Detection of Dinophysis species and associated okadaic acid in farmed shellfish: a two-year study from the western Mediterranean area

Introduction: Diarrhoetic shellfish poisoning (DSP), an alimentary intoxication known to lead to intestinal symptoms, and caused by toxins produced by some dinoflagellates (including several Dinophysis), represents a serious threat to public health. The aim of this paper was to provide information about the occurrence and abundance of potentially toxic harmful algal species causing DSP, and the associated concentration of okadaic acid (OA) toxins. The departing assumption was that in the study area there was an increase in the presence both of Dinophysis species and OA and its derivates that could result in a risk to the health of seafood consumers. Material and Methods: During 2015-2016, water and shellfish samples were collected in the Mediterranean area (Sardinia, Italy). Dinophysis cells were counted according to Utermohl's method from water samples, while mass spectrometry was used to identify lipophilic toxins in molluscs. Results: A total of 46 non-compliant samples of Mytilus galloprovincialis were observed. Their non-compliance concerned their OA levels above the legal limit. Among toxic dinoflagellates, D. acuminata and D. sacculus were the species found mostly during DSP events. Conclusion: No cases of human intoxication have been reported, but continuous surveillance of toxic phytoplankton is necessary to predict and prevent its harmful effects on human health.