Big Bend Florida Sportsman Guide

CIGUATERA

Fish Poisoning - The name may be difficult to remember. But if you get this disease, you'll never forget it.

by Donna G. Blythe, M.D., Donald P. de Sylva, PhD,
and Susanne Cramer-Castro, B.A.

Ciguatera fish poisoning is endemic wherever coral reef fishes are a food source. In South Florida, this includes the local coral reef fishing grounds as well as all of the Caribbean. It is the most frequently reported seafood-related disease.

Ciguatera results from the eating of reef fish affected with ciguatoxin. Ciguatoxin originates from a dinoflagellate name Gambierdiscus toxicus which colonizes coral beds. The toxin first affects the coral-grazing fish and is then passed up and through the food chain to the piscivorous fish (i.e., snapper, grouper, amberjack, barracuda) and finally to man. The toxin is not affected by either cooking or freezing, and the affected fish, cooked or raw, is not tainted by bacteria in any way. Typically, the victim states, "It was the best fish I ever tasted."

Ciguatera symptoms were first described in the 1500's by the Spanish explorers to Cuba and were attributed to the ingestion of a small snail which they called cigua.

In the Pacific, the first Tahitian death on the ship Bounty (of the famous Mutiny on the Bounty) was the ship's surgeon after a fish feast: "Old Bacchus died not of drink, as might have been supposed, but of eating a poisonous fish."²

Today a typical scenario would include a delicious family fish dinner at the evening meal, perhaps applauding the successful fisherperson and the culinary skills of the cook. Several hours later (and always in the wee hours of the morning) the rather sudden onset of gastrointestinal complaints awakens one after another of the fish-feasters. Nausea, vomiting, cramping, abdominal pain, and diarrhea suggest that perhaps the fish was spoiled.

Intense itching, joint and muscle pain, tingling of the lips, burning or pain when cold liquids are touched or drank will usually bring at least the more affected victims to the emergency room, later to find most if not all the others who also enjoyed the fish were variably affected. With the exception of ice applied to the tongue or fingertips being interpreted as a burning sensation, there are no clinical signs.

There is no diagnostic laboratory test. Diagnosis rests with the history of ingestion of reef fish followed by gastointestinal and bizarre neurological complaints all within a few hours' time frame. The coup de grace in diagnosis is the observance that the symptoms and intensified after the consumption of an alcoholic beverage.

As an aside, breast-feeding infants have been reported to exhibit an unusual degree of "fussiness" if their mothers have been victims of ciguatera and it is believed that the ciguatoxin is excreted in breast milk.

Treatment has traditionally been supportive and disappointing. This has included antihistamines, amitriptyline, calcium gluconate, pyridoxine, corticosteroids, atropine and vitamin B. Recently ciguatera has been successfully treated with IV mannitol.⁴ The usual dose is 1 gram of mannitol per kilogram victim's body weight infused intravenously either as a 20 percent mannitol solution or added to .9 NaCl or Ringer's solution.

For help with this treatment, call the Ciguatera Hotline at (305) 361-4619 or (305) 661-0774.

Ciguatoxin acts on the sodium channels, thereby causing changes in the electrical potential and permeability of cells. It is believed that mannitol might compete at the cell membrane and/or render the ciguatoxin inert. A scavenger effect is also possible and mannitol might also increase elimination of th toxin via its secondary diuretic effect.

Some of the symptoms can recur hours after treatment, suggesting further ciguatoxin absorption from the gastrointestinal tract; retreatment has been successful in these cases.

Untreated, ciguatera is usually a self-limited disease lasting one to two months. However, symptoms can persist months to years, causing great anguish.

Mannitol is believed to abbreviate if not abate the clinical sequelae of ciguatera fish poisoning. Preliminary evidence suggests that the earlier a victim is diagnosed and treated, the more likely the success with IV mannitol.

In the experience of the first author, mannitol has been shown to be safe and effective in patients aged 4 to 72 years old, even when given to an insulin-dependent diabetic.

Anecdotally an 8-month-old breast-feeding infant was apparently successfully treated recently in the Marshall Islands, where the use of IV mannitol in ciguatera was pioneered and now is the site of a NIH double-blind study on the use of IV mannitol in ciguatera fish toxicity.

Presently, there is no commercial assay available to test potentially toxic fish. A rapid enzyme immuno-assay for the detection of ciguatoxin in contaminated fish is currently being evaluated.⁵ To be marketable the test would have to be effective, inexpensive, and simple to use. Until this is available, avoidance of potentially toxic fish makes sense. This includes large predatory reef fish (greater than 5 pound snapper to 5 pound grouper or amberjack or greater than 2 pound hogfish seems a realistic guideline). Yellowtail snapper and dolphin (mahi-mahi) are safe fish to eat at any size in the South Florida and Caribbean areas.

Also, always know what kind of fish you are eating. Unsuspecting tourists have been known to have been sold barracuda thinking they are buying red snapper from an artful seaside fish peddler. A restaurant can "switch" a large grouper fillet for a yellowtail snapper, and most fish fanciers wouldn't know the difference. Make sure the fish is served whole (OK, headless) whenever possible. A fish small enough to fit on your plate is probably safe.
 

REFERENCES

1) JAMA. Laurence et al, 1980, 244:254-258
2) "Mutiny on the Bounty," Nordoff and Hall, 1932, pg. 94
3) JAMA, Bylthe and de Sylva, Oct. 24/31, 1990
4) JAMA, Palafox et al, May 13, 1988
5) Hokama, Toxicon, 1983:21-817