The U.S. Department of Agriculture announced that it has discovered four cases of mad cow disease in the United States. The most recent case of mad cow disease was discovered in a dairy cow in California.
U.S.D.A. labs were able to confirm that last case was atypical form of mad cow disease, which is a rare form. Agriculture officials say that it is not likely to be attributable to infected feed, which is the method in which mad cow diseases is transferred from cow to cow.
Officials added that the dairy cow did not enter the U.S. food supply. The U.S. instituted a mammalian feed ban in 1997 to protect animal health from diseases like mad cow.
“The beef and dairy in the American food supply is safe and USDA remains confident in the health of U.S. cattle,” said U.S. Agriculture Secretary Tom Vilsack. “The systems and safeguards in place to protect animal and human health worked as planned to identify this case quickly, and will ensure that it presents no risk to the food supply or to human health. USDA has no reason to believe that any other U.S. animals are currently affected, but we will remain vigilant and committed to the safeguards in place.”
Mad Cow Disease, also known asBSE (bovine spongiform encephalopathy), is a progressive neurological disorder of cattle that results from infection by an unusual transmissible agent called a prion. The nature of the transmissible agent is not well understood. Currently, the most accepted theory is that the agent is a modified form of a normal protein known as prion protein. For reasons that are not yet understood, the normal prion protein changes into a pathogenic (harmful) form that then damages the central nervous system of cattle.
Research indicates that the first probable infections of BSE in cows occurred during the 1970’s with two cases of BSE being identified in 1986. BSE possibly originated as a result of feeding cattle meat-and-bone meal that contained BSE-infected products from a spontaneously occurring case of BSE or scrapie-infected sheep products. Scrapie is a prion disease of sheep. There is strong evidence and general agreement that the outbreak was then amplified and spread throughout the United Kingdom cattle industry by feeding rendered, prion-infected, bovine meat-and-bone meal to young calves.
The BSE epizootic in the United Kingdom peaked in January 1993 at almost 1,000 new cases per week. Over the next 17 years, the annual numbers of BSE cases has dropped sharply; 14,562 cases in 1995, 1,443 in 2000, 225 in 2005 and 11 cases in 2010. Cumulatively, through the end of 2010, more than 184,500 cases of BSE had been confirmed in the United Kingdom alone in more than 35,000 herds.
There exists strong epidemiologic and laboratory evidence for a causal association between a new human prion disease called variant Creutzfeldt-Jakob disease (vCJD) that was first reported from the United Kingdom in 1996 and the BSE outbreak in cattle. The interval between the most likely period for the initial extended exposure of the population to potentially BSE-contaminated food (1984-1986) and the onset of initial variant CJD cases (1994-1996) is consistent with known incubation periods for the human forms of prion disease.
