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Simple Summary: The ultrastructural study of spermatozoa in parasites such as the Digenea provides data that, like classical morphological features, biological data, and genetic characterization, can help achieve a better understanding of phylogenetic relationships at different taxonomic levels. In this context, the present study provides the first ultrastructural data of spermatozoa in a digenean species of the genus Artyfechinostomum. These results increase the database of ultrastructural spermatological characteristics within the group of Echinostomatoidea. The comparison of these features with the existing data allows us to establish a coherent model of the sperm cell for species belonging to this superfamily. The study of sperm characteristics has proven useful for elucidating interrelationships in several groups of Platyhelminthes, such as digeneans. Thus, in the present work, the ultrastructural organization of the mature spermatozoon of the digenean Artyfechinostomum malayanum (Echinostomatidae), a parasite of Rattus norvegicus (Rodentia: Muridae) from Dong Thap Province, Vietnam, was investigated for the first time using transmission electron microscopy. The male gamete of A. malayanum exhibits two axonemes of different lengths, showing the 9 + '1' pattern of the Trepaxonemata, a nucleus, two mitochondria, two lateral expansions, two bundles of parallel cortical microtubules, external ornamentation, spine-like bodies, and granules of glycogen. Thus, the mature spermatozoon follows a Type V sperm model proposed for digeneans. We also highlight some noteworthy characteristics in Echinostomatidae with possible phylogenetic implications, such as two lateral expansions in the anterior region of the spermatozoon and two mitochondria. [ABSTRACT FROM AUTHOR]

Five newly obtained nuclear ribosomal transcription unit (rTU) sequences from Echinostomatidae and Echinochasmidae are presented. The inter- and intrafamilial relationships of these and other families in the suborder Echinostomata are also analyzed. The sequences obtained are the complete rTU of Artyfechinostomum malayanum (9,499 bp), the near-complete rTU of Hypoderaeum conoideum (8,076 bp), and the coding regions (from 5’-terminus of 18S to 3’-terminus of 28S rRNA gene) in Echinostoma revolutum (6,856 bp), Echinostoma miyagawai (6,854 bp), and Echinochasmus japonicus (7,150 bp). Except for the longer first internal transcribed spacer (ITS1) in Echinochasmus japonicus, all genes and spacers were almost identical in length. Comprehensive maximum-likelihood phylogenies were constructed using the PhyML software package. The datasets were either the concatenated 28S + 18S rDNA sequences (5.7–5.8 kb) from 60 complete rTUs of 19 families or complete 28S sequences only (about 3.8–3.9 kb) from 70 strains or species of 22 families. The phylogenetic trees confirmed Echinostomatoidea as monophyletic. Furthermore, a detailed phylogeny constructed from alignments of 169 28S D1−D3 rDNA sequences (1.1–1.3 kb) from 98 species of 50 genera of 10 families, including 154 echinostomatoid sequences (85 species/42 genera), clearly indicated known generic relationships within Echinostomatidae and Echinochasmidae and relationships of families within Echinostomata and several other suborders. Within Echinostomatidae, Echinostoma, Artyfechinostomum, and Hypoderaeum appeared as monophyletic, while Echinochasmus (Echinochasmidae) was polyphyletic. The Echinochasmidae are a sister group to the Psilostomidae. The datasets provided here will be useful for taxonomic reappraisal as well as studies of evolutionary and population genetics in the superfamily Echinostomatoidea, the sole superfamily in the suborder Echinostomata. [ABSTRACT FROM AUTHOR]

Species of the family Echinostomatidae use diverse gastropod taxa as first intermediate hosts. However, identification of echinostomatid larvae often proves difficult because of incomplete information on their life cycles and lack of molecular data that can link larvae to the corresponding known adults. Here, echinostomatids that were isolated from freshwater limpets in South Africa were described using light and scanning electron microscopy, and ribosomal (28S, ITS, and 18S) and mitochondrial (cox1) DNA sequences. The analyses revealed three species: Petasiger radiatus , Petasiger sp. and Echinostomatidae gen. sp. Considering the close morphological resemblance between cercariae of Petasiger spp. the current species were compared with data from literature. The results showed that cercarial size is generally unsuitable for species discrimination. The numbers of flame cells and refractile granules in the excretory system, and penetration gland cell patterns, may indicate, but do not prove species identity. Although papillary patterns were distinct between species, papillae were clearly discernible only using scanning electron microscopy and are known for only a few species. Phylogenetic reconstruction indicated that 28S rDNA sequences of Petasiger on GenBank are for P. exaeretus , P. phalacrocoracis , P. radiatus , and six unnamed species. Furthermore, the results revealed that multiple ITS rDNA and cox1 sequences labelled as Stephanoprora amurensis and P. phalacrocoracis on GenBank, are from isolates whose identities are questionable. Echinostomatidae gen. sp. could not be assigned to any currently known genus. Expansion of the genetic database of the family Echinostomatidae is necessary for the delineation of putative species and elucidation of intergeneric relationships. [ABSTRACT FROM AUTHOR]

