Chronic wasting disease in North Dakota deer appears on the verge of accelerated growth -- a development expected by state wildlife officials but not necessarily this soon.
Eighteen deer killed by hunters last fall tested positive for the fatal disease that strikes the nervous system in deer and also in elk and moose, according to the state Game and Fish Department.
That brings the total number of deer cases since the initial discovery of the disease in North Dakota in 2009 to 44 -- with 30 of them in just the past two years.
“As we approach that exponential phase, that’s absolutely a cause for concern,” Game and Fish Wildlife Veterinarian Charlie Bahnson said. “Unfortunately, the pattern that’s been observed in other parts of the country, that rate of acceleration starts to increase.”
It's a looming issue in a state where tens of thousands of people hunt deer and the industry contributes tens of millions of dollars to the economy each year. Hunters are key to keeping a handle on it, according to Bahnson.
A developing problem
The disease more commonly known by its acronym CWD has been an issue in other parts of North America for years. It’s been detected in wild deer, elk or moose in 24 states and two Canadian provinces, according to the U.S. Geological Survey’s National Wildlife Health Center.
North Dakota had been somewhat of an island -- surrounded by infected areas but free of the disease -- until 2009, when the first case was confirmed in a deer in the south central part of the state. Since then, 33 more cases have been documented in that hunting unit, 3F2, including 21 in the past two years.
“The disease is kind of clustered rather than scattered,” Bahnson said.
No cases have been found in elk or moose in North Dakota. But cases in deer have been confirmed in four other western units in the past three years, and officials brace for an inevitable spread of the disease across the state. When the growth will reach a point where it begins causing significant declines in the deer population is hard to predict, because it depends on numerous factors including deer density and habitat conditions.
“But we know it is out there -- that theoretical threshold,” Bahnson said. “That’s what’s concerning.”
For now, infection rates are fairly low -- about 5% for mule deer in 3F2, and around 2% for whitetails in that unit and others.
“It’s relatively low to other places in the country, in places where the disease has been for a number of decades,” Bahnson said. “Infection rates of 30-40% are certainly not unheard of. I think it kind of reflects that it’s somewhat early in the course of the disease” in North Dakota.
The state of Wyoming has a much more extensive history with CWD, with the disease first identified in the wild in 1985. Infection rates in 2019 in targeted deer units ranged from 5.2% to 57.1%, according to data from that state's Game and Fish Department.
Density maps provided by the agency show that 20 years after CWD was first documented in Wyoming, it was still concentrated in the southeastern part of that state, where it was initially discovered. It's been only in the last 15 years that the disease has spread throughout much of the rest of the state.
A noticeable increase
Given the experience of states with more CWD experience, the 69% jump in cases in North Dakota after last fall's surveillance tabulation is noteworthy.
“I think in a perfect world, we maybe thought we would be seeing this kind of increase many years down the road,” Bahnson said. He noted the large number of cases in 3F2 and said “it’s not unexpected, but we had hoped that it would be years and years before we reached that increase.”
The reason it happened last year is hard to pinpoint, he said, but “I think it probably reflects the disease is pretty well-established down there, so there’s enough (infected) individuals that are affecting other deer, to where we’ve just basically reached this point.”
Officials last year also documented the first CWD case in unit 3A2, in the northern part of the state bordering Canada and to the east of 3A1, where six cases have been documented in the past three years.
Most of the deer cases in North Dakota have been in hunter-killed animals. There has been only one documented case of a natural deer death due to the disease -- a whitetail found dead and emaciated by a landowner near Williston in February 2019.
However, “We very much assume that there’s quite a few deer that die out there; the carcasses are just never found,” Bahnson said.
As infection rates climb, such discoveries will become more commonplace, he said. And in 3F2, they're already climbing -- from 3.1% in mule deer in 2019 to 5.1% last year. Because Game and Fish tracks the infection rate, the agency knows "unequivocally" that higher surveillance participation by hunters isn't a reason for the increase in cases, according to Bahnson.
Impact on industry
Deer hunting is a hobby and tradition for many in North Dakota, and it’s also a multimillion-dollar industry. State tourism data show that each resident deer hunter spends about seven days in the field, spending on average about $136 each day. Nonresident hunters average about five days afield and spend $226 daily.
The impact of increasing CWD prevalence on the industry is hard to know. A study by Purdue University researchers in 2019 concluded that an outbreak in Wisconsin cost that state $17 million in license sales between 2002 and 2015.
License demand in North Dakota remains strong -- more than 81,000 people applied for a deer gun lottery license last year, when 69,050 licenses were available.
The number of licenses issued last year in 3F2 -- where 34 CWD cases have been documented through the years -- were 35% higher than they were in 2008, before the first case, according to Game and Fish data.
Still, when the agency has to inform a hunter that his or her deer was positive for CWD, “it’s really kind of erodes the overall hunting experience,” Bahnson said.
Hunters also have to decide whether to eat the meat. No CWD infections have been reported in people, but the World Health Organization and the U.S. Centers for Disease Control and Prevention recommend hunters not consume meat from infected animals.
Jeremy Doan, a hunting guide in the Burleigh County region, said the disease hasn’t impacted his area yet, but some out-of-state clients ask about it, and overall “it’s a huge concern.”
“If it did hit our area, it would definitely change everything,” he said. "Maybe the river will head it off."
Heading it off
Game and Fish has imposed measures in recent years to slow the spread of the disease, with violations carrying a $200 fine.
Baiting bans are in place in infected units and some neighboring units, to prevent deer from congregating and spreading the disease, which passes from animal to animal.
The movements of certain deer parts is restricted from CWD units in the state and from about two dozen other states where chronic wasting is present, including South Dakota, Montana and Minnesota; three Canadian provinces including Saskatchewan; and four overseas countries.
The state also has a surveillance program that collects deer heads voluntarily from hunters for testing. About 7% of hunters took part this year in targeted units, according to Game and Fish.
“Absolutely our best tool to manage the disease is the hunter,” Bahnson said.
Participation was higher than last year but still lower than Game and Fish would like, according to the wildlife vet. In 3F2, where participation rates are around 10%, “that at least lets us track infection rates,” he said. “In others, where it’s only 3-4%, that doesn’t really give us a confident picture.”
Bahnson stressed that units with CWD still have good hunting opportunities.
“We hope (hunters) will take advantage,” he said. “We also really need them, to help us keep this disease in check.”
For more information, go to https://gf.nd.gov/wildlife/diseases/cwd/faq.
Reach Blake Nicholson at 701-250-8266 or firstname.lastname@example.org.