Scientists are looking for answers as deer disease spreads

Yale Environment 360

Its cause of death was chronic wasting disease (CWD), experts said, making this the first confirmed death of an animal in the park from the disease.
First discovered in deer in Colorado in 1967, CWD has since spread, primarily through wild and captive deer populations, across the United States, Canada, and globally.
While the unusual disease has primarily afflicted white-tailed deer and mule deer, it infects all cervids, including moose, elk, reindeer, and caribou.
The brains of infected animals deteriorate to a spongy consistency.
In humans the prions could cause a variant of Creutzfeldt-Jakob disease, a rapidly progressive neurodegenerative disease.
And the infected deer “are outputting those prions into the environment in their feces and their urine every day.
Nonetheless, it’s estimated that between 7,000 and 15,000 infected animals, mostly deer, are unknowingly consumed by humans annually.
Infected deer meat might not cause a neurological disease for many years, at which point the earlier meat consumption and the illness may seem unconnected.


The body of a mule deer buck was found late last year in a remote area of Yellowstone National Park, close to Yellowstone Lake, by federal officials. Experts stated that chronic wasting disease (CWD) was the cause of death, making this the first documented case of the illness in a park involving an animal.

Though concerning, the finding wasn’t shocking. After being identified in Colorado deer in 1967, chronic wasting disease (CWD) has since spread throughout the US, Canada, and the world, mostly among populations of wild and captive deer. Spread has also been facilitated by the nation’s movement of harvested or live deer. It is currently present in four additional countries, five provinces, and 34 states. The most recent state to confirm cases is California, and British Columbia just discovered its first cases. Within the next ten years, experts predict the disease will spread to all 48 contiguous states.

All cervids, including moose, elk, reindeer, and caribou, are infected by the abnormal disease, though it has mostly affected white-tailed and mule deer.

Because of the thousands of elk, deer, and moose that inhabit and traverse Yellowstone’s untamed landscape, biologists have been particularly concerned about this area, sometimes referred to as America’s Serengeti. Research indicates that herds affected by CWD experience a decline of 3 to 20 percent annually.

Given that Wyoming has 22 state-run and one federally run elk-feeding operations, detection of the disease in Yellowstone was expected. Feeding operations increase the risk of disease transmission because they bring thousands of animals together.

Animals stutter, drool, and stare vacantly in the final days of their lives due to a gradual neurological system decline.

Thomas Roffe, a veterinarian and the former head of wildlife health for the United States, stated that CWD “has huge ecological implications.”. s. Fish and Wildlife Service. “I’ve advised that we will have a serious issue if we develop an illness that we are unable to treat, cure, or get better through vaccination. And CWD is included in that group. “.

There is no other wildlife disease like CWD. The reason behind it is an aberrant or misfolded cell protein. The symptoms of CWD are brought on by this so-called prion, which misfolds normal proteins in the brains of animals on contact. Animals with the infection experience spongy brain degeneration. It’s been called “zombie deer disease” and “the disease from space” because of the way the nervous system slowly deteriorates in the final days of an animal’s life, causing them to drool, stumble, and stare blankly. An animal may take several years to die.

CWD is difficult to detect, always fatal, and lacks a vaccine or treatment. The veterinarian for the California Department of Fish and Wildlife who is in charge of the state’s CWD surveillance and response initiatives, Brandon Munk, stated that “CWD-infected animals can excrete infectious prions before clinical signs appear.”. Once introduced, these prions can remain in the environment for years at a time, making it extremely difficult to stop or manage their spread. “.

Many important efforts are being made to comprehend the nature of CWD as it spreads, but there is still much that is unknown about it. Primarily, there is fear that CWD prions will cross the species barrier and infect humans, much like the AIDS virus did when it infected chimpanzees. A fast-progressing neurodegenerative illness called Creutzfeldt-Jakob disease may be brought on by prions in people.

As director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota, where Michael Osterholm is leading the CWD effort, he said, “We are quite unprepared” if humans contract the disease. Osterholm led the response to Covid-19. We would be in free fall if we saw a spillover at this moment. There aren’t any backup plans regarding what to do or how to investigate further. The disaster is unfolding slowly. “.

In order to convene 70 global experts in public health to begin formulating a contingency plan in the event of a spillover, Minnesota last year funded a CIDRAP project. According to Osterholm, new findings indicate that the prion is changing and getting increasingly capable of infecting people. “A humanized mouse—one that has had its genes altered to mimic the responses of a human immune system—will much more easily pick up the prions that we are currently seeing,” the expert stated. Nowadays, conditions are far better than in the past for leaping into a human cell. “.

Nevertheless, after high concentrations of prions were added to human brain cells, which did not contract the infection, a different recent study from the National Institutes of Health concluded that there was little chance of a spillover.

