Mass Outbreak of Paralytic Shellfish Poisoning Due to Ingestion of Oysters at Tamano-ura, Goto Islands, Nagasaki, Japan

Abstract

In March 1997, a large food poisoning incident due to ingestion of wild oysters, “magaki”, Crassostrea gigas, occurred at Tamano-ura, Goto Islands, Nagasaki, Japan. Twenty-six people were poisoned, of whom sixteen were hospitalized but recovered. Their main symptoms were paralysis of lips, hands, legs and whole body, vomiting and nausea. Patients had consumed about five oysters, equivalent to 25g of edible shucked parts, cooked with miso-soup or fried or raw and flavored with vinegar. This is the first incident of paralytic shellfish poisoning (PSP) reported in Nagasaki. By mouse bioassay and HPLC, the toxicity score of the “magaki” oysters was shown to be 7-135MU/g and its PSP consisted mainly of the low-toxicity components C1 (PX1) and C2 (PX2). Plankton from the sea water showed almost the same PSP composition pattern as the “magaki” oysters and is believed to be the causative agent. The causative plankton is (are) not among previously known toxic species such as Alexandrium catenella, A. tamarense and Gymnodinium catenatum, and remains unidentified.