Preliminary Data on the Occurrence of Anisakis spp. in European Hake (Merluccius merluccius) Caught Off the Portuguese Coast and on Reports of Human Anisakiosis in Portugal

Evaluating fatty acid profiles in anisakid nematode parasites and adjacent tissue of European hake (Merluccius merluccius): a first insight into local host-parasite lipid dynamics

Parasitism in fish is a widespread and ecologically significant phenomenon, affecting fish in both wild and aquaculture environments. Comprehending parasitism is essential for managing fish populations, protecting fish health, and preventing human exposure to zoonotic parasites. Understanding lipid dynamics between parasitic organisms and their hosts is crucial for elucidating host-parasite interactions. Although the third larval (L3) stage of anisakid larvae is not a developing stage, and therefore not as dependent on the host for the acquisition of nutrients, there are hints of interplay between parasites and fish hosts, also in terms of lipid content. This study aimed to characterize for the first time the fatty acid profiles of anisakid nematode parasites and adjacent tissue in the European hake (Merluccius merluccius) in order to shed some light on these intricate relationships. Fatty acid analysis revealed significant differences in the percentages of individual fatty acids between anisakid nematodes and adjacent European hake tissue. Anisakids presented a higher content in stearic (18:0), vaccenic (18:1n-7), and linoleic (18:2n-6) acids, while in turn, the belly flap tissue of the fish presented significantly higher contents in palmitic (16:0) and especially docosahexaenoic acid (22:6n-3) than the parasite. These differences suggest unique lipid metabolic pathways between parasite and fish, and that parasitism and the possible acquisition of lipids from the host (hake) do not profoundly shape the fatty acid profile of the parasites. Furthermore, the distinct fatty acid signatures described for parasites and hosts may serve as baselines to follow possible changes in the ecological statuses of both species and even to appraise the nutritional features of European hake when affected by parasitism. This study provides valuable insights into the lipid dynamics within host-parasite systems and underscores the importance of further research to unravel the complexities of these interactions.

Immunoproteomic and Immunoinformatic Approaches Identify Sensitive Antigens for Diagnosing Anisakis pegreffii Infection

Anisakis are foodborne parasites that opportunistically parasitize humans, leading to acute abdominal symptoms and allergies. Besides gastroscopy, no other diagnostic technique is available. Consequently, it is necessary to identify specific biomarkers and then develop molecular techniques for diagnosing Anisakis infection. In the present study, we used immunoproteomic and immunoinformatic approaches to identify sensitive antigens for diagnosing Anisakis pegreffii infection. A total of three proteins, including Ani609 (VDK51609), Ani941 (VDK75941), and AniS13, were identified based on immunoinformatic results. Then, the indirect ELISA method was developed based on the recombinant proteins, showing a similar diagnostic capability to that of parasitic soluble proteins. Next, a Gaussia luciferase immunoprecipitation assay (LIPS) was further developed upon the fusion of the proteins and Gaussia luciferase. The LIPS method indicated that A. pegreffii infection could be detected in rats as early as 1 week post infection, especially for Ani941. Overall, we identified the novel antigens using immunoproteomic and immunoinformatic approaches and then developed a sensitive method for diagnosing A. pegreffii infection, particularly for the early stage.

Detection and Characterization of Visceral Anisakid Nematodes in Blue Whiting from Portuguese Waters

This study employs molecular detection techniques, including conventional PCR and Sanger sequencing, to investigate the prevalence, species composition and public health implications of Anisakid nematodes in blue whiting (Micromesistius poutassou) caught off the Portuguese coast. With Portugal's high fish consumption rates and increasing preference for raw or undercooked seafood, the risk of parasitic infections, particularly anisakidosis, is rising. Fifty blue whiting fish were examined, showing a 100% infection rate with Anisakid larvae. Molecular analysis identified 68.1% of the larvae as Anisakis simplex, 18.1% as Anisakis pegreffii, and 13.8% as Hysterothylacium aduncum, marking the first report of H. aduncum in blue whiting in Portugal. Phylogenetic analysis based on the internal transcribed spacer (ITS) 1, 5.8S ribosomal RNA and ITS-2 confirmed the species classification. Notably, 42.9% of the fish were infected with multiple Anisakid species, increasing the risk of allergenic sensitization. Statistical analysis showed no significant correlation between fish width and parasitic load, and a weak negative correlation was found between fish length and parasitic load. The study contributes to food safety by integrating molecular tools that enable rapid and accurate species identification, offering new insights into the detection of biological contaminants in seafood. These findings are significant considering the rising trend in raw seafood consumption, underscoring the urgent need for enhanced detection strategies and broader parasite monitoring programs to mitigate public health risks. The high prevalence of parasitized fish highlights the necessity for the implementation of safe cooking practices to reduce the risk of anisakidosis. Further research into the allergenic potential of Hysterothylacium spp. and the ecological factors influencing this nematode distribution is recommended.

