13 states bordering a state where CWD has been confirmed, noted Fox. "As yet no new regulatory actions have been taken in-state by KDWP, the Kansas Animal Health Department or the USDA. But we're exploring multi-agency alliances to come up with CWD research and control measures that most effectively stem the spread of this disease." He reported that targeted surveillance had been done since 1996, and random testing on hunter-killed game since 1997. So far, none of 1167 animals tested have turned up with CWD - but that testing will be accelerated to include 1200 animals in 2002 alone. "We've also taken preemptive steps in northwest counties, reducing herd densities in the face of hunter opposition. We are encouraging hunters and landowners to take part in this program. At the same time, we're committed to delivering clear, factual updates to the public. Confusion about and fear of CWD could lead to the erosion of public trust in resource management agencies."

Because wild cervid densities in Alberta generally stay below five per square mile, and because the province has fewer than 1200 imported game farm elk and no game farm deer, "our exposure to CWD is limited." So declared Margo Pybus of the Alberta Wildlife Division, adding that surveillance of hunter-killed animals the past three years showed no CWD. One game farm was confirmed to have the disease. "If CWD appears, we'll take strong and immediate counter-measures," Pybus said. "We're already consulting with colleagues in Saskatchewan and the U.S. as to how we should handle the problem. Voluntary hunter surveillance, a rigorous game farm policy and a ban on baiting deer and elk should help keep Alberta CWD-free."

Questions of jurisdiction and responsibility crop up in crises. The burden for responding to CWD's threat lies mainly with states and provinces. Steve Williams, Director of the U.S. Fish & Wildlife Service, noted that Federal agencies will support states' efforts. "The National Park Service, Forest Service, BLM and BIA, as well as individual parks and refuges are working closely with state wildlife boards to control CWD," he said. "The U.S. Geological Survey will provide technical assistance; even NEPA will no doubt be involved in future policy talks and strategic plans." Williams added that federal funding would be needed to curb CWD.
One of the most pressing concerns in every state with aggressive surveillance is disposal of carcasses infected with CWD. Doris Olander and Joe Brusca of Wisconsin's Department of Natural Resources pointed out that an estimated 3 percent infection rate in the 20,000 deer the DNR plans to cull would leave 600 tainted carcasses. "Hunters will have killed the majority of these whitetails," they said. "And few, we suspect will want to keep the meat." Complicating disposal are the unknowns: Does CWD remain infectious after bodies decompose? How can we sample air, water and soil for CWD prions? "For now, it only makes sense to assume CWD can jump the species barrier to humans - at least as regards carcass disposal. Collectively, TSE agents are known to persist in the natural environment, so getting rid of dead deer is only part of our challenge." Wisconsin has investigated five disposal options:

1) landfilling at a modern, controlled site
2) burial at uncontrolled sites
3) dedicated rendering with controlled disposal
4) incineration
5) digestion by high-temperature, high-pressure alkaline hydrolysis

"Landfill and uncontrolled burial are high-capacity options that don't cost much," said Olander. "But they have no effect on the infectious agent, other than to localize it. Dedicated rendering is a popular method for disposing of cattle carcasses from BSE control programs. It can deactivate the agent. So can incineration, though with it comes the risk of airborne dispersal of CWD agent. Both these options are costly and may be impractical for large numbers of carcasses. Among incinerators, only ACDs (air curtain destructors) have the needed capacity." Low volume also plagues the digestion alternative, and the resulting liquid "requires special handling because of its high oxygen demand and pH."

Because of zoning restrictions and public concerns over CWD, uncontrolled burial has been eliminated as an option in Wisconsin. The others are still being considered. Local authorities will surely have a say as to how deer carcasses are handled - another compelling reason for continued public education efforts on CWD.

Michael Samuel from the USGS National Wildlife Health Center reiterated that Colorado has been engaged longer than any other state in the fight against CWD. "In May 2002, an independent panel of scientists reviewed the research progress and surveillance policies of Colorado's Division of Wildlife. The panel concluded that Colorado's CWD control program could serve as a model for other states, and that all such programs should include research, management and surveillance."

