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October 18, 2019

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Nevada fighting uphill battle to keep ‘zombie deer’ from entering state

Deer Chronic Wasting

Scott Takushi / Pioneer Press / AP

Biologist Mike Zeckmeister removes the lymph nodes from one of three deer in a hunter’s pickup truck in order to test them for chronic wasting disease, at a checkpoint in Shell Lake, Wis., Nov. 17, 2012.

“Zombie deer.” It sounds like a bad B-movie, something that airs on the SyFy channel late at night. They’re real, though — sort of — and Nevada wildlife regulators are working to keep them out of the state.

The term is one picked up by popular media for animals who have contracted chronic wasting disease, an incredibly contagious, terminal disease that can decimate populations of deer and elk. The disease causes zombie-like symptoms, such as lack of fear of humans, lethargy and emaciation.

Peregrine Wolff, a wildlife veterinarian with the state’s Department of Wildlife, said the department was working to keep the disease out of Nevada by, among other things, testing dead animals and keeping a close eye on the state’s border with Utah and the migratory elk and deer populations there. Nevada legislators also passed a law earlier this year to keep parts of certain carcasses out of the state in an attempt to stop the disease’s spread.

The disease has hit numerous states around the country, including Kansas, Colo­­rado and Wyoming. It’s crept into the eastern portion of Utah, the closest it has gotten to Nevada.

The disease is neither viral nor bacterial. Instead, it is transmitted by prions — protein particles that have been linked to numerous brain diseases across species, including mad cow disease in cattle and Creutzfeldt–Jakob disease in humans.

Diseases caused by prions cause damage to brain tissue, and are incurable. When an animal contracts chronic wasting disease, it creates lesions in the brain, leading to abnormal behavior. Humans are not thought to be able to get the disease, according to the federal Centers for Disease Control and Prevention, but some research has raised concern that chronic wasting disease “may pose a risk” to humans.

The minimum time between exposure and the first symptoms is thought to be 16 months, according to a study posted to the Center for Food Security and Public Health. The study says the average incubation period is 2-4 years. Some studies have shown that animals are contagious before symptoms start.

This long gestation period has also raised issues around determining the disease’s threat to humans, according to the CDC.

One of the problems, Wolff said, is that once the disease is found in a population, it’s almost certain that there is more than one infected animal.

That’s because, besides the disease’s highly contagious nature, it can remain in the environment for years.

For example, a study from a Public Library of Science journal shows that prions can stay in the soil and remain for years with limited degradation. A 2004 study published in the Center for Disease Control’s Emerging Infectious Diseases journal showed that two captive mule deer populations were infected with the diseases in separate paddocks — both of which had not had any infected animals inside them for around two years.

One of the issues in Nevada, Wolff said, is that infectable populations are differently distributed than in other states. “We’re trying to find it in a smaller population but also a more spread out population,” she said.

The disease’s contagious nature led to the passage of a bill in the 2019 legislative session banning the bringing certain animal body parts in from out of state, including the brain and the spinal cord, which contain large concentrations of the prions.

These body parts can introduce the disease into places they are disposed of. Tyler Turnipseed, the chief game warden for the state’s Department of Wildlife, summarized a possible scenario in testimony about the bill.

“Someone, for instance … shoots a deer in Colorado that is infected with chronic wasting disease. They’re back home to California, (and) realize they will be in violation of California's law (banning certain carcass parts), so they stop and dump out their butchered carcass alongside the freeway,” Turnipseed said. “They’ve taken their meat, they’re legal on that part, but they leave the spine or part of the head. A raven comes along, or the deer that migrate down off the Sonoma Range to the Humboldt River, and comes into contact with this carcass, and all of a sudden we’ve got chronic wasting disease (in Nevada).”

Wolff gave another example — if while processing deer carcasses, a taxidermist creates a pile of discarded tissue, which could cause a buildup of prions in the area.

“This is all in an effort to decrease risk,” she said. “We know that we can’t wrap Nevada in a bubble.”

Looking forward, though, Wolff and others are a bit fatalistic, though that hasn’t stopped them from fighting the disease’s spread. She doesn’t see the spread of the disease stopping cold at the Nevada border.

“It’s not a matter of if, it’s a matter of when,” Wolff said. J.J. Goicoechea, a state veterinarian with the state Department of Agriculture, said the same when discussing the bill passed by the legislature earlier this year.

“In talking with Utah and talking with Idaho, high likelihood, with time. In watching the patterns as they progress through Colorado into Wyoming, Nebraska, Kansas, up into Montana now, it’s spreading. And it is going to spread into Nevada,” he said. “We want to do everything we can. I don’t want it to be because of something we did not do, that we did not try to firewall that.”