Just like
mad cow disease, only they haven't quite proven it exists.
The USDA recently completed a study that shows this previously unrecognized form of the disease in swine may be infecting humans, yikes.
As far back as 1978, Dr. Masuo Doi, a vet with the Food Safety and Quality Service, observed signs of a mysterious central nervous system disorder in some young hogs that had arrived at the Tobin Packing Plant in Albany, N.Y., from several Midwestern states. For 15 months, he studied a hundred of them, observing:
"Excitable or nervous temperament to external stimuli such as touch to the skin, handling and menacing approach to the animals is a common characteristic sign among those affected with the disease." - symptoms similar to those of mad cow disease, or bovine spongiform encephalapathy.
So, the government fought about it for years and years ("it's not mad pig disease!" "the fuck it's not!"), and who knows what nasty shit they fed us in the meantime.
What happens if you eat diseased pig? Hmm, well, two epidemiological studies found pork to be a dietary risk factor in Creutzfeldt-Jakob disease, which I don't know what it is, but who wants it? Of course the government is fighting over whether infected pork can be proven to really give you this disease, yap yap yap, and the matter still hasn't been resolved.
But you don't have to take MY word for it!
If you like reading about wicked nasty pigs that can make you die and stuff, read:
http://eagle.westnet.gr/~aesclep/madpig2.htm
http://data.free.de/gen.free.de/gentech/1997/8.96-5.97/msg00260.html