Toxic marine puffer fish in Thailand seas and tetrodotoxin they contained

Assessment of Human Health Impacts from Invasive Pufferfish (Attacks, Poisonings and Fatalities) across the Eastern Mediterranean

The silver-cheeked toadfish Lagocephalus sceleratus (Gmelin 1789), and to a lesser degree the orange spotted toadfish Torquigener hypselogeneion (Bleeker, 1852), pose threats to human health from physical attacks and poisonings in the Eastern Mediterranean Sea. This study reviewed human health-related impacts resulting from these pufferfish, compiling and assessing records from online sources, the peer-reviewed literature, medical records, personal interviews, and observations across the Eastern Mediterranean in the years 2004 to 2023. A total of 198 events impacting human health were documented: 28 records of physical attacks, at least 144 non-lethal poisoning episodes, and 27 human fatalities resulting from consumption. The majority of the reported incidences occurred in Syria, Türkiye, and Lebanon. Most physical attacks occurred in summer, while most poisoning events occurred during winter. The number of recorded incidents greatly increased after 2019, especially with regard to poisonings, yet whether this is related to greater media attention, or to increased fish abundance is unclear. This is the first comprehensive study to collate findings on attacks, poisonings and fatalities caused by these pufferfish in the Mediterranean Sea, and may help in improving national health policies. We urge the continuation of national campaigns to caution residents and tourists of these species' high toxicities and potential aggressiveness.

Tetrodotoxin and Its Analogues (TTXs) in the Food-Capture and Defense Organs of the Palaeonemertean Cephalothrix cf. simula

Tetrodotoxin (TTX), an extremely potent low-molecular-weight neurotoxin, is widespread among marine animals including ribbon worms (Nemertea). Previously, studies on the highly toxic palaeonemertean Cephalothrix cf. simula showed that toxin-positive structures are present all over its body and are mainly associated with glandular cells and epithelial tissues. The highest TTXs concentrations were detected in a total extract from the intestine of the anterior part of the body and also in a total extract from the proboscis. However, many questions as to the TTXs distribution in the organs of the anterior part of the worm's body and the functions of the toxins in these organs are still unanswered. In the present report, we provide additional results of a detailed and comprehensive analysis of TTXs distribution in the nemertean's proboscis, buccal cavity, and cephalic gland using an integrated approach including high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), confocal laser scanning microscopy with anti-TTX antibodies, light and electron microscopies, and observations of feeding behavior. For the proboscis, we have found a TTXs profile different from that characteristic of other organs and tissues. We have also shown for the first time that the major amount of TTXs is localized in the anterior part of the proboscis that is mainly involved in hunting. TTX-containing glandular cells, which can be involved in the prey immobilization, have been found in the buccal cavities of the nemerteans. A significant contribution of the cephalic gland to the toxicity of this animal has been shown for the first time, and the role of the gland is hypothesized to be involved not only in protection against potential enemies but also in immobilizing prey. The data obtained have made it possible to extend the understanding of the role and features of the use of TTXs in the organs of the anterior part of nemertean's body.

Tetrodotoxins in Ribbon Worms Cephalothrix cf. simula and Kulikovia alborostrata from Peter the Great Bay, Sea of Japan

Tetrodotoxin, an extremely potent low-molecular-weight neurotoxin, and its analogues (TTXs) are widely distributed in aquatic and terrestrial ecosystems. Most investigations concerning TTXs have been conducted mainly on puffer fish, octopus, and mollusks, without paying due attention to various non-edible animals including nemerteans, a small group of marine worms, several species of which have been shown to possess high amounts of TTXs. In this study, for the first time, variations in TTX and its analogues, in 32 specimens of Cephalothrix cf. simula and 36 specimens of Kulikovia alborostrata, from Peter the Great Bay Sea of Japan were investigated, which may contribute to elucidation of TTXs migration pathways in ecosystems. Using high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), it was found that the total TTXs concentrations within both species vary by one to several orders of magnitude, 85.75-7108.26 µg/g and 0.35-8.11 ng/g in C. cf. simula and K. alborostrata, respectively. The intra- and interspecies similarities in proportions of TTXs in both species were observed; based on the results, a possible way of their toxification was discussed.

