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Deer dilemma

Hunters asked to help TWRA prevent the spread of chronic wasting disease
Story by: Glen Liford 4/25/2019

Tennessee Wildlife Resources Agency (TWRA) officials have announced new management measures to help prevent the spread of chronic wasting disease (CWD) in Tennessee’s wild deer and elk population.

CWD is a devastating prion disease affecting cervids, the deer family, including elk, moose, and caribou. The disease belongs to a group called transmissible spongiform encephalopathies (TSE), that includes such disorders as mad cow disease or bovine spongiform encephalopathy (BSE); scrapie in sheep; and Creutzfeldt-Jakob disease (CJD) in humans. CWD is progressive and always fatal. The disease does not appear to be transmissible to non-cervids, like cattle and sheep.

The TWRA move comes in response to news late last year that the first cases of the dreaded disease were detected in deer in West Tennessee.

“We had 10 deer harvested in Hardeman and Fayette counties test positive for CWD,” says Chuck Yoest, TWRA CWD coordinator. “As a result of those samples, TWRA increased its monitoring efforts and as of March 1, 2019, 186 deer in those counties and neighboring Madison County were identified. Chester, Haywood, McNairy, Shelby, and Tipton counties were designated high-risk areas as well, as some of the infected deer were harvested 10 miles or less from their borders.  TWRA started CWD surveillance in 2002.” 

CWD was first identified in captive mule deer in a Colorado research facility in 1967. Before being discovered in Tennessee, it was already threatening wild deer populations in 25 states, three Canadian provinces, and Norway, Finland, and South Korea.

These prion diseases are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response, according to the Center for Disease Control (CDC).

“Prions are misfolded proteins that act as an infections agent,” explains Dr. Dan Grove, University of Tennessee Extension wildlife health specialist and wildlife veterinarian. “The prions are found in the brain, spinal cord, and peripheral nerves; in bodily fluids and secretions — saliva, urine, feces, and blood; and in other tissues — muscle, spleen, kidneys, and lymph nodes.”

Testing for the disease is performed on the brain and lymph nodes of suspected animals.

Preventing the spread of the disease is difficult. Infected animals can take months or sometimes even years before the disease manifests itself. Animals infected with the disease may not exhibit symptoms for 12 to 18 months, explains Grove.

“The first sign is a thin appearance and poor hair coat,” he says. “In later stages, animals will drool, stumble, and walk in circles. They may be lying down and urinating and defecating on themselves.”

The prions that cause the affliction can also be transferred to the environment, where animals congregate at feed sites, rubs/scrapes, and mineral licks both natural and artificial, he explains.

“Studies have shown animals can still be infected up to 15 years later where the [area] is contaminated with prions,” says Grove. “Soil types often play a role and sometimes make the contamination worse and more prone to infections.”

Other risks for spreading the disease include the movement of deer and elk, whether natural or human assisted, he says.

“Animals don’t recognize borders as they travel, and the disease can be spread through the relocation of animals in the captive cervid industry or through reintroduction efforts by a wildlife agency,” says Grove.

CWD can also be transmitted by improper disposal of carcasses, including those brought in from other states, stresses Yoest. An infected carcass will have a high level of prions in it.

“If it is deposited in the landscape, those prions will be there a long time and create the potential for exposure,” he explains.

Lures derived from deer urine could also be contaminated with prions from urine, saliva, or feces, and provide the potential to transfer prions to the environment, which could further spread the disease, he says.

It’s still unclear whether eating animals infected with CWD is entirely safe, says Grove.

“Unfortunately, there are conflicting studies,” he says. “Some studies yet to be published indicate there is potential [for transmission to humans], but the reality is there is no documented case of a human being infected with CWD. Researchers are aware of infected deer in Colorado and Wyoming going back to the [19]60s and in some states the prevalence in the deer population is approaching 50 percent. There have been a lot of people eating infected venison [unaware], and there still has not been a documented case in humans.”

Grove stresses that wildlife agencies and professionals are not human health experts. He defers to the CDC on this, and the agency urges caution, he says.

“The CDC strongly recommends having your deer or elk tested before you eat it, if you’re harvesting it in an area known to have CWD,” he says. “And if you’re having an animal commercially processed, ask that your animal be processed individually and not mixed with meat from other animals.”

So what can hunters do to help stop the spread of CWD?

Yoest says TWRA has established guidelines to help contain the spread of the disease. These methods include carcass importation restrictions, wildlife feeding restrictions, and specialized bag limits and season dates that will be determined soon.

“First, please continue hunting and keep hunting traditions alive,” he says, noting that TWRA asks hunters to follow these guidelines:

• Honor carcass import restrictions, if hunting out of state;

• Use synthetic deer and elk lures instead of natural ones.

For those hunting in CWD-positive and high-risk counties:

• Harvest your bag limit and provide deer for sampling;

• Abide by wildlife feeding and carcass exportation restrictions;

• Follow best practices for carcass disposal, including leaving unused parts at harvest location (preferably buried); bagging parts and disposing of them in a landfill; or using a meat processor and allowing them to take care of those parts for you; and

• Report sick or abnormal acting deer and elk to TWRA.

There are several options for CWD testing. These include CWD sampling drop-off locations, participating processors and taxidermists, and staffed check stations as advertised. For information on the sampling locations and to learn of the results of those tests, see www.CWDinTennessee.com.

“It will take cooperation and coordination on behalf of hunters and TWRA to best manage CWD,” says Yoest. “It will require a long-term, sustained effort with results not to be realized for quite some time. But with your help, we will best manage chronic wasting disease.”

Visit these websites to learn more about CWD:

TWRA— www.CWDinTennessee.com

National Wildlife Health Center — www.usgs.gov

Centers for Disease Control — www.cdc.gov

USDA — www.aphis.usda.gov



 
 
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