"Zombie deer disease" is spreading in the United States. What is it?


An infectious disease similar to mad cow disease that can turn the brains of deer, elk and moose into "Swiss cheese" spreads in at least 24 states – and some experts warn that it could eventually end up in humans.

The fatal progressive neurodegenerative disease, known as the chronic debilitating disease – commonly known as "zombie deer disease", was first identified in the 1960s. Like mad cow disease, chronic debilitating disease is transmitted through prions , zombie-like pathogenic proteins that are not alive and can not be killed. When they infect an animal, they gnaw at the brain, causing a cascade of symptoms that resemble dementia and possibly death. Although the disease is still rare, researchers believe it is more prevalent than ever, partly because of the way humans negotiate deer and other hoofed mammals.

"What we have seen in recent decades is that the virus is spreading slowly in wild deer populations," said Peter Larsen, assistant professor of veterinary science at the University of Minnesota, who studied the pathogenic. It also spreads among captive deer, elk and reindeer, which are transported around the country and abroad to hunting ranches, children's zoos and Christmas themed farms. That's how the disease ended up in South Korea, said Larsen. (He has also been identified in Canada and Norway.)

When new outbreaks begin, they are virtually impossible to contain because, unlike viruses and bacteria, prions can not be killed and there is currently no effective way to detect them.

Researchers have long wondered whether the disease, like mad cow disease, can make the leap in humans. (The mad cow in humans is known as Creutzfeldt-Jakob disease.) At the end of last summer, we had a scary preliminary response. In an article published in the journal Emerging infectious diseasesScottish and Canadian researchers have shown, thanks to a Petri dish experiment, that the prions of sick animals can actually infect human cells.

Since then, there has been no direct evidence of human illness. The research has prompted Michael Osterholm, director of the Center for Infectious Disease and Policy Research at the University of Minnesota, to compare chronic debilitating disease with mad cow disease. Osterholm also warned the British government of the risks of mad cow disease before hundreds of people became infected in the UK and around the world in the late 1990s. Before a Minnesota State Committee on February 7 , he described as "probable" and "possible" the risks of infection by a chronic disease of wasting in humans, adding, "The number of human cases will be considerable and will not be an isolated event" .

According to Larsen, this is not the time to panic, but warned that this poses a growing threat to public health. People should not eat infected meat, he said, but stressed that there was actually no way to know if the meat was infected. "There is currently no way for people to quickly test prions in meat, on meat processing surfaces or in live deer," he said. "Ultimately, we must act now to develop new technologies to detect and destroy prions."

Let's review what we know about this emerging infectious disease.

1) What is "zombie deer disease"?

Named officially chronic debilitating disease, zombie deer disease is a progressive and life-threatening neurodegenerative disease that would affect deer, elk, reindeer and moose. It was discovered in Colorado deer in the 1960s, and since then it has intrigued scientists.

The disease is caused by prions, which are neither viruses nor bacteria. Prions are almost indestructible pathogenic proteins that cause abnormal cell folding, particularly in the brain and spinal cord, and lumping. When this happens, infected animals begin to develop a range of frightful symptoms – dementia, hallucinations and difficulty walking, talking and eating. The animals end up becoming wobbly and disoriented. These symptoms worsen over time and, as there is no cure, they always result in death.

The reason the disease has received its official name – chronic wasting disease – is that when prions take precedence over an animal, it begins to lose weight and wither. Prions "turn the brain into Swiss cheese," said Larsen.

But Larsen described the "zombie deer disease" as an unfortunate and potentially misleading nickname. "I saw only one dead deer from [chronic wasting disease] and he was emaciated, "he said." There are no zombie-like symptoms.Instead, the symptoms correspond to what you expect from a very sick animal: thin weak and unable to function normally.

"It's important to remember that [this] is a neurodegenerative disease – not a zombie disease in Hollywood. "

2) How is it transmitted in animals?

An animal with chronic debilitating disease can transmit prions to other animals through direct or indirect contact with bodily fluids such as stool, saliva, blood or urine. This means that the disease can spread if an infected deer is injured, for example, and its blood is touching an uninfected animal. or if a healthy animal comes into contact with soil, food or water contaminated by a sick deer.

That's not all, said Larsen. Because prions are so robust, they can survive in environments – farms, forests – for years, if not decades. "So, let's say you have a deer with chronic wasting disease, and he started to lose [prions] in his urine, his excrement, his saliva. If this deer dies on the forest floor, prions can survive and bind to the soil, where the plants absorb them. These plants can then spread prions through their leaves, said Larsen.

"So, it is spreading in nature, slowly. And every year, we see more and more cases of chronic wasting. "

3) How would this spread to people?

There has been no documented case of chronic debilitating disease in humans – but researchers believe this is possible and becomes more likely as infections become more common in animals.

Until now, the only evidence that scientists have spread to other animals is indirect. In laboratory experiments, scientists have shown that the disease can spread in squirrel monkeys and mice carrying human genes, says the Center for Disease Control and Prevention. In a forthcoming study, macaques – a primate species genetically similar to humans – fed on infected meat contracted the disease.

