At certain times of the year, various species of fish and shellfish contain poisonous biotoxins, even if well cooked. According to the CDC, it is considered an under-recognized risk for travelers, specifically in the tropics and subtropics. 

Certain fish—groupers, barracudas, moray eel, sturgeon, sea bass, red snapper, amberjack, mackerel, parrot fish, surgeonfish, and triggerfish—can cause ciguatera fish poisoning. The CDC recommends 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 do not 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 of the West Indies, the Pacific Ocean, and the Indian Ocean, where these reef fish are eaten.

Two other forms of poisoning can happen from naturally occurring toxins in fish: tetrodotoxin, sometimes called pufferfish poisoning or fugu poisoning, and 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 United States 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 United States.

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 generally appear between a few minutes and 6 hours after the toxic fish has been eaten. These include a variety of gastrointestinal, neurological, and cardiovascular abnormalities. The following are the most common symptoms of ciguatera poisoning. However, each individual may experience symptoms differently. Symptoms may include:

• Nausea

• Vomiting

• Watery diarrhea

• Headache

• Numbness and tingling about the mouth and extremities

In more severe cases, the person may suffer muscle pains, dizziness, and sensations of temperature reversal, where hot things seem cold and cold things seem hot. Irregular heart rhythms and low blood pressure may also be experienced. Ciguatera poisoning symptoms typically resolve within several days, but may last up to 4 weeks. The symptoms of ciguatera poisoning may resemble other medical conditions. Always talk with your healthcare provider for a diagnosis.

Treatment for ciguatera poisoning

Treatment for ciguatera poisoning involves relieving the symptoms and treating any complications. There is no specific antidote for the toxin itself. Generally, recovery takes from several days to several weeks. 

What is tetrodotoxin?

Tetrodotoxin, also called pufferfish poisoning or fugu poisoning, is a much rarer form of fish poisoning. Yet, it is potentially very serious. This is almost exclusively associated with eating the pufferfish from waters of the Indo-Pacific regions. There have also been several reported cases of poisonings, including fatalities, from pufferfish from the Atlantic Ocean, Gulf of Mexico, and Gulf of California. Pufferfish poisoning is a continuing problem in Japan.

What are the symptoms of pufferfish poisoning?

Symptoms generally appear between 20 minutes and 3 hours after eating the poisonous pufferfish. The following are the most common symptoms of pufferfish poisoning. However, each individual may experience symptoms differently. Symptoms may include:

• Numbness of lips and tongue

• Numbness of face and extremities

• Sensations of lightness or floating

• Headache

• Nausea and vomiting

• Abdominal pain

• Diarrhea

• Slurred speech

• Difficulty walking

• Extensive muscle weakness

• Convulsions

• Respiratory distress

• Mental impairment

• Cardiac arrhythmia

Death can happen within 4 to 6 hours of poisoning. It is essential to seek immediate medical attention.

Treatment for pufferfish poisoning

Treatment for pufferfish poisoning consists of limiting the body's absorption of the toxin, relieving symptoms, and treating life-threatening complications. There is no known antidote for tetrodotoxin. 

What is scombrotoxin?

Scombrotoxin, also called scombroid poisoning or histamine poisoning, happens after eating fish that contain high levels of histamine due to improper food handling. It remains one of the most common forms of fish poisoning in the U.S. and worldwide. These fish, which include mahi mahi (dolphin fish), albacore tuna, bluefin and yellowfin tuna, bluefish, mackerel, sardines, anchovy, herring, marlin, amberjack, and abalone, have high amounts of histidine. As a result of inadequate refrigeration or preservation, bacteria convert the histidine to histamine. This leads to scombroid poisoning. Contaminated fish may appear and taste fresh, although some may taste "peppery," "spicy," or "bubbly." The toxin may form even if the fish has only been temporarily stored at too high a temperature. 

This form of fish poisoning happens worldwide in temperate and tropical waters.

What are the symptoms of scombroid poisoning?

Symptoms generally appear within minutes to an hour after eating affected fish. They typically last 3 hours, but can last several days. The following are the most common symptoms of scombroid poisoning. However, each individual may experience symptoms differently. Symptoms may include:

• Tingling or burning sensations 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

The symptoms of scombroid poisoning may resemble other medical 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 unnecessary. Symptoms usually resolve within 12 hours and scombroid 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 specific medicines, procedures, and therapies

• Your opinion or preference