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Maine DMR Vibrio Education

Vibrios are a naturally occurring bacteria typically found in marine waters. Several species of Vibrio are pathogens and can cause illness in humans including gastroenteritis and septicemia. Illnesses from Vibrio infections are often associated with the consumption of raw or undercooked seafood including bivalve shellfish. Bivalve shellfish are filter feeders, meaning they feed by straining the surrounding water in order to collect food particles; these particles (including bacteria) can then become concentrated in their guts. Vibrio spp. are present throughout the marine environment, but pathogenic strains tend to be associated with warmer waters. If Vibrios are already present in shellfish they can multiply exponentially within harvested bivalves which are exposed to warm temperatures such as the exposed deck of a boat on a sunny day in August or an un-shaded summer picnic table. Research indicates the growth rates of Vibrio parahemolyticus (Vp) within harvested bivalves are determined by temperature; at 90°F the Vibrio population will double every hour, at 80°F it takes about two hours, at 60°F it takes over a day for the bacteria population to double, and below 50 the growth of Vp essentially stops. The best way to keep bivalve shellfish safe from Vibrio contamination is by observing temperature controls including cooling product as quickly as possible after harvest. This applies to recreational harvesters and retail purchases as well; keep your catch or purchase in a cooler with an icepack until you are ready to enjoy it!

The Maine Department of Marine Resources implemented new “Time/Temperature” regulations in 2012 in compliance with the Interstate Shellfish Sanitation Conference Executive Board recommendations and to minimize the risk of Vp to Maine’s valuable bivalve shellfish industry. These regulations include time limits between harvest and delivery to a certified shellfish dealer, time limits on cooling shellfish to an internal temperature of 50°F and other controls to support the maintenance of product at safe temperatures. A guidance document describing these regulations can be found on the DMR website: .

Several states are currently addressing Vp illnesses associated with bivalve shellfish harvest by closing specific growing areas and developing more stringent Vibrio management plans. The best defense against the threat of Vp in Maine shellfish is education of the industry and consumers, as well as a commitment from harvesters and dealers to adhere to time/temperature controls. Keep Maine shellfish safe by keeping it cool!