CIGUATERA

Fish Poisoning

by Donna G. Blythe, M.D., Donald P. de Sylva, PhD,

and Susanne Cramer-Castro, B.A. (edited and supplemented by WMG)

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 the dinoflagellate Gambierdiscus toxicus which is a benthic species that is occasionally common on reef algae. Not all examples of G. toxicus exhibit ciguatoxin, suggesting that it is strain-dependent. This makes the appearance of ciguatoxic fish locations temporary and difficult to predict. To make matters worse, there is no FDA-approved method of diagnosing ciguatoxin, although a company in Hawaii is selling test kits (see http://www.cigua.com/). The toxin first appears in coral-grazing fish and is then passed up and magnified through the food chain to the piscivorous fish (i.e., snapper, grouper, barracuda) and finally to humans. This phenomenon of concentrating a toxin by way of the food chain is called biological magnification. That said, there are also some examples of ciguatoxin poisoning after eating large acanthurids or siganids, but the occurrence of ciguatoxin in large predators is much more common. The toxin is water insoluble (see structure below), and is heat-stable, i.e., not affected by either cooking or freezing. The affected fish, cooked or raw, is not tainted by bacteria in any way, and the victim typically 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."

Several hours after ingestion of the ciguatoxic fish (and always in the wee hours of the morning), there is a rather sudden onset of gastrointestinal complaints. 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.

` 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 intravenous mannitol. 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 0.9 NaCl or Ringer's solution.

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 the 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.

TREATMENT

Mannitol Administration

Route: Intravenous

Dosage:

1 gm/kg Body Weight

Infusion Rate: 250 - 350 cc/hr

Total Infusion Time: 3-4 hrs

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 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.

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. 5To 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.

VOLUNTEERED SYMPTOMS

from ciguatera victims

Symptoms worsened with alcohol, sweets, nuts, or coffee ingestion

Headache

Double Vision/Eye Irritation

Diminished Memory

Metallic Taste

Exhaustion

Palpitations/"Heart Attack"

Tremor

Rectal Burning/Itching

Burning Urinating

Vaginal Pain/Tingling

Pain - Penis/Scrotum

Pain with Intercourse

Percentage of symptoms reported by ciguatera victims.

Gastro-Intestinal 100%

Itching 100%

Tingling-Numbness 100%

Muscular-Skeletal 100%

Reversal Cold/Hot 100%

Dizzyness-Vertigo 50%

Difficulty Breathing 50%

Difficulty Urinating 33%

Skin Rash-Eruption 16%

Paralysis 0%

Death 0%

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

Ciguatoxin molecule