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Freshwater crabs (Potamiscus manipuriensis), commonly consumed as local delicacies by the native people in the state of Manipur, were found to harbour metacercariae of Microphallus sp. (Family Microphyllidae), which were morphologically different from metacercariae of Microphallus spp reported earlier from different regions. So, PCR-based molecular characterization of this metacercaria was done utilizing rDNA marker regions: larger subunit (LSU) or 28S (D1-D3 region) and inter-transcribed spacer 2 (ITS2). Sequence and phylogenetic analyses confirmed that the taxon under study belonged to family Microphyllidae of genus Microphallus. [ABSTRACT FROM AUTHOR]

[Display omitted] • Previous population genetic analysis of Opisthorchis viverrini eggs revealed two populations. • Cat- and human-specific populations use different intermediate fish hosts. • There are distinct morphologies in egg, metacercaria, and adult worm stages of O. viverrini. • Our study confirms distinct human- and cat-specific O. viverrini populations. Infection by the zoonotic fish-borne trematode, Opisthorchis viverrini, remains a crucial health issue in Thailand and neighboring countries. Recently, molecular analysis revealed two populations of putative O. viverrini : one found primarily in human hosts ("human-specific" population) and the other primarily in cats ("cat-specific" population). It is unclear how the infective stages (metacercariae) of these different populations circulate among definitive and reservoir hosts in nature. To gain an insight into this, mitochondrial cox 1 and nad 1 gene sequences of metacercariae from fish intermediate hosts were examined. None of 192 metacercariae from cyprinid fish in Lao PDR and Thailand had sequences typical of "cat-specific" O. viverrini , suggesting that cyprinid fish are not the main second intermediate hosts of this population. Interestingly, all 20 O. viverrini -like metacercariae from snakehead fish (Channa striata) shared 99.51–100% sequence identity with eggs from cats naturally infected in a previous study. Hence, we propose a modification of the known transmission dynamics of O. viverrini : consumption of metacercariae within snakehead fish provides another pathway for cats and (occasionally) humans to acquire infection. We also performed morphological comparisons of eggs, metacercariae, and adult flukes (raised in hamsters) of both Opisthorchis populations. The "cat-specific" population has eggs that are narrower and adults that are shorter and wider than in the human-specific population. The metacercaria of the "cat-specific" population is elliptical, while that of the "human-specific" population is oval, occasionally rounded. Our results confirmed that O. viverrini -like metacercariae from snakehead fish are the infective stages of the "cat-specific" fluke. This provides a new insight into the dissemination and transmission of each population in the second intermediate host. The identity of the cat-specific population is discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: The apple snail is one of the most dangerous invasive species in freshwater environments. Using molecular and morphological tools, we re-describe an echinostomatid digenean parasitizing snails from two sites in the Buenos Aires Province, Argentina. The two stages found (i.e., rediae and metacercariae) demonstrate that the apple snail acts as the first and second intermediate host in its life cycle. The prevalence of the parasite was higher at one of the sampling sites, probably because the birds bearing the adult stage are more abundant in that area. A histological study showed that this parasite quickly invades multiple organs of the snail, which is different from most digenean infections, which only infect the gonad and digestive glands. Heavy deterioration of female and male reproductive structures associated with the presence of the parasite was also observed, which indicates castration. Pomacea canaliculata is one of the most dangerous invasive species. Morphological and molecular analyses have revealed that a digenean species belonging to the family Echinostomatidae parasitizes this snail at two sites in Buenos Aires Province, Argentina, South America. Molecular results confirmed that the species belongs to a genus closely related to Patagifer. Analysis of the 28S rDNA showed that the sequences of the rediae and metacercariae are identical, indicating that the apple snail acts as the first and second intermediate host. The cercariae may encyst as metacercaria inside the redia and also emerge and re-infect the same snail or another snail. The prevalence of digeneans was higher in one of the sampling locations (15.1% vs. 0.72%), probably because the bird species that acts as the definitive host is more abundant in that area. Histopathological examination showed that the parasite quickly invades multiple host organs (gills, intestines, albumen gland, lung, kidney, and mantle border) besides the gonad and digestive gland, as is usual in digeneans. In addition, the partial or total castration of snails was observed in cases of moderate and high infection intensity. In males, there was loss of integrity in testicular tubules, while in females, the replacement of ovarian tissue by rediae was found. [ABSTRACT FROM AUTHOR]

Three helminth species were recorded in a helminthological survey of the black-striped pipefish Syngnathus abaster (13 individuals) from the Lake Atanasovsko Wetlands, Bulgaria. These were the cryptogonimid trematode Timoniella imbutiformis (subadult and mature individuals), the opisthorchid trematode Cryptocotyle concava (metacercaria) and the raphidascaridid nematode Hysterothylacium cf. aduncum (third-stage larvae). Of them, T. imbutiformis was the most prevalent parasite species (15.38%). The other two helminth species were with lower prevalence, 7.69% each. Previously, these helminth species have not been reported as parasites of S. abaster in Bulgaria. This is the first record of Timoniella imbutiformis for the fauna of Bulgaria. [ABSTRACT FROM AUTHOR]

It is uncertain when the head collar and collar spines of Isthmiophora hortensis (Digenea: Echinostomatidae), a zoonotic echinostome species in Far Eastern Asia, develop during its larval stages. In this study, the appearance of the head collar and collar spines was studied using light and scanning electron microscopy in cercariae and metacercariae experimentally obtained from freshwater snails (Lymnaea pervia) and tadpoles (Rana nigromaculata), respectively. The cercariae were shed from the snail on day 30 after exposure to laboratory-hatched miracidia. Metacercariae were obtained from the experimental tadpoles at 3, 6, 12, 15, 20, 24, 26, and 30 h after exposure to the cercariae. The head collar was already visible in the cercarial stage, although its degree of development was weak. However, collar spines did not appear in the cercarial stage and even in the early metacercarial stage less than 24 h postinfection in tadpoles. Collar spines became visible in the metacercariae when they grew older than 24 h. It was concluded that the head collar of I. hortensis developed early in the cercarial stage, but the development of collar spines did not occur until the worms became 24-h-old metacercariae in our experimental setting. Counting the number of collar spines was concluded as an unfeasible diagnostic method for I. hortensis cercariae when they are shed from the snail host. [ABSTRACT FROM AUTHOR]

This article analyzed the infection characteristics of metacercariae of Metagonimus spp. (MsMc) in fish from 9 major water systems in Korea. A total of 19,568 fish in 87 species were examined over a period of 10 years (2011-2020). MsMc were detected in fish from all 44 survey areas in 9 water systems. Most of the surveyed sites showed very low and low infection levels (66.7%), while 33.3% of the areas, such as Tamjin-gang and Seomjin-gang, revealed moderate and high infection levels. High endemicity depends on the abundance of susceptible fish species, especially sweet smelt (Plecoglosus altivelis). The susceptibility index (SI) with MsMc in index fish, Zacco spp., was very low and low levels in 62.0%, moderate in 28.0%, and high in 10.0% regions. The SI was highest in the following order: Yeongam-cheon (283.8), Hoeng-cheon (192.3), Togyo-jeosuji (131.2), Deokcheon-gang (119.1), and Joyang-gang (106.3). The recent infection status of MsMc in P. altivelis was analyzed by the survey localities. In addition, except for P. altivelis, 9 fish species were highly infected with MsMc in some survey areas, including Zacco platypus, Z. koreanus, Z. temminckii, Opsariichthys uncirostris, Rhynchocypris oxycephalus, Carassius auratus, Acheilognathus rhombeus, Onchorhynchus masou, and Tribolodon hakonensis. In Korea, 74 fish species (15 families) are collectively listed as second intermediate hosts of Metagonimus spp. This review provides several novel characteristics of MsMc infection and clarifies the fish species of second intermediate host of Metagonimus spp. in this country. [ABSTRACT FROM AUTHOR]