The purpose of the research is the morphological and molecular identification of trematodes found in the intestines of migratory waterfowl with subsequent taxonomic evaluation.Materials and methods. Mature specimens of trematodes were collected from the intestines of waterfowl (Fulica atra and Aythya ferina) shot during the ecological-faunistic monitoring in the southern part of the Primorsky krai. Preliminary morphological analyze revealed that trematodes belong to the Echinostomatidae family. The whole-mounts of worms from F. atra were prepared using standard methods with alum carmine. Divergent domains of 28S ribosomal RNA gene were sequenced and used to determine systematic position and relationships of discovered species of echinostome by reconstructing Bayesian and Maximum likelihood trees.Results and discussion. Trematodes found in the coots' intestine, should be described as Neomoliniella longicorpa in the new genus Neomoliniella gen. et sp. nov., which is reliably confirmed by morphological and genetics data. Another cryptic echinostomatid species sister to Neomoliniella gen. nov., and probably representing the separate unknown genus, was demonstrated only on the phylogenetic reconstructions and confirmed by large genetic distances. Currently, this taxon is indicated as Echinostomatidae gen. sp. and more evidence is needed for its validation. We also report about the first detection of Echinostoma paraulum from A. ferina in the south of the Russian Far East. The biology, morphology of each life cycle stage of newly described species of worms should be investigated to test not only their scientific but also medical significance. For the first time in the history of the group, dichotomous keys for eight families of the superfamilyEchinostomatoidea and, to date, the largest of all previously known for the family Echinostomatidae identification chart – dichotomous keys for the identification of 27 Palearctic genera were compiled.

In the present paper, we review two of the most neglected intestinal food-borne trematodiases: echinostomiasis, caused by members of the family Echinostomatidae, and gastrodiscoidiasis produced by the amphistome Gastrodiscoides hominis. Both parasitic infections are important intestinal food-borne diseases. Humans become infected after ingestion of raw or insufficiently cooked molluscs, fish, crustaceans, amphibians or aquatic vegetables. Thus, eating habits are essential to determine the distribution of these parasitic diseases and, traditionally, they have been considered as minor diseases confined to low-income areas, mainly in Asia. However, this scenario is changing and the population at risk are currently expanding in relation to factors such as new eating habits in developed countries, growing international markets, improved transportation systems and demographic changes. These aspects determine the necessity of a better understanding of these parasitic diseases. Herein, we review the main features of human echinostomiasis and gastrodiscoidiasis in relation to their biology, epidemiology, immunology, clinical aspects, diagnosis and treatment. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome (mitogenome or mtDNA) of the trematode Echinostoma malayanum Leiper, 1911 was fully determined and annotated. The circular mtDNA molecule comprised 12 protein-coding genes (PCGs) (cox1 − 3, cob, nad1 − 6, nad4L, atp6), two mitoribosomal RNAs (MRGs) (16S or rrnL and 12S or rrnS), and 22 transfer RNAs (tRNAs or trn), and a non-coding region (NCR) rich in long and short tandem repeats (5.5 LRUs/336 bp/each and 7.5 SRUs/207 bp/each). The atp8 gene is absent and the 3′ end of nad4L overlaps the 5′ end of nad4 by 40 bp. Special DHU-arm missing tRNAs for Serine were found for both tRNASer1(AGN) and tRNASer2(UCN). Codons of TTT (for phenylalanine), TTG (for leucine), and GTT (for valine) were the most, and CGC (for Arginine) was the least frequently used. A similar usage pattern was seen in base composition, AT and GC skewness for PCGs, MRGs, and mtDNA* (coding cox3 to nad5) in E. malayanum and Echinostomatidae. The nucleotide use is characterized by (T > G > A > C) for PCGs/mtDNA*, and by (T > G ≈ A > C) for MRGs. E. malayanum exhibited the lowest genetic distance (0.53%) to Artyfechinostomum sufrartyfex, relatively high to the Echinostoma congeners (13.20–13.99%), higher to Hypoderaeum conoideum (16.18%), and the highest to interfamilial Echinochasmidae (26.62%); Cyclocoelidae (30.24%); and Himasthlidae (25.36%). Topology indicated the monophyletic position between E. malayanum/A. sufrartyfex and the group of Echinostoma caproni, Echinostoma paraensei, Echinostoma miyagawai, and Echinostoma revolutum, rendering Hypoderaeum conoideum and unidentified Echinostoma species paraphyletic. The strictly closed genomic/taxonomic/phylogenetic features (including base composition, skewness, codon usage/bias, genetic distance, and topo-position) reinforced Echinostoma malayanum to retake its generic validity within the Artyfechinostomum genus. [ABSTRACT FROM AUTHOR]

Life cycles, and morphological and molecular data were obtained for Echinostoma chankensis nom. nov., Echinostoma cinetorchis, Echinostoma miyagawai and Isthmiophora hortensis from East Asia. It was established that, based on both life cycle and morphology data, one of the trematodes is identical to the worms designated as Euparyphium amurensis. Genetic data showed that this trematode belongs to Echinostoma. The complex data on biological, morphological and genetic characterizations establish that the distribution of the morphologically similar species, I. hortensis and Isthmiophora melis, in the Old World are limited by the East Asian and European regions, respectively. Data on mature worms of East Asian E. miyagawai revealed morphological and genetic identity with E. miyagawai from Europe. However, E. miyagawai from Europe differs from E. miyagawai from the type locality (East Asia) in terms of reaching maturity and the morphology of cercariae. These data indicate that the European worm, designated E. miyagawai, does not belong to this species. An analysis of the phylogenetic relationships of Echinostomatidae was conducted based on the 28S, ITS2 and nad1 markers. Analysis using the nad1 gene for the known representatives of Echinostomatidae is carried out for the first time, showing that nuclear markers are ineffective separate from mitochondrial ones. [ABSTRACT FROM AUTHOR]

