Back to Stories
Public Health Official: Chronic Wasting Disease Seems Bound To Infect People
March 6, 2019
Public Health Official: Chronic Wasting Disease Seems Bound To Infect People
"CWD is gonna be a helluva wildlife problem even if disease doesn't reach livestock and humans," Osterholm says. He criticizes Wyoming for continuing to operate controversial elk feedgrounds
EDITOR'S NOTE: This story is part of an ongoing series called "Those Who Faced A Challenge And Did The Right Thing," with research underwritten in part through a grant by The Cinnabar Foundation.
Elk concentrated around artificial food at the National Elk Refuge in Jackson Hole, Wyoming which disease experts say is a CWD disaster waiting to happen. Photo courtesy Thomas D. Mangelsen (mangelsen.com)
As a deadly cousin to Mad Cow, Chronic Wasting Disease has now reached wildlife populations and game farms in at least 26 US states. The question, whose loom seems to assume greater prominence every day, relates to this: Is CWD a threat to human health?
Early in February 2019, Dr. Michael Osterholm, an eminent infectious disease expert, made headlines nationwide when he went before the Minnesota legislature and offered this grave observation:
“It is my best professional judgment based on my public health experience and the risk of [Mad Cow Disease] transmission to humans in the 1980s and 1990s and my extensive review and evaluation of laboratory research studies … that it is probable that human cases associated with the consumption of contaminated meat will be documented in the years ahead. It is possible that number of human cases will be substantial and will not be isolated events.”
To date, in spite of suspicions raised by those who have lost loved ones, there have been no documented cases of people coming down with CWD after eating meat from members of the deer family afflicted with the always-fatal malady linked to misshapen proteins called prions.
However, considering the rapid spread of CWD in wild white-tailed and mule deer herds, and disease outbreaks documented among privately-owned captive cervids, ever-increasing numbers of CWD-infected animals raises the odds of genetic mutations occurring with prions. That, Dr. Osterholm says, could make the disease possibly more conducive to crossing species barriers to both humans and livestock.
White-tailed deer are prolific. Millions of Americans eat white-tailed venison each year. Rising levels of disease prevalence, Osterholm suggests, translates into more points of contact between infected animals and humans via the butchering of game meat, consuming it, and infected wildlife coming in contact with bovine livestock. The connotations for hunters in the West, taking mule deer and elk, are identical, he adds.
Millions of Americans eat white-tailed venison each year. Rising levels of disease prevalence, Osterholm says, translates into more points of contact between infected animals and humans via the butchering of game meat, consuming it, and infected wildlife coming in contact with bovine livestock.
Osterholm is frustrated that there is no coordinated national plan of readiness between federal and state governments that focuses on not only preventing contacts and rapidly diagnosing transmission across species barriers, but more aggressively examining sources for future outbreaks.
This would include the controversial and unprecedented artificial feeding of more than 20,000 elk in the Greater Yellowstone Ecosystem. Here, between the National Elk Refuge and 22 feedgrounds operated by the state of Wyoming, concern has been raised to red alert following the discovery of a CWD-infected mule deer in Grand Teton National Park in autumn 2018, very near to where thousands of wapiti on the Elk Refuge are now clustered around artificial feed.
The absence of a coordinated tri-state strategy for confronting CWD in the Greater Yellowstone Ecosystem continues to anger conservationists and retired public wildlife officials who say there have been warnings about a potential crisis for decades.
Not long ago, Mountain Journal interviewed Dr. Osterholm, who is director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota in Minneapolis-St. Paul.
Author of more than 300 papers and abstracts on infectious diseases, he has won six major research awards from the National Institutes of Health and federal Centers for Disease Control. He has been particularly outspoken and recognized for his concern about a lack of preparedness for a global influenza pandemic that most health experts say is inevitable. In addition, Osterholm is author of several books, including The New York Times bestseller, Living Terrors: What America Needs to Know to Survive the Coming Bioterrorist Catastrophe.
