http://en.wikipedia.org/wiki/Mad_cow_disease
I was aware of a bovine problem similar to BSE in 1980s when a local farmer bought steer calves at our cattle market in UK. At aged 9months the freisians seemed to have arthritus (vets prognosis). Some of them keeled over and could not remain standing. Within the month they were 'put down'.
Although the steers were purchased in UK it was later discovered that these calves had been imported from Holland for the British markets.
When the disease was full blown in UK and stocks were shot & burned in 2000 approx, it was reported in the Farmers Weekly that the European stock were only immunised!
It was a devastating blow to UK farmers to lose their stock and livlihoods. They have yet to recover from the experience.
Please Google Farmers Weekly or Ministry of Agriculture for more factual details.