Vibrio parahaemolyticus MANAGEMENT FOR OYSTERS IN MASSACHUSETTS

To meet National Shellfish Sanitation Program and federal Food and Drug Administration standards pertaining to the harvest and handling of oysters and Vibrio parahaemolyticus (Vp.) the Massachusetts Division of Marine Fisheries (DMF) and Massachusetts Department of Public Health (DPH) adopted control measures in 2012 intended to deter the post- harvest growth of Vp. in oysters. Historically Vp. cases in Massachusetts (MA) have been rare and the relatively cool waters and high salinities in MA harvest areas haven not been considered particularly conducive to high levels of Vp. in shellfish. As a result of increased oyster production, warming air and water temperatures, and the introduction of a highly pathogenic strain of Vp. into MA waters this is no longer true. Since 2011 MA has experienced a significant increase in the occurrence of Vp. illness related to the consumption of raw oysters resulting in harvest area closures, recalls and considerable economic loss to the oyster industry. We conducted field studies to validate existing Vp. control measures and aquaculture industry practices in MA to determine their impact on Vp. levels in oysters. We also reviewed environmental conditions, Vp. levels and harvest practices in areas implicated in Vp. cases to better understand what environmental conditions and harvest practices could be leading to the increased risk of Vp. illness in the Commonwealth.