Tandem Mass Tagging (TMT) Reveals Tissue-Specific Proteome of L4 Larvae of Anisakis simplex s. s.: Enzymes of Energy and/or Carbohydrate Metabolism as Potential Drug Targets in Anisakiasis

Re-evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 1: ToRs1-3

Surveillance data published since 2010, although limited, showed that there is no evidence of zoonotic parasite infection in market quality Atlantic salmon, marine rainbow trout, gilthead seabream, turbot, meagre, Atlantic halibut, common carp and European catfish. No studies were found for greater amberjack, brown trout, African catfish, European eel and pikeperch. Anisakis pegreffii, A. simplex (s. s.) and Cryptocotyle lingua were found in European seabass, Atlantic bluefin tuna and/or cod, and Pseudamphistomum truncatum and Paracoenogonimus ovatus in tench, produced in open offshore cages or flow-through ponds or tanks. It is almost certain that fish produced in closed recirculating aquaculture systems (RAS) or flow-through facilities with filtered water intake and exclusively fed heat-treated feed are free of zoonotic parasites. Since the last EFSA opinion, the UV-press and artificial digestion methods have been developed into ISO standards to detect parasites in fish, while new UV-scanning, optical, molecular and OMICs technologies and methodologies have been developed for the detection, visualisation, isolation and/or identification of zoonotic parasites in fish. Freezing and heating continue to be the most efficient methods to kill parasites in fishery products. High-pressure processing may be suitable for some specific products. Pulsed electric field is a promising technology although further development is needed. Ultrasound treatments were not effective. Traditional dry salting of anchovies successfully inactivated Anisakis. Studies on other traditional processes - air-drying and double salting (brine salting plus dry salting) - suggest that anisakids are successfully inactivated, but more data covering these and other parasites in more fish species and products is required to determine if these processes are always effective. Marinade combinations with anchovies have not effectively inactivated anisakids. Natural products, essential oils and plant extracts, may kill parasites but safety and organoleptic data are lacking. Advanced processing techniques for intelligent gutting and trimming are being developed to remove parasites from fish.

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.

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.