Anisakid nematodes are a globally distributed group of marine mammal parasites. Kogiid whales, including the pygmy sperm whale Kogia breviceps, host an assemblage of specific anisakid species. Currently, three species are known to be specific to kogiid hosts, i.e., Skrjabinisakis paggiae, S. brevispiculata, and the less studied Pseudoterranova ceticola. The aim of this study was to investigate the species diversity of anisakid nematodes sampled from a pygmy sperm whale stranded in 2013 at the edge of its distribution range in the Northeast Atlantic, specifically in the North of Scotland. Nematodes were assigned to genus level based on morphology and identified by sequence analysis of the mtDNA cox2 gene and the rDNA ITS region. The present finding represents the first observation of syntopic occurrence of adult stages of S. brevispiculata, S. paggiae, and P. ceticola in a pygmy sperm whale in the Northeast Atlantic, and represent the northernmost record of these species in this area. Skrjabinisakis brevispiculata was the most abundant species, accounting for 55% of the identified nematodes, predominantly in the adult stage. Anisakis simplex (s.s.) was also abundant, with most specimens in the preadult stage, followed by S. paggiae and P. ceticola. The pygmy sperm whale is rarely documented in Scottish waters, and its occurrence in the area could suggest expansion of its geographic range. The presence of S. brevispiculata, S. paggiae, and P. ceticola in this whale species in this region may indicate a shift in the whole host community involved in the life cycle of these parasites in northern waters. However, it is also plausible that these parasites were acquired while the whale was feeding in more southern regions, before migrating northbound.
UNASSIGNED: Diversité des parasites Anisakidae chez un cachalot pygmée, Kogia breviceps (Cetacea : Kogiidae) échoué à la limite de son aire de répartition dans l’Atlantique Nord-Est.
UNASSIGNED: Les nématodes Anisakidae sont un groupe de parasites de mammifères marins réparti dans le monde entier. Les cétacés Kogiidae, y compris le cachalot pygmée Kogia breviceps, hébergent un assemblage d’espèces d’Anisakidae spécifiques. Actuellement, trois espèces sont connues pour être spécifiques aux hôtes Kogiidae, à savoir Skrjabinisakis paggiae, S. brevispiculata et Pseudoterranova ceticola, la moins étudiée. Le but de cette étude était d’étudier la diversité des espèces de nématodes Anisakidae échantillonnés sur un cachalot pygmée échoué en 2013 à la limite de son aire de répartition dans l’Atlantique Nord-Est, plus précisément au nord de l’Écosse. Les nématodes ont été attribués au niveau du genre en fonction de la morphologie et identifiés par analyse de séquence du gène cox2 de l’ADNmt et de la région ITS de l’ADNr. La présente découverte représente la première observation de l’apparition syntopique de stades adultes de S. brevispiculata, S. paggiae et P. ceticola chez un cachalot pygmée dans l’océan Atlantique Nord-Est, et représente le signalement le plus septentrional de ces espèces dans cette zone. Skrjabinisakis brevispiculata était l’espèce la plus abondante, représentant 55% des nématodes identifiés, principalement au stade adulte. Anisakis simplex (s.s.) était également abondant, la plupart des spécimens étant au stade préadulte, suivi par S. paggiae et P. ceticola. Le cachalot pygmée est rarement documenté dans les eaux écossaises et sa présence dans la région pourrait suggérer une expansion de son aire de répartition géographique. La présence de S. brevispiculata, S. paggiae et P. ceticola chez cette espèce de cachalot dans cette région peut indiquer un changement dans l’ensemble de la communauté hôte impliquée dans le cycle de vie de ces parasites dans les eaux nordiques. Cependant, il est également plausible que ces parasites aient été acquis alors que le cachalot se nourrissait dans des régions plus au sud, avant de migrer vers le nord.

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.

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

A survey on Anisakis simplex (sensu stricto (s.s.)) from blue whiting, Micromesistius poutassou, in the north-eastern Atlantic Ocean revealed the occurrence of high infection levels of third larval stages in visceral organs and flesh. Larvae were genetically identified with a multilocus approach as A. simplex (s.s.). Histochemical, immunohistochemical and ultrastructural observations were conducted on 30 M. poutassou specimens. Gonads, pyloric caeca and flesh harboured encapsulated larvae of A. simplex (s.s.) but no intense host reaction was encountered around the parasite in the above organs. In the liver, the most infected organ, the larvae co-occurred with the coccidian Goussia sp. Within the granuloma around the A. simplex (s.s.) larvae, two concentric layers were recognized, an inner mostly comprising electron-dense epithelioid cells and an outer layer made of less electron-dense epithelioid cells. Macrophages and macrophage aggregates (MAs) were abundant out of the granulomas, scattered in parenchyma, and inside the MAs, the presence of engulfed Goussia sp. was frequent. In liver tissue co-infected with Goussia sp. and A. simplex (s.s.), hepatocytes showed cytoplasmic rarefaction and acute cell swelling. Results suggest that the host-induced encapsulation of A. simplex (s.s.) larvae is a strategic compromise to minimize collateral tissue damage around the larval infection sites, to facilitate the survival of both parasite and host.

