Something Fishy - Ciguatera
Fresh fish it's delicious, and one of the healthiest foods you can enjoy, right? Well, usually. But in some parts of the world, including a few particular areas of the Caribbean, a certain toxic organism travels up the food chain through reef fish, then predatory fish and eventually to man, causing the bizarre and uncomfortable set of symptoms known as ciguatera. In extreme cases, death can occur.
In the Caribbean, ciguatera is most commonly reported in the area from the Virgin Islands to Montserrat, but odd cases have cropped up in other locations.
Anyone who has experienced ciguatera's symptoms knows that they are to be taken seriously, as John Smith can attest. "I have personally been poisoned twice in the Caribbean," he reports. "Once, while crewing aboard the ketch Meroe of Kent, seven of us were poisoned after sharing a Spanish mackerel caught between Barbuda and St. Barth's. We were enroute to Sint Maarten for one of the Heineken Regattas there, and to this day I blame our poor showing in the races on the effects of the poisoning. All of us were alternately enroute to the head or so sore in our arms and legs as to be unable to make efficient sail changes.
"In 1974," he continues, "I sat at a barbecue in the `ghetto' of old St. Barth's adjacent to the Yacht Club, enjoying the rum, impromptu music and chatting with new friends. The cruiser on my right took a piece of fish from the grill and I took the piece next to it. By morning he was dead and I was one sick puppy! For two months I was unable to hold as much as a cup of tea without spilling it."
John adds, "Just recently my friend Ed Teja wrote to me about an incident which occurred in Cumaná, Venezuela, and because of it requested that I write to Compass about ciguatera. It seems that the woman from whom he regularly bought fish took a barracuda home to feed her own family and she and three of her children died."
Ciguatera is nothing new. It was described as early as 600 BC by the Chinese, and Captain James Cook's log details effects felt by his crew on a voyage to Tahiti in 1774. The first clinical description of the syndrome was written by Portuguese biologist Don Antonio Parra whose observations were published in Havana in 1787. In his account Parra says, "some [fishes] cannot be eaten because they are `ciguatos' and some others are suspicioned because they carry with them the poison.. I can speak from personal experience, because on 15 March 1786, twenty-two of us ate a Cubera, and we all developed those symptoms to a greater or lesser extent. All were prostrated, but each one was suffering various types of discomfort, although the most common type of difficulty was the extreme exhaustion accompanied by more or less pain. I observed that I had extreme difficulty in breathing, which caused great pain and a feeling of suffocation. My tongue became rough and I developed a sour taste in my mouth."
Over 150 different symptoms have been reported, ranging from the gastrointestinal to the cardiovascular. One of the strangest is the neurological disorder that causes sufferers to feel a reversal of the sensations of hot and cold. One victim in the Virgin Islands said, "It was crazy; I'd sit in the noonday sun and be freezing cold, or drink a beer and it would taste really hot." Tingling around the mouth, hands and feet is also commonly reported, as are nausea, diarrhea and headache. The onset of symptoms usually occurs within 3 to 5 hours of eating a ciguateric fish, and can last months in severe cases. Symptoms are sometimes mistaken for salmonella or other bacterial contamination, but ciguatera is completely unrelated to spoilage.
Susceptibility and severity of symptoms varies greatly among individuals. Ciguatoxins are accumulative, and evidence suggests that individuals who have been previously exposed react at lower levels and experience more severe symptoms. Those who have been infected are advised to avoid consuming fish, shellfish, alcoholic beverages and oily foods including nut and seed products, as consumption of these may cause symptoms to re-occur.
The ciguatera threat begins when reef fish ingest the toxin-bearing dinoflagellates called Gambierdiscus toxicus microscopic, single-celled, free-swimming marine organisms which have attached themselves to the coral-dwelling marine algae which is the fishes' food. Larger, carnivorous fish eat the reef fish, and are in turn eaten by even larger predatory fish, which may in turn be eaten by man. Although hosts to the toxins, the fish themselves are not ill.