An Overview of the Anatomical Distribution of Tetrodotoxin in Animals

Tetrodotoxin (TTX), a potent paralytic sodium channel blocker, is an intriguing marine toxin. Widely distributed in nature, TTX has attracted attention in various scientific fields, from biomedical studies to environmental safety concerns. Despite a long history of studies, many issues concerning the biosynthesis, origin, and spread of TTX in animals and ecosystems remain. This review aims to summarize the current knowledge on TTX circulation inside TTX-bearing animal bodies. We focus on the advances in TTX detection at the cellular and subcellular levels, providing an expanded picture of intra-organismal TTX migration mechanisms. We believe that this review will help address the gaps in the understanding of the biological function of TTX and facilitate the development of further studies involving TTX-bearing animals.

Keeping Lagocephalus sceleratus off the Table: Sources of Variation in the Quantity of TTX, TTX Analogues, and Risk of Tetrodotoxication

The invasion of the tetrodotoxin (TTX)-bearing silver-cheeked toadfish and potential poisoning due to its consumption (tetrodotoxication) threatens public safety in the Mediterranean Sea. In this study, TTX and TTX analogues of Lagocephalus sceleratus (Gmelin, 1789) were measured using liquid chromatography tandem mass spectrometry (LC-MS/MS) in fish collected off the island of Crete (Southern Mediterranean). We tested the synergistic effect of a suite of factors potentially affecting toxins' levels and tetrodotoxication risk using general and generalized linear models, respectively. The type of tissue, geographic origin (Cretan Sea, Libyan Sea), sex, and fish maturity stage were significant predictors of toxin concentrations. Mean TTX was higher in gonads and lower in muscles, higher in the Libyan Sea and in female fish, and lower in juvenile (virgin) fish. The concentration of TTX was also significantly and positively correlated with the concentration of several TTX analogues (4-epiTTX, 4,9-anhydroTTX, 11-deoxyTTX, 5,11/6,11-dideoxyTTX, 5,6,11-trideoxyTTX, 11-norTTX-6-ol). The analysis showed that fish originating from the Libyan Sea had significantly higher probability to cause tetrodotoxication in case of consumption. The variability explained by the models developed in this study was relatively low, indicating that toxin levels are hard to predict and the consumption of L. sceleratus should therefore be avoided.

Hybrid Antibody-Aptamer Assay for Detection of Tetrodotoxin in Pufferfish

The marine toxin tetrodotoxin (TTX) poses a great risk to public health safety due to its severe paralytic effects after ingestion. Seafood poisoning caused by the consumption of contaminated marine species like pufferfish due to its expansion to nonendemic areas has increased the need for fast and reliable detection of the toxin to effectively implement prevention strategies. Liquid chromatography-mass spectrometry is considered the most accurate method, although competitive immunoassays have also been reported. In this work, we sought to develop an aptamer-based assay for the rapid, sensitive, and cost-effective detection of TTX in pufferfish. Using capture-SELEX combined with next-generation sequencing, aptamers were identified, and their binding properties were evaluated. Finally, a highly sensitive and user-friendly hybrid antibody–aptamer sandwich assay was developed with superior performance compared to several assays reported in the literature and commercial immunoassay kits. The assay was successfully applied to the quantification of TTX in pufferfish extracts, and the results obtained correlated very well with a competitive magnetic bead-based immunoassay performed in parallel for comparison. This is one of the very few works reported in the literature of such hybrid assays for small-molecule analytes whose compatibility with field samples is also demonstrated.

