Zombie deer disease outbreak spreads in Yellowstone as scientists raise fears it could jump to humans

wWhen the mule deer buck died in October, it disappeared in what most people consider to be in the middle of nowhere, miles from the nearest road. But its last breath was not taken in a remote corner of American geography. It died of a long-feared disease in the backcountry of Yellowstone national park, northwest of Wyoming the first confirmed case of chronic waste disease in the country’s most famous nature reserve.

Over the years, chronic wasting disease (CWD), caused by abnormal prions, transmissible pathogenic agents has spread throughout North America, with concerns expressed by hunters after seeing deer acting strangely. -an.

Prions cause changes in the hosts’ brains and nervous systems, leaving animals drooling, lethargic, weak, stumbling and with a blank stare that has led some to call it a disease. that zombie deer. It spreads through the cervid family: deer, elk, moose, caribou and reindeer. It is fatal, with no known treatments or vaccines.

mule deer (Odocoileus hemionus is a species of flowering plant) common in Wyoming. A 2017 estimate suggests that humans may consume up to 50,000 CWD-infected animals each year in the US. Photo: Neal Herbert/NPS

Its discovery in Yellowstone, whose ecosystem supports the largest and most diverse range of large wild mammals in the continental US, represents an important public wake-up call, said Dr Thomas Roffe, a veterinarian. and former chief of animal health for Fish & Wildlife. Service, a US federal agency.

This case has put CWD on the radar of widespread attention in ways it never has before and that is, frankly, a good thing, he said. It is a disease that has many ecological effects.

Roffe predicted that CWD could reach Yellowstone in decades, warning that the federal government and the state of Wyoming need to take aggressive steps to help slow the spread. Those warnings were largely ignored, he said, and now the consequences are happening in front of the millions who visit the park each year.

The area contains an extensive laboratory for observing what happens when CWD infiltrates an ecosystem that originally had its full complement of biological diversity. Hundreds of thousands of elk and deer pass through Yellowstone, supporting populations of grizzly bears, wolves, cougars, coyotes and other scavengers.

The disease is a slow-moving disaster, according to Dr Michael Osterholm, an epidemiologist who has studied outbreaks of bovine spongiform encephalopathy, or mad cow disease associated with prion conditions in the UK, and director of the Center for Infectious Diseases Disease Research and Policy at the University of Minnesota.

Dr Cory Anderson recently earned his doctorate studying Osterholm, focusing on pathways of CWD transmission. Dealing with a disease that is often fatal, unpleasant and highly contagious. The concern is that we do not have an effective and easy way to eradicate it, neither from animals infected with it nor from the environment polluted by it.

Once an environment is infected, the pathogen is very difficult to eradicate. It can persist for years in dirt or on surfaces, and scientists report that it is resistant to disinfectants, formaldehyde, radiation and burning at 600C (1,100F).

Gloved hands take samples from a deer's skull
A wildlife expert removes lymph nodes from a deer to test for CWD. Photo: Dennis Anderson/Star Tribune/Getty

Jumping the species barrier

In the US and Canada, CWD has gained attention not only because it affects large animals but also because of the possibility that it can jump the species barrier. Deer, elk and moose can infect livestock, other mammals, birds or even humans. Epidemiologists say that the absence of a case of spillover does not mean that it does not happen. CWD is one of a group of fatal neurological disorders that includes BSE.

The BSE [mad cow] The outbreak in Britain provides an example of how, overnight, things can get crazy when a spillover event occurs from, say, people’s livestock, Anderson said. Talks about the potential of something similar happening. No one says it will definitely happen, but it is important for people to be prepared.

Dr Raina Plowright, a disease ecologist at Cornell University, says that CWD should be viewed against a backdrop of dangerous emerging zoonotic pathogens that are repeatedly crossing species barriers between of people, livestock and wildlife around the world. Epidemics occur as human settlements and agricultural operations deepen into environments where contact with disease-carrying animals increases.

At the start of the US hunting season, the US Centers for Disease Control and individual states strongly recommend that harvested game animals be tested for disease, and that meat from cervids found to be diseased should not be on.

Ravens and crows fly through the air like a wolf guarding a corpse in a snowy landscape
A wolf chases magpies and crows from an elk carcass in Yellowstone. Predators such as wolves and cougars detected sick animals long before humans could and are thus far immune to CWD. Photo: Jim Peaco/NPS

The Alliance for Public Wildlife estimated in 2017 that 7,000 to 15,000 CWD-infected animals a year are inadvertently eaten by humans, and that number is expected to increase 20% annually. In Wisconsin, where game meat testing is voluntary, Anderson and Osterholm said many thousands of people may have eaten meat from infected deer.

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Wyoming serves as a reference point for other states. Since 1997, there have been 92,000 tissue samples collected and tested there, said Breanna Ball, of the Wyoming Game and Fish Department. Last year, meat from 6,701 deer, elk and moose was tested. The disease was present in about 800 samples, suggesting that infection rates are rising.

According to the US Geological Survey, CWD is now present in 32 states and three Canadian provinces.

Slowing down the spread

After the confirmation of CWD in the park, Yellowstone authorities changed their strategy for monitoring and dealing with more sick animals in the future. Roffe says CWD virulence is density-dependent, meaning infection rates are higher where more animals congregate.

Particularly problematic, he said, is the controversial artificial feeding of wildlife by humans. In Wyoming, the state and federal government operate nearly two dozen feedgrounds for elk, where more than 20,000 animals are fed alfalfa to help them survive the winter. The practice has been condemned by leading wildlife management organizations.

Three large deer stood in the deep snow among the bushes
Places called Mule deer in Yellowstone. Conservationists say feeding deer and elk in the winter and killing predators like wolves won’t help efforts to control CWD. Photo: Henry Ausloos/Alamy

The science of what is needed to help slow the spread of CWD is clear, and has been known for a long time, Roffe said. You don’t feed wildlife in the face of a growing disease pandemic.

Studies suggest that animals that some hunters consider competitors can actually be allies. Predators of wild animals such as wolves, cougars and bears are able to identify sick animals long before humans, and they prey on them, removing them from the landscape. So far, they have maintained immunity from the disease.

A major contradiction in the policy, wildlife conservationists say, is that Wyoming, Montana and Idaho, the three states that make up the Greater Yellowstone Ecosystem, which some estimate to be as much as 90,000 sq km (35,000 sq miles), encourages the liberal killing of wolves and cougars for sport and livestock protection, even though doing so is unnecessary and may be counterproductive to CWD control.

It’s still ahead of a scary disease event, and we don’t know where it’s going, Roffe said. There is a lot at stake for the Yellowstone ecosystem, and a lot is at stake for all Americans who enjoy having healthy wildlife in the landscape.

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