In the 1950s, screwworms caused annual losses to American meat and dairy supplies that were projected at above $200 million.

To face competition from American meat, even more stockyards will need better grain for feed.

Domestic and foreign purchases of American meat fell by half.

The quotas for American meat and poultry exports to these countries will be phased out over the next 15 to 20 years.

American meat has already begun arriving in China under a related trade deal.

The real threat is economic: the presence of the virus would lead to an automatic ban on exporting American meat, a $50 billion annual business.

They were tested using more readily available conventional American meats.

Throughout the world, people in poor countries tend to buy more American meat and grain as they become more affluent.

It recalls last year's European ban on American meat from cattle treated with hormones.

In particular, low prices are seen as an incentive for countries like Japan to develop a taste for American meat.