Encephalopathy: Could Chronic Wasting Disease in Deer Soon Become a Zoonosis?

Chronic wasting disease is currently spreading in the United States and Canada. American researchers estimate that meat from infected animals (deer, elk, moose, etc.) could pose a risk of infection to humans in the coming years. Hunters, who are particularly at risk, are advised not to handle or consume deer or elk meat in regions where the disease has been reported. Studies are underway to determine whether this prion disease could evolve into a zoonosis.   Although chronic wasting disease is not, in principle , transmissible to humans, it is highly contagious among deer, elk, moose, and related animals, which can transmit infectious prion proteins through saliva, blood, urine, and feces, via direct or indirect contact in the environment. Chronic Wasting Disease is endemic in the United States, where 24 states are now affected. In Canada, approximately 100 domestic herds have been infected since 1996, across three provinces (Saskatchewan, Alberta, and Quebec). Norway, Finland, and South Korea are also affected. As the number of cases in wild and domestic deer continues to rise, despite the eradication and culling measures that have been implemented, researchers are closely monitoring the disease’s progression. Although there is currently no evidence of transmission of the disease to humans, this possibility cannot be ruled out. According to animal studies, certain monkeys—specifically macaques—have become infected after eating meat or handling tissues from infected deer. These studies raise concerns about a potential risk to human health. At this time, there is no direct scientific evidence of transmission of the infectious agent to humans, and no human cases have been reported, but this may simply be a matter of time. Recently, the CDC , the U.S. agency responsible for disease control and prevention, released some rather alarming figures: as of January 31, 2019, 251 U.S. counties had reported a case of chronic wasting disease in wild deer. Canadian and U.S. health authorities advise residents of regions where chronic wasting disease has been confirmed to avoid meat consumption involving venison or elk meat. Similarly, hunters are encouraged to take precautions when handling carcasses and to have the animals tested before consuming the meat or tanning the hides. This progressive and fatal disease is a prion disease, like bovine spongiform encephalopathy, scrapie, and Creutzfeldt-Jakob disease . It primarily affects the spinal cord and brain of deer and can remain asymptomatic for several years after infection. Characterized by a decline in overall health, weight loss, excessive salivation, coordination problems, and altered behavior, it is often referred to as “zombie deer disease.” Although the clinical course of the disease is slow, the outcome is always fatal, as there is neither a treatment nor a vaccine.