Warning for seafood lovers: Beware of toxic fish

Posted at 10:00 PM, Feb 08, 2017
and last updated 2017-02-09 06:41:18-05

ESTERO, FL - When you think of what can hurt you in the ocean, chances are sharks come to mind.  But a more likely threat to your health is something that you can't see: tiny toxins found on algae called ciguatoxins.

Researchers are Florida Gulf Coast University in Estero have been taking a close look at ciguatoxins, which can make you sick, and in rare cases be deadly.

FGCU Marine Science professor Dr. Michael Parsons tells 4 In Your Corner he's done a theoretical calculation to give an idea of just how toxic we're talking.  "If you had purified ciguatoxin, you would need, say, just 150 pounds of it to kill everybody on the planet," says Parsons.

But that's purely theoretical, so don't worry about ciguatoxins becoming the world's next biological weapon anytime soon.

The toxins occur in nature in microscopic amounts. Even so, they can pack a punch - especially as they accumulate in fish.

The algae that contain the toxins are eaten by small reef fish, which are then eaten by larger fish, that are eventually eaten by humans.  The larger and older the fish is, the more ciguatoxins it's likely to contain.  And if you eat an infected fish, you could get ciguatera.

"Ciguatera is a form of seafood poisoning that's caused by toxins that accumulate in fish," says Dr. Parsons.

The Florida Department of Health's website has this to say about ciguatera: "Over 400 known fish species have been classified as potential ciguatoxin carriers. Examples of species associated with Florida cases include barracuda, grouper, amberjack, snapper, tuna, kingfish, eel, trevally (jack), seabass, mackerel, hogfish, and mahi-mahi. Cooking fish does not kill the heat-stable toxin. Ciguatoxic fish do not carry a foul odor or taste."

"There's no way we know of yet to remove the toxin from fish tissue," says Dr. Parsons.

For many people who get the sickness, the initial - and sometimes the only - symptom is gastrointestinal distress similar to food poisoning.  But it can get much worse from there.  "It's a neurotoxin, so it'll affect neurons in your brain," says FGCU marine science researcher Adam Catasus.

That effect on your brain could take many forms: shooting pain, confusion, hallucinations, numbness, uncontrollable itching, painful ejaculation and a strange sensation in your mouth.  "Your teeth may feel loose and kind of jiggling," says Dr. Parsons.

Another bizarre symptom is known as "temperature reversal", where your brain and body mistake hot for cold and vice versa.  "Whenever you drink cold water or soda, you might feel like your esophagus is burning," says Catasus.

"If you touch something hot, it might feel freezing cold," he adds.

Dr. Parsons says he gets emails and calls from people who've been struggling with the symptoms long after they ate infected fish.  "There are cases of symptoms lasting years." says Dr. Parsons who explains some patients notice the symptoms disappear and then reappear when triggered by something as simple as a glass of wine.  "But there is no cure," he says.

The Centers for Disease Control's website gives the following information on how many people get sick with ciguatera each year and where the cases are reported:  "More than 50,000 cases of ciguatera poisoning occur globally every year. The incidence in travelers to highly endemic areas has been estimated as high as 3 per 100. Ciguatera is widespread in tropical and subtropical waters, usually between the latitudes of 35°N and 35°S; it is particularly common in the Pacific and Indian Oceans and the Caribbean Sea. The incidence and geographic distribution of ciguatera poisoning are increasing. Newly recognized areas of risk include the Canary Islands, the eastern Mediterranean, and the western Gulf of Mexico."

Fish that are most likely to cause ciguatera poisoning are carnivorous reef fish, including barracuda, grouper, moray eel, amberjack, sea bass, or sturgeon. Omnivorous and herbivorous fish such as parrot fish, surgeonfish, and red snapper can also be a risk."

The most severe symptoms from ciguatera can occur right after you've eaten contaminated fish.  The symptoms are rare but serious: a dangerous drop in blood pressure and slowing of the heartbeat.

"Ciguatoxin can be fatal if it's a high enough dose," says Dr. Parsons.

Last year, a British woman's case of ciguatera made national headlines after she died just ten minutes after being taken to the hospital.  She had eaten cooked grouper on her honeymoon in Mexico.

Dr. Parsons told Fox 4 about one of the few surveys done in Florida.  "Based on the survey results, they determined about a 1000 people a year in Florida get sick with Ciguatera," says Dr. Parsons.

But he also tells Fox 4 it's difficult to tell which of those cases came from Florida fish.  "A fish that (can be) caught in Fiji and be served in a restaurant here in Fort Myers or Naples," says Dr. Parsons.  

"There is no way to test if the fish has toxin.  Over 80% of our seafood is imported and who knows?" says Parsons.

Another unknown that's got the researchers' attention is whether we'll see more ciguatera because of two key factors affecting our coastal waters: "Sea level rise and sea temperatures changing, it might (make it) become more prevalent in Florida," says Catasus.

Fox 4 asked Dr. Parsons if it's possible to catch fish with ciguatoxins off the coast of Southwest Florida.  "To be determined," he answered.

For now the researchers' best advice is to be cautious and know that size matters.  "If the fish is bigger and older, it's been in the food web longer, and it's been able to accumulate more toxin," says Catasus whose friend made a video of some their spearfishing adventures in which they catch fish and cut open their bellies to check for the presence of the algae (known as Gambierdiscus) that may contain the toxins.

Dr. Parsons says there's one fish that often poses risk and has been linked to numerous cases of sickness and even death.  "The best way to avoid ciguatera fish poisoning is not eat large barracuda," he says while offering a general guideline on how to judge a "big" barracuda: "Bigger than your forearm," he says.

"Those will be more likely," to have ciguatoxins he says.  "You're probably talking 20% up to 50% chance," more likely he adds.

And though the chances of poisoning are lower in other common species, there's quite a list of those known to cause problems.  "Other fish that have gotten people sick are amberjack, hogfish and grouper," says Catasus.

Dr. Parsons says many of the reported Florida cases of ciguatera were linked to grouper -- not because it's more toxic, but rather because it's so widely eaten.

The team definitely advises against eating fish organs which tend to have concentrated toxins.  "In the Indian Ocean people have died from eating shark brains, or shark livers," says Dr. Parsons.

But the researchers are say they don't want to be "the boy scientists who cried wolf," as Dr. Parsons put it, and were careful to let local fish eaters they shouldn't panic.  "I would say they do not need to give up seafood," says Dr. Parsons.

"The fish in Florida are generally safe," he says.

And they're taking their own advice.  "Hogfish is my favorite, and I'll still eat it," says Dr. Parsons, who notes hogfish is on the list of fish that 's been linked ciguatera cases.

"I still eat fish," says Catasus.  "I love seafood," he adds with a smile.

Both Catasus and Dr. Parsons recommend keeping an eye out for any FDA advisories that report ciguatera cases.  For example, advisories were issued for fish from Florida Garden Banks National Marine Sanctuary in the Gulf after cases were reported in the past.

A quick search of the internet will show you cases have been reported in Florida over the years too.

And the researchers at FGCU are hoping their work will help us all learn more about this toxin before it can hurt anyone else.  "The main goal to keep an eye out," says Catasus.  "And just try to help people not get sick."

Links on Ciguatera:

FGCU Study of Ciguatera
Ciguatera Warning from Florida Department of Health
Ciguatera & Climate Change Report -  National Institutes of Health
Centers for Disease Control Information on Ciguatera