CWD Creeps into Montana

Chronic Wasting Disease infects members of the deer family, including elk and moose

By Rob Breeding

Chronic Wasting Disease has arrived. It was a sad but inevitable development. Knowing what we now know about the disease and the way it spread across Wyoming, it was a near certainty CWD would eventually make it to Montana.

Two buck mule deer, both killed in hunt units along the Wyoming border south of Bridger, have tested positive for the disease. Both were killed this hunting season.

CWD was first detected in the southeastern corner of Wyoming in 1985. It took about 30 years for the disease to spread across the state. About a decade ago, infected deer started showing up on the Wyoming side of the Big Horn River Basin. In 2015, the first cases of CWD in the Cody area were confirmed, and that’s about 50 miles south of Belfry, where the second CWD-infected Montana deer was killed.

CWD infects members of the deer family, including elk and moose. The disease is slow acting, and infected animals can live for years, but eventually the reason for the disease’s name becomes apparent. Animals become emaciated, their ears droop, they salivate excessively and begin wandering in circles, as if they’ve been infected with a land-born version of whirling disease.

Then they die.

The evidence isn’t conclusive yet, but studies suggest deer and elk die from CWD at rates so fast that natural reproduction can’t keep up. In 2002, researchers in Wyoming captured 39 healthy elk calves in the National Elk Refuge near Jackson Hole. Then they transferred the animals to enclosures in Wheatland, near where CWD was first detected in Wyoming. The calves had been healthy, but 38 eventually died from CWD they likely picked up from the infected ground. Prions, the proteins that cause CWD, survive in soils long after they’ve been deposited by infected animals.

Some of those elk lived long enough to reach sexual maturity and give birth, but not enough to outrace the increased mortality from the disease. And mule deer numbers in that corner of the state are in decline, suggesting the disease is taking its toll.

So far there’s no evidence that CWD can jump the species barrier and infect humans who eat diseased deer, but a similar prion-based disease did make that leap. The Mad Cow epidemic in the 1990s in Great Britain nearly collapsed that country’s livestock industry, and more than 200 people in England and Western Europe have died from the human variant, Creutzfeldt-Jakob disease.

For now, it’s recommended that all deer killed in CWD-infected hunt units be tested before the meat is consumed. That process is relatively simple and involves sampling lymph nodes in the animal’s neck. Some hunt check stations in the hot zone of CWD’s spread can collect the appropriate tissue samples, but if you live outside that area and want to have your big game checked, there are kits that allow you to mail in samples. Fish, Wildlife and Parks has instructions on its Web site.

Fear of the spread of CWD has led some on the Montana side of the border to call on Wyoming to close the elk feeding grounds in the Jackson Hole region. The disease hasn’t yet been detected there, in elk at least. It may be too late to stop CWD, however, since it can take years for the disease to be confirmed. The disease may already be in the feeding grounds.

The diagonal spread of CWD across Wyoming took 30 years. If it travels across Montana at the same rate, it will make it to Kalispell by around 2050. Maybe CWD research will be more fruitful in the next three decades. The alternative isn’t too pretty.

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