A 15-Year Retrospective Review of Ciguatera in the Madeira Islands (North-East Atlantic, Portugal)

Abstract

The first ciguatera fish poisoning (CFP) in Portugal dates from 2008 when 11 people reported CFP symptoms after consuming a 30 kg amberjack caught around the Selvagens Islands (Madeira Archipelago). Since then, 49 human poisonings have been reported. The emergence of a new threat challenged scientists and regulators, as methods for toxic microalgae analyses and ciguatoxin (CTX) detection were not implemented. To minimise the risk of ciguatera, the Madeira Archipelago authorities interdicted fisheries in Selvagens Islands and banned the capture of amberjacks weighing more than 10 kg in the entire region of Madeira Archipelago. The accurate identification and quantification of the benthic toxin-producing algae species spreading to new areas require efforts in terms of both microscopy and molecular techniques. Two ciguatera-causing dinoflagellates, Gambierdiscus excentricus and Gambierdiscus australes, were identified in the Madeira Island and Selvagens sub-archipelago, respectively. Regarding the CTX analysis (N2a cell-based assay and LC-MS) in fish, the results indicate that the Selvagens Islands are a ciguatera risk area and that fish vectoring CTX are not limited to top predator species. Nevertheless, advances and improvements in screening methods for the fast detection of toxicity in seafood along with certified reference material and sensitive and selective targeted analytical methods for the determination of CTX content are still pending. This study aims to revise the occurrence of ciguatera cases in the Madeira Archipelago since its first detection in 2008, to discuss the risk management strategy that was implemented, and to provide a summary of the available data on the bioaccumulation of CTX in marine fish throughout the marine food web, taking into consideration their ecological significance, ecosystem dynamics, and fisheries relevance.

Keywords: Gambierdiscus; Macaronesia; ciguatera; ciguatoxins; seafood poisoning.

Figure 4

Fish species potentially acting as CTX vectors in Selvagens Islands coastal waters. Fish representations were adapted from [49].

Figure 1

View of the Selvagem Grande (A) and Selvagem Pequena (B), and iconic wildlife animals, such as the Cory’s shearwater Calonectris borealis (C), the greater amberjack Seriola dumerilli (D), and the barred hogfish Bodianus scrofa (E).

Figure 2

Distribution of Gambierdiscus species in the Macaronesia and the Mediterranean Sea, and the location of the Madeira and Selvagens Islands (NE Atlantic) [5,7,8,9,28,35,36,37].

Figure 3

Gambierdiscus collected from the Madeira and Selvagens Islands. Culture concentrate (A), Gambierdiscus sp. isolated from Madeira in light microscopy (scale bar 25 µm) (B), and G. australes isolated from Selvagens Islands (scale bar 10 µm) (C).