USDA: Cow with BSE likely to be only infected animal in herd

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Since bovine spongiform encephalopathy was diagnosed in Washington state in December, the U.S. Department of Agriculture has been "operating out of an abundance of caution" with regard to public and animal safety, said Dr. Ron DeHaven, the USDA's chief veterinary officer.

Dr. DeHaven spoke at the AVMA Veterinary Leadership Conference in Chicago on Jan. 11 about the ongoing epidemiologic investigation occurring on both sides of the U.S.-Canadian border. Agriculture officials are trying to determine the source of the contaminated feed and whether other animals were infected.

"We know that even in countries with a high prevalence of the disease, most notably the United Kingdom, it is very rare for there to be more than one or two, or maybe three, positive animals in a given herd," Dr. DeHaven said. "It's very likely that this (Washington state cow) was the only animal in that herd that was infected."

Nonetheless, since the Holstein tested positive for BSE on Dec. 23, the USDA has traced, quarantined, and culled hundreds of at-risk cattle, recalled thousands of pounds of beef, and implemented several measures to ensure the safety of the food supply.

Dr. DeHaven believes one of the more important safeguards announced by Agriculture Secretary Ann M. Veneman is a national animal identification system (see JAVMA, Feb. 1, 2004, page 348). Because BSE is not a contagious disease, agriculture officials have had weeks to track down animals of concern.

"But if we were dealing with a highly infectious disease, such as foot-and-mouth disease," he said, "we would need to be able to trace animals in a matter of hours if we had any hope of containing and eradicating this disease."

Such an identification system has been in the works for more than two years. Dr. DeHaven hopes that resources will now be made available to accelerate the system's implementation.

The investigation has traced the infected cow to her birth herd on a dairy farm in Alberta, Canada, meaning there still has not been a native-born case of BSE in the United States. Consumer confidence in the safety of U.S. beef remains high and cattle prices appear to be rebounding.

Dr. DeHaven referred to a study by the Harvard Center for Risk Analysis that concluded that if BSE is in the United States, then it exists at low prevalence. Moreover, the ban on ruminant-to-ruminant feed would eliminate the disease, even if the compliance rate were only 70 percent. The Food and Drug Administration claims a better than 99 percent compliance rate, Dr. DeHaven noted.

Many have tried comparing the BSE situation in North America with those in some European Union nations and Japan. "In fact, the situations are very much different," Dr. DeHaven said.

There has been a high prevalence of the disease in some E.U. countries. Yet, extensive surveillance programs in Canada and the United States demonstrated a low prevalence of the disease. Consumer confidence in those E.U. nations and Japan is so low that governments have gone to such extremes as testing animals that aren't of the susceptible population, such as cows younger than 30 months of age.

The United States is being pressured to follow those models, despite what is scientifically known about BSE, Dr. DeHaven observed.

Since the BSE case was announced in December, exports of U.S. beef and beef products have virtually dried up. In 2002, America exported $3.1 billion in beef and beef products, according to Dr. DeHaven, adding that, "Indeed, virtually all of that export market has now been shut off."

Given the myriad consequences of a cow testing positive for BSE, there is concern that countries will be less inclined to disclose such infections. For instance, the single case of BSE in Canada in May 2003 is estimated to have cost its economy some $4 billion; it's too soon to know the costs to the U.S. economy.

"What we're fearful of now," Dr. DeHaven said, "is that we've created an international disincentive for a country to report a case of BSE."


Dr. DeHaven spoke at the AVMA Veterinary Leadership Conference in January. An overview of the conference will be published in the March 1 News.