Prions

Prions are misfolded proteins that can pass on their misfolded shape to other normal proteins.

They characterize several fatal and transmissive neurodegenerative diseases in animals and humans.

For example, the bovine spongiform encephalopathy (BSE) or "mad cow disease" is caused by the mechanical seperation of beef. The seperated beef often contains the spinal cord which could carry the BSE prion, which could cause neurodegenerative diseases in humans.