Prevalence of Anisakis spp. and Hysterothylacium spp. larvae in teleosts and cephalopods sampled from waters off Sardinia

Fish feed composition by high-throughput sequencing analysis: Parasite risk assessment

The use of wild small fish species as feed for aquaculture has clearly an economic incentive by speeding the growth of farmed species. Since feed ingredients are sourced from wild fisheries the farmed species could contain natural contaminants which may introduce food safety concerns. In this study, we used High-Throughput Sequencing (HTS) to explore the whole DNA profile of ten dry commercial feeds commonly used by Spanish fish farming companies. The feeds were mainly made of species within the genus Sprattus, Ammodytes and Clupea, and vegetables of the genus Triticum. In the feeds, DNA sequences of parasitic nematodes of fishes (˂1 % total OTUs) were also identified. A taxonomic assignment of query sequences, using a phylogeny-based approach, estimation of pairwise nucleotide identities within and between sequence groups and haplotype network analysis, allow assign short query sequences to the species Phocanema krabbei (Anisakidae) and Hysterothylacium aduncum (Rhaphidascarididae). Both species were identified as ingredient in two and six fish feeds, respectively. This result is of highly concern regarding dietetic recommendations to sensitized patients to anisakids, considering the growing evidence on the possible allergenic potential of both genera, and the recent data on the transfer of anisakid heat-resistant allergens from fishmeal to farm and aquaculture animals.

A critical review of anisakidosis cases occurring globally

A review was conducted to identify the most common causative agents of anisakidosis, the methods used for identification of the causative agents, and to summarize the sources of infection, and patients' demographics. A total of 762 cases (409 articles, inclusive of all languages) were found between 1965 and 2022. The age range was 7 months to 85 years old. Out of the 34 countries, Japan, Spain, and South Korea stood out with the highest number of published human cases of anisakidosis, respectively. This raises the question: Why are there few to no reports of anisakidosis cases in other countries, such as Indonesia and Vietnam, where seafood consumption is notably high? Other than the gastrointestinal tract, parasites were frequently found in internal organs such as liver, spleen, pancreas, lung, hiatal and epigastric hernia, and tonsils. There are also reports of the worm being excreted through the nose, rectum, and mouth. Symptoms included sore throat, tumor, bleeding, gastric/epigastric/abdominal/substernal/lower back/testicular pain, nausea, anorexia, vomiting, diarrhea, constipation, intestinal obstruction, intussusception, blood in feces, hematochezia, anemia, and respiratory arrest. These appeared either immediately or up to 2 months after consuming raw/undercooked seafood and lasting up to 10 years. Anisakidosis commonly mimicked symptoms of cancer, pancreatitis, type I/II Kounis syndrome, intussusception, Crohn's disease, ovarian cysts, intestinal endometriosis, epigastralgia, gastritis, gastroesophageal reflux disease, hernia, intestinal obstruction, peritonitis, and appendicitis. In these cases, it was only after surgery that it was found these symptoms/conditions were caused by anisakids. A range of not only mainly marine but also freshwater fish/shellfish were reported as source of infection. There were several reports of infection with >1 nematode (up to >200), more than one species of anisakids in the same patient, and the presence of L4/adult nematodes. The severity of symptoms did not relate to the number of parasites. The number of anisakidosis cases is grossly underestimated globally. Using erroneous taxonomic terms, assumptions, and identifying the parasite as Anisakis (based solely on the Y-shaped lateral cord in crossed section of the parasite) are still common. The Y-shaped lateral cord is not unique to Anisakis spp. Acquiring a history of ingesting raw/undercooked fish/seafood can be a clue to the diagnosis of the condition. This review emphasizes the following key points: insufficient awareness of fish parasites among medical professionals, seafood handlers, and policy makers; limited availability of effective diagnostic methodologies; and inadequate clinical information for optimizing the management of anisakidosis in numerous regions worldwide.

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.

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.

