It is transmissible to other cows through the factory farming practice of rendering, or feeding the ground up remains of dead cows to other cows.
People get the disease by eating tainted meat.
BSE takes a long time to become noticeable in a cow, so by the time it's ready for slaughter, it could be BSE positive and no one would know it. The human version of BSE, called Creutzfeldt-Jakob disease, or CJD, kills by creating millions of tiny, spongy holes in a person's brain. The authors also have many things to say about an American meat industry seemingly more interested in public relations and suppressing critics than in cutting back, or stopping, the practice of rendering. To get the undiluted facts instead of diluted nonsense on this urgent issue, this is a Must Read of a book.