The effects of CWD go well beyond the biological, noted Brian Murphy of the Quality Deer Management Association. "Whitetail deer are the most economically important animals in the U.S. In 2001, nearly 11 million big game hunters spent over 153 million days afield, contributing almost $20 billion to the U.S. economy." Whitetail hunters generated most of this revenue. "While many hunters are as yet unaware of CWD," said Murphy, "many more are very concerned or confused about its effects on deer and venison." For that matter, so are deer managers, who have expressed alarm over the potential for CWD to turn hunters away from the sport. "If hunters stopped eating venison on a large scale, or became disenchanted with agency herd reduction programs, we'd quickly see a general resistance to doe shooting. Herd manipulation by sportsmen, important for regulating deer densities and age and sex ratios, would have to be replaced by regimented culling. Public opposition to that would be strong. Funding for all state wildlife management would be imperiled." Murphy urged an aggressive interagency public relations and information program to keep the public updated on CWD. These efforts should include, he said, conservation groups and the CWD Alliance.

Stephen Torbit from the National Wildlife Federation echoed Murphy's concerns. "CWD could profoundly affect the traditional model of wildlife management in the U.S. Not only might it affect hunter attitudes and participation, and land access; it could jeopardize state and federal management prerogatives." Torbit pointed to the Animal Health Protection Act, passed in 2002 largely because of the brucellosis found in Yellowstone Park bison. "AHPA has ominous implications for wildlife management because it places diseased animals under control of the USDA. Agricultural interests typically do not favor wildlife. CWD must not be allowed to drain professional biologists and ecologists of their ability to influence policy and to design and implement strategic management plans." A public discourse on CWD, he said, was the best way to ensure that traditional wildlife priorities would remain primary in state legislatures.

Late, inaccurate and sometimes misleading media coverage of CWD can undermine efforts to control the disease, said Jack Ward Thomas, formerly chief of the U.S. Forest Service. So can wrangling among professional scientists and resource managers over "turf." Thomas emphasized that CWD funding depends on a disciplined, coordinated effort among state and federal agencies and among conservation groups like the Boone and Crockett Club, Rocky Mountain Elk Foundation and Mule Deer Foundation. "We need accelerated research but also more effective communication to the general public. The CWD Alliance through its website will deliver a list of resources and experts, plus updated synopses of CWD news to both professionals and the public."

Better communication means more than clear enunciation of the known, Val Geist pointed out. "If you want progress, assemble experts from diverse fields and perspectives and encourage them to converse freely. What's inconsequential to one may prove a vital link to another. For example, the observation that CWD progresses down waterways has limited value unless you're familiar with the female dispersal mechanisms of mule deer. Then you realize it could advance faster among whitetails - and that it's probably not a disease spread by breeding males." He noted that the key to understanding CWD may require more study and discussions of wild cervid behavior. "We know, for instance, that the spread of BSE is linked to the eating of bone meal. But so far we haven't looked at bones as carriers. Does CWD reside there? How often do wild cervids chew bones?"

Geist reprimanded scientists and policy makers who failed to take advantage of the work of colleagues. He pointed out that scholarly debate outside structured forums is sadly lacking and mentioned elk ranching as an example of flawed policy from officials with insufficient background. "We're also moving from the extraordinarily successful model of North American wildlife management to one emphasizing husbandry of semi-domestic animals. Among the dangers is increasing unregulated transport of wild stock, which apparently can spread CWD." Geist suggested a shift away from case law dealing with wildlife to more effective treaty law.

In closing remarks, Len Carpenter from the Wildlife Management Institute urged caution in dispensing information about the disease. The public, he observed, has been alerted, and government agencies have been assembling information. Laboratories are working on better ways to detect CWD. Sensational headlines serve no purpose. Nor do reports by the scientific community that are hard for the lay person to understand.

