In vitro cultivation of anisakis simplex: pepsin increases survival and moulting from fourth larval to adult stage

Rapid and Conventional Freezing Conditions of Fish for the Prevention of Human Anisakiasis

In recent years, rapid freezers have been used to freeze and preserve seafood, with advances in freezing technology. However, limited studies have examined the effect of rapid freezing on the viability of Anisakis larvae in fish muscle. In this study, freezing experiments were conducted on Anisakis larvae alone (bare group) and on larvae embedded in mackerel fish (embedded group) using an air-blast freezer (rapid freezing) as the most popular rapid-freezing method, passing through the zone of maximum ice crystal formation within 30 min, and a natural convection freezer (conventional freezing) set at -20 °C. In the bare group experiments, all larvae died after 8 min of rapid freezing and after more than 2 h of conventional freezing. In the rapid-freezing experiments on the embedded group, only a few larvae were alive when the core temperature of the fish reached -20 °C, whereas all larvae died when the core temperature reached -35 °C. With conventional freezing, only a few larvae were alive for 24 h after freezing at -20 °C. In contrast, all larvae died after freezing at -20 °C for 24 h after the fish core temperature reached -20 °C under both rapid and conventional freezing conditions. In the embedded group, the standard deviation of the time taken for the fish core temperature to reach -20 °C was <15 min for rapid freezing and 171 min for conventional freezing. The results showed that the time taken for the core temperature to reach -20 °C varies by several hours in conventional freezing, depending on the fish size. Thus, the most crucial freezing conditions to avoid anisakiasis are either rapidly freezing the fish to a core temperature of -35 °C or keeping the fish core temperature at -20 °C for at least 24 h.

Exploring the exoproteome of the parasitic nematode Anisakis simplex (s. s.) and its impact on the human host - an in vitro cross-talk proteomic approach

Introduction

Anisakis simplex sensu stricto (s. s.) is one of the most widespread parasitic nematodes of marine organisms, with humans as accidental hosts. While many studies have explored nematode biology and host interactions, the role of extracellular vesicles (EVs) as signaling molecules in parasitic nematodes is less understood.

Materials and methods

Therefore, the proteins present in the EVs of A. simplex (s. s.) (Anis-EVs) were identified. In addition, a cross-talk proteomic approach was used to identify differentially regulated proteins (DRPs) in the proteome of the human intestinal epithelial cell line (Caco-2) co-cultured with L3 larvae of A. simplex (s. s.) or directly exposed to two concentrations (low or high) of Anis-EVs. In addition, DRPs were identified in the proteome of A. simplex (s. s.) larvae affected by co-culture with Caco-2. To achieve this goal, the shotgun proteomics method based on isobaric mass labeling (via tandem mass tags; TMT) was used with a combination of nano high-performance liquid chromatography (nLC) coupled with an LTQ-Orbitrap Elite mass spectrometer. In addition, ELISA assays were used to demonstrate if Caco-2 respond to A. simplex (s. s.) larvae and Anis-EVs with significant changes in selected cytokines secretion.

Results

The results of this study indicate the anti-inflammatory character of Anis-EVs in relation to Caco-2. At the same time, direct treatment with Anis-EVs resulted in more significant changes in the Caco-2 proteome than co-culture with L3 larvae.

Discussion

The results obtained should lead to a better understanding of the molecular mechanisms underlying the development of A. simplex (s. s.) infection in humans and will complement the existing knowledge on the role of EVs in host-parasite communication.

The response of Anisakis simplex (s. s.) to anthelmintics - Specific changes in xenobiotic metabolic processes

Anisakiasis is a parasitic disease transmitted through the consumption of raw or undercooked fish and cephalopods that are infected with larvae of Anisakis simplex (sensu stricto) or Anisakis pegreffii. The purpose of this study was to investigate how A. simplex (s. s.) responds to the influence of anthelmintics such as ivermectin (IVM) and pyrantel (PYR). In vitro experiments were conducted using larvae at two developmental stages of A. simplex (s. s.) (L3 and L4) obtained from Baltic herring (Clupea harengus membras). Larvae were cultured with different concentrations of IVM or PYR (1.56, 3.125, and 6.25 μg/mL) for various durations (3, 6, 9, and 12 h) under anaerobic conditions (37 °C, 5% CO2). The gene expression of actin, ABC transporter, antioxidant enzymes, γ-aminobutyric acid receptors, and nicotinic acetylcholine receptors, as well as the oxidative status were analyzed. The results showed that A. simplex (s. s.) L3 stage had lower mobility when cultured with PYR compared to IVM. The analysis of relative gene expression revealed significant differences in the mRNA level of ABC transporters after treatment with IVM and PYR, compared to the control group. Similar patterns were observed in the gene expression of antioxidant enzymes in response to both drugs. Furthermore, the total antioxidant capacity (TAC) and glutathione S-transferase (GST) activity were higher in the treatment groups than in the control group. These findings suggest a relationship between the expression of the studied genes, including those related to oxidative metabolism, and the effectiveness of the tested drugs.

Fecundity, in vitro early larval development and karyotype of the zoonotic nematode Anisakis pegreffii

The in vitro life cycle of zoonotic helminths is an essential tool for -omic translational studies focused on disease control and treatment. Anisakiosis is an emerging zoonosis contracted by the ingestion of raw or undercooked fish infected with the third stage larvae (L3) of two sibling species Anisakis simplex sensu stricto (s.s.) and Anisakis pegreffii, the latter being the predominant species in the Mediterranean basin. Recently, in vitro culture of A. pegreffii has been developed to enable fast and large-scale production of fertile adults. However, the conditions for larval development from hatching to infective L3 were not fulfilled to complete the cycle. Herein, we used a Drosophila medium supplemented with chicken serum and adjusted different osmolarities to maintain the culture of L3 hatched from eggs for up to 17 weeks. The highest survival rate was observed in the medium with the highest osmolarities, which also allowed the highest larval exsheathment rate. Key morphological features of embryogenesis and postembryogenesis studied by transmission electron microscopy revealed that the excretory gland cell is differentiated already up to 48 h post-hatching. Extracellular vesicles and cell-free mitochondria are discharged between the two cuticle sheets of the second stage larvae (L2). Contemporarly cultivated, two populations of adult A. simplex s.s. and A. pegreffii reached an average production of 29,914.05 (± 27,629.36) and 24,370.96 (± 12,564.86) eggs/day/female, respectively. The chromosome spreads of A. pegreffii obtained from mature gonads suggests a diploid karyotype formula of 2n = 18. The development of a reliable protocol for the in vitro culture of a polyxenous nematode such as Anisakis spp. will serve to screen for much needed novel drug targets, but also to study the intricated and unknown ecological and physiological traits of these trophically transmitted marine nematodes.

Metabolomic analysis reveals a differential adaptation process of the larval stages of Anisakis simplex to the host environment

Introduction: Anisakis simplex are parasitic nematodes that cause anisakiasis. The possibility of infection with this parasite is through consumption of raw or undercooked fish products. A. simplex infections are often misdiagnosed, especially in subclinical cases that do not present with typical symptoms such as urticaria, angioedema, and gastrointestinal allergy. The resulting allergic reactions range from rapid-onset and potentially fatal anaphylactic reactions to chronic, debilitating conditions. While there have been numerous published studies on the genomes and proteomes of A. simplex, less attention has been paid to the metabolomes. Metabolomics is concerned with the composition of metabolites in biological systems. Dynamic responses to endogenous and exogenous stimuli are particularly well suited for the study of holistic metabolic responses. In addition, metabolomics can be used to determine metabolic activity at different stages of development or during growth. Materials and methods: In this study, we reveal for the first time the metabolomes of infectious stages (L3 and L4) of A. simplex using untargeted metabolomics by ultra-performance liquid chromatography-mass spectrometry. Results: In the negative ionization mode (ESI-), we identified 172 different compounds, whereas in the positive ionization mode (ESI+), 186 metabolites were found. Statistical analysis showed that 60 metabolites were found in the ESI- mode with different concentration in each group, of which 21 were more enriched in the L3 larvae and 39 in the L4 stage of A. simplex. Comparison of the individual developmental stages in the ESI + mode also revealed a total of 60 differential metabolites, but 32 metabolites were more enriched in the L3 stage larvae, and 28 metabolites were more concentrated in the L4 stage. Discussion: The metabolomics study revealed that the developmental stages of A. simplex differed in a number of metabolic pathways, including nicotinate and nicotinamide metabolism. In addition, molecules responsible for successful migration within their host, such as pyridoxine and prostaglandins (E1, E2, F1a) were present in the L4 stage. In contrast, metabolic pathways for amino acids, starch, and sucrose were mainly activated in the L3 stage. Our results provide new insights into the comparative metabolome profiles of two different developmental stages of A. simplex.