Tetrodotoxin/Saxitoxins Selectivity of the Euryhaline Freshwater Pufferfish Dichotomyctere fluviatilis

The present study evaluated differences in the tetrodotoxin (TTX)/saxitoxins (STXs) selectivity between marine and freshwater pufferfish by performing in vivo and in vitro experiments. In the in vivo experiment, artificially reared nontoxic euryhaline freshwater pufferfish Dichotomyctere fluviatilis were intrarectally administered a mixture of TTX (24 nmol/fish) and STX (20 nmol/fish). The amount of toxin in the intestine, liver, muscle, gonads, and skin was quantified at 24, 48, and 72 h. STX was detected in the intestine over a long period of time, with some (2.7-6.1% of the given dose) being absorbed into the body and temporarily located in the liver. Very little TTX was retained in the body. In the in vitro experiments, slices of intestine, liver, and skin tissue prepared from artificially reared nontoxic D. fluviatilis and the marine pufferfish Takifugu rubripes were incubated in buffer containing TTX and STXs (20 nmol/mL each) for up to 24 or 72 h, and the amount of toxin taken up in the tissue was quantified over time. In contrast to T. rubripes, the intestine, liver, and skin tissues of D. fluviatilis selectively took up only STXs. These findings indicate that the TTX/STXs selectivity differs between freshwater and marine pufferfish.

Natural Products in Polyclad Flatworms

Marine invertebrates are promising sources of novel bioactive secondary metabolites, and organisms like sponges, ascidians and nudibranchs are characterised by possessing potent defensive chemicals. Animals that possess chemical defences often advertise this fact with aposematic colouration that potential predators learn to avoid. One seemingly defenceless group that can present bright colouration patterns are flatworms of the order Polycladida. Although members of this group have typically been overlooked due to their solitary and benthic nature, recent studies have isolated the neurotoxin tetrodotoxin from these mesopredators. This review considers the potential of polyclads as potential sources of natural products and reviews what is known of the activity of the molecules found in these animals. Considering the ecology and diversity of polyclads, only a small number of species from both suborders of Polycladida, Acotylea and Cotylea have been investigated for natural products. As such, confirming assumptions as to which species are in any sense toxic or if the compounds they use are biosynthesised, accumulated from food or the product of symbiotic bacteria is difficult. However, further research into the group is suggested as these animals often display aposematic colouration and are known to prey on invertebrates rich in bioactive secondary metabolites.

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.

The Incidence of Marine Toxins and the Associated Seafood Poisoning Episodes in the African Countries of the Indian Ocean and the Red Sea

The occurrence of Harmful Algal Blooms (HABs) and bacteria can be one of the great threats to public health due to their ability to produce marine toxins (MTs). The most reported MTs include paralytic shellfish toxins (PSTs), amnesic shellfish toxins (ASTs), diarrheic shellfish toxins (DSTs), cyclic imines (CIs), ciguatoxins (CTXs), azaspiracids (AZTs), palytoxin (PlTXs), tetrodotoxins (TTXs) and their analogs, some of them leading to fatal outcomes. MTs have been reported in several marine organisms causing human poisoning incidents since these organisms constitute the food basis of coastal human populations. In African countries of the Indian Ocean and the Red Sea, to date, only South Africa has a specific monitoring program for MTs and some other countries count only with respect to centers of seafood poisoning control. Therefore, the aim of this review is to evaluate the occurrence of MTs and associated poisoning episodes as a contribution to public health and monitoring programs as an MT risk assessment tool for this geographic region.

The Incidence of Tetrodotoxin and Its Analogs in the Indian Ocean and the Red Sea

Tetrodotoxin (TTX) is a potent marine neurotoxin with bacterial origin. To date, around 28 analogs of TTX are known, but only 12 were detected in marine organisms, namely TTX, 11-oxoTTX, 11-deoxyTTX, 11-norTTX-6(R)-ol, 11-norTTX-6(S)-ol, 4-epiTTX, 4,9-anhydroTTX, 5,6,11-trideoxyTTX, 4-CysTTX, 5-deoxyTTX, 5,11-dideoxyTTX, and 6,11-dideoxyTTX. TTX and its derivatives are involved in many cases of seafood poisoning in many parts of the world due to their occurrence in different marine species of human consumption such as fish, gastropods, and bivalves. Currently, this neurotoxin group is not monitored in many parts of the world including in the Indian Ocean area, even with reported outbreaks of seafood poisoning involving puffer fish, which is one of the principal TTX vectors know since Egyptian times. Thus, the main objective of this review was to assess the incidence of TTXs in seafood and associated seafood poisonings in the Indian Ocean and the Red Sea. Most reported data in this geographical area are associated with seafood poisoning caused by different species of puffer fish through the recognition of TTX poisoning symptoms and not by TTX detection techniques. This scenario shows the need of data regarding TTX prevalence, geographical distribution, and its vectors in this area to better assess human health risk and build effective monitoring programs to protect the health of consumers in Indian Ocean area.

