Shepherd's warning

摘要

Modern food-production methods move animals about a lot before they wind up on dinner tables. So, as the British government found out in the 2001 outbreak of foot and mouth disease (FMD) among cattle, tracing the origins of an epidemic can be tough. To make disease control easier, the European Union decided that all sheep, which also get fmd, should have identity cards in the form of electronic ear tags. That way they can be monitored, just as supermarkets use radio-frequency identification microchips in packaging to track their stock. Tracing infected animals back to their home farms is crucial for disease control.rnIt seems a good idea. It should also make controlling scrapie, a nasty sheep disease that can remain undetected for years before symptoms show, much easier. America started using the same technology in 2001 and stepped up an animal-testing programme to wipe out scrapie. The disease turned out to be more widespread than was first thought but, since 2005, the number of flocks testing positive has fallen by about 77%.