Mad Cow Disease 6/2010
What is Mad Cow Disease?
Mad Cow Disease is the commonly used name for Bovine Spongiform Encephalopathy (BSE), a slowly progressive, degenerative, fatal disease affecting the central nervous system of adult cattle. Since 1990, the U.S. Department of Agriculture (USDA) has conducted aggressive surveillance of the highest risk cattle going to slaughter in the United States.
What causes BSE?
The exact cause of BSE is not known but it is generally accepted by the scientific community that the likely cause is infectious forms of a type of protein, prions, normally found in animals. In cattle with BSE, these abnormal prions initially occur in the small intestines and tonsils, and are found in central nervous tissues, such as the brain and spinal cord, and other tissues of infected animals experiencing later stages of the disease.
Does BSE affect people?
There is a disease similar to BSE called Creutzfeldt-Jacob Disease (CJD) that is found in people. A variant form of CJD (vCJD) is believed to be caused by eating contaminated beef products from BSE-affected cattle. As of January 2006, there have been 155 confirmed and probable cases of vCJD worldwide among the hundreds of thousands of people that may have consumed BSE-contaminated beef products. The one reported case of vCJD in the United States was in a young woman who contracted the disease while residing in the UK and developed symptoms after moving to the U.S.
What measures are being taken to ensure food safety in the U.S. from BSE?
Following the identification in a Washington state dairy herd of a BSE-positive cow imported from Canada, USDA issued regulations containing safeguards to minimize risk for introduction of the BSE agent into the U.S. food supply. See USDA's website www.usda.gov for further information.
Similarly, the Food and Drug Administration (FDA) has prohibited the use of the cattle materials that carry the highest risk of BSE in human food, including dietary supplements, and in cosmetics. FDA's rule prohibits the use of the following cattle material in human food and cosmetics:
- cattle material from non-ambulatory, disabled cattle,
- cattle material from organs from cattle 30 months of age or older in which infectious prions are most likely to occur, and the tonsils and the distal ileum of the small intestine of cattle of all ages,
- cattle material from mechanically separated (MS) (beef), and
- cattle material from cattle that are not inspected and passed for human consumption
- The FDA has clarified that milk and milk products, hide and hide-derived products, and tallow derivatives are not considered prohibited cattle materials.
What is the risk for travelers?
The current risk of acquiring vCJD from eating beef (muscle meat) and beef products produced from cattle in countries with at least a possibly increased risk of BSE cannot be determined precisely. Nevertheless, in the UK, the current risk of acquiring vCJD from eating beef and beef products appears to be extremely small, perhaps about 1 case per 10 billion servings. In the other countries of the world, this current risk, if it exists at all, would not likely be any higher than that in the UK if BSE-related, public health control measures are being well implemented. Among many uncertainties affecting this determination are the incubation period between exposure to the infective agent and onset of illness, the sensitivities of each country's surveillance for BSE and vCJD, the compliance with and effectiveness of public health measures instituted in each country to prevent BSE contamination of human food, and details about cattle products from one country distributed and consumed elsewhere. Despite the exceedingly low risk, the US blood donor deferral criteria in effect as of September 2004 focus on the time (cumulatively 3 months or more) that a person lived in the UK from 1980 through 1996, whereas for the rest of Europe the criteria focus on the time (cumulatively 5 years or more) that a person lived in these countries from 1980 through the present.
To reduce any risk of acquiring vCJD from food, travelers to Europe or other areas with indigenous cases of BSE may consider either avoiding beef and beef products altogether or selecting beef or beef products, such as solid pieces of muscle meat (rather than brains or beef products like burgers and sausages), that might have a reduced opportunity for contamination with tissues that may harbor the BSE agent. These measures, however, should be taken with the knowledge of the very low risk of transmission as defined above. Milk and milk products from cows are not believed to pose any risk for transmitting the BSE agent.
How can I get more information?
For additional information about new, confirmed BSE cases, see the USDA website at www.usda.gov. The CDC, in collaboration with the American Association of Neuropathologists, established the National Prion Disease Pathology Surveillance Center. This pathology center provides free, state-of-the-art diagnostic services to U.S. physicians. It also helps to monitor the possible occurrence of emerging forms of prion diseases, such as vCJD, in the United States. For more information about the center visit its website at: http://www.cjdsurveillance.com.