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Fish and Shellfish Poisoning

At certain times of the year, some species of fish and shellfish contain poisonous biotoxins. This is true even if they are well-cooked. The CDC says it's an under-recognized risk for travelers. It's a greater risk for travelers in the tropics and subtropics. 

Certain fish can cause ciguatera fish poisoning. These include:

  • Grouper

  • Barracuda

  • Moray eel

  • Sturgeon

  • Sea bass

  • Red snapper

  • Amberjack

  • Mackerel

  • Parrot fish

  • Surgeonfish

  • Triggerfish

The CDC advises never eating moray eel or barracuda. Other types of fish that may contain the toxin at unpredictable times include sea bass and a wide range of tropical reef and warm-water fish. Fish containing these toxins don't look, smell, or taste bad. Cooking, marinating, freezing, or stewing does not destroy the toxin.

The risk of ciguatera poisoning exists in all tropical and subtropical waters where reef fish are eaten. These include the West Indies, the Pacific Ocean, and the Indian Ocean.

Here are 2 other forms of poisoning that can happen from naturally occurring toxins in fish:

  • Tetrodotoxin, sometimes called pufferfish or fugu poisoning

  • Scombroid poisoning

Where is the risk of ciguatera poisoning the greatest?

Reef fish from the tropical and subtropical waters of the West Indies, the Pacific Ocean, and the Indian Ocean pose the greatest threat. Cases have been reported in the U.S. in Hawaii, Guam, Puerto Rico, U.S. Virgin Islands, and Florida. A few isolated cases of ciguatera poisoning have even been noted along the eastern seaboard of the U.S.

More than 400 species of fish, particularly reef fish, are thought to contain the toxin for ciguatera poisoning.

What are the symptoms of ciguatera poisoning?

Symptoms of ciguatera poisoning often start from a few minutes to 6 hours after eating the toxic fish. They include many gastrointestinal, neurological, and cardiovascular problems. Each person may have different symptoms. But these are the most common symptoms:

  • Nausea

  • Vomiting

  • Watery diarrhea

  • Belly (abdominal) pain

  • Headache

  • Numbness and tingling feeling around the mouth, arms, and legs

  • Tiredness (fatigue)

In more severe cases, you may have muscle pains, dizziness, and sensations of temperature reversal, where hot things seem cold and cold things seem hot. You may also have irregular heart rhythms and low blood pressure. 

These symptoms often go away in a few days. But they may last up to 4 weeks. They can be caused by other health conditions. Always talk with your healthcare provider for a diagnosis.

Treatment for ciguatera poisoning

Treatment for ciguatera poisoning includes easing symptoms and treating any complications. There is no specific antidote for the toxin itself. Generally, recovery takes from a few days to a few weeks. 

What is tetrodotoxin?

Tetrodotoxin is also called pufferfish poisoning or fugu poisoning. It's a much rarer form of fish poisoning. It may be very serious. It's almost exclusively linked to eating pufferfish from waters of the Indo-Pacific regions. There have also been cases of poisonings from pufferfish from the Atlantic Ocean, Gulf of Mexico, and Gulf of California. Some of these include deaths. Pufferfish poisoning is a continuing problem in Japan.

What are the symptoms of pufferfish poisoning?

Symptoms often start between 20 minutes and 3 hours after eating the poisonous pufferfish. Each person may have different symptoms. But these are the most common symptoms:

  • Numb lips and tongue

  • Numb face, arms, or legs

  • Feeling of lightness or floating

  • Headache

  • Nausea and vomiting

  • Belly pain

  • Diarrhea

  • Slurred speech

  • Trouble walking

  • Extensive muscle weakness

  • Convulsions

  • Trouble breathing

  • Mental impairment

  • Irregular heartbeat

Death can happen within 4 to 6 hours of poisoning. Get medical care right away.

Treatment for pufferfish poisoning

Treatment for pufferfish poisoning consists of limiting how much of the toxin the body absorbs. It also includes easing symptoms and treating life-threatening complications. There is no known antidote for tetrodotoxin. 

What is scombrotoxin?

Scombrotoxin is also called scombroid poisoning or histamine poisoning. It happens after eating fish that have high levels of histamine due to incorrect food handling. It's one of the most common forms of fish poisoning in the U.S. and worldwide. 

Certain fish have high amounts of histidine. As a result of poor refrigeration or preservation, bacteria turn the histidine into histamine. This leads to scombroid poisoning. Contaminated fish may look and taste fresh. But some may taste peppery, spicy, or bubbly. The toxin may form even if the fish has been stored at too high a temperature for only a short time. 

This form of fish poisoning happens worldwide in temperate and tropical waters. It can happen after eating:

  • Mahi mahi (dolphin fish)

  • Albacore tuna

  • Bluefin and yellowfin tuna

  • Bluefish

  • Mackerel

  • Sardines

  • Anchovy

  • Herring

  • Marlin

  • Amberjack

  • Abalone

What are the symptoms of scombroid poisoning?

Symptoms often start within minutes to an hour after eating affected fish. They typically last 3 hours. But they can last for a few days. Each person may have different symptoms. But the most common symptoms are:

  • Tingling or burning feeling in the mouth

  • Rash on the face and upper body

  • Wheezing or shortness of breath

  • Drop in blood pressure

  • Throbbing headache

  • Hives and itching of skin

  • Nausea

  • Vomiting

  • Diarrhea

  • Itching

  • Heart palpitations

These symptoms can be caused by other health conditions. Many cases of fish allergy are actually scombroid poisoning. Always talk with your healthcare provider for a diagnosis. 

Treatment for scombroid poisoning

Treatment for scombroid poisoning is generally not needed. Symptoms often go away without treatment within 12 to 48 hours. This poisoning is rarely life-threatening. Treatment could include antihistamines, such as diphenhydramine and cimetidine.

Specific treatment for all fish and shellfish poisoning is based on:

  • Your overall health and medical history

  • Extent of the disease

  • Your tolerance for certain medicines, procedures, and therapies

  • Your opinion or preference

Online Medical Reviewer: Chris Southard RN
Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 11/1/2023
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