Co-infections of mammalian hosts with intestinal helminths and bacterial pathogens are common, especially in areas with inadequate sanitation. Interactions between co-infecting species and host microbiota can cause significant changes in host immunity, disease severity, and pathogen transmission, requiring unique treatment for each case. A greater understanding of the influences of parasite-bacteria co-infections will improve diagnosis and therapeutic approaches to control infectious diseases. To study the influence of the trematode parasite Echinostoma caproni on commensal and pathogenic bacteria in the mouse gut, we examined the abundance of intestinal lactic acid bacteria and Salmonella enterica serovar Typhimurium in control mice not exposed to E. caproni (P–) or S. Typhimurium (S–), E. caproni–infected (P+S–), S. Typhimurium-infected (P –S+), and E. caproni–S. Typhimurium co-infected (P+S+) mice, and determined bacterial burdens in the livers and spleens of the P–S+ and P+S+ mice. We also examined a subset of P+S– and P+S+ mice for survival and the relative location of E. caproni in the small intestine. The numbers of presumptive lactic acid bacteria were significantly higher in the P+S+ and P–S+ mice compared to the uninfected mice, and S. Typhimurium colonization in the liver and spleen was significantly reduced in the P+S+ mice compared to the P–S+ mice. Echinostoma caproni were located anteriorly in the intestine of P+S– mice, while in the P+S+ mice, the parasites were distributed more posteriorly. Survival of E. caproni was unaffected in either group. The results of our study suggest that E. caproni facilitates a higher abundance of presumptive lactic acid bacteria in the mouse intestine and reduces colonization of S. Typhimurium in the liver and spleen of the co-infected host. [ABSTRACT FROM AUTHOR]

The study of priority effects with respect to coinfections is still in its infancy. Moreover, existing coinfection studies typically focus on infection outcomes associated with exposure to distinct sets of parasite species, despite that functionally and morphologically similar parasite species commonly coexist in nature. Therefore, it is important to understand how interactions between similar parasites influence infection outcomes. Surveys at seven ponds in northwest Pennsylvania found that multiple species of echinostomes commonly co-occur. Using a larval anuran host (Rana pipiens) and the two most commonly identified echinostome species from our field surveys (Echinostoma trivolvis and Echinoparyphium lineage 3), we examined how species composition and timing of exposure affect patterns of infection. When tadpoles were exposed to both parasites simultaneously, infection loads were higher than when exposed to Echinoparyphium alone but similar to being exposed to Echinostoma alone. When tadpoles were sequentially exposed to the parasite species, tadpoles first exposed to Echinoparyphium had 23% lower infection loads than tadpoles first exposed to Echinostoma. These findings demonstrate that exposure timing and order, even with similar parasites, can influence coinfection outcomes, and emphasize the importance of using molecular methods to identify parasites for ecological studies. [ABSTRACT FROM AUTHOR]

The complete mitochondrial sequence of 17,030 bp was obtained from Echinostoma revolutum and characterized with those of previously reported members of the superfamily Echinostomatoidea, i.e. six echinostomatids, one echinochasmid, five fasciolids, one himasthlid, and two cyclocoelids. Relationship within suborders and between superfamilies, such as Echinostomata, Pronocephalata, Troglotremata, Opisthorchiata, and Xiphiditata, are also considered. It contained 12 protein-coding, two ribosomal RNA, 22 transfer RNA genes and a tandem repetitive consisting non-coding region (NCR). The gene order, one way-positive transcription, the absence of atp8 and the overlapped region by 40 bp between nad4L and nad4 genes were similar as in common trematodes. The NCR located between tRNAGlu (trnE) and cox3 contained 11 long (LRUs) and short repeat units (SRUs) (seven LRUs of 317 bp, four SRUs of 207 bp each), and an internal spacer sequence between LRU7 and SRU4 specifying high-level polymorphism. Special DHU-arm missing tRNAs for Serine were found for both tRNAS1(AGN) and tRNAS2(UCN). Echinostoma revolutum indicated the lowest divergence rate to E. miyagawai and the highest to Tracheophilus cymbius and Echinochasmus japonicus. The usage of ATG/GTG start and TAG/TAA stop codons, the AT composition bias, the negative AT-skewness, and the most for Phe/Leu/Val and the least for Arg/Asn/Asp codons were noted. Topology indicated the monophyletic position of E. revolutum to E. miyagawai. Monophyly of Echinostomatidae and Fasciolidae was clearly solved with respect to Echinochasmidae, Himasthlidae, and Cyclocoelidae which were rendered paraphyletic in the suborder Echinostomata. [ABSTRACT FROM AUTHOR]

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]

The aim of the research is to study the distribution of trematodes of the family Echinostomatidae among various species of game birds in the North-East of Kazakhstan. Helminths were collected using the complete helminthological autopsy method according to K. I. Scriabin. The species affiliation of trematodes was determined according to the determinant of K. M. Ryzhikov. Statistical processing of the obtained materials was carried out in accordance with the recommendations of G. F. Lakin. Based on the results of the diagnosis of taxonomic affiliation, 3 species of trematodes of the Echinostomatidae family were identified: Hypoderaeum conoideum, Echinostoma revolutum and Echinoparyphium aconiatum. The indicators of invasion extensivity, abundance index, and also the invasion intensity of the examined birds were analyzed. The study of the fauna and prevalence of representatives of the family Echinostomatidae of the Trematoda class of the Plathelminthes type in wild birds suggests that in Pavlodar region there are quite extensive foci of echinostomiasis not only in wild waterfowl, but also in domestic birds. Wild birds provide support for foci of trematodoses. [ABSTRACT FROM AUTHOR]

