Study Shows Some Deer Genetically Resistant to Chronic Wasting Disease

I think it was Kramer from the comedy Seinfeld who said it best: Mother Nature is a mad scientist! Nowhere is this more apparent than when considering how different animals have physical characteristics that may look strange, but that are best suited to their environment. For example, whitetail deer are born with white spots, camouflaging and protecting them from predators.

Scientist Charles Darwin explained Mother Nature’s mad tendencies by natural selection. Harken back to high school biology class, where you probably learned about natural selection (a.k.a., survival of the fittest). Natural selection is the process by which certain species that possess genetic traits best adapted to their environment tend to survive and pass the genetic traits to offspring, while animals without these genetic traits tend to die off.

Chronic wasting disease is a perplexing issue for biologists, state wildlife agencies and hunters. The disease has been discovered in more than two dozen U.S. states and Canadian provinces. (Photo: Warden Micheal Hopper, Kansas Department of Wildlife, Parks & Tourism)

Chronic wasting disease is a perplexing issue for biologists, state wildlife agencies and hunters. The disease has been discovered in more than two dozen U.S. states and Canadian provinces. (Photo: Warden Micheal Hopper, Kansas Department of Wildlife, Parks & Tourism)

It’s important to remember what natural selection is, because it just may hold the key to dealing with chronic wasting disease (CWD). Unless you’ve been living in outer space you know that CWD has been killing deer, elk and moose for decades. Wild whitetails in Wisconsin have been hit particularly hard by the disease, with biologists first identifying it in the wild in 2002. The Wisconsin DNR tried unsuccessfully to eradicate CWD by hiring sharpshooters to eradicate all whitetails in the CWD core area. Hunters knew their efforts were in vain.

“The topography is heavily wooded and hilly, giving deer ample places to hide,” said Anthony Grabski, a biochemist, hunter and landowner in the original core Wisconsin CWD area. “Deer are also very evasive creatures, so it’s impossible to kill all of them.”

Thankfully, long gone are the days of Wisconsin trying to wipe out CWD by wiping out deer herds. Today the Badger State’s management of CWD is limited to monitoring its prevalence and spread. This passive management gives a nod to natural selection, and a recent study supports the approach.

University of Wisconsin-Madison researcher Stacie Robinson and her colleagues looked at tissue samples of harvested deer collected for six years in the core CWD area to identify a set of genes (genotype) that appear to make some whitetails genetically resistant to CWD. Statistical modeling showed that deer with a particular genotype were four times less likely to contract CWD, and if they did become infected, they lived 49 longer (8.2 months) than deer without the genotype.

Robinson and her colleagues estimate that about 41 percent of all deer in the original CWD core area have CWD-resistant genes, which they will pass on to offspring. If natural selection follows its normal progression, deer that are CWD-resistant should become dominant in a few hundred years. That’s good news to hunters like Grabski.

“This evolutionary change could take place in an area with low infection rates in as little as 250 years,” Grabski added. “In an area of high infection, the process will be accelerated, and most deer could be CWD-resistant in as little as 50 years.”

The implications for CWD management are enormous. Those who still advocate harvesting large numbers of deer to try to eradicate CWD and/or for CWD testing will undoubtedly take out CWD-resistant deer from the wild, slowing the process of natural selection. In the end, it’s probably best to leave CWD management to Mother Nature.

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