First Report on the Occurrence of Tetrodotoxins in Bivalve Mollusks in The Netherlands

Abstract

Tetrodotoxin (TTX) is traditionally associated with seafood from tropical regions, but recently TTX was detected in bivalve mollusks in more temperate European waters. In The Netherlands it was therefore decided to monitor TTX in shellfish harvested from Dutch production areas. All shellfish production areas were monitored in 2015, 2016 and 2017. Samples were analyzed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). In total 1063 samples were investigated, and the highest concentrations were observed in 2016, i.e., 253 µg TTX/kg in oysters and 101 µg TTX/kg in mussels. No TTX analogues, with the exception of 4-epi-TTX in one single sample, were found and contaminated samples also showed positive results in the neuro-2a bioassay. The occurrence of TTX seems to be consistent over the last three years with the highest concentrations observed annually in late June. The causative organism and the reasons why specific Dutch production areas are affected while others are not, are still unclear. Initially in The Netherlands an action limit of 20 µg TTX/kg was used to ensure the safety of consumers (2016), but recently The European Food Safety Authority (EFSA) established an acute reference dose, and based on a high portion size of consuming 400 g mussels, this dose was translated into a safe concentration of 44 µg TTX per kg for shellfish. This concentration is now used as an action limit and TTX is formally included in the Dutch shellfish monitoring program.

First Detection of Tetrodotoxin in Bivalves and Gastropods from the French Mainland Coasts

“…Similar precision was obtained by Nzoughet et al in gastropods [25]. The sensitivity obtained was better or of the same order as most other published studies [12,14,24,25,27], and considered totally fit for purpose, though lower than the sensitivities obtained by Leão et al and Turner et al [13,21]. LOQ values of the latter are respectively of 0.9 and 0.8 µg TTX/kg.…”

“…Several European studies have been conducted since the EFSA risk assessment [12][13][14][15][16]. All these new data were obtained using hydrophilic interaction liquid chromatography associated with tandem mass spectrometry (HILIC-MS/MS).…”

Multi-Toxin Quantitative Analysis of Paralytic Shellfish Toxins and Tetrodotoxins in Bivalve Mollusks with Ultra-Performance Hydrophilic Interaction LC-MS/MS—An In-House Validation Study

“…More than 50 PST and 30 TTX analogues are known to exist worldwide [ 7 , 12 ], of which a certain number of PSTs are included in the European Commission (EC) regulation for marine toxins in bivalve mollusks, that currently do not cover TTX [Regulation (EC) No 853/2004]. During the recent years, the presence of TTX has been reported in different marine organisms, including gastropods and bivalve mollusks, from diverse geographic regions within European waters [ 3 , 13 , 14 , 15 , 16 ]. The changing climate with longer periods of elevated temperatures in combination with the presence of nutrients create the conditions for new events in the marine environment.…”

Evaluation of the Occurrence of Tetrodotoxin in Bivalve Mollusks from the Portuguese Coast

“…A survey study carried out in 2013-2014 and then between 2014 and 2016 revealed TTX concentrations up to 253 µg kg −1 in Pacific oysters (Magallana gigas, previously known as Crassostrea gigas) collected at the south coast of England [3,4]. Following the initial findings of [3], TTX was also detected in mussels and oysters from the Netherlands in 2015 [5], which made the Dutch authorities to issue an advice in 2016 and proposing to apply a zero tolerance for TTX in shellfish, meaning that bivalves would only enter the markets with non-detectable levels of TTX after analysis with analytical methods able to detect a concentration of 20 µg kg −1 or lower [6]. In 2017, the European Food Safety Authority (EFSA) stated a scientific opinion, following a request from the European Union, on the risk related to the presence of TTX and TTX analogues in marine bivalves and gastropods [7].…”