Ciguatera poisoning in French Polynesia: A review of the distribution and toxicity of Gambierdiscus spp., and related impacts on food web components and human health.

Ciguatera Poisoning (CP) is a seafood poisoning highly prevalent in French Polynesia. This illness results from the consumption of seafood contaminated with ciguatoxins (CTXs) produced by Gambierdiscus, a benthic dinoflagellate. Ciguatera significantly degrades the health and economic well-being of local communities largely dependent on reef fisheries for their subsistence. French Polynesia has been the site of rich and active CP research since the 1960's. The environmental, toxicological, and epidemiological data obtained in the frame of large-scale field surveys and a country-wide CP case reporting program conducted over the past three decades in the five island groups of French Polynesia are reviewed. Results show toxin production in Gambierdiscus in the natural environment may vary considerably at a temporal and spatial scale, and that several locales clearly represent Gambierdiscus spp. "biodiversity hotspots". Current data also suggest the "hot" species G. polynesiensis could be the primary source of CTXs in local ciguateric biotopes, pending formal confirmation. The prevalence of ciguatoxic fish and the CTX levels observed in several locales were remarkably high, with herbivores and omnivores often as toxic as carnivores. Results also confirm the strong local influence of Gambierdiscus spp. on the CTX toxin profiles characterized across multiple food web components including in CP-prone marine invertebrates. The statistics, obtained in the frame of a long-term epidemiological surveillance program established in 2007, point towards an apparent decline in the number of CP cases in French Polynesia as a whole; however, incidence rates remain dangerously high in some islands. Several of the challenges and opportunities, most notably those linked to the strong cultural ramifications of CP among local communities, that need to be considered to define effective risk management strategies are addressed.

Ciguatera risk assessment in two toxic sites of French Polynesia using the receptor-binding assay.

Ciguatera Fish Poisoning (CFP) is a tropical syndrome well known in remote archipelagos where the population is still dependent on fish resources. In order to assess the ciguatera risk in two islands of French Polynesia, Tubuai (Australes) and Nuku Hiva (Marquesas), a study was carried out on both Gambierdiscus populations as well as on various fish species using the receptor-binding assay (RBA) to detect and quantify ciguatoxins. Relationship between RBA data and size or weight of fish was evaluated, and when only few individuals for a particular species were available the trophic level was used to help comparisons between studied areas. According to epidemiological data, toxic versus safe areas were explored and compared in both islands. In Tubuai Island, Gambierdiscus cells were surprisingly absent in the north area, considered as a toxic area, but almost 94% of fishes were classified as RBA+. In contrast, the south area, supposed to be safe, was evolving to be a risky area because of the presence of Gambierdiscus cells and 74% of fishes being RBA+. In Nuku Hiva Island, Gambierdiscus cells were present in the toxic areas, Anaho, Taiohae and Taipivei, with two toxic blooms in Anaho Bay, but none in Terre Déserte, the fishing area of this island. With RBA data, fishes were analyzed to be RBA+ at a high percentage in Anaho and Taiohae, higher than in Taipivei and Terre Déserte areas. In general, our findings were congruent with epidemiological data and the knowledge of local people only for risky fish species.

Progress on chemical knowledge of ciguatoxins.

The chemical data setted up on the ciguatoxins responsible for ciguatera fish poisonings are summarized and discussed. The multiplicity of the toxic compounds isolated from fish and algal material is described. A tentative screening of the principal toxins still on process in the two laboratories has shown that (1) CTX is dominant in carnivorous fish, (2) less polar toxins are dominant in herbivorous fish, (3) CTX precursors are produced by G. toxicus in natura and in culture conditions. The increasing polarity of the toxins in step with the food chain levels supports the hypothesis of an oxidative modification of the precursors during the bio-accumulation in fish.