A STUDY of the spread of chronic wasting disease (CWD) among white-tailed deer in Virginia, West Virginia, Maryland and Pennsylvania found that infected deer tend to cluster in low-lying open and developed areas.
These results suggest that state wildlife management agencies should concentrate surveillance efforts in such topography and landscapes, according to researchers with The Pennsylvania State University's College of Agricultural Sciences.
The study yielded important insights into how CWD has progressed in the East, said David Walter, Penn State adjunct assistant professor of wildlife ecology. Subsequent modeling based on the research has revealed likely paths of future dispersal of the disease, which always is fatal to cervids such as deer, elk and moose.
"We are looking at what environmental variables might be associated with the presence or absence of CWD in the Northeast," explained Walter, who is an assistant leader of the Pennsylvania Cooperative Fish & Wildlife Research Unit.
"We obtained the geographic coordinates of hunter-killed deer that tested positive for CWD and overlaid them on a map showing a variety of habitat and landscape features," he said. "The analysis showed a high prevalence of CWD in deer sampled from low-lying open and developed landscapes."
This knowledge — generated by thesis work done by graduate student Tyler Evans, who is advised by Walter — became more important this spring when the Maryland Department of Natural Resources, Pennsylvania Game Commission and Pennsylvania Department of Agriculture announced that tests had revealed the discovery of three more CWD-positive deer.
Pennsylvania has found seven CWD-positive deer in the last two years. Maryland and Virginia have had a few each, but West Virginia has found more than 100 CWD-positive deer during the last decade.
CWD, which infects the brain and nervous system of cervids, belongs to a group of diseases known as transmissible spongiform encephalopathies, or prion diseases. It eventually produces enough damage to the brain of affected animals to result in death. While CWD is similar to bovine spongiform encephalopathy in cattle and scrapie in sheep, there is no known relationship between them.
CWD in the East first was documented in free-ranging deer in West Virginia concurrently with captive deer in New York in 2005. In the West, it first was recognized in 1967 in captive mule deer in a northern Colorado facility.
Considering the disease's prevalence in low-lying areas, Evans has modeled how it is likely to spread in free-ranging deer, in valleys parallel to mountains and along river bottoms, most likely through developed and agricultural terrain.