The heterophyid trematode Metagonimus romanicus (Ciurea, 1915) (Digenea) is redescribed on the basis of type material from domestic dogs (Canis familiaris) in Romania, vouchers from experimentally infected cats (Felis catus) and adults recovered from golden hamsters (Mesocricetus auratus) infected with metacercariae from scales of chub (Squalius cephalus) and common nase (Chondrostoma nasus) (Cypriniformes: Leuciscidae) in Hungary. This trematode, endemic to Europe and neighbouring regions (northwestern Türkiye), was previously misidentified as M. yokogawai (Katsurada, 1912), a zoonotic parasite of humans in East Asia. However, the two species differ considerably both genetically and morphologically, e.g., in the position of the ventral sucker, the presence of the prepharynx, the anterior extent of the vitelline follicles and the posterior extent of the uterus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), described from domestic cats and dogs in Israel, is a valid species distributed in the Middle East and Transcaucasia, which is also confirmed by molecular data. It differs from all Metagonimus species, including M. romanicus, in having symmetrical testes instead of the oblique testes of the other congeners. The zoonotic significance of M. romanicus and M. ciureanus is unclear, but appears to be low in Europe, mainly because raw or undercooked, whole fish with scales are generally not consumed. Accidental infection of fishermen by metacercariae in the scales when cleaning fish is more likely, but has never been reported. Remains of cyprinoids with scales infected with metacercariae of Metagonimus spp. can be an important natural source of infection for dogs, cats, and other carnivores, which can serve as a reservoir for these parasites.

TITLE: Petits trématodes intestinaux du genre Metagonimus (Digenea : Heterophyidae) en Europe et au Moyen-Orient : revue de parasites à potentiel zoonotique. ABSTRACT: Le trématode Heterophyidae Metagonimus romanicus (Ciurea, 1915) (Digenea) est redécrit sur la base de matériel type provenant de chiens domestiques (Canis familiaris) en Roumanie, de vouchers issus de chats (Felis catus) infectés expérimentalement et d’adultes collectés chez des hamsters dorés (Mesocricetus auratus) infectés par des métacercaires provenant d’écailles de chevesne commun (Squalius cephalus) et de nase commun (Chondrostoma nasus) (Cypriniformes : Leuciscidae) de Hongrie. Ce trématode, endémique d’Europe et des régions voisines (nord-ouest de la Turquie), avait été précédemment identifié à tort comme étant M. yokogawai (Katsurada, 1912), un parasite zoonotique des humains en Asie de l’Est. Cependant, les deux espèces diffèrent considérablement sur le plan génétique et morphologique, par exemple par la position de la ventouse ventrale, la présence du prépharynx, l’étendue antérieure des follicules vitellins et l’étendue postérieure de l’utérus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), décrite chez des chats et des chiens domestiques en Israël, est une espèce valide répartie au Moyen-Orient et en Transcaucasie, ce qui est également confirmé par des données moléculaires. Cette espèce diffère de toutes les espèces de Metagonimus, y compris M. romanicus, par ses testicules symétriques au lieu des testicules obliques des autres congénères. L’importance zoonotique de M. romanicus et M. ciureanus n’est pas claire, mais semble faible en Europe, principalement parce que les poissons n’y sont généralement pas consommés crus ou insuffisamment cuits et entiers avec les écailles. L’infection accidentelle des pêcheurs par des métacercaires présents dans les écailles lors du nettoyage du poisson est plus probable mais n’a jamais été signalée. Les restes de poissons cyprinoïdes avec les écailles, infectés par des métacercaires de Metagonimus spp. peuvent être une source naturelle importante d’infection pour les chiens, les chats et autres carnivores, qui peuvent servir de réservoir à ces parasites.

