Over 150,000 cows have contracted the disease in the UK, and new cases are still occurring there. TSEs have been found in many mammals including humans, cows, sheep, cats, goats, deer, mink and certain zoo animals. Pigs are not immune. A TSE has been experimentally induced in pigs. TSEs get their technical name from the fact that the brains of infected animals usually develop sponge-like holes.
Mammals can contract TSEs by eating infected animals.
There is no known treatment or cure for TSEs, and they are invariably fatal. While the cause of TSEs has not been definitively established, the most widely accepted theory is that the infectious agent is an abnormal form of a naturally occurring protein, called a prion. Prion proteins normally occur on the surface of nerve cells and lymphocytes. When an abnormal prion comes in contact with a normal prion the normal one converts to the abnormal form. This can continue in a kind of domino effect.