Miles Blumhardt, Fort Collins Coloradoan Published 8:00 a.m. MT Aug. 23, 2018 | Updated 9:48 a.m. MT Aug. 23, 2018
Mike Miller, Colorado Parks and Wildlife’s Wildlife Health Program Leader, feeds an elk at agency’s Wildlife Research Center on the CSU Foothills Campus on July 18, 2018.(Photo: Miles Blumhardt/Fort Collins Coloradoan)Buy Photo
“Watch your step for rattlesnakes,” Mike Miller cautions as he unlocks a squeaky gate that leads to a fenced field of dried, knee-high grass on the western outskirts of Fort Collins. “We usually don’t let anyone in here anymore.”
Here, on Colorado State University’s Foothills Campus sits a dilapidated animal pen that appears untouched since scientists discovered the mule deer they were studying were unexpectedly and mysteriously dying.
Researchers were baffled. Why were seemingly healthy deer taken from across Colorado’s wilderness turning thin and wasting away toward premature death?
“The reaction to it, quite honestly at the time, was just frustration because it kept ruining good research experiments,’’ says Miller, Colorado Parks and Wildlife senior wildlife veterinarian, whose office is a short walk from the pens where the deer were dying. “The deer didn’t live long enough.’’
That was in 1967.
A half-century later, chronic wasting disease, a mysterious malady intricately tied to Fort Collins, is stirring renewed anxiety as federal officials study once again its potential to spread to humans.
This tale of a disease killing deer and elk across Colorado, Wyoming, Nebraska and pockets of other states is one few have heard. That could all change given recent research that suggests this disease has greater potential than originally thought to cross genetic barriers to harm humans.
Mad cow outbreak spreads first wave of fear
As researchers remained perplexed for more than a decade following the 1967 discovery, the disease marched on mostly undetected, killing wild deer and elk while spreading to commercial game farms and in zoos across the United States and in Canada.
Then in February 1978, a breakthrough was made in the so-called wasting disease case. And it was unsettling.
The late Beth Williams, a veterinary pathology resident at Colorado State University, identified the disease as a transmissible spongiform encephalopathy (TSE). The always-fatal disease in deer, elk and to a lesser extent moose is caused when proteins go rogue, causing a deterioration of the central nervous system, slow emaciation and an ultimately ugly death.
Soon thereafter, researchers discovered chronic wasting disease in mule and black-tailed deer at the Wyoming Game and Fish Department’s Sybille wildlife research facility and soon thereafter in wild elk and deer in Colorado in 1981.
The genie was out of the bottle.
“I was concerned, but we really didn’t know what to do, and initially no one really cared about it in Colorado because it was an odd disease in deer and not correlated to BSE (bovine spongiform encephalopothy, or mad cow disease),’’ said Terry Spraker, pathology professor at CSU. “Then it was found on the Western Slope and in commercial game farms, and that affected elk guides and commercial facilities and that got the governor wanting to test about all the animals (for the disease).’’
While the disease’s initial identification meant little to people other than researchers, its relationship to a disease that a decade later would kill humans in Great Britain gained international attention.
Williams’ discovery of chronic wasting disease, as the disease became known, was related to scrapie in sheep and goats, mad cow disease in cattle and the fatal variant Creutzfeldt-Jakob disease in humans.
In the 1990s, variant CJD killed more than 200 people in Great Britain who ate tainted meat from cattle that were fed byproducts of animals infected with mad cow disease, which was discovered in cows in the 1980s. The disease is similar in some respects to Alzheimer’s in that both are classified as prion protein diseases where dementia is followed by death. The feeding practice was banned and mad cow disease cases subsided.
Still, fear of an outbreak of variant CJD occurring in the United States from people
eating deer, elk and moose infected with chronic wasting disease persisted.
While researchers in the U.S. couldn’t outright discount an outbreak in humans, it didn’t seem plausible that eating meat from animals suffering chronic wasting disease would lead to an outbreak of a disease similar to variant CJD. Health experts found no uptick in the disease in the U.S., not even among hunters — the number of cases held steady, with about one in a million Americans infected.
The spread of chronic wasting disease in deer and elk prompted an increase in research, which to date is around $100 million, including $20 million in Colorado. That research has solved some of the mystery of the disease, but many unanswered questions remain.
