Mad Cow Disease -- which changed its name from Bovine spongiform encephalopathy (BSE) when it got famous in the late 1990's -- is a fatal neurodegenerative disease in cattle, spread by the host consuming animal by-products infected by this protein mutation. The disease is zoonotic -- meaning it can be transmitted to humans (and vice versa) -- so this forced cannibalism resulted in the deaths of over 150 Europeans through 2004 who had consumed tainted beef. While only five BSE-infected cattle were identified in the U.S. through 2005 (due to their largely soy diet), the panic was enough to cause widespread bans on U.S. beef.