• Keywords
• Fish-borne zoonoses, Genotyping, Palaearctic region, Redescription, SEM, Taxonomy, Trematoda,
• MeSH
• Cyprinidae * MeSH
• Heterophyidae * anatomy & histology   MeSH
• Trematode Infections * epidemiology   veterinary   parasitology   MeSH
• Cats MeSH
• Mesocricetus MeSH
• Humans MeSH
• Metacercariae MeSH
• Parasites * MeSH
• Dogs MeSH
• Trematoda * MeSH
• Animals MeSH
• Check Tag
• Cats MeSH
• Humans MeSH
• Dogs MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Geographicals
• Europe epidemiology   MeSH
• Middle East epidemiology   MeSH

South African clinids are a major component of the temperate intertidal regions that are also known to participate in life cycles and transmission of several groups of parasites. However, the knowledge of trematode diversity of these fishes is incomplete. In this study, two species of Clinus Cuvier, the super klipfish Clinus superciliosus (Linnaeus) and the bluntnose klipfish Clinus cottoides Valenciennes, were collected from six localities along the South African coast and examined for the presence of trematodes. Metacercariae of Cardiocephaloides Sudarikov, 1959 were found in the eye vitreous humour and brain of C. superciliosus and in the eye vitreous humour of C. cottoides. Detailed analyses integrating morphological and molecular sequence data (28S rDNA, ITS2 rDNA-region, and COI mtDNA) revealed that these belong to two species, Cardiocephaloides physalis (Lutz, 1926) and an unknown species of Cardiocephaloides. This study provides the first report of clinid fishes serving as intermediate hosts for trematodes, reveals that the diversity of Cardiocephaloides in South Africa is higher than previously recorded, and highlights the need for further research to elucidate the life cycles of these trematode species. The broad geographical distribution of Cardiocephaloides spp. was confirmed in the present study based on molecular sequence data. The host-parasite interactions between clinid fishes and metacercariae of Cardiocephaloides are yet to be explored.

• Keywords
• Clinus cottoides, Clinus superciliosus, DNA, Trematoda, marine fish parasites, morphology,
• MeSH
• Phylogeny MeSH
• Genes, Helminth MeSH
• Trematode Infections parasitology   MeSH
• Host-Parasite Interactions MeSH
• Metacercariae anatomy & histology   classification   genetics   isolation & purification   MeSH
• Fish Diseases parasitology   MeSH
• Perciformes parasitology   MeSH
• DNA, Ribosomal genetics   MeSH
• Fishes parasitology   MeSH
• Life Cycle Stages MeSH
• Trematoda * anatomy & histology   classification   genetics   isolation & purification   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• South Africa MeSH
• Names of Substances
• DNA, Ribosomal MeSH

Strigeid trematodes of the genus Apatemon Szidat, 1928 are intestinal parasites of fish-eating birds, utilizing various fish species as second intermediate hosts. In this study, we report morphometrical and molecular characterization of Apatemon sp. metacercariae parasitizing killifish Nothobranchius furzeri (Cyprinodontiformes: Nothobranchiidae) in south-east Mozambique. Metacercariae obtained from the cerebral cavity of killifish and two adult individuals isolated from experimentally infected ducklings were used for detailed morphological and molecular description, both resulting in generic affiliation to Apatemon. This is the first molecularly confirmed record of this trematode genus in Africa. Considering the morphological variability and wide host range of individual Apatemon species, the combination of both morphological and molecular analyses is indispensable for valid identification of this parasite. The results of our molecular analysis together with phylogenetic reconstruction indicated the presence of a new African lineage, reflecting potentially high diversity within the genus Apatemon comparable with other digenean genera.

• Keywords
• Africa, Apatemon, Morphology, Nothobranchius furzeri, Strigeidae, Taxonomy,
• MeSH
• Cyprinodontiformes * MeSH
• Genes, Helminth MeSH
• Trematode Infections parasitology   veterinary   MeSH
• Metacercariae anatomy & histology   classification   genetics   growth & development   MeSH
• Multigene Family MeSH
• Fish Diseases parasitology   MeSH
• Helminth Proteins analysis   MeSH
• Electron Transport Complex IV analysis   MeSH
• RNA, Helminth analysis   MeSH
• Trematoda anatomy & histology   classification   genetics   growth & development   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Mozambique MeSH
• Names of Substances
• Helminth Proteins MeSH
• Electron Transport Complex IV MeSH
• RNA, Helminth MeSH

