Spontaneously Generated Mad Cow

From MarketWatch:

On Friday, the Department of Agriculture said that a sample from a cow that had been cleared last year as free of BSE -- more popularly known as mad-cow disease -- generated a possible positive under more intensive testing.

It's reassuring to be told, no less than eight times during Friday evening's news conference, that the meat from the suspect animal "did not get in the food or the feed chain." (US Dept. of Agriculture Secretary Mike Johanns, June 10). But from where did this alleged mad cow originate? What farm? What state? What country? And if it's true that cows develop the disease after being fed the flesh of other BSE-infected cows, then where and in what condition are all the other cows who received the same feed as this one? It's my understanding that the cow in question is "aged". That makes for a lot of years of feed. Following this path back further, from where did that BSE-infected feed originate? Am I to believe that this was a singular case of spontaneously generated bovine spongiform encephalopathy?