NEWS OF THE WEEK GOVERNMENT
MAD COW DISEASE OUTBREAK Scientists cite tests that USDA could use to protect public health
O
N DEC. 23, A SINGLE CASE OF
mad cow disease, or bovine spongiform encephalopathy (BSE), was detected in the U.S. Since then, nearly two dozen countries have announced they will no longer import U.S. beef, which could decimate the $2.6 billion export market. Since the discovery, USDAhas held daily press conferences to reassure the public about the safety of the beef supply, while some researchers have called for new regulations to test for BSE and contain its spread. USDA insists that its voluntary recall of 10,410 lb of beef associated with the BSE-infected cow was taken out of extreme caution. BSE is caused by misfolded prion proteins thought usually to get into cows through feed made from rendered cattle. The abnormal prions induce normal prion proteins to misfold, and eventually the brain develops spongelike holes. There is no scientific evidence, the agency says, that people can contract the human form of BSE, variant Creutzfeldt-Jakob disease (CJD), so long as the cow's brain and spinal cord are stripped away from muscle before the carcass is cut up. But in recent years, scientists have devised highly sensitive tests that have detected prions in muscle tissue ofhamsters and humans infected with prion diseases, notes Jiri Safar, associate professor of neurology at the University of California, San Francisco. This research suggests that beef muscle from infected cattle also contains abnormal prions but at perhaps one-fifteenth the level HTTP://WWW.CEN-ONLINE.ORG
that occurs in brain tissue, he explains. USDA is relying on research conducted in the late 1980s that used an insensitive test to conclude there are no prions in muscle, Safar tells C&EN. USDA is considering a number of measures to prevent further cases of BSE. One would prohibit the sale of so-called downer cattle, those that cannot walk, for human consumption. BSE, as well as physical injuries, can prevent cattle from walking. Another measure under consideration is to greatly expand the testing program. Out of 35 million cattle slaughtered in the U.S. each year, only about 20,000 are tested. Japan, by comparison, tests every animal, and the European Union tests all animals over 30 months of age.
Safar contends that all slaughtered cattle should be tested with a highly sensitive rapid test. "We have no data to show the real incidence of BSE in U.S. cattle. That is the problem," he says. Safar, Stanley B. Prusiner—who received a Nobel Prize for discovering that prions cause spongiform encephalopathies —and coworkers have developed a rapid, fully automated, highly sensitive assay that will be used to test all cattle in the UK. beginning inJanuary or February The test is marketed by a company Prusiner founded called InPro Biotechnology Using this test, called conformation-dependent immunoassay (CDI), a laboratory could assay 2,000-8,000 samples a day with a turnaround time of five hours, in contrast to the USDA test, which takes seven days. Unlike other rapid tests, CDI directly measures abnormal prions at very l o w levels. —BETTE HILEMAN
BUSINESS
Mad Cow Disease Spurs Interest In Tests
T
he appearance of mad-cow-diseasetainted beef in the U.S. food supply is spurring interest in commercially available diagnostics. Today in the U.S., only 20,000 out of 35 million cattle butchered annually are tested for the disease, also known as bovine spongiform encephalopathy. However, observers expect increased use of tests to detect it in infected animals as a means of preventing its transmission to the human population. Bio-Rad Laboratories, for instance, has millions of dollars in sales of such tests in Europe and Japan. Though the firm does not have approval to sell the tests in the U.S., investors anticipate the need and bid its shares up 20% to $59.82 on the day after the Department of Agriculture revealed the appearance of the disease in Washington state.
Other firms with tests approved in Europe include Abbott Laboratories, InPro Biotechnology, and Switzerland-based Prionics. Strategic Diagnostics has a test that detects meat and bone meal in animal feed, rather than the presence of diseased tissue. Such a test would help enforce compliance with animal feed regulations designed to prevent the spread of mad cow disease to uninfected animals. Another firm with technology to fight the spread of the disease to people is V. I. Technologies. The firm is now in Phase III testing of a system intended to remove infected prions—agents of mad cow disease and the human variant Creutzfeldt-Jakob disease— from blood products intended for human use.—MARC REISCH
C&EN
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