Shellfish-borne illnesses from pathogenic V. parahaemolyticus (Vp) in the Northeast US have significantly increased over the past 15 years. Tracking and forecasting the population dynamics of this environmentally transmitted pathogen is key to informing risk assessment and providing for a better understanding of ecological mechanisms underlying human illness potential and expansion.
Previous studies in the Great Bay Estuary (GBE) of New Hampshire and Maine suggested a range of ecosystem targets (water temperature, pH, ecosystem conditions, plankton communities, nutrients) as drivers of V. parahaemolyticus concentration variation in estuarine ecosystems. Tracking these variables can complement management strategies as tools that can provide for improved pre-harvest risk management. The current database for Vp and ecosystem drivers in GBE now spans 18 continuous years at two sites. A combination of descriptive and predictive modeling and multivariate community analysis representing sites and the harvest-area were used to re-analyze Vp concentrations in oysters in relation to water quality and meteorological factors.
The long-term surveillance of V. parahaemolyticus populations revealed a steady increase in concentration from 2007-2017, followed by a decline in more recent years. This 6-year decline occurred despite record high sea surface temperatures, a primary ecosystem driver, in the Gulf of Maine and GBE. The recent trend strays from previously identified and predicted trends (Hartwick et al 2019), thus, predictive models aimed at fitting the data to a trend where increases in V. parahaemolyticus concentrations continue in recent years, are not consistent with the data observed. V. parahaemolyticus pathogenicity markers were detected in aquaculture and wild-caught oysters with increasing frequency from 2014-2020 and have also since declined, which coincides with total V. parahaemolyticus concentration trends and regional vibriosis trends. Continued analysis of the full Vp database, along with continuous databases for Vibrio vulnificus and Vibrio cholerae is underway to provide for expanded risk assessment and ecological comparisons of these pathogenic Vibrio species in the GBE as a model approach for shellfish harvesting areas in the Northeast US.