Modeling Foodborne Pathogen Transfer and Exposure in the Household Environment

Introduction: Bacterial pathogens can enter into households through food, people, pets and pet food, and environmental media such as air or water. Once in the house, it is not quantitatively known which factors and behaviors are most responsible for exposure as a result of bacterial pathogen spread, persistence, or growth. The role of pets as pathogen vehicles is also poorly understood. While numerous outbreaks have been traced back to human or pet food consumed in the household, actual routes of exposure beyond direct ingestion are unclear. Consequently, existing guidelines to reduce consumer risk are not based on quantitative estimates.

Purpose: This study aimed to: 1) model the spread of Salmonella, introduced via human or pet food, through household environments, and 2) assess exposure risk and the impact of mitigation strategies.

Methods: Data on Salmonella ecology on different foods and surfaces, and transfer by direct contact were derived from literature and experiments. A probabilistic Monte Carlo simulation model was developed to estimate Salmonella spread in the kitchen, living/dining room, bathroom, and on floors. Two main scenarios were considered: (a) a pet feeding or food preparation event, and short-term subsequent actions, (b) an entire day including multiple instances of pet feeding, food preparation, and interactions with household surfaces.

Results: Outcomes were expressed as Salmonella concentration on surfaces, and as doses associated with touching contaminated surfaces or ingesting cross-contaminated food. Results highlight that human food preparation and kitchen hygiene protocols are the actions most affecting pathogen spread and secondary exposure. Contamination entering the house via human food can lead to exposure up to 3 log CFU higher than equal contamination levels in pet food. Handwashing and avoiding conditions favorable to Salmonella growth during meal preparation can effectively mitigate risk.

Significance: This model provides a tool for communicating risk and developing risk-based hygiene guidelines.