You'd have thought after the BSE scare over here that lessons would be learnt... why were they still feeding cows to other cows?
The FDA did put rules into place in 1997 to prevent this. Problem is, the disease has such a long period of time where it lies dormant, it could have caught it from one of the last cow based meals in 1997.
Personally, I'm not too worried about it. I will watch the news carefully to see if they find other cases of it. Then I might be a bit concerned. At least living here in the midwest though gives me a good choice in beef products, including some from farms I could drive to to ask questions about the feed the animals have gotten over the years.