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Wildlife Diseases

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Chronic Wasting Disease

What is Chronic Wasting Disease?
Chronic wasting disease (CWD) is a naturally occurring disease of the brain and nervous system in deer and elk that belongs to a family of diseases known as transmissible spongiform encephalopathies (TSE). This disease attacks the brains of deer, elk and moose and produces small lesions that eventually result in death. CWD is similar to another TSE disease, scrapie in sheep. No evidence exists that CWD affects humans or livestock.

Is CWD a new disease?
CWD was first recognized in captive mule deer in Colorado in the late 1960s, but was not identified as a TSE until the 1970s. CWD was first documented in wild elk in Colorado in 1981. Its discovery in wild deer in south-central Wisconsin in 2002 generated heightened attention from wildlife managers, hunters, and others interested in deer. CWD poses a significant threat to the deer and elk of North America and, if unchecked, could dramatically alter the future management of these species.

Captive deer infected with chronic wasting disease.

Captive deer infected with chronic wasting disease.

Why should we be concerned about CWD?
CWD is a relatively new disease and, consequently, there are a lot of unknowns. CWD does not cause an immediate widespread die-off of deer, but there may be long-term impacts to the herd if the disease is allowed to spread. Some scientists who have tried to predict the outcome on a deer population have described the disease as a 30 to 50-year epizootic with a potential to extirpate local populations. Others believe that the impacts might not be that severe. There are no proven solutions to eradicating the disease once present in wild populations. In addition, efforts by the state to contain or eradicate the disease are extremely costly and labor intensive.

How does CWD spread?
The method of CWD transmission is unknown, however there is strong evidence to suggest that abnormally-shaped proteins called "prions" are responsible. The agent responsible for this disease may spread directly through animal to animal contact or indirectly through soil or other surface to animal contact. It is thought that the most common mode of transmission from an infected animal is via saliva and feces. A recent study confirms that CWD prions can be shed into the enviroment in feces from animals showing no clinical signs of the disease and can contaminate the soil, leading to infection in other animals. CWD can be spread from region to region by the movement of captive deer or through the improper disposal of a harvested deer transported from a CWD infected area.

Where has CWD been found?
Prior to 2005, the disease had only been found in North America west of Illinois. In 2005, CWD was documented in captive and free-ranging herds in New York and in free-ranging herds in West Virginia. Since then, it has also been discovered in several other states. CWD has not been found in Connecticut or New England. States and Canadian provinces where CWD has been confirmed include: New York, Pennsylvania, West Virginia, Virginia, Maryland, Tennessee, Missouri, Arkansas, Mississippi, Illinois, Iowa, Minnesota, Wisconsin, Michigan, Ohio, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, New Mexico, Colorado, Wyoming, Montana, Utah, Saskatchewan, Alberta, Ontario, and Quebec. An updated map showing the states and Canadian provinces where CWD has been documented can be found on the Chronic Wasting Disease Alliance website.

The first reported case of wild moose infected with CWD occurred in Colorado in September 2005. Because moose do not congregate like deer and elk, cases of CWD in moose are expected to remain low.

In April 2016, the first detection of CWD was found in Europe. The Norwegian Veterinary Institute diagnosed CWD in a free-ranging reindeer in South-Norway. This was not only the first detection of CWD in Europe but also the first detection of natural infection in reindeer worldwide.

CWD Distribution Map of North America.

What is being done about CWD in Connecticut?
Connecticut and all other northeastern states have taken measures to prevent the spread of CWD. The Connecticut Department of Energy and Environmental Protection (DEEP) has taken the following CWD management actions:

  1. Connecticut, along with many other states, has banned the importation of live cervids (species in the deer/elk family) across state lines.
  2. An emergency regulation that was adopted in October 2005 to address concerns about CWD became permanent in September 2007. This regulation prohibits hunters from transporting into Connecticut any deer or elk carcasses or part thereof from any state where CWD has been documented, unless the meat has been de-boned. Specific wording of the regulation follows:
    • “Section 26-55-4: No person shall import or possess whole carcasses or parts thereof of any deer, moose, or elk from wild or captive herds from other states or Canadian Provinces where chronic wasting disease has been confirmed, including, but not limited to, Colorado, Wyoming, Utah, New Mexico, Montana, South Dakota, Kansas, Minnesota, Wisconsin, Illinois, Nebraska, Oklahoma, New York, West Virginia, Alberta and Saskatchewan. Any additional states* and provinces where chronic wasting disease is confirmed will be published in the Department's annual Hunting and Trapping Guide and on the Department's website. This provision shall not apply to meat that's de-boned, cleaned skullcaps, hides or taxidermy mounts.”
    • *See list above of additional states and Canadian provinces were CWD has been documented since this regulation was passed.
  3. In fall 2003, the DEEP, in cooperation with the UCONN Wildlife Conservation Research Center, initiated a surveillance program to determine if CWD existed in Connecticut. The program included testing deer using random surveillance of hunter-harvested and road-killed deer, and targeted surveillance of suspect animals (exhibited some symptoms consistent with CWD). Through random surveillance, over 230 samples were collected statewide and all tested negative for CWD. Deer were sampled from every county and deer management zone in the state. The extent of random sampling conducted in 2003 provides a high degree of confidence that CWD is not present in Connecticut. Through targeted surveillance, 4 suspect wild deer were collected and all tested negative for CWD (3 were hit by a vehicle and initially survived; 1 was an abandoned fawn being rehabilitated at a captive facility).
  4. In 2004, 298 randomly collected deer were tested for CWD from Deer Management Zone (DMZ) 11. Sampling efforts were focused in DMZ 11 because of the density of deer, relatively high number of captive deer facilities (6), and its close proximity to New York (New York has over 400 captive deer facilities with almost 10,000 deer and elk). Additionally, 6 suspect animals were collected and tested for CWD. All samples tested negative for CWD.
  5. From 2005-2011, a CWD surveillance program approved by USDA-APHIS was designed to focus sampling efforts in areas that were considered high and moderate risk. During this 7-year period, a total of 4,384 testable samples were collected from deer harvested during the archery, shotgun/rifle, or crop damage season and from deer found on roadways throughout the state.   
  6. Funding provided by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA-APHIS) was eliminated from the federal budget in 2012, so no CWD testing was conducted in 2012 or 2013. However, a joint partnership between Connecticut DEEP and the Stewart B. McKinney National Wildlife Refuge, with financial assistance from the U.S. Fish and Wildlife Service, National Wildlife Refuge System (USFWS-NWRS), allowed for testing to be conducted in 2014 through 2016. With the testing of over 32,000 deer in New York with no additional CWD cases being documented, the DEEP Wildlife Division no longer considers deer management zones 1, 6, and 11 to be high risk. Therefore, sampling will be stratified across all zones based on deer density. Since 2014, about 350 samples were collected each year. Since sampling efforts began in 2003, no cases of CWD have been detected in Connecticut or New England. Although additional funding sources for testing were lost in 2017, the Wildlife Division continues to collect samples to test for CWD. Hunters interested in donating deer heads for testing should keep the heads cool (not frozen) and arrange for them to be picked up by contacting (860-418-5921).

NEW REGULATION (effective in 2020): All use of natural deer urine products is prohibited, particularly for the purposes of taking or attempting to take or attract deer, or for the surveillance or scouting of deer. CWD can spread through exposure to infected deer urine. This new regulation safeguards Connecticut’s native deer population against unnecessary risk of contracting CWD.

U.S. Fish and Wildlife Service logo*A presentation on chronic wasting disease has been developed, which is ideal for hunting and conservation clubs. If you would like a presenter to visit your club or organization, please email the U.S. Fish and Wildlife Service Stewart B. McKinney National Wildlife Refuge at, or call 860-399-2513.

*An informational rack card on CWD is available for printing and distribution.

How can I tell if a deer has CWD?
In early stages of infection, animals show no symptoms. The incubation period can range from about 1-5 years. In advanced stages, infected animals begin to display abnormal behavior, such as staggering or standing with very poor posture, and carrying the head and ears in a lowered position. In later stages of the disease, infected animals become emaciated. Some symptoms of CWD also may be characteristic of other diseases and conditions (e.g., bacterial brain abscesses and epizootic hemorrhagic disease, or deer that have been injured in a deer-vehicle accident).

