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Diseases & Topics

Shellfish-Associated Toxins

Shellfish poisoning is a type of food poisoning people can get when they eat shellfish that have eaten toxin-producing algae. The 20 toxins responsible for paralytic shellfish poisonings (PSP) are all derivatives of saxitoxin. Paralytic Shellfish Poisoning (PSP), Diarrheic Shellfish Poisoning (DSP), Neurotoxic Shellfish Poisoning (NSP) and Amnesic Shellfish Poisoning (ASP) are the forms detected most frequently.

Eating contaminated shellfish results in a wide variety of symptoms, depending upon the toxins(s) present, their concentrations in the shellfish, and the amount of contaminated shellfish consumed.

In PSP (Paralytic Shellfish Poisoning), the effects are predominantly neurological and include tingling, burning, numbness, drowsiness, incoherent speech and respiratory paralysis, which requires prompt medical intervention.

DSP (Diarrheic Shellfish Poisoning) is usually a generally mild gastrointestinal disorder involving nausea, vomiting, diarrhea, and abdominal pain accompanied by chills, headache and fever.

NSP (Neurotoxic Shellfish Poisoning) causes both gastrointestinal and neurological symptoms, including tingling and numbness of lips, tongue and throat; muscular aches; dizziness; reversal of the sensations of hot and cold; diarrhea; and vomiting.

ASP (Amnesic Shellfish Poisoning) causes gastrointestinal disorders (vomiting, diarrhea, abdominal pain) and neurological problems (confusion, memory loss, disorientation, seizure or coma). Elderly people are most at risk from this type of shellfish poisoning.

Shellfish poisoning can be prevented by avoiding potentially contaminated bivalve (two-shell) mollusks. This is particularly important in areas during or shortly after "red tides." Travelers to developing countries should avoid eating all shellfish because they carry a high risk of viral and bacterial infections. Marine shellfish toxins cannot be destroyed by cooking or freezing.

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