Nearly all cases of infection in cattle have occurred in Britain, though in the last several months, infected animals have turned up in France, Germany, Portugal, Spain, Ireland, Switzerland, Belgium, Denmark, Italy, the Netherlands, Luxembourg and Liechtenstein. There have been 88 human cases in Britain, three in France and one in Ireland. Most have died. Yes, animals can be tested by examining their brains after they are slaughtered. Those tests were important in recognizing that the disease had crept into other countries in Europe.
Tests done in the United States show no evidence of mad cow disease.
The tests are not done on all cattle - just a sample that scientists say should be big enough to detect some cases if the disease exists here. In experiments, researchers have infected monkeys and mice with mad cow disease by feeding them brain tissue from infected cattle. That clued in the scientific community that there was a danger in Britain years before the government acknowledged it. In the United States, there have been reports of related diseases in mink and deer. These are not mad cow disease, said prion researcher Judd Aiken of the University of Wisconsin, Madison, although all have been fatal.