TITLE: Deer Are Beta-Testing a Nightmare Disease
https://www.theatlantic.com/science/archive/2024/02/deer-chronic-wasting-disease-prions-spillover-people/677307/
EXCERPT: Scott Napper, a biochemist and vaccinologist at the University of Saskatchewan, can easily envision humanity’s ultimate doomsday disease. The scourge would spread fast, but the progression of illness would be slow and subtle. With no immunity, treatments, or vaccines to halt its progress, the disease would eventually find just about every single one of us, spreading via all manner of body fluids. In time, it would kill everyone it infected. Even our food and drink would not be safe, because the infectious agent would be hardy enough to survive common disinfectants and the heat of cooking; it would be pervasive enough to infest our livestock and our crops. “Imagine if consuming a plant could cause a fatal, untreatable neurodegenerative disorder,” Napper told me. “Any food grown within North America would be potentially deadly to humans.”
This nightmare illness doesn’t yet exist. But for inspiration, Napper needs to look only at the very real contagion in his own lab: chronic wasting disease (CWD), a highly lethal, highly contagious neurodegenerative disease that is devastating North America’s deer, elk, and other cervids.
In the half century since it was discovered in a captive deer colony in Colorado, CWD has worked its way into more than 30 U.S. states and four Canadian provinces, as well as South Korea and several countries in Europe. In some captive herds, the disease has been detected in more than 90 percent of individuals; in the wild, Debbie McKenzie, a biologist at the University of Alberta, told me, “we have areas now where more than 50 percent of the bucks are infected.” And CWD kills indiscriminately, gnawing away at deer’s brains until the tissue is riddled with holes. “The disease is out of control,” Dalia Abdelaziz, a biochemist at the University of Calgary, told me.
What makes CWD so formidable is its cause: infectious misfolded proteins called prions. Prion diseases, which include mad cow disease, have long been known as terrifying and poorly understood threats. And CWD is, in many ways, “the most difficult” among them to contend with—more transmissible and widespread than any other known, Marcelo Jorge, a wildlife biologist at the University of Georgia, told me. Scientists are quite certain that CWD will be impossible to eradicate; even limiting its damage will be a challenge, especially if it spills into other species, which could include us. CWD is already a perfect example of how dangerous a prion disease can be. And it has not yet hit the ceiling of its destructive potential.
Among the world’s known infectious agents, prions are an anomaly, more like zombies than living entities. Unlike standard-issue microbes—viruses, bacteria, parasites, fungi—prions are just improperly folded proteins, devoid of genetic material, unable to build more of themselves from scratch, or cleave themselves in two. To reproduce, they simply find properly formed proteins that share their base composition and convert those to their aberrant shape, through mostly mysterious means. And because prions are slightly malformed versions of molecules that our bodies naturally make, they’re difficult to defend against. The immune system codes them as benign and ignores them, even as disease rapidly unfolds. “This is an entirely new paradigm of infectious disease,” Napper told me. “It’s a part of your own body that’s turning against you.”
And yet, we’ve managed to keep many prion diseases in check. Kuru, once common in the highlands of Papua New Guinea, was transmitted through local rituals of funerary cannibalism; the disease fizzled out after people stopped those practices. Mad cow disease (more formally known as bovine spongiform encephalopathy) was contained by culling infected animals and eliminating the suspected source, cow feed made with infected tissues. Even scrapie, a highly contagious prion disease of sheep and goats, is limited to livestock, making it feasible to pare down infected populations, or breed them toward genetic resistance.
CWD, meanwhile, is a fixture of wild animals, many of them migratory. And whereas most other prion diseases primarily keep quarters in the central nervous system, CWD “gets in pretty much every part of the body,” Jorge told me. Deer then pass on the molecules, often through direct contact; they’ll shed prions in their saliva, urine, feces, reproductive fluids, and even antler velvet long before they start to show symptoms. Candace Mathiason, a pathobiologist at Colorado State University, and her colleagues have found that as little as 100 nanograms of saliva can seed an infection. Her studies suggest that deer can also pass prions in utero from doe to growing fawn.
