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Voyagers deal with the risks of ciguatera

Jan 1, 2003
From Ocean Navigator #119 January/February 2002

From Ocean Navigator #119 January/February 2002

Voyagers deal with the risks of ciguatera

As thrilling as it is to land enormous barracuda, only small ones should be eaten to avoid risk of ciguatera poisoning. Knowing fish species and habits is key to safety.
   Image Credit: Masa Ushioda/Innerspace Visions

To the editor: Like most people who cruise the Caribbean and Bahamas, we frequently ask ourselves if the fish we catch are safe to eat. Some warm-water fish can contain toxins that are harmful to people. The most talked about marine toxin is ciguatera. Other marine toxins, such as fugu (Tetrodon/puffer fish) and various shellfish-borne marine toxins are apparently rare. Ciguatera is generally suspected of reef fish such as barracuda, grouper, snapper and kingfish. Like most cruisers, we are not physicians or experts in marine toxins, but since we frequently catch suspected fish in southern waters we need to know what we can eat and what we should throw back. The yachting medical guides we have onboard say little or nothing about marine toxins, particularly ciguatera.

Ciguatera research, including reference to a medical dictionary, must be done ahead of time and included as an addendum to medical texts onboard. Once underway, we have learned that we are much too busy landing big fish and sailing the boat at the same time to stop and look at the books for particulars on marine toxins. We also want to know what fish to keep when diving on a reef or fishing from the dinghy. We know that we have thrown back edible fish in the past. A little homework on toxins can mean more meals of fresh fish without worrying about possible after effects.

We need ciguatera information most when we are fishing in remote areas in foreign countries. Other than radio email we, like many voyagers, don't have Internet access on the boat, nor are we able to call the Florida Poison Information Center/Miami Marine Toxin Hotline at 888-232-8635 or visit their Marine Toxins website at www.niehs.nih.gov/centers/center/mis-ctr.htm. After talking with the experts in Miami, I learned that cases of ciguatera reported to the center are rare; one case was reported in the past six months, for example. This does not mean there are no cases in the Bahamas or the Caribbean, but evidently few are reported to the center. A ciguatera test kit is available from a company based in Hawaii. Apparently the ciguatera toxin is more common in the Pacific than the Atlantic. Although the crew of an inter-island freighter was infected with ciguatera in March 1999. The seriously ill crew was taken to the hospital in St. Thomas. The incident was well-reported in the press, but the reports neglected to name and describe the infected fish or exactly where the fish was caught! The Cigua-Check website (www.cigua.com) offers a fish poison test kit. The test kit has a shelf life of six months and costs $28.99 for five tests. Whether or not it is practical to stop fishing and perform a laboratory test on the flesh of suspected fish when bouncing around in a dinghy or trolling from the boat is a matter of personal choice.

Tests of suspected fish could, of course, be performed back at the boat before eating the fish. We don't know any voyager who has performed ciguatera tests. Local health care providers generally know very little about the subject, and none we know has test kits on hand. I frequently ask local fishermen which fish carry the ciguatera toxin, but their answers are usually vague. Locals don't seem to pay much attention to the subject. Or maybe they diagnose ciguatera as something else.

We have since learned that local restaurants frequently serve fish we have thrown back in the past. I would welcome guidelines on fish toxins from others much more expert than I. Ciguatera should be taken seriously, yet very little has been published that can be used as a practical guide for cruisers. There is a book available at www.cigua.com/cigua_book.htm for $15.00. The following was received from the Miami center and from Oceanit (www.oceanit.com), the firm offering the fish poison test kits. Our own experiences are added.

Symptoms

Symptoms generally appear within 24 hours. Nausea, vomiting, diarrhea, paresthesia (numbness, tingling, prickling or any abnormality of sensation), muscle weakness, hot-cold reversal, headache, myalgia (muscle pain), dysuria (difficult urination), hypotension, coma.

Ciguatera, like some other toxins, can accumulate in the body. During our travels, we have only observed a couple of mild cases where paresthesia was the chief symptom. The individuals returned to normal within a day or two with no apparent long-term effects.

Suspects

Barracuda, grouper, snapper, kingfish especially fish from reef areas in warm waters.

Ciguatera reports seldom name the species of fish or where they were caught. Based on hearsay about carriers of the ciguatera toxin, we have thrown back a number barracuda of various sizes. Barracuda are suspect because they prey on herbivorous (algae-eating) fish. We have since come to believe that young barracuda, less than 3 feet long, are edible, provided only filets are taken without cutting the spinal cord. We regularly eat grouper, snapper and kingfish without concern.

Geographic distribution

Sub-tropical to tropical, worldwide.

In the Virgin Islands, we observed mild symptoms of paresthesia with a cruising couple that lived off of reef fish. Several patrons were infected with ciguatera in a Bahamian restaurant serving tainted snapper. Unfortunately, the source of the fish was not available.

