Mad cow disease aka BSE can't be contracted eating muscle cuts of beef, only brain or spinal products if the animal were contaminated. It can't be renderend inert by cooking to a higher temperature as it is a radical protein and is not bacteria or viral.
There has been much damage to the livestock industry in the US by media hype when generally they were only interested with headlines.
The US livestock industry is the safest in the world. There has only been one reported case in all the millions and millions of animals raised. The probability of getting struck by lightening while standing on your head is much greater than contracting BSE from US beef.
Dr. Robert Hogan