Deer also ingest prions from their environment, where the molecules can linger in soil, on trees, and on hunting bait for years or decades. A team led by Sandra Pritzkow, a biochemist at UTHealth Houston, has found that plants can take up prions from the soil, too. And unlike the multitude of microbes that are easily done in by UV, alcohol, heat, or low humidity, prions are so structurally sound that they can survive nearly any standard environmental assault. In laboratories, scientists must blast their equipment with temperatures of about 275 degrees Fahrenheit for 60 to 90 minutes, under extreme pressure, to rid it of prions—or drench their workspaces with bleach or sodium hydroxide, at concentrations high enough to rapidly corrode flesh.
Infected deer are also frustratingly difficult to detect. The disease typically takes years to fully manifest, while the prions infiltrate the brain and steadily destroy neural tissue. The molecules kill insidiously: “This isn’t the kind of disease where you might get a group of deer that are all dead around this watering hole,” Jorge told me. Deer drift away from the herd; they forage at odd times. They become braver around us. They drool and urinate more, stumble about, and begin to lose weight. Eventually, a predator picks them off, or a cold snap freezes them, or they simply starve; in all cases, though, the disease is fatal. Because of CWD, deer populations in many parts of North America are declining; “there is definitely some concern that local populations will disappear,” McKenzie told me. Researchers worry the disease will soon overwhelm caribou in Canada, imperiling the Indigenous communities who rely on them for food. Hunters and farmers, too, are losing vital income. Deer are unlikely to go extinct, but the disease is depriving their habitats of key grazers, and their predators of food.
In laboratory experiments, CWD has proved capable of infecting rodents, sheep, goats, cattle, raccoons, ferrets, and primates. But so far, jumps into non-cervid species don’t seem to be happening in the wild—and although people eat an estimated 10,000 CWD-infected cervids each year, no human cases have been documented. Still, lab experiments indicate that human proteins, at least when expressed by mice, could be susceptible to CWD too, Sabine Gilch, a molecular biologist at the University of Calgary, told me.
And the more prions transmit, and the more hosts they find themselves in, the more opportunities they may have to infect creatures in new ways. Prions don’t seem to evolve as quickly as many viruses or bacteria, Gilch told me. But “they’re not as static as we would like them to be.” She, McKenzie, and other researchers have detected a multitude of CWD strains bopping around in the wild—each with its own propensity for interspecies spread. With transmission so unchecked, and hosts so numerous, “this is kind of like a ticking time bomb,” Surachai Supattapone, a biochemist at Dartmouth, told me.
TITLE: Possibility of Wildlife-to-Human Crossover Heightens Concern About Chronic Wasting Disease
https://kffhealthnews.org/news/article/chronic-wasting-disease-deer-cervids-hunting-prions/
EXCERPT: Each fall, millions of hunters across North America make their way into forests and grasslands to kill deer. Over the winter, people chow down on the venison steaks, sausage, and burgers made from the animals.
These hunters, however, are not just on the front lines of an American tradition. Infectious disease researchers say they are also on the front lines of what could be a serious threat to public health: chronic wasting disease.
The neurological disease, which is contagious, rapidly spreading, and always fatal, is caused by misfolded proteins called prions. It currently is known to infect only members of the cervid family — elk, deer, reindeer, caribou, and moose.
Animal disease scientists are alarmed about the rapid spread of CWD in deer. Recent research shows that the barrier to a spillover into humans is less formidable than previously believed and that the prions causing the disease may be evolving to become more able to infect humans.
A response to the threat is ramping up. In 2023, a coalition of researchers began “working on a major initiative, bringing together 68 different global experts on various aspects of CWD to really look at what are the challenges ahead should we see a spillover into humans and food production,” said Michael Osterholm, an expert in infectious disease at the University of Minnesota and a leading authority on CWD.
“The bottom-line message is we are quite unprepared,” Osterholm said. “If we saw a spillover right now, we would be in free fall. There are no contingency plans for what to do or how to follow up.”