BACKGROUND: Despite their complex life-cycles involving various types of hosts and free-living stages, digenean trematodes are becoming recurrent model systems. The infection and penetration strategy of the larval stages, i.e. cercariae, into the fish host is poorly understood and information regarding their entry portals is not well-known for most species. Cardiocephaloides longicollis (Rudolphi, 1819) Dubois, 1982 (Digenea, Strigeidae) uses the gilthead seabream (Sparus aurata L.), an important marine fish in Mediterranean aquaculture, as a second intermediate host, where they encyst in the brain as metacercariae. Labelling the cercariae with in vivo fluorescent dyes helped us to track their entry into the fish, revealing the penetration pattern that C. longicollis uses to infect S. aurata. METHODS: Two different fluorescent dyes were used: carboxyfluorescein diacetate succinimidyl ester (CFSE) and Hoechst 33342 (NB). Three ascending concentrations of each dye were tested to detect any effect on labelled cercarial performance, by recording their survival for the first 5 h post-labelling (hpl) and 24 hpl, as well as their activity for 5 hpl. Labelled cercariae were used to track the penetration points into fish, and cercarial infectivity and later encystment were analysed by recording brain-encysted metacercariae in fish infected with labelled and control cercariae after 20 days of infection. RESULTS: Although the different dye concentrations showed diverse effects on both survival and activity, intermediate doses of CFSE did not show any short-term effect on survival, permitting a brighter and longer recognition of cercariae on the host body surface. Therefore, CFSE helped to determine the penetration points of C. longicollis into the fish, denoting their aggregation on the head, eye and gills region, as well as on the dorsal fin and the lower side. Only CFSE-labelled cercariae showed a decreased number of encysted metacercariae when compared to control. CONCLUSIONS: Our study suggests that CFSE is an adequate labelling method for short-term in vivo studies, whereas NB would better suit in vivo studies on long-term performance. Cardiocephaloides longicollis cercariae seem to be attracted to areas near to the brain or those that are likely to be connected to migration routes to neuronal canals.

• Keywords
• Cardiocephaloides longicollis, Cercarial penetration pattern, Cercarial survival and activity, Digenea, Metacercarial encystment,
• MeSH
• Benzimidazoles MeSH
• Cercaria MeSH
• Fluoresceins MeSH
• Fluorescent Dyes * MeSH
• Trematode Infections transmission   veterinary   MeSH
• Host-Parasite Interactions * MeSH
• Larva MeSH
• Metacercariae MeSH
• Sea Bream parasitology   MeSH
• Fish Diseases parasitology   MeSH
• Life Cycle Stages MeSH
• Succinimides MeSH
• Trematoda growth & development   physiology   MeSH
• Aquaculture MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• 5-(6)-carboxyfluorescein diacetate succinimidyl ester MeSH Browser
• Benzimidazoles MeSH
• bisbenzimide ethoxide trihydrochloride MeSH Browser
• Fluoresceins MeSH
• Fluorescent Dyes * MeSH
• Succinimides MeSH

We report digeneans (Diplostomidae, Crassiphialinae) in the endangered freshwater fishes Valencia letourneuxi and Valencia robertae, endemics of Western Greece. Digenean metacercariae occurred in two forms in the abdominal cavity, excysted and encysted, the latter attached to the gonads, liver and alimentary tract. Parasites were, using morphological and molecular techniques, identified as two representatives of Crassiphialinae, specifically part of the Posthodiplostomum-Ornithodiplostomum clade. The spatial, seasonal, and age class variation in parasite prevalence was examined. Autumn parasite prevalence varied between the six populations sampled (18.2 to 100%). Seasonal prevalence at the two sites sampled quadannually peaked in autumn and reached its lowest value in spring; prevalence increased with size to 100% in young adult fish. We did not find a correlation between prevalence and host sex. Overall parasites' weight averaged 0.64% of the host's, while parasite weight increased with host weight. A comparison of relative condition and hepatosomatic and gonadosomatic indices of infected and metacercariae-free specimens showed that infection did not have a significant effect on host body condition and reproduction. Regarding the parasite's life cycle, planorbid gastropods are proposed as potential first intermediate hosts in view of the host's diet and occurrence data of molluscs in the ecosystem. This is the first record of a diplostomid digenean in valenciid fishes and of representatives of the Posthodiplostomum-Ornithodiplostomum clade in a native Greek freshwater fish. Our findings are discussed in conjunction to fish conservation interventions, since parasites may contribute to the decline of endangered species.