Morphological and molecular identification of Hysterothylacium larvae (Nematoda: Raphidascarididae) in marine fish from Tunisian Mediterranean coasts

The taxonomy of Hysterothylacium genus in Mediterranean waters remains incomplete and unresolved. The aim of the current study was to investigate the morphological and molecular identification of selected species of Hysterothylacium larvae in marine fish from the Tunisian Mediterranean coasts. A total of 192 marine fish samples were examined. In total, thirty-seven third-stage larvae of Hysterothylacium were morphologically identified as Hysterothylacium type V. In the present study, representatives of this type from the Mediterranean Sea were genetically characterized for the first time by sequencing the rDNA ITS (ITS1-5.8S-ITS2) regions and mtDNA cox2 gene. This study represents the first report of Hysterothylacium type V from the Mediterranean Sea. We also report Mullus barbatus, M. surmuletus, and Pagellus erythrinus as new hosts for this larval type. Based upon molecular and phylogenetic analyses considering the rDNA ITS regions, the Hysterothylacium type V described here was classified as a new genotype, named Genotype B. The valid genetic data of the described Hysterothylacium type V in the present study can be used to establish the phylogenetic relationships among Hysterothylacium species from the Mediterranean Sea and worldwide for future research.

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.

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.

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

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

Occurrence of larval ascaridoid nematodes in the Argentinean short-finned squid Illex argentinus from the Southwest Atlantic Ocean (off Falkland Islands)

The Argentinean short-finned squid (Illex argentinus) is an oceanic, neritic species widely distributed off the east coast of South America, representing the most abundant commercially exploited squid species in these waters. Despite the great commercial importance of Argentinean short-finned squid as a food resource, and as frozen product exported to Europe, the presence of zoonotic anisakid nematodes, especially in the mantle of the squid, is poorly known. The occurrence and site of infection of larval ascaridoid nematodes in 70 I. argentinus caught off the Falkland Islands were investigated. Squids were examined using the UV-Press method. In total, 30 nematodes were detected in the viscera and mantle. According to morphology, 27 were third-stage larvae (L₃) belonging to genus Anisakis, while three were L₃ assigned to Hysterothylacium. Anisakis pegreffii (n = 27) were identified by sequence analysis of the mtDNA cox2 and the partial EF1 α-1 region of nDNA genes; Hysterothylacium aduncum (N = 3) were identified by sequence analysis of the ITS rDNA region. These findings represent the first molecular identification of A. pegreffii and H. aduncum in I. argentinus. Both prevalence (P = 15.7%) and abundance (A = 0.39) of infection with A. pegreffii were low, and even lower values of infection were recorded for H. aduncum (P = 2.1%, A = 0.04). Only 3 out of 70 (4.3%) squids hosted A. pegreffii larvae in the mantle. Larvae infecting viscera were coiled and mainly attached to outer surface of visceral organs. Mantle-infecting larvae were situated in the posterior half. Thus, these results suggest that - although low - the risk of acquiring anisakiasis from consumption of raw, marinated and/or undercooked short-finned squid products still exists.

Prevalence of anisakid parasites in fish collected from Apulia region (Italy) and quantification of nematode larvae in flesh

Anisakis spp. and Hysterothylacium spp. are nematodes that commonly parasitize several fish species. Nematode larvae can be recovered in coelomic cavity and viscera, but also in flesh and have an important economic and public health impact. A total of 1144 subjects of wild teleosts, 340 samples of cephalopods and 128 specimens of farmed fish collected from Apulia region were analysed for anisakid larvae detection by visual inspection of coelomic cavity and viscera and by digestion of the flesh. No nematode larvae were found in farmed fish and cephalopod molluscs. All examined wild-caught fish species were parasitized, except for 5 species for each of which only a few subjects belonging to the same batch were sampled, therefore the results are just indicative. A total of 6153 larvae were isolated; among these, 271 larvae were found in the muscular portion. Larvae were identified by morphological method as belonging to the genera Anisakis (97.2%) (type I and type II) and Hysterothylacium (2.8%). Both nematodes could be found in all fish species, except for round sardinella (Sardinella aurita), infected only by Hysterothylacium spp. and for Mediterranean scaldfish (Arnoglossus laterna), little tunny (Euthynnus alleteratus) and chub mackerel (Scomber japonicus) infected only with Anisakis spp.. A sample of 185 larvae was sent to the National Reference Centre for Anisakiasis (C.Re.N.A.) of Sicily for identification at the species level: 180 larvae belonged to the species A. pegreffii and 2 larvae to A. physeteris. The remaining 3 larvae were identified at genus level as Hysterothylacium. Statistical indices such as prevalence, mean intensity and mean abundance were calculated. Chub mackerel (S. japonicus) was the species with the highest prevalence and mean intensity. Moreover, the average and the median values of larvae per 100 g of edible part for each fish species were determined to estimate the consumer exposure to Anisakis spp.. The obtained values were then recalculated by referring to the edible part of all specimens (infected and non-infected) forming a single parasitized batch, getting more realistic and objective data useful for risk assessment. Our results indicate that the consumption of raw or undercooked wild fish caught off Apulian coasts could result in the acquisition of anisakiasis; on the contrary, farmed fish and cephalopods appear to be safer for the consumer.

