Neurotoxic Shellfish Poisoning

Causative organism: Karenia brevis

Toxins produced: Brevetoxins

Neurotoxic Shellfish Poisoning (NSP) produces an intoxication syndrome nearly identical to that of ciguatera in which  gastrointestinal and neurological symptoms predominate. In addition, formation of toxic aerosols by wave action can produce respiratory asthma-like symptoms. No deaths have been reported and the syndrome is less severe than ciguatera, but nevertheless debilitating. Unlike ciguatera, recovery is generally complete in a few days. They close on the basis of cell counts, but cannot open until toxin levels are below the threshold for two measurements, at least one week apart.  Monitoring programs (based on K. brevis cell counts) generally suffice for preventing human intoxication, except when officials are caught off-guard in previously unaffected areas.

U.S. Finfish, Shellfish and Wildlife Affected by NSP
Harmful Algal Species
Geographic Area
Affected Organisms*
Karenia brevis

Gulf of Mexico
South Atlantic Bight

Bay scallops, surf clams, oysters, southern quahogs, coquinas


Many commercial and recreational species of fish, sea birds, sea turtles, manatees, dolphins

*Found to contain algal toxins, or to be adversely affected by toxic or harmful marine algae.

Medical Community
NSPNeurotoxic Shellfish Poisoning
Additional Information on CFP including: Background, Clinical Presentation, Diagnosis, Management and Treatment, Chemical Structure, and Molecular Mechanism of Action.

Additional Resources
Neurotoxic Shellfish Poisoning
Sharon M. Watkins, Andrew Reich, Lora E. Fleming, Roberta Hammond
    DOI: 10.3390/md20080021

Last updated: October 12, 2018