Neurotoxic shellfish poisoning

Neurotoxic shellfish poisoning (NSP) is caused by the consumption of brevetoxins, which are marine toxins produced by the dinoflagellate Karenia brevis (among several others).

Algal blooms are a naturally-occurring phenomenon, however their frequency has been increasing in recent decades at least in-part due to human activities, climate changes, and the eutrophication (over-abundance of plant nutrients as a result of agricultural runoff, deforestation, river bed erosion, etc.)

[1][2][3][4] HABs have been occurring for all of documented history, evidenced by the Native Americans' understanding of the dangers of shellfish consumption during periods of marine bioluminescence (a phenomenon observed during algal blooms).

[4] Notably, brevetoxins are tasteless and odorless and cannot be eradicated by rinsing, cleaning, cooking, freezing, or application of acid.

[4] Additionally, brevetoxins can bind a separate site on VGSCs, causing release of neurotransmitters (such as acetylcholine), resulting in tracheal smooth muscle contraction and widespread mast cell degranulation.

[6] Diagnosis of NSP is made based on clinical presentation as well as history findings including recent consumption of shellfish.

[4] Though public health policy differs by state, measures are taken to prevent shellfish poisoning outbreaks.

Karenia brevis , the primary dinoflagellate organism responsible for brevetoxin production.
Red Tide caused by dinoflagellates. Picture taken off the coast of San Diego, California.
Filter-feeding mollusks, such as oysters, concentrate dinoflagellates and their toxins in their flesh due to the way they feed. When the shellfish are then eaten by humans, high doses of the toxins may be consumed.
Brevetoxin A, a group of neurotoxins isolated from the marine dinoflagellate Karenia brevis (formerly Gymnodinium breve ).
Basic schematic of sodium channel function. Brevetoxins bind to the voltage-gated sodium channel and induce a channel-mediated sodium ion influx. This results in neuroexcitation, membrane depolarization, and spontaneous nerve firing.