Letter Concerning Misleading Government Reassurances on Mad Cow Disease
Secretary Ann M. Veneman
U.S.Department of Agriculture
14th & Independence Ave., SW
Washington, DC 20250
Fax: (202) 720-2166
Dear Secretary Veneman:
In an apparent attempt to reassure the public of the adequacy of its response to the recently diagnosed case of bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, the United States Department of Agriculture (USDA) has made several false or misleading statements. Here is the evidence:
- The current surveillance system cannot detect BSE if it is present in only one in a million adult cattle, as the USDA has claimed;
- The removal of nonambulatory (“downer”) cattle from the human food supply will not greatly reduce the risk to humans; and
- Although presented as a public health measure, the new restrictions on advanced meat recovery (AMR) systems in reality only alter labeling regulations; consequently spinal cord from younger cattle can still be included in beef stock, extract and flavoring.
Surveillance for BSE
The USDA’s surveillance website claims that the agency’s surveillance system “should allow detection of a case if BSE truly exists at a level of one or more cases per million in the adult cattle population,” a claim reiterated repeatedly by USDA officials in the aftermath of the Washington BSE case. This claim rests on a false assumption which has since rebutted by testing data from Europe, some of which actually appears on the USDA website.
It is certainly true that the risk of BSE is higher in downer than in non-downer cattle; this has been the justification for the USDA BSE surveillance program’s particular focus to date on downer cattle. But the USDA goes further and assumes that all BSE infections that might exist in the United States would occur in the downer population. In fact, data from the European Commission demonstrate that 287 normal-appearing cattle testing positive for BSE in Europe in 2002. While the proportion of non-downer cattle that tested positive for BSE in Europe was predictably lower than that proportion in the downer population (the same should be true domestically), there are approximately 230 times more non-downer adult animals than there are downer animals in the United States, according to the USDA’s surveillance website (195,000 downers among 45 million adult cattle). Thus, unless the risk of BSE in downers is much higher than that among non-downers, there can actually be substantially more BSE cases among non-downers than among downers. By analogy, drivers of red sports cars may be at greater risk of incurring or causing injury than drivers of other cars, but most injuries do not involve red sports car drivers.
The figure below illustrates this point. Based on the USDA’s data on the numbers of animals in the downer and non-downer populations, we have constructed a curve that demonstrates how the fraction of total BSE risk that exists among downer cattle varies according to how many times more risky downer cattle are than non-downer cattle. If, for example, downer cattle are 500 times more at risk for BSE than non-downer cattle, 69% of all BSE cases would be expected among downer cattle and a policy of excluding all downer cattle would have a significant impact. On the other hand, if downers were only five times more risky, only 2% of the risk would be among downers. Actual testing data from Europe, not adjusted for animal age, suggest that we are closer to the latter than the former: cattle populations analogous to what are termed downer cattle in the United States have a BSE prevalence 31 times higher than non-downer cattle. If this ratio is applied (rather than the USDA’s assumption that there is no risk whatsoever among non-downer animals and that the ratio is therefore infinite), we can see from the figure (indicated by the arrow) that only 12% of the total risk occurs among downers, with the remaining 88% among the normal-appearing cattle that are not currently being tested in the United States.
This observation has two main implications. First, the USDA claim that current testing can detect BSE at a level of one in a million cattle is false and should not be repeated. In order to truly be able to detect the one in a million risk, some mix of downer and non-downer testing will be necessary.
The numbers are daunting. In a scenario in which 50,000 tests would be performed on normal-appearing cattle and are all negative, one can still only assume (at the 95% confidence level standard in such calculations) that BSE does not exist at a prevalence exceeding 60 (not one) per million. If we apply that proportion to the 12% of the 35.7 million cattle slaughtered annually in the United Statesthat are over the age of 20 months1 (the age above which all BSE cases worldwide have been detected), that would still mean as many as 257 cattle could proceed to market in any one year without a single case being detected. The USDA needs to be forthright with the American public about these risks.
It is worth recalling that the USDA’s surveillance program has never been directly concerned with protecting the food supply (as witnessed by the now-abandoned practice of allowing most cattle with pending BSE tests to enter the food supply); it was designed to monitor the epidemic, more than to prevent it. To completely eliminate BSE risk would require the testing of all cattle (or at least those over 20-30 months). A reasonable approach would be to test all downers and a large number of older non-downer cattle to get a better handle on the extent of the disease. This approach is consistent with that recently recommended by your international subcommittee, the U.S. Food and Drug Administration’s (FDA’s) Transmissible Spongiform Encephalopathy Advisory Committee and an editorial in the New England Journal of Medicine.
