Shellfish Poisoning

Shellfish poisoning, recognized for several hundred years, is infection resulting from the ingestion of shellfish contaminated with a virus or bacteria. Shellfish poisoning includes four primary syndromes that are commonly caused by ingestion of bivalve mollusks (oysters, clams, mussels, and scallops) but may also result from ingestion of shrimp, crabs, and salted raw fish. These syndromes include paralytic shellfish poisoning (PSP), neurologic shellfish poisoning (NSP), diarrheal shellfish poisoning (DSP), and amnesic shellfish poisoning (ASP). PSP affects children more often than adults and is considered the most severe of the four syndromes, with a mortality rate of 1% to 12% in isolated outbreaks. All reported deaths from ASP have been in elderly patients. NSP and DSP have not been known to cause any deaths.

Causes

Bivalve mollusks accumulate toxins produced by microscopic algae. Offending toxins include saxitoxin (PSP), brevetoxin (NSP), okadaic acid (DSP), and domoic acid (ASP). These toxins are not inactivated by regular cooking and are also water soluble. Poisoning generally occurs after ingestion, although brevetoxin may become aerosolized by the surf. Outbreaks occur more often in warm weather but have decreased in the United States as a result of education and regulation by public health officials. Hepatitis A virus, Norwalk virus, Vibrio parahaemolyticus infection, and Vibrio vulnificus infection have also been implicated in shellfish toxicity.

Complications

Complications from PSP include respiratory failure and death. Complications from ASP include seizures, coma, hemiparesis, severe cognition dysfunction, and death. Dehydration may occur with all syndromes.

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