Wilderness: Shellfish Poisoning, Paralysis

Medically Reviewed by Jennifer Robinson, MD on August 29, 2022

Shellfish Poisoning Paralysis Overview

Shellfish poisoning can occur after eating clams, mussels, oysters, scallops, cockles, starfish, and crustaceans that consume dinoflagellates during a red tide. During a red tide, sea waters turn a reddish color because large numbers of red organisms (dinoflagellates) are present. Dinoflagellates kill fish and other organisms by releasing toxins (poisonous substances). Consequently, shellfish take in the concentrated saxitoxin, a poison that causes paralysis.

Red tides are most common in the cold waters of North America, Europe, Africa, Asia, and Japan. A red tide rarely occurs in warmer climates. People are poisoned when they unknowingly eat shellfish contaminated during a red tide with saxitoxins.

Shellfish that is contaminated during a red tide does not have an abnormal taste, smell, or color, and the toxin is not destroyed by heating or cooking. Paralysis due to shellfish poisoning follows a similar progression to that of pufferfish poisoning.

Shellfish Poisoning Paralysis Symptoms

Symptoms of shellfish poisoning begin 30 minutes to 2 hours after eating and include:

Muscle paralysis may occur. The person who has been poisoned may also develop the following conditions:

Ingesting large amounts of contaminated shellfish can result in coma and respiratory failure.

Shellfish Poisoning Paralysis Treatment

  • Do not induce vomiting
  • In case of vomiting, turn the person on their side to prevent the person from breathing in any stomach contents (vomit).
  • The person may become paralyzed.
  • Medical liquid charcoal to absorb the toxins may be given as a drink.
  • Artificial respiration may keep the person alive until they arrive at a hospital's emergency department.

When to Seek Medical Care

Seek medical treatment as soon as possible.

Synonyms and Keywords

wilderness: shellfish poisoning, paralysis; red tide; food poisoning; diarrhea; abdominal cramps; vomiting; nausea; toxicity

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Author: Scott H Plantz, MD, FAAEM, Research Director, Assistant Professor, Department of Emergency Medicine, Mount Sinai School of Medicine.

Editors: N Stuart Harris, MD, MFA, Staff Physician, Department of Emergency Medicine, Harvard Medical School; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; James Kimo Takayesu, MD, Staff Physician, Department of Emergency Medicine, Brigham and Women's Hospital/Massachusetts General Hospital.

CHC Medical Library and Patient Education: "Fish and shellfish poisoning."

SailNet: "Dangerous Seafood."

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