Osterholm left some citizens who heard his testimony before the Minnesota state legislature shocked when he cited an estimate made by the Alliance for Public Wildlife that, already, between 7,000 and 15,000 animals infected with CWD are consumed by humans annually.
CWD first appeared in the US in Colorado in the 1960s and some link its origin to captive deer in a research project that might have come down with the disease after being exposed to domestic sheep infected with scrapie, another prion disease. From there CWD spread to wild deer and elk, expanding slowly at first but in recent years its presence has raced through game animal populations on both sides of the Mississippi River.
In the West, CWD has been on an accelerated march from southeast Wyoming toward Greater Yellowstone, the most iconic and wildlife-rich ecosystem in the Lower 48. Despite widespread condemnation, state wildlife officials, governors and legislators have refused to shutter the practice of artificial feeding.
Dr. Tom Roffe, the former national chief of wildlife health for the U.S. Fish and Wildlife Service (which operates the National Elk Refuge) has been outspoken in his criticism. He has told Mountain Journal that “in the face of a disease threat like CWD the absolute opposite wildlife management strategy you would want to take is to keep the feedgrounds open because they create the ideal unnatural conditions for disease to accelerate.”
Meanwhile, the new incoming director of the Wyoming Game and Fish Department Brian Nesvik continues to present the state position that the feedgrounds will continue to operate because there’s no hard evidence that CWD will cause the problems some contend.
“We’ve had a lot of discussions about where that ought to go down the road, and for a long time the department’s position on that has been that we should look for opportunities to reduce our reliance on supplemental feed where we can,” Nesvik told reporter Mike Koshmrl with the Jackson Hole News & Guide. “But there are three things that have not changed. One is that without feedgrounds there’s still potential to transmit disease to domestic cattle. Number two, without feedgrounds it’s inevitable there’d be damage to private property and stored crops. And number three, there’s a large constituency of folks that want to have hunting opportunity for elk, and eliminating feedgrounds would dramatically reduce that opportunity. Those things are not changing rapidly, and our priorities for why we feed haven’t changed.”
Critics say Wyoming’s continuing denial of CWD’s impact runs against the prevailing opinions of disease and professional wildlife management but that its credibility has already been called into question. Some believe that if CWD harms wildlife populations beloved to hunters, a basis for a lucrative wildlife watching and big game outfitting industry, and one day results in infections of livestock or worse, humans, there could be justification for decision makers being held subject to criminal liability, like the lead-pipe water controversy in Flint, Michigan.
U.S. Sen. John Barrasso, R-Wyo, co-sponsored legislation in 2018 that would designate funding to identify how and why CWD is spreading with the hope that it would result in a coordinated strategy among states. Barrasso is joined by two Democrats—Doug Jones of Alabama and Michael Bennett of Colorado.
“Chronic wasting disease has negatively affected white-tailed and mule deer in Wyoming for decades,” Barrasso said in a statement. “To protect our wildlife populations and our hunters, we need to know more about how this disease is spread and which areas are most at risk. Our bill gives wildlife managers the tools they need to research and identify exactly where chronic wasting disease is most prominent and how we can better prevent it. It’s a critical first step to addressing this debilitating disease and keeping our wildlife herds healthy.”
It follows calls for increased research already made in 2017 by U.S. Sen. Jon Tester of Montana, who was joined by leaders of major sportsman's groups.
"In Montana, hunting is a part of our way of life because it helps provide our families with food, manage our wildlife, and sustain rural economies," Tester said. "It is critically important that we stop the spread of Chronic Wasting Disease before it diminishes our big-game herds and undercuts our outdoor economy."
Notably, the Montana Fish and Wildlife Commission sent a letter to the Wyoming Game and Fish Commission in 2017 forcefully requesting that Wyoming shut down its feed grounds, pointing out that wildlife moves across state lines and that the consequences of questionable wildlife management practices in Wyoming affect her neighbors.
Prion diseases are part of a family of diseases affecting the brain and central nervous system called Transmissible Spongiform Encephalopathies or TSEs. The bovine forms, which include Mad Cow and CWD, are BSEs, short for Bovine Spongiform Encephalopathies.