Proteomic characterization of extracellular vesicles released by third stage larvae of the zoonotic parasite Anisakis pegreffii (Nematoda: Anisakidae)

Introduction

Anisakis pegreffii is a sibling species within the A. simplex (s.l.) complex requiring marine homeothermic (mainly cetaceans) and heterothermic (crustaceans, fish, and cephalopods) organisms to complete its life cycle. It is also a zoonotic species, able to accidentally infect humans (anisakiasis). To investigate the molecular signals involved in this host-parasite interaction and pathogenesis, the proteomic composition of the extracellular vesicles (EVs) released by the third-stage larvae (L3) of A. pegreffii, was characterized.

Methods

Genetically identified L3 of A. pegreffii were maintained for 24 h at 37°C and EVs were isolated by serial centrifugation and ultracentrifugation of culture media. Proteomic analysis was performed by Shotgun Analysis.

Results and discussion

EVs showed spherical shaped structure (size 65-295 nm). Proteomic results were blasted against the A. pegreffii specific transcriptomic database, and 153 unique proteins were identified. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis predicted several proteins belonging to distinct metabolic pathways. The similarity search employing selected parasitic nematodes database revealed that proteins associated with A. pegreffii EVs might be involved in parasite survival and adaptation, as well as in pathogenic processes. Further, a possible link between the A. pegreffii EVs proteins versus those of human and cetaceans’ hosts, were predicted by using HPIDB database. The results, herein described, expand knowledge concerning the proteins possibly implied in the host-parasite interactions between this parasite and its natural and accidental hosts.

In vitro culture of the zoonotic nematode Anisakis pegreffii (Nematoda, Anisakidae)

BACKGROUND

Anisakiasis is a foodborne disease caused by the third-stage larvae (L3) of two species belonging to the genus Anisakis: Anisakis pegreffii and Anisakis simplex sensu stricto. Both species have been the subject of different -omics studies undertaken in the past decade, but a reliable in vitro culture protocol that would enable a more versatile approach to functional studies has never been devised. In nature, A. pegreffii shows a polyxenous life-cycle. It reproduces in toothed whales (final host) and disseminates embryonated eggs via cetacean faeces in the water column. In the environment, a first- (L1) and second-stage larva (L2) develops inside the egg, and subsequently hatched L2 is ingested by a planktonic crustacean or small fish (intermediate host). In the crustacean pseudocoelom, the larva moults to the third stage (L3) and grows until the host is eaten by a fish or cephalopod (paratenic host). Infective L3 migrates into the visceral cavity of its paratenic host and remains in the state of paratenesis until a final host preys on the former. Once in the final host's gastric chambers, L3 attaches to mucosa, moults in the fourth stage (L4) and closes its life-cycle by becoming reproductively mature.

METHODS

Testing two commercially available media (RPMI 1640, Schneider's Drosophila) in combination with each of the six different heat-inactivated sera, namely foetal bovine, rabbit, chicken, donkey, porcine and human serum, we have obtained the first reliable, fast and simple in vitro cultivation protocol for A. pegreffii.

RESULTS

Schneider's Drosophila insect media supplemented with 10% chicken serum allowed high reproducibility and survival of adult A. pegreffii. The maturity was reached already at the beginning of the third week in culture. From collected eggs, hatched L2 were maintained in culture for 2 weeks. The protocol also enabled the description of undocumented morphological and ultrastructural features of the parasite developmental stages.

CONCLUSIONS

Closing of the A. pegreffii life-cycle from L3 to reproducing adults is an important step from many research perspectives (e.g., vaccine and drug-target research, transgenesis, pathogenesis), but further effort is necessary to optimise the efficient moulting of L2 to infective L3.

Distribution and genetic diversity of Anisakis spp. in cetaceans from the Northeast Atlantic Ocean and the Mediterranean Sea

Parasite biodiversity in cetaceans represents a neglected component of the marine ecosystem. This study aimed to investigate the distribution and genetic diversity of anisakid nematodes of the genus Anisakis sampled in cetaceans from the Northeast Atlantic Ocean and the Mediterranean Sea. A total of 478 adults and pre-adults of Anisakis spp. was identified by a multilocus genetic approach (mtDNA cox2, EF1 α − 1 nDNA and nas 10 nDNA gene loci) from 11 cetacean species. A clear pattern of host preference was observed for Anisakis spp. at cetacean family level: A. simplex (s.s.) and A. pegreffii infected mainly delphinids; A. physeteris and A. brevispiculata were present only in physeterids, and A. ziphidarum occurred in ziphiids. The role of cetacean host populations from different waters in shaping the population genetic structure of A. simplex (s.s.), A. pegreffii and A. physeteris was investigated for the first time. Significant genetic sub-structuring was found in A. simplex (s.s.) populations of the Norwegian Sea and the North Sea compared to those of the Iberian Atlantic, as well as in A. pegreffii populations of the Adriatic and the Tyrrhenian Seas compared to those of the Iberian Atlantic waters. Substantial genetic homogeneity was detected in the Mediterranean Sea population of A. physeteris. This study highlights a strong preference by some Anisakis spp. for certain cetacean species or families. Information about anisakid biodiversity in their cetacean definitive hosts, which are apex predators of marine ecosystems, acquires particular importance for conservation measures in the context of global climate change phenomena.

Nematode surface functionalization with hydrogel sheaths tailored in situ

Engineering the surfaces of biological organisms allows the introduction of novel functions and enhances their native functions. However, studies on surface engineering remained limited to unicellular organisms. Herein, nematode surfaces are engineered through in situ hydrogelation mediated by horseradish peroxidase (HRP) anchored to nematode cuticles. With this method, hydrogel sheaths of approximately 10-μm thickness are fabricated from a variety of polysaccharides, proteins, and synthetic polymers. Caenorhabditis elegans and Anisakis simplex coated with a hydrogel sheath showed a negligible decrease in viability, chemotaxis and locomotion. Hydrogel sheaths containing UV-absorbable groups and catalase functioned as shields to protect nematodes from UV and hydrogen peroxide, respectively. The results also showed that hydrogel sheaths containing glucose oxidase have the potential to be used as living drug delivery systems for cancer therapy. The nematode functionalization method developed in this study has the potential to impact a wide range of fields from agriculture to medicine.

Drug efficacy on zoonotic nematodes of the Anisakidae family - new metabolic data

In the Anisakidae family, there are nematodes, most of which are parasitic for important commercial fish species. Both public health risks and socio-economic problems are attributed to these parasites. Despite these concerns, knowledge of the metabolism of these parasites remains unknown. Therefore, the main objective of this study was to investigate the receptors of drugs and oxidative metabolic status of two Anisakidae species, Pseudoterranova decipiens (s. s.) and Contracaecum osculatum (s. s.), under the influence of anthelminthic drugs, ivermectin (IVM) and pyrantel (PYR), at different concentrations: 1.56, 3.125 and 6.25 μg mL⁻¹ of culture medium for 3, 6, 9, 12 and 72 h. The mRNA expressions of the γ-aminobutyric acid receptor, acetylcholine receptor subunits, adenosine triphosphate-binding cassette transporters and antioxidative enzymes were determined. The total antioxidant capacity and glutathione S-transferase activity were also examined. To the best of the authors' knowledge, this is the first time that IVM and PYR have been tested against these parasitic nematodes.

