The illness itself is odd. It's not what you'd expect. You eat a fish, now hot feels cold, cold feels hot. Your mouth is tingling; your teeth hurt; you're itchy. You feel lousy.

It's all from a bit of fish you took while enjoying your vacation.

What is this? 

Certain types of fish have toxins that cause Ciguatera poisoning in people who eat them. These toxins come from a tiny organisms called dinoflagellates (algae) that cause the most common seafood toxin poisoning worldwide.

What are the Symptoms of Ciguatera Poisoning?

Ciguatera poisoning symptoms are varied and vague - some common, some odd and some just keep coming back. Some symptoms are fairly common from food poisoning - like the gastrointestinal symptoms: vomiting, diarrhea, and abdominal pain. Others are fairly odd - tingling around the mouth, painful tingling on arms and legs, itchiness, teeth pain, pain urinating, blurry vision, and even a reversal of hot and cold temperature sensation. Still other symptoms are quite serious, such as cardiovascular symptoms (slow or irregular heart rates). There may also be muscle aches, weakness, dizziness.

Fortunately, few die from this poisoning. Mortality is about 0.5%. This usually occurs from cardiovascular effects, low blood pressure, and pulmonary edema (or fluid in the lungs).

The disease is not usually spread from person to person, except, it appears, through sexual contact.

What Types of Fish Are Affected?

Only certain fish lead to Ciguatera poisoning. These are large, predatory reef fish, including barracuda, grouper, and red snapper, but also including amberjack, moray eel, amberjack, sea bass, sturgeon, parrot fish, and surgeonfish

These fish are found usually in tropical waters, such as in the Caribbean and Polynesia, as well as off the coast of West Africa and a recent sudden surge in coastal Southern China.

In the US, Ciguatoxin fish are found off the coasts of Florida and Hawaii, as well as Puerto Rico, Guam, the U.S. Virgin Islands, and American Samoa.

Fish are shipped around the world for consumption, so fish can also be consumed far from tropical areas leading to poisoning. Also, some such fish (barracuda and amberjack) migrate and can bring the toxin far from where it is usually found.

There are different toxins found in different locales. Polynesian cases tend to have more neurologic symptoms; Caribbean cases have more gastrointestinal and cardiovascular symptoms.

Symptoms can be worsened by other ingestions, such as alcohol which can increase the risk of bradycardia. These symptoms often can persist or recur recur, often brought on by alcohol, coffee, or nuts. This may last for weeks or months.

How to Avoid Ciguatera Poisoning?

Fish will not taste, smell, or appear different. It is only when people develop symptoms that the toxin is usually noticed.

1) Avoid eating large, predatory/carnivorous fish

2) Avoid eating large amounts of these fish, the head, roe, or viscera (organs in body cavity)

3) Avoid eating fish caught from areas known to have fish causing Ciguatera-poisoning

How Common Is this Poisoning?

There are likely more cases than reported. It is more common than realized. It is thought that over half a million in the Pacific Islands have had Ciguatera poisoning in their life. A survey over a year in 1984 in Puerto Rico showed that probably 7% of families had exposure to the poisoning. Those who did not eat fish often did so out of concern about the Ciguetera poisoning. A study a few decades old surmised that for every case reported in Miami that there are 10-100 not reported.

How Does the Algae Poison Seafood?

The toxin is produced by dinoflagellates, little one-celled organisms that make up algae found in coral reefs in tropical and subtropical waters. The dinoflagellates are picked up by herbivorous fish eating along the coral reefs. These fish are then eaten by predatory fish, which then accumulate higher and higher amounts the further they are up the food chain. The toxins are concentrated in these predatory fish and then eaten by humans. 

Dinoflagellates, Are These ever Seen?

Dinoflagellates are very small one-celled organisms. They are seen under microscopes. They however can be found in large numbers. When their numbers grow substantially, there can be millions of these organisms in 1 liter of sea water. Certain types of dinoflagellates (and there are many types) can discolor the water and can "bloom". This is which is called an algal bloom, and can lead to red tide or other discoloration of water.

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