Ciguatera

Ciguatera is a foodborne illness poisoning in humans caused by eating marine species whose flesh is contaminated with a toxin known as ciguatoxin, which is present in many micro-organisms (particularly, the micro-algae Gambierdiscus toxicus) living in tropical waters. Like many naturally and artificially occurring toxins, ciguatoxin accumulates in lower-level organisms, resulting in higher concentration of the toxin at higher levels of the food chain, an example of biomagnification.^[1] Predator species near the top of the food chain in tropical waters, such as barracuda, moray eel, parrotfish, grouper and amberjack, are most likely to cause ciguatera poisoning, although many other species have been found to cause occasional outbreaks of ciguatera. Ciguatoxin is very heat-resistant, so ciguatoxin-laden fish cannot be detoxified by cooking.^[2]

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History

Originally, ciguatoxin was linked to poison passed to tropical fish through consumption. However, the exact source of the toxin was unknown, and many sources were identified as the culprit. Some of these included the manchineel fruit, cocculus berries, palolo worms, compounds containing copper, pumice, corallina opuntia.

In Northern Australia, where ciguatera is a common problem, there are two commonly believed ways of determining that fish carry significant levels of ciguatoxin. The first belief is that if a piece of fish is contaminated with the toxin, flies will not land on it. The second belief is that the toxin can be detected by feeding a piece of fish to a cat as cats are allegedly highly sensitive to ciguatoxin and will display symptoms. It is not known whether there is any veracity to either belief.

Etymological Roots

It is a generally held theory that ciguatera, as a poisonous substance, was named and identified in Cuba, circa the early 1800s. Local folklore has identified that the etymology stems from a story of an Englishman who caught a barracuda on the Isla de Pinos. After consuming the barracuda, said Englishman became terribly ill. When queried about the origins of his illness, the Englishman claimed to have caught and eaten “a fish, from the seawater.” This gave rise to the name of the ailment as ciguatera, a transliteration into Spanish of the English word seawater.^{[citation needed]}

Distribution

Due to the localized nature of the ciguatoxin-producing micro-organisms, ciguatera illness is only common in tropical waters, particularly the Pacific and Caribbean, and usually is associated with fish caught in tropical reef waters. Ciguatoxin is found in over 400 species of reef fish, and therefore avoidance of consumption of all reef fish (any fish living in warm tropical waters) is the only sure way to avoid exposure to the toxin. Imported fish served in restaurants have been found to contain the toxin and result in illness which often goes unexplained by physicians unfamiliar with a tropical toxin and its characteristic symptoms.^[3] In addition, ciguatoxin has been found in farm-raised salmon.^[4]

Symptoms

Hallmark symptoms of ciguatera include gastrointestinal and neurological effects.^[5] Gastrointestinal symptoms include nausea, vomiting, and diarrhea usually followed by neurological symptoms such as headaches, muscle aches, paresthesia, numbness, ataxia, and hallucinations.^[2] Severe cases of ciguatera can also result in cold allodynia, which is a burning sensation on contact with cold (commonly incorrectly referred to as reversal of hot/cold temperature sensation).^[5] Doctors are often at a loss to explain these symptoms and ciguatera poisoning is frequently misdiagnosed as Multiple Sclerosis.^[6]

Dyspareunia and other ciguatera symptoms have developed in otherwise well males and females following sexual intercourse with partners suffering ciguatera poisoning, signifying ciguatera poisoning may be sexually transmitted.^[7] As diarrhea and facial rashes have been reported in breastfed infants of mothers with ciguatera poisoning, it is likely ciguatera toxins are also transferred into the breast milk.^[8]

The symptoms can last from weeks to years, and in extreme cases lasting as many as 20 years; often leading to long term disability.^[9] Most people do recover slowly over time.^[10] Often patients recover but redevelop symptoms in the future. This relapse/remit characteristic of the disease can be tied to the consumption of nuts, alcohol, eating fish or fish-containing products, eating chicken or eggs, and exposure to fumes such as those of bleach and other chemicals. Exercise is also a possible trigger.^[2]

Treatment

There is no effective treatment or antidote for ciguatera poisoning. The mainstay of treatment is supportive care. Some medications such as the use of Amitriptyline may reduce some symptoms of ciguatera, such as fatigue and paresthesia,^[11] although benefit does not occur in every case.^[12] Also used are steroids and vitamin supplements, but these merely support the body's recovery rather than directly reduce the toxic effects.

Previously mannitol was used for poisoning after one study reported the reversal of symptoms following its use.^[13] Follow up studies in animals^[14] and case reports in humans^[15] also found benefit from mannitol. However, a randomized, controlled, double-blinded, clinical trial of mannitol for ciguatera poisoning did not find any difference between mannitol and normal saline,^[16] and based on this result mannitol is no longer recommended.^[5]

There are a number of antiquated Caribbean homeopathic treatments, as well as ritualistic ones, most of which originated from Cuba and nearby islands. The most common old-time remedy involves bed-rest subsequent to a Guanabana juice enema. Other old-time treatments ranged from directly porting and bleeding the gastrointestinal tract, to ‘cleansing’ the diseased with a dove during a Santeria ritual. The efficacy of these treatments has never been studied or substantiated; nevertheless they are purportedly still used to this day.

See also

• Algal bloom (see "toxic chemicals" in paragraph 2)
• Dinoflagellate (see "neurotoxins" and "red tide" under Ecology and fossils and see "phosphate" under Cautions)
• Red tide

References

• Ciguatera fish poisoning CDC
• Ciguatera fish poisoning—Florida, 1991. MMWR June 4, 1993;42(21):417-8
• Ciguatera fish poisoning—Texas, 1997. MMWR August 28, 1998;47(33):692-4
• Epidemiologic notes and reports ciguatera fish poisoning—Bahamas, Miami. MMWR July 23, 1982;31(28):391-2
• Epidemiologic notes and reports ciguatera fish poisoning—Vermont. MMWR April 25, 1986;35(16):263-4
• Ciguatera fish poisoning
• The Ciguatera Homepage