The 1997 book "Mad Cow U.S.A.," by Sheldon Rampton and John C. Stauber, made the case that the disease could enter the United States from Europe in contaminated feed. Over the years, the U.S.Department of Agriculture has consistently stated that it used the "gold standard" of testing, and there is no evidence of mad cow in the beef supply. Without admitting any error, the USDA has rapidly increased the number of cattle it tests annually. It went from testing 219 in 1997 (the year it banned the feeding of ruminants to other ruminants) to 20,526 last year. By contrast, European countries tested 10 million animals last year.
New York Times December 28, 2003