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Marine Resources
October 1996, Volume 8, Number 2

Paralytic Shellfish Poisoning: The Alaska Problem
Raymond RaLonde, Marine Advisory Program, Aquaculture Specialist

In this issue:
Alexandrium, the Dinoflagellate that Produces Shellfish Poisoning Toxins 8
How Toxic Are Alaska's Most Common Shellfish PSP: The Bacterial Connection Truthsand Myths about PSP

Imagine yourself, a few friends, and family at the beach. The weather is amazingly cooperative this time of year for Southeast Alaska, and you feel blessed to enjoy the sunshine. Even though the wind cools the temperature, the beauty of the Alaska landscape is cause enough for celebration. What a day this is! The ocean and the scenery are magnificent. A seafood feast plannedfor mid-afternoon has members of your party busy harvesting shellfish from the rocky beach. In less time than expected, buckets of harvested shellfish arrive at the feet of the chef. A steamer pot of boiling salt water quickly cooks the bounty, and a few minutes later the harvest is devoured with gusto. What qualities could better represent a day in the Great Land? Reluctant to disrupt theexcitement of the outing, George tells you that he feels a strange tingling on his lips and face. Your spouse is also experiencing the same strange numbness on her face. You, too busy to eat much, don’t understand as each guest complains of this strange ailment. Your spouse stumbles as she carries more food to the table. George becomes dizzy and nauseous. While helping him to a beach chair, you noticethe volleyball team is leaving the playing area as each person becomes listless. The game is over, and unfortunately, so is the party. What is happening to these people? Could seafood fresh from the ocean cause such a serious condition? The problem is paralytic shellfish poisoning (PSP), and there is little you can do at this point except to get these victims to a medical facility and fast. Apotentially lethal event, PSP is a crisis no one wants to experience. As many coastal residents know, eating personally harvested shellfish is risky. As Alaskans you need to know about PSP, what health dangers it presents, and how you can reduce your risk of contracting this dreaded ailment.


12 14

Epidemiology of Paralytic Shellfish Poisoning Outbreaks in Alaska 16 Paralytic ShellfishPoisoning in the North Pacific


The Toxins
In Alaska microscopic single-celled dinoflagellate algae of the genus Alexandrium produce PSP toxins as a normal by-product. Bivalve shellfish (two shelled shellfish, like clams and mussels) feeding on these toxic algae may accumulate PSP toxins to concentrations unsafe for human consumption. The singular term toxin is not an accurate term for PSPsince there are at lease 21 molecular forms of PSP toxins. Collectively, these PSP toxins are termed saxitoxins, deriving the name from the butter clam, Saxidomus giganteus, where saxitoxins were originally extracted and identified. All the saxitoxins are neurotoxins that act to block movement of sodium through


Paralytic Shellfish Poisoning: The Alaska Problem

nerve cellmembranes, stopping the flow of nerve impulses causing the symptoms of PSP which include numbness, paralysis, and disorientation (Mosher et al. 1964). The toxicity of PSP toxins is estimated to be 1,000 times greater than cyanide and symptoms appear soon after consuming toxic shellfish. There is no antidote for PSP, and all cases require immediate medical attention that may include application of lifesupport equipment to save a victim’s life. If the dosage is low and proper medical treatment is administered, symptoms should diminish in approximately nine hours (Kao 1993). Saxitoxin molecules undergo chemical transformations that change one molecular form to another. Transformations are performed by the dinoflagellate cell and by many animals that acquire saxitoxins. One common transformation,...
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