EFSA Panel on Biological Hazards (BIOHAZ), Allende A, Alvarez‐Ordóñez A, Bortolaia V, Bover‐Cid S, De Cesare A, Dohmen W, Guillier L, Herman L, Jacxsens L, Nauta M, Mughini‐Gras L, Ottoson J, Peixe L, Perez‐Rodriguez F, Skandamis P, Suffredini E, Buchmann K, Levsen A, Mattiucci S, Mladineo I, Santos MJ, Guerra B, Goudjihounde SM, Hempen M, Bolton D. 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 2

The objective of this opinion was to determine if any wild caught fish species, originating from specific fishing grounds and consumed in the EU/EFTA could be considered free of zoonotic parasites. In this Opinion the term 'fishery products' only refers to fresh finfish. As there are multiple fish species and numerous potential parasites, Anisakis sp. was used as an indicator of zoonotic parasites in marine areas. This parasite species is particularly suited as it is common in marine environments, capable of infecting multiple fish species and is the subject of the majority of published studies. On the rare occasion where Anisakis sp. data were not available, or all tests were negative, other parasites such as Contracaecum osculatum (s.l.) and/or Phocanema spp. were considered. In freshwater systems, all zoonotic parasites were investigated. Consumption, import and landing data were used to determine the most relevant fish species and, where possible, the source fishing areas were identified. The most commonly consumed wild caught fish species in the EU/EFTA include tuna, cod, Alaskan pollock, hake, herring, sardines, mackerel, trout and saithe. Although the majority of these fish are caught in the Atlantic Ocean, the Mediterranean and the Black Sea (37) as well as several areas in the Indian Ocean, imported fish may originate from any global fishing areas, with the exception of Antarctica. Based on the data, at least one zoonotic parasite has been reported in at least one fish species in each of the FAO marine fishing areas. Thus, due to relative low fish host specificity of the zoonotic parasites, the panel concluded that all wild caught fish species may be exposed to and infected with zoonotic parasites. The same applies to freshwater fishing areas, with many areas having multiple studies reporting the presence of zoonotic parasites in the wild caught fish species.

Location and elimination of Anisakis simplex third stage larvae in Atlantic herring Clupea harengus L

We here describe the location of anisakid third stage larvae in Atlantic herring Clupea harengus L. caught in the North Sea in August 2023. We further demonstrate how industrial processing (mechanical gutting, removal of entrails, head, tail, hypaxial anterior musculature and vertebral column) reduces the overall infection and worm load in the musculature. The isolated anisakid larvae were identified as Anisakis simplex sensu stricto by a combination of morphometrics and molecular methods (PCR of rDNA and mtDNA, sequencing, BLAST analysis). As a baseline we examined a total of 75 specimens of freshly caught and ungutted herring and showed a positive correlation between host size (fish length and weight) and infection level. The overall prevalence of infection was 84 %, the mean intensity 11.3 (range 1-38 parasites per fish) and the abundance 9.52. The main part of the overall worm population was associated with stomach and pyloric caeca in the body cavity (77 %) and only 5 % was found in the musculature. Larvae occurred in the hypaxial part of the musculature (21), the epaxial part (7 worms) and the caudal part (5 worms). The prevalence of muscle infection was 28 % and the mean intensity 1.6 (range 1-5) parasites per fish and abundance 0.44 parasites per fish. In order to assess the effect of industrial processing on worm occurrence in the fish we examined a total of 67 specimens of herring, from exactly the same batch, but following processing. This included removal of organs in the body cavity, cutting the lower part of the hypaxial segment but leaving the right and left musculature connected by dorsal connective tissue. Five out of these fish carried one larva (prevalence 7.5%, mean intensity 1, abundance 0.07 larvae per fish), and these worms were located in the ventral part of the anterior musculature (2), in the central part of the anterior musculature (2) and one larva in the central part of the caudal musculature. The industrial processing reduced the overall occurrence (abundance) of worms in the fish from 9.52 to 0.07 (136 times reduction) and the occurrence in the musculature from 0.44 to 0.07 (6.28 times reduction). The overall prevalence was reduced from 84 % to 7.5 % (11.2 times reduction). Muscle infection prevalence fell from 28 % to 7.5 % (3.7 times reduction). We then followed another batch of herring following a marinating process (11% NaCl for 24 h and subsequent incubation in acetic acid and vinegar) by artificially digesting the flaps during week 1-8. Although a total of 31 larvae were recovered from 144 fish examined no live nematode larvae were isolated. The importance of fish handling, processing and marination for consumer safety is discussed.

