Dogs may be key in detecting CWD infection

The trick to detecting chronic wasting disease in cervids might be right under our noses—or more accurately, dogs’ noses.

Chronic wasting disease—CWD in its short form—has become an increasingly troubling issue for those managing both wild and captive cervid populations, but trained dogs may be the key to noninvasive detection of the disease.

As of July 2024, 32 states in the U.S. and five Canadian provinces have reported cases of chronic wasting disease in ungulates. CWD, which is caused by an abnormally folded protein called a prion, is highly transmissible. The disease, which is becoming more prevalent, is fatal to white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), elk (Cervus canadensis), and moose (Alces alces), among other cervids.

One challenge to managing CWD is that scientists either have to test for it in cervids after they have died, or they have to sedate them to gather tissue samples, which is quite invasive.

But in a recent study published in PLOS ONE, researchers found that using dogs may be a way to get around some of these challenges. The scent-savvy pooches can use their noses to discriminate between CWD-infected deer and ones without the disease.

While the term “working dogs” may conjure images of Belgian Malinois and Labrador retrievers, the six dogs trained in this study were various breeds rescued from shelters, including a coonhound named Moose that had destroyed his previous owner’s living room.

“You have to look for a dog that will do the same thing over and over again without getting bored, and they all need a high drive to work,” said Glen Golden, a study author and research scientist and behaviorist at Colorado State University. “They were all really good dogs.”

Golden and his team first had to familiarize the dogs with the scent of a CWD infection. They exposed the dogs to fecal samples—the metabolic result of the disease—rather than the actual pathogen. The samples were from both wild and captive white-tailed deer.

“Five test boxes were arranged on elevated surfaces, one of which contained a CWD-positive fecal sample,” Golden said. “Once the dog detected the positive sample’s odor, it would sit, alerting the handler to the positive box. The handler would then push a clicker and give the dog a treat or toy, depending upon what it was most motivated by.”

Golden said that after the dogs learned to find the CWD-positive samples, the researchers began adding negative samples around the positive one. The dogs were able to detect the positive result approximately 90% of the time.

“From there, we kept changing the position of the positive sample,” he said.

The researchers rotated the samples often so that dogs did not become too familiar with an individual deer’s smell.

“We’re asking them to generalize everything they’ve learned previously and forcing them to focus on infection status as opposed to any other smells,” he said.

After the dogs were able to confidently identify an infection through fecal samples, researchers began testing the dogs’ detection ability with gastrointestinal tract tissue samples from previously unseen—or, unsniffed—positive deer, in comparison to unseen negative samples.

Because the overall body smell of a CWD-infected deer should be similar to the fecal sample smell, dogs were still able to differentiate between an infected individual and a noninfected individual 81% of the time, even when presented with sections of the GI tract that don’t contain any fecal material.

A dog’s ability to detect an infection in this manner, especially with fecal samples, could prove to be a powerful and money-saving tool for those managing captive herds, Golden said. But, he added, the study has raised more questions about how the dogs could be best utilized to detect CWD in free-ranging herds.

He said that perhaps the best place to employ working dogs is at CWD hunter check stations, similar to the way the Transportation Safety Administration uses dogs at airports. But he would be interested in finding out if dogs could detect a CWD infection in areas where deer historically congregate, like around deer corn feeders, for example. This could give natural resources managers and wildlife agencies a valuable head start in disease surveillance and containment.