By the evening edition.
Chronic wasting disease (CWD) or “zombie deer”, which affects cervids (deer, reindeer, etc.), is spreading mainly in the United States and Canada. If some scientists were worried about possible transmission to humans, a latest study published in June 2024 is more reassuring.
For around ten years, a strange disease has affected deer, elk and reindeer in North American forests. Glazed eyes, stumbling, aggression… It is called chronic wasting disease (CWD) or “zombie deer” due to the symptoms that affect deer.
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Observed for the first time in 1967, in Colorado, it is a fatal degenerative disease of the nervous system of deer, in the same family as mad cow disease. It is caused by a prion, which is derived from a protein naturally present in the body of mammals, which can fold and change shape causing many behavioral disorders in animals.
An increasing spread in the United States
Its particularity lies in its slow evolution. “The disease will take months to develop before we can detect itexplains Sylvain Larrat, veterinarian specializing in wildlife. Throughout this period, the animal will be able to spread abnormal prions (infectious proteins, editor’s note) into its environment, which can contaminate other deer. »
Since CWD is fatal and is similar to Creutzfeldt-Jakob (the human equivalent of mad cow disease), American scientists are concerned about its increasing spread in recent years. As of December 2023, experts reported that the disease had been identified in 800 samples of deer, elk and elk in the western US state of Wyoming, as reported Reporterre . “A slow disaster”, which affects 31 American states, according to experts, but also Europe. Since in 2016, CWD was detected in reindeer and elk in Norway, then in Sweden in 2019.
“But it never went beyond Scandinaviaindicates Sylvain Larrat. The disease expands geographically from an initial infected area, but it does not happen quickly at all. » According to the veterinarian, the spread could accelerate if humans transported contaminated goods (game trade, etc.). “We can be reassured in France, because there are no close cases, the regulations prevent legal import and we already have a wildlife surveillance system (SAGIR). »
Transmission “impossible” or “extremely rare”
Today, no case of MDC has been diagnosed in humans, as recalled Squeeze Lemon . A 2022 study showed that an MDC mutation could develop in humanized mice. “Our results strongly suggest that CWD should be considered a real public health risk”, indicated the researchers. Especially since according to the Alliance for Public Wildlife (nature conservation agency in the United States), in 2017, between 7,000 and 15,000 animals infected with CWD were consumed each year by humans.
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Comments nuanced in June 2024 by the National Institutes of Health, a United States government institution which deals with medical and biomedical research. Researchers exposed human brain cells to prions damaged by the disease for 180 days. No spread has been noted. “Overall, the failure of CWD diffusion in brain organoids supports the existence of a strong species barrier to transmission of CWD prions to humans”, comment the scientists. In other words, according to them, “It is extremely unlikely that humans will contract prion disease due to inadvertent consumption of meat from CWD-infected deer. »
Transmission to humans would be “either impossible or extremely rare”according to Sylvain Larrat. “Among hunters in North America in highly contaminated areas, there is no epidemic. At present, the disease seems less transmissible than mad cow disease, that’s for sure. »
