Red Snapper, a large reef fish, is associated with ciguatera.
Vicky Bertagnolli ©2024, Clemson Extension
What is Ciguatera?
Ciguatera is a unique type of food poisoning caused by eating fish that are contaminated with ciguatoxin. This natural toxin originates in tropical and sub-tropical waters. The toxins are produced by microscopic organisms, known as dinoflagellates, Gambierdiscus toxicus. They attach to macroalgae and seagrasses primarily found in coral reef ecosystems. The toxin is passed along through a marine food chain of higher-order predators. Small fish ingest the toxic microorganisms and are then consumed by larger fish, passing on the toxin. As the ciguatoxin moves up the food chain it become more concentrated in fish tissues. When humans consume predatory coral reef fish with high concentrations of toxin, they can become sick. The larger the fish the greater the potential for poisoning.
Ciguatera illness generally occurs in the tropical regions of the world. It is the most common, non-bacterial, seafood illness. Presently, ciguatera is relatively limited in the United States and occurs less often than many common food bacterial poisonings. However, expanding distribution of tropical fishes, increasing vacation travel, and a warmer marine climate make it an illness of concern.
Where Does Ciguatera Occur?
Ciguatera occurs in marine waters near tropical reefs. The common boundaries referenced are for tropical reef waters between latitudes 35° south and north. Within these areas the occurrence is unpredictable and patchy, both in distribution and time. The majority of reefs are not ciguatoxic and outbreaks are usually localized. Thus, knowledge of the ciguatoxic areas or reefs is usually based on the local experience of fishermen and consumers.
Ciguatera is not a concern for fish caught in South Carolina waters but should be a consideration for people traveling to Caribbean areas. Based on seafood origins, primary areas of occurrence for the United States are Hawaii, Guam, and Puerto Rico where fish from tropical sources are consumed.
Which Seafoods Can Be Ciguatoxic?
Potentially any tropical marine fish participating in a food chain with ciguatoxin could become ciguatoxic. Some common fish associated with ciguatoxin are barracuda, grouper, amberjack, red snapper, moray eel, hogfish, mackerel, surgeonfish, and parrotfish.
Unfortunately, the usefulness of a list of ciguatoxic fish is questionable because of the diversity of fish species and the variety of names used. For example, local fisherman may refer to a variety of fish as “jacks” or “snappers” when they are actually a mackerel, wrasse, or other species. Certain species of snapper and grouper are not a risk for ciguatera, yet their popular reputation suffers because they are misidentified.
How is Ciguatera Identified?
There is no simple, reliable test kit available to the public. Determinations for ciguatera usually are limited to diagnosis based on symptoms. Symptoms following ingestion of a ciguatoxic fish can begin within less than six hours. This rapid onset is a primary reason for close food association and reporting of this seafood borne illness.
Initial symptoms are gastrointestinal, including nausea, cramping, and vomiting. This is followed by neurological discomforts: headaches, flushing, muscular aching, and weakness, tingling and numbing sensation of the lips, tongue and mouth, dizziness, myalgia, and arthralgia. More severe cases have experienced a cold-to-hot sensory reversal such that cold objects feel hot and hot objects feel cold. Victims usually recover within a few days, but severe neurological disorders may persist for months and sometimes for years. Symptoms may reoccur following alcohol consumption or again eating ciguatoxic fish.
The lengthy duration of neurological symptoms is unique, but many of these symptoms are similar for other food poisonings. In the event of food poisoning, consumers should note other foods eaten and try to retain any portions of a meal to better judge the cause. Ciguatera can be mis-diagnosed as more common forms of food poisoning.
What if You Suspect Ciguatera?
- Consult a physician, explaining your concern, types and amount of food eaten, and when the symptoms began. Rapid diagnosis by a physician and follow-up treatment is important.
- Try to obtain samples of the meal, particularly the fish, to help determine the cause. These samples should be tightly packaged and frozen for any subsequent analysis. Recalling the various foods eaten within 24 hours could indicate other possible causes.
- Try to verify the species and size of the suspect fish and how it was cooked and handled prior to cooking. These concerns are essential to confirming ciguatera versus other food poisonings. The heat-stable ciguatoxin is not destroyed by cooking and frozen storage. Knowledge of prior quality or partial mishandling could implicate a different form of food poisoning caused by partial spoilage, i.e., scombroid or histamine fish poisoning.
- Consult with other professionals in public health, food safety regulation or academic research, who can better advise your physician. Many physicians are not familiar with ciguatera.
How to Avoid Ciguatera
Ciguatoxic fish cannot be detected by appearance, taste, or smell. Raw and cooked whole fish, fillets or parts have no signs of spoilage, discoloration, or deterioration.
Thus, prior knowledge of potential ciguatoxic areas and fish remains the best source of caution in avoiding this distinct form of food poisoning. Consumers purchasing tropical marine fish from reef waters should frequent reputable dealers and restaurants. Vacationers and experienced recreational fishermen should exercise caution in areas of concern for particular tropical species. Consumers should not eat foods prepared from the heads or internal portions of tropical reef fish species.
Source:
- National Food Safety Database. Ciguatera. Prepared by Steven Otwell, December 1989.
- European Centre for Disease Prevention and Control. February 2021. https://www.ecdc.europa.eu/en/all-topics-z/ciguatera-fish-poisoning/facts-ciguatera-fish-poisoning
- Florida Department of Health. Seafood Safety. May 2024. https://www.floridahealth.gov/environmental-health/aquatic-toxins/seafood-safety/index.html
Originally published 08/99
