If anyone ever needed evidence to counter creationist claims that the design of life was perfect, prion proteins are that. Their existence is the equivalent of Internet Explorer bug exploits and shows that the mechanics of life really aren't as elegant and perfect as once thought.
Prions work by...well, they don't actually do anything at all, except exist. Unlike bacteria, which are life forms of their own, and viruses, which hijack the machinery of cells to reproduce, prion proteins are just proteins, created wrongly by their cells because of an error in protein synthesis. Their existence is by chance alone, not evolution; in the countless reactions and replications of proteins that happen in living things, eventually a protein is created that is just the right composition and shape to do really nasty stuff.
And that nasty stuff is to get stuck in the machinery of cells and get created in large amounts. Its not reproduction as viruses do, its just a mistake that happens in just such a precise way that it cascades. Most infectious prions damage the creatures they infect by damaging - and eventually destroying - brain matter.
And because they're not alive, they're impossible to kill and very hard to destroy. Normal sterilisation techniques don't work - gamma radiation, high temperature, chemicals. None can be sure of destroying every prion on or in an infected item, including surgical instruments and transfused blood.
But if it's any consolation, if these prions were really so unstoppable complex life wouldn't have been possible. Because they kill their host, they don't pass on like normal pathogens. Ones like BSE and scrapie arise from human idiocy and greed - namely the practice of feeding cattle the dead parts of other cattle, and getting cheap cattle from places where prion diseases are rife, like Africa. Prions are probably also a reason cannibalism isn't common in the higher animal species - including us.
So if you're scared that these things might be multiplying in your pancreas right now, don't be - they're very rare and don't effect all people anyway. But you know who to blame for your fear - the greedy farmers who wouldn't even pay for a little extra animal feed.
