Understanding the Impact of Chronic Wasting Disease on Deer
Chronic wasting disease (CWD) is a transmissible, neurodegenerative disorder in deer that causes inability to eat, stumbling, drooling, and lack of fear of humans, and in all cases is ultimately fatal. According to Michelle Gibison, diagnostic laboratory testing manager at the University of Pennsylvania School of Veterinary Medicine’s Wildlife Futures Program, infected deer can live for two or more years without showing clinical signs of the disease, during which time they can infect other deer.
CWD is a prion disease, meaning it results from a normal cellular protein that has misfolded and then spreads by misfolding additional copies of the protein. There is currently no evidence that CWD can spread to humans, but there is concern that this could change, as other prion diseases — such as Mad Cow Disease — can spread through the consumption of infected meat. CWD cases are increasing not just in Pennsylvania and the United States, but also across the world.
A new collaborative study from Penn Vet and other researchers has shed light on how CWD impacts the gut microbiome and provides a potential tool for disease surveillance. Through collecting and analyzing fecal samples from animals with and without CWD, the researchers found that several types of gut bacteria could differentiate between CWD-positive and -negative animals. Their paper “Prospective fecal microbiomic biomarkers for chronic wasting disease” was published in Microbiology Spectrum.
They analyzed 100 fecal samples from white-tailed deer from different regions of the U.S., of which half have chronic wasting disease and half do not. The study found similar changes in the deer diagnosed with earlier-stage and later-stage CWD, indicating that changes related to CWD precede symptoms. This methodology may prove useful for earlier detection of CWD, especially in areas where CWD spread may not have been previously reported.
Gibison says the Wildlife Futures Program is also unique in having seven wildlife health technicians spread across the state to help with specimen collection and disease surveillance. A next step in Penn’s CWD research is looking at captive and wild deer in Pennsylvania rather than captive deer across the country, which Kashina says is important because it eliminates the variability of geographic regions, which normally has a strong impact on the microbiome. The reasons for the connection between CWD and changes in the fecal microbiome remain uncertain.
One of Kashina’s longer-term hopes is development of fecal testing that hunters can utilize in the field. Catching CWD when it moves to a new area is important, Gibison says. Once the disease becomes endemic, it’s hard to eradicate.
Michelle Gibison is a diagnostic laboratory testing manager at the University of Pennsylvania School of Veterinary Medicine and section head of chronic wasting disease at the Wildlife Futures Program.
Anna Kashina is a professor of biochemistry in the Department of Biomedical Sciences at Penn Vet.
Julie C. Ellis is an adjunct associate professor of pathobiology at Penn Vet and co-director of the Wildlife Futures Program.
Other co-authors are Karie Durynski, Susan Bender, and Lisa Murphy of Penn Vet; Dawei W. Dong of Penn Vet and the Institute for Biomedical Informatics at the Perelman School of Medicine; Adam Didier and Maureen Bourner of MilliporeSigma, Merck KGaA; Guy Kleks and Avihai Zolty of Sigma Aldrich Israel Ltd., Merck KGaA; and Tracy Nichols of the U.S. Department of Agriculture.
The work was supported by the Pennsylvania Department of Agriculture and Pennsylvania Game Commission.