Resumen de High Salinity Relaying to Reduce Vibrio parahaemolyticusand Vibrio vulnificusin Chesapeake Bay Oysters (Crassostrea virginica)
Salina Parveen, Michael L. Jahncke, Sara Elmahdi, Helen Crocker, John Bowers, Chanelle White, Stephanie Gray, Amanda C. Morris, Kathy Brohawn
Cases of Vibrioinfections in the United States have tripled from 1996 to 2009 and these infections are most often associated with the consumption of seafood, particularly oysters (Crassostrea virginica). Information is needed on how to reduce numbers of Vibrio parahaemolyticusand Vibrio vulnificusin bi‐valve molluscan shellfish (for example, oysters). The purpose of this study was to evaluate the effectiveness of high salinity relaying or treatment in recirculating aquaculture systems (RASs) as methods to reduce the abundance of V. parahaemolyticusand V. vulnificusin oysters. For relaying field trials, oysters were collected from approved harvest waters, temperature abused outside under a tarp for 4 h, and then transferred to high (29 to 33 ppt.) and moderate (12 to 19 ppt.) salinities. For RAS treatment trial, oysters were transferred to 32 to 34 ppt. salinity at 15 °C. After 7, 14, 21, and in some instances 28 d, oysters were collected and analyzed for V. parahaemolyticusand V. vulnificuslevels using multiplex real‐time PCR. Initial levels of V. parahaemolyticusand V. vulnificusranged from 3.70 to 5.64 log10MPN/g, and were reduced by 2 to 5 logs after 21 to 28 d in high salinity water (29 to 34 ppt.). Oyster mortalities averaged 4% or less, and did not exceed 7%. Relaying of oysters to high salinity field sites or transfer to high salinity RAS tanks was more effective in reducing V. vulnificuscompared with V. parahaemolyticus. These results suggest that high salinity relaying of oysters is more effective in reducing V. vulnificusthan V. parahaemolyticusin the oyster species used in this study. Relaying of naturally contaminated oysters to high salinity sites in the Atlantic Coastal Bays and the Chesapeake Bay could provide a low cost and practical mitigation strategy to reduce Vibriospp. in oysters. This could result in decreasing the risk of Vibrioillnesses from oyster consumption during the warmer months when Vibriois present in high numbers. This study provides important information for risk management decisions for the oyster industry and regulatory agencies.