Ecological conditions in some localities support a continuous population of dinoflagellates, which then produce more ciguatoxin-bearing fish than other areas. Ecological disturbances to a reef, such as storm surges or careless development, can also cause the toxic organisms to spread rapidly.
In the Caribbean, ciguatera is most prevalent in the islands north of Martinique. A paper by David Olsen, David Nellis and Richard Wood published in the Marine Fisheries Review (Vol. 46, No. 1) pinpointed three primary centers of the toxin: one near Redonda between Antigua and Montserrat, one between the Saba Bank and the Anguilla Bank, and a third along the narrow shelf south of Norman and Peter Islands. Several St. Thomas, USVI markets no longer sell local fish and import all fish products sold, except for a very narrow range of species caught in specific "safe" locales. (John Smith says, "Anyone who has spent any time in the Virgin Islands is well aware that giving someone a kingfish caught on the south shore is not considered an act of kindness.")
Big Bad Fish
Because the toxin accumulates in the body of the fish, you should avoid eating large specimens of potentially ciguatoxic fish such as barracuda and kingfish that may carry high concentrations, even in areas where ciguatera is rare. St. Vincent & the Grenadines, for example, has had only one confirmed incidence of ciguatera poisoning, but it was devastating. A report by Chief Fisheries Officer Kerwin Morris relates that on the late afternoon of November 23, 1985, in the village of Owia, people "started pouring into the clinic in search of relief from vomiting, diarrhea and abdominal pains." By the next morning, over a hundred villagers were hospitalized in nearby Georgetown.
It was discovered that some 120 people had eaten a noonday meal that included meat from the same 30-pound barracuda. Some affected individuals had merely drunk the broth in which a piece of fish had been boiled. An undetermined number of small animals including cats, dogs and chickens died after eating parts of the fish which had been thrown away.
According to the Caribbean Fisheries Research and Management Project (CFRAMP), affected fish looks, smells and tastes normal. Freezing, drying, marinating, salting or cooking the fish does not destroy the poison. The freshness of the fish has no bearing on its toxicity.
So what to do, especially when you enjoy eating fish?
Exercise extreme caution when eating fish in high-risk areas (i.e. north of Martinique).
Avoid those fishes that are most often toxic. Potentially ciguatoxic fish include (but are not limited to) barracuda, greater amberjack, kingfish, cavalli, mutton and dog snapper, sharks, large grouper, hogfish and moray eel. Plant-, plankton- and coral-eating fish tend not to be toxic, and pelagic species such as dolphin (dorado) and tuna are rarely implicated.
Always ask the locals what they eat and don't eat. (Remember that common names often differ from one location to another.)
Choose small specimens of a species, as they are usually less likely to be toxic than large ones.
Test the fish you catch with a test kit
Always clean a fish thoroughly before cooking it. The poison is usually concentrated in the head, organs and roe.
If you experience any symptoms of ciguatera, seek medical attention immediately. There is no antidote, but symptoms can be alleviated.
Information from Compass correspondents Clifford Lee-Juillerat and John Smith, and from the Caribbean Fisheries Research and Management Project, Ciguatera by Dr. Yoshitsugi Hokama, and the Marine Fisheries Review was used in preparing this report.
Ciguatera Test Kit
Folklore says you can test a piece of fish for ciguatera by seeing if a silver coin placed on it turns black, or if a sweet potato boiled with it changes color. These tests have proven to be unreliable.
A faculty member at the University of Hawaii, Dr. Yoshitsugi Hokama, has developed a scientific test kit to determine whether or not that fish you just caught is really safe to eat.
The kit, which California sailing magazine Latitude 38 says "works like one of those pregnancy kits you buy in the drug store", has only one drawback the test takes an hour. Can you wait that long before you toss those succulent kingfish steaks onto the barbecue grill?
For information on ordering kits, contact Oceanit Test Systems. 1100 Alakea Street, Honolulu, Hawaii 96813, USA. Tel (808) 531-3017,
fax (808) 531-3177, E-mail firstname.lastname@example.org
Copyright© 1998 Compass Publishing