Carmelo Gianino, who works on a tow boat at the Miami Beach Marina, follows an old rule of thumb in South Florida fishing — stay away from the big barracuda to avoid a nasty fish-borne illness called ciguatera.
He has seen a few people return to the dock, proudly displaying their toothy catches, and tried to pass on some local knowledge. “They show me a big barracuda and I say, ‘I don’t eat those,’ and they tell me, ‘You should, they’re good!’” Gianino said.
Clearly, not everyone takes the advice. A new study conducted by University of Florida and the Florida Department of Health found that ciguatera strikes nearly 30 times more people than previously believed — with Hispanics among the most common victims to a toxin that can cause vomiting, nausea and, in the worst cases, paralysis.
The Florida Keys, where seafood is a daily staple, tops the list for a sickness often called fish poisoning, followed by Miami-Dade County. But the previous official rates, researchers say, dramatically underestimated the impacts.
Official state health records show ciguatera affects about one out of every 100,000 people in Miami-Dade and three out of every 100,000 in Monroe County each year. But based on more than 5,000 surveys of anglers, the Health Department and UF’s Emerging Pathogens Institute found that —while still rare compared to many other food-born illnesses such as salmonella, E.coli and norovirus — actual ciguatera cases are likely closer to 28 per 100,000 in Miami-Dade and 84 per 100,000 in Monroe.
Ciguatera is caused by a toxin in algae that grow on reefs in tropical and sub tropical waters. It moves up the food chain as fish feed on the algae and become prey for larger ones. The toxin is ingested into the flesh of the fish, and causes unpleasant symptoms when eaten by humans. While barracuda — which many South Florida anglers have been schooled to throw back — is known to be the most common carrier, researchers report that mahi mahi, hogfish, amberjack and grouper could carry the toxin as well.
“Any carnivorous fish that eats fish off the reef could potentially be toxic,” said Elizabeth Radke, the lead author of the study published in the American Journal of Tropical Medicine and Hygiene. Radke doesn’t think people should avoid eating them altogether, but just be aware of the risk. “People who eat fish from these areas should know it’s possible to get sick.”
Ciguatera is colorless and odorless and can’t be eliminated by cooking or freezing. There’s no cure for the illness, though a drug called mannitrol has been shown to reduce symptoms if taken early. Radke recommends those who feel sick one to three hours after eating fish seek medical attention and save a piece in the freezer that can be tested for toxins later.
South Florida is the most common place for ciguatera in the state, where seawater temperatures are higher and reef algae is prevalent. The ideal temperature for the algae to grow is in warm water, 84 degrees or more, and Radke worries that as temperatures rise, new areas may be at risk.
“For ciguatera, the hypothesis is that it will move further north as sea temperatures change with climate change,” she said. Odds are fishermen up north aren’t aware of ciguatera, which could cause public health risk in the future.
Although researchers found cases of ciguatera to be more common than previously thought, actual infections are not on the rise. The Florida Department of Health plans to continue educating communities via their website and outreach.
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