Red swamp crayfish Procambarus clarkii were collected from Cattail Marsh in Beaumont, Texas and necropsied. Eight (13%) of 62 crayfish collected were infected with metacercariae of Crepidostomum cornutum. Excysted metacercariae were stained and mounted for morphologic identification or preserved for molecular analysis. Morphometric values were consistent with those reported previously in the literature. Sequences of the 28S ribosomal RNA gene were aligned with the National Center for Biotechnology Information GenBank database. Blast analysis returned a result of 99% similarity for C. cornutum. This study provides the first report of C. cornutum metacercariae infecting P. clarkii in Texas substantiated by a voucher specimen and sequence data. Molecular data from this study should prove helpful in identification of adult stages from fish and cercariae from bivalves in future studies. [ABSTRACT FROM AUTHOR]

Cyprinid fishes are commonly acted as second intermediate hosts of Opisthorchis viverrini and Haplorchis spp. This research investigated the prevalence and intensity of both parasites in cyprinid species. This process is regularly used as a guideline for disease surveillance and as a preventive measure in the Upper Northeastern region of Thailand. Fish samples were collected from both lentic and lotic water sources between November 2020 and October 2021, and classified them by their species. Acid pepsin-HCL solution was used to digest the individual samples and create a build-up of precipitate in order to view metacercariae using a stereomicroscope. A total of 3583 fish were caught and classified into 23 species. Out of these fish, 5.49% of them were found O. viverrini, 26.54% Haplorchis taichui, 10.04% Haplorchis pumilio, and 9.29% Haplorchoides sp. Ten species of fish were observed to have been infected with O. viverrini. Amongst the collected fish, M. obtusirostris had the highest prevalence of infection at 52.94%, while B. gonionotus had only 1.71%. The prevalence of O. viverrini infection was highest at 27.41% in Udon Thani Province. No prevalence of O. viverrini infection was observed in Bueng Kan Province. High prevalence of O. viverrini infection in cyprinid fishes was found in both lentic and lotic water sources in almost all provinces in the region. The prevalence of infection and intensity depended on the fish species and fish habitats.

In the fall of 2021, California Department of Fish and Wildlife reported larval and adult California giant salamanders (Dicamptodon ensatus Eschscholtz, 1833) with skin lesions at multiple creeks in Santa Clara and Santa Cruz Counties, California, USA. Field signs in both stages included rough, lumpy textured skin, and larvae with tails that were disproportionately long, flat, wavy, and flaccid. Presence of large-bodied larvae suggested delayed metamorphosis, with some larvae having cloudy eyes and suspected blindness. To determine the cause of the disease, three first-of-the-year salamanders from one location were collected, euthanized with 20% benzocaine, and submitted for necropsy to the U.S. Geological Survey, National Wildlife Health Center. Upon gross examination, all salamanders were emaciated with no internal fat stores, and had multiple pinpoint to 1.5-mm diameter raised nodules in the skin over the body, including the head, gills, dorsum, ventrum, all four limbs, and the tail; one also had nodules in the oral cavity and tongue. Histologically all salamanders had multiple encysted metacercariae in the dermis, subcutis, and skeletal muscles of the head, body, and tail that were often associated with granulomatous and granulocytic inflammation and edema. A small number of encysted metacercariae or empty cysts were present in the gills with minimal inflammation, and rarely in the kidney with no associated inflammation. Morphology of live metacercariae (Trematoda: Heterophyiidae), and sequencing of the 28S rRNA gene identified a species of Euryhelmis (Poche, 1926). Artificial digestion of a 1.65 g, decapitated, eviscerated carcass yielded 773 metacercariae, all of similar size and morphology as the live specimens. Based on these findings, the poor body condition of these salamanders was concluded to be due to heavy parasite burden. Environmental factors such as drought, increased temperature, and overcrowded conditions may be exacerbating parasite infections in these populations of salamander.

Prosthogonimiasis poses a threat to the reproductive system of poultry and wild birds, which are the definitive hosts of the parasite causing this disease. However, the parasite infection of the second intermediate host (dragonfly), the primary vector of this pathogen, is rarely reported. In this study, the prevalence of Prosthogonimus infection in dragonflies was investigated from June 2019 to October 2022 in Heilongjiang Province, northeast China. The species of metacercariae isolated from dragonfly were identified by morphological characteristics, molecular biology techniques, and animal infection experiments. The results showed that 11 species of dragonflies and one damselfly were identified and among six of the dragonflies infected by Prosthogonimus metacercariae, Sympetrum depressiusculum (28.53%) had the highest infection rate among all positive dragonflies, followed by Sympetrum vulgatum (27.86%) and Sympetrum frequens (20.99%), which are preferred hosts, and the total prevalence was 20.39% (2061/10,110) in Heilongjiang Province. Three species of Prosthogoniumus metacercariae were isolated, including Prosthogonimus cuneatus, Prosthogonimus pullucidus, and Prosthogonimus sp., among which P. cuneatus was the dominant species in dragonflies in Heilongjiang Province. This is the first report on the prevalence of Prosthogonimus in dragonflies in China, which provides baseline data for the control of prosthogonimiasis in Heilongjiang Province and a reference for the prevention of prosthogonimiasis in other areas of China. [ABSTRACT FROM AUTHOR]

Phyllodistomum is the large digenean group of fish parasites, with 25 species described so far in the Indian subcontinent. Here, we redescribed two adult species of Phyllodistomum (P. srivastava Rai 1964 and P. parorchium Jaiswal 1957) collected from freshwater fish Heteropneustes fossilis Bloch, 1974 and Glossogobius giuris Ham, 1822, respectively, and an unknown Phyllodistomum metacercaria from shrimp (Macrobrachium dayanum Henderson, 1893). These parasites were genetically characterized using 28S and first and second internal transcribed spacers (ITS1 and ITS2) regions of the nuclear ribosomal DNA and CoxI region of the mitochondrial (mt) DNA to establish the link between metacercaria and adult. Morphologically, both the unknown metacercaria in shrimp and adult Phyllodistomum srivastava in fish, resembled in terms of crenulated margin of hind body, arrangement of diagonal testes, bipartite seminal vesicle, and compact paired vitelline masses. The two adult parasite species, P. srivastava from P. parorchium, were different in terms of shape and size of the body, ratio of suckers, the absence of crenulated margin of hind body, a single chambered seminal vesicle, and deeply lobed paired vitelline masses, in the former species. Comparison of the 28S, ITS, and mtCoxI sequence data suggested P. srivastava and Phyllodistomum metacercaria belong to the same species, and supported the distinction between P. srivastava and P. parorchium. Exploring the potential impact of Phyllodistomum infection on host behaviour and health would be prospective areas for future research. [ABSTRACT FROM AUTHOR]

Clinostomum is a trematode genus in the family Clinostomidae. The mentioned trematode species is parasitizing many fish species as intermediate hosts, while piscivorous birds and mammals are the main definitive hosts. Total of 58 metacercariae of Clinostomum larvae were dissected out from 25 infected fish specimens from eight different species from a number of water bodies of Sulaimani Province, Kurdistan Region, Iraq. In this investigation, 959 fish specimens were collected. These includes five cyprinid species: Capoeta trutta (Heckel), C. umbla (Heckel), Carasobarbus kosswigi (Ladiges), Cyprinion macrostomum Heckel and Garra rufa (Heckel), two leuciscid species: Alburnus sellal Heckel and Squalius lepidus Heckel and the mugilid fish Planiliza abu (Heckel). The prevalence of infection for each of these species was 1.8%, 5%, 20%, 1.5%, 1.7%, 4.9%, 4.9% and 1.3%, respectively. The morphology of the Clinostomum metacercariae was studied by using a compound microscope; their ultra-morphology was evaluated with a scanning electron microscopy (SEM); and the molecular analysis were performed by amplifying, sequencing and comparing the ITS1-5.8S-ITS2 and 28S rDNA gene loci from isolated Clinostomum metacercariae. The obtained sequences confirmed that all metacercariae of the Clinostomum, collected during the present study, represented with C. complanatum (Rudolphi, 1814) based on percent identity with sequences in the GenBank subject database. The molecular characterisations of the C. complanatum metacercariae in the present study were deposited in GenBank NCBI.

