Purpose: This study sought to develop an ingredients-to-consumer quantitative microbial risk assessment model to: 1) estimate pet and human exposure to Salmonella via dry pet food, and 2) assess the impact of industry and household-level mitigation strategies on such exposure.
Methods: Data on prevalence and concentration of Salmonella in pet food ingredients, production process parameters, bacterial ecology, and contact transfer in the household were obtained through a literature review, industry data, and experiments. An agent-based probabilistic Monte Carlo modeling framework was built in the @Risk Excel™ add-in.
Results: Human exposure due to handling pet food is minimal if contamination occurs before extrusion (mean dose 6×10-16 CFU/exposure event, with initial 2,500 CFU/kg in protein meal ingredient). Exposure increases considerably if such contamination levels occur in coating fat bypassing extrusion (mean dose 6×10-4 CFU/event). The outcome is highly variable, spanning 9 log CFU. Recontamination after extrusion and coating, e.g., via dust or condensate, can also lead to high exposure (mean dose 4×10-2 CFU/event with fixed 2,500 CFU/kg contamination in intermediate product). Hand washing after handling food can reduce dose by about 1 log. Exposure is the highest when Salmonella is transferred to human wet food, left at room temperature (dose 8×10-2 CFU after 2 hours, when coating fat is contaminated).
Significance: This model allows quantifying exposure associated with dry pet food, under current and alternative production and handling practices. Results can inform improved industry control measures, risk communication to consumers, and regulations.