Paralytic shellfish poisoning

Paralytic shellfish poisoning (PSP) is one of the four recognized syndromes of shellfish poisoning (the others being neurologic shellfish poisoning, diarrheal shellfish poisoning and amnesic shellfish poisoning). All four syndromes share some common features and are primarily associated with bivalve molluscs (such as mussels, clams, oysters and scallops). These shellfish are filter feeders and, therefore, accumulate toxins produced by microscopic algae, such as dinoflagellates and diatoms, and cyanobacteria.

Pathophysiology

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The toxins responsible for most shellfish poisonings are water-soluble, heat and acid-stable, and are not inactivated by ordinary cooking methods. The main toxin responsible for PSP is principally saxitoxin, but also gonyautoxin. The saxitoxins act by blocking sodium ion movement through voltage-dependent sodium channels in nerve and muscle cell membranes. Conduction block occurs principally in motor neurons and muscle. The toxin is made by dinoflagellates of the genus Gonyaulax which create the conditions known as "red tide". Almost all bivalve molluscs such as clams, mussels, oysters, snails and scallops ingest these organisms while feeding, and the poison is stored in their bodies. Most shellfish only store this toxin for six weeks after a red tide passes, but some such as butterclams are known to store the toxin for up to two years.

PSP can be fatal in extreme cases (particularly those already immuno-suppressed). Children are more susceptible. PSP affects those who come into contact with the affected shellfish by ingestion. Ten to thirty minutes after ingestion, symptoms can include nausea, vomiting, diarrhea, abdominal pain, and tingling or burning lips, gums, tongue, face, neck, arms, legs, and toes. Shortness of breath, dry mouth, a choking feeling, confused or slurred speech, and lack of coordination are also possible.

See also

• Cyanotoxin
• Algal bloom (see "toxic chemicals" in paragraph 3)
• Ciguatera
• Dinoflagellate (see "neurotoxins" and "red tide" under Ecology and fossils and see "phosphate" under Cautions)
• Red tide

Related Websites

• Toxicity, Shellfish
• Toxicity, Shellfish