CWD study completed

Tom Hobbs and his posse of Colorado State University graduate students have been riding the Livermore range for five years, rustling up deer and hauling them to a line camp, but instead of riding horses and using lassos, they’ve used helicopters to drop nets. At the line camp, the deer were probed and sampled by veterinarians and medical researchers, branded with a radio collar, and released back into the wild. They rounded up 539 animals, all in the name of understanding chronic wasting disease.

Hobbs has now completed a five-year study into the nature of chronic wasting disease (CWD), funded by a $2.5 million grant from the National Science Foundation, which he named The Laramie Foothills Mule Deer Project. He delivered a summary of the findings in his sixth annual gathering of concerned citizens at the Livermore Community Hall in early November.

His research was propelled by the sense of alarm raised when CWD was first discovered at a CSU holding pen some 40 years ago, and by the crude and unpopular culling program instituted by Colorado wildlife officials that resulted in the wholesale slaughter of buck deer in an attempt to halt the spread of the disease. Hobbs does not fault them, saying the program “was logically based on the best science they had at the time.”

At the time, early forecast models predicted the disease would decimate deer populations in the West, and some insinuated that the disease was somehow caused by CSU researchers. Now the science is much improved, says Hobbs. He reports that CWD is a prion disease, similar to scrapie in sheep, or to “mad cow disease.” It is spread through urine, feces and saliva and is thus present throughout the environment. It may have been present locally long before it was discovered.

Oddly, high concentrations of clay in soils may both preserve and amplify the causal agent. Two of the four areas studied, Big Hole and Red Mountain, were found to contain higher clay soils, while Campbell Valley and Lone Pine did not. The data showed that the population in these two was declining, but the statistics for the latter two did not support the conclusion that the presence of CWD would necessarily lead to a decline in the deer population. They found only one infected animal west of U.S. 287.

In sum, said Hobbs, if CWD is present, the herd faces a 75 percent chance of a declining population. If it is not present, the population only has a 45 percent chance of decline. Other findings included the fact that the further an animal ventured away from its winter range, the less likely it was to become infected.

Genetics also played a factor. Mutations to a prion-precursor gene may make an animal more or less likely to become infected. Overall, the odds of becoming infected were about 4 percent per year. A deer who lived longer than eight years was not likely to become infected. In total, about 8 percent of the female deer studied were infected, but there was much local variation. Male deer are three to four times as likely to be infected. The disease cannot be identified visually. A sick-looking deer is not necessarily infected.

One audience question was directed to Nathan Galloway, a research biologist and a hunter: “Would you eat a CWD infected deer?”

“No. I’d feed it to my dog,” Galloway said. He pointed out that canines are not susceptible to prion infections, but people are. Moose and elk are also potential victims, but mountain lions and coyotes are not. Researchers at Rocky Mountain National Park are currently studying indications of CWD in elk.

Further information can be found at: http://www.nrel.colostate.edu/projects/modelingCWD/ and an interesting video of the line camp activity can be found at https://www.youtube.com/watch?v=-Ho1Ur3omaU