BSE was first recognized in United Kingdom cattle in 1986. Since then, over 10 million cows have been infected and destroyed. BSE is caused by prions, which are abnormal variants of proteins that normally occur in cells such as brain cells or nerve cells. Normal prion proteins are produced in the nerve or brain cells but they are digested by protease enzymes. This aggregation of abnormal prion proteins is very similar to that of Alzheimer's disease.
Prions are sensitive to organic solvents, but can survive boiling and many disinfectants.
Since 1989, the USDA and the Food and Drug Administration have had stringent safeguards in place to prevent BSE from entering the country. According to current research, prions are not transmitted through skeletal muscle, milk, or connective tissue, but can be transmitted through bovine brain, eye, spinal cord, or nerve tissue. Prusiner, S.B. Prion diseases and the BSE crisis. S.B. The prion disease. CDC Emerg Infect Dis.