Tracking BSE

Mad cow, or bovine spongiform encephalopathy (BSE), is slowly progressive, degenerative, fatal disease affecting the central nervous system of adult cattle. For 16 years, the United States Department of Agriculture (USDA) has conducted aggressive surveillance of the highest risk cattle going to slaughter in the United States. The following lists a breakdown of the nation's three confirmed cases.

December 2003: USDA's surveillance program identified the nation's first BSE case in a dairy cow in Washington. The cow, brought in from Canada, prompted USDA and the Food and Drug Administration to activate their BSE Emergency Response Plans. The confirmation kicked off a strenuous two-year testing period by USDA of random cow brains in high-risk populations. That program, which boasts analysis of more than 700,000 animals, currently is being reviewed for a possible scale-back.

November 2004: USDA's surveillance program identified the second BSE case in the United States. Results from this animal initially were inconclusive in screening tests but negative in confirmatory immunohistochemical tests. After conducting an additional confirmatory test, USDA reported the results positive. USDA confirms that the cow was born before the U.S. instituted its ban on the use of most mammalian protein in feed for ruminant animals believed to be the most critical protective measure in preventing the spread of BSE among cattle.

March 2006: USDA reported a positive result on a Western blot confirmatory test conducted at USDA laboratories in Ames, Iowa, on samples from an animal that had previously tested inconclusive. The samples came from a non-ambulatory red crossbreed beef cow on an Alabama farm. Testing was conducted at University of Georgia diagnostic laboratories. The animal was buried on the farm and did not enter the animal or human food chain. Last month, USDA's Animal and Plant Health Inspection Service abandoned an epidemiological investigation into the cow's birth herd after officials conducted DNA testing on herds at 36 farms and five auction houses. Federal officials noted tracking difficulties because the animal was more than 10 years old and carried no tattoos, ear tags or branding marks.