The main feature of both mad cow disease and nvCJD is the progressive destruction of brain cells, inevitably leading to total disability and death. TSEs can afflict sheep, deer, elk, cows, mink, cats, squirrels, monkeys, humans and other species. CJD strikes one in a million people almost all of whom are older than 55. No one knows the latency period for nvCJD in humans, but it is thought to be around 10 years. Because of this uncertainty, no one is sure how many people in England already have the disease but are not yet showing symptoms.
Cows are, by nature, vegetarians.
But modern agricultural techniques changed that. Cows that died mysteriously were sent to rendering plants where they were boiled down and ground up into the consistency of brown sugar, and eventually added to cattle feed. Ten new cases of nvCJD were reported in England in 1999, bringing the total to 48. It has been more than 10 years since government authorities banned the use of the particular parts of cows thought to transmit mad cow disease. The appearance of new cases of nvCJD in 1999 implies either that the latency period for the disease is longer than 10 years, or that infected meat was not effectively eliminated from the food chain when government authorities said it was, or both.