Chronic Wasting Disease (CWD)

It is illegal for hunters who travel to any other states and provinces to hunt deer, elk, moose, or caribou to transport any carcass parts that pose a risk of containing CWD prions. For more information, see Can I Bring Intact Deer Carcasses From Other States Into Maine?

What You Should Know About Chronic Wasting Disease

What is Chronic Wasting Disease?

Chronic Wasting Disease (CWD) is a fatal disease of the nervous system for members of the deer family, including white-tailed deer, elk, moose, and potentially caribou. The disease belongs to a family of diseases known as transmissible spongiform encephalopathies (TSEs). Other TSEs include scrapie in sheep, BSE or Mad Cow Disease in cattle, transmissible mink encephalopathy (TME) in captive mink, Feline spongiform encephalopathy (FSE) in cats, Creutzfeldt-Jakob disease (CJD) in humans, and variant CJD in humans (i.e., associated with Mad Cow Disease). Although similar in some respects, there is no known causal relationship between chronic wasting disease and any other TSE of animals or people.

Where Has CWD Been Found?

Currently, CWD is known to infect free-ranging deer and elk in portions of Colorado, Illinois, Kansas, Nebraska, New Mexico, New York, South Dakota, Utah, Virginia, West Virginia, Wisconsin, Wyoming, Alberta, and Saskatchewan. In addition, CWD has been found in captive/farmed elk or white-tailed deer herds in Colorado, Kansas, Minnesota, Montana, Nebraska, New York, Oklahoma, South Dakota, Wisconsin, Wyoming, Alberta, and Saskatchewan. Free-ranging moose have been detected with CWD in Colorado and Wyoming.

Is CWD Present in Maine?

There is no evidence that CWD is present in wild white-tailed deer or moose in Maine, or in any captive member of the deer family in Maine (i.e., elk, red, sika, and fallow deer). In addition to our CWD monitoring program each year, Department of Inland Fisheries and Wildlife (DIFW) biologists examine 6,000 to 8,000 hunter-killed deer and 2,000 to 3,000 moose for management purposes. While conducting other fieldwork, wildlife biologists observe hundreds of live deer during a typical year. Biologists also respond to hunters who contact us when they kill apparently ill or injured individuals. To date, DIFW biologists have not observed symptoms consistent with CWD in Maine.

No sick animals that may fit the clinical profile for CWD have ever been brought to the attention of the Department of Agriculture (DOA) or private veterinarians from among Maine's licensed deer farms. Since autumn of 2001, more than 1,900 farmed-raised elk and deer slaughtered in Maine have been tested for CWD. To date, all tests have been negative for CWD.

In a 1999 cooperative study, DIFW, DOA, and Center for Disease Control officials tested 299 hunter-killed white-tailed deer from the western mountains and foothills of Maine. All deer tested negative for CWD. From 2002 to 2009, DIFW biologists have collected samples and had tested over 5,600 hunter-harvested deer across the state. All deer tested negative for CWD.

At this time, we consider Maine to be CWD-free, based on available evidence. However, we are stepping up surveillance for wild deer and captive/farmed cervids to better evaluate CWD status in Maine, as is being done throughout the U.S.

photo of a buck whitetail deer in a field

What Causes CWD?

The prevailing theory is that an infectious, abnormally-shaped protein called a CWD prion (pree-on) causes certain other brain proteins to change to a diseased form. CWD prions then accumulate in the brain and other nervous tissues, where they physically damage affected nerve cells. Although the disease agent mainly targets nervous tissue, it occurs in most tissues of an infected animal, including muscle tissue. Infected individuals shed CWD prions in urine, feces, saliva, and eye fluids.

Which Species Have Contracted CWD?

To date, chronic wasting disease has been found only in mule deer, white-tailed deer, moose, and elk. However, based upon molecular similarities, CWD can probably be transmitted to all species in the deer family (cervids), including red deer, fallow deer, sika deer, and caribou. There is no scientific evidence that CWD can be naturally transmitted to species outside the deer family, including cattle, horses, sheep, goats, or swine.

Can CWD Spread to People?

There is currently no scientific evidence that CWD can infect humans. Nevertheless, public health officials recommend avoiding exposure to the CWD disease agents. . Recently, CWD prions were found in the muscle tissue of infected mule deer. Therefore, muscle tissue from an infected animal should be considered a potential source of prion infectivity.

What are the Signs of CWD in the Deer Family?

