Ciguatera fish poisoning is caused by which organism?

• A. Gambierdiscus toxicus
• B. Karenia brevis
• C. Pryodinium bahamense
• D. Microcystis aeruginosa

Answer: (A)

Ciguatera poisoning comes from toxins produced by certain marine dinoflagellates that live on coral reefs in warm tropical waters. The organism most responsible is Gambierdiscus toxicus, which makes ciguatoxins that accumulate up the food chain when reef fish eat algae and smaller organisms containing the toxins. Humans ingest these contaminated fish and can develop a range of neurologic and gastrointestinal symptoms because ciguatoxins disrupt nerve signaling by affecting sodium channels. Cooking does not destroy these toxins, so preparation methods don’t prevent illness.

Other organisms listed are linked to different toxins or syndromes—for example, brevetoxins from Karenia brevis cause neurotoxic shellfish poisoning, saxitoxins from Pyrodinium bahamense cause paralytic shellfish poisoning, and Microcystis aeruginosa produces microcystins in freshwater environments.