Scientists Say Wolves May Hold Key to CWD Spread Across U.S.

by Jennifer Shea

Wolves may be the key to slowing the spread of chronic wasting disease in the U.S., some scientists say. And the disease is spreading fast, including to the gates of Yellowstone National Park. But wildlife officials question their solution.

Scientists Look At the Predator Cleansing Effect

CWD is a highly contagious neurodegenerative disease that affects deer, elk, reindeer, sika deer and moose. Its symptoms include weight loss, listlessness, stumbling and neurological problems. The disease can spread through direct contact or through contact with objects touched by CWD-infected animals. It is 100% fatal and to date, there are no treatments or vaccines for it.

The disease has spread to at least 23 states. And there is some concern, thanks to experiments on monkeys, that the disease may one day spread to humans through contaminated meat.

Now scientists are embarking on a research project in Yellowstone National Park to find out if wolves can stop the spread of CWD. The project looks at the predator cleansing effect, or the dynamic whereby predators like wolves keep a herd healthy by preying on the sickest animals in it. 

Early results are promising, the New York Times reports. They suggest that wolves, by culling sick animals, can delay outbreaks of CWD and can limit outbreak size.

The Study’s Problematic Assumptions

Princeton’s Andrew P. Dobson, a professor of ecology and epidemiology, said he believes that CWD grew out of an ecosystem deprived of predators and scavengers. He thinks a healthier wolf population would lead to ecosystems with fewer diseases.

But Montana Fish, Wildlife and Parks Department wildlife division chief Ken McDonald questioned that assumption. He pointed out that animals spread the disease for years before they show any outward signs of it.

“Wolves help remove sick animals, but animals don’t get visibly ill for about two years,” he said. “So they are carriers and spreaders but don’t get the classic symptoms.”

McDonald added that the number of wolves that would be necessary to control CWD would be unacceptable to humans, particularly to ranchers, farmers and hunters.

His solution? Raise the number of deer that hunters can kill in areas where CWD is prevalent.

Still, Penn State doctoral student Ellen Brandell, who is leading the Yellowstone research project, argues that tool is not “effective.” Rather than look for a vaccine, she advocates increasing the number of predators. So for now, she’s counting on Yellowstone’s 10 packs of wolves to keep CWD at bay.