"The experiments are [also] Researchers take environmental samples, such as rocks or pieces of wood, that have [pathogenic] let's pray over them, "said Larsen." They then place these contaminated objects in cages with transgenic hamsters and these hamsters develop the disease. "

Finally, in another recently published study, researchers found that chronic dieback of prions of the disease infected human cells in a petri dish.

The CDC says that these experiences "raise the concern that [chronic wasting disease] may pose a risk to people and suggest that it is important to prevent human exposure to [the disease]. The most likely way to do this is if a person, such as a hunter, eats contaminated meat.

This brings us to another troubling fact about chronic debilitating disease: "With a prion, you can not [cook it off]. The temperatures needed to destroy it are way beyond what you can cook, "said Larsen.

The only way to make the prions non-infectious is to use detergent, a strongly alkaline solution that radically alters the pH balance, and to autoclave – or treat them under pressure – to 270 degrees Fahrenheit . "Most people do not have access to this approach," said Larsen. "The fact is that it is difficult to manage [infectious] pray in the environment because we do not know exactly where they are hiding. This brings us to the next problem of this disease.

4) Where is the zombie deer disease in the United States?

Well, we only know where the chronic debilitating disease was. Deer can only be diagnosed after death (researchers must have access to tissues deep in the animal's brain and test them). But animals can carry pathogens for years and have no signs or symptoms. "This deer could make a 40-mile trip, sprinkling [infected] pray in the stool or urine, "said Larsen. "If we are going to say that it's a [chronic wasting] deer on this point on the map, what you do not see on this map is everywhere it has been in the past two years. "

By January 2019, 251 counties in 24 states had reported chronic wasting disease in wild deer, the CDC reported. You can see them here:

Chronic debilitating disease in wild deer reported by United States County in January 2019.

Again, however, researchers believe that the spread range is much wider. The CDC also noted that some states have better animal disease surveillance systems than others. As a result, the current map is more reflective of the strongest detection zones (and earlier diseases) than those where deadly prions are currently spreading in the United States.

5) Can we prevent the disease from spreading?

As there is currently no way to eradicate and cure the disease, researchers recommend that states in which it spreads should attempt to contain it by identifying diseased animals.

Now, here is another problem: the tools available to do this are very limited. Diagnoses to detect disease in animals are not always accurate, not all states have access to them, and again, they can only confirm the presence of infection in an animal after death. It can also take days or weeks to get results. This means that the illness may be moving for a moment before everyone knows it is there.

That's why Jeremy Schefers, a veterinary pathologist at the University of Minnesota, recently urged lawmakers in his state to fund research to develop better diagnostic tools and help scientists respond fundamental questions about chronic wasting. Schefers Addresses Minnesota Post:

We have to find infected animals before they die, but we do not have a test. … We need to know how other animals move the MDC prion into the environment, but we do not have a test for that.

We need to know if local butchery is contaminated and if it can be cleaned effectively, but we have no test on it. We need to know if the prions move from the soil to the plants and are potentially infectious, but we do not have a test for that. … I want to know how much there is in the soil and how much it takes to infect something, but we have no test for that.

All hunters need access to an easy-to-buy test and quick detection of CWD in their deer before it is cut into 100 pieces and distributed to their families. These hunters do not have access to a test.

6) How can people protect animals and themselves?

Health officials are especially worried about the potential exposure of hunters to the disease through animals carrying prions. Thus, anyone who is hunting in areas where chronic debilitating disease is spreading should take the following precautions, according to the CDC:

  • Do not shoot, handle or eat elk or deer that look unhealthy or "act strangely".
  • When dressing (or removing organs) from a hunted animal, wear latex or rubber gloves, avoid touching animal organs – especially brain tissue and spinal cord – and avoid using utensils that are also used at home.
  • Have deer or elk meat tested for prion disease before eating. However, the CDC also warns that, as the diagnostic tools for the disease are still limited, "a negative test result does not guarantee that an individual animal is not infected" by chronic wasting disease although this "may reduce your risk of exposure"
  • When processing meat commercially, ask the butcher if he handles and treats multiple animals at once (to avoid cross-contamination).

What about consumers of game meat, such as game, and restaurants that serve it? In this regard, Larsen did not get a comforting answer.

He advised anyone who ate game meat or a game restaurant to ask where the meat came from. And restaurants should make sure their meat is free of the disease. But again, in practice, it's not easy, because of the time needed to get the results of diagnostic tests.

"If you are a hunter and you kill a deer to feed your family or sell, are you going to wait two weeks? [for a test result]? Larsen asked. "How do you keep fresh meat?"

Thus, although consumers have the right to know if their meat has been infected with pathogenic prions, there is currently no effective way to get an answer.

"Humans have interacted with deer for centuries," said Larsen, "to feed, play sports or just watch them in the wild." But this tradition is "attacked now because of this agent pathogenic".


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