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BACKGROUND: Salmonella causes an estimated 1 million illnesses annually in the United States, of which approximately 11% are attributable to animal contact. In recent years, a number of Salmonella outbreaks caused by pet food and pet treats have been identified, though often small and geographically widespread. In 2013, the New Hampshire Division of Public Health Services (NH DHHS) investigated a cluster of Salmonella Typhimurium with indistinguishable pulsed-field gel electrophoresis patterns.
METHODS: A confirmed case was defined as a laboratory-confirmed infection with the outbreak strain of Salmonella Typhimurium in a person with illness onset on or after June 1, 2013. Case-patients were interviewed with standardized questionnaires to assess food, animal, and social histories. Responses were compared to FoodNet Population Survey data for 2006–2008 using binomial probabilities to identify common exposures. Laboratory and environmental investigations were conducted, including testing of implicated product and environmental swabs. Samples were tested in the NH Public Health Laboratories.
RESULTS: Between June and October 2013, a total of 43 ill persons including 36 confirmed cases were identified. Sixteen patients (37%) were hospitalized. Among 43 case-patients interviewed, the proportion exposed to dogs (95%) and pet treats (69%) in the 7 days prior to illness was statistically higher than the general US population (61%, p<0.0001 and 16%, p<0.0001, respectively). On further interview, 38 (88%) reported exposure to Brand X Chicken Jerky, the maker of Brand X chicken jerky, or the facility in which it was made. Product testing isolated the outbreak strain from four (100%) of four Brand X chicken jerky samples, including an unopened package purchased from stores, opened packages collected from patient households, and unpackaged jerky obtained from the jerky maker. The site visit revealed inadequate processing of the chicken jerky, bare hand contact with the finished product prior to packaging, and use of vacuum-sealed packaging, which may enable facultative anaerobic bacteria to proliferate. Seven of nine environmental swabs taken during the site visit also yielded the outbreak strain. Brand X Chicken Jerky was recalled on September 9, 2013.
CONCLUSIONS: Contaminated chicken jerky pet treats caused a large community outbreak of Salmonella Typhimurium in NH. Inadequate processing of chicken combined with poor handling, environmental contamination, and packaging practices contributed to the proliferation of Salmonella in this product. Consumers should be aware of the potential for animals and animal food to carry pathogens that cause human illness and practice good hand hygiene following contact with either.