EFSA Panel on Biological Hazards (BIOHAZ), Koutsoumanis K, Allende A, Alvarez‐Ordóñez A, Bover‐Cid S, Chemaly M, De Cesare A, Herman L, Hilbert F, Lindqvist R, Nauta M, Nonno R, Peixe L, Ru G, Simmons M, Skandamis P, Suffredini E, Buchmann K, Careche M, Levsen A, Mattiucci S, Mladineo I, Santos MJ, Barcia‐Cruz R, Broglia A, Chuzhakina K, Goudjihounde SM, Guerra B, Messens W, Guajardo IM, Bolton D. 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.

Variation in the levels of anisakid infection in the European anchovy Engraulis encrasicolus (Linnaeus) from the Bay of Biscay during the period 2000-2023 (ICES Subarea 8)

The European anchovy Engraulis encrasicolus is one of the most important commercial species in the Bay of Biscay (ICES Subarea 8), and our analysis focused on the analysis of the temporal mean abundance, prevalence, and intensity of Anisakis spp. larvae species in anchovies from ICES Subarea 8 in the years 2000, 2001, 2014-2016, and 2019-2023. Prevalence in adult individuals of anchovy was only 1% in 2000 but increased to 90% in 2014. Since 2015, the prevalence has decreased, and the number of individuals affected in 2023 accounted for 17.6%. The mean abundance showed a similar trend, with a peak of 3.79 nematodes/anchovy in 2014, falling to 0.21 in 2023. The species A. simplex sensu stricto and A. pegreffii were identified by PCR/SANGER sequencing and PCR/RLFP techniques in 2019 and 2020. Anisakis simplex (s.s.) was the most abundant species and, according to the results returned by these two techniques, it accounted for an average of 62.4% and 52.1% of total nematodes in 2019 and 2020, respectively. The results of studies monitoring infection levels in anchovies showed that the mean abundance and prevalence changed over the course of the study period and that the proportion of different species of Anisakis is also subject to variation from year to year.

Preliminary data on the occurrence of PAH and Anisakis spp. in Moroccan anchovies: Environmental parasitology and human health risk

This survey focuses on an environmental parasitology study by investigating Polycyclic Aromatic Hydrocarbons (PAH) bioaccumulation and the occurrence of Anisakis spp. on common anchovies collected from Moroccan coasts over 9 months through chemical (PAH) and Biological (Biometrics and parasitic) analysis. Obtained results were statistically analyzed and human health risks from anchovies consumption were assessed. The results obtained highlighted the good biological and chemical status of this fish in all stations of Morocco's coasts. Anisakis spp. was present in only four stations in the Atlantic fringe (maximum prevalence 22.22 %). Results have shown non-significant differences for tissue nature (Muscle, viscera) or spatial variation and were within a low range of concentrations well below the European Commission standards. Results have shown no serious harmful risk for humans from this fish consumption (ILCR and HI), and statistical analysis had shown positive correlations between prevalence and Chr, prevalence and sex-ratio, and prevalence and weight.

Anisakis infection in anchovies (Engraulis encrasicolus) from Iberian waters, southwestern Europe: Post-mortem larval migration

The Anisakis larvae presence in fish for human consumption is a health risk that needs to be monitored. The anchovy is a fish that is highly appreciated by consumers and that can harbour Anisakis. It is thus necessary to periodically evaluate the presence of anisakid larvae in them. So, anchovies from Iberian Peninsula coasts were analysed. Fish examination for macroscopic nematodes showed L3s of both Anisakis type I and Hysterothylacium aduncum. The Anisakis prevalence varies with the catching area and the fish size. The muscle prevalence was 7.45% (mean intensity 1.75; range 1-5). Molecular analysis showed 110 A. simplex s.s. (17 in muscle), 22 A. pegreffii (3) and 7 hybrid genotype individuals (1). Considering that most of the Iberian Peninsula coasts are a sympatry area between these two Anisakis species, it has been observed that A. simplex s.s./A. pegreffii ratio increases from south to north in a clockwise direction. Also, 19 larvae were detected on the fish surface from the Bay of Biscay, indicating the ability of these larvae to migrate after the fish death. The A. simplex s.s./A. pegreffii larvae proportion found on the anchovy surface is similar to the found in viscera and lower than in muscle, suggesting that most of the larvae migrating to the surface must have come from the visceral package. This confirms the importance of removing fish viscera immediately after capture, for those fish species where this is possible. As both species cause anisakiasis/anisakidosis, these data show a real risk to human health, especially in dishes highly prized in Mediterranean countries prepared with raw or semi-raw anchovies.

