Montana’s
approach to a fatal wildlife infection
By Jessianne Castle EBS ENVIRONMENTAL & OUTDOORS
BOZEMAN – In
mid-October, samples from a mule deer buck on Montana’s Hi-Line were packaged
and shipped to Colorado. There, scientists at Colorado State University
confirmed the news: the deer was infected with a fatal disease that has slowly
cropped up in deer within the Treasure State. Another was confirmed on Nov. 4
in an area northeast of Joliet.
Known as
chronic wasting disease, this infection has been confirmed in approximately 60
deer statewide since it was first found in wild herds in the Treasure State in
2017. It has been found along the Hi-Line mostly north of Highway 2; in
southern Montana south of Billings; within a half-mile of the southeast border
near Decker; and in the northwest near Libby.
CWD, making
its way into newspaper headlines as “zombie deer disease,” is a difficult
problem, one that wildlife disease ecologist Emily Almberg is increasingly
faced with in her role at Montana Fish, Wildlife and Parks.
CWD is a
slow-moving, fatal neurological disease that affects deer, elk and moose,
though it has only been confirmed within Montana in our wild deer herds. It is
caused by a misfolded protein known as a prion, and Almberg says once an animal
is exposed to the prions, they accumulate in the nervous system and cause
normal cellular proteins to misfold. This ultimately leads to tissue
dysfunction and death. In advanced stages, there is so much damage to the brain
that the organ comes to resemble Swiss cheese.
And the
challenge for managers is multifaceted. For one, there is no known noninvasive
method to sample for CWD; tissue samples from the nervous system or lymph nodes
from a dead animal are required for testing. Additionally, CWD-causing prions
are capable of surviving in the soil for what is yet unknown lengths of time
and a sick deer can spread the disease even before the appearance of symptoms.
“If left
unmanaged, CWD will spread,” said FWP Director Martha Williams in a statement.
“As infection rates increase, it can have a significant impact on our
wildlife.”
According to
Almberg, herds heavily affected by CWD can see serious population declines—in
Colorado, mule deer populations have dropped 45 percent over 20 years and in
Wyoming, one herd is experiencing a 21-percent annual decline. Yet perhaps the
most worrisome piece remains that researchers haven’t been able to find a cure.
CWD was
first discovered in 1967 in mule deer at a Colorado research facility. It
quickly showed up in captive mule deer and elk in Ontario, Colorado and
Wyoming, and by the ’90s, it was present in wild deer, elk and moose in
Colorado and Wyoming and in captive herds from Saskatchewan, South Dakota and
Oklahoma, as well as at a game farm in Philipsburg, Montana. At the time, the
infected Philipsburg elk were destroyed and the facility was quarantined.
As of 2017,
CWD was present in wild cervid herds in 25 states, three Canadian provinces,
Norway, Finland and South Korea. It reared its ugly head for the first time in
Montana’s wild populations in October 2017 when a deer harvested south of
Billings tested positive.
“I think
probably CWD has been here for a while and we’re just finding it,” Almberg
said, noting that as a slow-moving disease, it can take a while before it
becomes detectable. Though animals that have reached the terminal stage are
visibly sick—with excessive salivation, emaciation, apparent drowsiness and a
lack of muscle coordination—it can take up to two years before symptoms
develop.
Montana’s management
of CWD continues to evolve as new cases appear. Guided in-part by a citizen
advisory panel, FWP has designated CWD Management Zones where the disease is
known to exist, and is also sampling high-risk areas in order to look for any
new infections.
To prevent
the spread of the disease, transport restriction zones have been set up across
CWD Management Zones. Additionally, hunters can opt to have any deer tested for
CWD and FWP will cover the costs and submit the samples for testing. While the
disease is not thought to be transmissible to humans or domestic animals, the
Centers for Disease Control and Prevention recommend sick animals should not be
consumed.
Almberg said
an important point for hunters to remember is to avoid inadvertently spreading
the disease and that proper disposal is key. Rather than dump body parts or
trimmings in ditches or carcass piles, she said hunters should leave the spinal
column at the kill site and dispose of hides, bones and trimmings at approved
landfills. Not only is it illegal to dump carcasses near roadways, but also if
it is infected with CWD, the carcass can spread the disease for at least two
years.
Visit fwp.mt.gov/cwd for more information.
