October 2002

By Nathan Welton

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| The Ciguatocix Zone includes many of the world's most popular dive destinations. Yellow areas = Ciguatera occurs; Orange areas = Ciguatera endemic.|
If you've ever burned yourself with an ice cube after eating barracuda, you may have been a victim of ciguatera poisoning, an illness caused by eating predatory reef fish. One of the symptoms of ciguatera poisoning is sensory reversal--confusing hot things as cold and vice versa.

Ciguatera poisoning occurs in waters between latitudes 35 degrees north and 35 degrees south. That means it's prevalent in some of the world's most popular dive locations, and to confound matters, some of its symptoms are easily confused with decompression sickness. At least 50,000 people who live in or visit tropical areas of the world will become ill with ciguatera this year. Most symptoms disappear within days, but in severe cases, the symptoms can last from weeks to months.

Ciguatera poisoning is caused by consuming tropical marine fish that have accumulated a toxin that originates from certain species of algae. Ciguatoxin concentrates in the tissues of tropical predators--barracuda, snapper, groupers, amberjack, sea bass and mackerel--when they eat grazers that feed on the algae. These small fish are in turn eaten by larger fish, and so on up the food chain. And at the top of that chain is often an unsuspecting diver who wanders into a seafood restaurant after a day of diving.

There's no easy way to tell if the fish on your dinner plate is infected. The poison has no effect on infected creatures, and the toxin itself is odorless, tasteless and unaltered by cooking.

Ciguatera Symptoms

Dr. Lora Fleming, a ciguatera expert at the University of Miami School of Medicine, says problems usually begin with symptoms of classic food poisoning: diarrhea, vomiting and nausea. However, without treatment, the symptoms progress into bizarre neurological disorders. "Generally, your nerves start acting up and sending mixed information," says Fleming. "You feel like bugs are biting your legs or your teeth hurt." In addition to confusing hot and cold, other ciguatera symptoms include pain during urination and painful sexual intercourse.

Ciguatera and DCS

But what can be most perplexing is that victims suffer some combination of vertigo, weakness, fatigue, numbness and tingling, which are similar to symptoms associated with decompression sickness. Plus, the symptoms of both illnesses can be delayed for up to a day, though decompression sickness usually appears within six hours of surfacing and ciguatera usually begins 30 minutes to four hours after a meal.

To differentiate between ciguatera poisoning and DCS, look for ciguatera-specific symptoms, including diarrhea and no headache (decompression sickness is the other way around). According to Fleming, sensory problems like temperature reversal are highly indicative of ciguatera poisoning. Fleming says that because ciguatera's attack rate is nearly 100 percent, victims should look for afflicted dining buddies. Of course, be sure to ask dive operators which fish to avoid eating locally, and if you become sick, seek medical attention promptly and tell the doctor your dive profile and your eating history.

Treating Ciguatera

Fleming says the best treatment for individuals seriously ill with ciguatera poisoning is a drug called mannitol, which is given intravenously and can resolve symptoms within minutes, even when the victim has been ill for days. Researchers still don't understand how mannitol works in reversing the symptoms of ciguatera poisoning, though it is used in other patients as a diuretic and may flush out the toxin. For more information on mannitol, go to www.rehablink.com/ciguatera/treat.htm. Victims should also avoid eating fish, shellfish, any foods with nuts or nut oil, and drinking alcohol.

The simplest solution scientists can offer to those of us at the top of the food chain is to avoid eating larger individuals of suspect fish species. With the exception of testing fresh uncooked fish with a test kit called Cigua Check (www.ciguacheck.com), there is no way to determine if a fish carries the toxin. Predators heavier than four pounds are generally considered unsafe, since they've had time to acquire dangerous amounts of toxin. Avoiding the viscera and roe--usually the most tainted parts--of suspected fish is also a helpful way to avoid problems.