Holes appear in victims' brains, then they become demented and die.
The prion can propagate itself by causing other proteins to twist into the same shape. Prions can be passed on by eating the flesh of another animal, and are resistant to cooking and digestion. A theory about how prions are formed suggests that organophosphate pesticides could be partly to blame. Two people have already died defending this theory, apparently at the hands of professional assassins working either for the British government or the chemical industry. So the theory needs to be taken seriously.