Clinostomum is a trematode genus in the family Clinostomidae. The mentioned trematode species is parasitizing many fish species as intermediate hosts, while piscivorous birds and mammals are the main definitive hosts. Total of 58 metacercariae of Clinostomum larvae were dissected out from 25 infected fish specimens from eight different species from a number of water bodies of Sulaimani Province, Kurdistan Region, Iraq. In this investigation, 959 fish specimens were collected. These includes five cyprinid species: Capoeta trutta (Heckel), C. umbla (Heckel), Carasobarbus kosswigi (Ladiges), Cyprinion macrostomum Heckel and Garra rufa (Heckel), two leuciscid species: Alburnus sellal Heckel and Squalius lepidus Heckel and the mugilid fish Planiliza abu (Heckel). The prevalence of infection for each of these species was 1.8%, 5%, 20%, 1.5%, 1.7%, 4.9%, 4.9% and 1.3%, respectively. The morphology of the Clinostomum metacercariae was studied by using a compound microscope; their ultra-morphology was evaluated with a scanning electron microscopy (SEM); and the molecular analysis were performed by amplifying, sequencing and comparing the ITS1-5.8S-ITS2 and 28S rDNA gene loci from isolated Clinostomum metacercariae. The obtained sequences confirmed that all metacercariae of the Clinostomum, collected during the present study, represented with C. complanatum (Rudolphi, 1814) based on percent identity with sequences in the GenBank subject database. The molecular characterisations of the C. complanatum metacercariae in the present study were deposited in GenBank NCBI. [ABSTRACT FROM AUTHOR]

Examination of 4 Ozark cavefish, Troglichthys rosae, collected opportunistically during February 2020 from Benton County, Arkansas, U.S.A., revealed the presence of an unknown myxozoan (Myxobolus sp.) in the gall bladder of 1 fish and encapsulated metacercariae of Clinostomum sp. ("yellow grub") in 2 hosts. One Ozark cavefish harbored 4 metacercaria and the other a single metacercaria. This is the first report of any parasite from T. rosae, a federally threatened species. We also provide a summary of parasites reported from members of the cavefish and swampfish family, Amblyopsidae. [ABSTRACT FROM AUTHOR]

The objective of this study was to conduct a survey of parasites infecting the fat mucket, Lampsilis siliquoidea, during July 2022 at Lemon's Mill along 50 m of North Elkhorn Creek, a tributary of the Kentucky River in Scott County, Kentucky, U.S.A. Fifty-two specimens of L. siliquoidea were collected, and 3 different parasites were recovered. Sporocysts and rhopalocercous cercariae associated with Phyllodistomum sp. (prevalence = 13.5%) were recovered from the visceral mass and mantle cavity, respectively, nymphs and adults of the water mite Unionicola fossulata (prevalence = 96.2%; mean intensity = 3.92 ± 2.25) from the external surface of the gill demibranchs, and the aspidogastrid Cotylaspis insignis (prevalence = 84.6%; mean intensity = 8.50 ± 7.13) from the external surface at the gill-visceral mass junction. Prevalence and mean intensity were not significantly affected by host sex or host size. These results establish a baseline for parasite community structure in L. siliquoidea at the North Elkhorn Creek site. [ABSTRACT FROM AUTHOR]

The present study aimed to determine the infection status of trematode metacercariae and adults in cyprinoid fish from the Khun Thale Swamp in Surat Thani, Southern Thailand, with epidemiologic and faunistic viewpoints. In 2020, 577 fish in 15 species were collected in the summer (February-April) and rainy (September-November) seasons. Fish were individually examined for trematode metacercariae in the whole body and adults in the gastrointestinal tract using a stereomicroscope. Three species of digenetic trematode metacercariae, i.e., Haplorchis taichui, Haplorchoides mehrai, and Centrocestus formosanus, were detected in the muscle, fin, and/or scale of fish. Two species of adult flukes, including Rohdella siamensis and Helostomatis cyprinorum, were collected in the intestines. The prevalence of overall trematode infections was 32.4% (187/577 fish), which was higher in the rainy season (41.4%; 118/285) than in the summer season (23.6%; 69/292). The metacercariae of H. taichui and H. mehrai were detected in 7 fish species each, and those of C. formosanus were found only in Rasbora toneri. The aspidogastrean trematode R. siamensis (adult) was detected in Babonymus gonionotus. A digenean species, H. cyprinorum (adult), was found in Labiobarbus siamensis and Osteochilus vittatus. The present study has first confirmed that the metacercariae of heterophyid flukes, including H. taichui, H. mehrai, and C. formosanus, and adults of R. siamensis (Aspidogastrea) and H. cyprinorum (Digenea) are infected in some species of the cyprinoid fish from the Khun Thale Swamp in Surat Thani, Thailand. [ABSTRACT FROM AUTHOR]

Three juvenile Atlantic tripletail Lobotes surinamensis caught opportunistically in Charleston Harbor (South Carolina, USA) and maintained in captivity for over three months displayed an altered swimming behavior. While no direct causation can be demonstrated herein, fish were infected in their brain by strigeid trematode larvae (metacercariae) of Cardiocephaloides medioconiger, which were identified via ITS2 and 28S ribosomal RNA gene sequencing. Histology showed nonencysted metacercariae within the brain ventricle between the optic tectum and tegmentum, causing distortion of tegmental parenchyma. Aggregates of mononuclear inflammatory cells were in the ventricle adjacent to metacercariae. Metacercarial infection by Cardiocephaloides medioconiger has been reported from the brain and eyes of only two other fish species from the northern US Atlantic coast: the grey mullet Mugil cephalus and silverside Menidia menidia, but this identification is problematic and needs molecular verification. Atlantic tripletail is a new report as a second intermediate host for C. medioconiger and South Carolina is a new locality. Cardiocephaloides species in general have a low host specificity and infection by C. medioconiger could propagate to other fishes and affect neighboring natural ecosystems. [ABSTRACT FROM AUTHOR]