And much of that research was spearheaded in Fort Collins by Miller; Spraker; Tom Hobbs, senior research scientist at CSU; as well as in Wyoming by Williams, who first heard of wasting disease in the 1970s as a CSU graduate student.
Did chronic wasting disease originate in Fort Collins?
While leaning against the pen at the CSU Foothills Campus, Miller is quick to point out that chronic wasting disease was first discovered in Fort Collins, but that doesn’t mean it started here.
“This is the place where the term was first coined, but the rest is urban legend of how it started here,’’ Miller said. “Using that same logic, then AIDS started in the U.S., which it didn’t. It was first diagnosed here but it started in Africa.’’
But Fort Collins remains linked to the disease.
Gene Schoonveld, a retired Colorado Division of Wildlife senior wildlife biologist who lives in Fort Collins, knows why.
When the disease was discovered, he was conducting experiments on mule deer in those pens to help them survive starvation during harsh winters. He said about a dozen mule deer were brought in from various areas of Colorado. He believes the deer might have already been infected.
Another hypothesis, he said, is the disease might have crossed species. CSU was conducting scrapie research on domestic sheep and the sheep and deer were together in pens at times.
“We can’t prove either one, and Mike, Terry and I will probably go to our graves never knowing what really happened,’’ Schoonveld said.
While they didn’t know how the disease got to Fort Collins, researchers began discovering by the turn of this century that the disease was spreading. In some hot spots, nearly half of wild adult male deer, or bucks, were infected.
Chronic wasting disease was also spreading among commercial game farms. Quarantines stopped the transfer of captive animals between facilities and zoos. Those restrictions, atop captive animals dying from the disease, crippled the commercial game industry.
Miller and Spraker concur there are likely several ways the disease has spread.
For certain, they said, the disease was spread through transportation of infected animals by commercial facilities and zoos. Some infected animals escaped, and some came into contact with wild animals entering their pens, thus spreading the disease.
Strict regulations on moving captive animals has greatly reduced that mode of contagion, Miller said. So has a ban on giving wild animals protein blocks containing rendered animal byproducts tainted with the disease.
There is also a theory of scrapie crossing over from sheep to wild deer, elk and moose.
“We don’t know all the ways it can be spread, and you could spend a lifetime pondering explanations and never come up with the answer,’’ Miller said.
Research can now explain that the disease is spread among wild and captive deer, elk and moose through saliva, blood and waste, and can persist in the soil — especially the clay soil largely found in Colorado — for long periods of time.
Efforts to find a vaccine to prevent the disease have proved unsuccessful. Management strategies to control infection rates have been met with resistance.
In Colorado, studies around Fort Collins have shown aggressive hunting pressure and/or culling of deer, especially bucks, has reduced the infection rate. But that strategy has been unpopular with some landowners, hunting guides and hunters who covet large bucks.
To date, the disease has not been found in cattle.
Miller said the best hope now is managing the disease so it doesn’t kill deer and elk in such large numbers that herds are reduced to sizes too low to allow hunting. That would be a problem for Colorado, as big game hunting, which recently started, annually draws hundreds of thousands of hunters who have an annual economic impact of around $1 billion, including $38 million in Larimer County, according to a 2014 Colorado Parks and Wildlife survey.
Opposing findings rekindle human infection fears
Years after chronic wasting disease research largely disarmed the public about a risk to human health, the disease continued its slow but steady in deer and elk.
Then, there came a bombshell.
Preliminary results from an unpublished Canadian study released last year found that three of five macaque monkeys contracted CWD when fed the equivalent of a 7-ounce steak of deer meat tainted with the disease once a month for three years.
A similar study conducted by National Institutes of Health in Montana found macaque monkeys did not contract the disease.
According to the NIH, macaques often are used to model human protein diseases because they are genetically similar and susceptible to several types of diseases known to infect people.
The results from the Canadian experiments caused health agencies enough concern that the U.S. Centers for Disease Control and Prevention posted this on its website:
“The reasons for the different experimental results are unknown. To date, there is no strong evidence for the occurrence of CWD in people, and it is not known if people can get infected with CWD prions. Nevertheless, these experimental studies raise the concern that CWD may pose a risk to people and suggest that it is important to prevent human exposures to CWD.’’
Health experts have long recommended people not eat tainted meat and for people to protect themselves from coming into contact with certain parts of deer, elk and moose when field dressing them.
