Prions - tiny, non-living, infectious particles that they are - are admirable for their ability to avoid inactivation through means normally used on viruses and bacteria. The USDA defends1 that prions are "extremely resistant to heat, ultraviolet light, ionizing radiation, normal sterilization processes, and common disinfectants". So leaving your burger on the grill another minute or two isn't going to give peace of mind. Nor, for that matter, will spraying your ground beef with Lysol, which, as a last ditch effort, has more to recommend it than you might think.2 Were my body to fail me, I might choose that it succumb to the toxicities of prion-inactivation attempts, than to the wicked spongiform encephalopathies these anti-critters are known to induce.
Mad cow disease, or bovine spongiform encephalopathy (BSE), results in, well, a cow with a brain full of holes. Sheep have a form called scrapie that causes an itch so profound it compels them to scratch (thus scrapie) their wool away. Humans have forms that lead to loss of bodily functions, dementia, and ultimately death, since there is no known cure.
The FDA says that the human form "is believed to be caused by eating contaminated beef products". Cows get it by eating other cows, i.e. by eating feed that contains BSE-contaminated beef products, in other words, by forced cannibalism. Just about all of the beef you have eaten and will eat, unless labeled otherwise (or you raise your own), came from a cow cannibal. Oddly, a cow is an herbivore, and lacks the ability to chew or digest meat.
The US found its first mad cow in December, 2003. Before that the USDA tested about 20,000 cattle/yr for BSE, afterwards they upped it to 200,000/yr. There are about 100,000,000 cattle in the US inventory. Hm, 200,000 divided by 100,000,000 - is that 2% tested? I don't know about you, but that isn't enough to assure me of a mad-cow-free food supply. Japan tests 100% of their cattle, no wonder they've banned ours.
I like beef. I like a nice grilled burger, a sizzling steak, a tender beef bourguignon. Not a lot, just once in a while. Is it too much to ask that the meat I buy for such indulgencies come from a cow that wasn't forced to eat another cow? And if not that, from a cow whose cannibalistic flesh was inspected, and did pass, a prion test? Is that too much to ask?
1 Why are they defensive? Because we, however frivolously, expect big government agencies like the USDA to assure us that our meats have been cleansed of nasty crap.
2 I'm not recommending it.