Many in the state’s deer farmers are optimistic that a new genomic evaluation test that determines and individual animal’s susceptibility to chronic wasting disease could save the captive cervid industry.
And an official with the Pennsylvania Deer Farmers Association believes the test could also benefit deer in the wild.
According to Josh Newton, president of the association, genetic testing for CWD susceptibility can allow deer farmers to breed away from the disease in the future. By removing those animals identified as susceptible to the disease, he said, the likelihood of CWD occurring would decrease significantly.
Newton believes a similar approach can be taken with Pennsylvania’s wild deer.
“I’m a deer farmer and a hunter,” he said. “If CWD is as serious as touted, this is something that needs to be looked at for wild deer.”
The test was developed by Dr. Christopher Seabury of Texas A&M and is currently available for commercial application. The Deer Farmers Association recently allotted $50,000 for its members to have their animals tested, and samples can be taken from antlers, hair follicles, semen or an ear punch. The test can be done on a live animal and euthanization isn’t required.
According to USDA trials, Seabury’s test can identify animals highly susceptible to the disease with greater than 80% accuracy.
It has been called “groundbreaking” by USDA’s Animal and Plant Health Inspection Service and is supported by the Pennsylvania Department of Agriculture.
While Newton is convinced the test will enable deer farmers to “breed away” from CWD, he believes the same approach can be conducted in the wild.
“It would just take longer to replicate what’s being done in a farm environment,” Newton said. “Genetic analysis can be done in Wildlife Management Units on hunter harvested deer, and specific regions with high CWD susceptibility can be identified and appropriate management models implemented.”
But the Pennsylvania Game Commission isn’t convinced that genetic testing is a feasible practice for wild deer.
While the test identifies highly susceptible deer, it also determines animals that are less susceptible to CWD. That’s not necessarily an advantage, according to Andrea Korman, the PGC’s chronic wasting disease biologist.
Animals with genotypes that are less susceptible to CWD are relatively rare, she said, and they may require higher prion doses to become infected. Once that happens, Korman added, those animals have a slower progression of the disease, and they may shed CWD prions for a longer period of time.
“Decreased susceptibility also does not equal immunity; such cervids can still get infected and will die from the disease,” Korman said. “And given the rarity of this genotype suggest that it may not be advantageous to a deer’s overall survival beyond CWD.”
In Bedford, Blair, Huntingdon, Franklin, and Fulton counties, she said, certain populations of deer have a significantly higher frequency of the more susceptible genotype compared to deer surveyed in New Jersey, Wisconsin, Wyoming, and Canada.
But managing those free-ranging populations for a specific genotype is impossible, Korman said. There are different strains of CWD which carry varying rates of disease progression following infection and dose dependence for infection. And even though selection may occur over time, Korman said, it would also have to overcome dispersal and migration rates from unique populations with potentially different disease and genetic dynamics.
“Free-ranging deer are not livestock and cannot be manipulated as such,” she said.
But Newton said the current approach of attempting to drastically reduce deer numbers in areas where CWD is established may not be the best approach. By removing a higher number of animals, he said, a vacuum is created and other deer will move in.
“Without knowing the genetics of those animals, you’re probably filtering in animals with the same genetics as the ones you removed,” Newton said.
A potentially more effective option – one that could be determined by genetic testing – is to translocate deer from areas where CWD isn’t prevalent to fill the void where animals have been removed, according to Newton.
“For example, if we can determine the northeast part of the state has animals with low susceptibility to CWD, and we know the disease is in deer in the southcentral, you can do translocations,” Newton said. “The science has been done on this and CWD is a highly heritable disease. Dr. Seabury established that, now let’s find the areas of the genome that are susceptible.
“The PGC can do this from samples out of submissions from hunter harvested animals. It’s that easy and it’s certainly something that isn’t unproven.”
- This article originally appeared in PA outdoor News.