A Complex Proteomic Response of the Parasitic Nematode Anisakis simplex s.s. to Escherichia coliLipopolysaccharide

Helminths are masters at manipulating host's immune response. Especially, parasitic nematodes have evolved strategies that allow them to evade, suppress, or modulate host's immune response to persist and spread in the host's organism. While the immunomodulatory effects of nematodes on their hosts are studied with a great commitment, very little is known about nematodes' own immune system, immune response to their pathogens, and interactions between parasites and bacteria in the host's organism. To illustrate the response of the parasitic nematode Anisakis simplex s.s. during simulated interaction with Escherichia coli, different concentrations of lipopolysaccharide (LPS) were used, and the proteomic analysis with isobaric mass tags for relative and absolute quantification (tandem mass tag-based LC-MS/MS) was performed. In addition, gene expression and biochemical analyses of selected markers of oxidative stress were determined. The results revealed 1148 proteins in a group of which 115 were identified as differentially regulated proteins, for example, peroxiredoxin, thioredoxin, and macrophage migration inhibitory factor. Gene Ontology annotation and Reactome pathway analysis indicated that metabolic pathways related to catalytic activity, oxidation-reduction processes, antioxidant activity, response to stress, and innate immune system were the most common, in which differentially regulated proteins were involved. Further biochemical analyses let us confirm that the LPS induced the oxidative stress response, which plays a key role in the innate immunity of parasitic nematodes. Our findings, to our knowledge, indicate for the first time, the complexity of the interaction of parasitic nematode, A. simplex s.s. with bacterial LPS, which mimics the coexistence of helminth and gut bacteria in the host. The simulation of this crosstalk led us to conclude that the obtained results could be hugely valuable in the integrated systems biology approach to describe a relationship between parasite, host, and its commensal bacteria.

Hybrid Genotype of Anisakis simplex (s.s.) and A. pegreffii Identified in Third- and Fourth-Stage Larvae from Sympatric and Allopatric Spanish Marine Waters

Simple Summary

The nematode species Anisakis simplex sensu stricto (s.s.) and Anisakis pegreffii are wormlike parasites found in commonly consumed fish and are the main cause of human anisakiasis. Outwardly, the two nematodes are extremely similar and difficult to distinguish, especially in their larval forms. Genetic analysis has discovered the existence of a hybrid between these two “sibling species”, but its identification is a controversial matter, as results differ according to the specific region of the DNA analysed. The aim of our work was to confirm the presence of this hybrid genotype in fish off the Spanish coast and to obtain fourth-stage larvae in the laboratory to study if different genotypes are associated with different growth behaviour. Our results confirm that hybrid genotypes can be overestimated if identification is based on a particular molecular marker. We also obtained fourth-stage larvae with a hybrid genotype, which has not been reported previously. These findings are valuable for the taxonomic classification of Anisakis species, and for further epidemiological and biomedical research.

Abstract

The sibling species Anisakis simplex (s.s.) and Anisakis pegreffii are parasites of marine mammals and fish worldwide and the main causative agents of human anisakiasis. In sympatric areas, a hybrid genotype between the two species has been identified, mainly in third-stage larvae, but rarely in fourth-stage and adult forms. The aim of this study was to confirm the presence of hybrid genotypes in larvae parasitizing fish caught in sympatric and allopatric Spanish marine waters, the North-East Atlantic and West Mediterranean, respectively, and to study possible differences in the growth behaviour between genotypes. Of the 254 molecularly analysed larvae, 18 were identified as hybrids by PCR-RFLP analysis of the rDNA ITS region, 11 of which were subsequently confirmed by EF1 α-1 nDNA gene sequencing. These results therefore indicate an overestimation of hybrid genotypes when identification is based only on the ITS region. We also report the detection of a hybrid specimen in a host from the West Mediterranean, considered an allopatric zone. Additionally, fourth-stage larvae with a hybrid genotype were obtained in vitro for the first time, and no differences were observed in their growth behaviour compared to larvae with A. simplex (s.s.) and A. pegreffii genotypes.

Acute Anisakiasis: Pharmacological Evaluation of Various Drugs in an Animal Model

BACKGROUND

The accidental ingestion of the third larval stage of Anisakis can cause acute clinical symptoms, which are relieved via extraction of the larvae. Although this is a highly effective technique, it can only be practiced when the larvae are found in accessible areas of the gastrointestinal tract, and therefore instead the condition has often been treated using various different drugs.

AIMS

This study evaluates the effectiveness of gastric acid secretion inhibitors (omeprazole and ranitidine), gastric mucosal protectants (sucralfate) and anthelmintics (mebendazole and flubendazole) in treating anisakiasis in Wistar rats.

METHODS

Rats were infected with Anisakis-type I larvae and administered the drugs via a gastric probe. Data were recorded regarding the number of live and dead larvae, their location both within the animal and in its feces, and the presence of gastrointestinal lesions. Additionally, gastric pH was measured and histology performed.

RESULTS

While rats in all experimental groups exhibited lesions; those treated with ranitidine and mebendazole showed significantly fewer lesions (50% and 35% of rats exhibited lesions, respectively). Histological examination of the gastric lesions revealed infection-induced changes, but no significant differences were observed between the treated and untreated rats.

CONCLUSIONS

Mebendazole was found to be most efficacious in preventing gastrointestinal lesions, followed by ranitidine, which was the most effective antacid of those studied. Both these drugs could thus be considered as part of the conservative management of anisakiasis.

Correlation of NHR-48 Transcriptional Modulator Expression with Selected CYP Genes’ Expression during Thiabendazole Treatment of Anisakis simplex (s.l.)?—An In Vitro Study

Anisakis simplex (s.l.) is a complex of three sibling (biological) species of parasitic nematodes of marine mammals, including A. berlandi, A. pegreffii and A. simplex (s.s.). It is characterized by a complex life cycle in which humans can become accidental hosts by consuming dishes made of raw or undercooked fish containing L3 larvae, which in many regions of the world is related to the national or regional culinary tradition. This has spurred scientific efforts to develop new methods for treating the disease, called anisakiasis, and to neutralize invasive L3. Thiabendazole (TBZ) is a wide-spectrum anthelminthic with a higher efficacy than albendazole, a drug whose long-term use induces resistance in many parasitic species. Cytochromes P450 participate in TBZ metabolism, and the expression of their genes is controlled by nuclear hormone receptors (NHR). This study aimed to examine the effects of TBZ on the above-described pathway in invasive larvae of A. simplex (s.l.). The efficacy of TBZ against A. simplex (s.l.) larvae was observed for the first time. Larvae were cultured in vitro for 72 h in a medium containing TBZ at five concentrations from 0.5 to 1.5 mM. However, the survival curves did not significantly differ from each other. This means that all of the concentrations of TBZ had a similar effect on the A. simplex (s.l.) L3 larvae during in vitro culture. Nevertheless, TBZ modified the expression of nhr-48, cyp13a3 and cyp1a1 genes in the L3 of A. simplex (s.l.).

The Selection of Reliable Reference Genes for RT-qPCR Analysis of Anisakis simplex Sensu Stricto Gene Expression from Different Developmental Stages

BACKGROUND

Anisakis simplex s. s. is a parasitic nematode with a complex life cycle in which humans can become accidental hosts by consuming raw or not fully cooked fish containing L3 larvae. The growing popularity of raw fish dishes has contributed to an increase in the incidence of anisakiasis, which has spurred scientific efforts to develop new methods for diagnosing and treating the disease and also to investigate the gene expression at different developmental stages of this parasite. The identification of reference genes suitable for the normalization of RT-qPCR data has not been studied with respect to A. simplex s. s.

METHODS

In the present study, eight candidate reference genes were analyzed in A. simplex s. s. at two different developmental stages: L3 and L4. The expression stability of these genes was assessed by geNorm and NormFinder softwares.

RESULTS

In general, our results identified translation elongation factor 1α (ef-1α) and peptidyl-prolyl isomerase 12 (ppi12) as the most stable genes in L3 and L4 developmental stages of A. simplex s. s. Validation of the selected reference genes was performed by profiling the expression of the nuclear hormone receptor gene (nhr 48) in different developmental stages.

CONCLUSIONS

This first analysis selecting suitable reference genes for RT-qPCR in A. simplex s. s. will facilitate future functional analyses and deep mining of genetic resources in this parasitic nematode.

