It’s official. Montana has joined 23 other states and provinces with wild cervid populations infected with chronic wasting disease (CWD). Ironically, the two infected mule deer were killed by hunters south of Billings, near Wyoming, within days of Montana Fish Wildlife and Parks’ release of its draft CWD management plan. FWP has proactively moved to limit the emerging threat, and rightfully so.
An infectious, neurodegenerative disease caused by abnormal proteins, called prions, CWD affects white-tailed and mule deer, elk, moose, and caribou. It’s virtually always fatal. CWD first emerged in northeast Colorado and southeast Wyoming about 1980. It percolated along without much fanfare until the late 1990s when it began popping up elsewhere both in game farms and wild herds. At most new locations, its geographic distribution in the wild has expanded; and disease prevalence has trended upward.
This is a disease to be taken dead seriously. It’s unlike periodic outbreaks of botulism or blue tongue that quickly kill ducks or deer and then burn out. CWD persists; it’s relentless. Contributing to its persistence is the indestructibility of prions in the environment. Prions shed in saliva, urine, feces, and infected animal carcasses bind to soil and may be taken up by plants. There, prions remain infectious to cervids for years, perhaps decades. Infected animals survive for months or even years, all the while shedding prions. As more sick animals shed the pathogen, the cycle perpetuates.
In some Colorado and Wyoming deer herds infected longest, CWD infects 20–50 percent of the animals. Wyoming officials who’ve played down CWD’s threat to game herds, have recorded annual declines of 10 percent and 21 percent in whitetail and mule deer herds, respectively. Some modelling efforts suggest that herd extinctions may occur in time.
There’s no way to “treat” the disease and no vaccine prevents it. Instead, proactive intervention is the best bet to stem CWD’s impacts. Like other density-dependent diseases, CWD proliferates where animals congregate. Montana can reduce the disease risk by implementing strategies that limit cervid numbers to state population objectives.
CWD has now spread across neighboring Wyoming to all but Uinta and Teton Counties, the latter home to the National Elk Refuge where I worked the final 22 years of a career that spanned CWD’s march across Wyoming. CWD is knocking at the door of 8,000 elk that winter on the refuge and 16,000 more at 22 state-operated elk feed grounds. A looming nightmare.
Dan Vermillion, chairman of the Montana Fish and Wildlife Commission, recently noted, “To me, the arrival of CWD is terrifying and it’s heartbreaking the more I learn about the science and the potential it has to harm our game herds, which have contributed to the state’s reputation. ... Common sense, in the face of a disease event, points to getting rid of the (Wyoming elk) feed grounds.” In a resolution unanimously passed earlier this year, Montana’s Senate called upon Wyoming to do just that. But I’m not hopeful.
For 20 years I and other scientists and conservationists have warned that feeding elk is a worst-case scenario for CWD. Feed grounds increasingly accumulating prions from infected elk could become veritable biological SuperFund sites leading to migrating elk spreading CWD from these 23 feed ground hubs to Idaho, Yellowstone National Park and beyond.
What should Montana do to protect its treasured wildlife? Disease surveillance followed by inaction, as in Wyoming, is not an option. Montana has two choices. The window for both won’t stay open long:
1. Try to rid the disease along our border.
2. Contain and limit CWD prevalence, as the Montana CWD plan prescribes.
Both options require controversial management actions, public cooperation, a sustained commitment and funding. Neither option is guaranteed success. Both deserve debate. But accepting some level of cervid infection means that the longer CWD is here, the more animals will become infected and likely spread this deadly disease across the landscape. That’s CWD’s lesson from the past 40 years.
CWD’s worst impacts will develop over years. But decisions made now will affect our ecosystems, economy, and Montanans’ way of life far into the future. Talk to others who are knowledgeable. Read up on the issue. Comments on our state’s CWD plan are due by Dec. 8.