Because scientists knew infected feed was the likely cause of the problem, they recommended a ban on feeding meat and bone meal to cattle.

Officials said it was unlikely that these two Canadian-born cows had eaten the same infected feed.

This wasn't what they came into farming for, filling out forms, being criticized in the media for giving cattle infected feed.

It was Susan who'd never used infected feed, never had a sick cow.

It probably is not transmitted through infected feed, as is the case for BSE.

The disease was eventually traced to infected feed.

Much to the relief of the U.S.D.A., the cow turned out to be from a Canadian herd; it probably ate infected feed in Alberta when it was a calf.

Worldwide testing shows that it can take from 20 months to 15 years for an animal to exhibit infectious prions in its brain stem after eating infected feed.

European Union officials have ascribed the spread of the disease in Switzerland to infected feed from Britain and have shown less alarm than the Swiss themselves.