Anisakiasis and Anisakis: An underdiagnosed emerging disease and its main etiological agents

Anisakiasis or anisakiosis is a human parasitic infection caused by the third-stage larvae (L3) of nematodes of the genus Anisakis, although the term is also used in medical literature for the much less frequent (<3% of cases) infection by L3 of other genera of anisakids, particularly Pseudoterranova. These parasites have a marine lifecycle. Humans are infected by the L3 through ingesting of fish and squid, the intermediate/paratenic hosts. The live larvae generally penetrate the wall of the stomach or intestine causing, among other symptoms, intense pain or allergic symptoms. These are emerging, cosmopolite illnesses. Diagnosis and treatment is usually by endoscopy and extraction and identification of the larvae. Allergic forms are usually diagnosed by prick-test and/or allergen-specific IgE detection and treated with a suitable anti-allergy treatment. The patient is also warned against further consumption of marine fish or squid, as these may be infected with Anisakis. The most common method of prevention is thermal treatment of the entire fish or squid prior to consumption (>60 °C, >1 min or - 20 °C, >24 h). Useful measures for the control of anisakiasis would be to establish a national register of cases, to initiate educational campaigns for the general public and consciousness-raising and training campaigns for health professionals. These would be complemented by control measures for the relevant sectors of the economy: fish operators, fish farming, fishermen, fishmongers, fish industry and catering facilities. Possible genetic predisposition for allergy to Anisakis and the possible relationship between anisakiasis and cancer would also require further investigation.

Advances in Omic Studies Drive Discoveries in the Biology of Anisakid Nematodes

Advancements in technologies employed in high-throughput next-generation sequencing (NGS) methods are supporting the spread of studies that, combined with advances in computational biology and bioinformatics, have greatly accelerated discoveries within basic and biomedical research for many parasitic diseases. Here, we review the most updated "omic" studies performed on anisakid nematodes, a family of marine parasites that are causative agents of the fish-borne zoonosis known as anisakiasis or anisakidosis. Few deposited data on Anisakis genomes are so far available, and this still hinders the deep and highly accurate characterization of biological aspects of interest, even as several transcriptomic and proteomic studies are becoming available. These have been aimed at discovering and characterizing molecules specific to peculiar developmental parasitic stages or tissues, as well as transcripts with pathogenic potential as toxins and allergens, with a broad relevance for a better understanding of host-pathogen relationships and for the development of reliable diagnostic tools.

Comparative Proteomics Analysis of Anisakis simplex s.s.-Evaluation of the Response of Invasive Larvae to Ivermectin

Ivermectin (IVM), an antiparasitic drug, has a positive effect against Anisakis simplex s.s. infection and has been used for the treatment and prevention of anisakiasis in humans. However, the molecular mechanism of action of IVM on A. simplex s.s. remains unknown. Herein, tandem mass tag (TMT) labeling and extensive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis were used to identify the effect of IVM on the proteome of A. simplex s.s. in vitro. During the study, 3433 proteins, of which 1247 had at least two protein unique peptides, were identified. Comparative proteomics analysis revealed that 59 proteins were differentially regulated (DRPs) in IVM-treated larvae, of which 14 proteins were upregulated and 38 were downregulated after 12 h of culture, but after 24 h, 12 proteins were upregulated and 22 were downregulated. The transcription level of five randomly selected DRPs was determined by real-time PCR as a supplement to the proteomic data. The functional enrichment analysis showed that most of the DRPs were involved in oxidoreductase activity, immunogenicity, protein degradation, and other biological processes. This study has, for the first time, provided comprehensive proteomics data on A. simplex s.s. response to IVM and might deliver new insight into the molecular mechanism by which IVM acts on invasive larvae of A. simplex s.s.

Differences in Gene Expression Profiles of Seven Target Proteins in Third-Stage Larvae of Anisakis simplex (Sensu Stricto) by Sites of Infection in Blue Whiting (Micromesistius poutassou)

The third-stage larvae of the parasitic nematode genus Anisakis tend to encapsulate in different tissues including the musculature of fish. Host tissue penetration and degradation involve both mechanic processes and the production of proteins encoded by an array of genes. Investigating larval gene profiles during the fish infection has relevance in understanding biological traits in the parasite’s adaptive ability to cope with the fish hosts’ defense responses. The present study aimed to investigate the gene expression levels of some proteins in L3 of A. simplex (s.s.) infecting different tissues of blue whiting Micromesistius poutassou, a common fish host of the parasite in the NE Atlantic. The following genes encoding for Anisakis spp. proteins were studied: Kunitz-type trypsin inhibitor (TI), hemoglobin (hb), glycoprotein (GP), trehalase (treh), zinc metallopeptidase 13 (nas 13), ubiquitin-protein ligase (hyd) and sideroflexin 2 (sfxn 2). Significant differences in gene transcripts (by quantitative real-time PCR, qPCR) were observed in larvae located in various tissues of the fish host, with respect to the control. ANOVA analysis showed that relative gene expression levels of the seven target genes in the larvae are linked to the infection site in the fish host. Genes encoding some of the target proteins seem to be involved in the host tissue migration and survival of the parasite in the hostile target tissues of the fish host.

Anisakis and Hysterothylacium species in Mediterranean and North-East Atlantic fishes commonly consumed in Spain: Epidemiological, molecular and morphometric discriminant analysis

The consumption of raw fish parasitized with larval ascaridoid nematodes of the family Anisakidae can cause anisakiasis, provoking gastrointestinal and/or allergic symptomatology. The main causative agents in the Anisakis genus are the sibling species Anisakis simplex sensu stricto (s.s.) and A. pegreffii of the A. simplex sensu lato (s.l.) complex. Larvae of A. simplex (s.l.) are frequently detected in fish commonly consumed in Spain, as are larvae of the genus Hysterothylacium of the family Raphidascarididae, associated with allergic reactions but not considered pathogenic. Reported here are the results of an epidemiological survey of ascaridoid larvae in three commonly consumed fish species in Spain, horse mackerel (Trachurus trachurus) (n = 52), blue whiting (Micromesistius poutassou) (n = 93) and anchovy (Engraulis encrasicolus) (n = 69), caught in the North-Eastern Atlantic, West Mediterranean and Adriatic Sea. The larvae found in the dissected fish were identified in the following order of abundance: A. simplex (s.l.) (n = 2003), Hysterothylacium aduncum (n = 422), H. fabri (n = 180) and A. physeteris (n = 15). Binomial regression analysis showed a correlation between A. simplex (s.l.) and Hysterothylacium larvae abundance and the host geographical location, the North-Eastern Atlantic being the area with the highest parasitation. Fish length and weight and Fulton's condition factor were correlated with A. simplex (s.l.) abundance only in horse mackerel. There was a significant presence of A. simplex (s.l.) and H. aduncum larvae in the musculature of North-Eastern Atlantic blue whiting, the most parasitized part being the anteroventral region, followed equally by the anterodorsal and central sections. The ITS rDNA of larvae of the sibling species A. simplex (s.s.) and A. pegreffii was identified by PCR-RFLP, and a binary logistic regression model was developed to study their morphometric differentiation. Anisakis simplex (s.s.) was detected in the North-Eastern Atlantic and A. pegreffii in all the areas studied. The morphometric analysis discriminated between the two species at the third and fourth larval stages (L3 and L4), the latter obtained by in vitro culture in RPMI-1640 medium. Two discriminant functions were obtained for the L3 and L4 larvae, the ventricle being a key parameter for specific differentiation in both stages, providing taxonomical criteria that could be used besides molecular identification. The present study reveals differences in the parasitation of the studied fish, including the distribution of larvae in the musculature, related to the host species and its geographical origin.

