Anisakis infestation in marine fish and cephalopods from Galician waters: an updated perspective

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.

A review on fish-borne zoonotic parasites in Iran

BACKGROUND

Fish is a great nutritious food and provides quality protein and a variety of vitamins and minerals. This contributes significantly to the economy and food security in Iran. However, there are safety concerns related to the presence of zoonotic parasites.

OBJECTIVES

The objective of this study is, therefore, to review fish-borne zoonotic parasites in Iran.

METHODS

Keywords such as fish-borne, parasites, zoonotic, Iran, and some names of fish-borne zoonotic parasites were searched in databases including PubMed, Science Direct, Elsevier, SID, Magiran, Irandoc, Google Scholar and the World Health Organization.

RESULTS

The most common fish-borne parasites with zoonotic potential identified in reports in the literature were the protozoa Balantidium spp., Myxobolus spp. and Sarcosystis sp.; the trematodes Heterophyes heterophyes and Clinostomum complanatum; the cestodes Ligula intestinalis and Diphyllobothrium latum; the nematodes Pseudoterranova sp., Anisakis spp., Contracaecum spp., Raphidascaris spp., Eustrongylides spp. and Capillaria sp.; and the acanthocephal Corynosoma spp.

CONCLUSIONS

The potential risk factors for the transmission of fish-borne zoonotic parasites to humans are consumption of raw or undercooked infected fish, contact with contaminated water and contact with infected fish. There is a need for epidemiological surveillance of fish for parasites with zoonotic potential and of occurrence of infections in humans to better understand the public health significance and design prevention programs.

Large-scale genetic investigation of nematode diversity and their phylogenetic patterns in New Zealand's marine animals

Nematodes constitute one of the most speciose metazoan groups on earth, and a significant proportion of them have parasitic life styles. Zooparasitic nematodes have zoonotic, commercial and ecological significance within natural systems. Due to their generally small size and hidden nature within their hosts, and the fact that species discrimination using traditional morphological characteristics is often challenging, their biodiversity is not well known, especially within marine ecosystems. For instance, the majority of New Zealand's marine animals have never been the subject of nematode studies, and many currently known nematodes in New Zealand await confirmation of their species identity with modern taxonomic techniques. In this study, we present the results of an extensive biodiversity survey and phylogenetic analyses of parasitic nematodes infecting New Zealand's marine animals. We used genetic data to differentiate nematodes to the lowest taxonomic level possible and present phylogenies of the dominant clades to illustrate their genetic diversity in New Zealand. Our findings reveal a high diversity of parasitic nematodes (23 taxa) infecting New Zealand's marine animals (62 of 94 free-living animal species investigated). The novel data collected here provide a solid baseline for future assessments of change in diversity and distribution of parasitic nematodes.

Morphological and Molecular Identification of Anisakis spp. (Nematoda: Anisakidae) in Commercial Fish from the Canary Islands Coast (Spain): Epidemiological Data

The study aimed to perform the molecular identification of Anisakis larvae in commercial fish from the coast of the Canary Islands and to provide data on their infection level for the host and the species of this nematode parasite that we could find in several species of commercial interest in the Canary Archipelago. Fish specimens (n = 172) from the Canary coasts were examined for parasites. In total, 495 larvae were identified; PCR was carried out for the entire ITS rDNA and cox2 mtDNA region, obtaining sixteen sequences for the entire ITS rDNA region and fifteen for the cox2 mtDNA, this being the first contribution of nucleotide sequences of Anisakis species of fish caught from the Canary Islands. An overall prevalence of 25% was obtained in the fish analyzed, and five species of Anisakis were identified, these being Anisakis simplex (s.s.), Anisakis pegreffii, Anisakis physeteris, Anisakis nascettii and Anisakis typica and the hybrid Anisakis simplex x Anisakis pegreffii. The results obtained in this study have relevance for public health, since the pathology will depend on the species of Anisakis, so it is important to know the health status of fish in the waters of the Canary Islands to assure a safer consumption and take adequate measures, in addition to the provision of epidemiological data.

Nematode Parasites of the European Pilchard, Sardina pilchardus (Walbaum, 1792): A Genuine Human Hazard?

Simple Summary

The European pilchard is one of the most frequently consumed fish species in Mediterranean countries, especially in Italy and Spain, and has been reported as the cause of at least eight human anisakidosis cases in Spain since 1991, the parasitic disease caused by the ingestion of fish or cephalopods infested by the larval stage of anisakid nematodes. With the aim to shed light on the potential human parasitosis risk posed by these nematode larvae, we helminthologically analyzed a total of 350 sardines (European pilchard) captured in the Atlantic Ocean (175 sardines) and the Mediterranean Sea (175 specimens), acquired in various Spanish nationwide supermarket chains. The statistical analysis of some helminth parameters revealed a higher presence of nematodes belonging to the genus Hysterothylacium (frequency of parasitation of 24.29%; total mean parasite burden of 2.36), usually considered non-parasitic for humans (only three cases reported worldwide), when compared to nematodes of the genus Anisakis (5.71%; 0.16). The human anisakidosis risk after the consumption of raw or undercooked sardines and the role of Hysterothylacium, the most frequent nematode, is discussed, providing information to consumers. To avoid human infection by anisakid larval nematodes, the established preventive measures are confirmed and new ones are proposed.

Abstract

The European pilchard is one of the most frequently consumed fish species in Mediterranean countries, especially in Italy and Spain, and has been reported as the cause of at least eight human anisakidosis cases in Spain. With the aim to shed light on the potential human parasitosis risk posed by nematode larvae belonging to families Anisakidae or Raphidascarididae, a total of 350 sardines captured in the Atlantic Ocean (175 specimens) and the Mediterranean Sea (175 specimens), acquired in various Spanish nationwide supermarket chains, were helminthologically analyzed. The statistical analysis of some helminth parameters revealed a higher presence of nematodes belonging to the genus Hysterothylacium (prevalence 24.29%; mean abundance of 2.36), usually considered non-parasitic for humans (only three cases reported worldwide), when compared to nematodes of the genus Anisakis (5.71%; 0.16). The human anisakidosis risk after the consumption of raw or undercooked sardines and the role of Hysterothylacium, the most frequent nematode, is discussed, providing information to consumers. To avoid human infection by anisakid larval nematodes, the established preventive measures are confirmed and new ones are proposed, such as the consumption of sardines preferably caught in the Mediterranean and of small-sized specimens available, and the immediate evisceration after fishing.

