The World Is Your Oyster: A Multidisciplinary Approach To Evaluate the Spatial Distribution, Occurrence and Risk of V. parahaemolyticus in Oysters and Water

Abstract

Vibrio parahaemolyticus (V. parahaemolyticus) and Vibrio vulnificus (V. vulnificus) are naturally occurring bacteria and are the leading causes of seafood-borne illness and death in the United States, respectively. While other foodborne illnesses in the United States are decreasing, V. parahaemolyticus and V. vulnificus cases continue to increase. Often illness from V. parahaemolyticus and V. vulnificus are associated with the consumption of raw oysters. The current understanding of V. parahaemolyticus and V. vulnificus are focused primarily on oysters harvested in the Gulf of Mexico and the East Coast, though there is a growing health risk globally and in Southern California. In this dissertation, a multidisciplinary approach was used to show the spatial distribution of V. parahaemolyticus at a global and local level and data were used to inform risk estimates from consuming Southern California oysters contaminated with V. parahaemolyticus. In this dissertation, a scoping literature review provided an up-to-date understanding of V. parahaemolyticus in water and oysters at a global scale. This highlighted the necessity for oyster-related research publication guidelines to compare studies globally. From the details generated in the literature review, a database was developed to aid in a collaborative effort to better understand V. parahaemolyticus. This dissertation was the first to assess V. parahaemolyticus and V. vulnificus in water and Pacific oysters in Southern California. There was a higher concentration of pathogenic V. parahaemolyticus and V. vulnificus in the water column compared to oysters. Additionally, V. parahaemolyticus concentration in water and oysters and V. vulnificus concentration in water were correlated with environmental covariates. Following this field study, a quantitative microbial risk assessment (QMRA) model was utilized to predict illness risk from V. parahaemolyticus in recreationally harvested oysters from Southern California along the “sea-to-fork” pathway. This study utilized regional-specific and national data to estimate V.10 parahaemolyticus illness risk. The mean probability of illness per serving of oysters was 6.20 x 10-5 (95% confidence interval 5.653 x 10-7 – 1.92x 10-4) from consumption of raw oysters harvested in Southern California following the “sea-to-fork” pathway. The mean V. parahaemolyticus illness risk per serving of oysters immediately following harvest was 5.61 x 10-5 (95% confidence interval 4.84 x 10-8 – 1.83 x 10-4). The sensitivity analysis highlighted the relative importance of the initial concentration of V. parahaemolyticus in the oysters, number of oysters consumed, and concentration of pathogenic V. parahaemolyticus following transport in vibriosis risk.