The second implication is that although removing downer cattle from human consumption was appropriate because these animals are more risky, the overall risk to the public was only slightly reduced by this measure because only 12% of the risk resides in the downer population. The benefit of removing downer cattle from human consumption has been oversold as a public health protection measure. Strong enforcement of the FDA’s feed ban and the removal of risky material from human consumption remain our primary protections against this disease.
In addition to these design and risk communication problems, USDA’s surveillance program has been plagued by poor administration. In 2001, we conducted a study comparing the rates of BSE testing across states. Instead of finding approximately equal testing rates, we found a 400- to 2,000-fold difference between the states with the highest and lowest testing rates, suggesting a program in disarray. There appears to be no accepted procedure for deciding which animals to test, a point echoed in the current dispute over whether the Washington BSE case was a downer animal., Moreover, some USDA inspectors have testified that the industry itself selects the cattle brains for testing.
The Washingtoncase has also highlighted the major deficiencies in our ability to track livestock. Only 29 of the 81 cattle in the same herd as the index BSE case could be located by the USDA investigation. A comprehensive life-long tracking system must be implemented as soon as possible. But now that downer cattle have been removed from human consumption, farmers have an incentive to bury suspect animals on the farm, without notifying the USDA. Therefore, farmers should be compensated for providing their downer animals for testing and heavy penalties should be provided for any attempts to elude testing once an on-farm surveillance system is in place.
The recent discovery in a normal-appearing animal in Italy of an apparently new strain of BSE that may elude the tests currently in use in this country underscores the need for the U.S. approval of the more sensitive and rapid tests in widespread use in Europe.
For years, consumer groups have criticized the meat processing system in this country, arguing that certain practices can represent a BSE hazard. Concern has centered on mechanically separated beef (bones with attached muscle are crushed and pushed through an extruder to create a paste) and AMR (the use of belts and bone presses to remove meat from bone), both of which are intended to retrieve the last scraps of meat from a carcass. These processes have been used to produce hamburgers and hot dogs, for example.
Unfortunately, it has taken the Washington BSE case to get the USDA to act forcefully. It has banned the pneumatic stunning devices consumer groups have long condemned because they can disperse nervous tissue widely (and which the industry had largely abandoned anyway) and ruled that humans can no longer consume small intestine at all, as well as the brain, spinal cord and related structures of cattle over 30 months. It has also banned mechanically separated beef from cattle of all ages.
These changes are all welcome, but their impact should not be overestimated. First, while infectious activity has only been demonstrated experimentally in the nervous systems of cattle at about 32 months of age, inherent limitations in the experiment (only 30 animals were tested), the high infectious load in spinal cord and proven contamination of AMR product with spinal cord (35% of samples were contaminated in a 2002 USDA survey) make the safest course to simply preclude the technology’s use on vertebral columns for cattle of all ages.
More fundamentally, however, the USDA continues to present the AMR issue (at least for cattle under 30 months) as a food safety issue while it actually treats it as a labeling issue. Thus AMR contaminated by spinal cord is merely considered misbranded, which means it cannot carry the designation “meat.” None of this precludes labeling spinal cord as “beef” (or, less likely, “spinal cord”) and passing it off as part of beef stock, extract or flavoring.
Second, it still remains possible to eat unprocessed brain and spinal cord in this country, as long as the source animal is under 30 months of age. While recognizing that these products are seen by some as regional or ethnic delicacies, the time has come to seriously consider simply removing brain and spinal cord from the human food supply altogether because together they represent nearly 90% of the infectious load in cattle with BSE. At a minimum, brains and spinal cords need to be clearly labeled, along with a prominent warning about the attendant risk of BSE.
The USDA is charged with both promoting and regulating the agricultural sector. In its public pronouncements, it has emphasized the former over the latter. In contrast to what the USDA has repeatedly claimed or implied, the infected animal in Washington was probably not a downer (if it was, the claims for the effectiveness of the surveillance system would seem more credible), the surveillance system cannot detect the one in a million risk, the removal of downer animals from human food will have only a small protective effect on the safety of the food supply and spinal cord can still be consumed as “beef.” If the public and potential importers of U.S. cattle and cattle products are to be reassured, it can only be on the basis of accurate scientific information, rather than the false or misleading information that has represented a significant portion of the USDA response to date.
Peter Lurie, M.D., M.P.H.
Sidney M. Wolfe, M.D.
Public Citizen’s Health Research Group
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 69 Fed Reg 1865. January 12, 2004.