Spatial distributions of animals can affect interactions with their natural enemies, such as parasites, and thus have important implications for host–parasite dynamics. While spatial variation in infection risk has been explored in many systems at the landscape scale, less attention has been paid to spatial structure at smaller scales. Here, we explore a hypothesized relationship between a common spatial variable, vertical position, and risk of parasite infection in a model aquatic system, larval frogs (Rana) and trematode (Digenea) parasites. Vertical position is relevant to this system given evidence that the densities of snail first intermediate hosts, tadpole second intermediate hosts, and trematode infective stages can vary with depth. To test the effects of depth on infection risk of larval frogs by trematodes, we performed two enclosure experiments, one in the laboratory and one in the field, in which larval frogs in cages just below the water surface or near the bottom of the water column were exposed to parasites. Compared with near-surface cages, mean infection load (number of cysts) in tadpoles in near-bottom cages was 83% higher after 48-h exposures in the laboratory and 730% higher after 10-day exposures in the field. Our findings thus indicate that infection risk depends on depth, which may have adaptive significance, as tadpoles have previously been shown to change vertical position in response to parasite presence. These results motivate future work examining vertical variation in infection risk and may have broader implications for host–parasite dynamics and evolution of host and parasite behavior. [ABSTRACT FROM AUTHOR]

To study the prevalence of gastrointestinal parasites of Panthera pardus, 26 scat samples were collected from Katepurna Sanctuary during the census period conducted by forest department during January 2018. Out of these 21 samples had the highest overall infection rate of Paragonimus sp. Echinostomatidae, Dicrocoeliidae, Pseudophyllidea, Taeniidae, Mesocestoides sp. Hymenolepididae Acanthocephala, Spiruroidea, Gnathostoma sp. Molineus sp. Ancylostomoidea, Mammomonogamus sp. Toxocara-like, Toxascaris sp., Aelurostrongylus sp., Capillaria sp. and Mixed type of infections of Ascaris sp. was found faecal samples. This study provided a first overview on parasites in Panthera pardus in the Katepurna Sanctuary. [ABSTRACT FROM AUTHOR]

Parasites can affect animal populations and communities in aquatic ecosystems. However, greater understanding is needed for the distributions and drivers of parasite infection levels in many areas. This study focuses on parasite prevalence (percent infected hosts) of an important class of parasites, trematodes, in 2 species of snail first intermediate hosts (Planorbella trivolvis and Physa sp.) in the Illinois River watershed, which has been impacted by human development. We hypothesized that trematode prevalence depends on local (e.g., water chemistry) and landscape (e.g., proximity to the Illinois River and land cover) factors. To test our hypotheses, we collected at least 20 individuals of 1 or both species of snails from 28 ponds within the watershed, and we made water-quality measurements and recorded habitat characteristics at each site. We then screened the snails for infections in the laboratory and identified the trematode cercariae that emerged based on morphological and molecular techniques. We found 5 cercariae morphotypes, including important parasites of wildlife, such as Echinostoma sp. and Ribeiroia ondatrae. Our results indicate that proximity to the Illinois River and open water or wetlands was positively associated with trematode prevalence in both snail species, whereas water chemistry (higher pH, lower calcium concentration, and lower specific conductance) was associated with increased prevalence, but only in Physa. Our findings offer increased understanding of potential environmental drivers underlying trematode distributions, with implications for wildlife health. [ABSTRACT FROM AUTHOR]

Highlights • 17 different clades of echinostomes were found in East Africa. • The majority (13/17) of clades use Biomphalaria or Bulinus as an intermediate host. • For four clades partial life cycles (2/3) were determined. Abstract Echinostomes are a diverse group of digenetic trematodes that are globally distributed. The diversity of echinostomes in Africa remains largely unknown, particularly in analyses using molecular markers. Therefore, we were interested in the composition and host usage patterns of African echinostomes, especially those that also use schistosome transmitting snails as intermediate hosts. We collected adults and larval stages of echinostomes from 19 different localities in East Africa (1 locality in Uganda and 18 in Kenya). In this study we provide locality information, host use, museum vouchers, and genetic data for two loci (28S and nad 1) from 98 samples of echinostomes from East Africa. Combining morphological features, host use information, and phylogenetic analyses we found 17 clades of echinostomes in East Africa. Four clades were found to use more than one genus of freshwater snails as their first intermediate hosts. We also determined at least partial life cycles (2 of the 3) of four clades using molecular markers. Of the 17 clades, 13 use Biomphalaria or Bulinus as a first intermediate host. The overlap in host usage creates opportunities for competition, including against human schistosomes. Thus, our study can be used as a foundation for future studies to ascertain the interactions between schistosomes and echinostomes in their respective intermediate hosts. [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.

Spermatological characteristics of the digenean Hypoderaeum conoideum (Echinostomatidae) collected from Anas platyrhynchos in the Lac d’Annecy (France) were reinvestigated using transmission electron microscopy. The previous study on this species only describes the presence of two axonemes of unequal lengths, a mitochondrion, a posterior nucleus, and the disposition of cortical microtubules. The present ultrastructural study reveals that the mature spermatozoon of H. conoideum is a filiform cell tapered at both extremities. The sperm cell exhibits the characteristics of a digenean spermatozoa type V, namely two axonemes of the 9 + '1' pattern of trepaxonematan Platyhelminthes, external ornamentation of the plasma membrane associated with cortical microtubules, and located in the anterior part of the proximal region of the sperm cell, lateral expansions, two bundles of parallel cortical microtubules, maximum number of cortical microtubules in the anterior part of the spermatozoon, and presence of two mitochondria. In addition, the sperm cell of H. conoideum shows spine-like bodies and a posterior extremity with only the nucleus. The ultrastructural characters of the spermatozoon of H. conoideum are compared with those of other digeneans belonging to the superfamily Echinostomatoidea. [ABSTRACT FROM AUTHOR]