What should I do if I see a deer that exhibits symptoms of CWD?
Do not attempt to handle, disturb, kill, or remove the animal. Accurately document the location of the animal and immediately contact the DEEP’s 24-hour hotline at 860-424-3333. Arrangements will be made to investigate the report.

How is CWD diagnosed?
Prior to 2008, the only method to definitively diagnose CWD was to examine the brain, tonsils, or lymph nodes in a laboratory. No live-animal test, vaccine, or treatment for CWD existed. In 2008, researchers from the USDA-APHIS and Colorado State University evaluated and validated the first live rectal-tissue biopsy method for detecting chronic wasting disease (CWD) in captive and wild elk. The live rectal biopsy test appears to be nearly as accurate as a post-mortem diagnostic test. The key advantage to the rectal biopsy test is that it can be performed on live animals. With this technique, managers can detect CWD in animals not showing any signs of the disease and, thus, remove them to decrease the likelihood of infecting other individuals. This new live test will improve management and control of the disease, especially in captive settings.

What precautions should Connecticut hunters take?
Concern over CWD should not limit hunter willingness to harvest deer during the hunting season. No evidence exists that CWD affects humans or that it exists in Connecticut. Even in states where CWD is found, nobody has ever contracted CWD. Studies have shown that the abnormal prions that cause CWD do not transmit to species other than members of the deer family. However, as a precaution, public health officials recommend that humans avoid consuming meat from deer suspected of being infected with CWD. The CWD prion can be found within the meat of deer in the terminal stages of CWD. Higher levels of infected prions accumulate in tissues, such as the brain, spinal cord, spleen, lymph nodes, tonsils, and eyes, and as a precaution, contact with these items should be minimized.

Hunters should exercise the following precautions.

  • The use of natural urine-based lures is prohibited by a new state regulation that became effective in 2020.      
  • Avoid shooting, handling, or consuming any animal that is behaving abnormally or appears to be sick. 
  • Wear latex or rubber gloves when field dressing deer. 
  • Minimize the handling of and do not eat the brain, spinal cord, eyes, spleen, tonsils, and lymph nodes. 
  • De-bone meat from the animal. Do not saw through bone or cut through the brain or spinal cord (backbone). 
  • Wash hands and instruments thoroughly after field dressing is completed. Instruments should be placed in a 1:1 bleach/water solution for an hour and left to air dry before reusing. 
  • If you plan to hunt for deer or elk in another state, contact the state’s wildlife agency for the latest information on CWD and restrictions on transportation of harvested animals. 
  • To avoid possible introduction of high risk tissues from CWD-infected animals harvested outside of Connecticut, hunters should return with only boned-out meat, antlers with cleaned skull caps, hides without the head, and finished taxidermy mounts. This is mandatory if the deer was taken from a state known to have CWD. 
  • Dispose of carcasses by burying them or bringing them to landfills which accept carcasses. 
  • Carcasses from animals harvested in CWD-infected states and disposed of in the woodlands of Connecticut could result in an outbreak of CWD in our state.

NEW! The New York Department of Environmental Conservation adopted a rule change in 2019 that prohibits hunters from entering New York with whole carcasses or intact heads of deer, elk, moose, or caribou that they harvest anywhere outside of New York. Review the NYDEC's Big Game Importation Restrictions for more information.

Can I have my deer tested for CWD?
The Deer Program at Franklin Wildlife Management Area will be testing some deer as part of its annual surveillance for CWD. State testing typically occurs from mid-September through the end of January. If you would like to have your deer tested free-of-charge during the collection period, call the Franklin Wildlife Office (860-418-5921). Prior to testing, the deer's head should be kept cool but not frozen.

How can I find out more about CWD?
Persons wanting more information on CWD are advised to visit the following web sites:

Some information on this webpage was taken from CWD publications produced by other private organizations and state agencies.

Content last updated on March 12, 2020.