Ciguatera

What is ciguatera?

Ciguatera is food poisoning you get from eating fish contaminated with ciguatoxin. Ciguatoxin is a neurotoxin, a substance that changes how your nervous system works. Ocean algae called dinoflagellates (Gambierdiscus toxicus) grow in and around coral reefs and make ciguatoxin. Tiny fish eat dinoflagellates. Then, bigger fish that people eat, like grouper or snapper, eat the little fish, ingesting the ciguatoxin, too.

Ciguatoxin isn’t harmful to the fish but is poisonous to humans. If you eat contaminated fish, you’ll experience symptoms that can affect your digestive system, nervous system and (in severe cases) cardiovascular system (heart).

Although ciguatera isn’t typically fatal, it’s essential to go to the emergency room (ER) immediately to stabilize your condition and prevent serious complications.

Where is ciguatera fish poisoning found?

Anyone around the world can get this type of food poisoning. It affects people who eat contaminated fish from certain regions.

The fish at risk of contamination are in waters with coral reefs (where the algae that make ciguatoxin live). This includes fish in the Caribbean and in the South Pacific Ocean. Regions with coral reefs in the U.S. include waters off the coast of:

• Southern Florida.
• The Bahamas.
• The U.S. and British Virgin Islands.
• Puerto Rico.
• Hawaii.

Of course, fish caught in these waters are shipped worldwide. The risk for food poisoning has less to do with where you’re dining and more to do with where the fish you’re eating was caught.

What kind of fish have ciguatera?

Over 400 species of fish make a snack of the tiny fish that dine on dinoflagellates. And any of them can give you food poisoning if you eat them. Most are large predatory reef fish, like barracudas, moray eels and amberjacks.

Some of the most common types responsible for ciguatera include:

• Amberjack.
• Barracuda.
• Grouper.
• Moray eel.
• Parrot fish.
• Red snapper.
• Sea bass.
• Spanish mackerel.
• Sturgeon.
• Surgeonfish.

How do you know if a fish has ciguatoxin?

You don’t — unless it’s tested in a lab. In the U.S., the Food and Drug Administration (FDA) has labs that can test fish for ciguatoxin. But this isn’t helpful if you’re preparing the fish or just enjoying a fish dinner on date night.

A fish with ciguatoxin doesn’t smell, taste or look any different from a fish without it. You can’t remove the toxin by freezing or cooking it. This is one of the challenges of preventing ciguatera fish poisoning. It’s impossible to detect the toxin without lab tests, and you can’t remove it during food prep.

How common is ciguatera?

It’s the most common type of food poisoning involving fish. There are about 50,000 cases reported worldwide annually, but it’s likely more cases get treated but not reported.

Scientists project that cases of ciguatera may increase as climate change causes environmental shifts that are harmful to coral reefs but good for Gambierdiscus toxicus (the specific dinoflagellate responsible for ciguatera). The algae thrive around dead or dying coral reefs.

Still, many factors play a role in dinoflagellate growth, including the temperature of the water, how salty it is (salinity) and its exposure to light. Scientists continue to study these factors as they track and monitor the places where ciguatoxin-producing dinoflagellates are most likely to grow.

What are the symptoms of ciguatera fish poisoning?

Symptoms usually appear within the first six hours of eating contaminated fish. They may start as soon as 30 minutes after eating the fish or up to a day later.

Symptoms include:

• Nausea and vomiting.
• Diarrhea.
• Weakness and fatigue.
• Headache.
• Blurred vision.
• Hallucinations.
• Dizziness and vertigo.
• Heavy sweating.
• Intense itching.
• Teeth that feel achy or loose.
• Burning or metallic taste in your mouth.
• Pain in your muscles, joints or abdomen.
• Numbness or tingling in your mouth, fingers and toes.

The sensation that hot objects feel cold and cold objects feel hot (allodynia).

More severe (but less common) symptoms include:

• Chills.
• Skin rash.
• Paralysis.
• Watering mouth and eyes.
• Shortness of breath (dyspnea).
• Slow heartbeat (bradycardia).
• Low blood pressure (hypotension).

What causes ciguatera?

