Rise of the Zombie Deer

What's Going On?

A neurodegenerative disease known as "Zombie Deer Virus" has been spreading through deer, elk, and moose populations worldwide. The disease, more scientifically called Chronic Wasting Disease (CWD), is spread by pathogenic proteins called prions, which cause proteins in the brain cells of an infected animal to fold improperly and clump together — effectively turning the brain into "Swiss cheese". It's been reported in 24 US states so far, as well as Canada, Norway, Finland, and South Korea.

Tell Me More About the Zombie Part...

An infected deer can show no symptoms for months or years. But near the end of its life, it will become more and more emaciated, leave its herd, and stumble around in repetitive patterns, grinding its teeth in a dazed search for water to quench its insatiable thirst. There's no vicious craving for flesh, however — just a withered, dementia-ridden animal struggling toward its deathbed.

How Does It Spread?

Mostly through bodily fluids, but prions can survive for decades and take the long route to a new host. For example, prions in an infected deer's feces could bind to soil taken up by plants, spread to its leaves, then infect another deer that eats the leaves. So it's slowly increasing in the wild.

Could It Infect Humans?

According to many experts, it's probable... The disease works in a similar way to Mad Cow Disease, which did eventually infect humans. There haven't been any reported cases just yet — in 2005 around 200 people ate CWD-infected venison at an event in upstate New York, and a six year follow-up study found no adverse effects in anyone who consumed the meat.

But given the long life of prions, this isn't necessarily the end of the story. In a recent study CWD prions infected human cells in a petri dish. Scientists have also demonstrated that the disease can affect animals carrying human genes (like mice, squirrel monkeys, and macaques).

Fantastic! How Do I Avoid It?

Well, the best way to avoid it is by not eating deer or elk meat (or moose, if that's your thing), since cooking temperatures are not nearly high enough to kill prions. Authorities recommend that hunters get their animal tested before eating it, but the problem there is that current tests can only detect CWD at a certain stage, so it isn't a guarantee.

Where Has It Spread So Far?

In the US, 251 counties in 24 states have reported CWD among wild deer as of January. But researchers think the disease distribution is actually much wider — states vary a lot in their animal surveillance systems, and these pathogens are good at staying undercover. Read more here.

CWD in wild deer, by county | Source: CDC