Wasting disease testing robust for elk, skimpy for deer

Regional disease biologist Ben Wise extracts lymph nodes from hunter-killed elk heads at a Wyoming Game and Fish Department building. The department has increased its monitoring and testing since November, when a road-killed mule deer in Grand Teton National Park tested positive for chronic wasting disease. (Photo by Ryan Dorgan, Jackson Hole News&Guide)

By Mike Koshmrl

Jackson Hole News&Guide

Via Wyoming News Exchange

JACKSON — Aaron Morehead’s gloved hand skillfully sliced through esophagus, larynx and muscle from under the jaw of a middle-age cow elk shot hours earlier atop Blacktail Butte.

On a gusty December afternoon Morehead’s hand-numbing task was to retrieve two gummy bear-size lymph nodes. The white nodes can be tough to distinguish from the mess of tissue, glands and fat filling the retropharyngeal space under the elk’s lifeless head.

But for Morehead there was no mistaking them. Within moments he had the nodes in hand. As a Wyoming Game and Fish Department chronic wasting disease biologist, he’s done this hundreds of times before.

As the elk’s carcass headed to the processor and then a chest freezer on East Hall Avenue, the lymph nodes — part of the central nervous system and indicators of CWD — would soon be on their way to a Laramie laboratory for testing.

The amount of effort Wyoming wildlife managers put into monitoring the Jackson Elk Herd for chronic wasting disease is unparalleled among elk and deer herds roaming elsewhere in the state. Hundreds upon hundreds of hunter-killed animals from the world’s largest artificially fed elk herd are dissected and tested each fall. So far each has been deemed CWD-free.

Still, the demand for such tests is growing.

“We’re getting samples from everybody,” said Ben Wise, Game and Fish’s regional disease biologist. “The bad part is we’re seeing increased surveillance because we found it. We found chronic wasting disease.”

A mule deer buck, killed by a vehicle and found beside the road in Grand Teton National Park near Kelly, provided the first proof that the lethal, incurable disease has arrived in Teton County. The mid-November detection was anticipated, wildlife experts say, because CWD had been pressing toward Jackson Hole for decades and had been found in deer off to the east and south where the disease was already endemic.

Before this, there had already been a vigorous monitoring effort underway.

In Game and Fish’s Jackson Region, which encompasses Star Valley, as many as 600 lymph node samples from elk and deer will go to the lab in a busy year. The majority typically come out of cow elk shot during late-season hunts in Teton park and on the National Elk Refuge. The park and refuge are also invested in CWD monitoring, and the refuge has even required that successful hunters test their animals.

All the attention is having an effect.

“It takes a ton of samples to detect [CWD] at 1 percent prevalence,” Game and Fish Wildlife Disease Supervisor Hank Edwards said. “With the Jackson Elk Herd we’re there. We collect so many elk heads from that area.”

Game and Fish’s disease biologist, Wise, knows all about it.

During a wintry late-season weekend when elk are on the move, he guesses 60 or 70 cow heads and lymph node samples will pile up in the storage building outside the Game and Fish office on North Cache Street. They get there by way of head drop boxes distributed around the park and refuge, willing hunters in the field and the last-remaining wild game processor in Jackson Hole, Matt’s Custom Meats. In the park and refuge hunts alone through Dec. 3, some 350 heads and samples had cycled through Game and Fish’s monitoring process.

An identifying ear tag secured to a wire adorns each head so the state can discern whose elk is whose and later inform hunters that their meat is safe for consumption. Chronic wasting disease has never before been confirmed in a human, but laboratory tests with monkeys suggests there’s no absolute barrier preventing transmission between ungulates and primates.

It’s CWD’s disastrous potential that’s to blame for the huge investment of resources that goes into monitoring. Although slow-moving across the landscape and through wildlife populations, CWD is capable of collapsing herds, particularly deer herds, after it has infected areas for decades.

Once present, the degenerative neurological disorder transmits from animal to animal through contact, saliva and other bodily fluids. But the misfolded brain proteins that spread CWD, called prions, can also survive in soil, water, vegetation and minerals, enabling transmission through the land itself.

Twice in the past six years Game and Fish has changed its fundamental approach to monitoring for CWD.

Testing was spread out statewide until 2012, when some federal funding dried up that caused Game and Fish to focus resources instead on the outside “leading edge” of where the disease occurred.

That’s still the emphasis, Edwards said, but now biologists and field technicians are also trying to intensively sample nine mule deer herds from areas that have carried the disease for years.

“Our goal is to get good, statistically significant sample sizes in several of our herd units to get a grip on what our prevalence rates are,” Edwards said. “We’ll compare those with Montana, Colorado and several other states to try to figure out if we are already doing some management actions [i.e., hunting seasons] that are limiting chronic wasting disease.”

Overall, he said, the CWD monitoring program is processing as many animals as ever — and it’s only going to increase.

Through Tuesday afternoon Edwards’ Wildlife Health Laboratory had processed 5,391 tests during 2018, a monumental task for the three full-time and two contracted employees who work out of the Laramie facility.

“It is literally all we do,” Edwards said. “It starts the first of October, and we’re still busy into December. I would expect to get almost to 6,000 samples by the end of the year, which is about tied for the record.”

Although sampling of the Jackson Elk Herd is impressively robust, duplicating the effort with mule deer in the region has proven difficult. Most are killed well into the backcountry, and many are quartered and packed out in a way that leaves lymph nodes and other easily tested tissue in the field. Perhaps just a few dozen are rounded up in a hunting season, said Wise, who has spent days in the field in early fall without acquiring a single mule deer CWD sample to show for it.

“We know that deer are what we should be really keyed in on,” Wise said. “They’re the earliest to get it, and they make major movements out of CWD-endemic areas.”

To up that effort Wise is exploring better ways to test road-killed deer, whose locations must be noted for the samples to be meaningful. He is also setting out to train outfitters and hunters in the community in how to extract the retropharyngeal lymph nodes on their own. 

One Jackson Hole wildlife advocate who has paid close attention to CWD management and research commended Wyoming’s efforts to surveil for the disease’s advancements and prevalence rates.

“I think that’s the one area where the state’s done an excellent job,” Jackson native and wildlife filmmaker Shane Moore said. “They’ve had a rigorous program for a long time, and they let hunters know quickly when a new area shows up.”

But Moore is critical of the state’s lack of research looking into CWD’s ecological impacts and into how it’s being spread.

A few days after Morehead plucked the nodes out of the hunter’s Blacktail Butte elk he was in Jackson on Berger Lane rounding up more heads to sample from barrels outside Matt’s Custom Meats. The severed heads filled the bed of his green Game and Fish pickup truck.

“Thirty heads,” Morehead said. “This is my daily routine.”

Before he rolled away, one of the meat processor’s employees stepped outside to see what the commotion was about.

“Hey, buddy, how are you?” Morehead said. “You guys all set on head tags?”