Shellfish Poisoning: Categories, Symptoms and Treatment

Shellfish poisoning is eating contaminated seafood mainly associated Shellfish Poisoningwith clams, oysters, mussels and scallops, or bivalve mollusks, rather than squid and octopus, among others, which are also shellfish. Its name is misleading as it is not a exactly a type of fish. It is one of the most common seafood enjoyed by many different parts of the world, although is it also one of the most common food allergens worldwide. As filter feeders, shellfish build up toxins made by microscopic algae. Some of these microscopic algae-like include diatoms, cyanobacteria and dinoflagellates.

Most shellfish poisonings arise from warm waters, especially during the months of summer. Incidences of shellfish poisoning also increase when there is a red tide, or harmful algal bloom. Although it is a popular saying to not eat seafood, shellfish included in the months that don’t have the letter R in them (May to August), it is not necessarily factual. Moreover, the harmful substances in shellfish do not die or disappear with cooking, as they are heat stable. And one cannot tell if a shellfish is toxic simply by looking at it.

Categories of Shellfish Poisoning

There are different categories of shellfish poisoning, which are based on the specific toxins or chemicals that poison humans and their corresponding symptoms.

  • Paralytic shellfish poisoning
    • Caused by saxitoxin, neosaxitoxin and gonyautoxins I to IV
    • Neurotoxic shellfish poisoning
      • Caused bybrevetoxins
      • Amnestic shellfish poisoning
        • Caused bydomoic acid
        • Diarrheal shellfish poisoning
          • Caused byokadaic acid and azaspiracid

Symptoms of Shellfish Poisoning

Symptoms of shellfish poisoning usually manifest quickly, usually between 30 minutes to a few hours after eating the contaminated shellfish. Symptoms are quite apparent from their names.

  • Paralytic shellfish poisoning (lethal)
    • Tingling sensation of the lips and tongue which spreads to the fingers and toes
    • Loss of control of arms and legs and coordination
    • Trouble breathing
    • In some cases, nausea and vomiting
    • If ingested in large amounts, paralysis of chest and abdomen, which may lead to death
    • Neurotoxic shellfish poisoning
      • Nausea and vomiting
      • Slurred speech
      • In some cases, tingling sensation or numbness in the mouth, headaches and dizziness
      • Amnestic shellfish poisoning(lethal)
        • Short term memory loss, which may be permanent
        • Nausea and vomiting
        • Abdominal cramps and diarrhea
        • Confusion
        • In severe cases, coma and death
        • Diarrheal shellfish poisoning
          • Nausea and vomiting
          • Diarrhea

Treatment for Shellfish Poisoning

Shellfish poisoning may or may not be an emergency. Although unsure of the type of toxin ingested, it is better to be sure and go to the emergency room or call for emergency medical services. Some of the tips suggested include:

  • Do not try and stop the vomiting. Some doctors may induce vomiting or use stomach pump to remove the toxin, especially if within three hours of ingestion of contaminated shellfish.
  • Drink lots of clear fluids to avoid dehydration.
  • Intravenous (IV) fluids may be given in severe cases.

Shellfish poisoning can be treated effectively, especially if there is early recognition of symptoms. To know more on how to treat shellfish poisoning and other poisoning in the body, join in First Aid Training.


One Response to “Shellfish Poisoning: Categories, Symptoms and Treatment”

  1. george jackson January 19, 2015 at 10:05 pm #

    we live in San Felipe, Baja, MX. A govt alaert came to us Jan 15, 2015: don’t eat fich, clams etc. from Sea Of Cortez because of RED TIDE>>>we can’t find any info as to why it happened, or how long we have to be careful of our local fish. We also do not know how far out N< S< E< W< of our location the red is .
    Can you help us on information as to wat is the real story and maybe how we can prevnt it, we realize it is naturally occurring and induced by agriculture run off, which we know happens here. THIANK YOU fo r your time and consideration. George Jackson

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