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Can we control Chronic Wasting Disease?

Pennsylvania stands at crossroads. Does the Game Commission continue current chronic wasting disease (CWD) management actions that are following trends seen in other states, or implement new actions to try to turn the tide?

To date, the percent of the deer population affected by CWD is following the pattern seen in West Virginia and Wisconsin (See figure below). If unchanged, 25 percent of the deer population could be infected with CWD in the next 10 years.

Deer infected with CWD chart

CWD is too serious to ignore. CWD is always fatal and there is no treatment. CWD reduces deer survival leading to reduced hunting opportunities and declining populations.

CWD is spreading to new areas annually. CWD prions remain in the environment for years and cannot be treated.

And although effects of CWD on people are unknown, history with related diseases (for example, Mad Cow Disease being transmitted to humans) demonstrates a need for action to minimize human exposure to CWD.

The agency is using research to explore ways to mitigate CWD in the Commonwealth.


Research launched in 2018 is looking at the social and biological implications of efforts to CWD.

The study area is located within Disease Management Area 2 (DMA2) where the first free-ranging deer infected with CWD were detected in 2012. This area leads the state in both number and concentration of CWD cases.

Disease Management Area 2 study area map

Expand AllClick here for a more accessible version

Research objectives: 

1. Estimate deer survival and population abundance

To estimate survival and dispersal in the study area, biologists captured and marked 112 white-tailed deer in 2018 using drop nets. Capture efforts continue in the study area in 2019 with the use of Clover traps as well as drop nets.

Information on the capture techniques used can be found here.

What’s wrong with feeding wildlife?

Disease transmission is the biggest concern with feeding wildlife. Artificially congregating wildlife through feeding alters natural foraging behavior causing changes in movement and distribution. The artificial competition from crowding at feed sites leads to increased fighting and injury.

Pennsylvania is facing Chronic Wasting Disease (CWD) in deer, and mange in bears. Both diseases were either absent or much less likely to be found a decade ago and both diseases are now escalating in Pennsylvania. Wildlife feeding brings animals into closer contact with one another and for longer periods of time than typical. Increased contact increases exposure.

Feeding sites harbor and concentrate disease agents deposited by infected animals creating a reservoir of disease. Healthy animals become infected by ingesting contaminated feces, eating contaminated feed or nearby vegetation, or in the case of mange and bears, by rubbing against contaminated surfaces where mites persist.

Wildlife feeding can increase transmission of CWD and mange. Infectious agents, like the CWD prion, can be shed in oral and respiratory droplets and other bodily secretions like urine and feces. CWD is always fatal to deer and elk.  Mange, which is caused by mites on the surface of the skin, is highly contagious and a common cause of mortality in bears. These diseases impact wildlife populations by causing mortality or debilitating illness. Other diseases such as bovine tuberculosis, salmonellosis, toxoplasmosis, lungworms, and tapeworms can also be transmitted by feeding.

Risks for nontarget species. Items used to attract big game will draw squirrels, raccoons, opossums, rodents, skunks, and foxes, directly or indirectly. Many of these species are known carriers of transmissible disease, such as rabies, canine distemper, parvovirus, leptospirosis, Baylisascaris and ascarid roundworms, avian pox, and trichomoniasis, several of which have important human health implications.

Feeding blurs the lines between wild versus domestic and free-ranging versus private. Citizens who recreationally feed big game frequently assume a feeling of ownership over these animals. This violates the public trust doctrine that wildlife is a publicly owned resource. Wildlife associate food with humans resulting in habituation and wild animals become indifferent toward humans or human activity. This can lead to increases in vehicle strikes, property damage caused by wildlife, and other nuisance wildlife problems such as human-conditioned bears rummaging through trash or human injury from habituated wildlife getting too close. Some wildlife, like bears, can have home ranges that span 10 square miles or more. Habituation depreciates wildlife's natural independence from people, ultimately, "de-wilding" animals for human convenience.

What is avian influenza (bird flu)?

Avian influenza is a common disease of birds that rarely infects humans. These viruses are classified as having low pathogenicity or high pathogenicity based on the severity of the illness they cause in poultry and most are not considered a public health threat.

Fact: The highly pathogenic H5N1 strain of avian influenza has not been detected in North America.

