PA Deer Farmers Hopeful Fatal Brain Disease Can Be Bred Out Of Herds

Dec 28, 2016

Whitetail deer graze near Zelionople, Penn. on October 17, 2009.
Credit Keith Srakocic / AP

Pennsylvania’s deer and elk farmers are optimistic about new research into chronic wasting disease. 

Chronic wasting disease, or CWD, is a form of prion disease. 

Prion diseases affect many species of animals, including humans, and cause holes to form in the outer layer of the brain. CWD is the prion disease specific to deer and elk and does not affect other species. It is always fatal and symptoms include difficulty moving, weight loss, anti-social behavior and tremors.

“It’s like a slow festering disease,” said Glenn Dice, who tends to about 250 deer at his farm in Franklin County.

The new research looks at genetic susceptibility to CWD and could eventually lead to the disease being bred out of the state’s animals altogether.

The fact that CWD advances slowly and that not all deer and elk exhibit the same symptoms upon contracting the disease makes it hard to identify in live animals. Existing tests for the disease can only be administered after an animal dies.

And if one animal in a herd is shown to have the disease, the entire herd has to be quarantined and euthanized to prevent its spread.

“If even one of them tests positive then you’re put out of business. You lose your farm, you lose your herd,” said Dice. “That’s what’s scary about the disease and why the deer farmers have been doing their very best to self-fund as much of the research as we can.”

Dice said academic researchers are now showing interested in identifying the genetic markers that make certain deer and elk susceptible to the CWD.

According Nick Haley, professor of veterinary medicine at Midwestern University in Glendale, Ariz., similar work has already been done with scrapie, the prion disease that affects sheep and goats.

“About 10 to 15 years ago they identified some very simple genetic components that make sheep resistant to scrapie, and in a matter of years they were able to breed entire herds of sheep that were resistant to the disease,” Haley said.  “Since that started … the incidence of scrapie in places like the UK, the U.S. and Europe has gone down 90 percent or more.”

Haley said they are beginning to do the same thing with CWD, but that it’s a bit more complicated than scrapie in terms of the genetic markers that denote susceptibility or resistance.

Dice said eliminating scrapie from sheep and goat herds was a “long, expensive road” and did not have an estimation of when similar advances might be made in deer and elk populations.

Farmers in Pennsylvania are required to test for the disease annually. According to, CWD was found on an Adams County farm in 2012 and on two Jefferson County farms in 2014. It is also known to be active among wild deer populations in Somerset, Bedford, Blair, Fulton, Huntington, Jefferson, Clearfield, York and Adams counties.

Pennsylvania is the nation’s second largest deer farming state, second only to Texas, with more than 1,000 deer farms across the commonwealth. According to a 2007 report from Texas A&M University, deer farms employed 21,000 people nationwide and added nearly $1.3 billion to the economy.

UPDATED: This story was updated on Dec. 28, 2016 to clarify that CWD does not affect humans.