An odd pilgrim in the Holy Land

Concentrations of Tetrodotoxin (TTX) and Its Analogue 4,9-Anhydro TTX in Different Tissues of the Silver-Cheeked Pufferfish (Lagocephalus sceleratus, Gmelin, 1789) Caught in the South-Eastern Mediterranean Sea, Lebanon

Pufferfishes are among the best-known marine organisms that accumulate marine biotoxins such as Tetrodotoxin (TTX). In the Mediterranean Sea, the silver-cheeked toadfish Lagocephalus sceleratus is the most reported TTX-bearer, causing many fatal and non-fatal cases. In Lebanon, no previous studies have measured TTX levels although the possibility of TTX-poisoning is high since L. sceleratus is caught in different sizes and can be mistaken with other small fishes. Hence, this study reports TTX and its analogue 4,9-anhydro TTX in L. sceleratus collected from Lebanese waters in the Eastern Mediterranean Sea. The results show that TTX concentrations in fish tissues varied between 0.10 and 252.97 µg/g, while those of 4,9-anhydro TTX oscillated between 0.01 and 43.01 µg/g. Internal organs of L. sceleratus were the most toxic parts of its body, with the highest TTX levels found in gonads (mainly ovaries) and liver, followed by the muscles and skin with concentrations always exceeding the safety level. Toxicity fluctuations of L. sceleratus, its expansion, ecological and economic effects were also elucidated. Based on the present findings, it has been confirmed that L. sceleratus constitutes a health, ecological and economic risks, and therefore its trade in seafood markets should be banned to avoid any potential intoxication.

An Updated Review of Tetrodotoxin and Its Peculiarities

Tetrodotoxin (TTX) is a crystalline, weakly basic, colorless organic substance and is one of the most potent marine toxins known. Although TTX was first isolated from pufferfish, it has been found in numerous other marine organisms and a few terrestrial species. Moreover, tetrodotoxication is still an important health problem today, as TTX has no known antidote. TTX poisonings were most commonly reported from Japan, Thailand, and China, but today the risk of TTX poisoning is spreading around the world. Recent studies have shown that TTX-containing fish are being found in other regions of the Pacific and in the Indian Ocean, as well as the Mediterranean Sea. This review aims to summarize pertinent information available to date on the structure, origin, distribution, mechanism of action of TTX and analytical methods used for the detection of TTX, as well as on TTX-containing organisms, symptoms of TTX poisoning, and incidence worldwide.

Tetrodotoxin in live bivalve mollusks from Europe: Is it to be considered an emerging concern for food safety?

Tetrodotoxins (TTXs) are a group of potent neurotoxins named after the Tetraodontidae fish family (pufferfish). TTXs have been reported in several animal taxa, both terrestrial and marine. The ingestion of TTX-contaminated flesh can cause serious neurotoxic symptomatology and can eventually lead to death. Traditionally, TTXs have been associated with Asian countries, in particular with pufferfish consumption. However, they have also been reported in bivalve mollusks farmed in the Pacific area and, recently, in European seas. In Europe, different countries have reported TTXs, especially those bordering the Mediterranean Sea. As a consequence, in 2017 the European Food Safety Authority (EFSA) released an opinion with reference to TTX present in marine gastropods and bivalves, proposing a safety limit of 44 µg/kg TTXs in shellfish meat, below which no adverse effects should be observed in humans. Nevertheless, this limit has been exceeded on many occasions in European shellfish and, while for bivalves there have been no registered human intoxications, that is not the case for marine gastropods. However, TTXs have not yet been included in the list of marine biotoxins officially monitored in live bivalve mollusks within the European Union (EU). Thus, the aims of this manuscript are to discuss the increasing occurrence of TTXs in live bivalve mollusks from European sea waters, to acknowledge the still ongoing knowledge gaps that should be covered and to stimulate constructive debate on the eventuality of adopting a shared regulatory context, at least in the EU, for monitoring and managing this potential threat to food safety.

Elemental composition of pufferfish species from Northeastern Mediterranean Sea

This study aimed at comparing the elemental levels of muscle and liver tissues of four pufferfish (Lagocephalus sceleratus, Lagocephalus spadiceus, Lagocephalus suezensis, and Torquigener flavimaculosus), which are common in the Northeastern Mediterranean Sea (Mersin Bay), in terms of sex and seasonal variables. Na, Mg, P, K, and Ca levels in the muscle tissues of pufferfish range from 1848.4 to 16495.7, 824.4 to 2684.5, 6936.2 to 20486.6, 13019.3 to 36165.5, and 276.4 to 5566.5 μg g^-1, respectively. Na, Mg, P, K, and Ca levels in the liver tissues of pufferfish range from 531.8 to 6136.1, 63.8 to 899.1, 773.1 to 6677.5, 1151.4 to 10165.4, and 47.4 to 1607.7 μg g^-1, respectively. The levels of macroelements in the muscle and liver tissues can be represented as K > P ≥ Na > Ca ≥ Mg and K ≥ P ≥ Na > Ca ≥ Mg, respectively. Pufferfish muscle tissue has more abundant macroelement levels than liver tissue. Fe, Cu, and Zn levels in pufferfish muscle tissues range from 21.53 to 219.42, 0.73 to 6.54, and 25.38 to 100.47 μg g^-1, respectively. Fe, Cu, and Zn levels in pufferfish liver tissues range from 157.8 to 1368.6, 0.86 to 11.23, and 23.17 to 507.75 μg g^-1, respectively. Levels of trace elements in the muscle and liver tissues can be represented as Zn ≥ Fe > Cu and Fe ≥ Zn > Cu, respectively. The pufferfish liver tissue is richer than muscle tissue in terms of trace element levels. Cd, Pb, As, and Cr levels in pufferfish muscle tissues range from 0.66 to 6.30, 2.17 to 20.76, 41.90 to 258.37, and 0.34 to 3.70 μg g^-1, respectively. Cd, Pb, As, and Cr levels in the liver tissues of pufferfish range from 0.22 to 2.34, 0.17 to 2.27, 9.35 to 61.93, and 0.14 to 2.10 μg g^-1, respectively. Levels of metal in the muscle and liver tissues can be represented as As > Pb > Cd ≥ Cr and As > Cd ≥ Pb ≥ Cr, respectively. Pufferfish muscle tissue has a higher association with liver tissue due to metal level accumulation. All pufferfish are contaminated by Cd, Pb, As, Cr, Fe, and Zn metals.

