We extended our previous farm-to-illness model (NPB project number 07-079) to incorporate the risk of human toxoplasmosis as well as salmonellosis, from the consumption of both fresh intact pork cuts, and mixed pork as represented by breakfast sausage. In addition, the effect of two different production methods: continuous flow and all-in/all-out, is explored.
This risk assessment is based on a probabilistic simulation which models the variation that exists in the various factors affecting the addition, growth, partitioning, and inactivation of pathogens along the pork production chain. The prevalence and level of Salmonella contamination is simulated by the model, beginning with the arrival of weaned pigs at the production site, and tracked through growing, slaughter, processing and consumer cooking to the point of consumption. Toxoplasma level and prevalence in intact meat is represented by estimates from the literature, and the model uses simulated and literature values as input to the mixed meat module, which predicts the level and prevalence of Salmonella and Toxoplasma contamination in servings of breakfast sausage. The effect of cooking on both pathogens is simulated to yield a dose per cooked serving, which is translated into a risk of illness by dose-response models. In the absence of an accepted dose-response model for Toxoplasma cysts in humans, the exponential model is used with two different r-values.
The mean risk of salmonellosis per serving predicted by the model is 2×10-6 for intact cuts of pork and 6×10-6 for breakfast sausage. This translates to 50,000 cases of illness annually from fresh intact pork, and 30,000 for breakfast sausage, using available consumption data.
Depending on the r-value applied, the mean risk of toxoplasmosis predicted per serving of intact pork ranged from 8×10-7 to 8×10-6, and that per serving of breakfast sausage ranged from 7×10-7 to 7×10-6, leading to between 3,000 and 35,000 annual cases from consumption in the home of these two products.
The model supports scenario analysis to explore the impact of:
• proportion of pigs from all-in/all-out sites among pork production facilities
• prevalence of Toxoplasma among pigs contributing to mixed meat
• prevalence of Toxoplasma among grower pigs
• two levels of Toxoplasma cysts in pork
• efficacy of washing of viscera
• proportion of pathogens in protected areas during cooking
• probability of undercooking
This project is of interest to stakeholders at all stages of the pork production chain. The model developed facilitates further understanding of opportunities to manage the risk of both salmonellosis and toxoplasmosis due to pork products. It can also be used to identify important research opportunities.
Contact information: Greg Paoli, Risk Sciences International, Inc.; 200-449 Sussex Drive, Ottawa, ON.; Email: firstname.lastname@example.org