Background: Identification of the larval stages of Echinostoma spp. in freshwater snails is an essential guide to continue monitoring the possibility of their transmission and the potential of echinostomiasis in areas where trematodes are the primary agent of parasitic diseases. The aim of this study was investigate Echinostoma using morphological and molecular techniques. Methods: The study was conducted in Gilan and Mazandaran Provinces, northern Iran, from April 2019 to October 2021. Overall, 5300 freshwater snails were randomly collected and were identified using external shell morphology. Meanwhile, snails infected with trematodes were studied via shedding and dissecting methods. Larvae stages of Echinostoma were identified and the genomic DNA of the samples was extracted. The PCR amplification of the ITSI gene was carried out for 17 isolates and products were sequenced. Seven sequences were deposited in GenBank. Results: Totally, 3.5% of snails containing three species (Stagnicola sp., Radix sp. and Planorbis sp.) were infected with two types of cercaria, E. revolutum with 37 and Echinostoma sp. with 45 spines in the collar. Moreover, 35% of the snails were infected with Echinostoma spp. metacercaria. Phylogenetic analysis illustrated that isolates were included in two ITSI haplogroups. Conclusion: Results showed the potential hazard of a zoonotic parasite as Echinostoma in northern Iran. The potential of disease environmental relationship investigation and resource control optimization is necessary for effective disease prevention and health management. [ABSTRACT FROM AUTHOR]

Summary: Scaphanocephalus is a small trematode genus belonging to the family Opistorchiidae. The genus currently contains only three species associated with marine fish as intermediate hosts and fish-eating birds as definitive hosts. Here, specimens of Scaphanocephalus were collected from the Osprey, Pandion haliaetus , and the White mullet, Mugil curema in the Yucatán Peninsula, Mexico. We report for the first-time DNA sequences of adult specimens of Scaphanocephalus , particularly S. expansus , as well as a sequence of a different species sampled as metacercaria. Morphological comparisons of Scaphanocephalus expansus confirmed the identity of the adult specimens, with minor morphological variations; Scanning electron photomicrographs were included, and the species was re-described. Phylogenetic analysis based on 28S rDNA sequences showed that Scaphanocephalus is monophyletic within Opisthorchiidae and consists of three independent lineages. Sequences of adults are identical to those of S. expansus. Instead, the sequence of the metacercaria sampled from the mesentery of Mugil curema nested with specimens reported as Scaphanocephalus sp. from a labrid fish in the Mediterranean Sea, herein named it as Scaphanocephalus sp. 2. [ABSTRACT FROM AUTHOR]

Procedures for a digestion technique were modified to identify an optimum approach for recovering trematode metacercariae from large, terrestrial snails. Brachylaima thompsoni and Panopistus pricei were recovered via HCl/pepsin digestion from field-collected snails, Webbhelix multilineata and Neohelix albolabris. The incubation temperature, duration, concentration of digestion fluid, agitation, and centrifugation settings were modified until a set of procedures resulted in thorough digestion of the snail body while minimizing the required time to run the procedure and maximizing the fraction of metacercariae that remained alive and active. Most metacercariae died during lengthy digestions and/or those with high concentrations of HCl and pepsin. The optimal procedure identified included a 2 hr digestion in 0.7% HCl and 0.8% pepsin at 37°C with initial cutting of the snail foot and periodic agitation during digestion. This method resulted in recovery of metacercariae that were nearly always alive and appeared no different than specimens recovered by direct dissection of snails. The method developed here is but one of many used for recovery of parasites, usually nematodes, from their invertebrate or vertebrate hosts, but it focuses on those characteristics that allow live trematode recovery. [ABSTRACT FROM AUTHOR]

Background: Identification of the larval stages of Echinostoma spp. in freshwater snails is an essential guide to continue monitoring the possibility of their transmission and the potential of echinostomiasis in areas where trematodes are the primary agent of parasitic diseases. The aim of this study was investigate Echinostoma using morphological and molecular techniques.Methods: The study was conducted in Gilan and Mazandaran Provinces, northern Iran, from April 2019 to October 2021. Overall, 5300 freshwater snails were randomly collected and were identified using external shell morphology. Meanwhile, snails infected with trematodes were studied via shedding and dissecting methods. Larvae stages of Echinostoma were identified and the genomic DNA of the samples was extracted. The PCR amplification of the ITSI gene was carried out for 17 isolates and products were sequenced. Seven sequences were deposited in GenBank.Results: Totally, 3.5% of snails containing three species (Stagnicola sp., Radix sp. and Planorbis sp.) were infected with two types of cercaria, E. revolutum with 37 and Echinostoma sp. with 45 spines in the collar. Moreover, 35% of the snails were infected with Echinostoma spp. metacercaria. Phylogenetic analysis illustrated that isolates were included in two ITSI haplogroups. Conclusion: Results showed the potential hazard of a zoonotic parasite as Echinostoma in northern Iran. The potential of disease environmental relationship investigation and resource control optimization is necessary for effective disease prevention and health management.

Platyhelminths belonging to the family Clinostomidae (Digenea) have a worldwide distribution and are known to infect piscivorous birds through their intermediate hosts, usually fish species. In the present study, clinostome metacercariae were collected from fish hosts, including Channa punctata (Bloch 1793) (n = 25) and Trichogaster fasciata Bloch and Schneider 1801 (n = 25), from a freshwater system in India. The experimental infection of cattle egrets, Ardea (Bubulcus) ibis Linnaeus 1758, with some of the live metacercariae found in the present study was successful. Live adult parasites were obtained from the buccal cavity of the birds. Both metacercaria and adult specimens were subjected to molecular studies to obtain the sequences of 28S, ITS1, and ITS2 (nuclear rDNA) regions. The parasites were found to belong to three species, Clinostomum giganticum Agarwal 1959; C. piscidium Southwell and Prashad 1918; and Euclinostomum heterostomum (Rudolphi 1809). Phylogenetic analyses of the sequences obtained from the adults and metacercariae established a link between the metacercariae in the fish hosts and adults in the avian host, which is essential to elucidate their partial life cycle and specify morphological characteristics in the metacercarial stage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Digenetic trematodes in Manila clam on the west coast of Korea include at least 5 species from 3 families. • Phylogenetic position of three trematodes (Cercaria tapidis , Bacciger bacciger , and Parvatrema duboisi) was revealed. • Metacercariae infection prevalence showed a greater spatial variation compared to the sporocyst infection. The Manila clam Ruditapes philippinarum on the west coast of Korea harbors several digenetic trematodes. However, most studies in this region have been restricted to a few sampling sites and the current species designation of some trematodes is largely based on morphology, leaving the molecular phylogenetic position among the Digenea unsolved. Thus, we first provide both morphology and molecular phylogeny of some components in the trematodes community in the Manila clam based on a large-scale survey of 26 sites on the west coast, where well-developed tidal flats serve as large commercial clam culture beds. Our study revealed that the trematodes community in the clams consisted of at least 5 species that belong to 3 families (Himasthlidae, Gymnophallidae, Baccigeridae) and 1 superfamily (Monorchioidea). The life mode of the 5 different species included the metacercaria and sporocyst, with one species (Parvatrema duboisi) utilizing the clams as both the first and/or second intermediate host. Trematode infection prevalences were not evenly distributed among the study sites, although the reasons behind this are yet to be determined. Morphological identification was confirmed with the molecular analyses based on ITS and 28S rDNA; phylogenetic analysis also revealed that Cercaria pectinata infecting the clam gonad should be referred to as Bacciger bacciger hereafter. The present preliminary study provides a crucial baseline that could be further developed in a future study on the digenean trematodes community in the Manila clam. [ABSTRACT FROM AUTHOR]

In early September 2019, a morbidity and mortality event affecting California tiger salamanders (Ambystoma californiense) and Santa Cruz long-toed salamanders (Ambystoma macrodactylum croceum) in late stages of metamorphosis was reported at a National Wildlife Refuge in Santa Cruz County, California, U.S.A. During the postmortem disease investigation, severe integumentary metacercarial (Class: Trematoda) infection, associated with widespread skin lesions, was observed. Planorbid snails collected from the ponds of the refuge within seven days of the mortality event were infected with Ribeiroia ondatrae, a digenetic trematode that can cause malformation and death in some amphibians. We suggest sustained seasonal high-water levels due to active habitat management along with several years of increased rainfall led to increased bird visitation, increased over-wintering of snails, and prolonged salamander metamorphosis, resulting in a confluence of conditions and cascading of host-parasite dynamics to create a hyper-parasitized state.