Carpenter stressed that other diseases that affect humans - rabies, tuberculosis and West Nile virus - continue to merit research, and emphasized that clinical investigations alone will not "provide all the answers for management of CWD." He said there is no way to divorce the clinical aspects of CWD from its social and political ramifications, urging that attendees find ways to communicate in plain language the real risks of CWD. Speaking to concerns that extensive culling may be premature, Carpenter suggested that the costs of doing nothing may be very high, that the only way to further our knowledge of the disease while reducing transmission is vigorous thinning of herds in affected areas. He concluded by pointing out that volunteer conservation organizations have offered both funding and physical help to combat CWD.

One of the most useful sources of information now available to the public is the CWD website, on line since July, 2002. Established by the CWD Alliance, comprising the Rocky Mountain Elk Foundation, Mule Deer Foundation, Boone and Crockett Club, Pope and Young Club, Quality Deer Management Association, Wildlife Management Institute, National Shooting Sports Foundation and Cabela's, www.CWD-info.org keeps the public updated on the disease and efforts to combat it.

Symposium sponsors:

Colorado Division of Wildlife
Kansas Department of Wildlife and Parks
Nebraska Game and Parks Commission
Wyoming Game and Fish Department
National Shooting Sports Foundation
Quality Deer Management Association
Mule Deer Foundation
Rocky Mountain Elk Foundation
Pope and Young Club
Boone and Crockett Club
Whitetails Unlimited
Cabela's

CWD at a glance

· In 1967, mule deer held for research at Colorado State University exhibited an illness, later identified as chronic wasting disease.
· CWD is a form of transmissible spongiform encepalopathy (TSE), named for holes that give the brains of infected animals a sponge-like appearance. Bovine spongiform encepalopathy (BSE or mad cow disease) is another form of TSE. So is scrapie in sheep. CWD is always fatal.
· Like other TSEs, CWD is caused by infectious prions, mutant proteins that have the ability to change the structure of normal prion proteins in the brain. Prion accumulations also occur in the spinal cord, tonsils, eyes, spleen, pancreas and lymph nodes. It's unclear how CWD is spread.
· Though BSE has been implicated in variant Creutzfeld-Jakob disease, a TSE lethal to humans, there's no evidence at this time that CWD can be transmitted to humans.
· CWD's incubation period can last for months. Animals in the final (clinical) stages show emaciation, thirst, salivation, loss of coordination. But sure diagnosis is possible only by microscopic examination of the brain or, on live deer, tonsil tissue. The tonsil test does not work on elk.
· CWD is more prevalent where animals are concentrated. Game farms with CWD have a higher rate of infection, on balance, than do wild herds. Infection rates on wild mule deer range up to 13 percent in the endemic area of northeastern Colorado.
· Except in confinement, elk show lower incidence of CWD than do deer. Both whitetail and mule deer are vulnerable; CWD-infected deer have turned up from New Mexico to Wisconsin, and into Canada.
· To date, 29 states have tested 28,000 deer and elk for CWD. Responses to CWD-positive animals vary from "wait-and-see" to aggressive "surveillance" - culling and testing to determine the extent of the problem and reduce animal densities.
· New regulations to arrest CWD increasingly affect interstate transport of hunter-killed game. Hunters are required to submit deer and elk heads for testing in some areas. In others, testing is voluntary.
· If you hunt where CWD has been identified, keep knives used on meat away from the head and spine and internal organs of deer and elk. Wear rubber gloves for field dressing, and cut the meat yourself or insist that the butcher not mix your meat with that of other animals.
· To keep up to date on CWD, check the webside devoted to it: www.CWD-info.org.

Legislative

Policy

Baiting and Feeding

Bibliography

Meetings and Symposia

Testing Laboratories

Surveillance Strategies

CWD Experts

CWD Media Guide

CWD Brochure

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Media Photographs