Fish Poisoning and Shellfish Poisoning

Ciguatera poisoning is responsible for 20% of all fish-related foodborne illnesses (approximately 16,000 cases annually in the United States with 300 hospitalizations) and may result from eating any of > 400 species of fish from the tropical reefs of Florida, the West Indies, or the Pacific, where a dinoflagellate produces a toxin that accumulates in the flesh of the fish (1). Older fish and large fish (eg, grouper, snapper, kingfish) contain more toxin. No known processing procedures, including cooking, are protective, and flavor is unaffected. Poisoning can occur after eating fresh or frozen fish. No commercial product is available to test for ciguatoxin in fish.

Perinatal transmission may occur and ciguatoxin is secreted in breast milk. Pregnant and nursing women should avoid consuming the suspect fish.

Symptoms may begin 2 to 8 hours after eating. Abdominal cramps, nausea, vomiting, and diarrhea last 6 to 17 hours; then, pruritus, paresthesias, headache, myalgia, reversal of hot and cold sensation, and face pain may occur. For months afterward, unusual sensory phenomena and nervousness may cause debilitation (2). Diagnosis is clinical.

IV mannitol has been suggested as a treatment, but no clear benefit has been shown (IV mannitol has been suggested as a treatment, but no clear benefit has been shown (3, 4). Gabapentin, amitriptyline, nifedipine and pregabalin have been used to treat the long-term neurologic symptoms with varying degrees of success (). Gabapentin, amitriptyline, nifedipine and pregabalin have been used to treat the long-term neurologic symptoms with varying degrees of success (5, 6, 7, 8).

Scombroid poisoning is caused by high histamine levels in fish flesh due to bacterial decomposition after the fish is caught. Commonly affected species include:

• Tuna

• Mackerel

• Bonito

• Skipjack

• Mahi mahi

The fish may taste peppery or bitter. Facial flushing and possibly nausea, vomiting, epigastric pain, and urticaria occur within a few minutes of eating and resolve within 24 hours. Symptoms are often mistaken for those of a seafood allergy. Unlike other fish poisonings, this poisoning can be prevented by properly storing the fish after it is caught (9). Histamine poisoning has also been reported after eating Swiss cheese from bacterial contamination of raw milk prior to processing (10).

Diagnosis is clinical. If testing of the remaining fish is possible, histamine levels greater than 100 mg/100 g confirm the diagnosis.

Treatment may include H1 blockers and H2 blockers. Severe symptoms (airway edema, bronchospasm, or distributive shock) may require treatment for anaphylaxis with epinephrine and vasopressors. with epinephrine and vasopressors.

Tetrodotoxin poisoning is most commonly due to eating the puffer fish (fugu), a Japanese delicacy, but > 100 freshwater and saltwater species contain tetrodotoxin (11). Early symptoms include paresthesias in the face and extremities, followed by increased salivation, nausea, vomiting, diarrhea, and abdominal pain. Potentially fatal respiratory paralysis can also occur. Treatment is supportive care with attention to ventilatory assistance until the toxin is metabolized, which may take days. Case reports suggest anticholinesterases like edrophonium or neostigmine may help reverse some of the paralytic neurologic effects but data are inconclusive (). Early symptoms include paresthesias in the face and extremities, followed by increased salivation, nausea, vomiting, diarrhea, and abdominal pain. Potentially fatal respiratory paralysis can also occur. Treatment is supportive care with attention to ventilatory assistance until the toxin is metabolized, which may take days. Case reports suggest anticholinesterases like edrophonium or neostigmine may help reverse some of the paralytic neurologic effects but data are inconclusive (12).

The toxin cannot be destroyed by washing, cooking, or freezing.

Paralytic shellfish poisoning can occur from June to October, especially on the Pacific and New England coasts, when mussels, clams, oysters, and scallops are contaminated by the poisonous dinoflagellate responsible for red tide. This dinoflagellate produces the neurotoxin saxitoxin, which is resistant to cooking, freezing, or marinating. Contaminated seafood appears, smells, and tastes normal. Circumoral paresthesias occur 5 to 30 minutes after eating. Nausea, vomiting, and abdominal cramps then develop, followed by muscle weakness. Treatment is supportive. Untreated respiratory paralysis may be fatal; for survivors, recovery is usually complete (13).

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3. 3. Friedman MA, Fleming LE, Fernandez M, et al. Ciguatera fish poisoning: treatment, prevention and management. Mar Drugs. 2008;6(3):456-479. doi:10.3390/md20080022

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8. 8. Brett J, Murnion B. Pregabalin to treat ciguatera fish poisoning. . Pregabalin to treat ciguatera fish poisoning.Clin Toxicol (Phila). 2015;53(6):588. doi:10.3109/15563650.2015.1052499

9. 9. Hungerford JM. Scombroid poisoning: a review. Toxicon. 2010;56(2):231-243. doi:10.1016/j.toxicon.2010.02.006

10. 10. Taylor SL, Stratton JE, Nordlee JA. Histamine poisoning (scombroid fish poisoning): an allergy-like intoxication. J Toxicol Clin Toxicol. 1989;27(4-5):225-240. doi:10.3109/15563658908994420

11. 11. Bane V, Lehane M, Dikshit M, et al. Tetrodotoxin: chemistry, toxicity, source, distribution and detection. Toxins (Basel). 2014;6(2):693-755. Published 2014 Feb 21. doi:10.3390/toxins6020693

12. 12. Liu SH, Tseng CY, Lin CC. Is neostigmine effective in severe pufferfish-associated tetrodotoxin poisoning?. . Is neostigmine effective in severe pufferfish-associated tetrodotoxin poisoning?.Clin Toxicol (Phila). 2015;53(1):13-21. doi:10.3109/15563650.2014.980581

13. 13. Etheridge SM. Paralytic shellfish poisoning: seafood safety and human health perspectives. Toxicon. 2010;56(2):108-122. doi:10.1016/j.toxicon.2009.12.013