Is Chronic Wasting Disease in Deer and Elk a Threat to Humans?

Chronic wasting disease (CWD) in deer and elk (cervids) has been rapidly spreading across North America and has also been found in Korea and Europe. CWD is an infectious and fatal neurodegenerative disease, also known as transmissible spongiform encephalopathies, caused by prions. Prions are misfolded infectious proteins that reside in central nervous system tissues including the brain, spinal cord, and eyes. Transmission of these prions only occurs through handling or eating the affected nervous system tissues. It cannot be spread from person-to-person by touch or in the air. Scrapie and bovine spongiform encephalopathy (BSE) are the most well-known of the prion diseases. 

BSE or mad cow disease was first reported in 1996 by the UK and has been strongly linked through epidemiology and laboratory testing as the causal agent of variant Creutzfeldt-Jakob disease (vCJD) in humans. There have been 26 cases of BSE in North America reported by CDC surveillance from 1993 to 2018. Since vCJD was first reported in 1996, there have only been 231 cases worldwide with three of them related to blood transfusions. 

Because chronic wasting disease is spreading rapidly and there is a significant potential for human exposure to affected animals, the ability of the disease to infect humans has become a much-debated issue. Barria et al. analyzed prions from tissue collected from elk, white-tailed deer, and reindeer in North America and used a cell-free seeded protein microfolding assay to determine if they can convert the human prion protein to a disease-associated form.  Their data showed that the prions could be converted; however, there is variability in the efficiency of conversion related to polymorphism in both the cervid and human prion protein genes. It's clear that further research needs to be done to more definitively determine if humans can develop this disease.