Vibrio parahaemolyticus and Shellfish Safety

Vibrio parahaemolyticus is one of the leading causes of foodborne illness associated with seafood consumption worldwide. V. parahaemolyticus is a native bacterium to Salish Sea coastal waters and present in higher quantities during summer months. Humans who consume raw or undercooked shellfish, most commonly oysters, containing V. parahaemolyticus can develop a gastrointestinal illness. Typically self-limiting, V. parahaemolyticus infections can also lead to life-threatening skin infections or septicemia, particularly in individuals with weakened immune systems. The Washington State Department of Health (Health) manages V. parahaemolyticus through regular environmental sampling during summer months, implementing a V. parahaemolyticus Control Plan for the commercial shellfish industry, and issuing health advisories for recreational harvesters. Even with these measures in place, the numbers of V. parahaemolyticus illnesses have not declined in Washington and nationally V. parahaemolyticus-related illnesses are on the rise. V. parahaemolyticus is a highly temperature-dependent bacterium, with doubling rates of about 1.5 hours at 80⁰F. Understanding how shellfish exposure to high temperatures in intertidal areas influences the illness-causing potential of V. parahaemolyticus is a key component of Health’s Vibrio Program. The need for this data is made more critical by the potential for illness reports to increase with warming waters. As we experience climate change, it is essential to gain a more thorough understanding of how V. parahaemolyticus interacts with the dynamic Salish Sea ecosystem. V. parahaemolyticus will likely thrive with warmer water temperatures as well as warmer air temperatures with a greater number of sunny days in the summer months. Although lacking long-term datasets, recent annual variability in conditions such as the record-breaking weather in the summer of 2013 may provide a glimpse of things to come and valuable insights into how shellfish managers, harvesters, and consumers may need to adapt to a changing marine environment