Freezing Technology

8.3.3 Paralytic shellfish poisoning (PSP)

8.3.3 Paralytic shellfish poinsoning

Intoxication after consumption of shellfish is a syndrome that has been known for centuries, the most common being paralytic shell fish poisoning, PSP is caused by a group of toxins [saxitoxins and derivatives] produced by dinoflagellates of the genera Alexandrium., Gymnodinium and Pyrodinium. 

          Historically, PSP has been associated with the blooming of dinoflagellates [10⁶ cells/liter], which may cause reddish or a yellowish discoloration of the water. 

          The  dinoflagellate blooms are a function of  water temperature, light , salinity, presence of nutrients and other environmental condition.  However, the precise nature of factors eliciting a toxic colour is unknown.  Water temperature must be >5-8^oC for blooms to occur. When temperature decrease to below 4^oC, the dinoflagellate will survive as cysts buried in the upper layer of sediments.

          Mussels, clams, cockles and scallops that have fed on toxic dinoflagellates retain the toxin for varying periods of time depending on the shellfish.  Some clear the toxin very quickly and are only toxic during the actual bloom, other retain the toxin for a long time, even years.

          PSP is a neurological disorder and the symptoms are tingling, burning and numbness of lips and fingertips, ataxia, drowsiness and incoherent speech.  In severe cases, death occurs due to respiratory paralysis.  Symptoms develop within ½ hour to 2 hours after consumption and victims who survive more than 12 hours generally recover.

Toxin is found in their siphon. Gonyaulox tamarensis & Alexandrium catanella the toxin is known as saxitoxin. Toxin is heat stables not destroyed by cooking. One gram toxic meat can kill 5 people. Estimated lethal dose for man is 1-4mg, respiratory failure followed by death. Occurrence of this toxin in tropical water is scarce. US FDA limit is 80mg poison /100g.