Factbox: Mad cow cases in U.S. and Canada

(Reuters) – The following are key dates in the spread of mad cow disease in Canada and the United States. The U.S. Department of Agriculture confirmed on Tuesday the fourth U.S. case of mad cow, formally known as bovine spongiform encephalopathy (BSE), in a dairy cow in central California. First discovered in Great Britain in 1986, mad cow disease destroys the brain of cattle and a similar fatal disease can affect people who eat meat from infected cattle, according to scientists. More than 150 people and 184,000 cows, mainly in Britain and Europe, have died from the diseases. …