De novo transcriptome sequencing and analysis of Anisakis pegreffii (Nematoda: Anisakidae) third-stage and fourth stage larvae

Anisakis pegreffii is known as one of the causes of a fish-borne zoonosis, anisakidosis. Despite its significant public health and food hygiene impacts, little is known of the pathogenesis, genetic background of this parasite, at least partly due to the lack of genome and transcriptome information. In this study, RNA-seq and de novo assembly were conducted to obtain transcriptome profiles of the A. pegreffii third and fourth larvae. The third stage larvae (APL3) were collected from chub mackerel and the fourth stage larvae (APL4) were obtained by in vitro culture. In total, 47,243 and 43,660 unigenes were expressed in APL3 and APL4 transcriptomes. Of them, 18,753 were known and 28,490 were novel for APL3, while 18,996 were known and 24,664 were novel for APL4. The most abundantly expressed genes in APL3 were mitochondrial enzymes (COI, COII, COIII) and polyubiquitins (UBB, UBIQP_XENLA). Collagen-related genes (col-145, col-34, col-138, Bm1_54705, col-40) were the most abundantly expressed in APL4. Mitochondrial enzyme genes (COIII, COI) were also highly expressed in APL4. Among the transcripts, 614 were up-regulated in APL3, while 1,309 were up-regulated in APL4. Several protease and protein biosynthesis-related genes were highly expressed in APL3, all of which are thought to be crucial for invading host tissues. Collagen synthesis-related genes were highly expressed in APL4, reflecting active biosynthesis of collagens occurs during moulting process of APL4. Of these differentially expressed genes, several genes (SI, nas-13, EF-TSMT, SFXN2, dhs-27) were validated to highly transcribed in APL3, while other genes (col-40, F09E10.7, pept-1, col-34, VIT) in APL4. The biological roles of these genes in vivo will be deciphered when the reference genome sequences are available, together with in vitro experiments.

Genome-wide analysis of Anisakis simplex sensu lato: the role of carbohydrate metabolism genes in the parasite's development

Anisakis simplex sensu lato is a parasitic nematode which can cause gastric symptoms and/or allergic reactions in humans who consume raw and undercooked fish. Anisakiasis poses a growing health problem around the globe because it causes non-specific symptoms and is difficult to diagnose. This genome-wide study was undertaken to expand our knowledge of A. simplex s.l. at the molecular level and provide novel data for biological and biotechnological research into the analyzed species and related nematodes. A draft genome assembly of the L3 stage of A. simplex s.l. was analyzed in detail, and changes in the expression of carbohydrate metabolism genes during the parasite's life cycle were determined. To our knowledge, this is the first genome to be described for a parasitic nematode of the family Anisakidae to date. We identified genes involved in parasite-specific pathways, including carbohydrates metabolism, apoptosis and chemo signaling. A total of 7607 coding genes were predicted. The genome of A. simplex s.l. is highly similar to genomes of other parasitic nematodes. In particular, we described a valuable repository of genes encoding proteins of trehalose and glycogen metabolism, and we developed the most comprehensive data set relating to the conversion of both saccharides which play important roles during the parasite's life cycle in a host environment. We also confirmed that trehalose is synthesized at the expense of glycogen. Trehalose anabolism and glycogen catabolism were the predominant processes in stages L4 and L5, which could confirm our and other authors' previous reports that trehalose is synthesized at the expense of glycogen. The A. simplex s.l. genome provides essential data for post-genomic research into the biology of gastrointestinal and allergic anisakiasis in humans and the biology of other important parasitic helminths.

Gene expression profiles of antigenic proteins of third stage larvae of the zoonotic nematode Anisakis pegreffii in response to temperature conditions

Anisakis pegreffii, a recognised etiological agent of human anisakiasis, is a parasite of homeothermic hosts at the adult stage and of ectothermic hosts at the third larval stage. Among distinct factors, temperature appears to be crucial in affecting parasite hatching, moulting and to modulate parasite-host interaction. In the present study, we investigated the gene transcripts of proteins having an antigenic role among excretory secretory products (ESPs) (i.e., a Kunitz-type trypsin inhibitor, A.peg-1; a glycoprotein, A.peg-7; and the myoglobin, A.peg-13) after 24 h, in A. pegreffii larvae maintained in vitro, under controlled temperature conditions. Temperatures were 37 °C and 20 °C, resembling respectively homeothermic and ectothermic hosts conditions, and 7 °C, the cold stress condition post mortem of the fish host. Primers of genes coding for these ESPs to be used in quantitative real-time PCR were newly designed, and qRT-PCR conditions developed. Expression profiles of the genes A.peg-1 and A.peg-13 were significantly up-regulated at 20 °C and 37 °C, with respect to the control (larvae kept at 2 °C for 24 h). Conversely, transcript profiles of A.peg-7 did not significantly change among the chosen temperature conditions. In accordance with the observed transcript profiles, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed the presence of the three target ESPs at 37 °C, while only A.peg-13 was observed at 7 °C. The results suggest that temperature conditions do regulate the gene expression profiles of A.peg-1 and A.peg-13 in A. pegreffii larvae. However, regulation of the glycoprotein A.peg-7 is likely to be related to other factors such as the host's immune response.

Microbiota and gut ultrastructure of Anisakis pegreffii isolated from stranded cetaceans in the Adriatic Sea

BACKGROUND

Inferring the microbiota diversity of helminths enables depiction of evolutionarily established ecological and pathological traits that characterize a particular parasite-host interaction. In turn, these traits could provide valuable information for the development of parasitosis control and mitigation strategy. The parasite Anisakis pegreffii (Nematoda: Anisakidae) realizes the final stage of its life-cycle within gastric chambers of aquatic mammals, causing mild-to-moderate granulomatous gastritis with eosinophilic infiltrate, to severe ulcerative gastritis with mixed inflammatory infiltrate, often associated with bacterial colonies. However, its interaction with the host microbiota remains unknown, and might reveal important aspects of parasite colonization and propagation within the final host.

METHODS

MySeq Illumina sequencing was performed for the 16S rRNA gene from microbiota isolated from larvae, and uterus and gut of adult A. pegreffii parasitizing stranded striped dolphins (Stenella coeruleoalba). To assess the potential presence of Brucella ceti within isolated microbiota, Brucella-targeted real-time PCR was undertaken. In addition, TEM of the gastrointestinal tract of the infective third-stage (L3) and transitioning fourth-stage larvae (L4) was performed to characterize the morphological differences and the level of larval feeding activity.

RESULTS

In total, 230 distinct operational taxonomic units (OTUs) were identified across all samples (n = 20). The number of shared taxa was lower than the number of taxa found specifically in each parasite stage or organ. The dominant taxon was Mycoplasmataceae (genus Mycoplasma) in the gut and uterus of adult A. pegreffii, whereas Fusobacteriaceae (genus Cetobacterium) was the most abundant in 40% of larvae, alongside Mycoplasmataceae. No B. ceti DNA was detected in any of the microbiota isolates. TEM revealed differences in gut ultrastructure between L3 and L4, reflecting a feeble, most likely passive, level of feeding activity in L3.

CONCLUSIONS

Microbiota from L3 was more related to that of the gut rather than the uterus of adult A. pegreffii. Taxa of the larval microbiota showed qualitative and quantitative perturbations, likely reflecting the propagation through different environments during its life-cycle. This suggests an ontogenetic shift in the alpha and beta diversity of microbial communities from uterus-derived towards cetacean-derived microbiota. Although TEM did not reveal active L3 feeding, microbiota of the latter showed similarity to that of an actively feeding adult nematode.

Differential proteolytic activity in Anisakis simplex s.s. and Anisakis pegreffii, two sibling species from the complex Anisakis simplex s.l., major etiological agents of anisakiasis

Proteolytic activity was studied in two sibling species of Anisakis (Nematoda: Anisakidae), A. simplex s.s. and A. pegreffii, throughout their in vitro development from third larval stage (L3) from the host fish (L3-0h) to fourth larval stage (L4) obtained in culture. Proteases have a significant role in the lifecycle of the parasite and in the pathogen-host relationship. Proteolytic activity peaks were detected at pH 6.0 and 8.5. Protease activity was detected in all the developmental stages of the two species studied at both pH values. These pH values were used for assaying with specific inhibitors which permitted the determination of metalloprotease activity, and, to a lesser extent, that of serine and cysteine protease. Aspartic protease activity was only detected at pH 6.0. At this pH, L4 larvae showed higher proteolytic activity than L3 larvae in both species (p < 0.001), the majority of activity being due to metalloproteases and aspartic proteases, which could be related to nutrition, especially the latter, as occurs in invertebrates. At pH 8.5, proteolytic activity was higher in A. simplex s.s. than in A. pegreffii (p < 0.01). At this pH, the majority of activity was due to metalloproteases in all developmental phases of both species, although, in L3-0h, the activity of these proteases was significantly higher (p < 0.03) in A. simplex s.s. than in A. pegreffii. This could be related to the greater invasive capacity of the former. Serine proteases have frequently been implicated in the invasive capacity and pathogenicity of some parasites. This may be related to the significantly higher activity (p ≤ 0.05) of serine protease in all the larval stages of A. simplex studied at pH 6.0. Thus, there are interspecific differences in proteases that have been related to pathogenesis in nematodes. These differences could thus be contributing to the previously reported differences in pathogenicity between these two Anisakis species.