Occurrence of Anisakis and Hysterothylacium larvae in commercial fish from Balearic Sea (Western Mediterranean Sea)

This study investigates the occurrence of anisakids and raphidascarids in commercial fish from Balearic Sea (Western Mediterranean). A total of 335 fish including 19 black anglerfish (Lophius budegassa), 33 white anglerfish (L. piscatorius), 129 European hake (Merluccius merluccius), 30 red mullet (Mullus barbatus), and 124 striped mullet (M. surmuletus) were examined using enzymatic digestion. A total of 948 nematode larvae were isolated (prevalence 52.53%) being the highest prevalence observed in striped mullet. Forty-six larvae were identified using molecular analyses which included PCR and sequencing of the 629-bp fragment of mitochondrial cox2 gene region. Anisakis pegreffii (80.43%), A. physeteris (8.69%), Hysterothylacium fabri (6.52%), and A. simplex (4.35%) were detected based on molecular analyses of larvae. Total nematode prevalence was positively correlated with weight, length, condition factor, and maturity stage of the host and also with fishing ground depth. Statistical differences between total nematode prevalence and geographical sector of capture were observed when fishing hauls were grouped according to the abundance of sperm whales or common bottlenose dolphins. The results also corroborate that fishing water depth may play an important role in anisakid and raphidascarid parasitization.

Helminth parasites of the dwarf sperm whale Kogia sima (Cetacea: Kogiidae) from the Mediterranean Sea, with implications on host ecology

Limited data exist on the occurrence of the dwarf sperm whale Kogia sima in the Mediterranean Sea and its parasite fauna. Here, the occurrence of the anisakid species Anisakis physeteris and A. pegreffii in the stomach chambers of an adult female dwarf sperm whale, stranded in southern Italy, is reported. In addition, the occurrence of Phyllobothrium delphini larvae infecting the blubber of the caudal peduncle region was recorded. A. physeteris and A. pegreffii represent the 2 parasite species of the genus, mostly distributed in the Mediterranean Sea in fish and squids. The finding of A. pegreffii and A. physeteris in the dwarf sperm whale represents a new record in this host species for the Mediterranean Sea. The study of gastrointestinal content also revealed a massive presence of cephalopod beaks identified as belonging to pelagic squids including the umbrella squid Histioteuthis bonnellii, the reverse jewel squid H. reversa, the long-armed squid Chiroteuthis veranii, and the comb-finned squid Ctenopteryx sicula. The feeding habits of the dwarf sperm whale, as well as the occurrence of these squid residuals in the cetacean host, suggest that these squid species play a major role in maintaining the life cycle of anisakid parasite species and P. delphini.

Human anisakiasis in Italy: a retrospective epidemiological study over two decades

A retrospective analysis on human anisakiasis in Italy since its first description in 1996 was performed by conducting a literature search. Inclusion criteria based on the presence of a larva and on parasite identification were applied. Epidemiological data and clinical features were analysed. Particular attention was paid to the source of infection. In total, 73 cases were included in the analysis, while 34 were excluded. Cases were reported from eight Italian regions, most frequently Abruzzo, Apulia and Latium. The parasite was detected by endoscopy (51.4%) or laparotomy (48.6%). The site of infection was intestinal (42.5%), gastric (43.8%), oesophageal (1.4%) or ectopic (12.3%). Most of the parasites (71.0%) were identified as Anisakis sp. or A. simplex (s.l.). However, when molecular methods were used (21 cases), A. pegreffii was always identified. In most of the patients (65.7%), the source of infection was raw or undercooked anchovies, followed by "anchovies or sardines" (15.1%), generic "raw seafood" (15.1%), and sardines (1.4%). In only 2 cases (2.7%), the source was not available. This is the first systematic analysis of Italian cases of anisakiasis. The main conclusions derived from the results are: i) attention should be given to the history, in particular when raw marinated anchovies, proven to be the main source of human anisakiasis in Italy, are consumed; ii) in order to assess correct epidemiological data, a confirmed and specific etiological identification should always be sought.

