Wasting disease outbreak would imperil Arizona wildlife, lucrative hunting industry

The glassy eyes appear to stare out as the skull sways back and forth on the operating table. Time in the freezer has suppressed the smell. A smear of blood and brain fluid leads to the hands of Jon Heale, who stabilizes the decapitated head before severing what he’s searching for: the lymph nodes.

He marks the deer head for disposal and seals the extracts for testing. He wants to know if the animal was carrying chronic wasting disease, a contagious brain infection that is fatal and can ravage wild herds of deer and elk.

Heale is a wildlife health biologist for the Arizona Game and Fish Department and he coordinates the collection of thousands of samples each year for a statewide surveillance program. Arizona has yet to record its first case of chronic wasting disease in a local animal, but it borders states that have been dealing with the disease for years.

“Our populations are already at risk because they are under stress from drier and hotter summers,” Heale said. “Anything we can do to keep one more pressure off our deer and elk herds is critical.”

There have been no documented cases of chronic wasting disease transmitting from an animal to a human, but wildlife officials are concerned that the fear of infection may sway hunters to choose grocery stores over the outdoors. That could put a dent in Arizona’s multimillion-dollar hunting industry and cripple state-supported conservation efforts funded by the revenue.

An outbreak in the wild

Chronic wasting disease causes severe brain degeneration, leading to a decline in bodily function in the infected animal and, ultimately, death. It has similarities to mad cow disease, which is scientifically known as bovine spongiform encephalopathy.

“The reason why it’s called chronic wasting disease is because the animal literally wastes away,” Heale said. “Once it enters a population there is no treatment for it. There is no cure. All you can do is manage it.”

Nationally, agencies enforce a range of conservation regulations in response to historic over-hunting.

“Big game, mostly deer, are the foundation of most hunting in America. Originally, it was these large edible animals that were heavily exploited before we made game laws,” said Jim Heffelfinger, a wildlife science coordinator for the game and fish department.

Mule and white-tailed deer are the most common cervid species in Arizona. Since the establishment of hunting regulations, herds have been steadily recovering but rising temperatures and a lack of rainfall pose a persistent challenge to conservation.

The first case of chronic wasting disease was identified in a captive mule deer in Colorado in the late 1960s. The National Wildlife Health Center has recorded cases across three Canadian provinces and 26 states. Three — Colorado, Utah and New Mexico — border Arizona.

Studies in other Western states have shown what a chronic wasting disease outbreak could do to still-recovering wild deer and elk herds.

A research article from PLOS, an online journal, documented an infected white-tailed deer herd in Wyoming for seven years. With an average disease prevalence rate of 35%, results of the study showed infected deer were 4.5 times more likely to die. Overall, researchers recorded a 10% decline in the total population and predicted that within 50 years the herd could be pushed to extinction.

In Colorado, another study published on PLOS examined an infected mule deer herd and found a 45% decline of deer abundance over the course of two decades. The study concluded this “may lead to local imbalances in food webs and nutrient cycles in ecosystems.”

“There’s a perception that an animal gets infected and within days is stumbling around, but the fact of the matter is it’s pretty rare to see deer at the end stages of chronic wasting disease. They don’t last very long,” said Mike Miller, a senior wildlife veterinarian for Colorado Parks and Wildlife, who has been dealing with the disease since 1985.

“The majority of infected deer we pick up here appear perfectly healthy… They are shot by a hunter or hit by a car and they look normal to the casual observer and yet they are infected.”

Fear of human infection

Though there is no confirmed case of chronic wasting disease transmitting from an animal to a human, it is part of a group of prion diseases, some of which have affected humans, said Anne Justice-Allen, a wildlife veterinarian for the game and fish department in Arizona.

Prion diseases can infect both humans and animals and primarily affect prion proteins, which are found most abundantly in the brain. These diseases are distinguished by long incubation periods, can lead to brain damage and are usually fatal.

“We don’t think it’s a direct threat to people,” she said. "But because we don’t know a lot about these diseases there’s a lot of fear.”