A Study of 11-[³H]-Tetrodotoxin Absorption, Distribution, Metabolism and Excretion (ADME) in Adult Sprague-Dawley Rats

Tetrodotoxin (TTX) is a powerful sodium channel blocker that in low doses can safely relieve severe pain. Studying the absorption, distribution, metabolism and excretion (ADME) of TTX is challenging given the extremely low lethal dose. We conducted radiolabeled ADME studies in Sprague-Dawley rats. After a single dose of 6 μg/(16 μCi/kg) 11-[³H]TTX, pharmacokinetics of plasma total radioactivity were similar in male and female rats. Maximum radioactivity (5.56 ng Eq./mL) was reached in 10 min. [³H]TTX was below detection in plasma after 24 h. The area under the curve from 0 to 8 h was 5.89 h·ng Eq./mL; mean residence time was 1.62 h and t½ was 2.31 h. Bile secretion accounted for 0.43% and approximately 51% of the dose was recovered in the urine, the predominant route of elimination. Approximately 69% was recovered, suggesting that hydrogen tritium exchange in rats produced tritiated water excreted in breath and saliva. Average total radioactivity in the stomach, lungs, kidney and intestines was higher than plasma concentrations. Metabolite analysis of plasma, urine and feces samples demonstrated oxidized TTX, the only identified metabolite. In conclusion, TTX was rapidly absorbed and excreted in rats, a standard preclinical model used to guide the design of clinical trials.

LC-MS/MS method for the determination of tetrodotoxin (TTX) on a triple quadruple mass spectrometer

Tetrodotoxin (TTX), often referred to as the 'puffer fish' poison, is a marine toxin and it has been identified as the agent responsible for many food poisoning incidents around the world. It is a neurotoxin that blocks voltage-gated sodium channels, resulting in respiratory paralysis and even death in severe cases. It is known to occur in many different species of fish and other organisms. The toxin is mainly found in the Southeast Asia region. Worryingly, TTX is starting to appear in European waters. It is suspected that this is a consequence of Lessepsian migration, also known as the Erythrean invasion. Therefore, straightforward and reliable extraction and analytical methods are now urgently required to monitor seafood of European origin for TTX. This paper provides a versatile, dependable and robust method for the analysis of TTX in puffer fish and trumpet shellfish using LC-MS/MS. A three-stage approach was implemented involving: (1) the screening of samples using fast multiple reaction monitoring (MRM) mass spectral analysis to identify quickly positive samples on a triple quadrupole mass spectrometer (QqQMS/MS), the API 3000; (2) a Fourier-transform (FT)-MS full-scan analysis of positive samples to collect qualitative data; and (3) a method with a longer chromatography run to identify and quantitate the positive samples using the QqQMS. The quantitative LC-QqQMS method delivered excellent linearity for solvent-based standards (0.01-7.5 µg ml^-1; R² ≥ 0.9968) as well as for matrix-matched standards (0.05-37.50 µg g^-1; R² ≥ 0.9869). Good inter-day repeatability was achieved for all the relevant analytes with %RSD values (n = 9) ranging from 1.11% to 4.97% over a concentration range of 0.01-7.5 µg ml^-1. A sample clean-up procedure for the puffer fish and trumpet shellfish was developed to ensure acceptable and reproducible recoveries to enable accurate and precise determination of TTX in a myriad of tissues types. Blank mackerel matrix was used for the TTX standard spiking studies in order to calculate the recoveries of the toxin during the extraction procedure. The recovery was 61.17% ± 5.42% for the extraction protocol. MS/MS studies were performed on a linear-trap quadruple-Orbitrap mass spectrometer (LTQ-Orbitrap) to obtain high-mass-accuracy data of the target analytes and their characteristic fragment ions in the puffer fish and trumpet shellfish samples. This facilitated identification of TTX and its associated analogues. These high-mass-accuracy studies facilitated the development of a rapid MRM-based quantitative method for TTX determination on the LC-QqQMS.

