A beef cow from a herd in Alabama tested positive for bovine spongiform encephalopathy (BSE) or mad cow disease, but the origin of the animal could not be confirmed by the U.S. Department of Agriculture. The department will try to trace where the cow was born and find other members of its birth herd, believed to have eaten the same food. Previously, two infected cows have been found. The first case was discovered in the state of Washington, in December 2003, the animal's brain being tested after the carcass had been sold for hamburgers. The second infected animal was discovered last June, in a cow born and raised in Texas. The department waited seven month before testing to confirm the infection. So far, no person in the United States has the form of the brain wasting disease. Canada and the U.S. had restrictions in place to prevent contaminated imports since 2003, after the disease was found in North America, in Canada and in the U.S. Contaminated feed is believed to be the most likely cause of infection, thing which led the U.S. to ban the use of protein from ruminants, such as cattle, deer, sheep, elk and goats in 1997. Both countries require special devices to remove risk materials from carcasses, such as brains, spinal cords and other nervous tissues most at risk of carrying the infective agent.