The Centers for Disease Control and Prevention has a list of advice for hunters in areas with a high prevalence rate of chronic wasting disease, including testing harvested animals before consuming them.

“Science has shown these prions are evolving. They are conforming in different ways and this leads to different strains. The scary part about strains is that they’ve been shown to have unique host ranges,” said Cory Anderson, a research assistant for the chronic wasting disease program of the Center for Infectious Disease Research and Policy.

“We can’t discount the fact that there could be a strain someday where we see human infection," Anderson said. "This is a dynamic disease, it’s not a static issue. As long as exposure continues to increase, which there is no sign of it slowing, people have to be cautious.”

Crippling conservation

The game and fish department's conservation efforts in Arizona depend on the funding that comes from the state’s multimillion-dollar hunting industry.

With no positive chronic wasting disease cases recorded in Arizona, hunting culture thrives. In 2019, more than half of the department’s revenue came from hunting licenses, tags, firearms and archery equipment.

“If we get chronic wasting disease and people decide not to go hunting anymore, we lose all the income that funds our conservation work,” Heffelfinger said. “Just the thought of the disease crossing the human barrier could get people to say, ‘I’m just going to go to the grocery store.’”

In 2001, fishing and hunting expenses in Arizona generated nearly $960 million for the department. Hunting made up $126.5 million of that sum, a fourth of which came from big game trips. A study calculated the statewide economic impact of that revenue to be $1.34 billion, adding $58.2 million to state tax coffers.

With no positive chronic wasting disease cases recorded in Arizona, hunting culture is thriving. In 2019, the department received nearly 96,000 general deer applications for fewer than 47,000 hunt permit tags.

“For those that grew up hunting in Arizona it is a really important part of their culture, state culture and mental health, especially this year,” Heffelfinger said. “I’d hate to see this disease take away from that.”

Vic Adamowicz, an economist at the University of Alberta, is studying the effect of chronic wasting disease on hunting behavior.

“People are different. Some people have very little tolerance for risks like this, other people don’t feel that this is particularly risky. The hunter population is diverse,” said Adamowicz, who works in one of the three Canadian provinces that have had positive cases.

While Alberta, Canada, has not seen a dramatic change in hunting interest since the first positive case of the disease in 2005, Adamowicz believes "things may change as you see increases in prevalence."

“That’s been the hypothesis particularly in places in the U.S.,” Adamowicz said. “That’s part of the challenge, you can’t do experiments. We are just observing what we see and it’s very hard to understand what’s causing what because we are just observing hunter behavior, license sales, prevalence rates and just trying to understand those patterns.”

Safeguarding by surveilling

Paul Taylor strides across his pitch-black trophy room as the glistening eyes of deer, elk, fish, turkeys, squirrels, rams and a lone buffalo seem to follow his every step. A ceiling lamp illuminates the space, almost every square foot of which is lined with animal mounts.

At the age of six, with a low-gauge shotgun in hand and a few birdshots in his pocket, Taylor began learning about the "connection between hunting and conservation."

Turning an animal’s carcass into a mount is what Taylor calls “the ultimate sign of respect,” because nearly nothing is left to waste. For over 40 years, Taylor has been a licensed taxidermist working in Phoenix, Scottsdale and now San Tan Valley.

He says it's “darn near impossible” to estimate how many animals he has preserved.

For more than half of his career, Taylor has been participating in Heale's chronic wasting disease surveillance program by donating the lymph nodes of his mounts.

“I was born and raised in this state and I’m going to do what I can to protect these animals by collecting these glands,” Taylor said. “If chronic wasting hurts this deer population, any more than the drought and the over-hunting already has, it is going to devastate Arizona’s hunting. Period.”

Taylor’s business is one of over 20 working with the game and fish department's surveillance program, one of the state’s leading safeguards against an outbreak. While the number of samples collected remains steady from year to year, the department has been unable to consistently meet its sample quota from high, medium and low-risk areas.

