BSE is an infectious disease believed to be due to a misfolded protein, known as a prion.[3][6]Cattle are believed to have been infected from being fed meat and bone meal (MBM) that contained the remains of other cattle who spontaneously developed the disease or scrapie-infected sheep products.[3] The outbreak increased throughout the United Kingdom due to the practice of feeding meat-and-bone meal to young calves of dairy cows.[3][8]
Prions replicate by causing other normally folded proteins of the same type to take on their misfolded shape, which then go on to do the same, leading to an exponential chain reaction. Eventually, the prions aggregate into an alpha helical, beta pleated sheet, which is thought to be toxic to brain cells.[citation needed]
The agent is not destroyed even if the beef or material containing it is cooked or heat-treated under normal conditions and pressures.[15] Transmission can occur when healthy animals come in contact with tainted tissues from others with the disease. In the brain, the agent causes native cellular prion protein to deform into the misfolded state, which then goes on to deform further prion protein in an exponential cascade. This results in protein aggregates, which then form dense plaque fibers. Brain cells begin to die off in massive numbers, eventually leading to the microscopic appearance of "holes" in the brain, degeneration of physical and mental abilities, and ultimately death.[citation needed]
The British Government enquiry took the view that the cause was not scrapie, as had originally been postulated, but was some event in the 1970s that could not be identified.[16]
https://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy
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