Holy cow! What now? Mad cow disease has hit the U.S. How worried should you be?
Until last year, mad cow disease mad cow disease: see prion.
mad cow disease
or bovine spongiform encephalopathy (BSE)
Fatal neurodegenerative disease of cattle. Symptoms include behavioral changes (e.g. wasn't high on Americans' list of worries. The disease had struck only in other countries, such as the United Kingdom (UK), Canada, and Japan. That changed on December 23, when a cow in the state of Washington tested positive for the disease. Worse, before anyone knew, meat from this cow was sold across several Northwestern states, Hawaii, and Guam. When the test results came back, the U.S. Department of Agriculture (USDA USDA,
n.pr See United States Department of Agriculture. ) recalled the beef. But for many consumers, the announcement came too late--they had already eaten the recalled beef. Luckily, USDA practices in place at the time limited the likelihood that any infected tissue was in the meat. Within a week, the USDA announced new regulations to keep beef even safer (see "New USDA Regulations," page 9).
How are teens across the country responding to the news? A group of ninth-graders from Pennsylvania had mixed reactions. "I'm not worried about mad cow disease. It has yet to infect more than one cow in the U.S., and they're taking many precautions," Karlie says. Justin, on the other hand, isn't convinced. "I don't eat beef at all now," he says. Whatever your opinion, you might find yourself in the cafeteria wondering: Just what is mad cow disease? Should you be worried?
The drama first unfolded on Pitsham farm in the UK in 1984. A cow started losing weight, staggering, arching its back, and drooling drooling
the discharge of saliva from the mouth. A normal feature in some breeds of dogs such as St. Bernard, Newfoundland and English bulldog, presumably because of their loose, pendulous lips. . It acted like, well, a mad cow. But at the time, no one had ever heard of mad cow disease. The cow died six weeks later. Soon cows in other British herds were dying.
In 1986, scientists discovered the disease was a type of spongiform encephalopathy spongiform encephalopathy
Encephalopathy characterized by progressive diffuse vacuolation of the cerebral cortex. (in-SEH-fuh-LAH-puh-thee), a category of diseases that destroys neurons and leaves small holes in the brain. This class of disease is fatal. Scientists coined the cows' malady malady /mal·a·dy/ (-ah-de) disease.
A disease, disorder, or ailment.
a disease or illness. bovine spongiform encephalopathy bovine spongiform encephalopathy: see prion. (BSE See Bombay Stock Exchange.
See Boston Stock Exchange (BSE). ), or mad cow disease.
Spongiform encephalopathies are also called prion prion (prī`ŏn), infectious agent thought to cause a group of diseases known as
prion diseases or transmissible spongiform encephalopathies. (PREE-on) diseases. Dr. Shu Chen, associate director of the National Prion Disease Pathology Surveillance Center at Case Western Reserve University in Cleveland, Ohio, explains why: "The current understanding is the prion is an infectious agent infectious agent Pathogen, see there made up of an abnormal form of protein."
Cells make protein, strings of chemicals called amino acids. Nerve cells make normal priori protein (PrP) molecules, which can flip between shapes. When the PrP folds abnormally, the misfolded PrP molecules form prions that tan cause disease. According to the prion theory, misfolded PrP force normak PrP molecules to fold to match them. In this way, prions multiply in the cell and eventually kill it (see diagram, below). As these prions kill cell after cell, they leave small vacuoles, or holes, in the brain. Over time, they form plaques, tangled protein masses.
BSE might have begun with a surprising notion--feeding meat to cows, which are herbivores, or plant eaters. Farmers began adding bone meal from slaughtered sheep to cattle feed. Another prion disease, called scrapie scrapie: see prion. (SCRAPE-ee), strikes sheep. Scientists believe that cows that ate scrapie-infected sheep became infected. Then cow carcasses were ground up and added to cattle feed. The disease spread through British herds as cows ate their infected relatives.
In the decade following the discovery of mad cow disease, several humans died after developing symptoms similar to those of cows with BSE. Doctors thought the victims had a rare human priori disease called Creutzfeldt-Jakob (KROITS-felt YAH-kop) disease (CJD CJD
CJD Creutzfeldt-Jakob disease, see there ). But the victims were younger than most CJD patients, and the plaques on their brains didn't look like CJD plaques. "They look like daisy flowers because the central core of the plaque is surrounded by little petals of vacuoles," says Dr. Paul Brown, senior investigator at the National Institutes of Health. In 1996, scientists concluded they'd discovered a human version of BSE, variant Creutzfeldt-Jakob disease Creutzfeldt-Jakob disease: see prion.
Rare fatal disease of the central nervous system. It destroys brain tissue, making it spongy and causing progressive loss of mental functioning and motor control. (vCJD).
One way humans can contract vCJD is by eating BSE-contaminated cow parts. An infected cow's brain, spinal cord spinal cord, the part of the nervous system occupying the hollow interior (vertebral canal) of the series of vertebrae that form the spinal column, technically known as the vertebral column. , and other nervous-system tissues can carry the disease.
CAUSE FOR CONCERN?
Twenty-four countries have reported at least one BSE case. More than 183,000 instances of BSE and 143 of the world's 153 vCJD cases have occurred in the UK. To stop the outbreak, the UK banned farm animals from cattle feed and killed thousands of cows that may have been exposed to BSE. Sync 1992, the number of BSE cases there has been dropping.
In 1989, the U.S. banned the import of cattle products from countries with BSE. In 1997, the U.S. extended the ban to all European countries and banned the use of farm animals in cattle feed. These safeguards seemed to keep BSE out of the country--until the cow in Washington tested positive. So how did that cow slip in? Findings suggest it came from Canada.
