Chronic wasting disease (CWD) belongs to a group of diseases known as transmissible spongiform encephalopathies (TSE). It affects cervids, or members of the deer family. CWD causes a characteristic spongy degeneration of the brain leading to loss of body condition, altered behavior, and death. Though many observers try to compare CWD with mad cow disease, they are not the same. Mad cow disease stems from a different type of TSE that occurs in cattle.
CWD was first recognized as a clinical "wasting" syndrome in 1967 in mule deer at a wildlife research facility in northern Colorado. In the mid-1980s, CWD was detected in free-ranging deer and elk in contiguous portions of northeastern Colorado and southeastern Wyoming. In May 2001, CWD was also found in free-ranging deer in the southwestern corner of Nebraska. That limited area of northern Colorado, southern Wyoming and southwestern Nebraska is referred to as the CWD “endemic area.” CWD appears to afflict 4-8 percent of the deer in this region. The disease does not appear to limit free ranging elk or deer population numbers in the wild, though longer term studies are needed to evaluate long-term effects.
CWD also has been diagnosed in game-farm elk herds in a number of states and in two Canadian provinces. The first case among farmed elk herds in the United States was diagnosed in 1997 in South Dakota.
In 2002, Wisconsin became the first state east of the Mississippi River to find CWD in wild deer populations. Fearing rapid spread of the disease in whitetails, Wisconsin launched an unprecedented effort to eradicate the disease by depopulating deer from a 450-square-mile area.
Late in 2002, CWD was found in Illinois. In March of 2005, CWD was found in 2 game farm deer herds in New York.
CWD has been detected in both wild and captive deer and elk populations in isolated regions of North America. to date, CWD has been found in Colorado, Illinois, Kansas, Minnesota, Montana, Nebraska, New Mexico, Oklahoma, South Dakota, Utah, Wisconsin and Wyoming in the United States, and in Saskatchewan and Alberta in Canada.
Aggressive testing of hunter-harvested animals across the nation is attempting to further define the “outbreak area.”
Species that have been affected with CWD include elk, mule deer, white-tailed deer and black-tailed deer. Ongoing research is further exploring the possibility of transmission of CWD to other species. Closely related TSE diseases have been documented in cattle, mink, domestic sheep, exotic ungulates, and wild and domestic cats.
The agent responsible for CWD has not been completely characterized. There are three main theories on the nature of the agent that causes CWD: 1.) The most widely accepted theory is that the agent is a prion, an abnormal form of cellular protein that is most commonly found in the central nervous system and in lymphoid tissue. The prion "infects" the host animal by promoting conversion of normal cellular protein to the abnormal form; 2.) The agent is an unconventional virus; or 3.) The agent is a virino, or "incomplete" virus composed of nucleic acid protected by host proteins. The CWD agent is smaller than most viral particles and does not evoke any detectable immune response or inflammatory reaction in the host animal. Based on experience with other TSE agents, the CWD agent is assumed to be resistant to enzymes and chemicals that normally break down proteins, as well as resistant to heat and normal disinfecting procedures.
It is not known exactly how CWD is transmitted. The agent may be passed by infected animals in feces, urine or saliva, but considerable contact is probably required for transmission to occur. CWD appears more likely in areas where elk or deer are crowded or where they congregate. Artificial feeding of wild elk and deer may compound the spreading of CWD. Animals born in captivity and those born in the wild have been affected with the disease. Based on epidemiology, transmission of CWD is thought to be lateral or from animal to animal; although maternal transmission may occur, it appears to be relatively unimportant in maintaining epidemics.
Cases of CWD occur most commonly in adult animals, but also in yearlings. The disease is progressive and always fatal. The most obvious and consistent clinical sign of CWD is weight loss over time. Behavioral changes also occur in the majority of cases, including decreased interactions with other animals, listlessness, lowering of the head, blank facial expression and repetitive walking in set patterns. In elk, behavioral changes may also include hyper-excitability and nervousness. In game farms, affected animals continue to eat grain but may show decreased interest in hay. Excessive salivation and grinding of the teeth also are observed. Most deer show increased drinking and urination.
