Infectious prions get into the brain after people or animals eat food that is contaminated with them. Eventually, the proteins replicate to the point where they form plaques that can kill brain cells, and give the brain the “spongy” appearance that is characteristic of prion diseases (the diseases are formally called transmissible spongiform encephalopathies). Mad cow, scrapie and Creutzfeld-Jakob disease are all diseases of the brain that debilitate before they kill, and have no cure, or even many good treatment options beyond supportive care.
Prions are a distinct type of protein — they can self-replicate, said Adriano Aguzzi, professor of neuropathology at the University of Zurich,
When a prion comes into contact with a normal protein, it makes the normal protein alter its shape, and become a prion, too. Mad cow and scrapie affect cows and sheep, respectively, and Creutzfeld-Jakob disease (CJD) affects people.
Prions are also really hard to get rid of. The molecules are tightly bound, even boiling-water temperatures won’t break them up. Perhaps colloidal silver, zinc and copper might.
The prion mode of action is very different to bacteria and viruses as they are simply proteins, devoid of any genetic material. Once a misfolded prion enters a healthy person – potentially by eating infected food – it converts correctly-folded proteins into the disease-associated form.