CIGUATERA - A Physician’s View

by Alayne Main, M.D.

Frequently asked questions and carefully composed answers from an emergency room doctor  and recent circumnavigator.

Disclaimer: 

Whilst every effort is made to provide current and accurate information and advice,  no liability is accepted by the Island Cruising Association for any incorrect statement or advice.

Is ciguatera fish poisoning common?

Ciguatera fish poisoning is the most common non-bacterial, seafood-related disease. It is possible wherever coral reef fishes are a food source, especially if there has been a reef disturbance ­either natural, as in hurricanes, heavy rains, and algal blooms; or man-made, as in dredging, bombing or wharf con­struction. It is endemic in places such as Southern Florida, Hawaii, Puerto Rico, the Marshall Islands, French Polynesia, American Samoa, Papua New Guinea, the Virgin Islands, the Bahamas and Australia - confined to areas between 35 degrees North and South of the Equator. However, distri­bution of poisoned fish is very spotty. Fish from one side of an island can be harmless while the same species of fish from the other side is poisonous.

How can I tell if a fish is poisoned? 

Ciguatera poisoning does not alter the fish in any way. There is no colour, odour or taste difference in affected fish. It should be assumed that any large (five-plus pounds) reef-feeding fish (i.e. parrot fish), or any large predator of reef fish (i.e. barracuda, eel, grou­per, snapper, jack) is poisoned unless you are told otherwise by a reliable source. The toxin is not affected by stomach acid, cooking, drying, freez­ing, salting or pickling. 

It sounds like we shouldn’t eat fish at all out there.

Pelagic fish caught offshore can be assumed safe to eat. Eat only small reef fish - a whole fish should fit on your din­ner plate. Always know what kind of fish you are eating. To eat a “mystery” fish from a coral reef is risky. Now you can purchase the Cigua­Check test kit to know for sure. The kit was de­veloped by Dr. Yoshitsugi Hokama of the University of Hawaii School of Medicine. There are apparently more than 10,000 tests in the field with a verified sensitivity for ciguatoxin of 92%.

How will I know if I have ciguatera fish poisoning?

The explosive onset of an acute ciguatera illness can be identified readily. It should be suspected in any­one who has nausea, vomiting and diarrhoea 10 minutes to 12 hours after fish ingestion, especially when neurological symptoms follow. Most reported cases experience vomiting and watery diarrhoea at the onset, commonly be­tween three and six hours after ingestion. The bizarre symptoms of temperature reversal sensation, perception of loose teeth, numbness and tingling of the extremities, tingling around the mouth, joint and muscle pain, and intense itching can appear up to three days later, often after the gastrointestinal symptoms subside. Cardiovascular symptoms are less common, but can be severe. They usually resolve within two to five days. Weakness and dizziness may result from low heart rate and low blood pressure.

The average duration of intense symptoms is 8.5 days and many people have symptoms for one to two months, but mild annoying, chronic symptoms can last up to ten years. There is cur­rently no blood test to diagnose the ill­ness in humans - it is a clinical diagnosis. Other cases of fish and shellfish poisoning, botulism and even decom­pression sickness in scuba divers can mimic the symptoms.

What can I do if I am poisoned?

There is no standard treatment for ciguatera poisoning, and there is no cure. All one can do is support the pa­tient with symptom relief, time being the biggest healer. Recently, there have been new treatments discovered for both acute and chronic ciguatera poisoning, however not all cases respond. Dr. Neal Palafox in the Marshall Islands pioneered the use of intravenous (IV) Man­nitol which has recently become a mainstay of treatment worldwide.

Mannitol is not a cure or an antidote for ciguatoxin, but is re­ported to relieve many of the severe symptoms. Mannitol is inexpensive and safe, and is available in most basic emergency rooms. Interestingly, Mannitol has been found to be helpful even six or more days after the initial poisoning, so if there is concern, moves should be made to get emergency medical attention, even if it is days away. Some ERs use ac­tivated charcoal in the first few hours to decrease the absorption of the toxin in the gut. Most doctors wouldn’t rec­ommend the use of emetics or purgatives because dehydration is a serious risk. However, in a remote setting, it may be all you can do to decrease the load of toxin.

Having said that, treat­ing the gastrointestinal symptoms is the first objective - stop the vomiting ­using the same protocol you would for any GI problem. Give the bowel sev­eral hours rest - no fluids at all, and then slowly, by spoonful, begin to take water or an electrolyte solution. Stick to clear fluids for at least 24 hours.

What drugs should I carry aboard for this type of emergency?

Because I feel that ciguatera poison­ing shouldn’t happen to you, I wouldn’t carry medicines specifically for this problem (for example, I wouldn’t stock IV Mannitol). However, we can all be caught out, and I would carry ample amounts of the medicines used for ciguatera symptoms, because these will be used for a variety of common medi­cal conditions you will encounter on a long-term cruise. 

These include:

Benadryl cream, Benadryl capsules and injectable Benadryl (diphenhy­dramine) - an antihistamine, used for allergic symptoms such as itch, swelling, redness - Dramamine tablets, Dramamine sup­positories and injectable Dramamine (dimenhydrinate) - an antinauseant, used for nausea and vomiting - Prednisone tablets - a steroid, used for severe inflammatory symptoms, whether allergic, toxic or sometimes even infectious (injectable cortisone for ciguatera is sometimes used, but oral steroids should suffice) - Atarax tablets (hydroxyzine) - a se­dating antihistamine, useful for itching that causes insomnia - Vitamin complexes, especially B complex and C - taken daily to supple­ment a limited cruising diet - Ipecac syrup - an emetic, used for poisoning, not an ideal choice for ciguatera poisoning - Imodium (loperamide) - an antidiar­rheal, used for serious or inconvenient diarrhoea, not a first-line treatment

What can I expect following ciguatera poisoning, after my symptoms have resolved?

The prognosis is generally excellent, however in some patients, long-term symptoms occur after eating fatty foods (oily food, peanut products, sesame oil), seafood products (fish, shellfish - even if cigua-free), and alcohol. Even though it is almost never fatal, ciguatera poisoning can result in long-term symp­toms of muscle aches, joint pains, and a weak, tired feeling - symptoms not easily treated. In chronic cases, there can be a misdiagnosis of chronic fatigue syndrome. Remember that subsequent poisonings are often more severe, and no one knows how long the toxin stays in the body. Prevention is your best ally.