Ciguatera fish poisoning — DTM&H MCQ

Correct answer: E — Ciguatera fish poisoning

The correct answer is E, Ciguatera fish poisoning. The stem describes the classic triad of gastrointestinal symptoms (vomiting, diarrhoea) with onset within hours of eating large reef fish from a tropical or Caribbean location, followed by neurological features including paraesthesiae and, most tellingly, reversal of hot and cold sensation (thermal allodynia). This combination is considered almost pathognomonic for ciguatoxin ingestion, which acts on voltage-gated sodium channels in peripheral nerves. Large predatory reef fish (grouper, snapper, barracuda) bioaccumulate ciguatoxin from dinoflagellates up the food chain, and the toxin is heat stable, so normal cooking does not inactivate it. A UK case report confirmed ciguatera poisoning in patients who developed vomiting, diarrhoea, myalgia and paraesthesia after eating imported reef snapper, matching this clinical pattern. Why the other options are wrong: C. Scombroid poisoning: caused by histamine accumulation in poorly refrigerated fish (mackerel, tuna), producing flushing, urticaria and headache within minutes, not paraesthesiae or temperature reversal. D. Cholera: causes profuse watery diarrhoea from Vibrio cholerae toxin via contaminated water, not fish ingestion, and does not cause sensory disturbance or thermal reversal. A. Pufferfish tetrodotoxin poisoning: tetrodotoxin also blocks sodium channels causing paraesthesiae, but pufferfish are not typically eaten as large reef fish in the Caribbean, and thermal reversal is not the classic feature; progressive ascending paralysis is. B. Aflatoxin poisoning: results from chronic ingestion of mould-contaminated grains or nuts (Aspergillus), causing hepatotoxicity and carcinogenesis, unrelated to acute fish ingestion or neurological symptoms. Key point: Gastrointestinal symptoms plus paraesthesiae and pathognomonic hot/cold sensory reversal after eating large tropical reef fish equals ciguatera poisoning.

Reference: Turner AD et al, First Confirmed Occurrence of Ciguatera Poisoning in the UK from Imported Pinjalo Snapper, Marine Drugs 2025 (Cefas, UK); https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11857775/