Experts on Camera

Dr. Krysten Schuler: Chronic wasting disease

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Chronic wasting disease is a degenerative, contagious, always-fatal brain disease affecting deer and related animals that has spread across much of the United States.

On October 10, 2023, SciLine interviewed: Dr. Krysten Schuler, a wildlife disease ecologist at Cornell University. She discussed topics including: how the disease sickens and kills infected deer; how an outbreak can affect a regional deer population; where the disease has been detected in the United States; whether it poses a threat to human health; and what hunters and people who eat deer meat should know about chronic wasting disease.

Declared interests:

Dr. Schuler was previously with the U.S. Geological Survey at the National Wildlife Health Center. She currently volunteers as a science advisor for the National Deer Association and the Teddy Roosevelt Conservation Partnership.

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Introduction

[0:00:19]

KRYSTEN SCHULER: I’m Krysten Schuler. I’m a wildlife disease ecologist, and I study free ranging wildlife, their health, and populations.

Interview with SciLine


What is chronic wasting disease?


[0:00:35]

KRYSTEN SCHULER: Chronic wasting disease (CWD) is a fatal disease of members of the deer family, such as whitetail deer, mule deer, elk, moose, and reindeer. It’s caused by a prion, which is a misfolded protein particle. It is always fatal, and it’s in similar family as other diseases known as transmissible spongiform encephalopathies—mad cow disease in cattle, scrapie in sheep, and Creutzfeldt-Jakob disease in humans.


How does chronic wasting disease affect an infected deer?


[0:01:16]

KRYSTEN SCHULER: Chronic wasting disease—just like its name—causes the animal to become ill over a long period of time. So, over the course of a year or more. And these misfolded protein particles go to the brain, and they accumulate on the surface of the brain cells and cause holes to form in that animal. So, if an animal has holes in its brain, it’s not able to function optimally, which includes finding food. And over the course of months it just wastes away and can no longer function normally.


Does chronic wasting disease pose a threat to human health?


[0:02:01]

KRYSTEN SCHULER: Thus far, there are no known cases of transmission of CWD to humans. The complicating factor with that is that it is in the same family as mad cow disease, which did transfer to humans as variant Creutzfeldt-Jakob disease. So, there’s potential that it would be zoonotic—which means that it can go from an animal to human—but we don’t necessarily have any evidence of that yet. And there haven’t been any indications in areas that have had CWD for a number of decades that there are an increased number of transmissible spongiform diseases in humans in those CWD areas.


Where has chronic wasting disease been detected in the United States?


[0:02:55]

KRYSTEN SCHULER: Thus far in the United States, it’s been detected in 31 different states. But that’s not necessarily the whole entire state. It might be confined to a particular area or county.


How quickly does chronic wasting disease spread through regional deer populations?


[0:03:14]

KRYSTEN SCHULER: Evidence has shown that CWD prevalence increases slowly at first but then more rapidly over time. So, in regions that have chronic wasting disease, certain areas have seen high prevalence values. And if the prevalence becomes too high, and deer are dying, obviously, that can’t sustain a population in the long term.


How do wildlife agencies respond if chronic wasting disease is detected?


[0:03:48]

KRYSTEN SCHULER: The first detection of CWD in a new area means that the wildlife management agency has to implement new rules to try to contain the outbreak. So, often, that has implications for hunters that they’re not able to move their kill out of a determined disease management area. It can also affect the public as far as what actions need to be taken where there’s more presence around certain areas where people need to have their deer checked more often, or if you hit a deer that you need to have it reported. And so, it’s really an intensive operation for wildlife management agencies if CWD is detected.


How do wildlife agencies manage incipient chronic wasting disease outbreaks?


[0:04:49]

KRYSTEN SCHULER: Management of CWD is very difficult, and we have the best opportunity to manage the disease at the first detection before it really gets going. So, the best options for management are right at that initial detection. And that includes having new regulations about movement of carcasses, potentially the use of deer urine as a lure, and oftentimes, it also comes with trying to reduce the local deer density. Because with CWD, you need to stop that transmission, which at the beginning of an outbreak occurs from deer to deer. And so, getting the host—the deer—off the landscape can effectively stop that disease.


What should hunters and people who eat deer meat know about chronic wasting disease?


[0:05:49]

KRYSTEN SCHULER: Ideally, they would know that chronic wasting disease is fatal, and that the prions that cause it are very durable, meaning they can last in the environment for a long time. So, it’s important for hunters if they’re hunting in a known CWD area, to get their animal tested, and to dispose of any remains, any of the carcass that they don’t want to use in the trash, because there are certain parts of the deer that can harbor prions. And so, leaving those parts out on the landscape can then maintain the prions on the landscape. I think it’s important for anybody who eats venison to know that normal cooking temperatures do not inactivate the prion. It’s, like I said, it’s very durable. It’s very hardy. And so, you need really high temperatures and harsh chemicals to actually denature that prion protein.


How can individuals slow the spread of chronic wasting disease?

 


[0:06:57]

KRYSTEN SCHULER: On its own, CWD moves very slowly in a deer population. But we have to think about what our actions are, as hunters, and as the public. Because if we’re moving deer parts, or anything contaminated with prions, down the highway, we’re moving the disease a lot faster. So, for hunters—maybe going to a new area or a different state—it’s really important for them not only to read the regulations of the state they’re going to, but also what’s allowed to be imported back to their state of residence so that they can follow all the regulations and maintain good biosecurity to protect their own deer herd in their home state.


Do you have advice for reporters covering chronic wasting disease?


[Posted October 10, 2023 | Download video]