Published since 1946
CWD Found West of the Continental Divide in Montana
Chronic Wasting Disease (CWD) has been confirmed for the first time in a free-ranging herd west of the Continental Divide in Montana. The first case was a female white-tailed deer Montana Fish, Wildlife and Parks (FWP) officers killed in the town of Libby, MT after a resident reported seeing an emaciated, sick-looking doe. When tests in late May confirmed the deer was CWD positive, FWP initiated the response called for in the state’s CWD Management Plan. FWP established an Incident Command Team led by Region 1 Supervisor Jim Williams; defined an Initial Response Area (IRA) within a 10-mile radius of the location where the deer was found; began collecting additional deer within the IRA; began sampling road-killed deer, elk, and moose in surrounding areas; and launched an outreach campaign to keep the public informed and request observations of deer that appear abnormal.
As of July 3, FWP had submitted samples from 23 white-tailed and five mule deer to the Veterinary Diagnostic Lab at Colorado State University in Fort Collins. Of those, a white-tailed buck was confirmed positive. Three additional white-tailed deer from the Libby area, including a road-killed buck and two does collected by FWP, are suspected to have been infected with CWD. These suspected cases are currently undergoing a second test to confirm the results. CWD was not detected in 18 of the samples and results for six others were still pending as of July 8.
It is unknown whether the high deer density within the Libby city limits is a factor in the prevalence of CWD in this population. Comparing results of testing in the Libby area with those from the Northern Montana and Southern Montana CWD Management Zones where deer densities are lower may provide some insights. FWP and the Montana Fish and Wildlife Commission will make decisions this summer regarding any changes to hunting regulations for the area surrounding Libby this fall.
Montana FWP began low-level surveillance for CWD in 1998, but did not detect the disease in wild cervids until 2017. The first confirmed case was a hunter-killed mule deer harvested in south-central Montana in 2017. In response to that detection, FWP increased surveillance in 2018 in the area where the initial positive deer was taken, as well as additional hunting districts adjacent to Wyoming and Canada where CWD was known to occur. FWP also increased sampling in hunting districts surrounding the location of a former elk farm near Phillipsburg, MT where CWD had been detected in the late 1990s. The elk farm was depopulated and ceased operation after CWD was detected.
In 2018, FWP analyzed samples from 1,367 mule deer, 458 white-tailed deer, 105 elk and 9 moose. Results identified 26 additional CWD-positive animals, including 21 cases in both white-tailed and mule deer scattered across north-central and northeastern counties bordering Canada and five cases in both species within the CWD-positive area south of Billings, in southcentral MT. CWD was not detected near Phillipsburg, but low sample sizes precluded FWP from saying CWD is not yet present in that area.
The Montana Fish and Wildlife Commission adopted regulations in 2006 prohibiting the importation of whole carcasses, whole heads, brains or spinal columns of deer, elk or moose from states or Canadian provinces where CWD was known to occur. Nevertheless, FWP anticipated eventually finding CWD in deer in northcentral, northeastern and southcentral Montana, given the pre-existing prevalence of the disease in Alberta, Saskatchewan, and Wyoming. When CWD was found in Montana in 2017 and 2018, the Commission added restrictions on transportation of harvested animals out of the Northern and Southern Montana CWD Management Zones.
The discovery of CWD in deer west of the Continental Divide in an area far removed from Phillipsburg was unexpected. FWP plans to collect a random sample of up to 200 deer within the IRA in the coming months to estimate prevalence in this population and will increase sampling from hunter-killed animals in Region 1 hunting districts this fall. FWP Regional Communication and Education Program Manager Dillon Tabish reported that FWP is working on defining the geographic scope of a new CWD Management Area around Libby, as called for in the CWD Management Plan. Once established, the restrictions on transporting whole carcasses, whole heads, brains and spinal columns will be applied to that area.
Additional background information and updates on future findings in the Libby area is available on the FWP CWD website.