Copyright of Revista Veterinaria is the property of Universidad Nacional del Nordeste and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the southern Appalachian Mountains, U.S.A., the trematode Metagonimoides oregonensis, a parasite of raccoons and mink, primarily uses larvae of the salamander Desmognathus quadramaculatus as a second intermediate host. However, evidence suggests that a cryptic, sympatric species, Desmognathus folkertsi is parasitized at a very low level or not at all. We tested the hypothesis that Desmognathus marmoratus, which is phylogenetically a sister to D. folkertsi, also has a low infection rate. We collected larvae of sympatric D. quadramaculatus and D. marmoratus from a stream (Beech Creek) in Towns County, Georgia, U.S.A. Although prevalence and mean visible metacercariae were different in June, no difference was seen between the species in either measure of infection in August. Our results support earlier work that suggests that factors other than host phylogeny can be more important in influencing infection. [ABSTRACT FROM AUTHOR]

Praziquantel (PZQ) is currently the only approved drug for treating clonorchiasis, but its poor efficacy against Clonorchis sinensis larvae has highlighted the need to develop newer drugs. In this study, to address this challenge, we investigated the anti-parasitic efficacy of miltefosine (MLT), curcumin (CUR), and PZQ against C. sinensis metacercariae (CsMC), newly excysted juvenile worms (CsNEJs), and adults. Larvicidal effects of MLT and CUR surpassed those elicited by PZQ in vitro . These two drugs exerted their effect against both CsMC and CsNEJs in a dose- and time-dependent manner. To confirm the effect of these drugs in vivo , Syrian golden hamsters were orally infected with 100 CsMC and subsequently treated with MLT, CUR, or PZQ at 1 and 4 weeks post-infection (wpi). MLT and CUR reduced the worm recoveries at 1 and 4 wpi, indicating that these drugs were efficacious against both larvae and adult C. sinensis . PZQ was only efficacious against adult worms. Interestingly, both MLT and CUR showed lower levels of C. sinensis- specific IgG responses than the infection control group, implying that worm burden and bile IgG responses could be correlated. These results indicate that MLT and CUR are efficacious against both larval and adult stages of C. sinensis , thereby highlighting their potential for further development as alternative therapeutic options for clonorchiasis., Competing Interests: The authors declare no conflict of interest.

Clinostomum complanatum is a zoonotic parasite and can cause economic losses in fish farms. The parasite has been mostly reported in freshwater fish species but not in Garra rufa (Doctor fish) which is getting more popular for fish spa. This is the first report of yellow grub trematode C. complanatum infected with doctor fish (G. rufa) in the Southern Turkey. A total of 40 dead G. rufa, which were taken from a commercial firm, were examined. The parasite from fish were confirmed by morphologically and molecular methods (PCR and sequencing) using nuclear internal transcribed spacer gene marker (ITS 1). G. rufa were found to be infected by C. complanatum, with prevalence 90.0%, and a mean intensity of the infection 19.8. We observed that C. complanatum metacercariae were in the encysted form and excysted form in the infected fish, and the diameter of the metacercarial cysts was found to be between 0.15-2.3 mm. The parasites were measured as mean body length 4079±861 pm, mean body width 1463±244 pm, mean body length/body width 2.81±0.47. Internal transcribed spacer 2 (ITS2) gene were amplified for sequence and phylogenetic analyses and those sequences of metacercariae were also similar to the respective C. complanatum sequences in GenBank. Therefore, this study described the morphological characterization and molecular identification of C. complanatum for the first time from Garra rufa in Southern Turkey. [ABSTRACT FROM AUTHOR]

The diversity and taxonomy of metacercariae infecting freshwater amphipods of Poland are predominantly poorly known. During parasitological surveys of Gammarus pulex (Crustacea: Amphipoda) in the Pomeranian region of Poland in 2020 and 2021, some specimens of crustaceans were found to harbour metacercariae. Out of seven observed localities, metacercariae were found in the stream close to Krępa Słupska and the Lupawa River close to Smoldzino. They were morphologically studied and sequenced using universal eukaryotic primers that amplify V4–V5 regions of 18S rRNA. The BLAST analysis and phylogenetic reconstructions aid to define the affiliation of the revealed metacercariae within the Omphalometridae Looss, 1899. The further differential analysis based on morphologic information led to the conclusion that the metacercarial form studied herein represents Neoplagioglyphe megastomus (Baer, 1943). The degree of morphometric variations of taxonomic important features in populations from different geographic regions was followed up. The reported here form was characterized by a larger body size that was affected by the processing methods used in the present and previous studies. To our knowledge, this is the first report of Neoplagioglyphe megastomus in Poland and is the first molecular characterization of the worm.

Trematodes belonging to the family Echinostomatidae are food-borne parasites which cause echinostomiasis in animals and humans. This is a global public health issue, particularly in East and Southeast Asia. A method to detect the infective stage of Echinostomatidae species is required to prevent transmission to humans. In this study, a loop-mediated isothermal amplification coupled with a lateral flow dipstick (LAMP-LFD) assay was developed for visual detection of the metacercarial stage in edible snails of the genus Filopaludina from local markets in Thailand. The LAMP-LFD method can be performed within 70 min at a consistent temperature of 66 °C, and the results can be interpreted with the naked eye. The detection limits of the assay using Echinostoma mekongi , E. macrorchis , E. miyagawai and Hypoderaeum conoideum genomic DNA were equal between the four species at 50 pg/μL. A specificity evaluation demonstrated that the LAMP-LFD assay had no cross-reaction with another parasite (Thapariella species) or with the snail host species (Filopaludina martensi martensi , F. sumatrensis speciosa , and F. s. polygramma). Clinical test assessments were compared to microscopic examination in 110 edible snail samples. The clinical sensitivity and specificity of the tests were 84.62 % and 100 %, respectively, with a strong level of agreement based on the kappa statistic and the results of both methods were not significantly different (p > 0.05) per McNemar's test. The test successfully developed in this study may be useful for the detection of the metacercarial stage in edible snails for epidemiological investigations, control, surveillance, and to prevent future echinostomiasis health issues. • The assay can amplify DNA of four Echinostomatidae species in a single tube. • The results can be obviously visualized with the naked eye. • The assay could be utilized to diagnose Echinostomatidae infection in edible snail. • This study is the first LAMP-LFD assay for Echinostomatidae detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • First morphological identification of Leucochloridiid larval stages in Argentina. • First molecular identification of Leucochloridiid metacercaria from South America. • Amplified nuclear (28S) and mitochondrial (COI) regions for Leucochloridium sp. • All species delimitation methods recognize Leucochloridium sp. as a distinct species. • The described larval stages do not fit any South American Leucochloridium species. Trematodes of the genus Leucochloridium exhibit an unusual transmission strategy among mollusks (intermediate host). The fully developed sporocyst, housing encysted metacercariae, displays vivid coloration and rhythmic activity in the snail's tentacle, mimicking insect larvae. These strategies attract insectivorous birds, their final hosts, thereby increasing the chances of completing their life cycle. In South America, the reports of adults and larval stages of Leucochloridium are scarce. Brown-banded broodsac of Leucochloridium sp. were obtained from Omalonyx unguis collected in a shallow lake from Corrientes Province, Argentina. Here, we morphologically characterized the larval stages (broodsac and metacercaria), identified the parasite through DNA sequences from nuclear 28S-rRNA (28S) and the mitochondrial cytochrome c oxidase I (COI) genes, and explored its evolutionary affinities with the Leucochloridium species available in GenBank. The present broodsac displays brown bands, with a yellowish background in the first two-thirds and yellowish-white in the last third. Based on morphological comparisons, the broodsac and metacercaria described in this study could not be conclusively categorized under any known South American species of Leucochloridium. In relation to the phylogenetic reconstructions, Leucochloridium sp. consistently clustered with L. perturbatum , and species delimitation analyses resulted in recognized Leucochloridium sp. from Argentina as a distinct species. The DNA sequences obtained in this study constitute the first genetic data generated for sporocyst broodsacs in South America. Future studies, incorporating morphology, genetic, and biological data, will be essential for both species identification and the elucidation of leucochloridiid diversity in the region. [ABSTRACT FROM AUTHOR]