Geographic and host size variations as indicators of Anisakis pegreffii infection in European pilchard (Sardina pilchardus) from the Mediterranean Sea: Food safety implications

European pilchards are traditionally eaten marinated or salted in the Mediterranean countries often without thermal processing or gutting due to small size. Since ingestion of live third stage Anisakis larvae represents a causing agent in the onset of anisakiasis, the aim of our study was to assess prevalence and intensity of Anisakis infection in European pilchards originating from different Mediterranean regions in a three-year sampling period (2013-2015). A total of 1564 specimens of European pilchard collected from two geographically distinct sampling regions (western Mediterranean and Adriatic Sea) were examined using the UV-Press method, which utilises the fluorescence of frozen anisakids in flattened and subsequently frozen fillets and viscera. A subsample of 67 isolated larvae was identified as A. pegreffii by diagnostic allozyme markers and sequence analyses of the mtDNA cox2 locus. The overall prevalence in pilchards was 12.2% (range 0-44.9% for different sampling points) and mean intensity 1.8. More importantly, we have observed an overall larval prevalence of 1.5% in fillets. The highest prevalence (44.9%) was recorded in pilchards caught in western parts of the Mediterranean. As fish host size was a significant predictor of parasite abundance, it should be highlighted that these pilchards were also the largest (mean total length 173.2mm); on average >2cm larger than the rest of the samples. Other isolated nematode species included Hysterothylacium sp. in viscera, showing almost a double of A. pegreffii prevalence, 20.1%. In summary, our study demonstrates that the presence of A. pegreffii in European pilchards from the Mediterranean Sea is highly influenced by both geographic and host size variation. This implies that, before future risk management measures are developed, these variables should be assessed in order to minimize public health concerns.

Prevalence and Mean Intensity of Anisakidae Parasite in Seafood Caught in the Mediterranean Sea Focusing on Fish Species at Risk of Being Raw-consumed. A Meta Analysis and Systematic Review

OBJECTIVE

To assess the prevalence and mean intensity of anisakids in seafood caught in the Mediterranean Sea, focusing on fish species at risk of being raw-consumed.

DESIGN

Systematic review and meta-analysis of studies published from 1960-2012.

STUDY SELECTION

Main criteria for the inclusion of studies were as follows: Findings of anisakid larvae, in both muscles and viscera; fish species for human consumption caught in the Mediterranean Sea; prevalence and mean intensity data for each species; and sample size equal to or more than 40 fishes.

RESULTS

Twelve studies were identified. Among these, four studies considered the following three fish species that are often consumed raw or preserved lightly, or not cooked thoroughly: anchovy, pilchard, and Atlantic mackerel.

DATA SYNTHESIS

All pooled analyses were based on the random-effect model. Anisakids prevalence in fish muscle was 0.64% (P < 0.0001), in viscera it was 1.34% (P < 0.0001), and overall prevalence was 0.95% (P < 0.0001). Mean intensity in muscle was 2.31 (P = 0.0083), in viscera it was 1.55 (P = 0.0174), and overall it was 1.81 (P < 0.0005). Heterogeneity indices (I(2)) were significantly high with the exception of viscera mean intensity.

CONCLUSIONS

Anchovy, pilchard, and Atlantic mackerel have a low prevalence and mean intensity of anisakidae larvae in both viscera and muscles. Mean Intensity was also low.

Molecular identification of Anisakis and Hysterothylacium larvae in commercial cephalopods from the Spanish Mediterranean coast