Major toxin

Ciguatoxin, scaritoxin, maitotoxin.

Incubation

Hours

The Miami center and Oceanit told us that symptoms generally appear within 24 hours.

Duration

Years

We have observed no one with long-term effects.

Therapy

Mannitol, Supportive, TCA (chronic paresthesia).

The best treatment for ciguatera poisoning during the early phase (one to three days after eating toxic fish) has been mannitol infusion carried out in a physician's office or emergency unit of a hospital. Mannitol is not a cure or antidote for ciguatoxin, but it relieves many of the severe symptoms, except for diarrhea, in some patients. The Miami center reported that Mannitol is available in most hospitals. We have no information about mannitol in the out islands.

In some patients, long-term symptoms occur or reoccur after generally eating fatty foods (oily food, peanut products, sesame oil), seafood products (fish, shellfish, etc.) and alcohol (wine, beer, hard liquor). The long-term, chronic symptoms, such as muscle ache (myalgia), joint pains (arthralgia) and a weak, tired feeling (asthenia), have been successfully treated with tocainide and amitriptyline (anti-depressant) in some patients.

Earlier symptomatic treatment for ciguatera, and still used by some physicians, includes the following drugs: 1) calcium gluconate, 2) atropine and lidocaine for cardiac problems, 3) corticosteroids and antihistamines for potential hypersensitivity, and 4) other drugs, dexamethasone, cobalamine, vitamins (B complex and C), phenobarbital, plasma-infusing imodium, verapamil and dopamine.

Diagnosis

Immunoassay, clinical, mouse bioassay.

Tests must be performed on the flesh of suspected fish to determine the level of ciguatoxin. Test kits are the logical answer. The source listed for the Cigua-Check test kits in the Caribbean, is at the Blade and Key Center, 6292 Estate Nazareth No. 100, St. Thomas, VI. Telephone: 00802-1104 304-775-3254. Florida has one source listed: Capt. Harry's Fishing Supply, 100 NE 11th St., Miami, FL 33132-1726, Telephone: 305-374-4661, 800-327-4088.

Each cruiser must make his or her own decision about what fish to eat or not eat. We eat nearly all the fish we catch except for barracuda over 3 feet in length. We welcome comments from others on the subject.

Dick de Grasse is a frequent contributor to Ocean Navigator. He and his wife Kathy winter in the Caribbean on their sloop Endeavour and spend summers at their home on Islesboro, Maine.

Scott and Wendy Bannerot respond:

Hats off to Dick de Grasse for his thorough, up-to-date discussion of ciguatera. There are other potential hazards of consuming fish and shellfish, including hallucinogenic, tetrodotoxic, and ichthyotoxic fish poisoning, shark poisoning, clupeotoxism, scombrotoxism, and paralytic, amnesic, neurotoxic, diarrhetic, venerupin, neosurgatoxic, and prosurgatoxic poisoning. Regarding ciguatera, we feel that voyagers can virtually eliminate the chance of contracting it through a combination of the following measures: 1) sharpen your fish identification skills so that you are able to identify your catch to species level; 2) learn species, sizes and depth ranges considered dangerous for your area the best source of information is local fishermen (not necessarily the general public); 3) purchase and keep onboard a Cigua-Check kit we've found the test simple and easy to use, and if it allows you to eat just one nice fish every six months in circumstances where you have some doubt and local, expert advice is not available, it pays for itself (regardless of your location, you can order the kit from Capt. Harry's Fishing Supply as De Grasse mentioned); 4) as De Grasse said, you can't necessarily trust fish served in restaurants or sold at local markets. We're familiar with numerous poisoning cases under these circumstances in both the tropical Atlantic/Caribbean and Indo-Pacific, as economic motives induce people to push safety margins.

Lastly, we agree with De Grasse about the reasonable safety of eating small barracuda, but not "regularly eating grouper, snapper and kingfish without concern." Kingfish (or king mackerel, Scomberomorus cavalla) are occasionally ciguatoxic, particularlyy´in the northeastern Caribbean, and may also develop scombrotoxism unless they are absolutely fresh. Whether or not a particular grouper or snapper is safe to consume depends strongly on species, size of the fish, and location and depth of capture many are completely safe to eat, some can be strongly ciguatoxic. Arm yourself with knowledge and you'll have no problems.

We answer several of the questions he raises in our section on ciguatera in Chapter 10, "Medical Considerations for the Cruising Fisher," of our book The Cruiser's Handbook of Fishing (International Marine, 2000). We list numerous medical references and give specific guidelines for avoiding all of these afflictions.

Marine biologists Scott and Wendy Bannerot and two-year-old son Ryan live aboard their 41-foot aluminum sloop Elan, based in the South Pacific.