Present study was performed to survey on infection status of Isthmiophora hortensis (formerly Echinostoma hortense) metacercariae (IhMc) in dark sleepers, Odontobutis spp., from some water systems of the Republic of Korea. A total of 237 Odontobutis spp. was collected in the water systems of 5 rivers, i.e., Mangyeong-gang (gang means river), Geum- gang, Tamjin-gang, Seomjin-gang, and Nakdong-gang. They were all examined with artificial digestion method for 5 years (2013-2017). A total of 137 (57.8%) Odontobutis spp. were infected with 14.8 IhMc in average. The prevalence was the highest in Nakdong-gang areas (62.9%) and followed by in Mangyeong-gang (57.1%), Geum-gang (56.3%), Tamjingang (54.8%), and Seomjin-gang (53.9%) areas. Metacercarial densities were 28.1 (Geum-gang), 13.9 (Mangyeong-gang), 13.3 (Nakdong-gang), 13.1 (Tamjin-gang), and 2.3 (Seomjin-gang) per infected fish. Especially, in case of Yugucheon (cheon means stream), a branch of Geum-gang, IhMc were detected in all fish (100%) examined and their density was about 48 per fish. By the present study, it was confirmed that the infection status of IhMc is more or less different by the surveyed areas and the dark sleepers, Odontobutis spp., are suitable fish hosts of I. hortensis. [ABSTRACT FROM AUTHOR]

Members of the genus Drepanocephalus are endoparasites of fish-eating birds of the families Phalacrocoracidae and Sulidae distributed across the Americas. Currently, Drepanocephalus contains three species, i.e. D. spathans (type species), D. olivaceus and D. auritus. Two additional species, D. parvicephalus and D. mexicanus were transferred to the genus Petasiger. In the current study, available DNA sequences of D. spathans , D. auritus and Drepanocephalus sp., were aligned with newly generated sequences of D. spathans and Petasiger mexicanus. Phylogenetic analyses inferred with three nuclear (LSU, SSU and ITS1, 5.8S, ITS2) and two mitochondrial (cox 1, nad 1) molecular markers showed that the sequences of D. spathans and D. auritus are nested together in a single clade with very low genetic divergence, with Petasiger mexicanus as its sister species. Additionally, P. mexicanus was not a close relative of other members of the genus Petasiger, showing that P. mexicanus actually belongs to the genus Drepanocephalus, suggesting the need to re-allocate Petasiger mexicanus back into the genus Drepanocephalus , as D. mexicanus. Morphological observations of the newly sampled individuals of D. spathans showed that the position of the testes is variable and testes might be contiguous or widely separated, which is one of the main diagnostic traits for D. auritus. Our results suggest that D. auritus might be considered a synonym of D. spathans and, as a result, the latter represents a species with a wide geographic range across the Americas, parasitizing both the Neotropical and the double-crested cormorant in Argentina, Brazil, Paraguay, Venezuela, Colombia, Mexico, USA and Canada. [ABSTRACT FROM AUTHOR]

The localisation and the composition of germinal material in miracidia and mother sporocysts of Echinostoma caproni were studied with the use of histological and electron microscopic methods. Germinal material in miracidia was localised in the posterior body half and was represented by 3-4 undifferentiated cells and 5-7 germinal cells. Taken together, these cells are referred to as the primordium of the germinal mass. In the mother sporocyst, germinal elements also form and develop in the germinal mass, which is located caudally. It comprises undifferentiated cells and germinal cells as well as embryos of various ages (up to the stage of 30-50 blastomeres). Germinal cells divide only by cleavage. New germinal cells are formed only from undifferentiated cells, which can proliferate in the germinal mass and nowhere else. This indicates that the germinal mass is the reproductive organ of E. caproni mother sporocyst. [ABSTRACT FROM AUTHOR]

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Echinostoma caproni (Trematoda: Echinostomatidae) is an intestinal trematode, broadly employed to study the host-dependent mechanisms that govern the evolution of intestinal helminth infections. Resistance against E. caproni homologous secondary infections has been reported in mice and appears to be related to the generation of a local Th2 response, whereas Th1 responses promote the development of chronic primary infections. Herein, the ability of E. caproni to modulate its secretome according to the host environment is investigated. A two-dimensional differential in gel electrophoresis (2D-DIGE) analysis was performed to elucidate changes in the excretory/secretory products of E. caproni adults after primary and secondary infections in mice. A total of 16 protein spots showed significant differences between groups, and 7 of them were successfully identified by mass spectrometry. Adult worms exposed to a primary infection appear to upregulate proteins involved in detoxification (aldo-keto reductase), stress response (GroEL), and enhancement of parasite survival (acetyl-CoA A-acetyltransferase and UTP-glucose-1-phosphate urydyltransferase). In contrast, any protein was found to be significantly upregulated after secondary infection. Upregulation of such proteins may serve to withstand the hostile Th1 environment generated in primary infections in mice. These results provide new insights into the resistance mechanisms developed by the parasites to ensure their long-term survival. [ABSTRACT FROM AUTHOR]

