wattWhen a black-tailed deer dies in October, it does so in what most would consider a remote location, miles from the nearest road. But its last breath did not occur in a remote corner of American geography. It died of a long-feared illness in a remote area of Yellowstone National Park in northwestern Wyoming, the first confirmed case of chronic wasting disease in the country’s most famous natural preserve.
Chronic wasting disease (CWD), caused by an abnormal, transmissible pathogen called prions, has been quietly spreading across North America for years, largely as a result of concerns expressed by hunters after spotting unusual deer behavior.
Prions cause changes in the host’s brain and nervous system, causing the animal to drool, be lethargic, emaciated, stumble, and have hollow eyes. Some call it “zombie deer disease.” It spreads through members of the cervid family: deer, elk, moose, reindeer and caribou. It is fatal and has no known treatment or vaccine.
“Yellowstone’s ecosystem supports the largest and most diverse collection of large wild mammals in the continental United States, and the discovery in Yellowstone is an important wake-up call for the public,” said Dr. Thomas Roffe, veterinarian and former director of animal health for the Fish and Wildlife Service. alarm bell. Service, a U.S. federal agency.
He said the case has brought CWD to wider attention than ever before, which, ironically, is a good thing. This is a disease with huge ecological consequences.
Rove has predicted for decades that CWD would reach Yellowstone and warned that both the federal government and the state of Wyoming needed to take aggressive steps to help slow its spread. The warnings went largely unheeded, he said, and now the consequences will be felt in front of the millions of visitors who visit the park each year.
The region constitutes a giant laboratory for observing what happens when CWD infiltrates an ecosystem with its original intact biodiversity. Hundreds of thousands of elk and deer roam Yellowstone, providing habitat for grizzly bears, wolves, cougars, coyotes and other scavengers.
The disease is a slow-moving scourge, said Dr. Michael Osterholm, an epidemiologist and director of the Center for Infectious Disease Research and Policy who has studied British bovine spongiform encephalopathy, or mad cow disease, a disease related to prions. related disease) outbreaks. at the University of Minnesota.
Dr. Cory Anderson recently completed his PhD under the supervision of Osterholm, focusing on the transmission pathways of CWD. We are dealing with an always fatal, incurable, and highly contagious disease. Worryingly, we do not have an effective, simple way to eradicate it, either from the animals it infects or the environments it contaminates.
Once an environment is infected, the pathogen is difficult to eradicate. It can last for years on dirt or surfaces, and scientists report it is resistant to disinfectants, formaldehyde, radiation and incineration at 600C (1,100F).
Crossing species barriers
In the United States and Canada, CWD is a cause for concern not only because it affects large animals but also because of its potential to cross species barriers. Deer, elk and moose may infect livestock, other mammals, birds and even humans. Epidemiologists say the lack of spillover cases doesn’t mean it won’t happen. CWD is one of a group of fatal neurological diseases that includes BSE.
mad cow disease [mad cow] Anderson said the outbreak in the UK provided an example of how things can go crazy overnight when there is a spillover from livestock to humans and beyond. We’re talking about the possibility of something like that happening. No one is saying this will definitely happen, but it’s important for people to be prepared.
Dr. Raina Plowright, a disease ecologist at Cornell University, said CWD should be viewed in the context of dangerous emerging zoonotic pathogens that are spreading back and forth across species barriers between humans, livestock and wildlife around the world. Outbreaks occur as human settlements and agricultural operations penetrate the environment and increase contact with disease-carrying animals.
As hunting season begins in the United States, the Centers for Disease Control and states strongly recommend that harvested game be tested for disease and that meat from cervids showing disease should not be eaten.
The Public Wildlife Alliance estimated in 2017 that 7,000 to 15,000 CWD-infected animals are unknowingly eaten by humans each year, and that number is expected to increase by 20 percent each year. Anderson and Osterholm said wild game testing is voluntary in Wisconsin and thousands of people may have eaten meat from infected deer.
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Wyoming can serve as a reference point for other states. Since 1997, 92,000 tissue samples have been collected and tested, 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, showing infection rates are rising.
According to the U.S. Geological Survey, CWD is now present in 32 states and three Canadian provinces.
slow the spread
After CWD was confirmed in the park, Yellowstone authorities are modifying their surveillance strategies and handling more sick animals in the future. CWD’s virulence depends on density, meaning infection rates are higher where large numbers of animals gather, Roff said.
Particularly controversial, he noted, is the artificial feeding of wild animals by humans. In Wyoming, state and federal governments operate nearly two dozen elk feedlots, providing alfalfa to more than 20,000 animals to help them survive the winter. The practice has been condemned by major wildlife management groups.
Roffe said the science needed to slow the spread of CWD is clear and has long been known. You don’t feed wild animals in the face of a growing disease epidemic.
Research shows that some animals that hunters view as competitors may actually be allies. Wildlife predators such as wolves, mountain lions and bears are able to detect sick animals before humans do and prey on them, removing them from the landscape. So far, they have maintained immunity to the disease.
Wildlife activists say a major policy contradiction is that the three states of Wyoming, Montana and Idaho make up the Greater Yellowstone Ecosystem, which some estimate stretches 90,000 square kilometers (35,000 square miles) ), they encourage the indiscriminate killing of wolves and mountain lions for sport and livestock conservation, even when doing so is unnecessary and may be counterproductive to controlling CWD.
“We’re still on the front end of a terrible disease event, and we don’t know where it’s going,” Rove said. There’s a lot at stake for Yellowstone’s ecosystem, and for all Americans who like to have healthy wildlife on this land.
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