To reach these quotas next season, Heale, who authored the department’s most recent chronic wasting disease report, plans to partner with more businesses and target high-risk areas.

“Early detection is our best management tool because once it enters a population there is no treatment or cure,” Heale said. “That’s why we’re aiming to ramp up monitoring and keep it out before it gets the chance to even come in.”

Benefits for businesses

Over 23,000 samples have been collected and tested for chronic wasting disease since surveillance in Arizona began in 1998. Most of these samples were “hunter harvested,” meaning they were received through the reimbursement program for meat processors and taxidermists, like Taylor.

“Why not let it benefit the animals? The glands usually go into the dump, they’re wasted,” Taylor said. “I would do this for free just to help them find and get rid of chronic wasting.”

A recent study from PubMed Central conducted in New York found “taxidermists were an untapped source of valuable CWD samples and could be successfully trained with minimal agency effort. Taxidermists were just as capable of collecting the appropriate tissues and following submission instructions for laboratory testing as staff biologists.”

The department pays $10 or $15 for each sample, depending on whether the animal was harvested in or out of state; the latter is worth more.

“When it can be used for scientific purposes and it gives you 10 bucks, why not? It’s an easy 10 bucks,” Taylor said. “It takes seven minutes to cut two-inch glands out. Put it in a packet, write down a little bit of information, throw it into your cool box.”

The same study found “while the cost to have taxidermists collect samples might seem relatively expensive if considered on a per-sample basis, it is likely on par with or cheaper than agency collection if time and costs of sample extraction, transportation, and storage are considered.”

In the over 20 years he has been working with the department, Taylor estimates he’s made back several thousand dollars. In 2019, the department spent around $8,000 in reimbursements to taxidermists.

“These guys are the frontlines of interactions with hunters. They are coming directly to their front door, literally,” Heale said. “Having more of those businesses by our side as we move forward through the next few years and keep sampling is the best way forward.”

The department’s chronic wasting disease reports show that in the last five sampling seasons, meat processors and taxidermists have collected 4,165 samples, making up over 60% of all the samples collected since the 2015-16 season.

But the taxidermists currently participating in the program only make up a small fraction of the nearly 150 taxidermists licensed through the department. By the start of the next sampling season, Heale hopes to bring up the number of businesses to at least 30.

The department uses an online portal to help businesses sign up to participate. The most significant part of the process is an on-site training Heale runs at the taxidermist's place of business.

Taylor called the whole process “easy-peasy.”

“We need buy-in from hunters and taxidermists, alike,” Heale said. “If our deer and elk herds start to diminish, they are going to be impacted in some way or another. Be it through lack of business or the ability to go hunt or just to enjoy wildlife.”

Check stations for hunters

The Jacob Lake Check Station, which the game and fish department believes is the oldest check station in the country, is the other main source of hunter-harvested samples.

The purpose of a check station is to collect data on harvested animals, receive feedback from hunters and assure compliance with state regulations. The check station has been operating on the Kaibab Plateau since 1930, in a high-risk area for chronic wasting disease.

“There is very prominent intermingling of deer that summer in Utah and deer that summer in the Kaibab along the state border. Those two herds intermingle every winter. As a result, it’s an area where it’s likely, if CWD does make it into the state, to occur,” said Todd Buck, a wildlife manager for the department, who has spent nearly three decades at the plateau.

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Though the station has collected nearly 1,500 samples over the last five sampling seasons, the department has only reached its high-risk area quota twice.

The inconsistency is an issue. Buck, along with the rest of the department, hopes to address it this year, especially as chronic wasting disease continues to plague Arizona’s border states.

“Obviously, we set those goals anticipating that we will meet them. But hunter harvest conditions during the hunts all influence the number of deer that are harvested,” Buck said. “Some years we dip below that goal, some years we are above it, but certainly we would like to meet that goal. From a statistical perspective, it will give us some confidence in our sampling result.”

