A quantitative risk assessment model for Vibrio parahaemolyticus in raw oysters in Sao Paulo State, Brazil

• Probability of illness per serving of raw oysters ranges from 3.1 × 10− 4 (winter) to 6.0 × 10− 4 (summer).
• Temperature control during transport of oysters from production area to retail can reduce the risk by 99%.
• Depuration processes used in the processing plants did not reduce the density of V. parahaemolyticus in the oysters.

A risk assessment of Vibrio parahaemolyticus associated with raw oysters produced and consumed in São Paulo State was developed. The model was built according to the United States Food and Drug Administration framework for risk assessment. The outcome of the exposure assessment estimated the prevalence and density of pathogenic V. parahaemolyticus in raw oysters from harvest to consumption. The result of the exposure step was combined with a Beta–Poisson dose–response model to estimate the probability of illness. The model predicted that the average risks per serving of raw oysters were 4.7 × 10− 4, 6.0 × 10− 4, 4.7 × 10− 4 and 3.1 × 10− 4 for spring, summer, fall and winter, respectively. Sensitivity analyses indicated that the most influential variables on the risk of illness were the total density of V. parahaemolyticus at harvest, transport temperature, relative prevalence of pathogenic strains and storage time at retail. Only storage time under refrigeration at retail showed negative correlation with the risk of illness.