A scanning electron microscopy study of Anisakis physeteris molecularly identified: from third stage larvae from fish to fourth stage larvae obtained in vitro

The development of the fourth larval stage (L4) of Anisakis physeteris was studied using scanning electron microscopy (SEM), comparing it with third larval stage (L3) recently obtained from the host fish, blue whiting (Micromesistius poutassou), from the western Mediterranean Sea (east coast of Spain, zone FAO 37.1.1). After molting to L4, samples of the parasite were examined at different times in order to observe their development. Following collection of the L4, a small portion was taken from the middle of the larva for molecular identification, confirming in all cases that it was A. physeteris. The anterior and posterior sections of the larvae were prepared for morphological study by SEM. The development of a row of denticles on each of the three prominent lips, almost reaching the buccal commisures, was observed in the L4. Pores of unknown function were found in the upper external part of each lip. Clearly developed cephalic papillae, amphids, and deirids were also observed in L4, while, although present in L3, these were beneath the cuticle. Phasmids were detected in L4 but not in L3. The L4 tail finished in a conical lobe with a blunt point, absent in L3. In the oldest L4, some preanal papillae were observed beneath the cuticle in males, while, in females, the vulva could be seen by light microscopy, apparently still covered by the cuticle.

Modelling studies determing the mode of action of anthelmintics inhibiting in vitro trehalose-6-phosphate phosphatase (TPP) of Anisakis simplex s.l

The trehalose-6-phosphate phosphatase (TPP) enzyme is involved in the synthesis of trehalose, the main sugar in the energy metabolism of nematodes. TPP is a member of the HAD-like hydrolase superfamily and shows a robust and specific phosphatase activity for the substrate trehalose-6-phosphate. The presence of conserved active sites of TPP in closely related nematodes and its absence in humans makes it a promising target for antiparasitic drugs. In the present study, homology modeling, molecular docking and MD simulation techniques were used to explore the structure and dynamics of TPP. In the active site, a magnesium ion is stabilized by 3 coordinate bonds formed by D₁₈₉, D₁₉₁ and D₄₀₀. The key amino acids involved in ligand binding by the enzyme are C₁₉₈, Y₂₀₁,T₃₅₇, D₁₉₁ and Y₁₉₇. This study relied on docking to select potential inhibitors of TPP which were tested in vitro for sensitivity to anthelmintic drugs such as levamisole and ivermectin targeting Anisakis simplex. The higher toxicity of LEV than IVM was demonstrated after 96 h, 30% of larvae were motile in cultures with 100 μg/ml of LEV and 1000 μg/ml of IVM. We identified drug combination of LEV-IVM against in vitro A. simplex as agonistic effect (CI = 1.1). Levamisole appeared to be a more effective drug which inhibited enzyme activity after 48 h and expression of mRNA after 96 h at a concentration of 10 μg/ml. This preliminary study predicted the structure of TPP, and the results of an in vitro experiment involving A. simplex will contribute to the development of effective inhibitors with potential antiparasitic activity in the future.

Autonomy and integration in complex parasite life cycles

Complex life cycles are common in free-living and parasitic organisms alike. The adaptive decoupling hypothesis postulates that separate life cycle stages have a degree of developmental and genetic autonomy, allowing them to be independently optimized for dissimilar, competing tasks. That is, complex life cycles evolved to facilitate functional specialization. Here, I review the connections between the different stages in parasite life cycles. I first examine evolutionary connections between life stages, such as the genetic coupling of parasite performance in consecutive hosts, the interspecific correlations between traits expressed in different hosts, and the developmental and functional obstacles to stage loss. Then, I evaluate how environmental factors link life stages through carryover effects, where stressful larval conditions impact parasites even after transmission to a new host. There is evidence for both autonomy and integration across stages, so the relevant question becomes how integrated are parasite life cycles and through what mechanisms? By highlighting how genetics, development, selection and the environment can lead to interdependencies among successive life stages, I wish to promote a holistic approach to studying complex life cycle parasites and emphasize that what happens in one stage is potentially highly relevant for later stages.

Expression of Genes Encoding the Enzymes for Glycogen and Trehalose Metabolism in L3 and L4 Larvae of Anisakis simplex

Trehalose and glycogen metabolism plays an important role in supporting life processes in many nematodes, including Anisakis simplex. Nematodes, cosmopolitan helminths parasitizing sea mammals and humans, cause a disease known as anisakiasis. The aim of this study was to investigate the expression of genes encoding the enzymes involved in the metabolism of trehalose and glycogen—trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), glycogen synthase (GS), and glycogen phosphorylase (GP)—in stage L3 and stage L4 larvae of A. simplex. The expression of mRNA all four genes, tps, tpp, gs, and gp, was examined by real-time polymerase chain reaction. The A. simplex ribosomal gene (18S) was used as a reference gene. Enzymatic activity was determined. The expression of trehalose enzyme genes was higher in L3 than in L4 larvae, but an inverse relationship was noted for the expression of gs and gp genes.

Recent Advances in Elucidating Nematode Moulting - Prospects of Using Oesophagostomum dentatum as a Model

There are major gaps in our knowledge of many molecular biological processes that take place during the development of parasitic nematodes, in spite of the fact that understanding such processes could lead to new ways of treating and controlling parasitic diseases via the disruption of one or more biological pathways in the parasites. Progress in genomics, transcriptomics, proteomics and bioinformatics now provides unique opportunities to investigate the molecular basis of key developmental processes in parasitic nematodes. The porcine nodule worm, Oesophagostomum dentatum, represents a large order (Strongylida) of socioeconomically important nematodes, and provides a useful platform for exploring molecular developmental processes, particularly given that this nematode can be grown and maintained in culture in vitro for periods longer than most other nematodes of this order. In this article, we focus on the moulting process (ecdysis) in nematodes; review recent advances in our understanding of molecular aspects of moulting in O. dentatum achieved by using integrated proteomic-bioinformatic tools and discuss key implications and future prospects for research in this area, also with respect to developing new anti-nematode interventions and biotechnological outcomes.

Expression patterns and structural modelling of Hsp70 and Hsp90 in a fish-borne zoonotic nematode Anisakis pegreffii

Heat shock proteins (HSPs) are essential molecular chaperones that are highly conserved across organisms. They have a pivotal function in responding to thermal stress and are responsible for many cellular functions. Here, we aimed to elucidate the possible roles of Hsp70 and Hsp90 in the life cycle of the parasitic nematode Anisakis, particularly third- and fourth-stage larvae, from cold-blooded fish to warm-blooded marine mammals or accidentally to human hosts. We examined the expression profiles of Hsp70 and Hsp90 in different developmental stages of Anisakis pegreffii. The open reading frame of Hsp70 of A. pegreffii was 1950 bp, and deduced amino acid sequence showed high homology with those of other nematodes. Heatmap analysis revealed sequence identity of Hsp70 and Hsp90 in 13 important parasitic species, human and yeast. On heatmap and phylogenetic analysis, ApHsp70 and ApHsp90 shared the highest amino acid sequence identity with other nematodes and formed a monophyletic clade. The three-dimensional (3D) structure prediction of the newly characterized ApHsp70 and known ApHsp90 gene showed highly conserved motifs between A. pegreffii and other species. Quantitative real-time PCR and western blot analysis revealed higher mRNA and protein expression for ApHsp70 and ApHsp90 in fourth- than third-stage larvae, with higher mRNA and protein expression for ApHsp70 than ApHsp90. ApHsp70 and ApHsp90 may play important roles in Anisakis in response to thermal stress and might be important molecules in the development of A. pegreffii, which has implications for its control.