Ciguatera is your body’s response to ingesting ciguatoxin, a substance produced by a specific type of marine algae. Ciguatoxin becomes more potent and harmful as it travels through the food chain — from little fish to big fish to humans. For example, concentrations of ciguatoxin increase in the digestive systems of the bigger tropical fish that eat the little fish. Concentrations are especially high in the fish’s head, intestines, liver and eggs.

Eating contaminated fish exposes your nerves to the toxin, changing how they operate. The result is a host of symptoms, including those related to your:

• Digestive system (like nausea and vomiting).
• Nervous system (like weakness, numbness, tingling and pain).
• Cardiovascular system (like a slow heart rate).

How does it spread?

You get ciguatera by eating contaminated fish.

Some breastfeeding (chestfeeding) mothers (gestational parents) with ciguatera have reported symptoms like diarrhea and rash in infants. This means it’s possible to transmit the toxin while nursing your baby. You shouldn’t feed your infant from your body until you’ve recovered.

What are the complications of ciguatera?

You may vomit so much that you become dehydrated. You may need intravenous (IV) fluids in the ER to ensure your body has enough fluid. Life-threatening complications include respiratory or heart failure. Although ciguatera isn’t usually fatal, getting to an ER is essential to prevent potentially fatal complications from progressing.

How is ciguatera diagnosed?

The only way to know for sure if you have ciguatera is to test the fish in a lab for the toxin. But there’s no time for this during an ER visit.

Instead, your healthcare provider will diagnose you based on your symptoms and whether you’ve recently eaten one of the high-risk fish.

How is ciguatera treated?

There isn’t an antidote for the toxin. Instead, treatment involves symptom management and preventing life-threatening complications.

Treatment may include:

• Activated charcoal: If you’ve eaten within the last four hours and you’re not at risk of dehydration, your provider may give you activated charcoal to induce vomiting. Activated charcoal may also absorb some of the toxin.
• Osmotic diuretics: These medicines remove water from your body and can help reduce nervous system symptoms. If you’re stable and not at risk of dehydration, you may get a medicine called mannitol (Osmitrol®) via an IV to ease symptoms.
• Pain medications: You may need gabapentin or amitriptyline to ease nerve pain. They may also help with side effects like extreme itching. For more generalized pain, you may need a nonsteroidal anti-inflammatory drug (NSAID) or acetaminophen (Tylenol®).

Some foods cause people who’ve recovered from ciguatera to experience symptoms all over again. So, your provider will advise you to avoid these foods as part of your treatment.

For at least the next six months, you’ll need to avoid:

• Alcohol (which can also increase your risk of experiencing symptoms affecting your heart).
• Fish (even uncontaminated fish).
• Nuts.
• Seeds.

How soon after treatment will I feel better?

For most people, symptoms last a few days or weeks. In some cases, though, symptoms continue for months or (rarely) years. Symptoms affecting your nervous system are usually the ones that tend to last longest.

Can ciguatera fish poisoning be prevented?

The only way to prevent ciguatera is to avoid eating contaminated fish. The trouble is, outside of lab testing, there’s no way to know if a specific fish contains the toxin.

You can reduce your risk by steering clear of the reef fish most likely to contain ciguatera. And if you do eat these fish, definitely avoid consuming the parts that contain the highest concentrations of the toxin, including the head, intestines, liver and eggs.

What can I expect if I have ciguatera?

Most people start feeling better within a few weeks, although it may take months or even years to feel free of all nervous system symptoms. If you avoid food and drinks (like alcoholic beverages) that can trigger a symptom recurrence, you should eventually feel better.

Fewer than 1 in 1,000 people die from ciguatera poisoning. Deaths usually relate to complications affecting your heart and lungs — complications that can be avoided if you get to an ER.

When should I go to an ER?

If you’ve recently eaten a type of fish that lives in tropical and subtropical waters and you’re experiencing any of the symptoms of ciguatera, get to an ER immediately. Acting fast can prevent potentially life-threatening complications.

What questions should I ask my healthcare provider?

• What treatments will I need to manage symptoms?
• How frequently will you check on my progress as I recover?
• What foods and drinks should I avoid in the days/weeks/months ahead?
• How can I remain healthy and active while recovering from food poisoning?
• Should I steer clear of eating reef fish in the future?