Chronic wasting disease caused a 10 percent annual decline in the white-tailed deer population south of Glenrock, according to University of Wyoming researchers.
Their study, presented in a paper published Aug. 30 in the scientific journal PLOS One, is the first to look at population effects of white-tailed deer herds with a high level of CWD prevalence.
University of Wyoming graduate student Dave Edmunds said the findings are notable because there is no effective management for infected herds. The findings increase the urgency of keeping CWD from spreading.
“The take-home is: Prevent CWD from getting into new populations, because once it gets established we really have no way of handling the disease,” Edmunds said.
The study said localized extinction among infected herds could occur within 50 years. The disease also affects elk, moose and other kinds of deer.
While CWD is not known to have a negative effect on humans or livestock, Edmunds said white-tailed deer are one of the most popular animals with the public, both for hunting and nature watching.
“We care about population decline because this is the most commonly hunted big game species in North America,” Edmunds said. “There is a large segment of the population that want to hunt and just view — non-consumptive users ... just like to observe white-tailed deer.”
The disease has existed in Wyoming and northern Colorado for 50 years but has steadily grown over time and is now spreading to states like Wisconsin, Michigan and New York and even central Canada.
It is undetectable for roughly the first 18 months after an animal is infected. During that time, Edmunds said saliva and feces from infected deer can spread it across the herd’s habitat.
“The landscape becomes radioactive,” Edmunds said. “That’s what makes it such a nasty and difficult disease to manage.”
In the final stage of the disease, deer become emaciated and effectively starve to death. Edmunds said there is no cure and even infected deer cared for in captivity will eventually succumb.
The study examined deer in southeastern Wyoming from 2003-2010. Edmunds said the 10 percent annual population decline was due largely to a high infection rate among female deer who are responsible for increasing herd size.
“It doesn’t take very many bucks to impregnate all the does,” Edmunds said. “Females are really what drive population growth.”
Female deer in the studied population were infected with CWD at a rate of 42 percent, compared with 29 percent in males.
Edmunds said new hunting regulations, such as restrictions on killing does, might help ensure white-tailed deer populations remain stable. The research found CWD-infected deer are more likely to be killed by hunters even when no visible symptoms were present.
“Hunting is exacerbating the problem,” he said.
But a Wyoming Game and Fish official said that statewide the white-tailed deer population was doing fine.
“Saying CWD is affecting the white-tailed deer population is probably over-exaggerating,” said Scott Edberg, deputy chief of the Wildlife Division.
He said white-tailed deer are thriving in certain parts of the state, such as the Black Hills region.
But Edberg emphasized that for several years the state has had strict regulations of moving live animals and on exporting corpses of hunted animals out of the state — two main ways CWD is thought to be artificially spread.
“We have very strict regulations… specifically to address CWD,” Edberg said.
Edberg said he had not yet carefully reviewed the new research but that Game and Fish, which helped fund and support the study, would incorporate the results into its decision-making process about hunting regulations.
The study was conducted through the Wyoming Wildlife/Livestock Health Center under the supervision of Todd Cornish, an associate professor at the university-affiliated State Veterinary Lab.