The confirmation of always-lethal chronic wasting disease among the ranks of the Jackson Elk Herd is spurring discussions about how to best detect its presence as it spreads through the natural environment.
The vector of CWD is called a prion, which is a misfolded brain protein known for its near indestructibility and knack for persisting in the natural environment, including in soil and water. Since just a single elk to date has tested positive for CWD, it’s likely that prions have been deposited locally only at trace levels — so far. Nevertheless, National Elk Refuge biologist Eric Cole is one person on the hunt for some type of test or monitoring system to track its spread as more elk and deer become infected and prions accumulate on the landscape.
“The biggest issue is commercial assays for environmental prion detection are not available,” Cole told the News&Guide. “Everything has happened in the academic realm.”
Testing of dead animal tissue — lymph nodes are most commonly used — is commonplace. But surveillance of the environment presents a newer frontier.
Cole has been in talks with the U.S. Geological Survey and is eager to connect with a researcher who can conduct some type of testing ahead of a commercial test becoming available. In the meantime he’s banking soil from different parts of the refuge so that there’s the option of determining CWD’s spatial extent in the present and, as the years tick by, sometime down the road.
“Our focus is on soil right now, not water, but both surface and groundwater will likely also be a research route that we’re going to go in the future,” Cole said. “That’s all in the preliminary stages.”
Research on Colorado’s Front Range has found evidence that trace levels of prions can turn up in surface water, specifically the Cache la Poudre River outside Fort Collins.
“It may initially seem highly unlikely that an infectious protein could be detected in a small sample of the sixty billion liters of water flowing through the South Platte River Basin at the time it was collected,” a 2009 study published in the journal Prion says. “However, given the extreme sensitivity that [serial protein misfolding cyclic amplification] affords, a very small amount of [prion] contaminant can be detected.”
That study speculated that the prions from brains and body matter from deer and elk killed by CWD could be a cause of the contamination. But even live animals could also be shedding prions, the authors pointed out.
“Deer and elk defecate approximately 900,000 kilograms of feces and urinate approximately 14 million liters of urine in the area immediately surrounding the Cacha la Poudre per year,” the study said. “Although urine and feces likely contain much lower prion loads than blood or saliva, the sheer amount of excreta may contribute significantly to overall environmental contamination.”
Chronic wasting disease has never been documented crossing over to a human, but laboratory research with macaque monkeys that consumed infected meat has found there’s also no absolute barrier preventing transmission from cervids and primates.
Based on the Colorado research, it’s likely that CWD prions will someday be detectable in Flat Creek, which drains out of the National Elk Refuge, home for 8,000 or so concentrated elk each winter.
“The big question is, ‘How likely are prions to enter groundwater?’” Cole said. “I don’t have the answer.”
But that question is intriguing enough that town of Jackson Public Works Director Floren Poliseo is also exploring options for testing the municipal water supply. Town wells located on the refuge provide tap water for East Jackson, she said.
“We’ll definitely look into it,” Poliseo said. “I’m interested in figuring out what’s feasible and putting some costs to it so that we can budget for it in the future.”
The town’s water supply has a couple of factors going for it that could help keep CWD prions out. The wells are generally located uphill from the elk feeding areas, Poliseo said, so there’s no concern of surface runoff coming from the congregations of animals toward the well locations and then draining.
“Then in terms of the groundwater, our wells go pretty deep into an aquifer that’s separated from the surface by sandstone layers,” she said.
Prions would also need to navigate the soil before reaching the water supply, Teton Conservation District water resource specialist Carlin Girard said.
“Soil is pretty reactive when it comes to prions, and they do kind of bind to soil particles,” Girard said. “That makes them a little less mobile.”
But at the same time, he said, the soil types in this region are among the most porous that exist. They’re notoriously bad for filtering out contaminants.
“It lets a lot of stuff through,” Girard said. “I don’t want to assume much. Testing is always good.”