Tetrodotoxin levels of three pufferfish species (Lagocephalus sp.) caught in the North-Eastern Mediterranean sea

Tetrodotoxin (TTX) levels in Lagocephalus sceleratus (Silverstripe blaasop), Lagocephalus spadiceus (Half-smooth golden pufferfish) and Lagocephalus suezensis (Suez puffer) caught in Mersin Bay in the Northeastern Mediterranean Sea were analysed using Q-TOF LC/MS. Pufferfish were caught using trawl fishing, longlining and fishing line from December 2015 to October 2016. The TTX changes in the gonads, livers, intestines, skins and muscle tissues were evaluated according to sex and season. TTX levels for L. sceleratus and L. suezensis for all tissues were in the range of 0.69-35.6 μg/g and 0.67-3.09 μg/g, respectively. The highest TTX levels were observed in the gonads of female L. sceleratus caught in the autumn, and in the skin of L. suezensis caught in the spring but no quantifiable levels of TTX were found for L. spadiceus. In conclusion, L. sceleratus and L. suezensis species caught in the North-Eastern Mediterranean are toxic, and their consumption is unsafe.

First report on TTX levels of the yellow spotted pufferfish (Torquigener flavimaculosus) in the Mediterranean Sea

The differences of tetrodotoxin (TTX) levels in various parts of pufferfish (Torquigener flavimaculosus) were examined in conjunction with the seasonal and sexual variations. The TTX levels in gonads, liver, intestines, skin and muscle tissue were determined using the Q-TOF LC/MS. Instrumental analysis revealed that all examined tissues from T. flavimaculosus contained high TTX concentrations. TTX levels in the gonads, liver, intestines, skin and muscle tissue of pufferfish were within the range of 5.03-100.71, 7.04-106.80, 12.59-86.30, 33.95-139.88 and 15.88-86.07 (μg/g), respectively. It was determined that in all seasons, except for summer, female individuals had higher TTX levels than males. Among all seasons, the highest level of TTX was found in winter and the lowest in autumn. Consequently, T. flavimaculosus is a highly toxic pufferfish that is dangerous for human consumption and should not be consumed under any circumstances.

Severe Tetrodotoxin Poisoning after Consumption of Lagocephalus sceleratus (Pufferfish, Fugu) Fished in Mediterranean Sea, Treated with Cholinesterase Inhibitor

Lagocephalus sceleratus, or better known as the pufferfish, or fugu, is widespread in Asia and Indo-Pacific regions. It is a poisonous fish containing tetrodotoxin (TTX) which is a potent neurotoxin. In the Far East, fugu is considered a delicate dish, especially in Japan where it is prepared by experts. Nevertheless, poisoning from Lagocephalus sceleratus is not a rare event. Recent data from Japan indicate an incidence of 45 patients per year and a mortality rate of 11%. Mediterranean sea is not the natural habitat of Lagocephalus sceleratus. However, by now multiple reports have established a firm presence of Lagocephalus sceleratus in Mediterranean region as well. This phenomenon is explained by migration of pufferfish across the Suez Channel (lessepsian migration) (Eisenman et al., 2008, Bentur et al., 2008). With lessepsian migration came the first reports of TTX poisoning in the Mediterranean region. We report a patient with a particularly severe and life-threatening TTX poisoning caused by consumption of Lagocephalus sceleratus and treated by cholinesterase inhibitor to a complete and uneventful recovery.

[Deep non-reactive reversible coma after a Mediterranean neurotoxic fish poisoning]

INTRODUCTION

Neurotoxic fish poisoning appears to be a recent phenomenon in the Mediterranean Sea. We report a case of deep non-reactive reversible coma after ingestion of Mediterranean fish innards.

CASE REPORT

An 80 year-old man, heavy smoker who had a previous cerebral infarct in the posterior territory, was admitted for rapid deterioration of his neurological condition. He started having perioral tingling, then dysarthria, then became quadriparetic, then developed respiratory and hemodynamic failure and within 3-4h, entered a state of deep non-reactive coma with absence of all brainstem reflexes. He started to improve after 20 h and recovered his neurological baseline within 36 h. Later on, he stated that all his symptoms started after he ingested the gonads of a toxic fish, Lagocephalus scleratus.

DISCUSSION

Tetrodotoxin blocks voltage-gated sodium channels and inhibits the production and propagation of action potentials. This toxin is highly concentrated in the liver, gonads, intestines and skin of this fish that is well-known in Japan (where it is considered as a delicacy) and South-East Asia and seems to have migrated recently to the Mediterranean Sea. There is no known antidote to tetrodotoxin but intensive supportive treatment can be life-saving.