Mad cow disease, a.k.a. bovine spongiform encephalopathy (BSE), is a chronic degenerative disease of the central nervous system in cattle, primarily spread by contaminated feed. The USDA Food Safety and Inspection Service (FSIS) says that there is “strong epidemiologic and laboratory data” linking human consumption of BSE-contaminated products to variant Creutzfeldt-Jakob Disease (vCJD), “a rare, degenerative, fatal brain disorder.” There’ve been a lot of panicked media reports about vCJD, but there have only been three documented cases in the United States as of June 2008, according to the Centers for Disease Control and Prevention (and a total of 208 worldwide).
Still, people continue to be cautious about eating parts of cows that may carry BSE. The FSIS considers these to be the brain, tonsils, eyes, spinal cord, certain parts of the nervous system, and part of the small intestine. There is sometimes confusion about bone marrow because it has been reported to potentially carry the infection, but Christopher Cox, a health communications specialist at the CDC, says that so far research has been inconclusive, thus “there is currently no evidence to suggest that consumption of bone marrow poses a greater risk than other beef products.”
People also wonder about oxtail because it seems like part of the spinal column, but the FSIS “does not believe that the oxtail, used primarily for soups, is a source of potential infectivity” because the area that the agency defines as the tail doesn’t contain the high-risk portions of the animal (the spinal cord and the dorsal root ganglia).
Cox says that the last confirmed case of BSE in the U.S. was in 2006, and that “there is no reason for people to exercise more caution than normal when consuming beef products.” As of October 26, 2009, new FDA regulations will ban the use of the tissues that have the highest risk of carrying the BSE-causing agent—the brains and spinal cords from cattle 30 months or older—in all animal feed. This strengthens the 1997 regulation that required cattle feed to be clear of certain nasty bits but not all. The hope is to avoid any cross-contamination between other animal feeds and that of cattle by keeping the high-risk items out entirely.