The Acute Toxicity of Tetrodotoxin and Tetrodotoxin–Saxitoxin Mixtures to Mice by Various Routes of Administration

Abstract

Tetrodotoxin (TTX) is a potent neurotoxin associated with human poisonings through the consumption of pufferfish. More recently, TTX has been identified in bivalve molluscs from diverse geographical environments, including Europe, and is therefore recognised as an emerging threat to food safety. A recent scientific opinion of the EFSA Panel on Contaminants in the Food Chain recognised the need for further data on the acute oral toxicity of TTX and suggested that, since saxitoxin (STX) and TTX had similar modes of action, it was possible that their toxicities were additive so could perhaps be combined to yield one health-based guideline value. The present study determined the toxicity of TTX by various routes of administration. The testing of three different mixtures of STX and TTX and comparing the experimentally determined values to those predicted on the basis of additive toxicity demonstrated that the toxicities of STX and TTX are additive. This illustrates that it is appropriate to treat TTX as a member of the paralytic shellfish group of toxins. Since the toxicity of TTX was found to be the same as STX by feeding, a molar toxicity equivalence factor of 1.0 for TTX can be applied.

Survey of Tetrodotoxin in New Zealand Bivalve Molluscan Shellfish over a 16-Month Period

“…To assess the contribution of TTX to the total toxicity of the sample, it was subjected to a mouse bioassay (AOAC959.08) that targets these toxins and was found to be above regulatory limit at 1.3 mg STX·2HCl eq/kg. The result from the mouse bioassay is consistent with the expected underestimation of TTX toxicity due to its slower death response time than saxitoxin [ 24 ]. Shellfish sampled from the same site pre- and post-this result contained only trace TTX levels, demonstrating the rapid appearance and disappearance of TTX in shellfish from this site ( Table 2 ).…”

“…When assessing sample toxicity, co-occurrence of TTX with paralytic shellfish toxins needs to be considered. This is because both TTX and STX bind to voltage-gated sodium channels and our research has shown that they have additive toxicological effects [ 24 ]. The PSP mouse bioassay, which is still used for regulatory monitoring in some countries, is not able to distinguish TTX from saxitoxin group toxins (paralytic shellfish toxins).…”

“…Most of the information available relates to acute toxicity through intraperitoneal injection to mice, and this route of administration is of questionable relevance, given that seafood is consumed orally rather than injected. To address this we have recently generated robust toxicity information for TTX via oral administration (gavage and voluntary feeding) and demonstrated that the toxicities of STX and TTX are additive [ 24 ]. Data gaps still exist.…”

Public Health Risks Associated with Tetrodotoxin and Its Analogues in European Waters: Recent Advances after The EFSA Scientific Opinion

“…Further to the need for further data on the acute oral toxicity of TTX, the EFSA opinion also recognized the possibility that, due to their similar modes of action, toxicities of STX and TTX were additive, so they could perhaps be combined to yield one health-based guideline value. In this context, a study was conducted by Finch et al [65] to determine the toxicity of TTX by a number of different routes of exposure, including feeding, and at the same time to investigate whether the toxicities of STX and TTX are additive. NOAELs for indivicual TTX and STX by feeding were also determined to allow for a better estimation of the ARfD.…”

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

“…Accumulation of these toxins in edible bivalves is important to keep under observation in the area of seafood safety as they belong to the most neurotoxic substances known to induce serious illness [ 7 ] with the risk of fatal intoxication effects when ingested in higher concentrations [ 8 , 9 , 10 ]. There are also reports that PST (saxitoxin, STX) and TTX have been found together in marine organisms including bivalves [ 7 , 11 ] and Finch et al demonstrated that their toxicities are additive. 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].…”