Issue Brief Food Policy Research Center
Potential Impacts of a Zero Tolerance Policy for Salmonella on Raw Meat and Poultry
- Despite progress in reducing the prevalence of Salmonella in raw meat and poultry, human illness due to Salmonella has not decreased over the past 15 years.
- High-profile outbreaks and the proportion of Salmonella cases that are attributed to raw meat and poultry products have created a demand for new strategies to control Salmonella in these products.
- The United States Department of Agriculture Food Safety and Inspection Service (FSIS) previously used zero tolerance policies to control E. coli O157 in ground beef. Some have suggested that this serves as precedent for similar action for Salmonella in meat and poultry products.
- Enacting zero tolerance policies for Salmonella will not necessarily produce the desired public health outcomes and may lead to unsustainable increases in the number of meat and poultry products that would be held and recalled, with the potential for increased costs for producers, distributors, and consumers.
Salmonella is one of the leading causes of foodborne illness, hospitalization, and death in the United States (US). Each year, an estimated 1,000,000 illnesses, 19,000 hospitalizations, and more than 350 deaths are attributed to Salmonella.1 In contrast to most other foodborne pathogens tracked by the US Centers for Disease Control and Prevention (CDC) Active Surveillance Network for Foodborne Illnesses (FoodNET), the incidence of human illnesses due to Salmonella has not declined over the past 15 years.2 Estimates of the proportion of Salmonella cases attributed to meat and poultry products range from 33% based on outbreak data to 52% based on expert opinion.3,4 The lack of reduction in the population levels of human Salmonella infections likely reflects the emergence and growing importance of new sources of Salmonella.2 However, the occurrence of high profile outbreaks, such as the year-long outbreak of S. Heidelberg infections linked to chicken, reinforces the demand for new strategies to control Salmonella in raw meat and poultry.5-7
Zero tolerance used to reduce E. coli O157:H7
A zero tolerance policy means that the presence of an agent on a food product, at any level, is considered adulteration, and therefore that product is subject to regulatory action. Following a 1993 outbreak that involved > 700 illnesses and 4 deaths, FSIS determined that ground beef with any detectable E. coli O157:H7 should be considered adulterated.8 The implementation of this policy, combined with the concerted efforts of multiple food industry segments, regulatory, and public health officials, led to a drop in the incidence of E. coli O157:H7 infections from 2.6 cases per 100,000 population in 1996 to 1.1 cases per 100,000 in 2012.2 Since the enactment of zero tolerance, far less than 1% of raw ground beef samples test positive for E. coli O157:H7 each year.9 However, an average of 11 recalls of ground beef products continue to occur each year, 3 associated with human illness and 8 more associated with the presence of E. coli O157:H7 detected by microbiological sampling.10
Would zero tolerance be effective in controlling Salmonella?
Controlling Salmonella on raw meat and poultry is considerably more complex than controlling E. coli O157:H7. In addition to environmental and surface contamination issues, strains of Salmonella may contaminate internal tissues, and this may vary by type of Salmonella and food animal species. Implementing a zero tolerance policy alone is not sufficient to reduce the public health burden of illness. For example, despite an existing zero tolerance for Salmonella on ready-to-eat foods, including fresh produce, outbreak data suggests that 41% of Salmonella infections in the US may be attributed to fruits, nuts, and vegetables.3, 4, 11 Enacting a zero tolerance for Salmonella on raw meat and poultry products would result in a dramatic increase of recalls and market withdrawals of these products. Based on results of FSIS Pathogen Reduction/ Hazard Analysis and Critical Control Point (PR/HACCP) verification testing for Salmonella in 2013, as many as 1.6% of ground beef samples, 3.9% of retail chicken, and 15% of ground turkey samples could be subject to regulatory action.12 Given the length of time required to confirm presumptive results, this policy shift will undoubtedly increase the cost of producing these products and result in many more meat and poultry recalls. This potential impact would be several orders of magnitude greater than is currently seen with E. coli O157:H7 in ground beef.