Pathogenic potential of two sibling species, Anisakis simplex (s.s.) and Anisakis pegreffii (Nematoda: Anisakidae): in vitro and in vivo studies

The pathogenic potentials of two sibling nematodes Anisakis simplex sensu stricto (s.s.) and A. pegreffii were compared by in vitro and in vivo studies. Live third-stage larvae of each species were subjected to agar blocks made using PBS or RPMI-1640, overlaid with different supernatants (artificial gastric juice, PBS, and RPMI-1640), and their penetration ability was compared. Their tolerance of artificial gastric juice was also tested. Further, they were introduced into rats by gastric intubation, and the in vivo locations of them were investigated. A. pegreffii showed higher penetration ability than A. simplex (s.s.) in most of the experimental conditions, except for the RPMI-1640 agar block overlaid with artificial gastric juice. In an acid tolerance test, the mean survival times were 6.1 days for A. simplex (s.s.) and 4.2 days for A. pegreffii. In an animal experiment, A. simplex (s.s.) stayed for a shorter time in the stomachs of rats than A. pegreffii. Some A. pegreffii and A. simplex (s.s.) were embedded in the gastric mucosa or freely existed in the abdominal cavity. All of these results suggest that A. pegreffii has the pathogenic potential to cause anisakidosis in humans when ingested, as does A. simplex (s.s.).

Anisakid parasites in commercial hake ceviche in southern Chile

The objective of this research was to determine the occurrence of anisakid nematode larvae in hake ceviche sold in restaurants in Valdivia (39°48'S, 73°14'W) and Niebla (39°49'S, 73°22'W), Chile. Between August and November 2012, 78 portions of ceviche were collected (6 from each of the 13 restaurants that sell this product). Each portion was weighed and divided into approximately 30-g samples, which were placed in petri dishes with 0.15 M NaCl. All samples were manually shredded and then examined with a stereomicroscope. Muscles of 41 southern hake (Merluccius australis), a fish sold fresh in Valdivia, also were examined by candling to determine the presence of anisakid larvae. The presence of Pseudoterranova larvae in ceviche sold in Chile was identified for the first time. The pH of ceviche ranges from 4.1 to 4.8, which favors the presence of viable anisakid larvae that tolerate the acid pH similar to that found in the stomach of their mammalian host. No significant differences (P > 0.05) in the prevalence, mean abundance, and mean density of anisakid larvae in ceviche were found between localities. Larvae were detected in ceviche from 3 of 6 restaurants in Valdivia and 4 of 7 restaurants in Niebla. Of the 78 examined portions of ceviche, 21.8% had larvae. The prevalence of viable larvae was 16.7 and 7.1% in the examined portions from Valdivia and Niebla, respectively. In the 41 hake muscle samples from Valdivia, the prevalence (4.9%), mean abundance (0.1), and mean density (0.03) was the same for Pseudoterranova and Anisakis larvae. No inspection processes or pretreatments are currently in place for raw fish to achieve safe conditions for ceviche in restaurants from Valdivia and Niebla.

Anthelmintic activities of aporphine from Nelumbo nucifera Gaertn. cv. Rosa-plena against Hymenolepis nana

Nelumbo nucifera Gaertn. cv. Rosa-plena (Nelumbonaceae), commonly known as lotus, is a perennial aquatic plant grown and consumed throughout Asia. All parts of N. nucifera have been used for various medicinal purposes in oriental medicine. From the leaves of Nelumbo nucifera Gaertn. cv. Rosa-plena (an aquatic plant), liriodenine (1), lysicamine (2), (−)-anonaine (3), (-)-asimilobine (4), (-)-caaverine (5), (-)-N-methylasimilobine (6), (-)-nuciferine (7), (-)-nornuciferine (8), (-)-roemerine (9), 7-hydroxydehydronuciferine (10) and cepharadione B (11) were isolated and identification and anthelmintic activities of aporphine was evaluated against Anisakis simplex and Hymenolepis nana. This study found that the above constituents killed H. nana or reduced their spontaneous movements (oscillation/peristalsis). However, the above constituents at various concentrations demonstrated no larvicidal effect or ability to halt spontaneous parasite movement for 72 h against A. simplex, respectively. In addition, according to an assay of cestocidal activity against H. nana and nematocidal activity against A. simplex, we found that the above compounds showed greater lethal efficacy on H. nana than against A. simplex. Further investigation showed that these above constituents have effects against peroxyl radicals under cestocidal effect. Together, these findings suggest that these constituents of Nelumbo nucifera Gaertn. cv. Rosa-plena might be used as anthelmintic agents against H. nana.

Antioxidant, anti-adipocyte differentiation, antitumor activity and anthelmintic activities against Anisakis simplex and Hymenolepis nana of yakuchinone A from Alpinia oxyphylla

Background

Alpinia oxyphylla is a common remedy in traditional Chinese medicine. Yakuchinone A is a major constituent of A. oxyphylla and exhibits anti-inflammatory, antitumor, antibacterial, and gastric protective activities.

Methods

Antioxidant and antitumor characteristics of yakuchinone A in skin cancer cells as well as novel mechanisms for the inhibition of adipocyte differentiation, cestocidal activities against Hymenolepis nana adults, and nematocidal activities against Anisakis simplex larvae are investigated.

Results

Yakuchinone A presents the ability of the removal of DPPH·and ABTS⁺ free radicals and inhibition of lipid peroxidation. Yakuchinone A suppresses intracellular lipid accumulation during adipocyte differentiation in 3 T3-L1 cells and the expressions of leptin and peroxisome proliferator-activated receptor γ (PPARγ). Yakuchinone A induces apoptosis and inhibits cell proliferation in skin cancer cells. The inhibition of cell growth by yakuchinone A is more significant for non-melanoma skin cancer (NMSC) cells than for melanoma (A375 and B16) and noncancerous (HaCaT and BNLCL2) cells. Treatment BCC cells with yakuchinone A shows down-regulation of Bcl-2, up-regulation of Bax, and an increase in cleavage poly (ADP-ribose) polymerase (PARP). This suggests that yakuchinone A induces BCC cells apoptosis through the Bcl-2-mediated signaling pathway. The anthelmintic activities of yakuchinone A for A. simplex are better than for H. nana.

Conclusions

In this work, yakuchinone A exhibits antioxidative properties, anti-adipocyte differentiation, antitumor activity, and anthelmintic activities against A. simplex and H. nana.

Brazilein from Caesalpinia sappan L. Antioxidant Inhibits Adipocyte Differentiation and Induces Apoptosis through Caspase-3 Activity and Anthelmintic Activities against Hymenolepis nana and Anisakis simplex

Brazilein, a natural, biologically active compound from Caesalpinia sappan L., has been shown to exhibit anti-inflammatory and antioxidant properties and to inhibit the growth of several cancer cells. This study verifies the antioxidant and antitumor characteristics of brazilein in skin cancer cells and is the first time to elucidate the inhibition mechanism of adipocyte differentiation, cestocidal activities against Hymenolepis nana, and reduction of spontaneous movement in Anisakis simplex. Brazilein exhibits an antioxidant capacity as well as the ability to scavenge DPPH^• and ABTS^•+ free radicals and to inhibit lipid peroxidation. Brazilein inhibited intracellular lipid accumulation during adipocyte differentiation in 3T3-L1 cells and suppressed the induction of peroxisome proliferator-activated receptor γ (PPARγ), the master regulator of adipogenesis, suggesting that brazilein presents the antiobesity effects. The toxic effects of brazilein were evaluated in terms of cell viability, induction of apoptosis, and the activity of caspase-3 in BCC cells. The inhibition of the growth of skin cancer cells (A431, BCC, and SCC25) by brazilein is greater than that of human skin malignant melanoma (A375) cells, mouse leukemic monocyte macrophage (RAW 264.7 cells), and noncancerous cells (HaCaT and BNLCL2 cells). The anthelmintic activities of brazilein against Hymenolepis nana are better than those of Anisakis simplex.