Analysis of potential drivers of spatial and temporal changes in anisakid larvae infection levels in European hake, Merluccius merluccius (L.), from the North-East Atlantic fishing grounds

We analysed the spatial and temporal variability of Anisakis larvae infection in hake (Merluccius merluccius) from the North-East Atlantic from 1998 to 2020 and the potential drivers (i.e., environmental and host abundance) of such variation. The results showed that hake from separate sea areas in the North Atlantic have marked differences in temporal abundance levels. Hake larger than 60 cm were all parasitized in all ICES (International Council for the Exploration of the Sea) subareas 6, 7, and 8. The belly flaps were the most parasitized parts of the flesh, accounting for 92% of the total. Individuals of Anisakis simplex, Anisakis pegreffii, Anisakis spp. and a hybrid of Anisakis simplex × pegreffii were genetically identified, and Anisakis simplex as the most abundant (88-100%). An ecological niche model of Anisakis occurrence in fishes in the NE Atlantic was built to define the thermal optimum and environmental ranges for salinity, depth, chlorophyll concentration, and diffuse attenuation. The temporal variability of anisakid infection in fishes in the last two decades indicated an increase in the NE Atlantic at an annual rate of 31.7 nematodes per total number of specimens examined per year. This rise in infection levels could be triggered by the increase in intermediate host fish stocks, especially hake in the area.

Infection Rate in Seabasses Fed with Viscera Parasitised by Anisakid Larvae

PURPOSE

It has been suggested that the removal of infected viscera on board is responsible for the high prevalence of anisakid larvae present in wild fish species. The aim of this work is to assess the re-infection capacity of anisakid larvae in European seabasses, a natural host species for the parasite by feeding with pieces of parasitised hake liver under controlled experimental conditions.

METHODS

To prove this potential link between manipulation and re-infestation, 50 farmed seabasses free of anisakid nematodes were fed with fresh hake liver pieces naturally infested with anisakid larvae.

RESULTS

After digestion periods from 4 to 21 days, the seabasses showed a prevalence of Anisakis of 6%, and a low retention rate of 0.11 larvae/seabass after four days' digestion, and 0.0021 after 21 day digestion. Two nematodes were found in the intestine and in the visceral cavity, and 13 Anisakis were found partially digested in the stomach of one same individual after 4 day digestion. Results showed that only a small number of Anisakis ingested with the viscera were able to reinfect the seabasses, as most of the larvae seemed to be quickly digested or defecated.

CONCLUSION

it seems that the availability of larvae that could re-enter the life cycle and re-infect a fish after the removal and discarding the infected viscera on board could be much less important than commonly believed.

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.

Anisakicidal Effects of R (+) Limonene: An Alternative to Freezing Treatment in the Industrial Anchovy Marinating Process

Anisakiasis is a fish-borne zoonotic disease caused by the ingestion of raw/undercooked fishes or cephalopods parasitized by members of the genus Anisakis. Freezing ensures the inactivation of viable Anisakis larvae; however, since it affects the organoleptic properties of food, essential oils and their compounds were proposed as an alternative. In this study, fresh anchovy fillets were experimentally parasitized with L3 Anisakis larvae to test the anisakicidal efficacy of R (+) limonene (LMN) in marinated fishery products. The anisakicidal effectiveness and organoleptic influence of several LMN concentrations (0.5%, 1%, and 5%) were tested during the marinating process (MS) and storage in sunflower seed oil (SO) of marinated anchovy fillets. Double treatment (DT) with 1% LMN was also performed both during marination and subsequent storage in oil. MS treatment resulted only in a reduction in larvae viability after 48 h, while a complete inactivation was observed in SO after 8, 10, and 20 days of treatment with 5%, 1%, and 0.5% LMN, respectively. DT was the most effective with complete larval inactivation after 7 days. Only 5% LMN influenced the sensory characteristics of the fillets, resulting, however, in a pleasant lemon-like odor and taste. Considering the results obtained, LMN might be a suitable natural alternative to manage Anisakis risk in the fishery industry.

Molecular Epidemiology of Anisakis spp. in Wedge Sole, Dicologlossa cuneata (Moreau, 1881), from Fishmarkets in Granada (Southern Spain), Caught in Two Adjacent NE and CE Atlantic Areas

The presence of third stage larvae (L3) of Anisakis spp. in wedge sole, Dicologlossa cuneata (Moreau, 1881), purchased in fishmarkets in the city of Granada (Andalusia, southern Spain) was assessed. The wedge sole were caught in two FAO zones: area 27.IXa NE Atlantic (SW Spain coast) and area 34.1.11 CE Atlantic (NW Morocco coast). Only Anisakis larvae, type I, were detected in the largest fish (>20 cm) from the CE Atlantic. These were molecularly identified as A. simplex s.s. The prevalence (P) of Anisakis in this area was 12.5% and the mean intensity (MI) was 1. The presence of Hysterothylacium spp. larvae was also detected in the fish from both areas, with the prevalence being approximately double in the CE Atlantic area (12.5 vs. 5.7). A comparison between the Anisakis-infected and non-infected fish from this area showed that the former were significantly longer than the latter (p < 0.01). These results show that Anisakis parasitization of wedge sole sold in the markets of the city of Granada is of low prevalence and intensity (P = 4.5, MI = 1), especially in those from area 27.IXa (P = 0), indicating that the risk of human infection is low, particularly as this fish is traditionally prepared by deep-frying in oil in Andalusia (southern Spain).

Anisakid and Raphidascaridid parasites in Trachurus trachurus: infection drivers and possible effects on the host's condition

This study investigated the distribution of nematode larvae of Anisakidae and Raphidascarididae (genera Anisakis and Hysterothylacium) in Trachurus trachurus (Linnaeus, 1758) in the Ligurian and central-northern Tyrrhenian Seas. The relationship between the number of parasites and the length and weight parameters of the fish was assessed, and the possible effect of the parasites on the condition factor was evaluated. A total of 190 T. trachurus specimens were collected in July 2019. Parasites were found in 70 individuals. A total of 161 visible larvae were collected in the viscera. Morphological analysis revealed the presence of Anisakis spp. in 55 fish and Hysterothylacium spp. in 15 fish, while 5 fish showed coinfection with both genera. The specimens subjected to PCR (n = 67) showed that 85% of the Anisakis larvae analyzed belonged to the species A. pegreffii, while the remaining 15% belonged to hybrids of A. pegreffii-A. simplex (s.s.). A total of 58% (n = 7) of the Hysterothylacium larvae analyzed belonged to the species H. fabri, while 42% belonged to the species H. aduncum. Our results support the hypothesis that infection with these parasites does not affect the condition of the fish host analyzed, and that body size and depth are major drivers in determining infection levels with Anisakid and Raphidascaridid nematodes.

Biology, Epidemiology, Clinical Features, Diagnosis, and Treatment of Selected Fish-borne Parasitic Zoonoses

Fish-borne parasites have been part of the global landscape of food-borne zoonotic diseases for many decades and are often endemic in certain regions of the world. The past 20 years or so have seen the expansion of the range of fish-borne parasitic zoonoses to new geographic regions leading to a substantial public health burden. In this article, we summarize current knowledge about the biology, epidemiology, clinical characteristics, diagnosis, treatment and control of selected fish-borne helminthic diseases caused by parasitic roundworm (Anisakis), tapeworm (Dibothriocephalus), and fluke (Metagonimus). Humans acquire infection via consumption of raw or improperly cooked fish or fish products. The burden from these diseases is caused by morbidity rather than mortality. Infected patients may present with mild to severe gastrointestinal (eg, abdominal pain, diarrhea, and indigestion) or allergic manifestations. Patients are often admitted to the hospital or clinic with acute symptoms and no prior health problems and no travel history. Diagnosis is often established based on the detection of the diagnostic parasite stages (eg, eggs or tapeworm segments) in the patient's feces. Sometimes imaging is required to exclude other causes and avoid unnecessary surgery. Dibothriocephalus and Metagonimus are mainly treated with praziquantel. Extraction of adult Dibothriocephalus or Anisakis larvae from the bowel ensures complete elimination of the parasites and prevents a relapse of infection. The development and implementation of more efficient food safety and public health strategies to reduce the burden of zoonotic diseases attributable to fish-borne parasites is highly desirable.

