Mad Lambs: Why Are These Sheep Headed to Slaughter?

The U.S. Department of Agriculture is not taking any chances that Europe's mad-cow disease will get a hoofhold here. This week the USDA will destroy 360 Vermont sheep, even though the agency does not know for sure that the animals have the disease--and may not know for two years. The sheep were imported from Europe in 1996. In 1998 the USDA placed them in quarantine after learning they may have consumed contaminated feed. Last July four of the animals developed transmissible spongiform encephalopathy, a class of diseases that includes mad cow. Within days, the USDA issued an emergency order to acquire the animals. But the owners went to court, claiming, correctly, that the USDA could not distinguish between mad cow and scrapie, a threat to sheep but not humans. A federal appeals court ruled against the shepherds this month, and last week the flocks were seized. Why does it take so long to determine if they have been infected? The only way to confirm TSE is either by symptoms or by autopsy of the animals' brains. The problem is that the agent responsible for TSE is still unknown. The best way to learn whether an animal is infected is to inoculate brain material into a healthy lab mouse, then monitor the mouse to see if it gets sick, a process that can drag on interminably for all concerned.

--By Dick Thompson/Washington. With reporting by Alice Park and Elaine Rivera/New York