This study aims to investigate the occurrence of nematode larvae in commercial cephalopods in the Western Mediterranean Sea. A total of 202 animals comprising 123 broadtail shortfin squid (Illex coindetii), 34 European squid (Loligo vulgaris) and 45 common octopus (Octopus vulgaris) were examined using enzymatic digestion. A total of 31 larvae were isolated (prevalence: 14.6%) and identified using molecular analyses which included PCR and sequencing of the ITS (ITS1-5.8S rDNA-ITS2) region. Phylogenetic tree inferred from ITS sequences yielded supported relationships for Anisakis (P: 12.2%) and Hysterothylacium species (P: 4.1%). All parasites were found parasitizing I. coindetii and, as expected, A. pegreffii presented the highest prevalence (11.4%). A. physeteris was also found with a lower prevalence (1.6%) but confirming the role of the broadtail shortfin squid as paratenic host and, its potential host for anisakidosis transmission. A hybrid larva between Anisakis simplex and A. pegreffi was also identified. All Anisakis larvae were found within the visceral cavity; in contrast most of the Hysterothylacium larvae were isolated from the mantle. A significant correlation was found between total nematode prevalence and depth, explained by the presence of larger broadtail shortfin squids inhabiting deeper depths. Therefore, the results obtained in the present study improve the knowledge of the occurrence of Anisakis and Hysterothylacium species in the I. coindetii from the Spanish Mediterranean Sea highlighting the importance of considering I. coindetii as a potential hazard for humans if it is consumed raw or not well cooked and the need of further research in other cephalopods.

Petromyzon marinus (Petromyzontidae), an unusual host for helminth parasites in western Europe

The sea lamprey Petromyzon marinus, which is among the most phylogenetically ancient vertebrates, is a hematophagous ectoparasite that feeds on vertebrates and is considered vulnerable in Europe but is a pest in the North American Great Lakes. We conducted a literature review of helminth parasites of P. marinus and investigated postmetamorphic lampreys sampled in rivers and northeast Atlantic coastal waters (western France) during spawning migration. Based on the literature review, 16 helminth taxa have been recorded in P. marinus, among them 14 in North America but only 2 in Europe, with no species in common between these areas. Specific parasites are lacking, and helminth parasites recorded in P. marinus are mostly opportunistic and are trophically transmitted to fish hosts with both extremely low prevalence and mean intensity. Thus, P. marinus seems an unusual host that is probably infected through accidental ingestion of parasites by microphagous larvae (ammocoetes) and/or hematophagous postmetamorphs. Our field study supports this hypothesis, since only a single third-stage larva of Anisakis simplex sensu stricto was found in 2 postmetamorphic P. marinus among the 115 individuals dissected. This opportunistic, trophically transmitted, and cosmopolitan nematode species has never been recorded in North American sea lampreys and only once in Galician rivers (southern Europe). Infestation pathways of P. marinus by A. simplex are proposed vis-à-vis the feeding strategy of postmetamorphs and fish host species which potentially harbor anisakid larvae in their musculature. More generally, the complexity of biotic interactions is discussed considering P. marinus both as a host for helminth parasites and as a parasite for hosts such as fish and mammals, which are also potential predators of sea lamprey.

Fishing area and fish size as risk factors of Anisakis infection in sardines (Sardina pilchardus) from Iberian waters, southwestern Europe

The sardine (Sardina pilchardus) is a fish commonly consumed and appreciated in many countries, although they are more likely to be eaten fresh in western Mediterranean countries such as Spain, Portugal, France or Italy. A molecular epidemiological survey of sardines from 5 fishing areas of the Spanish Mediterranean (Málaga, southern Spain) and Atlantic coasts (southern: Cádiz and Isla Cristina; northern: A Coruña and Ondarroa) was carried out to determine the presence of Anisakis spp. larvae. The highest prevalence of these larvae was observed in fish from A Coruña (28.3%), followed by Ondarroa (5%) and Cádiz (2.5%). No Anisakis larvae were found in fish from Málaga and Isla Cristina. Three Anisakis genotypes were identified: Anisakis simplex sensu stricto, Anisakis pegreffii and a hybrid genotype between these two species. A. pegreffii was the most prevalent species in A Coruña (71% of larvae). Only three Anisakis larvae (9% collected larvae) were located in the musculature of sardines: two were identified as A. pegreffii while the other was a hybrid genotype. Sardine infection was associated with fishing area and fish length/weight (length and weight were strongly correlated; Pearson's correlation 0.82; p<0.001). Risk factor multivariate analysis showed that the risk of infection increases 1.6 times for every additional cm in the length of the sardines from the same fishing area. Comparison of fish of equal length showed that in sardines from A Coruña the risk of parasitization is 11.5 times higher than in those from other fishing areas. Although the risk of infection by Anisakis through consumption of sardines is generally low due to the low epidemiological parameter values (prevalence 10%, mean intensity 1.7 (range 1-5) and mean abundance 0.17), as larger fish are more heavily parasitized, there is an increased risk of infection by Anisakis through consumption of large sardines which are raw or have undergone insufficient treatment (undercooked, smoked, marinated, salted, pickled, freezing,…).