• Keywords
• Digenea, Host body condition, Parasite prevalence, Planorbidae, Platyhelminthes, Valenciidae,
• MeSH
• Killifishes parasitology   MeSH
• Ecosystem MeSH
• Trematode Infections parasitology   veterinary   MeSH
• Mollusca parasitology   MeSH
• Metacercariae * MeSH
• Fish Diseases parasitology   MeSH
• Endangered Species MeSH
• Fresh Water MeSH
• Life Cycle Stages MeSH
• Trematoda classification   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Greece MeSH

Metacercariae of a North American digenean Posthodiplostomum cf. minimum centrarchi (Strigeiformes: Diplostomidae), have been reported from seven localities in Europe, with cysts recorded in the mesentery and internal organs of two invasive non-indigenous fishes (Lepomis gibbosus and Micropterus salmoides) from sites in Bulgaria, the Czech Republic and Portugal. Analysis of rDNA locus ITS1-ITS2-28S confirmed a closer relationship to the American Posthodiplostomum species than the common European species P. cuticola or P. brevicaudatum. Our data indicate limited potential of this parasite for switch to local fish fauna and confirm the occurrence at distant sites across Europe, suggesting that birds as definitive parasite hosts may play an important role for parasite dispersal. Further detailed studies are needed to confirm the actual means of introduction to Europe.

• Keywords
• Lepomis gibbosus, Micropterus salmoides, Non-indigenous species, Physid snails, White grub,
• MeSH
• Snails parasitology   MeSH
• Trematode Infections epidemiology   parasitology   veterinary   MeSH
• Metacercariae genetics   isolation & purification   physiology   MeSH
• DNA, Ribosomal Spacer genetics   MeSH
• Fish Diseases epidemiology   parasitology   MeSH
• Perciformes parasitology   MeSH
• Birds parasitology   MeSH
• Trematoda classification   genetics   isolation & purification   physiology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic epidemiology   MeSH
• Europe epidemiology   MeSH
• Portugal epidemiology   MeSH
• United States epidemiology   MeSH
• Names of Substances
• DNA, Ribosomal Spacer MeSH

When parasites invade paired structures of their host non-randomly, the resulting asymmetry may have both pathological and ecological significance. To facilitate the detection and visualisation of asymmetric infections we have developed a free software tool, Analysis of Symmetry of Parasitic Infections (ASPI). This tool has been implemented as an R package (https://cran.r-project.org/package=aspi) and a web application (https://wayland.shinyapps.io/aspi). ASPI can detect both consistent bias towards one side, and inconsistent bias in which the left side is favoured in some hosts and the right in others. Application of ASPI is demonstrated using previously unpublished data on the distribution of metacercariae of species of Diplostomum von Nordmann, 1832 in the eyes of ruffe Gymnocephalus cernua (Linnaeus). Invasion of the lenses appeared to be random, with the proportion of metacercariae in the left and right lenses showing the pattern expected by chance. However, analysis of counts of metacercariae from the humors, choroid and retina revealed asymmetry between eyes in 38% of host fish.

• Keywords
• Diplostomum, Gymnocephalus cernua, Trematoda, bilateral asymmetry, fish, ruffe, software, statistical analysis,
• MeSH
• Trematode Infections parasitology   pathology   MeSH
• Data Interpretation, Statistical MeSH
• Metacercariae physiology   MeSH
• Fish Diseases parasitology   pathology   MeSH
• Perches parasitology   MeSH
• Software * MeSH
• Trematoda physiology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH

Freshwater pulmonate snails from three locations in Lake Furesø north of Copenhagen were screened for infection with furcocercariae (by shedding in the laboratory) and recovered parasite larvae were diagnosed by molecular methods (by performing PCR of rDNA and sequencing the internal transcribed spacer [ITS] region). Overall prevalence of infection in snails was 2%. Recovered cercariae from Lymnaea stagnalis (Linnaeus) were diagnosed as Diplostomum pseudospathaceum Niewiadomska, 1984 (prevalence 4%) and cercariae from Radix balthica (Linnaeus) as D. mergi (Dubois, 1932) (prevalence 2%). Pathogen-free rainbow trout were then exposed to isolated cercariae and infection success and site location of metacercariae in these fish were determined. Infection experiments confirmed that both species could infect rainbow trout with the eye lens as infection site for the metacercarial stage although infection success differed. Combination of molecular and biological assays may contribute to improvement of our knowledge on diagnosis, distribution and biology of diplostomids in fish.

