Ciguatera poisoning, caused by the ingestion of fish contaminated with ciguatoxins, represents one of the most common forms of seafood poisoning. Ciguatoxins accumulate up the food chain in fish species found in tropical and subtropical waters. In the US, the risk mainly comes from Caribbean fish. Ciguatera poses both acute and chronic health problems that necessitate awareness and understanding for prevention.
What is Ciguatera?
Ciguatera poisoning results from eating fish contaminated with ciguatoxins. These naturally occurring toxins are produced by the marine dinoflagellate Gambierdiscus toxicus. The dinoflagellate is found in algae growing on reefs. Vegetarian fish that eat the algae first ingest and accumulate ciguatoxins. The vegetarian fish are then eaten by larger and larger fish, and the toxin accumulates in the marine food chain. When a person eats a fish with high levels of ciguatoxin, he or she typically will have symptoms 4-6 hours later.
Reef fish such as barracuda (the most likely), grouper, and snapper have the highest likelihood of having high levels of ciguatoxin. However, any larger fish from Caribbean waters may contain ciguatoxins. Ciguatoxins are not broken down by freezing or cooking.
Acute Ciguatera
The first symptoms typically occur 4-6 hours after ingestion of ciguatoxins and may occur up to 24 hours. Neurological symptoms may occur in a few hours and up to 3 days after the meal.
Symptoms are gastrointestinal, neurological, and cardiac. Rarely, coma, respiratory paralysis, and death can occur.
Gastrointestinal: nausea, vomiting, diarrhea, painful bowel movements, and abdominal pain.
Neurological: tingling, numbness, teeth feeling loose, painful limbs, itching, muscle aches, joint aches, vertigo, trouble walking, and a characteristic hot-cold sensory reversal where hot objects feel cold and vice versa. Typically, numbness and tingling start around the mouth.
Cardiovascular: irregular heartbeat, fluid buildup in the lungs, low blood pressure, and a slow heart rate (bradycardia). Cardiac symptoms may take 1-5 days to develop.
Other: metallic taste, sweating, chills, painful urination, painful ejaculation
Chronic Ciguatera
To understand how ciguatera can become a chronic illness, one must know a little bit about the size of ciguatoxin. Ciguatoxin has a low molecular weight of about 1,000 g/mol or daltons. Compare this to a single influenza virus, which is 3,900,000 daltons. The immune system can quickly clear larger molecular structures, such as viruses, compared to tiny toxins. Another comparison is botulinum toxin (Botox), which is 150,000 daltons. When injected with this toxin, the effects last approximately 3 months, at which point the body has finally cleared the toxin. Further, some people’s immune systems will struggle to clear the toxin due to the HLA genotype, which will result in chronic symptoms lasting many months or years. Similar to illness from exposure to a water-damaged building, ciguatera illness is a biotoxin illness and can produce Chronic Inflammatory Response Syndrome (CIRS).
Symptoms: Chronic ciguatera is primarily characterized by persistent or recurrent neurological and systemic symptoms, including:
Fatigue and muscle weakness.
Depression, anxiety, or mood disturbances.
Long-term sensory abnormalities, particularly exacerbation of hot-cold reversal.
Prevention & Conclusion
When it comes to ciguatera, an ounce of prevention is really worth a pound of cure. Even locally, avoid buying fish from tropical waters. When visiting the Caribean and the Florida Keys, never eat parrot fish, barracuda, grouper, or "local fish." Even mahi-mahi has been a source of ciguatoxin, causing human illness. Shellfish is generally safe.
You can read more about CIRS and immune system genotypes that cannot quickly clear toxins in the blog post tagged to this post.
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