Food safety considerations in relation to Anisakis pegreffii in anchovies (Engraulis encrasicolus) and sardines (Sardina pilchardus) fished off the Ligurian Coast (Cinque Terre National Park, NW Mediterranean)

Engraulis encrasicolus and Sardina pilchardus are pelagic fishes of notable economic and gastronomic importance in the northwest Mediterranean (Ligurian Sea, Italy). The consumption of thermally unprocessed or lightly processed, marinated or salted anchovies and sardines presents a potential risk to acquire anisakiasis, a fish-borne parasitic disease in humans. Prevalence and abundance of Anisakis larvae in Engraulis encrasicolus and Sardina pilchardus from the Monterosso fishing grounds (Cinque Terre National Park, Ligurian Sea, Italy) were assessed, and the larvae were identified by morphological and PCR-RFLP methods. Anisakis larvae, all belonging to Anisakis pegreffii spp. were found in the visceral mass of 1050 anchovies (0.8% overall prevalence), whereas no Anisakis larvae were found in the 750 sardines examined. According to these data, the risk of acquiring anisakiasis from the consumption of raw or undercooked anchovies and sardines caught in the fishing area we investigated is very low.

Evolution of the Anisakis risk management in the European and Italian context

Due to the social and legislative implications, the presence of Anisakis spp. larvae in fishery products has become a concern for both the consumers and the official Control Authorities. The issuance of a large number of provisions, aimed at better managing fish products intended to be consumed raw or almost raw and the associated risks, resulted in a very complicate legal framework. In this work, we analyzed the evolution of the normative through an overview on the local and international legislations, focusing on issues that are of practical interest for Food Business Operators (FBOs) in the fishery chain. In addition, we performed a survey across the Department of Prevention of the Italian Local Health Authorities (LHA) and the main fish markets in Italy to collect the operating procedures and the monitoring plans. Overall, we found many differences, due to the absence of a national reference standard for the management of the Anisakis risk. From this examination, it turns clear that only a participation of all the involved institutions, a strategy of synergistic interventions, as well as a correct training of FBOs, can result in an effective risk management and a proper risk communication, which should overcome states of confusion and unnecessary negative impacts on the economy.

Molecular and epidemiological data on Anisakis spp. (Nematoda: Anisakidae) in commercial fish caught off northern Sardinia (western Mediterranean Sea)

Anisakiasis is a fish-borne zoonosis caused by third stage larvae of the nematode Anisakis sp. present in fish or cephalopods. This is the first contribution to the molecular identification and epidemiology of Anisakis spp. in commercial fish from the Gulf of Asinara (Sardinia, western Mediterranean Sea). Between April 2006 to November 2011, 777 specimens of 10 fish species (Engraulis encrasicolus, Merluccius merluccius, Micromesistius poutassou, Phycis blennoides, Sardina pilchardus, Sardinella aurita, Scomber colias, Sphyraena viridensis, Trachurus mediterraneus, Trachurus trachurus) were examined for Anisakis sp. larvae. A total of 1286 larvae were found in 218 fish. The great majority of larvae were located in the body cavity, and only a small part (60, 4.7%) in the muscle. All the Type I larvae (1272) were identified as Anisakis pegreffii and all the Type II (14) as Anisakis physeteris, confirming that A. pegreffii is the dominant species and the most important agent of human anisakiasis in the western Mediterranean Sea.

Molecular identification of Anisakis species (Nematoda: Anisakidae) from marine fishes collected in Turkish waters