Effectiveness of Gutting Blue Whiting (Micromesistius poutassou, Risso, 1827), in Spanish Supermarkets as an Anisakidosis Safety Measure

Anisakidosis is a parasitic zoonotic disease which can cause gastroallergic reactions in humans. In 2010, the European Food Safety Agency estimated that approximately 20,000 cases of anisakiasis had been reported across the world, with Spain having the highest number of infections in Europe. The blue whiting (Micromesistius poutassou, Risso, 1827) is one of the most widely fished species worldwide and represents around 25% of the white fish eaten in Spain. The Spanish Food Safety Authority requires obligatory evisceration of certain fish species before commercialization, but not for blue whiting. Nevertheless, some supermarkets carry this out themselves to prevent human infections and negative customer reactions deriving from the presence of ascaridoid larvae. To assess the effectiveness of eviscerations at supermarkets, a total of 320 blue whiting specimens were examined. The risk of larval migration from the visceral cavity to the musculature in gutted and ungutted fish was also assessed. Our results showed a total prevalence (25%) of ascaridoids in fish gutted at the supermarket, and a direct relationship was found between the presence of larvae in the muscle and time until evisceration. In ungutted fish, the standard length and weight were higher for infected than for non-infected fish. Also, massive infections had a higher prevalence in these larger specimens, in which the viability of larvae was also high. Larval viability was not found to be affected by a 24-h refrigeration period. Anisakis was the most prevalent genus identified in the fish examined. The results indicate that gutting at the supermarket is not an effective method for the total removal of ascaridoid larvae and that additional safety measures are advisable.

Anisakis simplex (s.s.) larvae (Nematoda: Anisakidae) hidden in the mantle of European flying squid Todarodes sagittatus (Cephalopoda: Ommastrephidae) in NE Atlantic Ocean: Food safety implications

Few reports exist upon the occurrence and localization of zoonotic anisakid nematodes in T. sagittatus, especially in the mantle of the squid. The occurrence and site of infection of larval anisakids in 98 T. sagittatus caught West off St. Kilda, NE Atlantic Ocean, were investigated. Squids were examined for anisakids using the UV-Press method. In total, 689 nematodes were detected in the viscera and mantle. According to morphology, all the larvae (L₃) were assigned to genus Anisakis. Diagnostic allozymes and mtDNA cox2 sequence analysis permitted to genetically identify all larvae as Anisakis simplex (s.s.) (N = 100). Overall prevalence (P = 81%) and mean intensity (mI = 8.6) of infection with A. simplex are provided. Most of the larvae present in the mantle cavity were embedded in the stomach wall or attached in the outer layer of the stomach and caecum (49%). Over a third of squids (37%) hosted A. simplex (s.s.) larvae in the mantle. A novel schematized representation of larvae distribution in the mantle is provided, showing where they were mostly located. According to the results obtained, the risk of anisakiasis associated with consumption of raw or undercooked T. sagittatus should be considered.

World-wide prevalence of Anisakis larvae in fish and its relationship to human allergic anisakiasis: a systematic review

The infective stage of Anisakidae nematodes responsible for allergic reactions in humans is found in a variety of edible fish and cephalopods. The identification of geographical regions that are high risk for infected seafood may help prevent allergic reactions in humans. Despite an abundance of published literature which has identified anisakid larvae in an array of edible seafood as well as scattered reports of human allergic anisakiasis, the relationship between the two has not been fully explored. Therefore, a systematic spatio-temporal study was conducted to determine the prevalence of Anisakis spp. in fish from January 2000 to August 2020 firstly to explore the relationship between fish infection and cases of allergic anisakiasis and secondly to use fish infection data to map potential allergic anisakiasis 'hot spots'. A systematic literature search for original English text articles was conducted through search engines, Web of Science, Scopus, PubMed, Science Direct and Google Scholar. Out of 3228 articles which describe anisakid infection in fish, 264 were used for data extraction. Of 904 articles describing allergic anisakiasis, 37 were used for data extraction. A qualitative summary of the extracted data was performed using equal interval method (ArcMap software) in order to compare the global distribution of Anisakis-infected fish. Of the 152-identified fish hosts, five families were most commonly infected with Anisakis spp. These included Lophiidae (86.9%), Trichiuridae (77.05%), Zeidae (70.9%), Merlucciidae (67.8%) and Gadidae (56.8%). The hot spot areas for allergic anisakiasis were North and northeast of Atlantic Ocean, southwest of USA, west of Mexico, south of Chile, east of Argentina, Norway, UK and west of Iceland (confidence 99%). The highest rate of allergic anisakiasis was in Portugal and Norway with the prevalence rate of 18.45-22.50%. Allergologists should consider allergic anisakiasis as a public health issue particularly in high-risk countries where high prevalences in fish have been demonstrated.

Investigation of Anisakis larvae in different products of ready-to-eat fish meat and imported frozen fish in Turkey

Globalization opens new market areas and affects food consumption habits, resulting in rapid and remarkable cultural change. Food habits such as consumption of raw fish meat have become popular, resulting in increased risk of emerging infectious diseases. Anisakis simplex sensu stricto (s.s) and A. pegreffii are the most common and important fish-borne zoonotic nematodes responsible for human anisakiasis, which occurs through the consumption of raw or undercooked fish as well as cooked fish due to their heat-stable allergens. Here, we investigated the prevalence, intensity, and abundance of Anisakis larvae in imported fish and ready-to-eat local fish products in Turkey. A total of 205 ready-to-eat fish products, 100 imported frozen Atlantic salmon (Salmo salar) fillets, and 100 imported frozen whole Atlantic mackerel (Scomber scombrus) were sampled from supermarkets, sushi restaurants, and fish markets. All samples were individually examined using a pepsin digestion technique. In total, 602 Anisakis type I larvae were recovered from 98/100 mackerel. No larvae were found in ready-to-eat products or frozen Atlantic salmon fillets. Overall, 8.8% of the larvae were found in the muscle tissue. The overall mean intensity and abundance of infection in mackerel were 6.14 and 6.02, respectively. The larvae were molecularly identified and their phylogenetic relationships with the relevant Anisakis sequences in GenBank were investigated. For this purpose, a subsample of randomly selected 100 Anisakis larvae were analyzed with PCR-RFLP of the ITS region. The larvae were identified as A. simplex (s.s.) (n = 87) and hybrids (n = 13). ITS and cox2 gene regions of all hybrids and randomly selected 50 A. simplex (s.s.) larvae were sequenced for species confirmation and phylogenetic analyses. No intraspecific nucleotide variation was found among the ITS sequences of either species. Seven and three haplotypes, respectively, were identified for A. simplex (s.s.) and hybrid species according to DNA polymorphism of the cox2 gene. Hybrids in our study clustered within the common A. simplex (s.s.) clade in the cox2 phylogenetic tree indicating the dominance of A. simplex (s.s) in the catching area of Atlantic mackerel. Consequently, our study indicates high occurrence of A. simplex (s.s.) larvae with an overall 98.0% prevalence in imported Atlantic mackerel, and highlights the importance of these fish as potential reservoirs for human allergic anisakiasis in Turkey and possibly in other countries.