As a scientist, Miller acknowledges you can never rule out a disease crossing species. And he agrees people should reduce the risk of exposure. He continues to research chronic wasting disease because he said reducing its occurrence in animals reduces humans’ risk of exposure.
Still, he said he has cut his hand with a clever used to examine infected deer and has likely unwittingly eaten infected wildlife.
“I don’t want to be dismissive, but I don’t think about (becoming infected) a lot,’’ he said. “I don’t drive without a seat belt, some do. It’s a personal choice.’’
Schoonveld, 81, said he is pretty sure he unknowingly has eaten infected deer and likely fed it to his family. He would be much more careful now.
While he’s unsure if he will contract variant Creutzfeldt-Jakob disease, he knows one thing.
“Can you imagine what would happen if the monkey research simulated in the human population?’’ Schoonveld said. “I do. It would be hell on wheels.’’
5 important things to know about chronic wasting disease
What is chronic wasting disease?
CWD is a fatal neurological disease found in deer, elk and moose. It belongs to a family of diseases caused by prions (abnormally shaped proteins). This particular prion attacks the brains of infected animals, causing the animals to display abnormal behavior, become uncoordinated and emaciated, and eventually die.
Where is CWD found in Colorado?
CWD has been found in deer, elk and moose herds in various locations in Colorado. About half of Colorado’s deer herds and one-third of the state’s elk herds are known to be infected. Deer are about twice as likely to be infected as elk. In deer, bucks are twice as likely to become infected as does, but in elk, the infection rate is the same in males and females. Moose are infected at low rates.
Where else is it found?
It is found in 23 states and two Canadian provinces (Saskatchewan and Alberta) in the wild. Those states include Colorado, Wyoming, Nebraska, Utah, New Mexico, Montana, South Dakota, North Dakota, Kansas, Texas, Iowa, Missouri, Arkansas, Minnesota, Michigan, Wisconsin, Illinois, Pennsylvania, Maryland, Mississippi, New York, Virginia, West Virginia and the provinces of Alberta and Saskatchewan in Canada. The presence of CWD in captive locations includes several more states and provinces. It’s found as far away as Norway, in reindeer, and in Korea.
Is there a risk to humans?
Disease in humans resulting from exposure has not been reported to date. However, there may be a small risk from eating meat from infected animals. Public health officials recommend that people avoid exposure to infected animals. The disease does not appear to be transmissible to cattle.
What CWD precautions and preventive measures should hunters take?
To minimize exposure, Colorado Parks and Wildlife and state public health officials advise hunters not to shoot, handle or consume any deer, elk or moose that is acting abnormally or appears to be sick. When field-dressing game, wear rubber gloves and minimize the use of a bone saw to cut through the brain or spinal cord. Minimize contact with brain or spinal cord tissues, eyes, spleen or lymph nodes. Always wash hands and utensils thoroughly after dressing and processing game meat.
Why should people be concerned about CWD?
CWD poses a significant threat to the future health and vitality of captive and free-ranging mule deer, white-tailed deer, elk and moose populations throughout 26 states and provinces in North America. A growing body of evidence suggests that unchecked epidemics can impair the long-term population of affected herds.
Chronic wasting disease timeline
1967: Wasting syndrome is observed in captive mule deer at the Colorado State University wildlife research facility in west Fort Collins.
1975−81: Wasting syndrome is observed in Toronto Zoo mule deer transferred from the Denver Zoo.
1979: Recognized in captive mule deer at Wyoming wildlife research facility.
1981: Detected in wild elk in Colorado.
1985: Detected in wild mule deer in Colorado and Wyoming.
1996: Detected in a captive elk farm in Saskatchewan; 38 other linked farms eventually found positive.
1997: Detected in captive elk facilities in South Dakota.
1998: Detected in captive elk facilities in Montana and Oklahoma.
1999: World Health Organization indicates no evidence CWD is transmissible to humans, but advises that exposure should be avoided.
2000: Detected in wild mule deer in Nebraska and Saskatchewan.
2002: Colorado establishes guidelines to minimize transport of high-risk carcass materials. First International CWD Symposium is held in Denver.
2002: Detected in captive elk in Minnesota, wild and captive white-tailed deer in Wisconsin and Illinois, mule deer in New Mexico and elk in South Dakota.
2003: Detected in wild mule deer in Utah.
2004: Detected in wild elk in New Mexico.
2005: Detected in moose in Colorado.