Both dust and water can spread the aberrant proteins that cause CWD, which can remain contagious for at least 15 years.

In the meantime, two men who consumed venison from a herd known to be infected with CWD developed rapid-onset Creutzfeldt-Jakob disease, according to a case study that was published in the journal Neurology in April of last year. Within a month of exhibiting symptoms, one of the men passed away from the illness, while the other man passed away afterwards. The five writers hypothesised that their frequent consumption of deer meat—prions have been discovered in the muscle tissue of deer—may have contributed to the illness. Although the cases attracted a lot of media attention, other experts pointed out that the paper was just an observation and that further research was necessary to rule out the possibility that the disease was contracted from eating deer meat.

The ecology of CWD is being researched by a different team of specialists at the University of Minnesota. This research is crucial to understanding where CWD has spread and where it might go in the future as well as the best ways to curb or prevent it. According to Peter Larsen, co-director of the Minnesota Center for Prion Research and Outreach and associate professor in the University of Minnesota College of Veterinary Medicine, “we are looking at how prions move through the environment.”.

Prions are being released into the environment in large quantities, he claimed. These substances can spread throughout the environment for extended periods of time, but how long do they stay contagious? “Where are they going, and what does exposure look like?”.

Prions can remain infectious for at least 15 years, according to data from studies on scrapies, a deadly degenerative disease linked to prions that affects sheep and goats but not humans who eat them. Both water and airborne dust can be used to transport them.

According to a recent study, plants have the ability to act as disease vectors by using their roots to absorb prions from the soil, transporting them to aboveground growth, and then infecting animals that eat them. But up until now, that movement has only been observed in lab environments—not in natural environments. Hay imports from areas affected by prion outbreaks are prohibited in some locations.

According to Larsen, prevalence rates range from 30 to 40 percent of a herd of deer in some parts of the nation. Additionally, the diseased deer “are outputting those prions into the environment every day in their urine and feces.”. You can envision a patch of alfalfa with a hundred deer for several days. That is a significant amount of prions in the surroundings. “.

An additional significant unknown is how prions will develop. A study revealed that prions that made their way through voles’ digestive tracts evolved to spread to raccoons.

The existence of wolves in Yellowstone, who are immune to the disease, may be one mitigating factor. Some biologists think that by pursuing and eating animals that are weak from the disease, they could prevent CWD from spreading. Some experts think the relentless spread of CWD may be caused by a lack of predators and scavengers on the landscape. Preliminary models suggest that wolves may delay outbreaks and reduce their size.

Developing a test that hunters could administer in the field is crucial, according to experts, in preventing a potential spread to humans.

Predators and scavengers have the ability to spread the illness simultaneously. According to Larsen, this is one of the CWD’s most worrisome features. We don’t know how CWD prions will evolve or which mammals they will be able to infect, but many species may be exposed to them. “.

Unlike bacteria or viruses, prions are nearly unbreakable, which makes them a unique challenge. They become more concentrated when cooked rather than dying. Antiseptics and radiation cannot kill them either.

Prion diseases have only been known to infect humans once, in the late 1990s and early 2000s, when prions infected cattle and resulted in mad cow disease, also known as bovine spongiform encephalopathy, or BSE. Variant Creutzfeldt-Jakob disease claimed the lives of over 200 beef eaters, mostly in Europe. Still, some scientists think prions could be the cause of other illnesses like multiple sclerosis and Parkinson’s.

However, the number of infected animals—mostly deer—that are unintentionally eaten by people each year is thought to be between 7,000 and 15,000. It is possible to test deer after they are shot, but many hunters choose not to bother because it can take a week to get the results. Development of a test that hunters could administer in the field, yielding results in hours rather than days or weeks, is crucial, according to experts, to stop the disease’s spread and potential human spread.

The extended latency of prions makes their detection in humans difficult. A neurological condition resulting from contaminated deer meat may not manifest for many years, during which time there may be no apparent link between the earlier meat consumption and the illness.

The global spread of the disease is primarily affecting hunters. Although some people have given up eating wild game, most hunters, according to Steve Rinella, host of the television show MeatEater, do not worry about it because CWD has not been observed in humans. If a hunter developed CWD, “that would change dramatically,” he stated. “A hunter developing CWD would be a nightmare.”. “.

For Indigenous people who depend on wild game, the threat presents a special concern. According to Tanya Roerick, the tribe’s director of wildlife programs, “white-tailed deer are an important cultural and food resource for the Leech Lake Band of Ojibwe.”. “To maintain their spiritual and familial ties, not for athletics. “.

She stated that CWD poses a threat to the Ojibwe way of life and has been discovered in three locations within 15 miles of the reservation. The tribe has been offering free CWD testing on deer that its members have harvested for years. According to Roerick, this surveillance “will continue for the foreseeable future.”. “.

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