Larval ascaridoid nematodes in horned and musky octopus (Eledone cirrhosa and E. moschata) and longfin inshore squid (Doryteuthis pealeii): Safety and quality implications for cephalopod products sold as fresh on the Italian market

The aim of this study was to evaluate the occurrence, infection level and distribution of ascaridoid larvae in cephalopod products sold in Italy. Data on the species most commonly commercialized as whole and fresh on the Italian market were collected. After comparing commercial and literature data, Eledone spp., comprising E. cirrhosa and E. moschata (horned octopus and musky octopus, respectively) and Doryteuthis pealeii (longfin inshore squid) were selected, as they had been rarely investigated. Overall, 75 Eledone spp. caught in the Mediterranean Sea (FAO area 37) and 70 D. pealeii from the Northwest Atlantic Ocean (FAO area 21) were examined by visual inspection and artificial digestion (viscera and mantle separately). Parasites were submitted to morphological and molecular analysis. Prevalence (P), mean intensity (MI) and mean abundance (MA) were calculated. In D. pealeii, 2 nematode larvae molecularly identified as Anisakis simplex s.s. were found in the viscera and in the mantle of two specimens (P: 2.9% 95% CI: 0-6.8%; MI: 1; MA: 0.028). In Eledone spp. 9 nematode larvae molecularly attributed to Hysterothylacium spp. were found in the mantle of 5 specimens (P: 6.7% 95% CI: 1-12.3%; MI: 1.8; MA: 0.12). This is the first report of A. simplex s.s. in D. pealeii. Considering the zoonotic and allergenic potential of these larvae and their localization also in the edible part (mantle), a potential public health issue exists.

Anisakid nematode species identification in harbour porpoises (Phocoena phocoena) from the North Sea, Baltic Sea and North Atlantic using RFLP analysis

Harbour porpoises (Phocoena phocoena) are the only native cetacean species in the German North and Baltic Seas and the final host of Anisakis (A.) simplex, which infects their first and second gastric compartments and may cause chronic ulcerative gastritis. Anisakis simplex belongs to the family Anisakidae (Ascaridoidea, Rhabditida) as well as the phocine gastric nematode species Pseudoterranova (P.) decipiens and Contracaecum (C.) osculatum. These nematode species are the main causative agents for the zoonosis anisakidosis. The taxonomy of these genus with life cycles including crustaceans and commercially important fish is complex because of the formation of sibling species. Little is known about anisakid species infecting porpoises in the study area. Mature nematodes and larval stages are often identifiable only by molecular methods due to high morphological and genetic similarity. The restriction fragment length polymorphism (RFLP) method is an alternative to sequencing and was applied to identify anisakid nematodes found in harbour porpoises from the North Sea, Baltic Sea and North Atlantic to species level for the first time. In the study areas, five gastric nematodes from different harbour porpoise hosts were selected to be investigated with restriction enzymes HinfI, RsaI and HaeIII, which were able to differentiate several anisakid nematode species by characteristic banding patterns. Anisakis simplex s. s. was the dominant species found in the North Sea and Baltic porpoises, identified by all three restriction enzymes. Additionally, a hybrid of A. simplex s. s. and A. pegreffii was determined by HinfI in the North Sea samples. Within the North Atlantic specimens, A. simplex s. s., P. decipiens s. s. and Hysterothylacium (H.) aduncum were identified by all enzymes. This demonstrates the value of the RFLP method and the chosen restriction enzymes for the species identification of a broad variety of anisakid nematodes affecting the health of marine mammals.

Occurrence of larval anisakids in horse mackerel (Trachurus trachurus) caught in Portuguese waters

The third-stage larvae (L3) of the Anisakidae family are parasitic nematodes with zoonotic impact and are frequently encountered in the organs and musculature of various fish intended for human consumption. Since Anisakis simplex (s.s.) and A. pegreffii are the major aetiological agents of human disease, this study aims to combine the morphological and molecular data on the recovered anisakid larvae to contribute to a simplified morphological distinction of those species and conducted a survey of anisakid larvae infection in horse mackerel (Trachurus trachurus). Here, 116 horse mackerel caught in Portuguese waters were analysed for the presence of L3 of anisakids, and 3148 larvae were collected, of which only 30% were retrieved during visual inspection. As such, visual inspection does not appear to be very effective in anisakid detection. A prevalence of 84.5% of infected fish was found, and the mean intensity and mean abundance were 32.1 and 27.1 parasites per fish, respectively. The morphological and molecular analyses of 196 L3 randomly chosen from the total sample of parasites demonstrated the presence of L3 of mostly Anisakis spp., with only one L3 of Hysterothylacium aduncum. Relative frequencies of 62.9% for A. pegreffii and 37.1% for A. simplex (s.s.) were obtained. The morphometry differences between these two sibling species were evaluated, and the results demonstrated significant differences between the length of the ventriculus and the length of the oesophagus. Precisely, A. simplex (s.s.) has a longer oesophagus and ventriculus than A. pegreffii. As such, these differences may be used to distinguish the two species through morphological analysis.

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.

Biomonitoring of Heavy Metal Pollution Using Acanthocephalans Parasite in Ecosystem: An Updated Overview

As a result of the global industrial revolution, contamination of the ecosystem by heavy metals has given rise to one of the most important ecological and organismic problems, particularly human, early developmental stages of fish and animal life. The bioaccumulation of heavy metals in fish tissues can be influenced by several factors, including metal concentration, exposure time, method of metal ingestion and environmental conditions, such as water temperature. Upon recognizing the danger of contamination from heavy metals and the effects on the ecosystem that support life on earth, new ways of monitoring and controlling this pollution, besides the practical ones, had to be found. Diverse living organisms, such as insects, fish, planktons, livestock and bacteria can be used as bioindicators for monitoring the health of the natural ecosystem of the environment. Parasites have attracted intense interest from parasitic ecologists, because of the variety of different ways in which they respond to human activity contamination as prospective indices of environmental quality. Previous studies showed that fish intestinal helminths might consider potential bioindicators for heavy metal contamination in aquatic creatures. In particular, cestodes and acanthocephalans have an increased capacity to accumulate heavy metals, where, for example, metal concentrations in acanthocephalans were several thousand times higher than in host tissues. On the other hand, parasitic infestation in fish could induce significant damage to the physiologic and biochemical processes inside the fish body. It may encourage serious impairment to the physiologic and general health status of fish. Thus, this review aimed to highlight the role of heavy metal accumulation, fish histopathological signs and parasitic infestation in monitoring the ecosystem pollutions and their relationship with each other.