For nearly a decade, the game and fish department has divided Arizona into high, medium and low-risk areas for chronic wasting disease. Over the last five sampling seasons, the quotas for each of these areas have been inconsistently met.

“There’s a lot going on when it comes to those quotas,” Heale said. “Bag limits change, tag amounts change and then there are environmental variables… Those goals are definitely important, and we try to reach those goals, but a lot of it is out of our control.”

Consistent sampling from each risk area allows the department to make informed decisions on its chronic wasting disease protocols. The negative effects of inconsistent sampling on data and risk assessment remain theoretical.

“Those goals are put there so we get enough animals from those high risk, medium risk and low-risk areas to confidently say that we’ve sampled enough of the population,” Heale said. “It’s hard to say if we’re not sampling the high-risk areas intensely enough something could come in that we would never detect.”

What surveillance can’t control are humans, who pose the next most likely cause of an outbreak among the state's deer and elk herds.

With the state’s recovering herds and a multimillion-dollar hunting industry at risk, the Arizona Game and Fish Department established regulations mitigating the most likely ways humans could cause an outbreak.

While the state is enforcing best practices on carcass transportation and baiting tactics, it’s now the less likely, unproven and unregulated human-caused entryways that pose a risk to Arizona’s position as one of the last uninfected western states.

Infectious soil

Chronic wasting disease stems from self-replicating proteins known as prions. They can’t easily be killed by disinfectants, heat or cold, and can even harbor in soil.

When deer and elk have chronic wasting disease "they are shedding infectious agents in their bodily fluid,"  said Bryan Richards, the emerging disease coordinator at the National Wildlife Health Center. That contaminates the soil around them. Once exposed, the tainted soil lingers for long periods of time and can be tracked out by boots and tires.

By binding to both plants and soil, the disease can efficiently infect herds. Research has found soil can serve as a reservoir of infection and cause animals to have more exposure to oral transmission of the disease.

“It is especially harmful to deer and elk because they are very social, communal animals,” Heale said. “They do congregate around watering holes and food plots, making those places perfect for an outbreak.”

While a positive case in a local deer or elk has not been confirmed in Arizona, infected animals have regularly been driven into the state by hunters unaware they were moving infectious material.

The last five chronic wasting disease reports recorded four infected animals being hauled through or to Arizona after being harvested out of state. The positive cases were from deer and elk harvested in Montana, Nebraska, New Mexico and Colorado.

“If you’re moving infectious material, be it soil or a deer carcass, the outcome could be the same,” Richards said. “Anything you can do to implement precautionary measures that reduce the risk of human-assisted introduction of CWD are very valuable protocols to implement.”

Arizona does not currently have protocols consistently advising people hunting out of state how to limit soil movement.

State agencies, including Arizona's, often refer to the Association of Fish and Wildlife Agencies when developing chronic wasting disease management standards.

The association's technical report on best practices advises that when working in an infected area equipment should be cleaned off with detergent, wiped down with a bleach solution and that all field clothing should be carefully enclosed before transportation.

While this advice targets those studying the disease, Richards believes it would be helpful for hunters to do the same.

According to Richards, who helps track and map the disease’s spread throughout the country, the soil and plants in an area with a high prevalence of chronic wasting disease should be considered infectious material. He said the clothes, hunting equipment and undercarriage of a hunter’s vehicle could “easily carry some of that infectious material.” 

Arizona has a higher potential of hunters transporting infected soil across the border because there are free-ranging populations of infected deer and elk in both New Mexico and Utah, Richards said.

“Twenty years ago, you would have probably thought, ‘Man, this guy is crazy.’ But start looking at the data, it’s not that far-fetched because you have all the factors adding up,” Richards said. “In all of these areas… animals have been shedding infectious agents into the environment for decades."

According to Richards, tips on how to limit the movement of infectious material — by hosing down the undercarriages of vehicles, rinsing off boots and storing hunting clothes — should be included in the game and fish department's advice to hunters on the best ways to help keep chronic wasting disease at bay. He said these precautions "would certainly reduce the risk of moving infectious material."