In the fall of 2021, California Department of Fish and Wildlife reported larval and adult California giant salamanders (Dicamptodon ensatus Eschscholtz, 1833) with skin lesions at multiple creeks in Santa Clara and Santa Cruz Counties, California, USA. Field signs in both stages included rough, lumpy textured skin, and larvae with tails that were disproportionately long, flat, wavy, and flaccid. Presence of large-bodied larvae suggested delayed metamorphosis, with some larvae having cloudy eyes and suspected blindness. To determine the cause of the disease, three first-of-the-year salamanders from one location were collected, euthanized with 20% benzocaine, and submitted for necropsy to the U.S. Geological Survey, National Wildlife Health Center. Upon gross examination, all salamanders were emaciated with no internal fat stores, and had multiple pinpoint to 1.5-mm diameter raised nodules in the skin over the body, including the head, gills, dorsum, ventrum, all four limbs, and the tail; one also had nodules in the oral cavity and tongue. Histologically all salamanders had multiple encysted metacercariae in the dermis, subcutis, and skeletal muscles of the head, body, and tail that were often associated with granulomatous and granulocytic inflammation and edema. A small number of encysted metacercariae or empty cysts were present in the gills with minimal inflammation, and rarely in the kidney with no associated inflammation. Morphology of live metacercariae (Trematoda: Heterophyiidae), and sequencing of the 28S rRNA gene identified a species of Euryhelmis (Poche, 1926). Artificial digestion of a 1.65 g, decapitated, eviscerated carcass yielded 773 metacercariae, all of similar size and morphology as the live specimens. Based on these findings, the poor body condition of these salamanders was concluded to be due to heavy parasite burden. Environmental factors such as drought, increased temperature, and overcrowded conditions may be exacerbating parasite infections in these populations of salamander. [Display omitted] • Morbidity and mortality event affecting California giant salamanders in California. • Salamanders had rough, lumpy skin, abnormal tails, and delayed metamorphosis. • Euryhelmis sp. metacercariae infection in dermis, subcutis, and skeletal muscles. • Environmental factors may exacerbate parasite infection in these salamanders. [ABSTRACT FROM AUTHOR]

The diversity and taxonomy of metacercariae infecting freshwater amphipods of Poland are predominantly poorly known. During parasitological surveys of Gammarus pulex (Crustacea: Amphipoda) in the Pomeranian region of Poland in 2020 and 2021, some specimens of crustaceans were found to harbour metacercariae. Out of seven observed localities, metacercariae were found in the stream close to Krępa Słupska and the Lupawa River close to Smoldzino. They were morphologically studied and sequenced using universal eukaryotic primers that amplify V4-V5 regions of 18S rRNA. The BLAST analysis and phylogenetic reconstructions aid to define the affiliation of the revealed metacercariae within the Omphalometridae Looss, 1899. The further differential analysis based on morphologic information led to the conclusion that the metacercarial form studied herein represents Neoplagioglyphe megastomus (Baer, 1943). The degree of morphometric variations of taxonomic important features in populations from different geographic regions was followed up. The reported here form was characterized by a larger body size that was affected by the processing methods used in the present and previous studies. To our knowledge, this is the first report of Neoplagioglyphe megastomus in Poland and is the first molecular characterization of the worm. [ABSTRACT FROM AUTHOR]

Understanding the host specificity of trematode larvae is vital in predicting the mode of trophic level transfer of trematode parasites and their evolution. In this study, six species of trematode metacercariae, Eumegacetes sp., Orthetrotrema monostomum, Ganeo tigrinus, Mehraorchis sp., Pleurogenoides sp. and Phyllodistomum sp. infecting the larvae of the odonate family Libellulidae from the water bodies in the Wayanad region of the Western Ghats are recorded. The prevalence of infection of these metacercariae was 5.8%, 2.0%, 10.4%, 9.1%, 2.6% & 1.3%, respectively. Further, the mean intensity of infection was estimated to be 4.44, 1.67, 5.38, 6.21, 6.0 & 17.5 and the mean abundance 0.26, 0.03, 0.56, 0.56, 0.16 & 0.23 respectively. [ABSTRACT FROM AUTHOR]

• A clonorchiasis epidemic model with time delays is proposed. • The clonorchiasis transmission case in Guangxi Province, China is studied. • The results are beneficial to the control of clonorchiasis for Guangxi. • The analysis and simulation methods are also applicable to other vector-borne diseases models. Clonorchiasis is a serious food borne parasitic disease caused by clonorchis sinensis that is transmitted via snails to freshwater fish, and then to humans and other mammals. Based on the life cycle clonorchis sinensis, we present a mathematical model of clonorchiasis with three time delays which represent the maturation period of metacercaria developing adult flukes within human host, the period of eggs developing cercariae within snail host and the period of cercariae developing metacercaria within fish host.The basic reproduction number R 0 for this model is introduced. We establish a threshold type result on the global dynamics in terms of R 0. More precisely, the disease-free equilibrium is globally attractive if R 0 < 1 ; while the disease is uniformly persistent if R 0 > 1. Considering the above-mentioned periods can also be modelled by introducing the corresponding exposed classes, we also study the dynamical behavior of the corresponding model without delays. Numerically, we study the clonorchiasis transmission case in Guangxi Pronvince, China. Some control strategies are provided to prevent clonorchiasis spread in Guangxi by numerical analysis. [ABSTRACT FROM AUTHOR]

Copyright of Parasite (1252607X) is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In early September 2019, a morbidity and mortality event affecting California tiger salamanders (Ambystoma californiense) and Santa Cruz long-toed salamanders (Ambystoma macrodactylum croceum) in late stages of metamorphosis was reported at a National Wildlife Refuge in Santa Cruz County, California, U.S.A. During the postmortem disease investigation, severe integumentary metacercarial (Class: Trematoda) infection, associated with widespread skin lesions, was observed. Planorbid snails collected from the ponds of the refuge within seven days of the mortality event were infected with Ribeiroia ondatrae, a digenetic trematode that can cause malformation and death in some amphibians. We suggest sustained seasonal high-water levels due to active habitat management along with several years of increased rainfall led to increased bird visitation, increased over-wintering of snails, and prolonged salamander metamorphosis, resulting in a confluence of conditions and cascading of host-parasite dynamics to create a hyper-parasitized state. [Display omitted] • Mortality event in wild endangered salamanders in California. • Infection with Ribeiroia ondatrae caused severe fatal skin lesions. • Sustaining water levels may increase parasite transmission. [ABSTRACT FROM AUTHOR]

