Containing the spread of CWD

Containing the Spread

How FWP is working to keep chronic wasting disease—now confirmed in two areas of Montana—from moving elsewhere in the state. By Peggy O’Neill.

This story is featured in Montana Outdoors September-October 2018 issue

This past July, 25 wildlife professionals from seven states gathered in a conference room near the Denver airport. The mood was somber.

“We are a reluctant new member of this group,” John Vore, Game Management Bureau chief for Montana Fish, Wildlife & Parks, told his colleagues.

The statement elicited a few chuckles, but the reason for the group’s gathering was no laughing matter. Just a few months earlier, Montana had become the most recent state to detect chronic wasting disease (CWD), which is now present in 25 states and two Canadian provinces.

CWD is a contagious neurological disease that infects members of the cervid family (deer, elk and moose). Symptoms at its end stages include poor body condition, excessive salivation and drooling, drooping head and ears, disoriented behavior, and decreased sociability.

There is no known cure for CWD, and it is always fatal to infected animals (though there have been no known cases of the disease affecting humans who eat meat from infected animals).

Presence of the disease was first confirmed in Montana last fall when a mule deer shot south of Billings near Bridger tested positive, as did another mule deer shot less than 10 miles from the Canada border north of Chester in Liberty County.

Though dispiriting to Montana hunters and wildlife managers, the discovery of CWD here was no surprise. Emily Almberg, FWP wildlife disease ecologist, says biologists assumed CWD was already in the state and it was just a matter of time before it was detected. Montana is nearly surrounded by states and provinces where the disease has been detected in wild herds: Wyoming, the Dakotas, Saskatchewan, and Alberta.

Given enough time to work its ravages, CWD can seriously reduce populations. Both Colorado and Wyoming have had the disease for decades. Wyoming has estimated a 21 percent annual decline in one heavily infected mule deer herd, and Colorado reports a 45 percent decline in an infected mule deer herd there. Among white-tailed deer, Wyoming saw a 10 percent annual decline in an infected herd and a corresponding decline in older bucks.

Almberg says that once CWD gets into wild deer or elk populations, there’s no way to effectively eradicate it. The only option is to try to keep prevalence low and reduce its spread.

The Wyoming Game and Fish Department organized the regional CWD meeting in Denver and invited game and fish agencies from across the northern Great Plains. Representatives from Montana, Colorado, South Dakota, Utah, Kansas, and Nebraska participated. Among other issues, participants discussed CWD management recommendations developed by the Western Association of Fish and Wildlife Agencies (WAFWA). “The WAFWA recommendations have had a big influence on the states’ and provinces’ renewed commitment to managing CWD and is defining what management will look like,” says Almberg. “This regional coordination is one of the most promising developments in recent years. We’re hoping it will help all of us develop more effective CWD management tools.”

Plans to manage the disease vary among states and often evolve within states. For years, Wyoming chose not to manage CWD because the need did not appear critical. But after seeing CWD prevalence increase and deer numbers in heavily infected herds decline, Wyoming recently decided to actively manage the disease.

CWD was first detected in 1967 in captive deer at a wildlife facility in Colorado and quickly spread to wild herds there. According to Mike Miller, a wildlife veterinarian with Colorado Parks and Wildlife, almost half of that state’s deer herds and one-third of its elk herds are now infected. “This is the biggest thing that’s ever hit wildlife management in Colorado,” he says. Colorado is managing CWD using special hunts and mandatory sampling in specific areas.

With CWD lingering at Montana’s door for so long, FWP had the opportunity to learn from other states and was prepared to act quickly when the disease was detected. “Because we had developed a well-thought-out management plan, we’ve been able to efficiently look for CWD and respond to it when it was found,” Vore says.

CWD map

FWP had identified priority surveillance areas—located near borders of states and provinces with CWD—where biologists monitored for the disease in harvested and road-killed deer and those showing symptoms. That’s how the first infected hunter-harvested deer were discovered last year. Then, in accordance with the state’s plan, FWP quickly established two special hunts last winter where the infected deer were found. By studying the harvested deer, FWP scientists learned how prevalent and geographically widespread CWD was in the affected areas.

Scientists found that 2 percent of mule deer and 1 percent of whitetails in the Bridger area had the disease, and less than 1 percent of the mule deer in the Chester area were infected.

The state’s CWD plan calls for intensely monitoring other priority surveillance areas. “Unfortunately, we don’t have the resources to monitor them all at once,” says Vore.

Instead, FWP will monitor some areas one year then move to other areas the next, rotating over a three-year period. The plan also calls for continuing to collect samples from any animals killed that show CWD symptoms anywhere in the state.

In addition, FWP has established “transport restrictions zones” (TRZs) around areas where the disease was detected. No one may transport the heads or spinal columns of deer, elk, or moose killed in CWD-positive areas out of the TRZs.

Vore says FWP is committed to managing CWD in ways that keep prevalence low and minimize the disease’s spread. That will probably mean increasing harvest, especially of males, in CWD-positive areas. Bucks are typically two to three times more likely to be infected than does and disproportionately contribute to the spread of the disease.

FWP may also reduce large deer or elk groupings by removing or fencing-off attractants such as hay stacks or through hazing or dispersal hunts. The disease spreads more readily when deer and elk congregate.

“Having CWD is now a new normal for Montana,” Vore says. “But with wise and careful management, we, our kids, and our grandkids will be enjoying deer, elk and moose far into the future.”Bear bullet

Peggy O’Neill is chief of the FWP Information and Education Bureau.