Ciguatera

• Epidemiology: The most common fish-associated nonbacterial food poisoning in the United States, with most cases occurring in Florida and Hawaii
  • In all, 20,000-50,000 people are affected annually, although 90% of cases may go unreported.
  • Three-quarters of cases involve barracuda, snapper, jack, or grouper found in the Indian Ocean, the South Pacific, and the Caribbean Sea.
• Pathogenesis: Ciguatera toxin acts on neuron voltage-gated sodium channels and is created by marine dinoflagellates, whose consumption by fish allows the toxin to accumulate in the food chain. Three major ciguatoxins-CTX-1, -2, and -3-are found in the flesh and viscera of ciguateric fish, are typically unaffected by external factors (e.g., heat, cold, freeze-drying, gastric acid), and do not generally affect the fish (e.g., odor, color, or taste).
• Clinical features: Pts typically develop symptoms within 2-6 h, with virtually all pts affected within 24 h. The diagnosis is made on clinical grounds.
  • Symptoms can be numerous (>150 reported) and include diarrhea, vomiting, abdominal pain, neurologic signs (e.g., paresthesias, weakness, fasciculations, ataxia), maculopapular or vesicular rash, and hemodynamic instability.
  • A pathognomonic symptom-reversal of hot and cold tactile perception-develops within 3-5 days and can last for months.

Paralytic Shellfish Poisoning

• Etiology: Induced by ingestion of contaminated filter-feeding organisms (e.g., clams, oysters, scallops, mussels) that concentrate water-soluble, heat- and acid-stable chemical toxins
  • The best-characterized and most frequently identified paralytic shellfish toxin is saxitoxin.
  • Paralytic shellfish toxins cannot be destroyed by ordinary cooking.
• Clinical features: Oral paresthesias (initially tingling and burning, later numbness) develop within minutes to hours after ingestion of contaminated shellfish and progress to involve the neck and distal extremities. Flaccid paralysis and respiratory insufficiency may follow 2-12 h later; 12% of pts die, most within 18 h.

Scombroid

• Etiology: Histamine intoxication due to bacterial decomposition of inadequately preserved or refrigerated scombroid fish (e.g., tuna, mackerel, saury, needlefish, wahoo, skipjack, and bonito)
  • This syndrome can also occur with nonscombroid fish (e.g., sardines, herring, dolphinfish, amberjack, and bluefish).
  • Affected fish typically have a sharply metallic or peppery taste but may be normal in appearance and flavor.
  • Because of uneven distribution of decay within the fish, not all people who eat an affected fish will become ill.
• Clinical features: Within 15-90 min of ingestion, pts present with oral tingling, mild abdominal pain, and nausea. Pts with severe cases develop flushing (exacerbated by UV exposure), pruritus, urticaria, angioneurotic edema, bronchospasm, GI symptoms, and hypotension.
  • Symptoms generally resolve within 8-12 h.
  • May be worse in pts concurrently taking isoniazid because of inhibition of GI tract histaminases.