Some believed that Mad Cow, when identified in the United Kingdom, would never move beyond domestic cattle herds, Osterholm says. It proved not to be true. In people, Creutzfeldt-Jakob disease is a human TSE that is extremely rare. The disease that crossed the species barrier from infected cattle [Mad Cow] to humans is Variant Creutzfeldt-Jakob or vCJD.
“Since 1995, when it was identified, 178 deaths have been attributed to vCJD. It's thought that one in 2,000 people in the UK is a carrier of the disease,” BBC News reported in a story published in October 2018. “But it appears that relatively few who catch the infectious agent that causes the disease then go on to develop symptoms”.
Some 4.4 million cattle, suspected of coming in contact with sick animals or facilities harboring them, were slaughtered. British ag producers for many years afterward suffered economic losses where other nations imposed a ban on exports of cattle and beef.
In a study that appeared in Journal of Wildlife Diseases in 2018, evidence showed cattle resisted CWD both when given oral inoculation and cattle were placed in pens where CWD contamination was known to be present. Among the five authors cited were the late CWD scientist Elizabeth Williams and Terry J. Kreeger who had been a longtime veterinarian with the Wyoming Game and Fish Department.
While scientists noted that domestic cattle are susceptible to CWD-associated prions in an absolute theoretical sense, it was instructive that when domestic cows were exposed to enclosures where 89 infected mule deer and 83 infected elk had been kept over a ten-year period—all of which perished from CWD—no infections happened in cattle.
This is important because many experts believe cattle could function as intermediary vectors by which CWD could mutate into a strain more likely to be transmitted to humans. And it is that possibility that worries Osterholm and others because that’s what happened with Mad Cow in the UK.
Kreeger and others wrote in their journal article: “Of secondary concern, passage of the CWD agent through cattle or other livestock hosts could lead to transformation of cervid-adapted prions to a new prion strain with greater potential infectivity for humans.” They noted that scrapie, a prion disease known to exist in domestic sheep for hundreds of years, had not been linked to human cases, though some suspect that scrapie transmission to cattle could have happened when beef and dairy cows were fed feed comprised of ground up infected sheep.
“The possibility remains that a scrapie strain adapted to cattle after its inadvertent introduction became the BSE prion strain which—unlike the scrapie agent itself— eventually proved infectious to humans,” the Journal of Wildlife Diseases article states. “Whether CWD infection of cattle would present a significant public health issue is unknown, but the potential risk would need to be evaluated. Considered in total, the improbability of cattle becoming naturally infected with CWD suggested by our and other studies should diminish concerns over these secondary transmission risks.”
Osterholm, having been involved with investigation teams in the UK, isn’t so sanguine. In fact, people concerned about CWD reaching wildlife feedgrounds in Wyoming have criticized Kreeger for downplaying the risk of a catastrophic outbreak in elk. Over time, he and some of his research colleagues have acknowledged that CWD could result in the extinction of local mule deer herds carrying a specific genetic makeup and they’ve modeled the potential for that happening in elk.
Dr. Osterholm says the number of unknowns relating to the pathogenesis of CWD—the pathways it takes to infection— should not be a basis for relief but pondered for what coming revelations about the potential communicability of CWD could be. One of those involves a controversial study by Canadian researchers suggesting that macaque primates, whose genetics are similar to humans, came down with CWD after being fed disease-contaminated venison.
Cooking beef until its well done did not kill prions from infected meat. With CWD, experts say it is incredibly difficult to sanitize surfaces and soils that come in contact with infectious material. Another fear surrounds the fact that soils can become contaminated with prions shed by the saliva, urine, feces and decomposing tissues of dead animals carrying CWD. Studies also have shown that prions can be taken up in plants growing from infected soils, thus exposing prions to animals—deer family members and livestock—that have no physical contact with stricken CWD hosts.
