After 10 years of active surveillance, BSE has never been found in the United States. Formal regulations making the emergency ban permanent follow on Dec. 6, 1991.
Government officials theorize the disease spread because of infected meat and bone meal.
A Purina Mills plant in Gonzales, Texas mistakenly mixes meat and bone meal in a supplement for cattle feed. The supplement is loaded on a truck for delivery the next day to a feedyard. The feedyard stops feeding, Purina recalls the feed and FDA takes samples for analysis. The feedyard voluntarily holds 1,222 head of cattle. No quarantine was ever issued.