Occurrence and molecular identification of Anisakis larval type 1 (Nematoda: Anisakidae) in marketed fish in Egypt

Anisakidosis is a zoonotic infection caused by members of the family Anisakidae. The presence of anisakid larvae in fish poses risk for humans and dissuade consumers from purchasing infected products. Although fish constitute important component of Egyptian diet, the prevalence of anisakid larvae in marketed fish in Egypt is not well described. Furthermore, the species of anisakid larvae is not defined in most of the available studies due to the over reliance on morphological analyses. The aim of the current work was to assess the prevalence and intensity of anisakid larvae in three common marketed fish in Egypt (Atlantic herring, Mediterranean horse mackerel and Atlantic mackerel) and to determine the species of the isolated larvae using morphological and molecular methods. Light and scanning electron microscope (SEM) analyses revealed the details of the isolated larvae. However, partial sequencing of cytochrome oxidase subunite-1 (mt cox1) gene revealed that all larvae isolated from Atlantic herring and Mediterranean horse mackerel belonged to Anisakis simplex sensu stricto with prevalence of 87.1% and 83.3%, respectively, whereas Atlantic mackerel harbored Anisakis typica with a prevalence of 42.8%. The Mediterranean horse mackerel demonstrated the highest larval mean intensity (n = 20 larvae/infected fish). This study highlights the importance of these fish as potential reservoirs for human anisakiasis in Egypt and possibly in other coastal countries.

The use of the so-called 'tubs' for transporting and storing fresh fishery products

On-land transport/storage of fresh fishery products (FFP) for up to 3 days in 'tubs' of three-layered poly-ethylene filled with freshwater and ice was compared to the currently authorised practice (fish boxes of high-density poly-ethylene filled with ice). The impact on the survival and growth of biological hazards in fish and the histamine production in fish species associated with a high amount of histidine was assessed. In different modelling scenarios, the FFP are stored on-board in freshwater or seawater/ice (in tubs) and once on-land they are 'handled' (i.e. sorted or gutted and/or filleted) and transferred to either tubs or boxes. The temperature of the FFP was assumed to be the most influential factor affecting relevant hazards. Under reasonably foreseeable 'abusive' scenarios and using a conservative modelling approach, the growth of the relevant hazards (i.e. Listeria monocytogenes, Aeromonas spp. and non-proteolytic Clostridium botulinum), is expected to be < 0.2 log10 units higher in tubs than in boxes after 3 days when the initial temperature of the fish is 0°C ('keeping' process). Starting at 7°C ('cooling-keeping' process), the expected difference in the growth potential is higher (< 1 log10 for A. hydrophila and < 0.5 log10 for the other two hazards) due to the poorer cooling capacity of water and ice (tub) compared with ice (box). The survival of relevant hazards is not or is negligibly impacted. Histamine formation due to growth of Morganella psychrotolerans under the 'keeping' or 'cooling-keeping' process can be up to 0.4 ppm and 1.5 ppm higher, respectively, in tubs as compared to boxes after 3 days, without reaching the legal limit of 100 ppm. The water uptake associated with the storage of the FFP in tubs (which may be up to 6%) does not make a relevant contribution to the differences in microbial growth potential compared to boxes.

Recent increase of ulcerative lesions caused by Anisakis spp. in cetaceans from the north-east Atlantic

Species of Anisakis typically infect the stomach of cetaceans worldwide, often causing ulcerative lesions that may compromise the host's health. These nematodes also cause anisakiasis or allergic reactions in humans. To assess the risks of this emerging zoonosis, data on long-term changes in Anisakis infections in cetaceans are necessary. Here, we compare the prevalence and severity of ulcerative lesions caused by Anisakis spp. in five cetacean species stranded along the north-west Spanish coast in 2017-2018 with published data from 1991-1996. Open ulcers were found in 32/43 short-beaked common dolphins, Delphinus delphis; 3/5 striped dolphins, Stenella coeruleoalba; 1/7 bottlenose dolphins, Tursiops truncatus; and 1/3 harbour porpoises, Phocoena phocoena meridionalis; a single individual of long-finned pilot whale, Globicephala melas, was found uninfected. In common dolphins, the mean abundance of open ulcers per host was 1.1 (95% confidence interval: 0.8-1.3), with a maximum diameter (mean ± standard deviation) of 25.4 ± 16.9 mm. Stomachs with scars or extensive fibrosis putatively associated with Anisakis were detected in 14 and five animals, respectively. A molecular analysis based on the mitochondrial cytochrome c oxidase II gene using 18 worms from three cetacean species revealed single or mixed infections of Anisakis simplex sensu stricto and Anisakis pegreffii. Compared with the period 1991-1996, we found a strong increase of prevalence, abundance and extension of ulcerative lesions in most cetacean species. Anisakis populations could have increased in the study area over the last decades, although we cannot rule out that a higher environmental stress has also boosted the pathological effects of these parasites.

Validation of a Commercial Loop-Mediated Isothermal Amplification (LAMP) Assay for the Rapid Detection of Anisakis spp. DNA in Processed Fish Products

Parasites belonging to the Anisakis genera are organisms of interest for human health because they are responsible for the Anisakiasis zoonosis, caused by the ingestion of raw or undercooked fish. Furthermore, several authors have reported this parasite to be a relevant inducer of acute or chronic allergic diseases. In this work, a rapid commercial system based on Loop-Mediated Isothermal Amplification (LAMP) was optimised and validated for the sensitive and rapid detection of Anisakis spp. DNA in processed fish products. The specificity and sensitivity of the LAMP assay for processed fish samples experimentally infected with Anisakis spp. larvae and DNA were determined. The LAMP system proposed in this study was able to give positive amplification for all the processed fish samples artificially contaminated with Anisakis spp., giving sensitivity values equal to 100%. Specificity tests provided no amplification for the Contracaecum, Pseudoterranova, or Hysterothylacium genera and uninfected samples. The limit of detection (LOD) of the LAMP assay proposed was 10² times lower than the real-time PCR method compared. To the best of our knowledge, this is the first report regarding the application of the LAMP assay for the detection of Anisakis spp. in processed fish products. The results obtained indicate that the LAMP assay validated in this work could be a reliable, easy-to-use, and convenient tool for the rapid detection of Anisakis DNA in fish product inspection.

