Amnesic Shellfish Poisoning

Aka: Amnesic Shellfish Poisoning, Amnestic Shellfish Poisoning, Domoic Acid, Domoic Acid Toxicity, Domoic Acid Ingestion

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II. Pathophysiology

  1. Consumption of shellfish (mussels, clams) containing Domoic Acid
  2. Effects are seen in humans as well as marine animals including birds

III. Mechanism

  1. Domoic Acid is produced by Pseudo-Nitzschia Diatoms (marine algae)
  2. Shellfish that filter feed (e.g. mussels, clams) accumulate the Domoic Acid toxin
  3. Domoic Acid is a non-protein Amino Acid
    1. Tasteless and odorless
    2. Heat stable
    3. Water soluble
  4. Domoic Acid is a Neurotoxin
    1. Excitatory at Glutamate receptors
    2. Results in large influx of Calcium and Sodium, causing Neuronal cell death

IV. Findings

  1. Domoic Acid onset of activity within 5 hours of ingestion
  2. Gastrointestinal
    1. Abdominal Pain and cramping
    2. Nausea or Vomiting
    3. Diarrhea
  3. Neurologic
    1. Confusion and Disorientation to coma
    2. Memory Loss
    3. Hemiparesis
    4. Cranial Nerve palsy (e.g. Ophthalmoplegia)
    5. Purposeless chewing or grimacing
    6. Seizures or Status Epilepticus
  4. Cardiovascular
    1. Cardiac Dysrhythmia
    2. Hemodynamic instability

V. Evaluation

  1. See Unknown Ingestion
  2. See Altered Level of Consciousness
  3. Bedside Glucose
  4. Comprehensive metabolic panel
  5. Toxicology Screening
  6. Electrocardiogram
  7. CT Head
  8. Leftover Shellfish can be tested for toxins (ELISA, Liquid chromatography)

VI. Management

  1. Consider alternative diagnoses (see evaluation above)
  2. Supportive Care
    1. Intravenous Fluids
    2. Antiemetics
    3. Status Epilepticus management
    4. Vasopressors for refractory Hypotension
  3. Disposition
    1. Observe all patients with unclear cause, neurologic deficit, cardiovascular instability or Electrolyte abnormality
    2. Patients with mild symptoms may be discharged with close interval follow-up

VII. Complications

  1. Death (2%)
    1. Mortality is primarily in elderly
  2. Seizures
    1. Resolve over weeks in most cases
  3. Persistent Neurologic Deficits (<10%)

VIII. Resources

  1. Amnesic Shellfish Poisoning (Washington Department of Health)
    1. https://www.doh.wa.gov/CommunityandEnvironment/Shellfish/RecreationalShellfish/Illnesses/Biotoxins/AmnesicShellfishPoisoning
  2. Amnesic Shellfish Poisoning (Wikipedia)
    1. https://en.wikipedia.org/wiki/Amnesic_shellfish_poisoning

IX. References

  1. Koch and Tomaszewski (2018) Crit Dec Emerg Med 32(5): 32
  2. Jeffery (2004) Food Chem Toxicol 42(4):545-57 +PMID:15019178 [PubMed]

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