Chronic wasting disease is a slowly progressive disease; signs of sickness are usually not seen for 5 to 36 months after the disease agent enters the animal. Individuals showing symptoms of CWD tend to be 18 months of age or older. CWD damages the brain of infected animals, causing them to display unusual behavior, lose bodily functions, become very thin, and die within 1 to 12 months after symptoms of the illness first appear. Clinical signs identified in captive/farmed deer and elk include excessive drooling, excessive thirst, frequent urination, sluggish behavior, isolation from herd, teeth grinding, holding the head in a lowered position, and drooping ears. It should be noted that some of these symptoms can be seen after a very severe winter in Maine, when deer may appear very thin and weak. Although rare in cervids, rabies may produce some symptoms in common with CWD, such as erratic behavior, and drooling.

How is CWD Diagnosed?

Chronic Wasting Disease is usually diagnosed from dead animals. The "gold standard" test for CWD from involves Immunohistochemistry (IHC) techniques. This technique utilizes antibody based staining to color the tissue sample from the animal. This tissue sample is then evaluated using light microscopy. The deer tissues used in this assay come from the end of the brain stem (obex) or from lymph tissues in the neck. Other diagnostic tests utilize an enzyme-linked immunosorbant assay (ELISA), which indicates the presence of prions by changing the color of the test solution. This is a rapid technique that allows the testing of large numbers of samples at a relatively low cost. Currently most of the deer sampled for CWD in Maine are tested using this method. Any samples identified as having CWD prions using the ELISA technique would be verified using IHC. Live animals can be diagnosed for CWD by taking a biopsy sample from the animal's tonsils and analyzing the sample using IHC. However, this test is only used in certain cervid management situations.

How do deer, Moose, Elk or Caribou Get CWD?

The ways in which CWD is passed among animals is not well understood. CWD prions are very hardy; they are not easily destroyed by environmental factors, heat, or disinfection solutions. Therefore, CWD prions can remain in contaminated environments for many years. In mule deer, scientists have demonstrated that CWD prions are efficiently passed on from does to fawns. Furthermore, they suspect that this mode of transmission is important is sustaining CWD epidemics. The prions causing CWD occur in saliva, urine, feces, and eye fluids. Therefore, CWD is likely transmitted by direct contact with infected individuals, or by contact with contaminated soil, leaves, bedding, feed, or water. Frequent contact with other deer, such as what occurs when deer congregate around winter deer feeding stations or are kept in fenced-in enclosures increases the risk of transmitting diseases like CWD. Contact between wild and fenced cervids along fence lines can spread CWD in either direction. In addition, sites where CWD-infected cervids had died (or were placed) may become contaminated, as tissues decompose. Predators and scavengers also transmit CWD prions after consuming infectious parts of CWD-infected cervids and may influence the spread of CWD in the environment.

Are Commercial Deer Feeds Safe?

In theory, prions from CWD-infected deer could be present in commercial deer and elk foods, if they were formulated using rendering products (e.g., meat and bone meal or MBM) containing CWD-infected slaughter and processing wastes. In 1997, the U.S. Food and Drug Administration (FDA) placed a total ban on the use of MBM from cattle, sheep, goats, and cervids as a component in commercial feeds for ruminants (including wild and domestic deer and elk). Assuming all feed companies are complying with the FDA ban, commercial feeds commonly used to supplement the diets of captive/farmed or wild cervids would currently be free of CWD infectivity. We don't know, however, if MBM from CWD-infected deer or elk was ever incorporated into commercial ruminant feeds distributed in Maine prior to 1997. Nor do we know if commercial feeds currently formulated for non-ruminants (horse, swine, poultry, dog, and cat) sometimes contain MBM from CWD-infected deer or elk. When feeding wild deer or captive/farmed cervids, use only commercially available products formulated specifically for ruminants (deer, cattle, sheep, goats), or use whole grains (e.g. oats, corn) without supplements.

photo of a doe whitetail in the snowy woods

Winter Feeding of Deer

If supplemental feeds are free from CWD infectivity, the practice of feeding deer in winter cannot cause a CWD outbreak. However, the close contact and crowding typically seen among deer at winter feeding sites can greatly accelerate the spread of infectious diseases like CWD, if an outbreak occurs from other sources. Because of the long incubation period for CWD, an outbreak among white-tailed deer at feeding sites may spread to a large area long before clinically-ill individuals are observed. This would greatly hamper efforts to control the disease. Discontinuing the practice of winter feeding of deer makes great sense as a measure to prevent the spread of CWD. If you feed wild deer in Maine, please consider phasing out of the practice as soon as possible, as a disease prevention measure. DIFW has produced an excellent video highlighting the pitfalls involved in feeding wild deer. It is available at nominal cost at their online store.

