BSE, or Jakob Kreuzfeld (Not sure on spelling, and it may not even be the right name....I'll play the odds though.) disease is a degenerative neurological disorder, yes, often made apparent by symptoms of aggressiveness (This "Mad" Cow disease) and disorientation. However,this is a play on words, more specifically Mad take as insane.
In short, grow a sense of humor, it's a joke.