The hidden companion of non-native fishes in north-east Atlantic waters

A tropicalization phenomenon of ichthyofauna has been described in the last decades in Galicia (north-eastern Atlantic), with increasing reports of tropical and subtropical fishes appearing northward this distribution range. A search for parasites was carried out in the digestive tract of two specimens first captured in Galician waters: the prickly puffer Ephippion guttifer (Tetraodontidae) and the African stripped grunt Parapristipoma octolineatum (Haemulidae). Examination of E. guttifer showed high intensity of nematodes, from three different genera: Cucullanus (Cucullanidae), Hysterothylacium (Raphidascaridae) and Anisakis (Anisakidae), with demonstrated pathogenicity to humans. Molecular identification allowed the identification of Anisakis pegreffii, already described in the area, and first reports for European waters of Cucullanus dodsworthi, Hysterothylacium reliquens and a new Hysterothylacium sp. P. octolineatum showed a far lower level of parasitization, with two Hysterothylacium larvae, genetically identified as Hysterothylacium deardorffoverstreetorum, also its first report in the eastern Atlantic. Thus, possible ecological impact of the occurrence of two non-native individual fishes in a new area could be remarkably higher if we see this issue through the lens of the parasitological perspective, as far as only two individual fish can harbour more of one hundred nematode parasites belonging to different species, most of them also new species for that area.

Epidemiological Scenario of Anisakidosis in Spain Based on Associated Hospitalizations: The Tip of the Iceberg

BACKGROUND

The risk of infection with Anisakis has been recognized for some time, but it is now emerging due to major awareness, better diagnostic techniques, and increasing preference for raw or lightly cooked food. Spain has the second-highest reported incidence after Japan, though the real anisakidosis burden is unknown because of the scarcity of epidemiological data. This study provides a 19-year review of anisakidosis-related hospitalizations describing epidemiological trends and patient characteristics.

METHODS

We performed a retrospective descriptive study using the Spanish Hospitalization Minimum Data Set from 1997 to 2015. Hospitalization rates were calculated and spatial distribution of cases and their temporal behavior were assessed. Clinical characteristics were described, including related codiagnoses and procedures.

RESULTS

A total of 2471 hospital discharges were identified. A continuous increasing trend was observed, with several peaks. Most affected communities were located in the northwest inland part of the country. Almost 54% of hospitalized patients were male, with a mean age of 51.3 years. Median length of stay was 5 days, and the hospitalization median cost around €2900. Fatal outcome occurred in 0.5%. Most frequent codiagnoses were digestive diseases, mainly intestinal obstruction. Urticaria, anaphylactic reaction, and angioneurotic edema were only recorded in 2.2%, 2.4%, and 1.2%, respectively.

CONCLUSIONS

Knowing that hospitalization is unusual in anisakidosis, we offer calculations of the real disease burden. Improving disease surveillance in parallel to disease control will be useful both in gaining extended disease knowledge and reducing morbidity and related costs.

Anisakis Nematodes in Fish and Shellfish- from infection to allergies

Anisakidosis is a zoonotic parasitosis induced by members of the family Anisakidae. The anisakid genera includes Anisakis, Pseudoterranova, Hysterothylacium and Contracaecum. The final definitive hosts of these nematodes are marine mammals with a complex life cycle. These nematode parasites use different crustaceans and fish species as intermediate or paratenic hosts and humans are accidental hosts. Human anisakiasis, the infections caused by members of the genus Anisakis, occurs, when seafoods, particularly fish, contaminated with the infective stage (third stage larvae [L3]) of this parasite, are consumed. Pseudoterranovosis, on the other hand is induced by members of the genus Pseudoterranova. These two genera of anisakids have been implicated in human disease globally. There is a rise in reports of gastro-intestinal infections accompanied by allergic reactions caused by Anisakis simplex and Anisakis pegreffii. This review provides an update on current knowledge on Anisakis as a food-borne parasite with special focus on the increasingly reported diversity of fish and crustacean hosts, allergens and immunological cross-reactivity with invertebrate proteins rendering this parasite a significant public health issue.

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Anisakis, is a foodborne zoonotic parasite.

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Humans are accidental hosts of Anisakis L3 larva.

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Consumption of Anisakis parasite-contaminated seafood causes human anisakiasis.

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Zooplankton (Crustaceans: Krills, Squids, Crayfish) composition in fishing regions contribute to Anisakis parasitosis.

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Anisakis is the parasite with the largest number of registered allergens with the IUIS.

Transcriptome and metabolome analyses of Coilia nasus in response to Anisakidae parasite infection

Parasites from the family Anisakidae are capable of infecting a range of marine fish species worldwide. Coilia nasus, which usually feeds and overwinters in coastal waters and spawns in freshwater, is highly susceptible to infection by Anisakidae. In this study, we used scanning electron microscopes to show that C. nasus infected by Anisakidae exhibited damage and fibrosis of the liver tissue. To better understand host immune reaction and metabolic changes to Anisakidae infection, we used a combination of transcriptomic and metabolomic method to characterize the key genes and metabolites, and the signaling pathway regulation of C. nasus infected by Anisakidae. We generated 62,604 unigenes from liver tissue and identified 391 compounds from serum. Of these, Anisakidae infection resulted in significant up-regulation of 545 genes and 28 metabolites, and significant down-regulation of 416 genes and 37 metabolites. Seventy-four of the 961 differentially expressed genes were linked to immune response, and 1, 2-Diacylglycerol, an important immune-related metabolite, was significantly up-regulated after infection. Our results show activation of antigen processing and presentation, initiation of the T cell receptor signaling pathway, disruption of the TCA cycle, and changes to the amino acid and Glycerolipid metabolisms, which indicate perturbations to the host immune system and metabolism following infection. This is the first study describing the immune responses and metabolic changes in C. nasus to Anisakidae infection, and thus improves our understanding of the interaction mechanisms between C. nasus and Anisakidae. Our findings will be useful for future research on the population ecology of C. nasus.

Prevalence and Risk of Anisakid Larvae in Fresh Fish Frequently Consumed in Spain: An Overview

Anisakidosis is a fish-borne zoonosis caused by parasitic nematodes of the family Anisakidae, of which the species belonging to Anisakis simplex complex are the most representative. It is considered an emerging disease in Spain. The objective of this study is to analyse the presence of larvae in fish frequently consumed in Spanish supermarkets, inferring the risk of infection. In total 1,786 specimens of 9 different fish species, from two geographical origins (Atlantic and Mediterranean), acquired fresh and not eviscerated were examined for anisakid nematodes. Analysis showed that 33.7% of the samples were parasitized by Anisakis larvae. The horse mackerel (Trachurus trachurus) presented the highest total prevalence (66.0%), followed by the silver hake (Merluccius bilinearis) (59.5%), the mackerel (Scomber scombrus) (58.4%), the blue whiting (Micromesistius poutassou) (53.9%) and the European hake (Merlucius merlucius) (45.0%). In general, the prevalence was higher in Atlantic than in Mediterranean fish. In all the species analysed, a higher presence of the parasite was detected in the viscera than in the flesh, although in the most parasitized species a noteworthy prevalence and abundance was observed in the flesh. In conclusion, risk factors, like fish species and origin, should be considered by consumers, in addition of following the recommendations established by Commission Regulation (EU) No1276/2011 and the Spanish Royal Decree 1420/2006.

