Chemical Hazard: Ciguatera Toxin

Chemical Hazard: Ciguatera Toxin

 

 

Ciguatera toxin is a heat-stable lipid soluble compound, produced by dinoflagellates and concentrated in fish organs, it is odourless and tasteless.

The dinoflagellates are single-celled eukaryotes constituting the phylum Dinoflagellata. Usually considered algae, dinoflagellates of the genus Gambierdiscus (Gambierdiscus toxicus) are mostly marine plankton, but they also are common in freshwater habitats (1-3).

 

Ciguatera toxin tends to accumulate in large predator fish (weight over 2 Kg or about 4.5 lbs), such as the barracuda and other carnivorous reef fish, because they eat other fish that consume toxin-producing alga, which live in coral reef waters. The toxin has highest concentrations in fish visceral and sex organs. The areas of concern for Ciguatera toxin include the Caribbean Sea, Hawaii and coastal Central America.

Pathogenicity: Eating ciguatera-contaminated tropical or subtropical fish is the main way that humans are exposed to the toxin.

Limits in food: In the EU, legislation covering fishery products states that “fishery products containing biotoxins such as ciguatera toxins” cannot be placed on the market, but no methods of analysis are given. In the USA no action limits have so far been established. However, the FDA has proposed guidance levels of <0.1μg kg -1 C-CTX-1 equivalents and <0.01μg kg -1 P-CTX-1 equivalents.

 Sources: This toxin is found in fish most commonly, barracuda, grouper, red snapper, eel, amberjack, sea bass and Spanish mackerel.

 Illness, Symptoms and Complications: Gastrointestinal symptoms and signs (e.g. vomiting, diarrhea, abdominal pain, nausea) develop within 6–24 hours of eating a reportedly good-tasting reef fish.

Cardiac signs may include hypotension and bradycardia, and may necessitate urgent medical care.

Severe cases of ciguatera poisoning may result in shortness of breath, salivation, tearing, chills, rashes, itching, and paralysis.

Neurologic symptoms vary among patients and include the following: paresthesias (numbness and tingling) in the extremities (feet and hands) and oral region, generalized pruritis (itching), myalgia (muscle pain), arthralgia (joint pain), and fatigue. 

Death due to heart or respiratory failure occurs in rare cases.

 Controls to reduce the risk:

For food manufacturers it can be difficult to control or prevent ciguatera toxin within fish products as it is odourless, tasteless and toxic fish cannot be identified by appearance or behaviour. It is also heat stable so cooking, boiling or any other heat treatment will not destroy it (4).

 Testing

The FDA fish testing procedure is a two-tiered protocol involving: 1) in vitro assay, i.e. a high-throughput screen for toxicity consistent with ciguatoxin’s mode of action; and 2) an analytical chemistry technique known as liquid chromatography-mass spectrometry (LC-MS).

 Reference

1. Yasumoto T, Nakajima I, Bagnis R, Adachi R. Finding of a dinoflagellate as a likely culprit of ciguatera. Jpn Soc Sci Fish. 1977; 43: 1021–1026.
2. Cameron J. Effects of ciguatoxin on nerve excitability in rats (part I) J Neurol Sci. 1991; 101:87–92. 
3. Mattei C, Dechraoui MY, Molgó J, Meunier FA, Legrand AM, Benoit E. Neurotoxins targetting receptor site 5 of voltage-dependent sodium channels increase the nodal volume of myelinated axons. J Neurosci Res. 1999; 55: 666–673.
4. Bagnis R. In: Algal toxins in seafood and drinking water. Falconer I, editor. Academic Press; London: 1993. pp. 105–115.