How Now, Mad Cow?

In December 2003, the United States became the 24th country to diagnose a case of bovine spongiform encephalopathy (BSE), also known as “mad cow disease.” U.S. regulations had required embargoes against all things bovine from the previous 23 countries, and now it is our turn.

Since the suspect 6.5-year-old dairy cow slaughtered in Washington State was a “downer” (not ambulatory), a brain sample was sent to the U.S. Dept. of Agriculture’s reference laboratory in Ames, Iowa, for testing for BSE. The rest of the apparently sound carcass was processed as meat and distributed to several states. How the animal got BSE in Washington (or earlier in Alberta, Canada?) may never be known.

Following Canada’s first BSE case earlier in 2003, seven herds were killed in an unsuccessful search for associated BSE and feed contamination. Similar findings for “our” cow might lead to near-normal exports in another year, assuming establishment of enough cosmetic control measures. More rigorous feed restrictions apparently would not have prevented the earlier Canadian BSE case, and the same may well be true here. It is highly possible that an occasional animal may develop BSE spontaneously, as humans do classical Creutzfeldt-Jakob disease (CJD).

From 1986 until November 2003, 183,634 cattle were diagnosed with BSE in the United Kingdom, compared to 4,469 in the other 22 countries and now one in the U.S. Since 1996, the UK has recorded 143 cases of variant CJD (vCJD) in humans—a BSE:vCJD ratio of 1,284:1. The annual vCJD trend is downward. Given the vCJD incubation period of 10–20 years, the majority of these infections were surely contracted before the disease was recognized and rigorous restrictions were placed on what Britons could eat from cattle.

USDA officials confused the issue by declaring the meat safe, but then recalling it for destruction. Clearly, food safety is in the eye of the beholder: it typically becomes a major issue when hunger is no longer a concern—a situation not yet attained in the U.S. Against the perceived threat of vCJD, we must balance the foodborne illnesses that are already occurring here. Furthermore, with 4,000 deaths annually from malnutrition, 9 million people hungry, and 33 million food-insecure in the U.S., it is clear that not eating is a far greater threat than eating. All food safety decisions should be made with this in mind. Consumer protectionists, who want a risk-free food supply regardless of cost, clearly do not regard the hungry as “stake-holders.” Activists belittle antemortem (looking for neurological symptoms) and postmortem (“poke and sniff ”) inspection, while demanding more costly inspections and testing for every foodborne disease agent.

Our erstwhile BSE protection system entailed banning feeding of almost all mammal-derived feed products to ruminants and testing animals that came to slaughter as downers or with walking problems, as well as a few dead-on-farm cattle. The test used at Ames is a “gold-standard” procedure—slow and more focused on specificity than on sensitivity, performed by neuropathologists. Because of the long response times, it was not thought necessary to detain otherwise-normal carcasses in cold storage awaiting the test results.

In Europe, where all slaughter cattle over 24 or 30 months old are tested, carcasses are held overnight, until judged negative by tests that emphasize speed and sensitivity over specificity. In Japan, all slaughter cattle (even veal calves) are tested, despite the impossibility of a positive result in animals under, say, 20 months of age. The test kits used in Europe and Japan are now available in the U.S., but laboratories to do the tests are not, nor are people trained to collect exactly the right part of each slaughtered animal’s brain for testing.

Meanwhile, USDA is banning slaughter of downer cows and requiring that suspect animals’ carcasses be held pending the completion of testing, which could take days or weeks. Probable results will be more testing of healthy animals and very little testing of excluded downers, suspects, and dead-on-farm cattle. This will minimize the perceived risk to consumer health (which is really negligible) and yield an inaccurate assessment of the true incidence of BSE in the U.S.

Our first BSE diagnosis is an economic and political disaster, with negligible threats to human and animal health in the U.S. Embargoes on our beef exports will have a large impact on the economy, in that food has been the only category of international trade in which the U.S. has consistently maintained a favorable balance of payments. Top-grade beef intended for export will rebound into the domestic market, as it did in Canada, and make needed culling of dairy cattle very difficult. Given the high cost of now-unprofitable rendering and the extreme cost of incineration, cattle unlikely to be sold as food will be difficult or impossible to dispose of, as will newly banned specified-risk materials. Which will prove the greater burden—live, unproductive animals that have to be fed, or dead animals and organs that cannot legally be discarded—remains to be seen.

U.S. food priorities should be to (1) feed everyone, (2) combat foodborne agents that are causing significant incidence of illness and death in the U.S., and (3) deal with hypothetical risks like BSE-vCJD in ways that will minimize damage to the U.S. economy, without taking bread out of the mouths of the hungry.

by Dean O. Cliver is Professor of Food Safety, School of Veterinary Medicine, University of California, Davis, CA 95616.