BSE

Epidemics in cattle are believed to have originated in sheep, in which the related prion disease scrapie is common. The tissues that contain most of the pathogenic molecules are those of the brain and the nervous system, although contagious amounts appear sometimes to be present in the blood. In the brain, these proteins form plaques, which lead to the appearance of holes in the brain, degeneration of mental abilities and death.

Following an epidemic of BSE in Britain, 152 people (as of 2003) acquired and died of a more or less identical disease. For many of them, direct evidence exists that they had consumed tainted beef, and so this is assumed to be how all the individuals contracted it. Disease incidence also appears to correlate with slaughtering practices that led to the contamination of hamburger and other beef with nervous system tissue. The human disease was designated variant Creutzfeldt-Jakob disease (or vCJD), after an extremely rare genetic prion disease whose symptoms it closely resembles.

Although the diseased herds were culled long ago, more people are diagnosed with vCJD each year. This implies that the disease has a long latency, as a result of which, public health experts do not know yet how many ultimately will contract it. The ease with which the disease can be contracted from beef therefore is not yet known.

Rodents injected with brain tissue from diseased cows begin to succumb to a similar neurological disorder in one or two years. With current tests, it is not possible to detect abnormal prions in the brains of all of these animals.

On February 17 2004 a research team headed by Salvatore Monaco reported in the Italian Proceedings of the National Academy of Sciences that a second strain of mad-cow disease had been detected. It is not known if this second strain is transmissible to humans.

The epidemic in British cattle

The BSE epidemic in the United Kingdom was discovered in 1986. BSE is thought to have spread by the practice of feeding cattle meat and bone meal, a high-protein substance obtained from the remnants of butchered animals. This practice allowed the accumulation of prions over many generations. The use of meat and bone meal as a protein supplement in cattle feed was widespread in Europe prior to about 1987. Soybean meal is the primary plant-based protein supplement fed to cattle. However, soybeans do not grow well in Europe, so cattle raisers throughout Europe turned to the less expensive animal byproduct feeds as an alternative.

BSE in North America

On December 23, 2003, the first case of BSE in the United States was found in a single Holstein cow in Washington State. Agriculture Secretary Ann Veneman called the discovery "a clear indication that our surveillance and detection program is working." However, the United States tested only 20,526 cows in 2003 out of the roughly 35 million slaughtered. Current tests reveal the presence of misshaped prions when they are abundant, but it is not known how far the disease must progress in an individual to transmit it to others. Therefore, it is possible that even among those cattle that are tested and classified as negative, a proportion nevertheless may be contagious. As a result, U.S. authorities have very little idea of how many American beef cattle might have the disease.

The government plans to double the number of cattle tested in 2004, and has banned the use of "downer cows" for human consumption. While the Washington cow that tested positive for BSE was indeed unable to stand, veterinarians say the condition was unrelated to BSE. Therefore it is not clear by how much the ban is liable to reduce the number of infected cattle consumed. Only 200,000 cows slaughtered in 2003 were downers.

The meat of the BSE-positive cow went to market, but some of it was successfully recalled before it was sold to consumers. U.S. authorities called for a switch to the testing procedure that is used in the United Kingdom, which yields its results in one day. Until the switch, U.S. surveillance relied on a test that gave results only after two weeks, after which time the meat from an animal usually has all been sold.

Shortly after the U.S. discovery of BSE, Japan and South Korea instituted a temporary ban on the import of U.S. beef, until more information about the US BSE outbreak becomes available. Since Japan and South Korea are the first- and third-largest importers of US beef, respectively, the economic impact of their bans is significant both for American cattle ranchers and for Japanese and Korean beef consumers. [1]

No case of variant Creutzfeldt-Jakob disease has occurred in North America so far, except among those who have travelled to Europe.

Husbandry practices in the United States relating to BSE

Soybean meal is cheap and plentiful in the United States. As a result, the use of animal byproduct feeds was never as common as it was in Europe. However, U.S. regulations only partially prohibit the use of animal byproducts in feed. Regulations prohibit the feeding of cows, sheep and goat byproducts back to themselves. But the byproducts of ruminants can still be legally fed to pets and to other food animals such as pigs and chickens. It is also legal for these food animals to eat byproducts of their own species, which ruminants may legally be fed as well. [2]

In February 2001, the USGAO reported that the FDA, which is responsible for regulating feed, had not adequately policed the various bans. [3] Compliance with the regulations was shown to be extremely poor before the discovery of the Washington cow, but industry representatives report that compliance is now 100%. Even so, critics call the partial prohibitions insufficient.

Research on treatment

Further Research

• You Don't Need Meat, by Peter Cox, ISBN 0-7225-1298-8. Details history of Mad Cow (BSE), and varient diseases scrapie, CJD, kuru.
• Mad Cow USA, by Sheldon Rampton and John Stauber, ISBN 1-56751-110-4. (The entire original edition of the book is online)
• Mad Cowboy: Plain Truth from the Cattle Rancher Who Won't Eat Meat by Howard F. Lyman, ISBN: 0684854465. (Lyman and Oprah Winfrey were sued for discussing this book)
• Mad Cow Disease: Plague of the 21st Century? (audio presentaton), by Dr. Michael Greger. Dr. Greger has written many articles on Mad Cow disease, and the risks to U.S. consumers.
• http://www.bseinfo.org - The Source For Bovine Spongiform Encephalopathy Information. This site is funded in part by America's Beef Producers through the Beef Checkoff Program and managed by the National Cattlemen's Beef Association on behalf of the Cattlemen's Beef Board and State Beef Councils.

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