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On December 23, 2003, the U.S. Department of Agriculture (USDA) announced a presumptive diagnosis of bovine spongiform encephalopathy (BSE, or "mad cow" disease) in an adult Holstein cow from Washington State. Samples were taken from the cow on December 9 as part of USDA's BSE surveillance program. The BSE diagnosis was made on December 22 and 23 by histopathology and immunohistochemical testing at the National Veterinary Services Laboratory, Ames, Iowa. The diagnosis was confirmed by an international reference laboratory in Weybridge, England, on December 25. Preliminary trace-back based on an ear-tag identification number suggests that the BSE-infected cow was imported into the United States from Canada in August 2001. What is bovine spongiform encephalopathy (mad cow disease)? Bovine spongiform encephalopathy (BSE) is a progressive neurological disorder of cattle that results from infection by an unconventional transmissible agent.
The BSE epidemic in the United Kingdom peaked in January 1993 at almost 1,000 new cases per week. The outbreak may have resulted from the feeding of scrapie-containing sheep meat-and-bone meal to cattle. There is strong evidence and general agreement that the outbreak was amplified by feeding rendered bovine meat-and-bone meal to young calves.
 Is BSE occurring in the United States? According to the Animal and Plant Health Inspection Service of the U.S. Department of Agriculture, BSE has not been detected in the United States, despite active surveillance efforts since May 1990. As of October 31, 2000, 11,700 bovine brain specimens have been examined by an ongoing BSE surveillance system in the United States, and no evidence of BSE was seen. Regularly updated numbers of bovine brain samples tested as part of the nationwide BSE surveillance program are provided by the USDA. Further, to prevent BSE from entering the United States, severe restrictions were placed on the importation of live ruminants and certain ruminant products from countries where BSE was known to exist. These restrictions were later extended to include importation of ruminants and certain ruminant products from all European countries. Is BSE a foodborne hazard in the United States? As indicated above, BSE has not been shown to exist in the United States. Thus, it is extremely unlikely that BSE would be a foodborne hazard in this country. Because the use of ruminant tissue in feed was probably a necessary factor responsible for the BSE outbreak in the United Kingdom and because of the current evidence for possible transmission of BSE to humans, the U.S. Food and Drug Administration instituted a ruminant feed ban in June 1997 that became fully effective as of October 1997. Is there any monitoring of the incidence of Creutzfeldt-Jakob disease in the United States? Yes. The possibility that BSE can spread to humans has focused increased attention on the desirability of national Creutzfeldt-Jakob disease (CJD) surveillance.
The Centers for Disease Control and Prevention (CDC) monitors the trends and current incidence of CJD in the United States by analyzing death certificate information from U.S. multiple cause-of-death data, compiled by the National Center for Health Statistics, CDC. A summary of these data was published in the Journal of the American Medical Association on November 8, 2000 (Volume 284, No. 18, pp. 2322-3; available at What is the new variant form of CJD that the experts in the United Kingdom believe might be related to the BSE outbreak in cattle?
Is there evidence directly linking this newly recognized variant of CJD to BSE exposure? There is strong epidemiologic and laboratory evidence for a causal association between new variant CJD and BSE. The absence of confirmed cases of new variant CJD in other geographic areas free of BSE supports a causal association. In addition, the interval between the most likely period for the initial extended exposure of the population to potentially BSE-contaminated food (1984-1986) and onset of initial new variant CJD cases (1994-1996) is consistent with known incubation periods for CJD. Interim results of an ongoing experimental study involving inoculation of a panel of inbred mice with the agents causing BSE and new variant CJD substantially increased the strength of the scientific evidence for a causal association between new variant CJD and BSE. Two additional groups of inbred mice and a group of cross-bred mice inoculated with brain homogenates from new variant CJD cases were also reported to have had latency periods and lesion profiles consistent with the BSE pattern. Bovine spongiform encephalopathy (Mad Cow Disease) Is BSE a foodborne hazard for travelers to Europe? The current risk for infection with the BSE agent among travelers to Europe is extremely small, if it exists at all. Source:http://www.cdc.gov/ncidod/dvrd/bse/
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Through the end of November 2003, more than 183,000 cases of BSE were confirmed in the United Kingdom alone in more than 35,000 herds. Regularly updated numbers of reported BSE cases, by country, are available on the website of the 
In contrast to the classic form of CJD, the new variant form in the United Kingdom predominantly affects younger persons (median age at death: 27.5 years as of October 2000), has atypical clinical features, with prominent psychiatric or sensory symptoms at the time of clinical presentation and delayed onset of neurologic abnormalities, including ataxia within weeks or months, dementia and myoclonus late in the illness, a duration of illness of at least 6 months, and a diffusely abnormal non-diagnostic electroencephalogram.