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National Collaborating Centre
for Environmental Health Centre de collaboration nationale
en santé environnementale

What is PSP?
Paralytic shellfish poisoning (PSP) occurs following the ingestion of bivalve shellfish (e.g., mussels, oysters, clams, and scallops), gastropods (abalone) and crustaceans (crab and lobster) containing biotoxins.1,2 The distribution of PSP biotoxins is worldwide, with biotoxins being produced by toxic marine micro-organisms that accumulate in exposed shellfish.1-3 There are more than 20 different PSP biotoxins, collectively called saxitoxins.3
What are the symptoms of PSP?
Paralytic shellfish poisoning can be life threatening; consequently, public health response to suspect PSP cases requires a timely and coordinated effort. Time between ingestion and onset of clinical effects ranges from 15 minutes to 10 hours, with median time being one hour.1,2 Initial symptoms include tingling or numbness of the tongue and lips that spreads to the face, neck, fingers, and toes. Headache, nausea, vomiting, diarrhea, hyper-salivation, fever, and diaphoresis may also occur. Exposed individuals may describe a feeling of dizziness or “floating,” owing to distortion of sensation and proprioception. Subsequent symptoms are generalized paraesthesia, arm and leg weakness, and ataxia. Rapid development of paralysis and respiratory failure may occur within 24 hours in severe cases. The rate of symptom progression is correlated with poisoning severity. In patients with mild to moderate poisoning, effects resolve over 2-3 days, but in severe cases, weakness may persist for up to a week. In most fatalities, death occurs rapidly, typically within 12 hours.
Illness information
Four persons ate raw oysters (quantity range 4-10 /person) and cooked Manila clams (quantity range 5-20/person) on June 17, 2010. Symptom onset occurred within 15 minutes with four out of four persons reporting tingling of the mouth and fingers. Symptoms resolved by early evening in all but one person who remained symptomatic the following morning with tingling in their toes. This individual was admitted to a hospital emergency department on June 18, 2010.
What can be done for individuals exhibiting the above symptoms and who are thought to be suspect-PSP illness cases?
There is no antidote for PSP, and all cases require immediate medical attention. Management of clinically ill individuals is primarily supportive. Close observation in the early stages of poisoning is critical so that any progression to paralysis and/or respiratory failure can be recognized and treated immediately and effectively.