Deadly disease in US forests
Hunters die after eating “zombie” deer meat
By Hedviga Nyarsik
April 26, 2024, 6:21 p.m
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An insidious disease is spreading in North America: it makes deer and deer look like zombies. Apathetic and drooling, the animals drag themselves through the forests until they die. There are now initial indications that the “zombie disease” can also affect people.
They stagger around listlessly, drooling and becoming thinner and thinner until they finally die: deer in North America suffer from a brain disease that is very reminiscent of BSE in cattle. Because of the symptoms, researchers and US media speak of the “zombie deer disease”. Scientifically, the fatal disease of the central nervous system is called Chronic Wasting Disease (CWD). So far, CWD has spread among deer, elk and reindeer. But now there are initial reports that the disease may also affect humans.
A team of doctors from the University of Texas describes in the Journal “Neurology” the case of two hunters who died after eating wild meat from a deer population affected by CWD. Accordingly, one of the men appeared confused and aggressive before his death. The symptoms developed within a short period of time and quickly worsened, according to the study.
According to the scientists, the man’s friend, also a member of the same hunting party, died at a later, unspecified time. The doctors write that he had previously developed similar symptoms to his hunting buddy. An autopsy ultimately revealed that this second patient died of Creutzfeldt-Jakob disease.
Brain takes on spongy perforated structure
Both Creutzfeldt-Jakob in humans and mad cow disease, as bovine spongiform encephalopathy (BSE) is colloquially known, and “zombie deer disease” (CWD) are among the so-called prion diseases. Prions are abnormal proteins, primarily in the brain, that have not folded properly. The type of folding is decisive for the function of proteins in the body. If this is wrong, the protein cannot do its job. Prions also have an insidious trick up their sleeves: they teach surrounding proteins to also fold incorrectly. In this way, the dysfunctional tissue continues to spread.
The spread of chronic wasting disease in the USA (as of February 2024)
(Photo: Bryan Richards, Emerging Disease Coordinator/National Wildlife Health Center)
The abnormally folded proteins are gradually deposited in the brain and cause the nerve cells to deteriorate. As the disease progresses, the affected brain takes on a spongy, perforated structure with thread-like, protein-containing deposits. The process resembles a type of accelerated dementia and cannot be stopped or cured.
Prion diseases are therefore always fatal. However, there is a serious difference between, for example, Creutzfeldt-Jakob and CWD in deer: animals infected with CWD also excrete the prions and can thus transmit them to other animals. Even before symptoms appear, saliva and other body fluids are contagious, according to the science journal “Spectrum” writes. In addition, the prions survive in the soil, on plants and other surfaces for years, meaning that animals can become infected at a later date.
Just a hint, no proof
Experts have long feared that CWD could also spread to humans. Since BSE we have known that people can become infected with animal prions and become ill as a result. It is even suspected that the new variant of the fatal Creutzfeldt-Jakob disease (now known as nvCJD) in humans is caused by the consumption of BSE-contaminated beef. In addition, it has already been proven that prions from CWD also affect predators, rodents and even monkeys.
Further investigations must show whether the two hunters actually died of CWD, as the research team writes. There are “indications of possible animal-human transmission,” says the study. But that is not reliable proof. Prion diseases are difficult to distinguish from one another and, in rare cases, can occur spontaneously without any external factors.
Nevertheless, the scientists warn that further research into the potential risks of consuming CWD-infected deer and the impact on public health is urgently needed. “A cluster of sporadic Creutzfeldt-Jakob cases may indicate possible cross-species prion transmission in regions with confirmed CWD deer populations. Surveillance and further research are essential to better understand this possible association.”