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U.S. National Office for Harmful Algal Blooms

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Paralytic Shellfish Poisoning

Causative organisms: Alexandrium spp.,Gymnodinium catenatum, Pyrodinium bahamense

Toxins produced: Paralytic Shellfish toxins (PST), saxitoxin analogs, spirolides, gymnodimines, goniodomins

Paralytic Shellfish Poisoning (PSP), like ASP, is a life threatening syndrome associated with the consumption of seafood products contaminated with the neurotoxins known collectively as saxitoxins (STXs). Symptoms are purely neurological and their onset is rapid, appearing as early as ten minutes to three hours following consumption of contaminated food. Duration of effects is generally a few days in non-lethal cases. Symptoms include tingling, numbness, and burning of the perioral region, ataxia, giddiness, drowsiness, fever, rash, and staggering. These symptoms can be accompanied by abdominal pain, nausea, vomiting and diarrhea.  The most severe cases result in respiratory arrest within 24 hours of consumption of the toxic shellfish. If the patient is not breathing or if a pulse is not detected, artificial respiration and CPR may be needed as first aid. There is no antidote, supportive therapy is the rule and survivors recover fully. PSP is prevented by large-scale proactive monitoring programs (assessing toxin levels in mussels, oysters, scallops, clams) and rapid closures of suspect or demonstrated toxic areas to harvest.  There are now over 30 recognized morphological species of Alexandrium, and around half of these species are known to produce toxins.

U.S. Finfish, Shellfish and Wildlife Affected by PSP

U.S. Finfish, Shellfish and Wildlife Affected by PSP
Harmful Algal SpeciesGeographic AreaAffected Organisms*
Alexandrium spp.Northern Atlantic and Pacific Coast of North America, Alaskan ArcticMussels, surfclams, softshell clams, sea scallops, butterclams, ocean quahogs, oysters, gastropods, lobsters, crabs.
Herring, salmon, menhaden, sandlance, mackerel, and possibly other fish species.
Whales, sea lions+, sea otters+, sea birds.
Squid, zooplankton, and other benthic invertebrates.
*Found to contain algal toxins, or to be adversely affected by toxic or harmful marine algae.
+Causative algae implicated, not confirmed.

Medical Community

Paralytic Shellfish Poisoning
Additional Information on PSP including: Background, Clinical Presentation, Diagnosis, Management and Treatment, Chemical Structure, and Molecular Mechanism of Action.

Additional Resources

  • Deeds, J., Landsberg, J., Etheridge, S., Pitcher, G. and Longan, S., 2008. Non-traditional vectors for paralytic shellfish poisoning. Marine drugs, 6(2), pp.308-348; DOI: 10.3390/md20080015.
  • Etheridge, S.M., 2010. Paralytic shellfish poisoning: seafood safety and human health perspectives. Toxicon, 56(2), pp.108-122; https://doi.org/10.1016/j.toxicon.2009.12.013
  • Kodama, M. Paralytic shellfish poisoning toxins: Biochemistry and origin Aqua-BioSci. Monogr. 2010, 3, 1–38.