Anisakiasis in Italy: Analysis of hospital discharge records in the years 2005-2015

Background

Anisakiasis is a fish-borne zoonosis caused by the ingestion of marine food infected with Anisakis third-stage larvae, widespread marine parasitic nematodes. Gastrointestinal and/or allergic clinical signs and symptoms are not specific. While frequently reported in countries with large raw fish consumption as Japan, the global prevalence of anisakiasis may be severely underestimated due to limitations of available diagnostic tools and to diverse clinical manifestations. Recently, infective larvae were found in the same localization with gastrointestinal tumors. The occurrence of allergic exacerbation upon secondary exposure and the possible occupational exposure, highlight the need to increase scientific evidences on anisakiasis.

Methods

We performed a retrospective descriptive study using analysis of Hospital Discharge Records (HDRs) from 2005 to 2015 in Italy, with particular attention to allergic manifestations. Descriptive statistics and multivariate analyses were performed using backward step-wise logistic regression models to assess spatial distribution and temporal trend as well as the variables independently associated with the allergic clinical signs and symptoms in Italian cases of anisakiasis.

Results

HDRs reporting the ICD-9 code for anisakiasis were retrieved (370), with a higher number of cases reported from central and southern regions, with particular regard to populations inhabiting the coastal territories. Around 40% of patients presented allergic manifestations and half of them showed serious allergic reactions. The multivariate analyses showed an independent association between allergic manifestations and features as living in southern regions and female gender, while anaphylactic episodes was independently associated only with female gender.

Conclusion

The present study is the first attempt to a better understanding of the epidemiological picture of anisakiasis in Italy, mining official data. A common strategy on data collection, monitoring and reporting would favor a more accurate epidemiological scenario in Italy, since the report of the diseases is not mandatory.

A Perspective Around Cephalopods and Their Parasites, and Suggestions on How to Increase Knowledge in the Field

Although interest in several areas of cephalopod research has emerged over the last decades (e.g., neurobiology, aquaculture, genetics, and welfare), especially following their 2010 inclusion in the EU Directive on the use of animals for experimental purposes, knowledge regarding the parasites of cephalopods is lacking. Cephalopods can be intermediate, paratenic, or definitive hosts to a range of parasites with a wide variety of life cycle strategies. Here, we briefly review the current knowledge in cephalopod parasitological research, summarizing the main parasite groups that affect these animals. We also emphasize some topics that, in our view, should be addressed in future research, including: (i) better understanding of life cycles and transmission pathways of common cephalopod parasites; (ii) improve knowledge of all phases of the life cycle (i.e., paralarvae, juveniles, adults and senescent animals) and on species from polar deep sea regions; (iii) exploration of the potential of using cephalopod-parasite specificity to assess population boundaries of both, hosts and parasites; (iv) risk evaluation of the potential of standard aquacultural practices to result in parasite outbreaks; (v) evaluation and description of the physiological and behavioral effects of parasites on their cephalopod hosts; (vi) standardization of the methods for accurate parasite sampling and identification; (vii) implementation of the latest molecular methods to facilitate and enable research in above mentioned areas; (viii) sharing of information and samples among researchers and aquaculturists. In our view, addressing these topics would allow us to better understand complex host-parasite interactions, yield insights into cephalopod life history, and help improve the rearing and welfare of these animals in captivity.

Ancient horizontally transferred genes in the genome of California two-spot octopus, Octopus bimaculoides

Horizontal gene transfer (HGT), a mechanism that shares genetic material between the host and donor from separated offspring branches, has been described as a means of producing novel and beneficial phenotypes for the host organisms. However, in molluscs, the second most diverse group, the existence of HGT is still controversial. In the present study, 12 HGT genes were identified from California two-spot octopus Octopus bimaculoides based on a similarity search, phylogenetic construction, gene composition analysis and PCR (Polymerase Chain Reaction) validation. Based on the phylogenetic topologies, ten HGT genes were identified to have been transferred into the possible molluscan ancestor, possibly before its radiation. Furthermore, most of the donor organisms were predicted to be familiar bacteria in marine environments. These horizontally transferred genes were under a strong negative selection and could be transcribed in octopus functionally. The predicted biochemical functions of these genes include metabolism, neurotransmission, immune defense and tissue integrity. Seven Zn-metalloproteinases were validated as the main type of HGT genes in octopus with divergent motif composition, intron presence and phylogenetic relationship to the endogenous ones. Furthermore, the functions of Zn-metalloproteinase were predicted to be responsible for immune defense and tissue remolding. Three HGT genes were distributed mainly in the nervous system and were predicted to regulate the neurotransmission through glia-neuronal interactions. The results collectively indicated the existence of HGT in molluscs and its potential contribution to the evolution of octopus with regards to functional innovation and adaptability.

Mesopredatory fishes from the subtropical upwelling region off NW-Africa characterised by their parasite fauna

Eastern boundary upwelling provides the conditions for high marine productivity in the Canary Current System off NW-Africa. Despite its considerable importance to fisheries, knowledge on this marine ecosystem is only limited. Here, parasites were used as indicators to gain insight into the host ecology and food web of two pelagic fish species, the commercially important species Trichiurus lepturus Linnaeus, 1758, and Nealotus tripes Johnson, 1865. Fish specimens of T. lepturus (n = 104) and N. tripes (n = 91), sampled from the Canary Current System off the Senegalese coast and Cape Verde Islands, were examined, collecting data on their biometrics, diet and parasitisation. In this study, the first parasitological data on N. tripes are presented. T. lepturus mainly preyed on small pelagic Crustacea and the diet of N. tripes was dominated by small mesopelagic Teleostei. Both host species were infested by mostly generalist parasites. The parasite fauna of T. lepturus consisted of at least nine different species belonging to six taxonomic groups, with a less diverse fauna of ectoparasites and cestodes in comparison to studies in other coastal ecosystems (Brazil Current and Kuriosho Current). The zoonotic nematode Anisakis pegreffii occurred in 23% of the samples and could pose a risk regarding food safety. The parasite fauna of N. tripes was composed of at least thirteen species from seven different taxonomic groups. Its most common parasites were digenean ovigerous metacercariae, larval cestodes and a monogenean species (Diclidophoridae). The observed patterns of parasitisation in both host species indicate their trophic relationships and are typical for mesopredators from the subtropical epi- and mesopelagic. The parasite fauna, containing few dominant species with a high abundance, represents the typical species composition of an eastern boundary upwelling ecosystem.