Abstract: Associations among parasites affect many aspects of host–parasite dynamics, but a lack of analytical tools has limited investigations of parasite correlations in observational data that are often nested across spatial and biological scales. Here we illustrate how hierarchical, multiresponse modelling can characterize parasite associations by allowing for hierarchical structuring, offering estimates of uncertainty and incorporating correlational model structures. After introducing the general approach, we apply this framework to investigate coinfections among four amphibian parasites (the trematodes Ribeiroia ondatrae and Echinostoma spp., the chytrid fungus Batrachochytrium dendrobatidis and ranaviruses) and among >2,000 individual hosts, 90 study sites and five amphibian host species. Ninety‐two percent of sites and 80% of hosts supported two or more pathogen species. Our results revealed strong correlations between parasite pairs that varied by scale (from among hosts to among sites) and classification (microparasite versus macroparasite), but were broadly consistent across taxonomically diverse host species. At the host‐scale, infection by the trematode R. ondatrae correlated positively with the microparasites, B. dendrobatidis and ranavirus, which were themselves positively associated. However, infection by a second trematode (Echinostoma spp.) correlated negatively with B. dendrobatidis and ranavirus, both at the host‐ and site‐level scales, highlighting the importance of differential relationships between micro‐ and macroparasites. Given the extensive number of coinfecting symbiont combinations inherent to natural systems, particularly across multiple host species, multiresponse modelling of cross‐sectional field data offers a valuable tool to identify a tractable number of hypothesized interactions for experimental testing while accounting for uncertainty and potential sources of co‐exposure. For amphibians specifically, the high frequency of co‐occurrence and coinfection among these pathogens—each of which is known to impair host fitness or survival—highlights the urgency of understanding parasite associations for conservation and disease management. [ABSTRACT FROM AUTHOR]

Adult specimens of Echinostoma ilocanum (Garrison, 1908) Odhner, 1911 (Trematoda: Echinostomatidae) were recovered from 2 riparian people who resided along the Mekong River in Savannakhet Province, Lao PDR. In fecal examinations done by the Kato-Katz technique, they revealed echinostome eggs together with eggs of Opisthorchis viverrini (and minute intestinal fluke eggs) and hookworms. To recover the adult flukes, they were treated with praziquantel 30-40 mg/kg in a single dose and purged with magnesium salts. A total of 658 adult fluke specimens were recovered from the 2 people; 456 from case 1 and 202 from case 2. Specimens from case 1 consisted of 335 echinostomes (301 E. ilocanum and 34 species undetermined), 120 O. viverrini, and 1 Haplorchis taichui, and those from case 2 consisted of 36 E. ilocanum, 134 O. viverrini, and 32 H. taichui. Thus, the number of E. ilocanum specimens was 337 in total (average per person, 168.5). From this study, it is suggested that foodborne intestinal flukes and liver flukes are highly prevalent along the Mekong River in Savannakhet Province. The present report describes for the first time human infections with E. ilocanum in Lao PDR. [ABSTRACT FROM AUTHOR]

The review summarizes data on the number, size and localization of serotoninergic neurons in cercariae of 16 trematode species, referring to 11 families. Presented diagrams show distribution patterns of serotoninergic neurons in cercariae of trematodes from different taxonomic, biological and morphological groups. Data analysis indicates that the number, disposition and size of these neurons vary in cercariae of different species. The data are discussed in relation with a functional significance of serotonin as a neurotransmitter in free-living larvae—trematode cercariae. [ABSTRACT FROM AUTHOR]

Echinostoma paraensei (Digenea: Echinostomatidae) lives in the duodenum and bile duct of rodents and is reported as a useful model for studies on the biology of flatworms. Here, we compared the growth and development of pre and post ovigerous worms collected 3, 7, 14 and 21 days post infection from experimentally infected hamster (permissive host) and Wistar rat (less permissive hosts). Linear measurements and ratios were examined by light (morphology and morphometry) and confocal laser scanning microscopy. At day 3, either worm from hamsters or rats were small with poorly developed gonads. At seven day, worms increased in size and morphometric differences between hosts are statistically significant after this time. In addition, adult worms (14 and 21 days of age) harvested from hamster showed developed gonads and vitelline glands laterally distributed on the body, whereas worms from rat showed atrophied reproductive system characterized by underdeveloped vitelline glands and stunted ovary. The worm rate recovery in rat decreased from 29.3% (day 7) to 20.6% (day 14) and 8% (day 21), whilst it remained around 37% in hamster. In conclusion, this is the first appointment demonstrating that low permissiveness influences the reproductive system of echinostome since the immature stages of development. The phenotypic analysis evidenced that hamster provides a more favorable microenvironment for gonads development than rat, confirming golden hamster as a permissive host, whereas Wistar rat is less permissive host. [ABSTRACT FROM AUTHOR]

A survey was performed to know the infection status of echinostome metacercariae in Cipangopaludina chinensis malleata snails from Korea. Total 75 snails collected in 5 localities, i.e., Imsil-gun, Jeollabuk-do, Hwasun-gun and Shinan-gun (Aphae and Jido), Jeollanam-do, and Jinju-si, Gyeongsangnam-do, were examined for metacercariae by the artificial digestion method. Infection rates of metacercariae were 80.0%, 66.7%, 100%, 60.0%, and 73.3%, and their densities were 39, 32, 183, 19, and 30 per snail infected, respectively. The metacercariae were round, 105-118×105-118 μm in size, with a thin cyst wall, collar spines on the head collar, and excretory granules in 2 canals of excretory tube. Adult flukes were elongated, ventrally curved, and 5,167×939 μm in average size. Head collar distinct, bearing 45 collar spines with 5 end groups on each side. Oral sucker subterminal, pharynx well developed, and esophagus somewhat short. Cirrus sac well developed, with a saccular seminal vesicle, and ventral sucker very large. Ovary elliptical and on the median line of the body. Testes tandem and slightly lobed. Eggs operculated, elliptical, and 90-103×55-60 μm in size. By scanning electron microscopy, the head collar was prominent with 45 collar spines resembling horns of younger stags. Scale-like tegumental spines were densely distributed on the body surface between the head collar and ventral sucker. Conclusively, it has been first confirmed that the life cycle of E. macrorchis is indigenously maintained in Korea, and C. chinensis malleata snails are popularly infected with the metacercariae of this echinostome. [ABSTRACT FROM AUTHOR]