Studies describing the parasite fauna of sunfish species from the Mediterranean Sea are to date limited, despite information gained through parasitological examination may reveal unknown ecological and biological aspects of both hosts and parasites. Moreover, recent molecular studies on sunfish taxonomy revealed the presence of two species belonging to the genus Mola in the Mediterranean basin, namely M. mola and M. alexandrini. These two fish taxa have long been synonymized or confused among them, which implies that the majority of the studies carried out so far reported the parasites infecting both species under a single host species, generally referred to as M. mola. We hereby investigated the parasite fauna of a 43 cm long M. mola specimen from the Mediterranean Sea, whose identification was confirmed by molecular tool, and provided the first evidence of the occurrence of the nematode Anisakis simplex (s.s.) and of the cestode Gymnorhynchus isuri in Mola species anywhere. The use of helminth species as biological tags for the sunfish is also discussed.

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.

Anisakiosis is a fish-borne disease with gastrointestinal and/or allergic symptoms caused by the consumption of raw or undercooked fish parasitized with nematode larvae of the genus Anisakis. In Europe, Anisakis pegreffii has been detected as the causative agent, although the sibling species Anisakis simplex sensu stricto (s.s.) is also known to cause the disease in other parts of the world, and discrepancies exist regarding their respective pathogenic potential. In Spain a high number of cases has been recorded, with marinated anchovies being the main source of infection, although no specific diagnosis has been documented in humans. In this study, we analyzed three cases of anisakiosis in patients from Barcelona (Spain) who had consumed undercooked hake. All patients described epigastric pain and several larval nematodes were removed endoscopically from their stomachs. Larvae were morphologically characterized as third-stage larvae of Anisakis simplex sensu lato (s.l.) and molecularly identified as A. simplex (s.s.) by means of PCR RFLP of the ITS region of the rDNA and sequencing of the elongation factor1 alpha1 (EF1 α-1) nDNA gen. This study represents the first specific identification of Anisakis larvae in clinical cases of anisakiosis reported in Spain. Specific molecular diagnosis is of crucial importance for assessing the health risk of Anisakis sibling species. Hake consumption stands out as a risk factor for anisakiosis, since this fish species can be highly parasitized.

Anisakid larvae are a prevalent food-borne pathogen that has been found in numerous fish species destined for human consumption. The accidental consumption of infected raw or poorly cooked fish may cause gastroenteric diseases and allergies in humans. In spite of the fact that thorough cooking or freezing kills Anisakis worms, this method does not destroy their allergenic capacity. The presence of A. simplex (s.s.) in seafood products may present a health risk for consumers. In Turkey, Atlantic mackerels are marketed as frozen and mainly imported from Norway. The aim of this study was to identify the Anisakis species found in deep-frozen whole Atlantic mackerel (Scomber scombrus) destined for human consumption in fish markets that imported fish from Norway to Turkey. All Anisakis larvae isolated from imported Atlantic mackerel were identified via morphology as third larvae of Anisakis Type I. The ITS region (ITS-1, 5.8S subunit, ITS-2) was amplified and digested with the restriction enzymes Hinf I and Hha I. Larvae of the genus Anisakis were identified via PCR-RFLP as belonging to Anisakis simplex (s.s.), and this was confirmed by sequencing the cox2 gene. The overall prevalence of Anisakis larvae was 25% (95% confidence limits: 13-41%), and the mean intensity was 19.1 (bootstrap 95% confidence limits: 15.3-25.5). Recognized zoonotic A. simplex (s.s.) larvae found in imported Atlantic mackerel could represent a risk. Those who consume them could acquire parasitic allergies. The results will have an important impact on public health risk assessment in that they suggest reviewing critical control points at the Hazard Analysis Critical Control Point (HACCP) programmer to reduce the risk of anisakid-induced allergies among consumers. Consequently, the present study provides the first data regarding the occurrence of A. simplex (s.s.) larvae in imported Atlantic mackerel in Turkish markets.