Molecular Epidemiology of Anisakis and Anisakiasis: An Ecological and Evolutionary Road Map

This review addresses the biodiversity, biology, distribution, ecology, epidemiology, and consumer health significance of the so far known species of Anisakis, both in their natural hosts and in human accidental host populations, worldwide. These key aspects of the Anisakis species' biology are highlighted, since we consider them as main driving forces behind which most of the research in this field has been carried out over the past decade. From a public health perspective, the human disease caused by Anisakis species (anisakiasis) appears to be considerably underreported and underestimated in many countries or regions around the globe. Indeed, when considering the importance of marine fish species as part of the everyday diet in many coastal communities around the globe, there still exist significant knowledge gaps as to local epidemiological and ecological drivers of the transmission of Anisakis spp. to humans. We further identify some key knowledge gaps related to Anisakis species epidemiology in both natural and accidental hosts, to be filled in light of new 'omic' technologies yet to be fully developed. Moreover, we suggest that future Anisakis research takes a 'holistic' approach by integrating genetic, ecological, immunobiological, and environmental factors, thus allowing proper assessment of the epidemiology of Anisakis spp. in their natural hosts, in human populations, and in the marine ecosystem, in both space and time.

Liver of the fish Gymnotus inaequilabiatus and nematode larvae infection: Histochemical features and expression of proliferative cell nuclear antigen

Histopathological lesions due to third-larval stage of nematode Brevimulticaecum sp. within the liver of a subpopulation of 31 Gymnotus inaequilabiatus from the Pantanal Region (Brazil) were studied with histochemical and immunohistochemical methods. In 93.5% of fish, livers harboured nematode larvae and the intensity of infection ranged from 8 to 293. In livers with highest number of larvae, the hepatic tissue was occupied primarily by the nematodes. Each larva was encircled by focal inflammatory granulomatous reaction. Within the thickness of the granuloma, three concentric layers were recognized: an inner layer of densely packed epithelioid cells, a middle layer of mast cells (MCs) entrapped in a thin fibroblast-connective mesh and an outer layer of fibrous connective tissue with fibroblasts. Epithelioid cells and fibroblasts within the thickness of the granuloma wall were positive for proliferative cell nuclear antigen (PCNA). Moreover, several hepatocytes in infected liver were immunoreactive to PCNA. Occurrence of rodlet cells and MCs in parenchyma, in close proximity to the encysted nematode larvae and near the blood vessel of infected liver, was observed. Macrophage aggregates (MAs) were numerous within the granulomas and scattered in parenchyma of the infected liver. High quantity of haemosiderin was encountered in MAs and hepatocytes of infected liver.

Ecological role of bluefin tuna (Thunnus thynnus) fish farms for associated wild fish assemblages in the Mediterranean Sea

The ecological effects of tuna fish farms are largely undocumented. This study confirmed their high capacity to attract surrounding wild fish. The aggregation effect persisted year round, without detectable seasonal differences. Farm impact was restricted to close proximity of the sea cages, and was more prominent over the bottom than in the water column strata. Tuna fish farms proved to be high energy trophic resources, as indicated by the enhanced fitness status of two focal species, bogue and seabream. Under abundant food supply, seabream appear to allocate the majority of energy reserves to gonad development. Farm associated bogue had greater parasite loads, with no detrimental effect on fitness status. Overall, tuna fish farms can be regarded as population sources for aggregated wild fish, and under the no fishing conditions within the leasehold areas, can serve as functional marine protected areas.

Anisakis - immunology of a foodborne parasitosis

Anisakis species are marine nematodes which can cause zoonotic infection in humans if consumed in raw, pickled or undercooked fish and seafood. Infection with Anisakis is associated with abdominal pain, nausea and diarrhoea and can lead to massive infiltration of eosinophils and formation of granulomas in the gastrointestinal tract if the larvae are not removed. Re-infection leads to systemic allergic reactions such as urticarial or anaphylaxis in some individuals, making Anisakis an important source of hidden allergens in seafood. This review summarizes the immunopathology associated with Anisakis infection. Anisakiasis and gastroallergic reactions can be prevented by consuming only fish that has been frozen to -20°C to the core for at least 24 hours before preparation. Sensitization to Anisakis proteins can also occur, primarily due to occupational exposure to infested fish, and can lead to dermatitis, rhinoconjunctivitis or asthma. In this case, exposure to fish should be avoided.

Validation of a commercial kit aimed to the detection of pathogenic anisakid nematodes in fish products

Anisakids are parasitic nematodes responsible for a zoonosis that occurs following the ingestion of fish and fish products infected with larvae belonging to the genera Anisakis and Pseudoterranova. Rarely Contracaecum is found in association with gastric/intestinal illness, while Hysterothylacium is commonly considered not pathogenic. Although Real Time PCR assays have been recently used with the aim to detect and quantify these parasites in food products, methods applied did not undergo through extensive validation process, a feature highly desirable or mandatory in the case of testing laboratories accredited for the ISO EN 17025:2005. Here, a comprehensive study has been performed to validate a commercial kit based on multiplex real time PCR for the qualitative detection of Anisakis and Pseudoterranova. Inclusivity/exclusivity trials were carried out on DNA from species of the genera Anisakis, Pseudoterranova, Contracaecum, Hysterothylacium and Ascaris, on fish intentionally contaminated with Anisakis spp. and Pseudoterranova spp. and on marine organisms as fish, crustacean and squid to test the commercial kit on a large sample. The assay gave positive amplification for several Anisakis and Pseudoterranova species, while providing no signal for the members of the remaining genera. Each sample was correctly assigned either to Anisakis or Pseudoterranova, thus indicating that no cross-reaction occurred. The LOD was determined using two independent standard curves. Robustness was assayed by using two different thermocyclers in three distinct laboratories with different operators. The establishment of a validation dossier will permit the use of the commercial kit for the detection of Anisakis and Pseudoterranova DNA in fish and fish products intended for human consumption by public or private laboratories, following the requirements regarding the quality assurance processes described in the ISO EN 17025:2005.

No more time to stay 'single' in the detection of Anisakis pegreffii, A. simplex (s. s.) and hybridization events between them: a multi-marker nuclear genotyping approach

A multi-marker nuclear genotyping approach was performed on larval and adult specimens of Anisakis spp. (N = 689) collected from fish and cetaceans in allopatric and sympatric areas of the two species Anisakis pegreffii and Anisakis simplex (s. s.), in order to: (1) identify specimens belonging to the parental taxa by using nuclear markers (allozymes loci) and sequence analysis of a new diagnostic nuclear DNA locus (i.e. partial sequence of the EF1 α-1 nDNA region) and (2) recognize hybrid categories. According to the Bayesian clustering algorithms, based on those markers, most of the individuals (N = 678) were identified as the parental species [i.e. A. pegreffii or A. simplex (s. s.)], whereas a smaller portion (N = 11) were recognized as F1 hybrids. Discordant results were obtained when using the polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLPs) of the internal transcribed spacer (ITS) ribosomal DNA (rDNA) on the same specimens, which indicated the occurrence of a large number of 'hybrids' both in sympatry and allopatry. These findings raise the question of possible misidentification of specimens belonging to the two parental Anisakis and their hybrid categories derived from the application of that single marker (i.e. PCR-RFLPs analysis of the ITS of rDNA). Finally, Bayesian clustering, using allozymes and EF1 α-1 nDNA markers, has demonstrated that hybridization between A. pegreffii and A. simplex (s. s.) is a contemporary phenomenon in sympatric areas, while no introgressive hybridization takes place between the two species.