Anisakid nematodes in Trichiurus lepturus and Saurida undosquamis (Teleostea) from the South-West Indian Ocean: Genetic evidence for the existence of sister species within Anisakis typica (s.l.), and food-safety considerations

Nematode parasites of the genus Anisakis (Nematoda, Anisakidae) are considered among the most important biological hazards in seafood products worldwide. In temperate and tropical waters, the most common species appears to be Anisakis typica, generally found around the viscera and sporadically in the flesh of various fish host species. This study investigated the infection sites and genetic diversity of A. typica infecting commercial fishes from the South-West Indian Ocean. Largehead hairtail (N = 20) and brushtooth lizardfish (N = 72) fished off Tanzania were inspected for anisakid nematodes by UV-press. A subsample of 168 nematodes were identified by sequence analyses of the cox2 mtDNA gene and ITS region of rDNA. The species A. typica (s.l.) (N = 166), Pseudoterranova ceticola (N = 1) and Anisakis paggiae (N = 1) were molecularly identified. Phylogenetic analysis of A. typica (s.l.) sequences based on both genes, indicated the existence of two distinct phylogenetic lineages forming two well-supported clades. The first clade comprised 12 A. typica specimens including individuals from its type locality (central Atlantic Ocean). The second clade comprising 154 specimens, clustered with reference sequences retrieved from GenBank including one apparently undescribed taxon, i.e., Anisakis sp. 1, and A. typica var. indonesiensis. The two reciprocally monophyletic clades are closely related and correspond to two distinct sister species within A. typica (s.l.), presently indicated as A. typica sp. A and A. typica sp. B. Two and four fixed alternative nucleotide substitutions (SNPs), i.e., diagnostic positions, between the two taxa, respectively, were found at the mtDNA cox2 and the ITS region of rDNA. The genetic data, as well as their occurrence in sympatry, strengthens the hypothesis that the actual specimens represent two distinct gene pools. The occurrence of both A. typica sp. A and A. typica sp. B in the musculature of freshly examined T. lepturus and S. undosquamis, suggests that both species can migrate intra-vitam into the flesh. Although the zoonotic potential of A. typica s.l. is still unclear, the presence of these parasites in the musculature, edible part of the fish, raises health concerns for consumers.

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Phylogenetic analyses suggest the existence of two sister species within A. typica (s.l.).

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typica sp. A and sp. B can both migrate intra-vitam into the fish flesh.

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Occurrence of A. typica (s.l.) larvae in the fish flesh may raise food safety concerns.

Anisakid Nematodes and Potential Risk of Human Anisakiasis through the Consumption of Hake, Merluccius spp., Sold Fresh in Spanish Supermarkets

Nematode parasite species belonging to the Anisakis simplex complex are the most important cause of human anisakiasis through the consumption of (mainly) undercooked, previously not frozen, or conveniently treated fish. In Spain, the consumption of hake has been recognized as an important source of this parasitosis. With the aim of shedding light on the risk factors that can influence the potential risk of human anisakiasis in Spain through the consumption of fresh hake sold by nationwide supermarket chains, a total of 536 small hake specimens belonging to the species Merluccius bilinearis caught off the Northeast American coasts and Merluccius merluccius caught in the Northeast Atlantic and Mediterranean waters was analysed. Anisakids morphologically identified as Anisakis type I were found as the most prevalent and the most abundant species and were considered the main potential cause of human anisakiasis. Intrinsic and extrinsic factors concerning the hake, such as its origin and season of capture, its size, as well as the days passed between its capture and consumption, should be taken into account to avoid this human parasitosis. It is essential that consumers have access to fish label information which should include, as regulated by the European Commission, traceability data.

Seafood safety and food-borne zoonoses from fish: Examining the risk of Anisakis in the Portuguese Population and Consumer Risk Perceptions of Fish Consumption

Parasitic nematodes of the genus Anisakis are the causative agent of anisakiosis, an important fish‐borne zoonosis. Humans are infected through consumption of raw or undercooked fish, contaminated with the parasite. Infection can result in both gastrointestinal and allergic symptoms. There are few reports of anisakiosis in Portugal, but evidence of Anisakis allergy exists, indicating that exposure is occurring in the population. The European Food Risk Assessment Fellowship Programme (EU‐FORA) work programme, entitled: ‘Food safety of fish and zoonoses: fish consumption and microbiological risk assessment and perception, from fisherman to final consumers in Portugal’ was hosted by the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), in Porto, Portugal. It aimed to gather information on risk perception and attitudes in the Portuguese population to contamination of fish with Anisakis spp. and on their knowledge of methods to prevent infection. In addition, it aimed to examine the risk of anisakiosis in the Portuguese population.