Should you worry about mad cow disease? Chen says, "If the problem is limited to a single herd or very specific animal populations and is not spread to other places, then I don't think people should be too worried. But of course this depends on a very good surveillance system for BSE."
Some people believe the U.S. should test every cow that's slaughtered. But Sara Goodwin, spokesperson for the National Cattlemen's Beef Association National Cattlemen's Beef Association or NCBA, an advocacy group for beef producers in the United States, reports that it works "to increase profit opportunities for cattle and beef producers by enhancing the business climate and building consumer demand. , insists, "We have the systems in place to detect this disease, prevent its spread, and to protect animal and public health. U.S. beef remains the safest in the world."
Most of the ninth-graders interviewed don't plan to change their eating habits. But Rachal adds: "I'll think more about my food, and where it came from."
HOW MAD COW DISEASES SPREADS
Mad cow disease starts after a cow eats feed contaminated with nervous-system tissue from an infected cow or sheep. Normal PrP molecules, made by nerve cells, become abnormally folded. These misfolded PrPs are known as prions. Misfolded PrP force normal PrP to refold Re`fold´
v. t. 1. To fold again. to match the misfolded ones. New prions are formed. Over time prions accumulate in the cow's brain cells, crippling the animal.
1 Nerve cell produces normal PrP molecules.
2 Misfolded PrP, or prion, invades causing normal PrP to misfold.
3 Prions build up and eventually kill the cell.
4 Prions invade other cells, where the process repeats.
Did You Know?
* In 2002, 1.3 million cattle were slaughtered in Japan; each was tested for bovine spongiform encephalopathy (BSE). In the U.S., however, only 20,000 of the 35 million cattle slaughtered in 2002 were tested for BSE.
* U.S. consumers spend approximately $50 billion per year on beef.
Directions: Read the story. Then test your comprehension by circling the correct answer.
1. Cows are naturally
2. Which of the following about prions is not true?
a. They are infectious agents made up of an abnormal form of protein.
b. They are folded into abnormal shapes.
c. Prions cause abnormal nerve cells to multiply.
d. Prions form tangled protein masses.
3. People can become infected with the human version of mad cow if they eat an infected cow's
a. nervous system tissue.
b. spinal cord.
d. all of the above.
4. Normal PrP molecules are made by
b. nerve cells.
c. amino acids.
d. blood cells blood cells,
n.pl the formed elements of the blood, including red cells (erythrocytes), white cells (leukocytes), and platelets (thrombocytes).
See erythrocyte and leukocyte. Platelets are classed separately. .
5. BSE may have originated when British cows ate
a. scrapie-infected sheep.
b. tainted plants.
c. other cows.
d. an unknown source.
Take It Further:
Conduct a class poll. Will you eat beef despite the discovery of a case of mad cow disease? Why or why not?
1. b 2. c 3. d 4. b 5. a
For terrific information on mad cow disease, visit the companion Web site to the NOVA program "The Brain Eater." It includes a teacher's guide and activity pages. Visit: www.pbs.org/wgbh/nova/madcow/
Check out the U.S. Food and Drug Administration's Web page on bovine spongiform encephalopathy. www.fda.gov/oc/opacom/hottopics/bse.html
Also read these news articles:
"How Now, Mad Cow?" by Cathy Booth Thomas, Time, January 12, 2004.
"Mad Cow: What's Safe Now?" by Jerry Adler, Newsweek, January 12, 2004.
RELATED ARTICLE: New USDA regulations.
After the first cow in the U.S. was diagnosed with BSE, the U.S. Department of Agriculture created additional regulations to ensure the safety of the country's meat supply.
SOME OF THE NEW RULES:
1 Downer down·er
A depressant or sedative drug, such as a barbiturate or tranquilizer. cattle, or cows that are unable to stand, are banned for use as food.
2 Cattle tested for BSE will be held until test results come back negative.
3 Brain, spinal cord, and other central-nervous-system tissues from cattle 30 months of age and older, along with the small intestine small intestine
Long, narrow, convoluted tube in which most digestion takes place. It extends 22–25 ft (6.7–7.6 m), from the stomach to the large intestine. of all cattle, are banned for use in the human food supply. (Since BSE symptoms usually take three and a half years to show, cattle younger than 30 months aren't considered risky.)
4 Advanced Meat Recovery Advanced meat recovery (AMR) is a slaughterhouse process by which residual meat trimmings are extracted from bones and other carcass materials. This meat is comparable in appearance, texture, and composition to meat trimmings and similar meat products derived by hand. (AMR (1) (Adaptive Multi-Rate) A variable rate speech codec selected by the 3GPP for the 3G evolution of the GSM cellphone system (WCDMA). Using the Algebraic CELP (ACELP) compression technology, AMR provides toll quality sound at transmission rates from 4.75 to 12. ) is a technology that uses high pressure to remove muscle tissue from the bone. Spinal cord was already banned from being included in AMR product. Now dorsal root ganglia ganglia /gan·glia/ (gang´gle-ah) plural of ganglion. (clusters of nerve cells connected to the spinal cord) are also prohibited.
5 Mechanically separated meat Mechanically separated meat (MSM), also known as mechanically recovered meat (MRM) is a paste-like and batter-like meat product produced by forcing beef, pork or chicken bones, with attached edible meat, under high pressure through a sieve or similar device to separate the is banned from use in human food, since it could contain bits of nervous-system tissue.