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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

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.

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.  


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. 

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. 


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.