May 5, 2002 The Denver Post by Theo SteinOne of the enduring mysteries about chronic wasting disease is where it came from.
Thirty-five years after it was first identified as a transmissible spongiform encephalopathy, researchers say they may never know. But there are two main theories.
CWD may have arisen on its own. The infectious protein thought to cause the disease is natural, and a sporadic mutation may have taken hold somewhere in northeastern Colorado or southern Wyoming 40 years ago. But why here and nowhere else?
Of all the transmissible spongiform encephalopathies, CWD is most similar to sheep scrapie, which was known to infect flocks along the foothills of Colorado and Wyoming. Perhaps, researchers speculate, scrapie jumped to deer somewhere in that area. But scrapie has been widely distributed throughout the country, so why here and nowhere else?
Researchers believe that feeding cattle scrapie-infected sheep bits caused mad cow disease. Some speculate that deer involved in a nutritional study at a Colorado State University research station in Fort Collins - where CWD was first recognized in 1967 - were either fed rendered sheep or lived on scrapie-contaminated ground.
But so far, no one has found records of scrapie at the station, which has been owned since 1977 by the Colorado Division of Wildlife. And the research protocol didn't involve feeding protein supplements to sheep.
In addition, the endemic area extends all the way to Casper, but just a little ways south of Fort Collins. So if it did start in Colorado, why would it move so far north and not spread south to Denver?
Despite the lack of evidence, the theory that the wildlife agency was responsible for the spread of CWD is accepted as a bedrock truth among many elk ranchers.