Get the latest information on the risk of mad cow disease.
Mad cow disease was first officially diagnosed in Britain in 1986. Since then, nearly 200,000 cases of the disease have been confirmed worldwide, two of them in the United States. Although strict safety measures have led to a significant drop in the number of reported cases, mad cow disease remains a concern for both animals and people.
Here we answer some of your questions about mad cow disease, the risks mad cow disease poses, and how you can protect yourself, your family, and your pets.
What is mad cow disease?
Mad cow disease is the common term for bovine spongiform encephalopathy (BSE), an invariably fatal disease that slowly destroys the nervous system in cattle. Scientists believe the disease is caused by a protein called a prion that occurs naturally in the brains of animals and people. Normally, prions are harmless, but when they're misshapen — something that can happen when a process called protein folding goes awry — they can cause devastating illness.
Are prions the same thing as bacteria or viruses?
No. Unlike viruses and bacteria, prions lack nucleic acid, a vital component of living cells. They're also nearly indestructible — impervious to heat, radiation, washing, boiling and strong chemicals, including stomach acid.
How do cattle develop BSE?
The most likely explanation is that cattle developed the disease from eating feed containing the ground-up parts of infected animals. That's why most countries now ban the use of mammalian protein in feed intended for cows and other ruminants. Some research suggests that, at least theoretically, infected prions also may be transmitted in animal urine.
What is Creutzfeldt-Jakob disease?
Creutzfeldt-Jakob disease (CJD) is a fatal, degenerative brain disorder in humans. Like mad cow disease, it develops when prions attack brain cells. Most people develop CJD for no apparent reason, but some inherit a genetic mutation for the disease. In a few instances, CJD has been transmitted through cornea and skin transplants, blood transfusions or contaminated surgical instruments used in brain surgery. And a type of CJD, called variant CJD (vCJD), can occur after eating meat from cows infected with mad cow disease.
What does vCJD do to humans?
When a person eats BSE-infected meat, prions from the meat are absorbed into the bloodstream and eventually carried to the brain, where they begin destroying brain cells. When the infected cells die, prions are released into normal brain tissue and go on to infect more cells. In time, large clusters of cells die, leaving the brain riddled with sponge-like holes.
The first indications of the disease are psychiatric — personality changes, memory loss and impaired judgment. People with vCJD eventually develop dementia, which robs them of the ability to speak, think, remember or care for themselves. Problems with balance and coordination also are common, leading to falls and difficulty walking.
Although it seems to take years or even decades for signs and symptoms of vCJD to appear, once they do develop, people with the disease rarely live more than 12 to 14 months. The cause of death usually isn't the disease itself but a complication such as infection or heart or respiratory problems.
Are certain types of beef or cuts of beef safer than others?
The chances of eating infected beef are very low — even in countries with a relatively high rate of mad cow disease, such as the United Kingdom, Portugal, France, Spain and Germany. Still, the meats most likely to contain prions include hamburgers, hot dogs, sausages and luncheon meats because they generally contain meat from different parts of the animal. The parts of cows that have the highest risk of carrying prions include the bone marrow, brain, spinal cord, eyes and small intestine. Cuts of beef muscle or whole muscle meats appear to be free of the prions that can lead to vCJD.
Is any type of beef absolutely safe?
Several choices exist if you're still nervous about mad cow disease but want to continue eating beef. Many independent farmers, natural foods stores, coops and some larger grocery stores sell organic beef . This meat comes from cows that eat grains and grasses rather than feed containing parts of other animals. If you're concerned about vCJD, you might feel better feeding your family beef from cows that have eaten only grass.
Organic beef is labeled with a green circular symbol that signifies it's certified organic. Meat that isn't certified by the federal government can't claim to be organic.
Can you contract vCJD by eating contaminated beef just once?
That's not known. Theoretically, if you consumed enough abnormal prions and enough time passed for the disease to develop, it's possible you could get vCJD from eating infected beef just once.
Can you contract vCJD by drinking milk, eating gelatin or getting vaccinated?
Not according to current evidence. Scientists have studied cows with BSE and determined that the prions that cause vCJD in humans are found only in the brains, eyes, spinal cords and related tissues of cows. The milk and muscles of cows don't appear to carry the prions, which means that milk should be safe to drink.
Vaccinations are also safe. Several components of cows, such as blood, enzymes and amino acids, are used to grow the bacteria and viruses needed to make some vaccines. But not all vaccines are grown in cattle parts. The FDA's Center for Biologics Evaluation and Research (CBER) oversees vaccines and recommends that companies producing vaccines from cattle parts use only cattle from low-risk countries, such as the United States. The CBER keeps a listing of companies that use cattle from countries that aren't classified as low-risk on its Web site.
Eating gelatin may pose some risk because it's made from the bones and hides of cows. But the risk of infection is low, and the process used to make gelatin appears to reduce the ability of prions to infect people.
What about insulin, which sometimes is derived from the pancreas of cows?
Insulin sold in the United States isn't made from cows, but people for whom available forms of insulin don't work are allowed to import beef insulin from other countries. If you do so, keep in mind that insulin may be a possible source of vCJD if it's derived from an infected cow. And because beef insulin comes from countries outside of the United States, the Food and Drug Administration (FDA) can't evaluate the safety of the insulin you import. If you use beef insulin, talk to your doctor.
Do children contract vCJD more easily than adults do?
No evidence shows that children are more vulnerable to vCJD than adults are. But because children are more likely to eat hot dogs and hamburgers, they may be at higher risk.
Will cooking beef to a certain temperature destroy the prions?
No. Prions are nearly impossible to kill, even at very high temperatures. Your best bet for avoiding BSE-infected beef is to be selective when choosing meats. Choose cuts such as roasts and steaks over hamburger or luncheon meats. If possible, buy meat from countries with a low risk of mad cow disease, such as the United States.
The federal government is considering labels for meat that would show in what countries each cow was born, raised and slaughtered. Currently, origin labels are voluntary, though the law could become mandatory in the future.
What if my dog or cat eats pet food made with mad-cow-infected beef?
Several species can get diseases related to BSE and vCJD, including goats, sheep, mink, deer, elk and cats. Dogs don't appear to get this type of disease. Still, because cats and dogs often eat food that contains ground-up scraps of animals, including cows, your anxiety over your pet's health is reasonable.
Current restrictions on beef for human consumption don't apply to beef for cats' consumption. Even so, the FDA says your cat's risk of getting mad cat disease (feline spongiform encephalopathy) is very low. To be safe, however, avoid pet foods that contain beef. And look for pet foods made from "human-grade ingredients" or brands that don't contain animal byproducts. They may be slightly more expensive than other brands are, but they're also likely to be safer.
Last Updated: 02/10/2006