Rapid losses of biodiversity due to the changing landscape have spurred increased interest in the role of species diversity and disease risk. A leading hypothesis for the importance of biodiversity in disease reduction is the dilution effect, which suggests that increasing species diversity within a system decreases the risk of disease among the organisms inhabiting it. The role of species diversity in trematode infection was investigated using field studies from sites across the U.S. to examine the impact of snail diversity in the infection dynamics of both first and second intermediate larval stages of Echinostoma spp. parasites. The prevalence of Echinostoma spp. sporocysts/rediae infection was not affected by increases in snail diversity, but significant negative correlations in metacercariae prevalence and intensity with snail diversity were observed. Additionally, varying effectiveness of the diluting hosts was found, i.e., snail species that were incompatible first intermediate hosts for Echinostoma spp. were more successful at diluting the echinostome parasites in the focal species, while H. trivolvis, a snail species that can harbor the first intermediate larval stages, amplified infection. These findings have important implications not only on the role of species diversity in reducing disease risk, but the success of the parasites in completing their life cycles and maintaining their abundance within an aquatic system. [ABSTRACT FROM AUTHOR]

Background: Helminth infections are among the most prevalent neglected tropical diseases, causing an enormous impact in global health and the socioeconomic growth of developing countries. In this context, the study of helminth biology, with emphasis on host-parasite interactions, appears as a promising approach for developing new tools to prevent and control these infections. Methods/Principal findings: The role that antibody responses have on helminth infections is still not well understood. To go in depth into this issue, work on the intestinal helminth Echinostoma caproni (Trematoda: Echinostomatidae) has been undertaken. Adult parasites were recovered from infected mice and cultured in vitro. Double indirect immunofluorescence at increasing culture times was done to show that in vivo-bound surface antibodies become trapped within a layer of excretory/secretory products that covers the parasite. Entrapped antibodies are then degraded by parasite-derived proteases, since protease inhibitors prevent for antibody loss in culture. Electron microscopy and immunogold-labelling of secreted proteins provide evidence that this mechanism is consistent with tegument dynamics and ultrastructure, hence it is feasible to occur in vivo. Secretory vesicles discharge their content to the outside and released products are deposited over the parasite surface enabling antibody trapping. Conclusion/Significance: At the site of infection, both parasite secretion and antibody binding occur simultaneously and constantly. The continuous entrapment of bound antibodies with newly secreted products may serve to minimize the deleterious effects of the antibody-mediated attack. This mechanism of immune evasion may aid to understand the limited effect that antibody responses have in helminth infections, and may contribute to the basis for vaccine development against these highly prevalent diseases. [ABSTRACT FROM AUTHOR]

Trematodes of the subclass Digenea are a major impediment to catfish aquaculture in the southeastern United States. Catfish production ponds are ideal feeding grounds for piscivorous birds, and given the variety of aquatic snails that inhabit these ponds, they offer a prime environment for the propagation of digenetic life cycles. In July 2014, snails morphologically consistent with Biomphalaria havanensis L. Pfeiffer, 1839, were collected from 2 different catfish production ponds in the catfish farming region of eastern Mississippi. These snails were refractory to Schistosoma mansoni Sambon, 1907, infection, and phylogenetic analyses based on internal transcribed spacer (ITS)1 and ITS2 fragments placed the snails within the B. havanensis/ obstructa complex. Some (1.5%) of these snails shed cercariae morphologically and molecularly consistent with Drepanocephalus auritus Kudlai, Kostadinova, Pulis, and Tkach, 2015 (formerly reported as Drepanocephalus spathans Dietz, 1909) , an echinostomatid parasite of the double-crested cormorant Phalacrocorax auritus Lesson, 1831, and channel catfish Ictalurus punctatus Rafinesque, 1818. Juvenile channel catfish were challenged individually with ∼275 cercariae of D. auritus per fish, resulting in limited mortality (2 out of 10 fish). Surviving fish were euthanatized 7 d postchallenge, and the presence of metacercariae was confirmed histologically. Parasite-associated pathology was consistent with previous studies. Subsequent molecular analysis of 5 different gene targets confirmed morphological identifications. Previous research has suggested the existence of discrete North American and South American haplotypes of D. auritus. Mitochondrial cytochrome c oxidase subunit 1 and nicotinamide adenine dinucleotide dehydrogenase subunit 1 sequences demonstrated that both haplotypes were released by snails in this study, suggesting a broader distribution of these genetic variants than previously thought. Along with Planorbella trivolvis Say, 1817, this work identifies a second snail species common to catfish aquaculture ponds that releases D. auritus infective to juvenile channel catfish and is the first report of B. havanensis as an intermediate host for D. auritus in North America. [ABSTRACT FROM AUTHOR]

Echinostoma cribbi sp.n. is being described here, collected from the small intestine of the bird cattle egret (Bubulcus ibis Linn., 1758). The new species is characterized by 38-40 collar spines absence of esophagus, having contiguous ovary and testes, anterior testis smaller as compared to posterior testis and a different host and locality. This is the ninth species of Echinostoma Rud., 1809 being reported from a bird of Pakistan. [ABSTRACT FROM AUTHOR]

The specimens collected from American mink (Neovison vison) and European polecat (Mustela putorius) in Lithuania were morphologically identified as Isthmiophora melis (Schrank, 1788) Lühe, 1909 and were molecularly characterized through sequencing of partial 18S rDNA, 28S rDNA, ITS1- 5.8S-ITS2 region, and ND1. Relations of I. melis to other species of the genus Isthmiophora Lühe 1909 were discussed. According to ITS1 and ND1 sequences the closest species to I. melis is Isthmiophora hortensis (Asada, 1926). [ABSTRACT FROM AUTHOR]

