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Mad Cow Disease

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Mad Cow Disease Paper

Mad Cow Disease, or bovine spongiform encephalopathy (BSE), is a fatal brain disorder disease of cattle that affect the central nervous system and causes staggering and agitation. Some unknown transmissible agent causes mad Cow Disease. Currently, the most accepted theory is that the agent is a modified form of a normal cell surface component known as prion protein. In BSE, the unknown agent causes the cow's brain cells to die, forming sponge-like holes in the brain. The cow behaves strangely and eventually dies. The connection between BSE and humans was uncovered in Great Britain in the 1990s when several young people died of a human brain disorder, a new variation of a rare brain disorder called Creutzfeldt-Jakob Disease (CJD), which typically strikes elderly people. The new variation is called new variant Creutzfeldt-Jakob Disease (nvCJD). Eating meat from cows that have been contaminated with Mad Cow Disease also exposed humans to the disease.

BSE is thought to have come from a similar disease in sheep called scrapie. In the 1980s, producers of cattle feed (which often included ground meat and bone meal by-products from sheep) changed the way they processed feed. The change somehow allowed the scrapie disease agent to survive the cattle feed production process. The contaminated food was fed to cattle, which then came down with BSE.

Neither scrapie nor BSE were thought to affect humans. Therefore, meat (nervous tissue) from BSE-infected cows made it into the food supply. Humans who ate the infected meat (probably hamburger or other processed meats) contracted the BSE-causing agent and developed nvCJD.

The agent that causes BSE is currently unknown. The following information is know about the agent:

* The agent must be small - The agent's size must be as small or smaller than a virus.

* It cannot kill it by cooking or freezing - Much higher temperatures than those used in cooking or sterilizing are required to kill it.

* Disinfectants do not work - Normal chemicals that you would typically use to disinfect surfaces for bacteria and viruses (Lysol, Betadine, Clorox) are not effective.

* It does not appear to have genetic information (nucleic acids) - This finding has been questioned.

Research into BSE and similar diseases (nvCJD, CJD, scrapie) have provided three theories about the agent that causes BSE. These theories have lead scientists to believe that it is:

* An unidentified virus or virus-like particle - Although the size of the agent is right, the resistance to heat and chemicals, as well as the absence of any nucleic acids, would make it unlike any known virus.

* A mobile bacterium (Spiroplasma) - Many of the features of Spiroplasma infections are similar to BSE, but there is no direct evidence to tie it to BSE.

* An abnormal protein (prion) - Abnormal prions are found throughout the brains of BSE-infected cows, nvCJD victims, CJD victims and scrapie-infected sheep. The protein is smaller than a virus and not changed by heat or by disinfectants.

The World Health Organization recommends, "Countries should not permit tissues that are likely to contain the BSE agent to enter any food chain, human or animal. This means excluding cattle brains, eyes, spinal cord and intestine (from small intestine to rectum) from the human food supply, and from all animal feed. Unfortunately, the U.S. still feeds those potentially risky tissues to people, pigs, pets and poultry.

Although beef brains, guts, eyes and spinal cords are available to consumers as "variety meats," they are labeled as such and therefore represent only a small fraction of the American public's exposure to these organs. People are more likely to consume potentially infectious tissues such as spinal cord disguised within all-American favorites, like hot dogs and hamburgers.

After a cow is slaughtered and the standard cuts of beef removed, the bloody skeleton with a few scraps of meat are still attached. To recover any last shreds of meat, the bones, prebroken or whole, may be placed in a giant vice-like device that crushes the carcass into bone cakes. The potentially highly infectious spinal cord and fluid may be forced out of the backbone and spewed in the final product. Mechanically separated beef has been used in the United States since the 1970's. Examples of such "quality meat food products" include hot dogs, sausages and burgers. By law, hot dogs can contain up to 20% of this mechanically separated beef.

Although food containing mechanically separated beef must be labeled as such, there are no labels on food in restaurants, so people could be exposed to spinal cord tissue in hot dogs, sausages, hamburgers, and ground meat products when dining out. Although Europe heeded the World Health Organization's warnings and banned such meat recovery systems years ago, these devices remain one of the best opportunities for prion-infected tissues to enter the human food supply in North America.

In 1994, meat processors began using a new technology, called advanced meat recovery (AMR), to help "increase yields and profitability. These systems also extrude meat from the remains of the carcass under pressure, but without crushing the bones. The American Meat Institute describes the process: "Just as fruit processors use machines to remove fruit from peels thoroughly and efficiently, meat companies use similar equipment to remove meat from some hard to trim bones.

The product varies from a ground beef-like texture to the consistency of thick tomato sauce. Before 1994, only cattle skeletal muscle, tongue, diaphragm, heart, and esophagus could be labeled as beef. However, by the end of that year, the



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