Update on methodologies available for ciguatoxin determination: perspectives to confront the onset of ciguatera fish poisoning in Europe

Abstract

Ciguatera fish poisoning (CFP) occurs mainly when humans ingest finfish contaminated with ciguatoxins (CTXs). The complexity and variability of such toxins have made it difficult to develop reliable methods to routinely monitor CFP with specificity and sensitivity. This review aims to describe the methodologies available for CTX detection, including those based on the toxicological, biochemical, chemical, and pharmaceutical properties of CTXs. Selecting any of these methodological approaches for routine monitoring of ciguatera may be dependent upon the applicability of the method. However, identifying a reference validation method for CTXs is a critical and urgent issue, and is dependent upon the availability of certified CTX standards and the coordinated action of laboratories. Reports of CFP cases in European hospitals have been described in several countries, and are mostly due to travel to CFP endemic areas. Additionally, the recent detection of the CTX-producing tropical genus Gambierdiscus in the eastern Atlantic Ocean of the northern hemisphere and in the Mediterranean Sea, as well as the confirmation of CFP in the Canary Islands and possibly in Madeira, constitute other reasons to study the onset of CFP in Europe [1]. The question of the possible contribution of climate change to the distribution of toxin-producing microalgae and ciguateric fish is raised. The impact of ciguatera onset on European Union (EU) policies will be discussed with respect to EU regulations on marine toxins in seafood. Critical analysis and availability of methodologies for CTX determination is required for a rapid response to suspected CFP cases and to conduct sound CFP risk analysis.

Keywords: CFP; Europe; Gambierdiscus; ciguatera; ciguatoxin; detection methods; methods.

Figure 1

(a) General and specific structures of Pacific ciguatoxins (P-CTXs) (b) Structure of Caribbean ciguatoxins (C-CTX-1).

Figure 1

(a) General and specific structures of Pacific ciguatoxins (P-CTXs) (b) Structure of Caribbean ciguatoxins (C-CTX-1).

Figure 2

Solid-phase extraction clean-up of CTXs containing fish extract for use with the mouse bioassay according to standard preparation procedure ([128] and [131]).

Figure 3

Extraction and purification of CTXs from fish samples (caught in the Pacific and Caribbean) for use with Cell Based Assay and LC-MS analysis [119].

Figure 4

Extraction and rapid purification of CTXs from Pacific fish samples to be used with the Receptor Binding Assay [33].

Figure 5

Rapid extraction and purification procedures for CTX determination in Pacific fish samples using LC-MS/MS analysis (CREM-LC-MS/MS) [124].

Figure 6

Extraction and purification procedure of CTXs from wild and cultured Gambierdiscus spp. cell pellets [33,68,69].

Figure 7

Neuroblastoma (Neuro-2a) cells exposed for 24 hours to P-CTX-1 in the presence or absence (▪) of ouabain (0.1 mM) and veratridine (0.01 mM). The proportion of O and V produced an approximate 20% cell mortality. No toxic effects of P-CTX-1 were measured when Neuro-2a cells were not treated with O and V (▪). P-CTX-1 is toxic to Neuro-2a cells in the presence of O and V (●) with 50% of cell mortality produced with a concentration of 3.3 pg CTX-1 (IC₅₀ = 3.3 pg P-CTX-1 mL⁻¹) [195].

Figure 8

Total ion chromatogram for a fish sample extract containing P-CTX-1 (3.83 min, 0.8 mg/kg), P-CTX-2 (5.01 min, 1.1 mg/kg) and P-CTX-3 (5.35 min, 1.4 mg/kg). Reprinted from [125], reprinted with permission from Elsevier.