Zombie Deer Disease: The Science Behind the Prion Infection That Turns Deer into Zombies

At first glance, seeing zombie deer staggering down the road may seem like something out of a Hollywood film, but wildlife officials and police in the US take this sighting very seriously. It's an indicator of chronic wasting disease (CWD), an epidemic currently spreading among deer, elk, and moose across the US that leaves infected animals drooling, lethargic, and wandering with blank stares; ultimately it leads to 100% fatal neurological disorders caused by abnormal proteins known as prions.

Prion diseases are rare, progressive, and ultimately fatal neurodegenerative conditions that impact both humans and members of the Cervidae (cervid family of hoofed mammals), including deer, moose, and antelope. 

They differ from viruses or bacteria in that they cause proteins to fold incorrectly, which leads them to form toxic plaques that eat away at brain cells until dementia, tremors, coordination issues and ultimately death occur. Although no one has yet been infected by chronic wasting disease (CWD), its danger remains for anyone hunting, raising, or eating deer and other cervids. CWD may spread throughout nature through dead animals carrying it and can even be spread via humans who handle or consume their meat.

There is no cure for prion diseases, and it can be extremely difficult to determine whether someone has it from just their symptoms alone. Furthermore, incubation periods for these diseases may last years before we know who was affected.

Scientists are issuing an alert, warning that zombie deer disease--also known as Chronic Wasting Disease or CWD--could spread to humans if its outbreak continues to expand. Already it has been found in hundreds of deer and moose in Yellowstone National Park alone as well as 800 samples across Wyoming.

The Sierra Club notes that although natural predators of deer, such as wolves and mountain lions, may be capable of killing CWD-infected deer quickly enough, they lack the means and have reservations against killing sick deer out of fear they'll contract CWD themselves.

Scientists warn that should CWD spread to humans, it will be very challenging to treat. There are no vaccines available and symptomatic treatments rarely work effectively in people. "The mad cow disease outbreak in Britain provided a reminder of what can go wrong when there's an accidental spillover of disease from livestock to humans; CWD shares many similarities. Therefore, now is the time to start taking this threat seriously."