• MeSH
• Ecology MeSH
• Phylogeny MeSH
• Snails parasitology   MeSH
• Trematode Infections parasitology   transmission   veterinary   MeSH
• Lakes parasitology   MeSH
• Metacercariae MeSH
• DNA, Ribosomal Spacer chemistry   genetics   MeSH
• Molecular Sequence Data MeSH
• Fish Diseases parasitology   transmission   MeSH
• Oncorhynchus mykiss parasitology   MeSH
• Specific Pathogen-Free Organisms MeSH
• Polymerase Chain Reaction veterinary   MeSH
• Seasons MeSH
• Fishes MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA veterinary   MeSH
• Fresh Water parasitology   MeSH
• Trematoda genetics   isolation & purification   physiology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Denmark MeSH
• Names of Substances
• DNA, Ribosomal Spacer MeSH

This report addresses the possible impacts of local habitat characteristics on the metacercariae of Clinostomum schizothoraxi Kaw, 1950 infecting crucian carp, Carassius carassius (Linnaeus), from three lakes in Kashmir. The lakes chosen encompass an extremely wide gradient in trophic status--Manasbal (less polluted and mesotrophic), Dal (moderately polluted and eutrophic) and Anchar (strongly polluted and hypertrophic). The results indicate that infrapopulation-level descriptors of abundance of C. schizothoraxi in fish differed between the three lakes and revealed that the infection levels were greater at Anchar Lake. Furthermore, the prevalence, mean abundance and mean intensity of infection also changed during the period of investigation along the seasonal gradient of water temperature. The fact that the abundance patterns of the parasite differed in different populations of the same host provided a unique opportunity for a comparative study on the temporal variations in infection patterns attained during different seasons. In particular, the lake environments showed a high degree of variability in the density profiles of mollusc intermediate hosts and, thus, the differences in the infection status of crucian carp were derived on the basis of intermediate host population size which, in turn, was influenced by the trophic characteristics of the three lakes.

• MeSH
• Ecosystem MeSH
• Snails parasitology   MeSH
• Population Density MeSH
• Trematode Infections epidemiology   parasitology   veterinary   MeSH
• Host-Parasite Interactions MeSH
• Lakes MeSH
• Carps parasitology   MeSH
• Larva MeSH
• Metacercariae MeSH
• Fish Diseases epidemiology   parasitology   MeSH
• Prevalence MeSH
• Seasons MeSH
• Temperature MeSH
• Trematoda isolation & purification   MeSH
• Water Pollution MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• India epidemiology   MeSH

The present study describes the anatomy and surface topography of the metacercaria of Microphallusprimas (Jägerskiöld, 1909) infecting the shore crab Carcinus maenas (L.) in Aveiro estuary, northern Portugal. The metacercaria species identification resulted from the combined use of morphological and molecular data, particularly the 28S rDNA gene. The metacercariae encysted preferentially in the host's hepatopancreas and also in the gonads. Isolated cysts were present in two distinct forms, spherical and oval, and were shown to be the identical species by the internal transcribed spacer 1 (ITS1) sequence. Chemically excysted metacercariae were studied by light (LM) and scanning electron microscopy (SEM). Their specific characteristics observed include the particular aspect of the vesiculo-prostatic pouch surrounded by a very thin membrane, the presence of a prominent muscular papilla, and an obvious metraterm. The dorsal and ventral tegumental surfaces of the metacercaria were densely packed with similar squamous spines, which decreased in number and size towards the hindbody. The edges of the posterior and ventral face of the body were coated with numerous microvilli, whose function remains unknown. In order to identify the species of metacercariae, we compared a 28S partial rDNA sequence of the two forms of cysts with the same 28S partial region of M. primas available in GenBank. With this comparison, we determined that the sequences had a 100% similarity and therefore belonged to the same species, i.e., M. primas.

• MeSH
• DNA, Helminth chemistry   MeSH
• Brachyura parasitology   MeSH
• Larva genetics   growth & development   ultrastructure   MeSH
• Metacercariae genetics   growth & development   ultrastructure   MeSH
• DNA, Ribosomal Spacer genetics   MeSH
• Microscopy, Electron, Scanning MeSH
• Molecular Sequence Data MeSH
• DNA, Ribosomal chemistry   MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA MeSH
• Trematoda classification   genetics   growth & development   ultrastructure   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Portugal MeSH
• Names of Substances
• DNA, Helminth MeSH
• DNA, Ribosomal Spacer MeSH
• DNA, Ribosomal MeSH