Further, with regard to the media, Osterholm rolls his eyes at reporters and that have characterized CWD as “zombie deer disease” in order to generate clicks to their sites. He says the disease is a serious enough menace without having to resort to hyperbole.
Here, then, is Mountain Journal’s conversation with Dr. Osterholm.
MOUNTAIN JOURNAL: What caused you to speak out with such a forceful warning before the Minnesota legislature?
DR. MICHAEL OSTERHOLM: Several things. First of all, it’s one of those things, like so many issues, that I could work 28 hours a day on. I’ve been very involved with influenza outbreaks and other diseases, like Ebola, and traveling 200,000 miles a year for work. CWD should be regarded on the same scale of other diseases we are worried about.
I just became more and more unsettled about this issue. I had been involved with providing professional input in the 1980s on BSE. And at that time had expressed my severe concern about this idea that there was this magical disease barrier existing between species that would keep everything from coming to humans. It was something I thought was naïve and my suspicions were validated. At the time, some said you were just a scare monger, that kind of person who just needlessly upset people. And, of course, the story’s been told since that time. I wasn’t alone and our worries were indeed justified.
MOJO: Speak to the similarities with CWD.
OSTERHOLM: I’ve seen the same thing with CWD and I’ve been extremely concerned about, how again, from an agricultural standpoint, the captive cervid farming groups have so misled and challenged us with what they don’t do to stop this. And, correspondingly, what they are doing with their management practices to spread it. The public should be concerned and paying attention.
MOJO: Your comments before lawmakers in Minnesota were praised by many for saying things on the minds of public health professionals elsewhere, as well as those involved with trying to confront CWD as it spreads throughout wildlife populations.
OSTERHOLM: I actually spoke a year ago at the state veterinary association meeting here in Minnesota, laying this all out and the board of animal health was just sitting there in the audience. They had to hear the truth and I didn’t spare a word. At the time I said this has all the makings of BSE déjà vu all over again. Even if it’s not going to happen, there is nothing to keep us from being expeditious and responsible in saying that, let’s at the very least, just do whatever we can to prevent humans from coming in contact with or being exposed to contaminated venison.
MOJO: Such as?
OSTERHOLM: We ought to aggressively be developing testing methods that can be done on site, reliable, cheap, and effective. Trying to create a barrier there.
The last thing we want to have happen is for hunting as a tradition and a management tool to be reduced. Right now there are 200,000 white-tailed deer a year that are harvested in Minnesota and if we suddenly saw the white-tailed deer hunting experience change, that’s only going to increase the problem on the wildlife side because of the animal population density [i.e. having higher concentrations of animals with CWD coming in closer contact with uninfected animals]. However, we need to face the facts and make sure people are protected by providing the best available knowledge.
MOJO: You have called attention to something that, compared to the other issues, hasn’t generated a lot of media coverage and that is the risk of CWD animals passing through meat processing facilities.
OSTERHOLM: Yes, the second thing I’m very concerned about and it comes from some of my foodborne disease work is and has an overlay with prions, is what the hell happens when you introduce CWD into meat processing environments? If somebody’s deer or elk comes through and it’s contaminated what does that mean for everything else behind it? I’ll tell you: it’s not good because it’s not easy to sterilize and decontaminate places and surfaces that become tainted with BSE prions.
I’ve been involved with several situations in hospitals where someone with Creutzfeldt-Jakob disease was accidentally operated on, had brain surgery, and they didn’t understand what was going on. All of that medical equipment had to be land filled. There was no way we could adequately disinfect it. And now imagine the processing environment. I just finally said enough is enough here. We’ve got to speak out on this thing. I realize I have a voice in Minnesota and to some degree around the country; if I put my name to something I typically think it’s pretty important. I finally spoke out and said this is it.
MOJO: You’ve taken your concern a step further, emphasizing your fear that with potential prion mutation, CWD could cross a species barrier from cervids to domestic livestock and then reach people.
OSTERHOLM: Something that’s been very concerning is the lack of national leadership, whether it be on the wildlife side or on the agricultural side. Clearly, I think we have some serious challenges here with what it means to the bovine world.