Are Urine-Based Deer Lures Safe?

In most cases, the urine used to formulate commercial "doe-in-heat" or other buck lures is collected from captive deer or elk farms. If CWD prions are passed in the urine of CWD-infected deer and elk, the infective agent may be present in these lures. If present, then CWD prions may inadvertently be placed where susceptible Maine deer may contact and ingest them. Depending upon how the lure is handled, CWD contaminated deer lures could also be a source of exposure (and inadvertent ingestion) by people. In addition researchers are demonstrating that once prions are in the environment they may contaminate the area by remaining in the soils for years to come.

At this time, we do not know whether any captive/farmed deer or elk used by the lure industry have ever contracted CWD. To date, deer lures are not being checked for the presence of CWD prions. Until more is known about whether commercial deer lures pose a realistic risk of spreading CWD, we recommend that hunters use caution in spreading urine-based lures in the environment, and avoid placing the lures on their clothing or skin. Avoid placing deer lures on the ground or on vegetation where deer can reach them. Deer lures can be safely placed above deer height, allowing air circulation to disperse the scent. We would also strongly recommend using synthetic, non-urine based lures that have become available on the market until further research can show that deer urine does not pose a risk of containing infectious prions.

Why are We Concerned about CWD in Maine?

Where it occurs, CWD poses serious problems for wildlife managers, and the implications for free-ranging deer are significant. If it emerges in Maine, CWD could seriously reduce infected deer populations by lowering adult survival and de-stabilizing populations. Monitoring and control of CWD is extremely costly and would divert already scarce funding and staff resources away from other much-needed programs. Public concerns and perceptions about human health risks associated with all TSEs may erode hunter willingness to harvest deer, leading to unwanted population growth in areas that remained CWD-free. Major reductions in deer hunting would adversely affect Maine's economy, since deer hunting currently contributes more than $200 million to the economy of our rural state. Perceptions about the safety of farmed venison as human food could cause the collapse of Maine's $1 million deer farming industry. Preventing the arrival of CWD in Maine is an urgent state priority.

What is Being Done to Prevent CWD Outbreaks in Maine?

The Departments of Agriculture, Human Services, and Inland Fisheries and Wildlife are coordinating efforts to prevent CWD from entering the state. They are also working closely with other states, the federal government, and private organizations on various CWD-related topics. The activities cover 3 key areas.

Preventing introduction of CWD: The Maine Department of Agriculture revised its cervid importation rules in 2010, lifting an embargo that had been in place since 2002. Cervid importations are now permitted in conformance with the Department’s rules which require that animals come from 5-year CWD certified herds as well as from tuberculosis accredited-free herds.
The Department of Inland Fisheries and Wildlife has issued advisories covering:
1. Safe ways to import hunter-killed cervids (deer, elk, moose or caribou) from states harboring CWD;
2. Cautious use and placement of urine-based deer hunting lures, while the safety of these products can be evaluated;
3. Voluntarily modifying or ending the widespread practice of feeding deer in winter, as a preventive measure.

Monitoring wild and farmed deer for CWD: Efforts to monitor wild and captive/farmed deer in Maine for the presence of CWD, as are most other states are increasing. Plans include testing a representative, statewide sample of the deer harvest for CWD each year for the foreseeable future. Captive/farmed deer will be monitored for the presence of CWD (using on-farm health monitoring practices), and by testing certain farmed deer for CWD at slaughter.

Outreach: Good communication is important to disease prevention. Advisories to hunters, meat processors, taxidermists, deer farmers, and the public, suggesting ways to lessen the risks of introducing CWD into Maine, and providing basic facts about the disease will be issued.

What Can Deer, Moose, Elk and Caribou Hunters Do to Avoid CWD Risks?

If you plan to hunt deer, moose, caribou or elk in a state/province known or suspected to harbor CWD (see above for list of states and provinces), there are some commonsense precautions you should take to avoid handling, transporting, or consuming potentially CWD-infected specimens. The following precautions are adapted from the Wisconsin Department of Natural Resources:

General precautions:

- Do not eat the eyes, brain, spinal cord, spleen, tonsils, or lymphnodes of any deer.
- Do not eat any part of a deer that appeared sick.
- If your out-of-state deer is sampled for CWD testing, wait for the test results before eating the meat.

Field dressing:

- Wear rubber or latex gloves while handling the carcass.
- Minimize contact with the brain, spinal cord, spleen, and lymphnodes (lumps of tissue next to organs or in fat and membranes) as you work.
- Use a hunting knife, not knives used at the dinner table.
- Remove all internal organs for proper disposal by burial, or other means that prevents contact by live deer.
- Clean knives and equipment of residue and disinfect in a 50/50 solution of household chlorine bleach and water for 1 hour.

