Earlier this year, a team of scientists sparked a wave of media attention with their provocative report: They claimed to have discovered two cases of a rare but deadly prion disease in hunters, which could have been caused by consumption of contaminated deer meat – a frightening phenomenon. reminder of the mad cow crisis more than 30 years ago. But many outside experts disagree, and recent research has disputed that such a thing is even possible — at least for now.
The report was present by researchers at the University of Texas Health Science Center at San Antonio in early April, during the annual conference of the American Academy of Neurology.
Is it time to be afraid of deer?
They had discovered the case of a 72-year-old man who died in 2022 from Creutzfeldt-Jakob disease, or CJD, the most common but still very rare prion disease in humans. According to the report, the man had a friend at the same hunting lodge who had also recently died of CJD. And both men reportedly ate game from the same deer population, a population in which cases of chronic wasting disease (CWD) have already been detected.
CJD, CWD and other prion diseases are caused by a misfolded version of the harmless prion protein. When a bad prion comes into contact with its normal body, it somehow forces it to turn into another misfolded copy. Over time, this zombie-like accumulation of diseased prions destroys the brain from the inside out, although it can take years or even decades before symptoms such as dementia does not appear. But once they do, death soon follows.
Mammals in general are susceptible to prion diseases, which can occur sporadically or be caused by genetic mutations that make the appearance of these bad prions almost inevitable. But sometimes prions can also be transmitted from one individual to another (the infamous prion disease). which spread by cannibalism), or even between two different animal species. In the 1980s, we learned that cows could develop bovine spongiform encephalopathy, or mad cow disease, from prions, which may have been caught by prion-infected sheep. A few years later, we learned that people could contract a variant of Creutzfeldt-Jakob disease from eating mad cows.
The mad cow epidemic and the resulting outbreaks of vCJD (the variant form) were finally contained through better food safety practices. But CWD in deer, first discovered in the 1960s, has only become a bigger problem over time as the disease has spread farther and farther among deer populations. deer in North America. And UT Health San Antonio researchers argued that a similar chain of events could have occurred with their two hunters.
“The patient’s history, including a similar case in his social group, suggests possible novel animal-to-human transmission of CWD,” they wrote. They also called for more research to be conducted to investigate this possibility.
The team explicitly noted that this potential link between prions and humans was unproven (as was Gizmodo’s study). blanket at the time), but other media outlets were not as careful in their statements. Great Britain Daily Mail‘s big titlefor example, was: “Two hunters “become the first Americans to die from ZOMBIE DEER disease” after eating infected game.
“Incredibly irresponsible”
Leaving the tabloids aside, many outside scientists and organizations still believed the researchers were going too far in their speculation, given how little information was available.
In response to the report, the conservation group Tennessee Wildlife Federation declared that “attempting to link sporadic cases of CJD in humans to CWD without documentation or evidence is incredibly irresponsible.” The Centers for Disease Control and Prevention has been more generous, with CDC epidemiologist Ryan Maddox narrative USA today in late April that it was important to assess the potential risk of CWD transmission to humans, but also that the CDC had reviewed these cases and ruled out any link to CWD.
Many details of these cases, including the older age of the victims, “were all consistent with what we normally see in classic, sporadic CJD not attributed to CWD,” Maddox said. In contrast, cases of vCJD caused by infected beef tend to occur in much younger people.
Gizmodo contacted experts at Case Western University’s National Prion Disease Surveillance Center about the report, who were equally skeptical, although they emphasized the importance of tracking CWD in deer.
“The NPDPSC found no evidence of transmission of chronic wasting disease to humans; however, continued monitoring is warranted given the increasing spread of the disease,” Brian Appleby, director of the center, told Gizmodo in an email.
Some animal studies, including non-human primates, have revealed evidence that chronic wasting disease prions could potentially infect and sicken humans, but other this is not the case with research. A new study on this same subject was published last month, conducted by researchers at the US National Institute of Allergy and Infectious Diseases, and it too was reassuring.
Nothing to find
The team, led by NIAID researcher Cathryn Haigh, had already learned how to create lab-grown organoids – miniaturized versions of our organs – from our brain that can be reliably infected with human CJD prions. These organoids, in addition to saving time and animal lives, should also more accurately model how prions make us sick and could even help us discover or test drugs that can stop them.
In this new research, Haigh’s team once again easily infected their organoids with CJD, which served as their control comparison. They also soaked other organoids in CWD prions taken from several species of deer and elk for a week straight and observed them for six months.
“The short story is: We couldn’t see anything,” Haigh, head of the Prion Cell Biology Unit at NIAID’s Neurological Infections and Immunity Laboratory, told Gizmodo.
Haigh does not entirely rule out the risk of CWD being transmitted to humans. It’s not impossible that a strain of CWD emerges that could one day cross the species barrier, for example. And Haigh’s team continues to study the topic, with an upcoming study aimed at testing whether CWD prions can infect human intestinal tissue, likely a crucial step toward brain infection from eating contaminated venison. But for now, judging from their and other research, she’s not too worried. “We believe that currently the risk of CWD transmission to humans is low,” she said.
As for the recent report, Haigh doesn’t mince words about his opinion on it.
“Personally, I thought it was alarmist. I don’t think they presented anything that would worry people on the ground,” she said.
Gizmodo contacted several of the authors of the MDC case report, both before its publication in April and recently, who did not directly respond. Monica Taylor, senior director of public and media relations at UT Health San Antonio, responded to our latest inquiry. Taylor noted, correctly, that the team’s case report was not a peer-reviewed study, but a poster presentation at a conference.
“The conclusion of this presentation is that there are no proven cases of transmission to date,” Taylor added.
So yes, if you are a venison lover, there is no immediate need to reduce your habit. Just make sure you cook it. You may never get prions from deer, but any type of undercooked meat is likely to contain germs or parasites that can still make you sick, including game meat.