As scientists that study food safety issues, we disagree with Mr. Murphy’s claim that E. coli O157 bacteria “cannot be controlled at the source, or at the packing plant, or during further processing, or after packaging and distribution.” Can E. coli O157 be eliminated? Perhaps not, but an overwhelming body of scientific evidence clearly informs us that pathogens like E. coli O157 can be controlled at multiple points of the beef chain. For example, controls implemented at packing plants have reduced the rate of USDA/FSIS positive tests in ground beef by more than 90%. This didn’t occur by chance; it is the result of informed activities to control this and other pathogens.
We all agree, however, that more can be done and we must look for opportunities for continual improvement. The scientific evidence now tells us that control of E. coli O157 at the source is one such opportunity. Each of us has extensive experience evaluating and validating the ability of a variety of technologies, such as vaccination, as effective tools for controlling E. coli O157. Dr. Loneragan and colleagues, in a number of studies, found that vaccination reduces the number of E. coli O157-positive cattle. Moreover, cattle that remained positive actually shed 98% fewer E. coli O157. In a recent large commercial feedlot study, Dr. Renter and colleagues showed the same vaccine reduced the number of cattle shedding E. coli O157 by more than 50%, and also reduced the percentage of high-level shedding animals by more than 75%. These data, along with a tremendous and growing number of other peer-reviewed studies, demonstrate that pathogens like E. coli O157 can, in fact, be controlled at the source. Recently, a number of risk assessments have shown that control at the source likely has positive public-health benefits. For example, Dr. Hurd used a risk assessment model to demonstrate that preharvest interventions, such as a vaccine, have a positive impact for various stakeholders. Their model showed that interventions reducing live cattle prevalence by 50% are expected, based on the best available data, to reduce the chances of a large-scale E. coli O157 outbreak and reduce the number of human illnesses associated with E. coli O157-contaminated ground beef.
Although vaccination or other available interventions may not totally eliminate E. coli O157, applying multiple interventions at key points in the beef chain can contribute to further improvements in the control of E. coli O157. The beef industry has already invested in the development and subsequent implementation of multiple effective interventions in the packing and further processor sector. Yes, occasional contamination events occur; however, the prevalence of E. coli O157 in retail ground beef has been reduced to an all-time low. Further, the CDC data demonstrate that E. coli O157 is one of the few food-borne pathogens in which the incidence of human disease has been declining over the past decade. In fact, the government’s target for reducing E. coli O157 incidence by 2010 was successfully achieved. But the bar has been raised, a new target has been set, and this target will require additional control – such as at the source.
We realize that E. coli O157 continues to be a difficult issue for the beef industry. There are still important efforts to make sure that consumers understand correct handling and proper cooking are crucial for reducing the risk of E. coli O157. However, we know the science – E. coli O157 can be controlled at multiple points of the beef chain, including in live cattle, and we believe it is important to clarify this for the Drovers/CattleNetwork audience.
|Dr. H. Scott Hurd
Iowa State University
|Dr. Guy H. Loneragan
Texas Tech University
806-742-2805 x 268
Dr. David Renter