Krysten Schuler, a wildlife disease ecologist at the College of Veterinary Medicine at Cornell University, said most hunters would be willing to clean boots, vehicles and other equipment that has come into direct contact with soil.

“Hunters really pride themselves on conservation. They are worried about the animals and a lot of them out there want to know what they can do personally to help with CWD,” said Schuler, who has spent years studying chronic wasting disease surveillance and response.

With Arizona one of the last uninfected states in the West, Nick Pinizzotto, CEO of the National Deer Association, said addressing any potential threats, no matter how unlikely, is worth it.

“It is much easier to hose the bed of your truck out… then get it and then you have to try to slow the spread,” Pinizzotto said. “There is no aspect of chronic wasting disease anybody will enjoy. But if given the choice, I promise you, as someone who lives in a state with CWD, you would much rather not have it and deal with these inconveniences than the alternative.”

Carcass handling

The CDC advises those hunting in positive areas to test the animal before consuming it.

“Since there is a similar disease, mad cow disease, that has affected people there is some concern it could shift to a new host,” Justice-Allen said. “But to date, we do not have any confirmation that that can happen.”

If chronic wasting disease were to affect people, Justice-Allen said it would be similar to mad cow disease in the way it causes "brain issues."

The CDC also recommends the careful handling of deer and elk killed in areas with a high prevalence of chronic wasting disease. Besides ingestion, hunters are most at risk of being exposed to infectious material when they are field dressing and processing the meat.

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Reports from the Association of Fish and Wildlife Agencies and the Western Association of Fish and Wildlife Agencies are often considered when state agencies are developing chronic wasting disease management plans.

While these technical reports and management recommendations offer some advice on field sampling procedures, they do not advise hunters on how to protect themselves when field dressing or processing meat.

Safe carcass handling recommendations are often found scattered across the internet on hunting blogs and social media platforms. There is currently no central place where Arizona hunters can find suggested protocols.

Pinizzotto, whose organization is commonly a communication link between agencies and hunters, said an effective way to communicate with the public is to keep all relevant advice in a single location, for example on a state agency’s website. That information can then be promoted on social media and hunting regulation documents.

“There is a lot of diversity among hunters and where they are coming from and how they think about things and see the world,” Pinizzotto said. “In some cases, it can’t be a one-size-fits-all message. You have to be willing to do different things and tell your message in different ways.”

The 2020-21 Arizona hunting regulations document already provides advice on ethical hunting, tips on sunrise and sunset times, an explanation of the North American conservation model and even a checklist on how to get started hunting. Pinizzotto says a page of bullet-point tips on proper field dressing and meat processing techniques would be more than appropriate for the document to include.

Schuler says providing recommendations and advice is one of the best ways for state agencies to communicate safety practices to hunters.

“People respond better to the voluntary measures, where they have ownership over the ability to do these things versus someone telling them they have to,” Schuler said. “We want to make sure people know what they can do, and how they can take ownership over their activities.”

Field dressing and meat processing safety recommendations for Hunters

• Wear latex gloves throughout the entire field dressing and meat processing
• Use a dedicated table or location for meat processing. If a table is being used, try to cover it with a plastic sheet that is replaced after every animal to avoid residue attaching from animal to animal
• Use dedicated knives and utensils for field dressing and meat processing, which are used for nothing else
• Avoid cuts to the spinal column, which is where chronic wasting disease has been found to have the most infectivity. If absolutely necessary, for moments like removing the head, use a dedicated knife that does nothing else put cut the spinal column
• Clean all knives and utensils with a disinfectant solution that is half bleach, half water. The equipment should be left to soak in the solution for approximately 10 minutes
• Wear an apron to avoid infectious material staining regularly used apparel

Anton L. Delgado is an environmental reporter for The Arizona Republic/azcentral. Follow his reporting on Twitter at @antonldelgado and tell him about stories at anton.delgado@arizonarepublic.com.

Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.