Anisakid nematodes are important etiological agents for zoonotic human anisakiasis (or anisakidosis). These parasites in the Turkish waters still remain unexplored. This study aims the molecular identification of Anisakis species in Turkey's coast from Black, Aegean and Mediterranean Sea and specifically to screen for zoonotic species in commonly commercialized a total of 1145 fish belonging to 31 different species using both polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) and sequencing of the ribosomal internal transcribed spacer (ITS) regions and the mitochondrial cytochrome C oxidase subunit II (cox2) gene. A total of 776 Anisakis type I larvae were isolated in 56/1145 (4.8%) fish of 7 species from Turkish waters. The combining all of our results, e.g., morphology, PCR-RFLP, ITS region, and the cox2 gene, conclusively supported the identification of 3 Anisakis spp. taken from marine fish hosts, namely Anisakis pegreffii, Anisakis typica and Anisakis simplex sensu stricto (s.str.)/A. pegreffii hybrid genotype. No Anisakis larvae were isolated from the Black Sea whereas A. pegreffii, A. typica and A. simplex s.str./A. pegreffii hybrid genotype was found in the Aegean Sea and A. pegreffii was only isolated from the Mediterranean Sea. This study represents the first identification of A. typica and A. simplex s.str./A. pegreffii hybrid genotypes from Turkish waters. Moreover, in the present study first record of the presence of A. pegreffii is also reported from Turkish coasts of Aegean and Mediterranean Sea. No zoonotic Anisakis species were found in commonly commercialized 1025 fish belonging to 16 different species from the Black Sea, thus Turkish populations who consume captured fish from the Black Sea may have a less risk of human anisakiasis or allergies. However, the prevalence of larvae were 47.1% and 46% and recognized zoonotic A. pegreffii were identified from the Aegean and Mediterranean Sea coast, suggesting a high threat of anisakiasis or allergies for Turkish populations who consume fish originating in these regions.

Presence of anisakid larvae in the European anchovy, Engraulis encrasicolus, fished off the Tyrrhenian coast of central Italy

A survey was carried out to determine the prevalence of anisakid nematode larvae in European anchovy (Engraulis encrasicolus) fished off the Tyrrhenian coast of central Italy. From February through July 2012, 1,490 specimens of E. encrasicolus caught in three different fishing areas (off Civitavecchia, Anzio, and Gaeta in the northern, central, and southern Lazio region of Italy, respectively) were tested for the presence of anisakid larvae, both by visual microscopic inspection and enzymatic digestion. In each of the three fishing areas, each of two sampling times produced 250 fish (with the exception of one sampling time in Gaeta that produced 240 fish). Larvae of the family Anisakidae were detected with an overall estimated prevalence of 2.3%, and each positive fish harbored a single larva. No anisakid larvae were detected in fish caught off Gaeta. Fish with larvae were significantly longer (standard length) than fish without larvae. Twenty-six larvae (74.3%) were detected by visual inspection of the viscera, eight larvae (22.8%) were detected by visual inspection of the fillets, and one larva (2.8%) was detected after digestion of pooled fillets. Molecular analysis to fully characterize the 35 detected larvae revealed 15 specimens of Anisakis pegreffii, 10 specimens of Hysterothylacium aduncum, and one hybrid genotype of A. pegreffii × Anisakis simplex. For nine specimens, no visible product was obtained after PCR amplification. The overall prevalence for A. pegreffii and H. aduncum was 1.0 and 0.7%, respectively. A comparison between fishes harboring A. pegreffii larvae and those harboring H. aduncum revealed that those with A. pegreffii were significantly heavier. The prevalence of anisakid larvae found in the present study is lower then that reported previously in E. encrasicolus collected in the Mediterranean Sea.

Presence of Contracaecum spp. in teleosts cultured and fished in Sardinia

This study reports the results of the finding of Contracaecum spp. during a survey on endoparasites isolated from cultured and wild fish and also from some cephalopods caught in Sardinian waters. Contracaecum spp. is a nematode belonging to the Anisakidae, and is reported to cause zoonosis in humans. Nematodes were detected after visual inspection and enzymatic digestion and then identified by morphologic observation, which was confirmed by PCR. The results show that Contracaecum spp. were found in both fish caught from sea or lagoon, and in both cultured and wild fish: 33 of the parasitized samples were wild fish (24 caught in the sea and 9 in lagoons) and 11 were cultured ones. The prevalence of Contracaecum spp. was higher in Diplodus spp. (16.0%), Sparus aurata (15.8%) and Mullus spp. (14.6%). Larvae were also found by enzymatic digestion at muscular level in 5 species, with the highest prevalence in S. aurata (10.5%). The results of this study indicate that Contracaecum spp. was present in cultured fish such as S. aurata, Diplodus spp. and Dicentrarchus labrax. All cultured fish with parasites were collected from land-based semi-intensive tanks whose water came from an adjacent lagoon. Finally, the evidence that this parasite is found in both cultured and wild fish leads us to re-consider the zoonotic potential of Contracaecum spp., in particular when one bears in mind its dimensions at the L3 stage, when it is barely visible to the human eye.