Trematode parasites can affect their molluscan hosts, which serve as the first intermediate hosts in their life cycles, in manifold ways, but little is known about trematode-induced effects on their second intermediate hosts. Experimental infection of blue mussels Mytilus edulis serving as second intermediate hosts for larval stages (metacercariae) of the trematodes Himasthla elongata was studied in field experiments during one year. The heart rates and growth rates of noninfected mussels were significantly higher than those of infected mussels. During the summer, the heart rates of noninfected mussels showed rhythmic oscillations, whereas the parasitized animals displayed no any rhythmicity. There was a significant difference between the infected and uninfected mussels in relation to heart rates and temperature. The results indicate that mussels infected with H. elongata metacercariae may be at an energetic disadvantage relative to noninfected mussels. Furthermore, trematode infection may disrupt neuronal control of cardiac function. [ABSTRACT FROM AUTHOR]

Parasites can influence host population dynamics, community composition and evolution. Prediction of these effects, however, requires an understanding of the influence of ecological context on parasite distributions and the consequences of infection for host fitness. We address these issues with an amphibian – trematode (Digenea: Echinostomatidae) host–parasite system. We initially performed a field survey of trematode infection in first (snail) and second (larval green frog, Rana clamitans) intermediate hosts over 5 years across a landscape of 23 ponds in southeastern Michigan. We then combined this study with a tadpole enclosure experiment in eight ponds. We found echinostomes in all ponds during the survey, although infection levels in both snails and amphibians differed across ponds and years. Echinostome prevalence (proportion of hosts infected) in snails also changed seasonally depending on host species, and abundance (parasites per host) in tadpoles depended on host size and prevalence in snails. The enclosure experiment demonstrated that infection varied at sites within ponds, and tadpole survival was lower in enclosures with higher echinostome abundance. The observed effects enhance our ability to predict when and where host–parasite interactions will occur and the potential fitness consequences of infection, with implications for population and community dynamics, evolution and conservation. [ABSTRACT FROM PUBLISHER]

The location of parasites within individual hosts is often treated as a static trait, yet many parasite species can occur in multiple locations or organs within their hosts. Here, we apply distributional heat maps to study the within- and between-host infection patterns for four trematodes ( Alaria marcianae, Cephalogonimus americanus, Echinostoma spp. and Ribeiroia ondatrae ) within the amphibian hosts Pseudacris regilla and two species of Taricha. We developed heatmaps from 71 individual hosts from six locations in California, which illustrate stark differences among parasites both in their primary locations within amphibian hosts as well as their degree of location specificity. While metacercariae (i.e., cysts) of two parasites ( C. americanus and A. marcianae ) were relative generalists in habitat selection and often occurred throughout the host, two others ( R. ondatrae and Echinostoma spp.) were highly localised to a specific organ or organ system. Comparing parasite distributions among these parasite taxa highlighted locations of overlap showing potential areas of interactions, such as the mandibular inner dermis region, chest and throat inner dermis and the tail reabsorption outer epidermis. Additionally, the within-host distribution of R. ondatrae differed between host species, with metacercariae aggregating in the anterior dermis areas of newts, compared with the posterior dermis area in frogs. The ability to measure fine-scale changes or alterations in parasite distributions has the potential to provide further insight about ecological questions concerning habitat preference, resource selection, host pathology and disease control.

The helminthological survey of 13 specimens of 5 ciconiiform species revealed the presence of 10 species of intestinal digeneans: Sphincterodiplostomum musculosum Dubois, 1936 in Tigrisoma lineatum and Ardea alba; Tylodelphys elongata (Lutz, 1928) in T. lineatum; Apharyngostrigea ardearum (Lutz, 1928) and Dolichorchis lacombeensis Lunaschi and Drago, 2006 in Ardea cocoi and Ardea alba; Posthodiplostomum nanum Dubois, 1937 in A. alba and T. lineatum; Ascocotyle diminuta (Stunkard and Haviland, 1924) in A. alba; Petasiger sp.1 in A. cocoi and Paryphostomum segregatum Dietz, 1909, Strigea vaginata (Brandes, 1888) and Petasiger sp. 2 in Coragyps atratus. Syrigma sibilatrix was free of digeneans. The reports of A. ardearum, T. elongata, S. musculosum and D. lacombeensis represent new host records; the other reports are new geographical records. Moreover, the specimens described as Apharyngostrigea brasiliana Szidat, 1929 by Labriola and Suriano (1998) were analyzed and transferred to A. ardearum.El estudio parasitológico de 13 ejemplares pertenecientes a 5 especies de aves Ciconiiformes reveló la presencia de 10 especies de digéneos intestinales: Sphincterodiplostomum musculosum Dubois, 1936 en Tigrisoma lineatum y Ardea alba; Tylodelphys elongata (Lutz, 1928) en T. lineatum; Apharyngostrigea ardearum (Lutz, 1928) y Dolichorchis lacombeensis Lunaschi y Drago, 2006 en Ardea cocoi y A. alba; Posthodiplostomum nanum Dubois, 1937 en A. alba y T. lineatum; Ascocotyle diminuta (Stunkard y Haviland, 1924) en A. alba; Petasiger sp.1 en A. cocoi y Paryphostomum segregatum Dietz, 1909, Strigea vaginata (Brandes, 1888) y Petasiger sp. 2 en Coragyps atratus. Syrigma sibilatrix no se encontró parasitada por digéneos. El presente estudio aporta nuevos registros de hospedadores para A. ardearum, T. elongata, S. musculosum y D. lacombeensis y nuevos registros geográficos para las restantes especies. Además, los organismos descritos como Apharyngostrigea brasiliana Szidat, 1929 por Labriola y Suriano (1998) fueron analizados y transferidos a A. ardearum.