Heading South for the Holidays? Why You Should Be Careful About Eating Local Fish

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Few meals rise to the level of a life-changing event. For Andrew Kirsop, however, a fresh seafood dinner in the Cook Islands was just that. Devastatingly so.

In January of 2007, Kirsop, then 25, was vacationing with his family in Rarotonga, not far from Fiji, when he ate fish that was contaminated with ciguatoxin. Believed to be one of the most potent natural substances known, ciguatoxin, even the smallest amounts, can lead to ciguatera fish poisoning (CFP) — perhaps the most commonly reported seafood-toxin illness that few people have ever heard of.

After eating the contaminated fish (Kirsop says he ate such a wide variety of seafood that he can’t be certain which fish held the toxin), he says he had “difficulty focusing and was nauseous — just feeling off. My stomach was upset and I had this overwhelming urge to fall asleep.” (More on Time.com: Study: Could Cell-Phone Use in Pregnancy Affect Kids’ Behavior?)

Worldwide some 500,000 people are estimated to be affected by ciguatera each year, a figure that researchers from the Ciguatera Fish Poisoning Monitoring project suggest may be increasing because of climate change — as surface water temperatures rise, so do the algae that harbor the toxin. But despite being so widespread, CFP can be tricky to pinpoint, especially outside of endemic areas. For one thing, the symptoms vary widely — from mild food poisoning to more serious neurological problems — and for patients like Kirsop, they can change over time.

Kirsop did not seek treatment until he returned to the U.S., and by that time his condition had deteriorated dramatically. A month after returning home, Kirsop’s symptoms had become so severe that he struggled to speak. “What would happen was, I would think about what I was trying to say and by the time I could say what I wanted, I’d forgotten what I was saying,” he said. (More on Time.com: How Not to Get Sick)

He was forced to quit school a few months shy of graduating from Evergreen State College, where he had been studying business and economics. “Not being able to speak really put a damper on my classes,” he says.

Kirsop’s experience with CFP is extreme. In such rare cases, people can suffer neurological or neuropsychiatric symptoms, including anxiety, depression and even memory loss, which may plague them for years, and if left untreated, potentially result in coma. One distressing characteristic symptom of CFP is temperature-related dysesthesia, in which a person touches an object that is hot and the brain registers it as being cold, and vice versa. But the majority of people who develop CFP experience only mild food poisoning, which includes nausea, vomiting, diarrhea and stomach pain — not exactly a day at the beach.

Dr. Glenn Morris, a physician working with the multicenter, interdisciplinary Ciguatera Fish Poisoning Monitoring project, acknowledges that scientists still do not fully understand CFP. What doctors do know is that the toxin attacks the nervous system, and that it is common and potent. “There is very high attack rate, it takes a very small amount of toxin to get sick,” says Dr. Melissa Friedman, a neuropsychiatrist in Florida. Doctors think the more contaminated fish you eat, the worse the symptoms. (More on Time.com: Top 10 Most Dangerous Foods)

To reduce their risk of illness, tourists heading to the islands this winter should educate themselves about the risks of eating local fish. CFP happens frequently in tropical regions, mostly in the Caribbean, Hawaii, Florida, Australia and the Pacific Islands. The toxin itself forms in dinoflagellates, a type of algae found on coral reef. Small fish eat the algae, then pass the toxin up the food chain. The contaminated fish that lands on your dinner plate, however, looks and tastes the same as uncontaminated fish, so it’s hard to avoid.

The Florida Department of Health recommends sidestepping local fish that are most commonly associated with ciguatera — such as barracuda, hogfish, red snapper and grouper — when visiting endemic regions. Travelers should also ask local fishermen about which types of fish to avoid, since they are likely to be familiar with the illness.

Physicians in these areas are also likely to recognize the early signs of CFP and know to ask patients if they have recently eaten fish. But apart from that key question, doctors’ only way to diagnose CFP is to rule out other possibilities. “Ciguatera is a diagnosis of exclusion,” Dr. Friedman says. (More on Time.com: 6 Common Sources of Radiation In Your Life)

Researchers are now working on other ways to diagnose the illness. Dr. Morris says he is currently studying the biomarker molecules created by the toxin, which could lead to a fast and accurate diagnostic test, say by analyzing a patient’s blood or saliva. Currently, there is no surefire antidote for CFP; mannitol therapy is typically used to treat the symptoms, with varying levels of success.

Andrew Kirsop hopes to help change that. Despite continuing symptoms, he eventually returned to school and completed his undergraduate degree in 2008. Now he plans to pursue a graduate degree in environmental studies, with a focus on the effects of ciguatera fish poisoning — a subject he, unfortunately, knows first-hand.

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