Brain-Eating Crows May Help Spread Prion Diseases

Prions—the infectious proteins that cause illnesses such as mad cow disease, scrapie, chronic wasting disease and Creutzfeldt-Jakob disease—can pass through the digestive systems of crows, new research published in PLoS One finds. The crows are unharmed during the process, and scientists suspect that the birds may play a part in transmitting prion diseases from one location to another, one animal (or, eventually, human) to the next.

To make this discovery, the researchers fed crows prion-infected mice brains. When the crows excreted the digested brains around four hours later, the prions emerged without any damage. The researchers then injected healthy mice with prions recovered from the crows’ droppings, and those mice showed signs of prion disease.

Crows are likely not alone in their passive role as prion transmitters. Other studies suggest that insects, poultry and other scavengers may passively carry prions without showing any disease symptoms themselves. But this study is the first to demonstrate that those consumed prions can retain their ability to cause disease even after being digested. When it comes to prion diseases, Poe may have been right to dub the “grim, ungainly, ghastly, gaunt” raven an ominous “thing of evil” tossed by tempest onto horror-haunted homes.

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Rachel Nuwer is a freelance science writer based in Brooklyn.