domoic

Domoic, in common usage referring to domoic acid, is a naturally occurring marine neurotoxin produced by certain diatoms, especially species of Pseudo-nitzschia. It bioaccumulates in filter-feeding shellfish such as mussels, clams, and scallops, and can also concentrate in some fish and crustaceans that feed on contaminated organisms. Harmful algal blooms that produce domoic acid are influenced by environmental factors such as nutrient availability and sea-temperature changes.

Domoic acid acts as an excitotoxin in the human nervous system. It binds to kainate and, to a lesser extent, AMPA receptors in the brain, causing excessive neuronal stimulation and potential cell damage. The hippocampus is particularly affected, leading to memory impairment and disorientation known as amnesic shellfish poisoning (ASP). Symptoms typically emerge within hours and may include nausea, vomiting, abdominal cramps, headache, dizziness, confusion, and memory loss; severe cases can involve seizures, coma, or death. There is no antidote, and treatment is supportive.

The toxin is heat-stable, so cooking does not reliably neutralize it. Public health protection relies on monitoring programs that test shellfish for domoic acid; harvest areas exceeding regulatory limits are closed. Detection methods include laboratory techniques such as LC-MS/MS and immunoassays. Regulatory limits vary by jurisdiction but commonly set action levels around 20 micrograms per gram (20 ppm) in shellfish flesh.

Domoic acid was first linked to human illness during a 1987 outbreak in Prince Edward Island, Canada, prompting ongoing surveillance and regulatory responses to mitigate ASP risk.