Cutting and processing:

- Wear rubber or latex gloves.
- Minimize handling brain or spinal tissues. If removing antlers, use a saw designated for that purpose only.
- Do not cut through the spinal column except to remove the head. Use a knife or saw designated only for this purpose.
- Bone out the meat from the deer and remove all fat and connective tissue (the web-like membranes attached to the meat). This will also remove lymph nodes.
- Dispose of feet, hide, brain and spinal cord, bones, and head by burial, or other means that prevents contact by live deer.
- Thoroughly clean and sanitize equipment and work areas with 50/50 bleach water after processing.
- If processing deer from out-of-state CWD management or eradication zones, keep meat and trimmings from each deer separate.

Can I Bring Intact Deer, Moose, Caribou or Elk Carcasses From Other States Into Maine?

To prevent the introduction of CWD into Maine and pursuant to12 MRSA Part 12, Chapter 903, Subchapter 2, §10103, 2. and § 10104. 1., it is illegal for hunters who travel to any other states and provinces to hunt deer, elk, caribou or moose to transport any carcass parts that pose a risk of containing CWD prions with the exception of New Hampshire. Hunters may return to Maine only with boned-out meat, hardened antlers (with or without skull caps), hides without the head portion, and finished taxidermy mounts. If still attached, skull caps should be cleaned free of brain and other tissues.

At this time, no state or province can claim to be free of CWD - - too little monitoring has been conducted to realistically evaluate CWD status. Accordingly, this regulation against importing potentially high-risk carcass parts applies to wild deer, caribou, moose or elk taken in any state and province outside Maine (with the exception of New Hampshire), and to cervids killed in commercial hunting preserves everywhere.

Can I Get My Maine Deer, Caribou, Moose or Elk Tested for CWD?

Currently, there is a high demand for CWD testing in states known to harbor CWD. Unfortunately, existing laboratory tests for CWD are expensive, time-consuming, and they can only be performed at a small number of federally-approved labs. Although our system can accommodate enough samples (less than 1,000) from farm-raised and wild deer to scientifically monitor for CWD, we are not able to routinely test hunter-killed deer, moose, caribou or elk in Maine at this time.

black and white line drawing of a doe whitetail deer

What If I See a Deer or Moose Showing Signs of CWD in Maine?

Hunters and wildlife watchers should realize that deer (and moose) are subjected to a wide array of illnesses and injuries that may cause unusual behavior or unthrifty appearance. For example, healthy deer at feeding sites are easily approached by people, these same deer may appear thin and unhealthy for weeks following a severe winter, and deer injured by vehicles or predators may limp and appear sick. Reporting all encounters of sick deer by the public would quickly overwhelm state agency personnel. Moose also may appear unhealthy in late winter if they carry heavy tick infestations and lungworm infections.

On the other hand, if CWD were to emerge in Maine, early detection of diseased individuals provides the best means we have of controlling or eradicating the disease. Therefore, if you observe a deer or moose that clearly shows symptoms of CWD, do not kill or handle the deer. Report the sighting to an Inland Fisheries and Wildlife biologist or game warden (see phone numbers below). Again, report only deer showing all or most of these CWD symptoms: extreme thinness, unaware or unafraid of people, shaking or unable to walk normally, drooling, can't raise the head, and ears drooping.

Wildlife Biologists and Game Wardens:

Ashland – (207) 435-3231
Bangor – (207) 941-4466
Enfield – (207) 732-4132
Gray – (207) 657-2345
Greenville – (207) 695-3756
Jonesboro – (207) 434-5927
Sidney – (207) 547-5318
Strong – (207) 778-3324

For More Information:

The following websites are good sources of information about Chronic Wasting Disease:


If you have questions about CWD prevention efforts in Maine, the following contacts are suggested:

Hunting, monitoring of wild deer:

Information Center, Dept. of Inland Fisheries and Wildlife
284 State Street, 41 SHS, Augusta, ME 04333-0041
(207) 287-8000

Regulation of Captive/Farmed Deer or Elk:

Michele Walsh, DVM, State Veterinarian
Maine Department of Agriculture
Conservation & Forestry
Augusta, ME 04333
Office: 207-287-7615
Cel: 207-215-6727

Questions about CJD, variant CJD, or other Human TSE's:

Maine Dept. of Human Services, Bureau of Health,
SHS #11, Augusta, ME 04333-0011
(207) 287-7087