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

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

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

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

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