Is there going to be potential cross exposure [to cattle] and would that happen? The ag people can’t just back out of the conversation about it potentially reaching livestock and, of course, public health officials need to be paying attention to the human side. Right now there is no effective message coming forward from public health about the importance of this other than “just don’t eat it.” The World Health Organization and CDC advisement to not eat suspected meat is limp compared to what we need. A lot of CWD-infected deer and elk may not look sick.
I’m not telling anybody this [CWD] is going to be a BSE crisis but I am suggesting that it couldbe. Why do we want to experiment with ourselves to find out?
MOJO: Some public health officials and experts involved with wildlife management say CWD is an example of an emerging and expanding disease in which the more they look into this, the more frightening the potential becomes. Your thoughts?
OSTERHOLM: I agree.
MOJO: As CWD continues to spread and its impact deepens in wildlife populations, what are your priorities.
OSTERHOLM: I’m less concerned now about contamination of the environment with regard to CWD reaching people. We’re unclear to what degree the environment outside of concentrated experiments like game pens holds in terms of potential for transmission to other cervids or exposure of prions to humans. It’s right now unclear what the risk is. However, game farms and areas where concentrated animal feeding of wildlife occurs is a different situation from CWD naturally spreading.
I absolutely have no doubt that animal to animal transmission is really important. How much of that is from direct saliva contact is really unclear. I think the human exposure question involves really, for me, the venison and game meat consumption issue. The extent of using your own utensils and knives in butchering deer or elk and bringing it back to the kitchen raises serious questions about contamination. And, in terms of people coming in contact with lymph nodes and other tissue of infected animals, we just don’t know the degree of risk but that doesn’t mean risk doesn’t exist.
MOJO: How does this relate to any insights you’ve gleaned from your earlier work in investigating the deaths of people from Mad Cow?
OSTERHOLM: When you look at BSE in England, we looked at the abattoir (slaughterhouse) workers and those involved with packing, we didn’t see any evidence of increased risk there. Risk had to do instead with consumption. That to me represents at least some hope that just exposure to prions wasn’t a good mechanism, but it means that actual ingestion played a key role. I wouldn’t say that it’s a lock-solid type case that there aren’t dangers for people processing infected animals.
Right now, the best thing we can do for certain is make sure people aren’t eating CWD-infected deer and elk and that becomes problematic as it spreads throughout wildlife and geographically.
MOJO: We know that there are different prion strains and mutations that can occur. Is your concern that it’s only a matter of time?
OSTERHOLM: That’s part of it; actually, it’s all of it. Look at the accelerating number of cases. This is out of control in the wildlife populations. Minnesota has done almost as good a job as anybody. They’ve tried hard. It appears that CWD is coming in from infected wild deer in Wisconsin. We also had a damned case in February in Brainerd where a game farm up there had CWD positive animals. The owner refused to depopulate a year ago and now there’s been a transmission to wild deer near his farm.
"Look at the accelerating number of cases. This is out of control in the wildlife populations. In Iowa County, Wisconsin, almost 40 percent of some wild deer herds are CWD positive which means they are going to die and before they do they’ll expose others. What does that mean? We don’t know but the prospects are frightening." —Minnesota epidemiologist Michael Osterholm
MOJO: What kinds of discussions are you having with wildlife managers?
OSTERHOLM: That’s we’ve got a lot of work to keep it from spreading. In Iowa County, Wisconsin, almost 40 percent of some wild deer herds are CWD positive which means they are going to die and before they do they’ll expose others. What does that mean? We don’t know but the prospects are frightening.A
MOJO: Wildlife health experts view game farms and concentrated feeding of wild animals as sort of seasonal de-facto game farms. When you look at concentrating 15,000 to 20,000 elk around artificial feedlines in winter in Wyoming, with animals that then disperse over hundreds and thousands of square miles to summer breeding and calving grounds, what do you make of that?