Research is being conducted to develop live-animal diagnostic tests for CWD. Early results indicate that a new live-test utilizing tissues from an animal’s tonsils may be viable in deer, but so far has been ineffective in elk. Currently, the only definitive diagnosis involves a microscopic examination of the brain, tonsils or lymph nodes performed after death. Gross lesions seen at necropsy reflect the clinical signs of CWD, primarily emaciation. Aspiration pneumonia, which may be the actual cause of death, also is a common finding in animals affected with CWD. On microscopic examination, lesions of CWD in the central nervous system resemble those of other TSEs. In addition, scientists use a technique called immunohistochemistry to test brain tissue for the presence of the abnormal prion protein to diagnose CWD.
There are no reported cases of natural transmission of CWD from infected elk or deer to domestic sheep or cattle. Several investigations are underway to further study this question.
The World Health Organization has reviewed available scientific information and found that currently there is no evidence that CWD in deer or elk can be transmitted to humans. During the period 1997-1998, three cases of sporadic Creutzfeldt-Jakob disease (CJD) occurred in the U.S. in young adults. These individuals had consumed venison. This led to speculation about possible transmission of CWD from deer or elk to humans. However, review of the clinical records and pathological studies of all three cases by the Centers for Disease Control and Prevention in Atlanta, Georgia, did not find a causal link to CWD. Nonetheless, wildlife officials in the Rocky Mountain region suggest special meat-handling guidelines for hunters. These may be found at www.cwd-info.org.
Do not shoot or handle an elk or deer that is acting abnormally or appears to be sick. When field-dressing game, wear rubber gloves and minimize the use of a bone saw to cut through the brain or spinal cord (backbone). Bone out the meat. Minimize contact with and do not consume brain or spinal cord tissues, eyes, spleen, or lymph nodes. Always wash hands thoroughly after dressing and processing game meat. For more, visit www.cwd-info.org.
Many states are currently aggressively testing wild elk and deer for CWD. In 2002, the disease has been found in Illinois, New Mexico, Colorado, Wyoming, Nebraska, South Dakota and Wisconsin. Outside of the CWD “endemic area,” most new cases of CWD have been found in close proximity to game farms. Currently, Colorado is attempting to test a large sample of cervids from an area near Craig, where an outbreak among wild deer appears traceable to a nearby game farm.
CWD surveillance of game farming operations is not yet regulated by the federal government, but some states, in cooperation with the industry, conduct CWD surveillance and have captive herd certification programs. A cooperative surveillance program began in 1997 between some states and the U.S. Department of Agriculture (USDA) and its Animal and Plant Health Inspection Service (APHIS). State agriculture and wildlife agencies, USDA, APHIS and the captive cervid industry are nearing adoption of a federal program for CWD.
The Rocky Mountain Elk Foundation recognizes chronic wasting disease as one of many threats to elk. The Foundation’s involvement in CWD issues must be carefully measured and balanced against the most significant and long-term threat to elk habitat loss. While the Elk Foundation maintains its focus on permanent land protection and habitat stewardship in elk country, it is supporting the leaders in the fight against CWD by working to offset the media sensationalism and public hysteria that too-often surround this disease. Early in 2002, the Elk Foundation helped found the “CWD Alliance” along with Boone and Crockett Club and Mule Deer Foundation. More conservation-minded organizations and companies quickly joined, offering their resources to help this collaborative project meet its goals. The main purpose is to disseminate accurate, responsible information about chronic wasting disease. The primary vehicle is a Web site, www.cwd-info.org, which is updated frequently.
In addition to its activities in the CWD Alliance, and supporting the leaders in the fight against CWD, the Elk Foundation is committed to:
- Connecting media with scientists. The Rocky Mountain Elk Foundation co-sponsored the first scientific symposium surrounding CWD. The event was held August 6-7 in Denver. More than 500 people from state resource agencies, CWD research labs, and news outlets were in attendance. The 2nd International CWD Symposium will be held July 12-14, 2005 at the Monona Terrace Convention Center in Madison, Wisconsin.
