The danger of mad cow disease may have faded from memory, but experts caution that similar pathogens in animals pose a potential threat to human health and the economy.
Although rare, sporadic cases of mad cow disease still occur, and similar pathogens lurk in animals across the globe.
Chronic wasting disease (CWD), colloquially referred to as “zombie deer disease,” affects animals such as deer, elk, reindeer, and moose. It has been detected in numerous American states, Canadian provinces, and several countries including South Korea, Finland, Norway, and Sweden. In some U.S. counties, over 80% of deer are infected.
Experts are concerned that this progressive, fatal illness could potentially spill over to humans in a manner similar to mad cow disease. The resulting economic and public health crisis could be worse, as CWD can affect both farmed and free-range animals, making total control impossible.
Epidemiologist Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP), has launched an international effort to prepare for a possible spill over to humans or farm animals humans might consume. The venture is funded by the Minnesota legislature and is composed of 67 experts from seven countries, including representatives from federal agencies like the U.S. Centers for Disease Control and Prevention and National Institutes of Health, universities, and tribal communities. The group will address topics like public health and animal surveillance, diagnostics, lab capacity, and planning and response for the disease.
Chronic wasting disease is an infectious condition that affects deer, elk, reindeer, and moose. Animals can become infected through contact with the feces, saliva, blood, or urine of infected animals, or through contaminated soil, food, or water. Environments contaminated with the disease are believed to remain infectious for years, if not decades. The symptoms in animals include drastic weight loss (wasting), stumbling, listlessness, and other neurologic symptoms.
No human cases of chronic wasting disease have yet been reported. However, similar diseases have been reported in humans.
Chronic wasting disease is caused by infectious proteins called prions, which can incubate in an animal or person for decades before leading to rapid deterioration and death about a year after the onset of symptoms.
The consumption of infected deer meat is a potential concern, as infectious proteins are found in the brain and peripheral nerves of their muscles, which could pose a risk to human health. Experts urge caution when hunting in areas where CWD has been detected in deer, recommending testing the meat and avoiding consumption if it tests positive for the disease.
There are various prion diseases, some of which affect animals, while others affect humans. These diseases include Creutzfeldt-Jakob disease (CJD), mad cow disease (BSE), scrapie, transmissible mink encephalopathy, feline spongiform encephalopathy, and ungulate spongiform encephalopathy, among others.
Symptoms of human prion diseases include rapid onset dementia, difficulty walking, involuntary muscle movements, confusion, mood changes, hallucinations, muscle stiffness, impaired memory, depression, fatigue, difficulty speaking, and eventual death.
Prion diseases can be passed among humans in rare cases, such as through the transplant of corneas, blood transfusions, and via contaminated medical equipment.
There is a concern that if chronic wasting disease spilled over into humans, it might transmit more easily, potentially leading to fecal-oral transmission and possible endemicity in humans.