Proteolytic activity in Hysterothylacium aduncum (Nematoda: Anisakidae), a fish gastrointestinal parasite of worldwide distribution

Proteases have a significant role in the life cycle of parasites and the pathogen-host relationship, being regarded as important virulence factors. In the parasitic nematode Hysterothylacium aduncum proteolytic activity was measured during in vitro development from third larval stage (L3) to mature adult, using DQ red casein as a fluorogenic substrate. Proteolytic activity was detected in all the developmental stages studied and at all pH values within the range employed (2.0-7.5). The assay with specific inhibitors permitted the determination of metalloprotease activity, and, to a lesser extent, that of aspartate- and cysteine-protease. Serine-protease activity was the lowest of those studied. In L3 recently collected from the host fish (L3-0 h), the greatest activity was found at an optimum pH of 4.0 and was mainly inhibited by 1,10-phenathroline (metalloprotease inhibitor). This metalloprotease activity in L3-0 h (infective stage) may be related to the invasion of the host tissues by this larva. In the other developmental stages, the greatest protease activity was found at pH 5.5, although at pH 4.0 a lower activity peak was detected. On the other hand, our data show that the proteolytic activity of the nematode varies according to the presence of pepsin (an aspartic-protease) in the culture medium. Thus, at pH 4.0, activity was greater in the absence of pepsin, with increasing aspartic-protease activity. Together with the detection of aspartic-, cysteine- and metallo-protease (enzymes involved in digestion in invertebrates) in all the developmental stages of the parasite taking place in the digestive tract of the host fish, this allows us to suggest that the pepsin in the culture medium mimics the predigestion conditions in the habitat of the worm within the host and that the activity detected may have, amongst others, a digestive function.

Teladorsagia circumcincta: survival of adults in vitro is enhanced by the presence of a mammalian cell line

Adult Teladorsagia circumcincta survival and motility in vitro was examined in a range of different cell culture media, supplements and gas mixes. Under optimum conditions, worms survived for 14 days, exhibiting high motility for 9 days and egg production for 72 h. Optimum conditions involved co-culture of worms with a HeLa cell line in a supplemented cell medium (CEM) and an atmosphere containing 10% CO(2), 5% O(2) 85% N(2), 65% humidity at 37 degrees C. The incubation medium consisted of Minimum Essential Medium with 10% fetal calf serum, 1% non-essential amino acids, 1% glutamax and 1% penicillin-neomycin-streptomycin cocktail mix. Compared with optimum conditions, incubation in CEM alone, cell conditioned CEM, RPMI alone, Medium 199 alone, reduced CO(2) or O(2), or when cells were replaced with Escherichia coli, both survival and motility were reduced. Optimum conditions for adult T. circumcincta maintenance for culture, anthelmintic testing or generation of excretory/secretory products are described.

Allergenic properties and cuticle microstructure of Anisakis simplex L3 after freezing and pepsin digestion

This article examines the viability of and the alterations to the larval cuticle and the pattern of the antigens released when live or frozen Anisakis simplex larvae were treated with acid and pepsin. The results showed that freezing did not greatly alter the larva body. If ruptures were observed, the antigen release to the incubation media was not enhanced, and most of the antigenic content was retained inside the bodies of the larvae. The immunoblotting assay demonstrated that most of the antigens released, including the allergen Ani s 4, were resistant to pepsin. Freezing killed the larvae, but their survival was not compromised by acid treatment or pepsin digestion when kept chilled. All these findings support recommendations about freezing fish for consumption raw or undercooked to prevent human infection by A. simplex larvae. However, our data show that the antigenicity of the larvae is preserved after freezing and may explain why some sensitized patients develop symptoms after ingestion of infested frozen fish.

Morphological differences between larvae and in vitro-cultured adults of Anisakis simplex (sensu stricto) and Anisakis pegreffii (Nematoda: Anisakidae)

Proper identification of Anisakis species infecting host fishes is very important to both human health and fish disease diagnosis. The foremost problem in the identification of Anisakis larvae in fishes is that L3 larvae cannot be easily differentiated morphologically, especially between A. simplex (sensu stricto) (s.s.) (Rudolphi, 1809) and A. pegreffii Campana-Rouget et Biocca, 1955. Instead, molecular means such as allozyme, mitochondrial DNA (mtDNA) cox2 region and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses had been successfully used. In this study, morphological differences of L3 larvae collected from fishes and in vitro-cultured L4 larvae and adult A. simplex (s.s.) and A. pegreffii were evaluated. Anisakis larvae were collected from 7 different host fishes within Japan. Undamaged A. simplex (s.s.) and A. pegreffii collected from Oncorhynchus keta (Walbaum) and Scomber japonicus Houttuyn, respectively, were used for in vitro-culture in order to obtain L4 and adult stages. Species identification was confirmed by PCR-RFLP analysis of the ITS region (ITS1-5.8S-ITS2) of ribosomal DNA and by mtDNA cox2 gene sequencing. Results revealed that L3, L4 and adult stages of A. simplex (s.s.) and A. pegreffii are morphologically distinguishable based on ventriculus length, wherein the former has longer ventriculus (0.90-1.50 mm) than the latter (0.50-0.78 mm). For oesophagus/ventriculus ratio, these two species are distinguishable only during L4 and adult stages. Also, adult male A. simplex (s.s.) and A. pegreffii were found to be distinguishable by differences in the distribution pattern of the caudal papillae, particularly the 3rd pair of distal papillae.

Anisakis simplex: CO2-fixing enzymes and development throughout the in vitro cultivation from third larval stage to adult

We studied the effect of CO(2) on the in vitro cultivation of Anisakis simplex, an aquatic parasitic nematode of cetaceans (final hosts) and fish, squid, crustaceans and other invertebrates (intermediate/paratenic hosts), and, occasionally, of man (accidental host). The results showed that a high pCO(2), at a suitable temperature, is vital for the optimum development of these nematodes, at least from the third larval stage (L3) to adult. After 30 days cultivation in air, molting to L4 (fourth larval stage) was reduced to 1/3, while survival was about 1/3 of that when cultivated in air + 5% CO(2). The activity of the CO(2)-fixing enzymes, PEPCK and PEPC, was also studied. Throughout the development of the worms studied, PEPCK activity was much higher than that of PEPC (e.g., 305 vs. 6.8 nmol/min.mg protein, respectively, in L3 collected from the host fish). The activity of these enzymes in the worms cultivated in air + 5% CO(2) was highest during M3, and was also generally higher than that of those cultivated in air only, especially during molting from L3 to L4 (e.g., in recently molted L4, PEPCK activity was 3.7 times greater than that of PEPC 2.9 times greater than when cultivated in air).

CO(2)-fixing enzymes during moulting from third larval to fourth larval stage of Anisakis simplex and Hysterothylacium aduncum (Nematoda: Anisakidae)

The fixing of CO(2) is an important metabolic process for many organisms. In the anisakid nematodes, CO(2) has been shown to be necessary for their development, at least in vitro. The presence of CO(2) stimulates the moulting (M3) of the larvae from the third (L3) to the fourth (L4) stage and prolongs the survival, at least, in vitro. We determined the activity of CO(2)-fixing enzymes, common to many organisms, in two anisakids: Anisakis simplex, a parasite of cetaceans, and Hysterothylacium aduncum, a parasite of fish. Although no activity was detected for pyruvate carboxylase or carboxylating-malic enzyme, we detected phosphoenolpyruvate carboxykinase (PEPCK) and phosphoenolpyruvate carboxylase (PEPC) activity. In A. simplex, PEPCK was clearly higher than that of PEPC throughout the moulting process studied. In H. aduncum, although the activity of both enzymes was of similar magnitude, they showed different behaviour; PEPCK activity decreased after the moulting to L4, PEPC activity increased so that the ratio PEPCK/PEPC activity decreased from 1.90 before moulting to 0.59 after.

Population structure of Anisakis simplex (Nematoda) in harbor porpoises Phocoena phocoena off Denmark

The population structure and habitat selection of Anisakis simplex in 35 harbor porpoises off Denmark are described. The nematodes were collected from the stomach and duodenal ampulla and were categorized as third-stage larvae, fourth-stage larvae, subadults, and adults. The porpoises harbored 8,043 specimens of A. simplex. The proportion of adults and subadults increased with infrapopulation size. The number of development stages across infrapopulations covaried significantly (Kendall's test of concordance). Concordance was higher in hosts with the highest intensities than in those with low and medium intensities. All stages occurred mainly in the forestomach, but this trend was stronger for the adults. Adult and subadult sex ratios did not depart significantly from 1:1. Our data suggested that recruitment and duration of each stage were the main factors accounting for infrapopulation structure. The preference of A. simplex for the forestomach conformed with previous studies, but the narrower distribution of adults relative to other stages might indicate a strategy to enhance mating opportunities. Information on sex ratios of A. simplex is scarce and contradictory. We suggest that the discrepancies might partly reflect differences in categorization criteria and statistical methods.