OSTERHOLM: Well, the Wyoming example, it seems to me, is an aberration. Feeding wildlife and bunching animals together concerns me greatly. That to me is as close as you’re going to get in a cervid to migratory waterfowl and when disease affects migratory birds it gets moved around quickly. What happens in place A means nothing about what might happen in place B,C,D and E. You can’t predict. . But I will note that white-tailed deer don’t move as much as mule deer and elk.
"Feeding wildlife and bunching animals together concerns me greatly. That to me is as close as you’re going to get in a cervid to migratory waterfowl and when disease affects migratory birds it gets moved around quickly. What happens in place A means nothing about what might happen in place B,C,D and E. You can’t predict." —Osterholm
MOJO: So does it concern you that Wyoming and the National Elk Refuge are feeding and bringing together animals in large concentrations? And so you share the warnings that we in the West are feeding animals in such large concentrations with CWD literally on the doorstep?
OSTERHOLM: Absolutely. It’s setting the table for research into how a CWD pandemic could affect a regional population. We need to be looking at that. Some people say that if we don’t feed them then they are going to die. Well the people who say that to rationalize doing nothing must not know what it means to have CWD taking hold in their wildlife. This is where we have to start having dispassionate conversations and asking what are the factors and to what end?
"Regardless of whether CWD reaches humans, it’s going to be a hell of a wildlife disease problem no matter what. But it could be a lot more than that. We could have a BSE nightmare, an American version of it, all over again." —Osterholm
MOJO: You've voiced a wariness toward those who argue that wildlife managers should just wait to see if there’s a disaster and then respond?
OSTERHOLM: I tend to be a data driven guy. But at the same time, I’m one that knows that pulling the pump handle of the fire alarm sometimes needs to be done before you have all the information you need. When John Snow pulled the pump handle of alarm in Soho in London in the mid 1800s, warning about cholera erupting from untreated water, and poor sanitation, it was a while before it happened. and action was taken. Meantime, a lot of people died.
We’ve got more than enough data to justify taking really significant actions, which nobody’s doing. Part of the problem is discussions about CWD have been siloed, almost as an over-response to make sure there isn’t alarm
MOJO: If we don’t take action, what will happen?
OSTERHOLM: I don’t know. Soon we will, though. Regardless of whether CWD reaches humans, it’s going to be a hell of a wildlife disease problem no matter what. But it could be a lot more than that. We could have a BSE nightmare, an American version of it, all over again. I think it would be a real challenge. The way the numbers are going up should be a concern. If we keep seeing the expansion of CWD in white-tailed deer, the numbers could be astronomical around the country. In North America in general and with elk on top of it. We have to pull ourselves out of the sand and understand there could be a real reckoning coming.
MOJO: In the West, some hunters and hunting guides want to minimize the worry so we don’t inflame hysteria.
OSTERHOLM: All we need is one CWD case in which a human gets sick and dies to how the jig is up, to prove it can happen and then people will go off the deep end. There’s no way you’ll be able to control the hysteria.
MOJO: Anything else you want to emphasize?
OSTERHOLM: I remember reading the pieces that appeared in Mountain Journal. They’ve been among the most comprehensive out there. I think your publication, in elevating the issue, is right on. You understand the reason why we should be concerned and try to get ahead of it instead of being caught by surprise. All we as scientists want to do Is get out facts. I’ve always believed in the wisdom of the precautionary tale.
If the advocates for action were asking for some extreme measures to be taken based on little to no data, then there would be a problem. But we’ve got enough data here to justify what we must do. What we’re asking for is not extreme. People should be aware that consuming meat from a CWD positive animal may put the life and health of you and your family at real jeopardy. How is saying that being anything but responsible?
Please click here to support a publication devoted to protecting the wild country and the wildlife you love.
Read Mountain Journal's unprecedented, widely-distributed and critically-acclaimed series (ongoing) on Chronic Wasting Disease:
Part One: Greater Yellowstone's Coming Plague: With the arrival of Chronic Wasting Disease imminent, is government mismanagement threatening the health of GYE's elk herds and humans?
The Cinnabar Foundation.