WASHINGTON (AP) -- From consumers to beef producers, Americans braced for the fallout from the apparent discovery of mad cow disease in the United States even as federal officials insisted the food supply was safe.
Read the full story
December 24, 2003
By James Winshall, M.D.
Harvard Medical School
What Is The Doctor's Reaction?
People planning to serve prime rib for their holiday dinner may be thinking twice now that mad cow disease has appeared in the United States. While the timing may be bad, many experts are probably less than surprised that the crippling disease has finally made an American appearance.
Mad cow disease also is known by its medical term: bovine spongiform encephalopathy, or BSE. This cattle disease has a lot in common with a human disease known as Creutzfeldt-Jakob disease, or CJD. About a decade ago, British researchers identified a new form of CJD - which they called new variant Creutzfeldt-Jakob or vCJD - that looked identical to the infection that caused BSE in cows. The identification of more than 100 human cases followed an epidemic of about 50,000 cases of BSE in cattle. Both infections are caused by prions, which are tiny microbes that are smaller even than viruses. Prions appear to contain only protein, and thereby lack the DNA that is required by most living organisms - leading some scientists to question whether prions are really "alive." Furthermore, prions do not appear to be "killed" or inactivated by usual sterilizing techniques such as heating or treatment with many types of germicides.
Once inside a human, prions travel to the brain, where they cause a destructive process that plays out over years. In the end, the brain is left with numerous tiny holes, much like a sponge (hence the name "spongioform") or Swiss cheese. Patients with classic CJD develop a variety of symptoms including a rapidly progressing dementia, mood changes, muscle spasms and difficulty walking. Once memory changes begin, most patients -- who tend to be over age 50 -- die within a year. Compared to the classic form of the disease, patients with the mad cow-associated new variant CJD tend to be younger (an average age of about 30), have more psychiatric symptoms, and progress less rapidly. There are no known treatments for either form of the disease, which has been uniformly fatal.
No one is certain how BSE prions get from cattle to humans, but the best evidence is that it comes from eating beef and beef products. The situation is almost certainly compounded by certain questionable practices within the cattle industry, including using ground-up beef entrails to fortify cattle feed (which tends to promote the spread of disease). British health officials cracked down on such practices following the outbreak of BSE and vCJD in the early to mid 1990s, and the number of new cases of vCJD has declined dramatically. Unfortunately, the U.S. Department of Agriculture - under a lot of pressure from the cattle industry - has been reluctant to impose such measures or to screen more extensively for BSE.
What Changes Can I Make Now?
Most people are wondering: Is it time to stop eating U.S. beef? There's not a simple answer to this question, since cutting out beef is probably the only way to prevent getting vCJD. (Prions may also be transmitted by blood transfusions, although this appears exceptionally rare.) Quarantine procedures should help to curb the spread of the disease, although the slow pace of infection means that it will take months to be sure that more cases do not appear. It's also not clear whether BSE-infected meat may have already slipped into the marketplace.
However, a single infected cow doesn't make an epidemic, and many health authorities think the U.S. beef supply remains safe - at least from BSE. There's some evidence that eating beef "products" (entrails, sausages, cold cuts) may be more risky than eating steaks, since prion levels are higher in nerve, intestines and bones than in muscle. Ground beef may also be a bad choice, since parts of hundreds of different cows may end up in one hamburger.
There are a few other things to keep in mind. First, BSE is only one of many different infections that can be transmitted by eating tainted meat. Your risk of getting a life-threatening bacterial infection from beef is much greater than the risk of BSE. Second, there are other reasons to cut down on beef - namely, the high levels of saturated fat that appear to increase your risk of heart disease and cancer. So, if you want to stay healthy this holiday, consider substituting a big green salad for that hamburger.
What Can I Expect Looking To The Future?
It's too early to tell what will be the fallout from yesterday's discovery of a single U.S. cow with BSE. With any luck this outbreak will mimic a similar one in Canada earlier this year, which was limited to few cattle and has shown no evidence of spreading to other cattle or to humans. It may also lead to some needed changes in the cattle industry that may help to decrease the risk of BSE in the future. In the meanwhile, there's nothing to suggest that we are on the verge of finding new ways to prevent or treat vCJD.
Related Areas:
Creutzfeldt-Jakob Disease (CJD)
