Shellfish RI 2008: Vibrio parahemolyticus
surveillance in the Northeast US
Research conducted at Department of Fisheries, Animal and Veterinary Science, University of Rhode Island, Kingston, RI
Principal Investigators: Marta Gómez-Chiarri, David Bengtson, and Michael Rice
The industry has prioritized the development of tools to rapidly identify the human pathogen Vibrio parahaemolyticus in shellfish growing areas. Differentiating pathogenic strains from benign strains could have a significant impact on both the wild harvest fishery and the aquaculture industry. Identifying and intercepting contaminated product before it hits the market is the eventual goal.
Outbreaks of V. parahaemolyticus in the Pacific Northwest and Texas during 1997 and 1998 resulted in the adoption by regulatory agencies of a control plan to control sporadic illnesses due to the consumption of raw shellfish with V. parahaemolyticus based on temperatures and total levels of V. parahaemolyticus in shellfish.
However, this plan is based on information gathered in the Gulf of Mexico and Pacific Northwest. More data about the presence of pathogenic strains and relationship with environmental conditions and illnesses in the Atlantic region is necessary in order to develop a rational management plan for the control of V. parahaemolyticus illnesses.
We are surveying for pathogenic strains of V. parahaemolyticus in local waters and shellfish using a sensitive method developed by the Food and Drug Administration (FDA), and will relate levels of pathogenic strains to environmental conditions and reports of human illnesses. We have adapted the methods developed by the FDA and optimized them in our laboratories. Our methods are very sensitive and allow detection of low levels of pathogenic strains in a background of large numbers of non-pathogenic strains.
We are also in the process of evaluating the effectiveness of a method to remove inhibitors affecting the sensitivity of the detection assay using coated charcoal. We are also in the process of determining the temporal and geographical patterns of distribution of V. parahaemolyticus and the effect of environmental factors on bacterial levels in oysters. Our surveillance includes collection of samples of water and oysters every three weeks from four sentinel farm sites, as well as a more intense geographical sampling of 10 farms at the peak of summer temperatures, when risk of V. parahaemolyticus is highest.
Environmental conditions at the sites are being measured throughout the summer (temperature) and at the time of sampling (salinity, dissolved oxygen, turbidity, and organic matter content), so the relationship between environmental parameters and presence of pathogenic V. parahaemolyticus can be determined.
This research will provide data on the levels of pathogenic and non-pathogenic V. parahaemolyticus in farmed oysters and waters in Northeast US. These data will help avoid too stringent regulations of the bivalve industry that could impact the marketability of our farmed seafood products.