Science Scope

Fish in the Caribbean could poison you. Is climate change to blame?

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Researchers at the University of Florida uncover the possible link between climate change and the toxins in fish that poison the people who eat the fish.

If you eat toxic fish, you'll get the normal bouts of diarrhea and vomiting within six to eight hours of eating your dinner. The emergency doctors at a hospital in St. Thomas know that when a patient comes in at two in the morning with classic symptoms of ciguatera fish poisoning, the patient likely ate poisonous fish for dinner.

But the discomfort doesn't end there. The patient feels numbness and tingling in the arm.

Ice cream tastes hot. Coffee tastes cold.

There's numbness in the teeth.

The symptoms can last for weeks. Not only can it be debilitating, it can kill the person. Fortunately, the cases in the Caribbean are milder than the cases seen in other tropical hot spots.

Ciguatera is caused when toxins are produced by algae found in coral reefs. Bigger fish like barracuda are a problem because the toxins accumulate. Humans too can become sick. The disease is common in tropical regions of the world like the Pacific Ocean. But the tales in the Caribbean have been pretty anecdotal to date.

Researchers involved in The CaribCATCH project are looking more closely at what's going on in St. Thomas, U.S. Virgin Islands, to find out how the locals are dealing with ciguatera fish poisoning.

Emerging Pathogens Institute director Glenn Morris at the University of Florida is working with the University of Maryland, the Woods Hole Oceanographic Institute, the U.S. Food and Drug Administration, the University of the Virgin Islands and Florida State University.

"If you go to a tourist hotel restaurant, you won't eat the local fish. The fish you'd eat is imported from the mainland," Morris said. "The hotels were sued to many times because the local fish sickened too many people."

The local people are at risk. There are 7.3 cases for every 1000 people in the population. That might not seem like that much, but if you multiply that by your life span, there's a good chance you'll get the fish poisoning at some point.

And worse, it's not like if you get it once, you are immune to it. There's an opposite effect: you actually get more sensitive to the poison. Tiny levels of the toxin can trigger symptoms again.

Morris remembers passing a stall that said, "We serve barracuda, eat at your own risk." Seventy percent of barracuda are toxic.

"We don't know that much about the toxin," Morris said. "We want to understand the change of climate, the warming water temperatures in the Caribbean, a disease that's related to water temperature and how that translates to the number and severity of illnesses as seen in St. Thomas."

The locals know the disease well. It's been documented for hundreds of years; the Spanish first reported it.

The researchers are doing phone calls with the locals to find out more of their stories and get a sense of incidence data.

The scientists are also out there collecting samples from the coral reef, so they can carefully monitor the temperature of the reef. "We are looking for bleaching events, where the reef dies and the toxins move in," explained Morris.

In the lab, when the researchers raise the temperature, the algae grows better.

"We are getting increasing water temperatures. The Atlantic warm pool forms each summer in the Caribbean," Morris said. "There's an increased toxicity in fish and increased cases in humans. Does it translate?"

"The problem with ciguatera might be getting worse. From the lab data, the algae that produces the toxin is sensitive to water temperature. The Atlantic warm pool is expanding. Can we link the changing water temperatures with the algae that produces the toxins?"

Doctors in the Caribbean might know this disease well. But doctors in less tropical places might not be aware of this illness. Tourists can return home and get the seemingly "mysterious" illness.

"The disease can really result in people being debilitated," Morris said. "We are concerned with the rising temperatures."

Once a fish has ciguatera, it looks and tastes normal. It's unaffected by cooking. Sometimes, people say it was the tastiest fish they ever had.

Boonsri Dickinson

Contributing Editor

Contributing Editor Boonsri Dickinson is a freelance journalist based in San Francisco. She has written for Discover, The Huffington Post, Forbes, Nature Biotech, Technewsdaily.com, Techstartups.com and AOL. She's currently a reporter for Business Insider. She holds degrees from the University of Florida and the University of Colorado at Boulder. Follow her on Twitter. Disclosure