Chronic Wasting Disease still increasing in deer

CODY — Chronic wasting disease continues to evade Wyoming Game and Fish staff. Despite many years of attempts to corral the disease, the number of deer infected with the neurological illness has not waned, but hope may be on the horizon.
“What we’re seeing in some of these areas, where there is heavy overlap with whitetails (deer), where there is a resident population, we are seeing these numbers of chronic wasting disease come up,” Tony Mong, Cody wildlife biologist for G&F, said at a public meeting in January.
When G&F first started tracking CWD around 2000, the disease was mostly limited to the southeast corner of the Big Horn Basin. By 2015 the disease had fully infiltrated the entire Basin with the highest prevalence in eastern Park County. In 2021 there was also a high density for the disease in the South Fork.
“Cody is hot and as you move along the Shoshone (River) it stays hot,” said Eric Maichek, G&F disease biologist for the Cody region.
The stereotypical “zombie deer” infected by CWD, marked by extreme weight loss, fatigue and foaming at the mouth, only make up about 5% of deer with the disease, Maichek said, with the large majority appearing “perfectly normal.” The disease is 100% fatal.
“Always kills them,” Maichek said.
The Clarks Fork region still remains relatively low for CWD cases.
The year 2020 was the highest year for CWD testing on record with around 6,500 samples taken.
“You can’t understand the disease unless you have enough samples,” Maichek said.
Maichek said CWD develops in a “slow and methodical” fashion across the landscape. He said when CWD prevalence rises over 20% in a herd it starts to drag down the population, a phenomenon proven in a few herds in the Big Horn Basin and south Converse County.
G&F has relied most heavily on “targeted removal” of CWD-positive deer to eradicate the disease.
“This has shown to be pretty effective in getting rid of CWD,” Maichek said.
Maichek said a number of studies, including in nearby Colorado and the Black Hills, has shown with the initiation of harvest control measures such as pushing hunting seasons later into the fall and increasing licenses disbursed, CWD can be suppressed.
“They’re giving us some incentive to at least consider it,” he said.
Maichek also said rapid tests can be performed on the ears of deer that may have CWD, and there are certain blood tests starting to show some promise.
“Ultimately it’s got to be long-term and systemic,” he said.
Maichek said CWD will never be completely removed, but with more study it can be better understood and mitigated. For instance, it has been discovered that some deer appear better genetically predisposed to live with it.
G&F has also employed carcass disposal and transport, the process of cleaning and gutting CWD deer and moving them to landfills and across state lines as an effort to prevent spread to places that don’t already have it. Maichek said this takes collaboration with the state and landfills to fund these efforts and separate carcasses from other waste.
The South and North Fork check stations both monitor for the disease as do trail cameras, set up at “pinch points” known to be migration corridors for deer. CWD prion, a type of protein that can trigger normal proteins in the brain to fold abnormally, can be spread through body fluids, direct contact, soil, food, water or mineral licks.
G&F is looking for public input on what it feels could be the best management practices.“We want to hear what you’re seeing out in the field and what you’re feeling about how these populations are doing,” Mong said.
Mong said there have been some outbreaks of “blue tongue” across the state, but CWD is still the most prevalent disease hampering Wyoming deer.

During the public meeting held in January, Tim Berry asked Mong and Maichek whether they would consider increasing the buck harvest season in high CWD areas. Mong said this would be “something to consider,” but current buck levels in the Upper Shoshone – a high CWD area – are at about 32%, an acceptable number.
 
This story was published on Feb. 23, 2022