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8.3.2 Ciguatera toxin

This poisoning result from the ingestion of fish that have become toxic by feeding on toxic dinoflagellate. Gambierdiscus toxicus, which is living around coral reef closely attached to macroalgae. Increased production of toxic dinoflagellates are seen when reefs are disturbed ( hurricanes, blasting of reefs etc.). The toxin ciguatera accumulates in fish that feed on the toxic algae. Toxin can be detected in gut, liver and muscle tissue by means of mouse assay and chromatography. The pharmacological action of ciguatoxin is due to cholinesterase inhibition. According to Taylor (1988), some fish may be able to clear the toxin from their systems. The clinical picture varies but onset time is a few hours after ingestion of toxin.

Gastrointestinal and neurological systems are affected due to the toxin. Duration of illness may be 2-3 days but some may also persist for weeks on even years in severe cases. Death results from circulatory collapse. The most consistently reported symptoms are

1. Moderate to severe neurological disorders that may persist for days, weeks,or months and/or
2. Moderate to severe gastrointestinal disorders of relatively short duration
3. In some cases, death due to respiratory failure.

Cigutera may be caused by over 400 species of marine fishes, including many that are highly priced for food. Five species of organisms namely Gambierdiscus toxicus, Prorocentrum concavum, P. mexicanium, Gymnodinum sanguineum and Gonyaulax polyedra, produced one or more toxic fractions which killed mice within 48 hours.