The team of experts is planning for a potential outbreak, focusing on public health surveillance, lab capacity, prion disease diagnostics, surveillance of livestock and wildlife, risk communication, and education and outreach.
Despite the concern, tens of thousands of infected animals have been eaten by people in recent years, yet there have been no known human cases of the disease.
Many hunters have wrestled with how seriously to take the threat of CWD. “The predominant opinion I encounter is that no human being has gotten this disease,” said Steve Rinella, a writer and the founder of MeatEater, a media and lifestyle company focused on hunting and cooking wild game.
They think, “I am not going to worry about it because it hasn’t jumped the species barrier,” Rinella said. “That would change dramatically if a hunter got CWD.”
Other prion diseases, such as bovine spongiform encephalopathy, also known as mad cow disease, and Creutzfeldt-Jakob disease, have affected humans. Mad cow claimed the lives of more than 200 people, mostly in the United Kingdom and France. Some experts believe Parkinson’s and Alzheimer’s also may be caused by prions.
First discovered in Colorado in captive deer in 1967, CWD has since spread widely. It has been found in animals in at least 32 states, four Canadian provinces, and four other foreign countries. It was recently found for the first time in Yellowstone National Park.
Prions behave very differently than viruses and bacteria and are virtually impossible to eradicate. Matthew Dunfee, director of the Chronic Wasting Disease Alliance, said experts call it a “disease from outer space.”
Symptoms are gruesome. The brain deteriorates to a spongy consistency. Sometimes nicknamed “zombie deer disease,” the condition makes infected animals stumble, drool, and stare blankly before they die. There is no treatment or vaccine. And it is extremely difficult to eradicate, whether with disinfectants or with high heat — it even survives autoclaving, or medical sterilization.
Cooking doesn’t kill prions, said Osterholm. Unfortunately, he said, “cooking concentrates the prions. It makes it even more likely” people will consume them, he said.
Though CWD is not known to have passed to humans or domestic animals, experts are very concerned about both possibilities, which Osterholm’s group just received more than $1.5 million in funding to study. CWD can infect more parts of an animal’s body than other prion diseases like mad cow, which could make it more likely to spread to people who eat venison — if it can jump to humans.
Researchers estimate that between 7,000 and 15,000 infected animals are unknowingly consumed by hunter families annually, a number that increases every year as the disease spreads across the continent. While testing of wild game for CWD is available, it’s cumbersome and the tests are not widely used in many places.
A major problem with determining whether CWD has affected humans is that it has a long latency. People who consume prions may not contract the resulting disease until many years later — so, if someone fell sick, there might not be an apparent connection to having eaten deer.
TITLE: China reports death of woman from two combined strains of bird flu
https://www.independent.co.uk/asia/china/china-bird-flu-infection-death-b2487822.html
EXCERPT: The 63-year-old woman from Anhui province in China died due to the combined infection, attributed to cross-species transmission, on 16 December.
According to reports, the woman had underlying health conditions.
Her symptoms included cough, sore throat, and fever that started on 30 November.
China’s National Disease Control and Prevention Administration stated that screenings of her close contacts yielded negative results, and no suspected cases were found.
“The outbreak is an episodic cross-species transmission from bird to humans,” the statement from the National Disease Control and Prevention Administration said.
The agency described the incident as an isolated case of bird-to-human transmission, emphasising the low risk of the virus infecting people and confirming that no human-to-human transmission has occurred.
The situation in China, with its large populations of farmed and wild birds, provides an environment conducive to the mixing and mutation of avian viruses.
Meanwhile, last year in April, a woman died from H3N8 bird flu in China in the first known human fatality from the avian influenza strain.
The World Health Organisation confirmed the death from the virus which had not been detected in humans before two non-fatal cases emerged – both also in China – in April and May 2022.
The woman who died was a 56-year-old from Guangdong province in southeast China.
H3N8 is known to have been circulating since 2002 after first emerging in North American waterfowl. It is known to infect horses, dogs and seals.