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In this Article

• Mad cow disease facts, history, how it's spread, and link to variant Creutzfeldt-Jakob disease (vCJD)
• How many cases of mad cow disease have been identified in the U.S.?
• How many cases of mad cow disease have been identified in Canada?
• What are the different strains of mad cow disease?
• Can feed bans prevent the spread of mad cow disease?
• What is the prevalence of mad cow disease in the U.S. and Canada?
• Mad Cow Disease Index

There have been 3 cases of BSE identified in the United States. The following information provides descriptions of these three cases:

• On December 23, 2003, the U.S. Department of Agriculture (USDA) announced a presumptive diagnosis of the first known case of BSE in the United States. It was in an adult Holstein cow from Washington State. This diagnosis was confirmed by an international reference laboratory in Weybridge, England, on December 25. Trace-back based on an ear-tag identification number and subsequent genetic testing confirmed that the BSE-infected cow was imported into the United States from Canada in August 2001. Because the animal was non-ambulatory (a "downer cow") at slaughter, brain tissue samples were taken by USDA's Animal and Plant Health Inspection Service as part of its targeted surveillance for BSE. However the animal's condition was attributed to complications from calving. After the animal was examined by a USDA Food Safety and Inspection Service (FSIS) veterinary medical officer both before and after slaughter, the carcass was released for use as food for human consumption. During slaughter, the tissues considered to be at high risk for the transmission of the BSE agent were removed. On December 24, 2003, FSIS recalled beef from cattle slaughtered in the same plant on the same day as the BSE positive cow.
• On June 24, 2005, the USDA announced receipt of final results from The Veterinary Laboratories Agency in Weybridge, England, confirming BSE in a cow that had conflicting test results in 2004. This cow was from Texas, died at approximately 12 years of age, and represented the first endemic case of BSE in the United States.
• On March 15, 2006, the USDA announced the confirmation of BSE in a cow in Alabama. The case was identified in a non-ambulatory (downer) cow on a farm in Alabama. The animal was euthanized by a local veterinarian and buried on the farm. The age of the cow was estimated by examination of the dentition as 10-years-old. It had no ear tags or distinctive marks; the herd of origin could not be identified despite an intense investigation (see second featured item above and Alabama BSE Investigation, Final Epidemiology Report, May 2006 ). In August 2008, several ARS investigators reported that a rare, genetic abnormality that may persist within the cattle population "is considered to have caused" BSE in this atypical (H-type) BSE animal from Alabama.