Purpose: Cardiocephaloides comprises strigeid trematodes that represent a small genus. In this study, metacercaria identified as Cardiocephaloides sp. was collected from the Gangetic leaffish Nandus nandus from the Ganga River at Bairaj, Bijnor (29º01'N, 77º45'E) in the state of Uttar Pradesh (U.P.), India. Partial DNA sequences of the internal transcribed spacers (ITS1-5.8S-ITS2) and 28S gene of nuclear ribosomal DNA were generated and compared with available sequences of Cardiocephaloides species from Genbank database. Methods: Encysted metacercariae of Cardiocephaloides sp. were collected from Nandus nandus were processed, identified and documented using morphological methods. The ITS1-5.8S-ITS2 cluster and 28S gene of ribosomal DNA of metacercariae were also sequenced and used for phylogenetic analysis. Results: The infections of brain parasites are poorly understood in India and if studies are available, they are not properly described. During this study, the species collected were found belongs to the genus Cardiocephaloides. Metacercariae of Cardiocephaloides sp. is distinguished morphologically from others that also harbor brain by the presence of having an egg shape cyst and body elongate oval in shape with well-developed anterior part. The metacercariae are identified by matching of molecular sequence data and is compared to other species of Strigeidae. Conclusion: This is the first record of metacercaria of Cardiocephaloides sp. from India. This molecular data from the present study will provide future comparative insights into species of Cardiocephaloides and its close affiliation to other congeners from different geographical areas. [ABSTRACT FROM AUTHOR]

Manila clam Ruditapes philippinarum is present at high rates of density in tidal flats in Cheonsu Bay on the west coast of Korea, where clams often exhibit mass mortalities in late summer. We monitored the pathologic condition of clams at Hwangdo tidal flat (HD) to understand the parasitic impacts on clam fitness. Manila clams were fully ripe in July and spawned during August and September, as the histology indicated. The histology revealed that clams in HD tidal flats were heavily infected by the protozoa parasite Perkinsus olseni, as the monthly prevalence ranged from 53% (September) to 93% (August). In addition, Manila clams were co-infected by the metazoan parasite Cercaria tapetis and Parvatrema duboisi with the prevalence of 0-33% and 0-14%, respectively. Massive hemocyte infiltration and subsequent inflammation were commonly observed from the gills of P. olseni infected clams. Clusters of P. olseni trophozoites and heavy hemocyte infiltration were also observed from the female gonad, suggesting that P. olseni interferes with host gonad maturation. The larval trematode occupied almost the entire host gonad, resulting in gonad castration. In addition, Metacercaria of P. duboisi were observed from the subsurface of the mantle. Ray’s fluid thioglycollate medium assay (RFTM) indicated that clams collected in August and September contained approximately 4.0x106 P. olseni cells/g gills. Condition Index (CI) declined gradually from spring to early summer, and the decline in CI was interpreted as a consequence of the heavy parasitism, as the parasites drain the host’s net energy to be used in somatic growth and gamete production. [ABSTRACT FROM AUTHOR]

The purpose of the research is to determine quantitative indicators of infection of fish of the cyprinid family with opisthorchid metacercariae in the rivers of Khanty-Mansi Autonomous Okrug – Yugra.Materials and methods. The researches were done for the Bolshoy Yugan, Vynga, Tromyogan, Pim, Ob, Irtysh rivers in 2012–2018. Fish species was identified under the identification guide, and their age was determined by their scales. The fish were examined for the presence of metacercariae of opisthorchids by compression of the spinal muscles followed by microscopy according to the generally accepted technique.Results and discussion. The extent of infection of ide by opisthorchid metacercariae ranged from 11.2–87.4% in different rivers, spruce – 35.6–94.1%. With the age of fish, the extent of infection and the abundance index increase due to the accumulation of infection. There are species of fish identified that are less vulnerable to the infection. The highest rate of fish infection was observed in the Irtysh River.

The purpose of the research description of larvae Gymnophallus rebecqui (Bartoli, 1983) morphology from bivalve mollusks Abra segmentum Recluz, 1843 and Cerastoderma glaucum Poiret, 1789 in the Black Sea; to study seasonal abundance of G. rebecqui in the Black Sea.Materials and methods. During 2011–2012 years, 875 samples of bivalves A. segmentum and 440 samples of C. glaucum were investigated from two biotopes Sevastopol water area. The samples were selected every month. All mollusks tissues were investigated for parasites with a compressor method over binocular at increase × 98. The detected cercarias and metacercarias were fixed for life and dyed with acetous carmine, and after dehydration in a series of alcohol and clarification in clove oil were placed in Canada balsam. One of the generally accepted systems of trematodes measuring was used in the work. Measurings were made on microscope XY-B2 with с a film camera at increase × 1000. The images were made in redactor of vector graphics Inkscape 0.48.2-1.Results and discussion. For the first time, at the estuary of the river Chernaya and in the Black Sea, larvae of trematodes G. rebecqui have been found in mollusks A. segmentum and C. glaucum. A. segmentum has appeared to be not only the second intermediate host for such trematode in the studied ecosystem but also parthenitas G. rebecqui were detected in it. According to the main diagnostic and morphological features, the analyzed larvae of trematodes were identified as G. rebecqui: the Y-shaped secretory cyst without diverticula in cercarias, and the absence of the ventral hole and of accumulation of prostatic cells over the ventral sucker at the metacercaria stage. The morphometric features of the cercarias and metacercarias of trematodes G. rebecqui, which were studied by us, are within the boundaries known for larvae of this type parasitizing in mollusks A. segmentum and C. glaucum off the coasts of France, Great Britain and the Black Sea. An infection peak of mollusks C. glaucum with metacercarias G. rebecqui was observed in late summer and early autumn in both regions.

Cyprinid fishes are commonly acted as second intermediate hosts of Opisthorchis viverrini and Haplorchis spp. This research investigated the prevalence and intensity of both parasites in cyprinid species. This process is regularly used as a guideline for disease surveillance and as a preventive measure in the Upper Northeastern region of Thailand. Fish samples were collected from both lentic and lotic water sources between November 2020 and October 2021, and classified them by their species. Acid pepsin-HCL solution was used to digest the individual samples and create a build-up of precipitate in order to view metacercariae using a stereomicroscope. A total of 3583 fish were caught and classified into 23 species. Out of these fish, 5.49% of them were found O. viverrini , 26.54% Haplorchis taichui , 10.04% Haplorchis pumilio , and 9.29% Haplorchoides sp. Ten species of fish were observed to have been infected with O. viverrini . Amongst the collected fish, M. obtusirostris had the highest prevalence of infection at 52.94%, while B. gonionotus had only 1.71%. The prevalence of O. viverrini infection was highest at 27.41% in Udon Thani Province. No prevalence of O. viverrini infection was observed in Bueng Kan Province. High prevalence of O. viverrini infection in cyprinid fishes was found in both lentic and lotic water sources in almost all provinces in the region. The prevalence of infection and intensity depended on the fish species and fish habitats., Competing Interests: The authors declare that they have no competing interests., (© 2024 The Authors. Published by Elsevier Ltd on behalf of World Federation of Parasitologists.)

