What Is Ciguatera Poisoning, and How Can We Avoid It?

by Owen James Burke


A day’s catch from between Norman and Peter Islands in the Virgin Islands — a known hotspot for ciguatera

Ciguatera poisoning is a foodborne illness which comes from a toxin found in over 400 reef-dwelling species throughout the world’s tropical and subtropical waters. It’s viciously painful in some cases, and symptoms can be anything from slight malaise to aching joints, disorientation, diarrhea, and severe vomiting, which can last anywhere between weeks and years. Some historians believe that the ancient Polynesians developed such a problem with ciguatera, it may have been a major cause for their diaspora at the turn of the first millennium.

What Is Ciguatera and Where Is It?

Ciguatera is a toxin found in dinoflagellates (Gambierdiscus toxicus), marine plankton which attach to corals, algae and seaweed, and are consumed by reef-dwelling herbivorous fish. Certain reefs have very high concentrations of ciguatera, while others — anywhere south of Martinique, in the Caribbean, for example — have not even a trace, and as of yet, scientists are still unclear as to why this might be.

How is Ciguatera Contracted?

Ciguatera builds by slowly making its way up the food chain. Unfortunately, ciguatera is fat-soluble, so as it carries on up the food chain to larger fish like parrotfish, groupers, snappers, jacks, and barracudas, which oftentimes have the highest concentrations of the toxin (be careful where you order your ceviche). Furthermore, ciguatera is also heat-stable, so you can cook and char your catch all you’d like — whatever amount of ciguatoxins exist in that fish are staying with it.


Ciguatera (Gambierdiscus toxicus) (Photo: Maria Faust, Univ. of Texas)

What Are the Symptoms?

Detecting ciguatera poisoning can be tricky. Common symptoms include diarrhea, vomiting, tingling of the extremities (and not in a fun way), disorientation, and inability to sense differences between extreme heat and extreme cold, when turning on a faucet, for example.

Ciguatera stores up in one’s system over time, so, even if you’re regularly consuming small reef fish with small traces of the toxin, it’s quite possible you’ll hit your threshold at some point. Ciguatera symptoms can last anywhere from weeks to years, depending on the dose or concentration. A most important distinction to note about ciguatera is that it is impossible to develop an immunity against it.

Do I Have to Stop Eating Fish?

One approach, beyond certainty, will prevent ciguatera from ever entering your body. But all the same, it’s most certainly not an approach with which we are willing to live — that is, a diet free of ocean fish. There are plenty of reefs, fish and entire zones of the ocean completely unaffected by ciguatera, so switching to a land-based diet is entirely unnecessary (and, if you’re anything like me, nightmarish). Coincidentally, this is yet another case for eating smaller and more abundant ocean fish such as sardines, anchovies and sprats.

I love eating reef fish just as much as anyone, and certainly consumed my fair share while living in the Caribbean, but a diet built on prized reef fish is not only detrimental to the livelihood of the sea, it could likely bring about your own untimely demise as well.

Is There a Way to Test for Ciguatera?

Most scientists, researchers, doctors, and other professionals of the like will answer — rather bluntly — ‘No.’ However, my time spent in the islands with peoples whose sustenance depended largely on reef fish did teach me one trick: ants.

If you can find an anthill nearby while you’re cleaning or preparing to cook your catch (which should be no difficult feat on most Caribbean islands), take a piece of meat with a section of the spine or a small steak from the tail of a fish if you’re willing to afford it, and place the specimen beside the anthill. Ants, being the ever-laboring hungry-driven communists they are, will 9.9 times out of 10 come to investigate. This is when you’ll want to watch closely. If the ants begin to circle the fish, but do not eat it, it’s a good sign they’ve detected something suspicious about the fortuitous handout, and it’s likely that you shouldn’t eat that fish either.

Is this test entirely certain? I’m not a doctor, so no lawsuits, please. I have run this test a handful of times, and once did see a perfect ring of ants form around the tail meat of a black jack (Caranx lugubris).

How Do I Know If I’ve Been Poisoned, and How Can I Be Treated?

After ingestion of a particularly strong concentration, a patient will be well aware. There are no institutionally accepted methods of treatment for ciguatera poisoning other than bed rest. There is, however, one folk remedy that is quite popular in the Caribbean: an enema of soursop (a.k.a. guanabana, custard apple). Another remedy involves drinking tea from Mangrove buttons, which are high in tannins and the richly cleansing vitamin B.

The environment takes care of itself in strange ways, like plastic-dissolving bacteria which thrive in the great garbage patches of the oceans, for example. As reef fish population levels begin to take a slide, perhaps ciguatera is King Neptune’s way of telling us to give them a break. Okay, maybe that’s just a bunch of swill, but regardless, you don’t want ciguatera, and there are plenty of other fish in the sea, so chose your seafood wisely.

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