Most researchers believe that Mad Cow Disease (formal name – bovine spongiform encephalopathy or BSE) is transmitted by an infectious agent called a prion.  Prions are mis-formed proteins which concentrate in nervous system tissues such as the brain, eyes, and spinal cord, although some recent research on similar diseases in other animals have found prions in blood and muscle tissue. The disease is spread among cattle when their feed contains infectious material from other cattle (or sheep, which get a similar disease called scrapie.) The human form of the disease is called variant Creutzfeldt-Jakob Disease (vCJD). It causes the brain and nervous system to waste away and get a spongy appearance.

Unlike bacteria or viruses, prions cannot be killed with heat or disinfection.  So there is nothing that consumers can do at home to deal with meat contaminated with BSE.