The South-Eastern Health Board has issued a health alert relating to certain shellfish harvested from the Waterford estuary. The warning concerns bivalve shellfish (mussels, oysters, clams and scallops) harvested near Waterford and Wexford. During routine monitoring, oysters from this area have been found to contain Diarrhetic Shellfish Poisoning (DSP) toxicity. Cooking does not destroy the toxins, which can cause severe gastro-intestinal symptoms, including diarrhoea. The toxins are produced naturally by phytoplankton.