Paralytic shellfish poisoning

Background

• Caused by ingestion of toxin-contaminated bivalve shellfish and crustaceans
  • Most commonly involves clams, mussels, whelks, moon-shells, dogwinkles, oysters, whole scallops, and crab and lobster hepatopancreas
  • Toxin can remain for up to a year in some shellfish
• Results from accumulation of toxin after algal blooms of dinoflagellates, which usually occurs in the warmer months
  • Toxin accumulates in specific tissues, such as the siphon, neck, and gills of butterclams

Clinical Manifestations

• Incubation period of 1 hour (range 30 minutes to 3 hours)
• Severity clinical illness and speed of progression depends on amount of toxin ingested
• Paresthesias and numbness spreading from lips and mouth to face, neck, and extremities
• Dizziness, headaches, nausea, vomiting
• Paresis or paralysis
• In severe cases, respiratory depression and death

Diagnosis

Case Definition

• Clinical illness is defined as: neurological symptoms such as paresthesia and/or paralysis involving the mouth and extremities, which may be accompanied by gastrointestinal symptoms
• At-risk shellfish include filter-feeding molluscan bivalve shellfish, such as clams, mussels, scallops (digestive tissues), oysters, cockles, and whelks, and the hepatopancreas of crab

Confirmed Case

• Clinical illness within 24 hours of eating at-risk shellfish, and
• Detection of saxitoxin or related toxins in samples of shellfish that were consumed by an individual meeting the clinical case definition, in edible tissues in excess of 0.8 mg/kg, or
• Detection of saxitoxin in urine or feces collected within 24 hours of exposure and illness, or
• Detection of high levels of dinoflagellates (Alexandrium, Gymnodinium, and Pyrodinium species) associated with shellfish poisoning in water from which epidemiologically related shellfish were gathered

Probable Case

• Clinical illness within 12 hours of consumption of at-risk shellfish and in the absence of other known causes

Management

• Supportive care

Prevention

• Monitoring for saxitoxin and other related toxins in shellfish