A PUFFERFISH (TETRADON NIGROVIRIDIS) AVAILABLE IN THE COMMON PET TRADE HARBORS LETHAL CONCENTRATIONS OF TETRODOTOXIN: A CASE STUDY OF POISONING IN A CUVIER'S DWARF CAIMAN (PALEOSUCHUS PALPEBROSUS)

Many pufferfish possess tetrodotoxin (TTX). Unaware of this fact, the owner of a 3-mo-old pet Cuvier's dwarf caiman ( Paleosuchus palpebrosus ) fed the caiman a green spotted pufferfish ( Tetraodon nigroviridis ), acquired from a local discount department store. The caiman was nonresponsive within an hour of consumption of the fish. The caiman was presented for veterinary evaluation but died despite intensive medical care. High-performance liquid chromatography and a competitive inhibition enzyme immunoassay were used to determine whether the pufferfish was tetrodotoxic and whether the deceased caiman had TTX in its system. Skin and liver of the pufferfish harbored high concentrations of TTX, and the caiman had TTX in the blood, liver, and kidney. The clinical signs and presence of TTX in the caiman suggest that the caiman succumbed to tetrodotoxicosis. The implication is that lethally poisonous species are available commercially and pose a danger to other pets and possibly small children.

Potential Threats Posed by Tetrodotoxins in UK Waters: Examination of Detection Methodology Used in Their Control

Tetrodotoxin is a neurotoxin responsible for many human fatalities, most commonly following the consumption of pufferfish. Whilst the source of the toxin has not been conclusively proven, it is thought to be associated with various species of marine bacteria. Whilst the toxins are well studied in fish and gastropods, in recent years, there have been a number of reports of tetrodotoxin occurring in bivalve shellfish, including those harvested from the UK and other parts of Europe. This paper reviews evidence concerning the prevalence of tetrodotoxins in the UK together with methodologies currently available for testing. Biological, biomolecular and chemical methods are reviewed, including recommendations for further work. With the recent development of quantitative chromatographic methods for these and other hydrophilic toxins, as well as the commercial availability of rapid testing kits, there are a number of options available to ensure consumers are protected against this threat.

Tetrodotoxin, an Extremely Potent Marine Neurotoxin: Distribution, Toxicity, Origin and Therapeutical Uses

Tetrodotoxin (TTX) is a potent neurotoxin responsible for many human intoxications and fatalities each year. The origin of TTX is unknown, but in the pufferfish, it seems to be produced by endosymbiotic bacteria that often seem to be passed down the food chain. The ingestion of contaminated pufferfish, considered the most delicious fish in Japan, is the usual route of toxicity. This neurotoxin, reported as a threat to human health in Asian countries, has spread to the Pacific and Mediterranean, due to the increase of temperature waters worldwide. TTX, for which there is no known antidote, inhibits sodium channel producing heart failure in many cases and consequently death. In Japan, a regulatory limit of 2 mg eq TTX/kg was established, although the restaurant preparation of “fugu” is strictly controlled by law and only chefs qualified are allowed to prepare the fish. Due to its paralysis effect, this neurotoxin could be used in the medical field as an analgesic to treat some cancer pains.

Tetrodotoxin: chemistry, toxicity, source, distribution and detection

Tetrodotoxin (TTX) is a naturally occurring toxin that has been responsible for human intoxications and fatalities. Its usual route of toxicity is via the ingestion of contaminated puffer fish which are a culinary delicacy, especially in Japan. TTX was believed to be confined to regions of South East Asia, but recent studies have demonstrated that the toxin has spread to regions in the Pacific and the Mediterranean. There is no known antidote to TTX which is a powerful sodium channel inhibitor. This review aims to collect pertinent information available to date on TTX and its analogues with a special emphasis on the structure, aetiology, distribution, effects and the analytical methods employed for its detection.