Fact: Highly pathogenic strains, like highly pathogenic H5N1, cause severe illness and rapid death in poultry. H5N1 has caused the largest and most severe outbreaks in poultry on record.

Fact: At present, the highly pathogenic H5N1 strain of the bird flu virus does not easily infect people and rarely spreads from person to person.

Fact: In cases where the H5N1 strain has infected humans, it is a serious disease; while only about 200 people are known to have contracted the disease, about half of them have died.

2. Estimate deer dispersal rates and describe dispersal paths

To estimate survival and dispersal in the study area, biologists captured and marked 112 white-tailed deer in 2018 using drop nets.  Capture efforts continue in the study area in 2019 with the use of Clover traps as well as drop nets. 

Information on the capture techniques used can be found here.  

Diseases of concern

​Each of these diseases can be passed from animal to animal and spreads more quickly when animals are congregated at wildlife feeders or other artificial feeding sites.

CWD – Chronic Wasting Disease is a transmissible spongiform encephalopathy (TSE) that affects deer and elk. This always-fatal disease attacks the animal's brain and causes loss of normal bodily functions. The disease is similar to Mad Cow disease in cattle. CWD can remain infectious in the environment for years, and there is no cure. Deer infected with CWD have been found in numerous locations in Pennsylvania. Learn more.

Mange is a contagious skin condition caused by burrowing mites that affects wildlife worldwide. In some cases, mange can be fatal, debilitating an infected bear through hair loss, damaged skin, secondary bacterial infections, and starvation. Mange in Pennsylvania black bears has progressively increased in frequency and distribution, and is causing concern as cases expand into other Mid-Atlantic states. Wildlife feeding is believed to contribute to the spread of mange by facilitating contact with infected bears or contaminated objects rubbed by infected bears. Learn more.

Bovine tuberculosis is a bacterial disease of the respiratory system. The disease can be fatal to white-tailed deer, elk, black bear, bobcat, coyote, opossum, raccoon and fox, as well as domestic livestock. At present, there have been no confirmed cases of bovine tuberculosis in Pennsylvania's wildlife, but it has been diagnosed in wildlife populations in other states. Learn more.

Lactic acidosis or grain overload is a metabolic disease associated with feeding of deer and elk. Lactic acidosis is the fatal disruption of the body's acid-base balance in the rumen caused by eating foods for which the rumen is not currently adapted, such as corn in winter. Animal deaths due to lactic acidosis are documented annually in Pennsylvania. 

Foundering – High carbohydrate foods like corn can also cause foundering – a condition of the hoof related to disruption of the acid-base balance in the rumen. Pain in the growth plate of the hoof causes an irregular step and hooves grow much longer due to atypical contact with the ground. This condition has been documented in Pennsylvania.

Aflatoxicosis is a condition where toxins produced by fungi on spoiled feed, particularly grains, cause mortality to animals including wild turkeys.

Hair loss in deer is a newly emerging disease syndrome. Mild to marked hair loss and soft tissue inflammation of the muzzle are two newly-recognized conditions associated with feeding. The cause of the hair loss syndrome is unknown, but many parasitic, infectious, and toxic causes have been considered. Soft tissue inflammation of the muzzle is a kind of bacterial infection not previously seen in white-tailed deer.

What is a bird flu pandemic?

Influenza pandemics are caused by the global spread of a new influenza virus that has adapted to humans and is easily transmitted from person to person.

Fact: There currently is no human influenza pandemic occurring anywhere in the world.

Fact: If the current H5N1 is detected in North America, it will not signal the start of a flu pandemic.

Fact: At this time, the H5N1 virus is not capable of causing a flu pandemic.

Fact: Scientists are concerned that H5N1, or another strain of influenza, could mutate to become a human flu virus that is easily transmitted from person to person and which could trigger an influenza pandemic.

3. Monitor proportion and location of sampled deer that are infected with chronic wasting disease (CWD)

​Population data are being collected using distance sampling. Thirteen routes throughout the study area are completed multiple times before and after hunting seasons. In spring of 2018, total distance surveyed was 160 miles and 3,146 deer were observed. 

Public Involvement

Because of the increasing threats to our wildlife populations, an agency Wildlife Feeding Committee and a citizen Advisory Committee formed to look at the problem and propose possible solutions. Participants selected for the Advisory Committee were intended to represent a variety of stakeholders from the Northcentral Region. The Advisory Committee includes representative(s) from Texas Blockhouse, Sinnemahoning Sportsman, Grays Run Gun Club, Pennsylvania State Camp Association, National Wild Turkey Federation, PA Chapter of Backcountry Hunters & Anglers, Bonnell Run Hunting & Fishing Club, State Representative Garth Everett's office, PA Great Outdoors Visitors Bureau, and Game Commission Forest Game Cooperators: Collins Pine/Kane Hardwood and Seneca Resources Company LLC.

Advisory Committee members met several times to discuss the problem and offer possible solutions. Then the Wildlife Feeding Committee drafted a plan based on their input. Open houses are collecting additional public input from a larger group of constituents throughout July and August. In September the agency hopes to adjust the proposed recommendations and seek final public input on a plan regarding the feeding of big game in Pennsylvania. The Game Commission Executive Office can expect final recommendations in October.

Pennsylvanian's have an increasingly-serious problem that shouldn't be ignored. The Game Commission believes that it is vitally important for the agency to work together with the citizens of Pennsylvania to address this very difficult problem. With greater public input in this process, we believe we can achieve that goal.

How is avian influenza spread?

Legal and illegal movement of infected birds; poultry products; contaminated materials, equipment and vehicles; as well as wild bird migration are ways that H5N1 is spread.

Fact: The highly pathogenic H5N1 strain has spread to large geographic areas in Asia, Europe and Africa, where it has primarily affected domestic poultry.

Fact: Most human cases of avian influenza have occurred in people who have had close contact with infected poultry or have eaten infected poultry that was improperly cooked.

4. Evaluate effectiveness of disease management activities on CWD

During 2017 in the study area, biologists detected CWD in 27 of 559 sampled deer (i.e., proportion of sample where CWD was detected = 0.05). Samples were collected from deer that were road-killed, harvest-harvested, or exhibiting signs of CWD.

In 2018, CWD has been detected in 17 of 575 deer sampled in the study area.  As of February 2019, results are still pending for 274 samples in the study area. 

Advisory Committee Proposal

There is broad support from the Advisory Committee to extend the current regulations prohibiting feeding of bear and elk to include deer and turkey. There was little support from the Advisory Committee members to ban the feeding of all wildlife, primarily because of the wide use of bird feeders. Expanding the feeding ban to include all big game would address some of the concerns related to wildlife feeding, while allowing for limited feeding of birds.

We understand that banning the feeding of all big game will be a major change, particularly to those who take great personal satisfaction from feeding wildlife. For some, feeding may be their primary means of connecting with Pennsylvania wildlife. We want all Pennsylvanians to enjoy and value our great wildlife resources. Considering this emotional connection, the Advisory Committee understood the problems caused by feeding and the majority supported its prohibition. The committee also supported banning the use of urine (both natural and synthetic), scents and lures used to hunt big game. 

(Proposed language)
137.33 Feeding of certain wildlife prohibited.

It is unlawful to intentionally lay or place food, fruit, hay, grain, chemical, salt or other minerals anywhere in this Commonwealth for the purpose of feeding big game to include Elk, Deer, Bear and Turkey, or to intentionally lay or place food, fruit, hay, grain, chemical, salt or other minerals that may cause big game to congregate or habituate an area.  If otherwise lawful feeding is attracting big game, the Commission may provide written notice prohibiting the activity.

Who is responding? What's being done?

The U.S. National Strategy for Pandemic Influenza is guiding the U.S. preparedness and response to an influenza pandemic, with the three goals: Preparedness and Communication; Surveillance and Detection; and Response and Containment.

Federal and state domestic animal, wildlife and public health agencies are working closely to prepare, prevent and respond to the potential introduction of the highly pathogenic H5N1 virus into the United States.

The U.S. Departments of Interior, Agriculture and Health & Human Services are working with other federal and state agencies in implementing a National Early Detection System for Highly Pathogenic H5N1 Avian Influenza in Wild Migratory Birds focused on:

  • Rapid investigation of wild bird mortality in the U.S;
  • Surveillance in live wild birds;
  • Surveillance in hunter-killed wild birds;
  • The use of sentinel species to detect H5N1 and
  • Environmental sampling of areas frequented by wild birds.

PGC biologists are sampling live Canada geese and mallards statewide, as well as scaup (a species of diving duck), taken by hunters on Lake Erie to test for avian influenza. Water samples from areas where waterfowl congregate are also being taken and tested for avian influenza. The PGC is occasionally finding various forms of the low pathogenicity Avian Influenza virus in these samples. This is expected because these viruses regularly coexist with these birds. The presence of the low pathogenic virus poses no threat to human health.

Fact: H5N1 has been eliminated from countries such as Japan, South Korea and Israel by quick and efficient eradication of the disease in domestic poultry.

5. Evaluate public support for CWD management activities

Surveys were sent to 1,982 random hunters and landowners in the study area. A total of 983 surveys were returned, and after accounting for undeliverable surveys, the response rate was 54%.

72% = Percent of hunters and landowners were moderately or very concerned CWD would cause declines in local deer numbers.

72% = Percent of hunters and landowners said CWD should be managed to reduce impact on deer and deer hunting

67% = Percent of hunters and landowners said taking no action was unacceptable.

55% = Percent of hunters and landowners said reducing deer numbers by hunting to slow CWD was acceptable.

Plant native vegetation

​Wildlife have adapted to their natural environments; their bodies go through natural changes to help them survive throughout the changing seasons.

If you still want to feed wildlife, go native! The best things we can do for wildlife is plant native vegetation that provides food and cover. Things to consider planting are mast-producing trees for food, conifer trees for cover, native plants for seed and nectar.

Contact your Game Commission region office for additional information on how to create, preserve, or enhance wildlife habitat.

What is the role of wild birds in the spread of avian influenza?

Migratory birds-typically waterfowl, shorebirds, gulls and terns-are natural carriers of avian influenza and are considered the natural reservoir for low-pathogenic strains of the disease. The impact of highly pathogenic H5N1 on migratory birds and the role that wild birds play in the spread of H5N1 is unclear. In many cases, scientists are uncertain if wild birds were the source of the H5N1 virus or if they acquired it from poultry. Once infected, wild birds could transport the virus to a new location, but infected birds are rarely able to travel far.

Fact: If the highly pathogenic H5N1 is detected in wild birds in the United States it does not necessarily pose a threat to the general public or to the U.S. poultry industry.

Fact: The highly pathogenic H5N1 has been detected in an increasing number of wild bird species; however, the actual number of wild birds infected with H5N1 has been relatively low.

Fact: There currently is no scientific basis for controlling highly pathogenic H5N1 by management of wild birds beyond physically segregating poultry from exposure to wild birds.

Should waterfowl hunters take special precautions?

Hunters should follow routine precautions when handling game.

  • not handle or eat sick game.
  • Wear rubber or disposable latex gloves while handling and cleaning game, wash hands and thoroughly clean knives, equipment and surfaces that come in contact with game.
  • Do not eat, drink or smoke while handling animals.
  • All game and poultry products should be thoroughly cooked (160°F).
Should I be worried about my bird feeder?

Exercise good hygiene when maintaining or filling your bird feeders. The PGC recommends cleaning your feeders periodically with a household soap, rinsing them thoroughly, then following up with a rinse of a solution of nine parts water to one part chlorine bleach and allowing to dry without rinsing.

What should I do if I find a dead bird?

A certain level of mortality in wild birds is normal. Wild bird mortality occurs as a result of trauma, ingestion of pesticides, infections and accidents of nature, most of which pose no threat to the health of domestic animals or people.

Incidents of five or more ill or dead birds (not including pigeons) in the same geographic area over a one- or two-day period may indicate a die-off and should be reported to your PGC region office during regular business hours. Bag and refrigerate (do not freeze) the birds in a cooler with ice until arrangements for pickup or disposal can be made.

Even in cases involving five or more birds, the cause of death can often be determined without laboratory testing. PGC staff may make arrangements to acquire dead birds or recommend disposing of them in a plastic bag in household trash that ends up at a regulated landfill.

The PGC's wild bird mortality investigations are part of a larger operation in cooperation with USDA Wildlife Services. In addition to following up on citizen reports of dead birds, PGC biologists are sampling live Canada geese and mallards statewide, as well as scaup (a species of diving duck), taken by hunters on Lake Erie to test for avian influenza. Water samples also will be taken from areas where waterfowl congregate and tested for avian influenza.