Possible alternatives to zero tolerance policy for Salmonella on raw meat and poultry
Research based on monitoring Salmonella in various production systems has helped reduce the prevalence of Salmonella contamination of raw meat and poultry over the past decade. For example, the percent of positive Salmonella tests for young chickens in the PR/HACCP verification testing program decreased from an original baseline of 20% in 1995 to 3.9% in 2013.12 Furthermore, the rate of positives is considerably less in large processing plants (1.5%) than in small (6.5%) or very small (17%) plants.12 This suggests that having more resources to put into monitoring and managing Salmonella in processing plants leads to more effective control. Under a zero tolerance policy, identification of Salmonella would be self-incriminating and a barrier for companies interested in continuing effective performance monitoring standards.
Eliminating consumer exposure to Salmonella on raw meat and poultry products at the retail level would require use of a terminal treatment such as irradiation. Although approved for use for the control of Salmonella in ground meat and poultry products, resistance from certain advocacy groups and the lack of consumer demand for irradiation represents an important barrier to its use. Other pathogen reduction treatments such as high-pressure treatment may be more acceptable alternatives.
Methods that quantify levels of Salmonella on raw meat and poultry can more fully characterize the risk of human illness at different levels of exposure. In outbreaks associated with ready-to-eat foods, higher levels of contamination have been associated with higher rates of illness among persons who ate the food. Similar relationships likely occur with raw meat and poultry products. An alternative to zero tolerance is to develop enforceable performance standards based on levels of Salmonella contamination associated with illness, rather than on the qualitative presence or absence of Salmonella. Models of disease transmission based on actual outbreaks and dose-response models can help improve our understanding of the relationship between levels of contamination in raw meat and poultry products and the risk of illnesses in consumers exposed to the products. This approach to risk assessment can be used to develop tolerance levels that prevent illness transmission without creating regulatory barriers that prevent companies from monitoring Salmonella in their facilities.
- Scallan, E.; Hoekstra, R.M.; Angulo, F.J.; Tauxe, R.V.; Widdowson, M.-A.; Roy, S.L.; et al. Foodborne illness acquired in the United States—major pathogens. Emerg Infect Dis 2011 Jan;17(1):7-15.
- Centers for Disease Control and Prevention. Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 1996–2012. MMWR 2013:62(15);283-287.
- Batz, M.B.; Hoffmann, S.; & Morris, Jr., J.G. Ranking the disease burden of 14 pathogens in food sources in the United States using attribution data from outbreak investigations and expert elicitation. J Food Prot. 2012 Jul;75(7):1278-91.
- Pires, S.M.; Vieira, A.R.; Hald, T.; & Cole, D. Source attribution of human Salmonellosis: An overview of methods and estimates. Foodborne Pathog Dis. 2014 Jun 2. [Epub ahead of print]
- FSIS. Salmonella Action Plan. 2013. Accessed on 9/08/2014
- H.R. 4966 To amend the Federal Meat Inspection Act, the Poultry Products Inspection Act, and the Egg Products Inspection Act to provide that meat, poultry, and egg products containing certain pathogens or contaminants are adulterated, and for other purposes.
- CDC. Multistate outbreak of multidrug-resistant Salmonella Heidelberg infections linked to Foster Farms Brand Chicken. 2014. Accessed on 9/08/2014
- Rangel, J.M.; Sparling, P.H.; Crowe, C.; Griffin, P.M.; & Swerdlow, D.L. Epidemiology of Escherichia coli O157:H7 outbreaks, United States, 1982–2002. Emerg Infect Dis [serial on the Internet]. 2004 Apr [June 29, 2014].Accessed on 9/08/2014
- FSIS. Microbiological results of raw ground beef analyzed for Escherichia coli O157:H7, Summarized by Calendar Year. Accessed on 9/08/2014
- Seys, S.A.; Sampedro, F.; & Hedberg, C.W. Assessment of Shiga toxin-producing Escherichia coli O157 illnesses prevented by FSIS recalls of beef products. (Manuscript in preparation) 2014.
- CDC. Foodborne Outbreak Online Database (FOOD). Accessed on 9/08/2014
- FSIS. Progress report on Salmonella and Campylobacter testing of raw meat and poultry products, 1998-2013.Accessed on 9/08/2014
Note: This Issue Brief was first published in October 2014. Minor updates were made in January 2015.