In the last weeks, we have been reading yellowish notes and with bad information about the disease by prions, chronic cachexia, or Chronic Waste Disease, in English, misnamed “zombie deer disease.”
What is a chronic wasting disease?
Across the Atlantic, we speak of “zombie deer disease.” Chronic wasting disease (CWD) in cervids primarily affects North American deer, white-tailed deer, mule deer (or hemione), elk, and reindeer.
It was first observed in the United States, in 1967, in Colorado. Then it spread to 23 other US states and two Canadian provinces, Alberta and Saskatchewan. In 2016, it was detected in Europe for the first time in reindeer and elk in Norway.
It is a fatal degenerative disease of the central nervous system of cervids, of the same family (transmissible spongiform encephalopathy), as the so-called mad cow disease, sheep scrapie Creutzfeldt-Jakob disease. CWD is caused by a prion that derives from a protein naturally present in the body of mammals, which can fold up and change shape, thus becoming harmful. Healthy prions are contaminated, and their “accumulation causes the bursting of nerve cells,” explains Quebec’s government, on its site dedicated to forests, wildlife, and parks.
A variant of mad cow disease
Of course, the nickname of this disease should not be taken literally: infected deer do not go so far as to become ugly bloodthirsty creatures, but they are nonetheless sadly insane: difficulty in standing, listlessness, salivation, rapid weight loss (hence the name “debilitating”), and aggression towards commonly feared species are all symptoms of CWD. Unfortunately, there is currently no known treatment or vaccine. Contaminated deer, elk, or elk are then condemned to die generally a few months after being infected.
Although identified in 1978, cervid encephalopathy remains poorly understood. It is known to be caused by a prion – in other words, a protein that attacks the brain and spinal tissues – and transmitted via body fluids or water consumed by animals. In fact, animals in captivity would be more vulnerable to it. Even more confusing: while most deer develop the famous symptoms, others die suddenly without showing the slightest warning sign.
It is also known to have many similarities to a much more studied disease: bovine spongiform encephalopathy (BSE), also known as mad cow disease. The same one that terrorized Europe at the end of the 1990s. A total of 223 people died in the world after eating contaminated meat and developing Creutzfeldt-Jakob disease, a kind of “human derivative” of the ESB. It is mainly for this reason that zombie deer are considered by some researchers to be a threat to humans.
How is it transmitted?
The method of transmission of CWD is uncertain. “Contact between sick and healthy animals is probably contagious, but the real route is not known. Both saliva and feces must play a role. Therefore the oral route must represent the most usual route of contamination, ” writes François Moutou of the Epidemiology Unit, French Food Safety Agency (Afssa Lerpaz), in an article on the disease the scientific journal Virology, in 2005.
The prion is present in the stool, urine, saliva, and blood of affected animals; very resistant, the prion contagious, and can remain active for several years in the environment.
When the disease affects herds and no longer wild animals, the breeder must slaughter all animals.
How does it manifest itself?
Infected animals do not immediately show visible signs of the disease. They appear between 18 and 48 months after infection. Animals lose weight, and their behavior changes.
“We note a decrease in vigilance, less social interactions on the part of sick animals, phases of hyperexcitability, stereotypical behaviors, hyperesthesia, and a decline in eyesight,” reports François Moutou. Animals are shaking, drooling, eating all the time, but losing weight. Hence the nickname of zombie deer. The disease is incurable, and no vaccine exists to prevent it.
Is there a risk for humans?
Until now, there have been no cases of humans affected by this disease. But a team of researchers from the University of Calgary (Canada), along with scientists from the Canadian Food Inspection Agency (Asia), may have discovered the bad news. They presented the preliminary results of their study started in 2009, and according to them, CWD can infect people who eat deer carrying this prion.
These scientists carried out macaques (the monkeys that have the most similarities to humans) and found that the primates contracted the disease after regularly eating infected meat. Not all 5 of 18 animals exposed to the disease showed signs of transmission. “The most cautious approach is to consider that CWD has the potential to infect humans,” the agency notes in a press release.
According to estimates from the Alliance for Public Wildlife, a Canadian organization that advocates for North American wildlife conservation, between 7,000 and 15,000 infected animals are eaten each year by hunting families in Canada. And the quantities are increasing by 20% every year.
Experts are advising hunters who capture deer in areas where the disease is present to have the meat tested before consuming it (a policy already in place in the two affected Canadian provinces) and to extend testing to farms. The Asia study is to continue at least until 2020.
Before panic, vigilance
Do we really have to worry? Difficult to say at the moment. First, remember that no human being seems to have fallen ill after having ingested contaminated meat. Second, there is no proof for the moment that the prions responsible for encephalopathy in deer have the same “saponifying” effect on the human brain. And this, even if Trevor Ames mentioned experimental results showing the possibility of transmission to primates.
In an interview with Health magazine, Professor Brian Appleby, director of the National Prion Disease Surveillance Center, raises a genuine threat: the inability to contain an epidemic that affects wild animals. “With cattle, sheep, or goats, slaughter helps contain [the disease]. The deer are free, and we don’t have the luxury of being able to neutralize them to stop the spread.”
The CDC (Center for Disease Control) recommends the following:
- Do not hunt or consume meat from animals with erratic behavior or found dead, mainly in areas of greater impact.
- Analyze the meat at specialized meat handling centers.
- Use gloves when cutting and skinning animals.
- Do not use common kitchen tools for such actions.
- Maintain the least contact with the animal’s organs.
- If suspicion is confirmed by symptoms or by meat analysis, it is recommended not to consume it.
There is no easily accessible information about it in the USA, nor do we find documented cases. We hope this information is useful and see your next hunt !!!
Remember that your safety comes first.
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