The one‐stripe spiny eel (Macrognathus aral, Bloch & Schneider, 1801) under the family Mastacembelidae, a native ornamental fish, were collected from the freshwater ponds and canals of West Bengal, with a purpose to raise the colony as ornamental fish broodstock. During acclimatization, fish were found to be lethargic and reluctant to consume feed followed by the appearance of deep wounds and red patches on the ventral part of the body surface. There was a mortality of 40.49% of affected fish within the next 48 hours. Post‐mortem examinations revealed the presence of metacercariae inside the body cavity and on internal organs, spreading up to the buccal cavity. The abundance of the parasite was 15 to 36 numbers per fish. The length of the metacercaria varied from 5.2 mm to 9.8 mm. The metacercariae were identified as Clinostomum complanatum by light microscopy. Further, molecular confirmation of identification was done using PCR amplification and sequencing of the 18S RNA gene. This is the first report of metacercarial infestation of Clinostomum complanatum with molecular confirmation in indigenous M. aral with high ornamental value. [ABSTRACT FROM AUTHOR]

Clinostomum Leidy, 1856 (Trematoda: Clinostomidae) is a cosmopolitan, zoonotic genus of fluke that has been poorly studied in an Australian setting. Following previous reports of reservoir fish in Australian fish ponds being heavily infected with Clinostomum metacercaria, the current study was conducted to determine the specific identity of Clinostomum sp. in inland Australia, by examining and characterizing parasites collected from a potential definitive host, cormorants. A total of 33 parasite specimens belonging to the genus Clinostomum were collected from two cormorants (little black cormorants, Phalacrocorax sulcirostris) that were collected from the Narrandera Fisheries Research Centre, New South Wales, at the same locality where metacercaria of Clinostomum sp. have been reported in fish. All specimens in our study were immature adults. Clinostomum specimens with similar morphology have been identified as C. complanatum in the past, based on their morphological characteristics. However, phylogenetic analyses based on the ITS sequence data in the present study suggest they are the same as the Clinostomum sp. previously reported from carp gudgeons (Hypseleotris spp.) from the same farm, and distinct from C. complanatum. The ITS sequences obtained from the specimens in the present study were most similar to those belonging to C. phalacrocoracis (never reported in Australia). Our specimens formed a distinct clade on the phylogenetic tree and their specific identity awaits until fully mature specimens are described in future studies. [ABSTRACT FROM AUTHOR]

In the southern Appalachian Mountains, U.S.A., the trematode Metagonimoides oregonensis, a parasite of raccoons and possibly mink, utilizes larvae of lungless salamanders as second intermediate hosts, most frequently using the salamander Desmognathus quadramaculatus. We tested whether there was a difference in parasite infection between this salamander and its sympatric, cryptic congener, Desmognathus folkertsi, in northern Georgia. Whereas larval D. quadramaculatus had a prevalence of 100% with intensities ranging from 18 to over 1,000, none of the D. folkertsi had visible metacercariae. These results indicate that M. oregonensis is more host-specific in salamander second intermediate hosts in the southern Appalachians than previously reported. [ABSTRACT FROM AUTHOR]

Background: The genus Nematostrigea comprises trematodes parasitising in fish-eating birds of Europe, Africa, and North America. Their life cycle is unknown. Purpose: To provide the first description of metacercariae of Nematostrigea serpens serpens, a nominative subspecies of the type species of Nematostrigea, and to record metacercaria of Nematostrigea vietnamiensis, with molecular data. Methods: Encysted metacercariae of N. serpens serpens and N. vietnamiensis were collected from fish in Russia and Vietnam, respectively, and were processed, identified, and documented using standard morphological techniques. The 28S rRNA gene of metacercariae of both species and the cox1 gene of metacercariae an earlier studied adult of N. serpens serpens were sequenced and used for phylogenetic analysis. Results: Metacercaria of N. serpens serpens have a spatulate body with a foliate forebody and a short hindbody, two long lateral rectilinear pseudosuckers, and the holdfast organ with bifurcated anterior and entire posterior external lobes. The analysis of the cox1and 28S rRNA gene sequences unequivocally showed the conspecificity of metacercariae and adult stage of N. serpens serpens. Based on the 28S rRNA gene sequence-based phylogenetic analysis, the genus Nematostrigea is a sister taxon to the group of strigeid genera Cotylurus + Ichthyocotylurus. Morphological and phylogenetic data demonstrated that N. vietnamiensis does not belong to the genus Nematostrigea and is possibly be affiliated with the crassiphialine trematodes. Conclusion: This is the first record of metacercariae of N. serpens serpens. N. vietnamiensis, renamed Prodiplostomulum vietnamiense comb. nov., must be moved to the crassiphialine 'Prodiplostomulum'-type metacercariae group [ABSTRACT FROM AUTHOR]

Metacercariae of the zoogonid trematode Steganoderma cf. eamiqtrema ex crab Chionoecetes bairdi caught in the Sea of Okhotsk were described using morphological and molecular-genetic (ITS2 region, 28S rRNA and nd1 genes) data. These are the first molecular-genetic data for the genus Steganoderma. The studied trematodes differed from S. eamiqtrema in having a much larger body size. The phylogenetic analysis based on the 28S rRNA gene supported neither the current taxonomic hypothesis that Steganoderma belongs to the subfamily Lepidophyllinae nor the earlier views that the Steganodermatinae and the Lecithostaphylinae are synonymous. The topology of the phylogenetic tree shows that the Steganodermatinae and the Lecithostaphylinae are independent subfamilies. However, morphological differences between them are obscure. Until morphological evidence for the Steganodermatinae is found, we propose to distinguish the subfamily Lepidophyllinae sensu stricto with the genera Lepidophyllus and Urinatrema, and the subfamily Lecithostaphylinae sensu lato uniting all the other former lepidophyllines. Thus, for now, we propose to consider the Steganodermatinae as a conditional synonym for Lecithostaphylinae sensu lato. [ABSTRACT FROM AUTHOR]

Life cycle stages, including daughter sporocysts, cercariae, and metacercariae, of Parvatrema duboisi (Dollfus, 1923) Bartoli, 1974 (Digenea: Gymnophallidae) have been found in the Manila clam Ruditapes philippinarum from Aphaedo (Island), Shinan-gun, Jeollanam-do, Korea. The daughter sporocysts were elongated sac-like and 307-570 (av. 395) μm long and 101-213 (av. 157) μm wide. Most of the daughter sporocysts contained 15-20 furcocercous cercariae each. The cercariae measured 112-146 (av. 134) μm in total length and 35-46 (av. 40) μm in width, with 69-92 (av. 85) μm long body and 39-54 (av. 49) μm long tail. The metacercariae were 210-250 (av. 231) μm in length and 170-195 (av. 185) μm in width, and characterized by having a large oral sucker, genital pore some distance anterior to the ventral sucker, no ventral pit, and 1 compact or slightly lobed vitellarium, strongly suggesting P. duboisi. The metacercariae were experimentally infected to ICR mice, and adults were recovered at day 7 post-infection. The adult flukes were morphologically similar to the metacercariae except in the presence of up to 20 eggs in the uterus. The daughter sporocysts and metacercariae were molecularly (ITS1-5.8S rDNA-ITS2) analyzed to confirm the species, and the results showed 99.8-99.9% identity with P. duboisi reported from Kyushu, Japan and Gochang, Korea. These results confirmed the presence of various life cycle stages of P. duboisi in the Manila clam, R. philippinarum, playing the role of the first as well as the second intermediate host, on Aphae-do (Island), Shinan-gun, Korea. [ABSTRACT FROM AUTHOR]