- Funding CWD research and education initiatives. The Rocky Mountain Elk Foundation and its Project Advisory Committees have never rejected a request for funding in CWD research or education. Research has helped advance scientific knowledge of the disease, track its course through infected animals, and identify elk that may have contracted CWD. Educational efforts have connected the science of CWD to the media and public. The following projects are completed, ongoing or pending.
Year |
Project Title
|
Partner(s)
|
RMEF Funding
|
1999 |
South Dakota Wild Deer & Elk CWD Surveillance |
South Dakota Department of Game, Fish and Parks
South Dakota State University |
$5,241
|
2001 |
National CWD Symposium Seed Money |
Kansas Department of Wildlife and Parks
Nebraska Game and Parks Commission
Kansas Cooperative Fish and Wildlife Research Unit |
$1,000
|
2001 |
Oregon Wild Deer & Elk CWD Surveillance |
Oregon Department of Fish and Wildlife
United States Department of Agriculture
USDA - Animal and Plant Health Inspection Service
Oregon Hunters' Association
|
$5,681
|
2002 |
The Wildlife Society Western States Student Conclave CWD Workshop |
Colorado State University College of Natural Resources
Colorado State University Department of Fisheries
The Wildlife Society - Colorado State University Student Chapter
The Wildlife Society - Colorado Chapter
The Wildlife Society - Central Plains and Mountain Chapter |
$1,500
|
2002-03 |
CWD Alliance Support |
Mule Deer Foundation
Boone and Crockett Club
CWD Alliance Partners and Sponsors |
$17,107
|
2002 |
CWD Alliance Comprehensive Website Development |
Boone and Crockett Club
The Mule Deer Foundation
Pope and Young Club
|
In-kind
|
2002 |
Dynamics and Early Detection of CWD in Elk |
University of Wyoming
Wyoming Game and Fish Department
Colorado Division of Wildlife
Agriculture Research Service |
$10,000
|
2002 |
National CWD Symposium Sponsorship |
Colorado Division of Wildlife
Kansas Department of Wildlife and Parks
Nebraska Game and Parks Commission
Wyoming Game and Fish Department
Boone and Crockett Club
The Mule Deer Foundation
National Wildlife Federation
|
$1,092
|
2002 |
California Department of Fish and Game CWD Syposium Stipend |
California Department of Fish and Game |
$358
|
2003 |
CWD Surveillance in Wild California Elk |
United States Department of Agriculture
California Department of Fish and Gam |
$4,000
|
2003 |
Wisconsin CWD Public Education Signage |
Wisconsin Department of Natural Resources |
$2,000
|
2003 |
Southeastern Cooperative Wildlife Disease Study |
University of Georgia - Southeastern Cooperative Wildlife Disease Study |
$16,500
|
2003 |
CWD Wisconsin Informational Pamphlet |
Wisconsin Department of Natural Resources
Natural Resources Foundation of Wisconsin
Whitetails Unlimited
|
$3,000
|
2004 |
CWD Alliance Support |
Boone and Crockett Club
The Mule Deer Foundation
CWD Alliance Partners and Sponsors
|
$10,000
|
2004 |
Shedding Light on CWD Educational CD |
CWD Alliance Partners and Sponsors
American Outdoor Productions
Bowhunting Preservation Alliance
|
In-kind
|
2005 |
CWD Alliance Support |
Boone and Crockett Club
The Mule Deer Foundation
CWD Alliance Partners and Sponsors
|
$10,000
|
|
|
|
Total $87,479
|
- Supporting state’s elk management programs. The Rocky Mountain Elk Foundation recognizes that it doesn’t have the local knowledge or expertise to manage wildlife resources at the state level. Instead, we always have been a facilitator working cooperatively with states that invite our participation in elk conservation or restoration programs. CWD will not change that role. The Foundation stands ready to support and assist state resource leaders in all their elk conservation decisions, from restoring elk to native ranges, to enacting moratoriums on all new elk reintroductions.
- Continuing coverage. CWD is consistently covered in the Foundation’s official magazine, Bugle. Past articles include: