Photo courtesy PGC.

Projects to Explore CWD in Pennsylvania

February 9, 2023

HARRISBURG, Pa. – Chronic Wasting Disease (CWD) – an always-fatal and untreatable neurological disease affecting white-tailed deer and elk – continues to expand across Pennsylvania.

But it’s not going unchallenged. Several research initiatives launching this year aim to increase understanding of CWD and develop tools to confront it.

The first project will look at the impact of CWD on deer in Bedford and Fulton counties, which have produced about 90% of known CWD-positive deer since the disease’s discovery in Pennsylvania in 2012.

The Pennsylvania Game Commission, in cooperation with the Cooperative Fish and Wildlife Research Unit at Penn State University and the University of Pennsylvania School of Veterinary Medicine’s (Penn Vet) Wildlife Futures Program, will capture and outfit deer with GPS collars over three years starting this winter. Deer will be monitored to examine their fates.

“Although it is unfortunate that CWD is now found in about one of every five hunter-harvested adult deer in these counties, these circumstances do provide a higher probability of capturing, marking and monitoring individual CWD-infected deer,” said Andrea Korman, the Game Commission’s CWD Section Supervisor. “It will give us insight into the effects of CWD on Pennsylvania’s deer population.”

A second project with the Cooperative Fish and Wildlife Research Unit at Penn State University will use modeling to investigate how CWD may affect future deer populations and what actions can be taken to reduce any negative effects.

Right now, the ultimate impact of CWD on Pennsylvania’s deer herd is unknown. Research from Wyoming has shown that CWD can negatively impact deer populations, but Pennsylvania’s deer abundance and landscape are much different.

“Pennsylvania’s landscape is ideal for white-tailed deer, so it is important for the Game Commission to have Pennsylvania-specific data when recommending CWD management actions,” said David Walter, Assistant Leader of the Pennsylvania Cooperative Fish and Wildlife Research Unit. “This study will provide those needed data.”

Two other research initiatives underway focus on improving CWD detection. Detection of CWD is particularly challenging.

CWD has a long incubation period. Infected animals might not show clinical signs of the disease for up to 18 to 24 months post-infection. In the meantime, they appear normal but continue spreading the disease.

What’s more, there is no approved live-animal test for CWD. Current testing methods can detect it only by examining tissues – such as brainstem and lymph nodes – collected from dead animals.

But the Wildlife Futures Program, a wildlife health partnership between Penn Vet and the Pennsylvania Game Commission, is currently engaged in two projects aimed at improving the Game Commission’s ability to detect CWD.

The first involves using dogs trained to sniff out CWD. Phase one of this initiative, conducted through Penn Vet’s Working Dog Center, validated that dogs can distinguish feces from CWD-infected deer from those of deer that were not infected.

In phase two, the Wildlife Futures Program’s K9 Conservation Team will move dogs into the field to determine their CWD scent detection on the landscape.

The second project involves refining a highly sensitive detection method for prions known as real-time quaking-induced conversion test (RT-QuIC for short) to detect CWD in feces and other tissues. This would expand the Game Commission’s ability to track and monitor CWD.

“The evaluation of dogs’ CWD-detection abilities and new diagnostic tests represent potential additions to the toolbox for managing CWD,” said Lisa Murphy, Co-Director of Penn Vet’s Wildlife Futures Program. “We’re looking forward to assessing the results of these ongoing research programs.”

CWD, classified as a transmissible spongiform encephalopathy (TSE), is similar to scrapie in sheep, bovine spongiform encephalopathy (BSE or “mad cow disease”) in cattle, and Creutzfeldt-Jakob disease (CJD) in humans. It represents a significant threat to deer and elk in Pennsylvania. There is no natural immunity to the disease and there is no cure.

CWD spreads through direct animal-to-animal contact, as well as indirectly through prion-contaminated environments. Prions are misfolded proteins, and evidence supports prions as the infectious agent for CWD. CWD-infected individuals shed prions in saliva, urine and feces, and infected carcasses contribute to environmental contamination. Prions can pass through the digestive tract of scavengers and predators and remain infectious; plants can uptake CWD prions and remain infectious; and soils retain infectious CWD prions for years.

Currently, there is no evidence of CWD infecting humans or other species under natural conditions, but much is still unknown about CWD. Given the uncertainty, limiting exposure of wildlife, livestock and people to CWD prions is essential.

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