USDA estimates the prevalence of bovine spongiform encephalopathy in the United States is less than 1 case per million adult cattle, based on an adult cattle population in this country of 42 million animals.
USDA estimates the most likely number of cases present in the United States is between four and seven animals based on the enhanced surveillance effort since June 2004 and surveillance over the past five years.
USDA experts used two different methods, the BSurvE Prevalence B method and the Bayesian birth-cohort method, to analyze the prevalence of BSE based on all of the surveillance data.
The testing program is not part of U.S. food safety protections. The system of interlocking safeguards protects animal and public health. The most important safeguards are the removal of specified risk materials from the food supply, along with the Food and Drug Administration's 1997 ruminant-to-ruminant feed ban. Science indicates that the longer the FDA's feed ban is in place, the lower the prevalence of BSE will be in this country.
USDA will use the prevalence analysis, once it is peer-reviewed, and international standards set by the World Animal Health Organization, to design an ongoing BSE surveillance program for the United States. The data and analysis will also assist in making science-based policy and regulatory decisions related to the disease.
USDA's enhanced BSE surveillance program followed the detection of BSE in an imported animal in December 2003. The target population of cattle tested included those animals where the disease is most likely to be found if it is present: non ambulatory cattle, cattle exhibiting signs of central nervous disorders or any other signs that may be associated with BSE, including emaciation or injury and dead cattle. Samples were drawn from more than 5,000 locations across the United States, including slaughter plants, renderers, farms, public health laboratories, veterinary diagnostic laboratories and salvage slaughter facilities.