Ciguatera fish poisoning — DTM&H MCQ

Correct answer: E — Ciguatera poisoning

Ciguatera poisoning (E) is correct because it produces a combined gastrointestinal and neurological syndrome after eating tropical reef fish, with paraesthesiae and the classic pathognomonic feature of temperature (hot-cold) sensory reversal. The toxin, ciguatoxin, is produced by the dinoflagellate Gambierdiscus toxicus and accumulates up the reef food chain in large predatory reef fish (barracuda, grouper, snapper, moray eel), which is consistent with a Caribbean reef-fish exposure. Vomiting typically occurs within hours, followed by neurological features including perioral and limb paraesthesiae, pruritus and the characteristic cold allodynia (cold objects feel hot and vice versa), which can persist for weeks. Ciguatoxin is heat stable, so normal cooking does not destroy it, reinforcing that any large reef fish from an endemic area carries risk regardless of preparation. Why the other options are wrong: B. Amoebiasis: causes bloody diarrhoea and colitis from faecal-oral protozoal spread, unrelated to fish ingestion and with no paraesthesiae or thermal sensory disturbance. A. Scombroid poisoning: results from histamine accumulation in improperly stored fish (tuna, mackerel) causing a histaminergic reaction (flushing, urticaria, headache, diarrhoea) within minutes, but it does not cause paraesthesiae or temperature sensation reversal. D. Cholera: causes profuse watery (rice-water) diarrhoea from Vibrio cholerae via contaminated water, not fish, with no neurological or sensory features. C. Tetrodotoxin poisoning: linked to pufferfish (fugu), not typical reef fish, and causes rapidly progressive descending paralysis and perioral numbness rather than temperature reversal. Key point: Vomiting plus paraesthesiae plus reversal of hot-cold sensation after reef fish is the classic triad that identifies ciguatera poisoning.

Reference: Travel Doctor Network (UK), Ciguatera Fish Poisoning, Travel Health & Advice, https://www.traveldoctor.network/risk/ciguatera-fish-poisoning/