Shellfish Toxicity Clinical Presentation
- Author: Thomas C Arnold, MD, FAAEM, FACMT; Chief Editor: Asim Tarabar, MD more...
History
All 4 shellfish syndromes can produce symptoms lasting from a few minutes to several hours after ingestion of contaminated shellfish.
- Paralytic shellfish poisoning
- The onset generally is noted with paresthesias of the lips, tongue, and gums. Symptom onset usually occurs within 30 minutes of ingestion.
- Symptoms at onset rapidly progress to involve the distal extremities.
- Other symptoms include a sensation of floating, headache, ataxia, muscle weakness, paralysis, and cranial nerve dysfunction.
- Gastrointestinal symptoms are less common and may include nausea, vomiting, diarrhea, and abdominal pain. Fatalities are usually within the first 12 hours of symptom onset and are caused by unsupported respiratory failure.
- PSP usually lasts 3 days, but muscle weakness may persist for weeks.
- Neurologic shellfish poisoning
- The illness encountered with NSP is milder than that with PSP. Symptom onset ranges from 15 minutes to 18 hours postingestion, and the duration of toxicity ranges from 1-72 hours (usually < 24 h) postingestion.
- Presenting symptoms include gastroenteritis; rectal burning; paresthesias of the face, trunk, and limbs; myalgias; ataxia; vertigo; and reversal of hot/cold sensation.
- Other less common features include tremor, dysphagia, bradycardia, decreased reflexes, and mydriasis.
- This syndrome presents much like ciguatera poisoning but without a paralytic component, and it may last from several hours to a few days.
- The brevetoxins, unlike the other shellfish toxins, can become aerosolized by the surf and produce an allergic response characterized by rhinorrhea, conjunctivitis, bronchospasm, and cough in sensitive individuals along the shore.
- Diarrheal shellfish poisoning
- DSP is most common in Japan and Europe.
- Gastroenteritis develops shortly after ingestion and generally lasts 1-2 days.
- Amnestic shellfish poisoning
- The only reported outbreak occurred in 1987 and affected more than 100 people after eating mussels harvested off Prince Edward Island, Canada.
- Gastroenteritis followed by headache and short-term memory loss occurred.
- In a few cases, severe cognitive dysfunction to the point of interfering with the patient's ability to perform normal daily activities was noted.
- Seizures, coma, hemiparesis, and ophthalmoplegia were noted in the most severe cases. The mortality rate is 3%.
Physical
- Findings vary according to the syndrome involved.
- Gastrointestinal symptoms occur less often in PSP than in the other syndromes.
- Paresthesias of the face and extremities are noted only in PSP and NSP.
- ASP is the only shellfish syndrome with cognitive dysfunction as an early finding.
- Volume depletion from gastrointestinal symptoms is common to all syndromes.
Causes
Ingestion of raw or cooked mollusks that contain the toxin in sufficient quantities ensures the development of symptoms.
Burgess V, Shaw G. Pectenotoxins--an issue for public health: a review of their comparative toxicology and metabolism. Environ Int. Oct 2001;27(4):275-83. [Medline].
Lefebvre KA, Robertson A. Domoic acid and human exposure risks: A review. Toxicon. Jun 6 2009;[Medline].
Centers for Disease Control and Prevention. Update: Neurologic illness associated with eating Florida pufferfish, 2002. MMWR Morb Mortal Wkly Rep. May 17 2002;51(19):414-6. [Medline].
Bronstein AC, Spyker DA, Cantilena LR Jr, Green JL, Rumack BH, Giffin SL. 2009 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 27th Annual Report. Clin Toxicol (Phila). Dec 2010;48(10):979-1178. [Medline]. [Full Text].
Johnson RC, Zhou Y, Statler K, Thomas J, Cox F, Hall S, et al. Quantification of saxitoxin and neosaxitoxin in human urine utilizing isotope dilution tandem mass spectrometry. J Anal Toxicol. Jan-Feb 2009;33(1):8-14. [Medline].
Nicholson BC, Shaw GR, Morrall J, Senogles PJ, Woods TA, Papageorgiou J, et al. Chlorination for degrading saxitoxins (paralytic shellfish poisons) in water. Environ Technol. Nov 2003;24(11):1341-8. [Medline].
Ahmed FE. Seafood safety. Committee on Evaluation of the Safety of Fishery Products. Food & Nutrition Board, Institute of Medicine. National Academy Press; 1991.
Chandrasekaran A, Ponnambalam G, Kaur C. Domoic acid-induced neurotoxicity in the hippocampus of adult rats. Neurotox Res. 2004;6(2):105-17. [Medline].
Economou V, Papadopoulou C, Brett M, Kansouzidou A, Charalabopoulos K, Filioussis G, et al. Diarrheic shellfish poisoning due to toxic mussel consumption: the first recorded outbreak in Greece. Food Addit Contam. Mar 2007;24(3):297-305. [Medline].
Gessner BD, Middaugh JP, Doucette GJ. Paralytic shellfish poisoning in Kodiak, Alaska. West J Med. Nov 1997;167(5):351-3. [Medline].
Jeffery B, Barlow T, Moizer K, Paul S, Boyle C. Amnesic shellfish poison. Food Chem Toxicol. Apr 2004;42(4):545-57. [Medline].
Kawatsu K, Hamano Y, Noguchi T. Production and characterization of a monoclonal antibody against domoic acid and its application to enzyme immunoassay. Toxicon. Nov 1999;37(11):1579-89. [Medline].
Poli MA, Musser SM, Dickey RW, Eilers PP, Hall S. Neurotoxic shellfish poisoning and brevetoxin metabolites: a case study from Florida. Toxicon. Jul 2000;38(7):981-93. [Medline].
Stommel EW, Watters MR. Marine Neurotoxins: Ingestible Toxins. Curr Treat Options Neurol. Mar 2004;6(2):105-114. [Medline].
Usleber E, Dietrich R, Burk C, Schneider E, Martlbauer E. Immunoassay methods for paralytic shellfish poisoning toxins. J AOAC Int. Sep-Oct 2001;84(5):1649-56. [Medline].
Vale P, Sampayo MA. Comparison between HPLC and a commercial immunoassay kit for detection of okadaic acid and esters in Portuguese bivalves. Toxicon. Nov 1999;37(11):1565-77. [Medline].
Van Dolah FM. Marine algal toxins: origins, health effects, and their increased occurrence. Environ Health Perspect. Mar 2000;108 Suppl 1:133-41. [Medline].

