Ciguatera

Ciguatera is a unique type of food poisoning caused by the consumption of marine species that harbor natural toxins originating in certain tropical waters. These species and locations are linked by a food chain, which generates and accumulates a heat-resistant, acid-stable collection of toxic substances known as ciguatoxin. The initial culprits are certain species of microplankton or dinoflagellates that form the toxins that higher-order predators and man consume. These natural toxins can concentrate as they move up the food chain, but their adverse effects appear limited to man.

Ciguatera Poisoning:

Vertebrate fish containing toxins capable of causing human illness can be divided into three major groups based on the location of the toxin. Ichthyosarcotoxic fish (hagfish, lamprey, puffer, snapper, barracuda) contain toxin in their musculature, viscera, skin or mucus, and are responsible for most fish poisonings. Ichthyo-ootoxic fish contain toxins in their gonads, and ichthyohemotoxic species contain toxins in their blood. The most frequently implicated ichthyosarcotoxism is ciguatera. Ciguatera poisoning is on the increase because of a recurrence of it in normally edible fish, the sporadic and unpredictable nature of the toxicity and the increased demand for seafood worldwide.

Side Effects of Ciguatera

Ciguatera is a toxin which sometimes contaminates reef fish. Symptoms may be delayed up to 30 hours. Sensitization can render subsequent ingestion far more dangerous.

Detection:

Ciguatoxic fish appear normal in all ways including the smell and taste of the flesh. The detection of ciguatoxic fish has been based largely on unsubstantiated and erroneous rules of thumb such as: A lone fish separated from the rest of the school should not be touched; if ants are repelled by a fish, or a turtle refuses to eat it, it is probably unsafe for humans; if a thin slice of the fish does not show a "rainbow effect' when held up to the sunlight, it is inedible; a silver spoon will tarnish if placed in the cooking pot with a toxic fish. There are no distinguishing routine laboratory features of ciguatera toxin, however, testing of the toxin source is available in some endemic areas. The stick enzyme immunoassay provides promise as a simple widespread test for clinical laboratories and the fishing industry. Other tests include the mouse intraperitoneal injection and radioimmunoassay (RIA) and guinea pig atrium assay. RIA has been used to screen amberjack in Hawaii, but this method is time consuming. An electrophoretic technique to evaluate potentially toxic fish has been described but requires further evaluation.

Summary:

Although a common source of fish-induced poisoning, ciguatera is little known by the general public and poorly understood by health practitioners. The ingestion of large reef fish, especially snappers, jacks, parrotfish and barracuda, is associated with this illness, and consumption of these fish by natives and tourists in areas of recent reef disturbances should be avoided.