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Digeneans of the family Notocotylidae differ from other digeneans in their peculiar eggs. The eggs feature a pair of long filaments extending from their poles, and their contents differ significantly from what we expect to observe in the eggs of digeneans. Instead of a ciliated miracidium larva, the notocotylid egg contains a tiny few-celled mother sporocyst. This sporocyst infects a snail host following accidental ingestion of the egg. Previous transmission electron microscope studies elucidated the structure of the sporocyst and proposed a mechanism of the injection relying on the structure called the opercular cord, but the data were insufficient to describe certain details. Here, we present ultrastructural data on the egg of Paramonostomum, clarifying the nature of the injection apparatus and providing the missing details of the in-egg mother sporocyst structure. We found the opercular cord to be part of the eggshell associated with the vitelline membrane. We also elucidated the intertwining connection between the germ cells and the sporocyst's tegument and explored 'nuage' granules present in the cytoplasm of the germ cells, providing evidence for identification of these cells as the germ ones. We discuss our findings in the context of transition of miracidia to a passive strategy of snail infection., Competing Interests: Declarations. Ethical approval: Not applicable. Animal welfare: Not applicable. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

The literature about mollusc-parasite interactions is focused on species affecting human health, such as trematodes on freshwater snails as intermediate hosts. Far less attention has been paid to parasite-snail interactions in terrestrial habitats. Here we present the first observation of a sciomyzid larva of Limnia unguicornis, parasitizing a vulnerable, tiny air-breading snail, Vertigo moulinsiana (strictly protected by Polish law). Sciomyzids are almost exclusively malacophagous but their biology and ecology are understudied. Thus, we have reviewed the available information on Limnia species and discussed the results of our research., (© 2024. The Author(s).)

This study aimed to investigate the occurrence of larval trematode infections in bithyniid snails across five provinces in southern Thailand. A total of 1,413 Bithynia siamensis snails were collected between October 2021 and October 2022 using handpicking and scooping methods. Among these, 844 were identified as B. s. siamensis and 569 as B. s. goniomphalos. The snail samples were examined for parasitic infections in the laboratory using shedding and crushing methods. Among the 27 sampling sites, snails from 6 sites were infected with various trematode species (infection rate: 4.95%, 70/1,413). Evaluation of the morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of trematodes (belonging to four families). The identified species included Echinochasmus pelecani (family: Echinostomatidae), Echinostoma revolutum (family: Echinostomatidae), Haematoloechus similis (family: Haematoloechidae), Loxogenoides bicolor (family Lecithodendriidae), and Stictodora tridactyla (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively. The cercariae from the identified trematode species were studied for DNA analysis. The phylogenetic lineage reveals relationships among the species, confirming the morphological distinctions., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Schistosomiasis is a significant public health threat, and Oncomelania hupensis is the only intermediate host for schistosoma japonicum. We conducted 12-year monthly repeated surveys to explore the interactive and lag effects of environmental factors on snail density and to monitor their long-term and seasonal trends in a bottomland around the Dongting Lake region in China. Relevant environmental data were obtained from multiple sources. A Bayesian kernel machine regression model and a Bayesian temporal model combined with a distributed lag model were constructed to analyze interactive and lag effects of environmental factors on snail density. The results indicated the average annual snail density in the study site exhibited an increasing and then decreasing trend, peaking in 2013. Snail densities were the highest in October and the lowest in January in a year. Normalized Difference Vegetation Index (NDVI) and water level were the most effective predictors of snail density, with potential interactions among temperature, precipitation, and NDVI. The mean minimum temperature in January, water level, precipitation and NDVI were positively correlated with snail density at lags ranging from 1 to 4 months. These findings could serve as references for relevant authorities to monitor the changing trend of snail density and implement control measures, thereby reducing the occurrence of schistosomiasis., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Fasciolosis, caused by the liver fluke Fasciola spp., is a significant parasitic disease of livestock and humans worldwide. Fasciola transmission and life cycle are highly dependent on climatic conditions, especially temperature and humidity. This dependency has gained significance in the context of ongoing climate change. This literature review examined evidence on the effects of temperature variability on the developmental stages of Fasciola spp. and the snail intermediate hosts. We reviewed free larval stages of Fasciola spp. development, as well as snail intermediate hosts, while investigating the climate-related factors influencing each stage. We found that Fasciola spp. egg hatching and development were inhibited below 10 °C and optimal between 20 and 30 °C, miracidia hatching time decreased with higher temperatures and cercarial shedding by snail hosts accelerated around 27 °C. Further, metacercarial viability declined at higher temperatures but was prolonged by higher humidity. Snail intermediate host growth rates peaked at 25 °C, and their susceptibility to Fasciola infection depends on temperature, underscoring its importance in transmission dynamics. Overall, the Fasciola life cycle and snail host development exhibit stage-specific temperature thresholds, indicating a complex relationship between temperature fluctuations and parasite transmission potential. This research highlights the key role of temperature and humidity on Fasciola spp. and snail development, shedding light on the potential consequences of climate change on their survival, development, and disease transmission. Data limitations, primarily from the scarcity of high-resolution climate-related experiments, should drive future research to enhance predictive models and deepen our understanding of the impact of climate change on this parasitic disease., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

As ecosystem disruptors and intermediate hosts for various parasites, freshwater snails have significant socioeconomic impacts on human health, livestock production, and aquaculture. Although traditional molluscicides have been widely used to mitigate these effects, their environmental impact has encouraged research into alternative, biologically based strategies to create safer, more effective molluscicides and diminish the susceptibility of snails to parasites. This review focuses on alterations in glucose metabolism in snails under the multifaceted stressors of parasitic infections, drug exposure, and environmental changes and proposes a novel approach for snail management. Key enzymes within the glycolytic pathway, such as hexokinase and pyruvate kinase; tricarboxylic acid (TCA) cycle; and electron transport chains, such as succinate dehydrogenase and cytochrome c oxidase, are innovative targets for molluscicide development. These targets can affect both snails and parasites and provide an important direction for parasitic disease prevention research. For the first time, this review summarises the reverse TCA cycle and alternative oxidase pathway, which are unique metabolic bypasses in invertebrates that have emerged as suitable targets for the formulation of low-toxicity molluscicides. Additionally, it highlights the importance of other metabolic pathways, including lactate, alanine, glycogenolysis, and pentose phosphate pathways, in snail energy supply, antioxidant stress responses, and drug evasion mechanisms. By analysing the alterations in key metabolic enzymes and their products in stressed snails, this review deepens our understanding of glucose metabolic alterations in snails and provides valuable insights for identifying new pharmacological targets., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The intricate relationships between parasites and hosts encompass a wide range of levels, from molecular interactions to population dynamics. Parasites influence not only the physiological processes in the host organism, but also the entire ecosystem, affecting mortality of individuals, the number of offspring through parasitic castration, and matter and energy cycles. Understanding the molecular mechanisms that govern host-parasite relationships and their impact on host physiology and environment remains challenging. In this study, we analyzed how infection with Microphallus trematodes affects the metabolome of two Littorina snail species inhabiting different intertidal zone shore levels. We applied non-targeted GC-MS-based metabolomics to analyze biochemical shifts induced by trematode infection in a host organism. We have identified changes in energy, amino acid, sugar, and lipid metabolism. In particular, we observed intensified amino acid catabolism and nitrogenous catabolites (glutamine, urea) production. These changes primarily correlated with infection and interspecies differences of the hosts rather than shore level. The changes detected in the host metabolism indicate that other aspects of life may have been affected, both within the host organism and at a supra-organismal level. Therefore, we explored changes in microbiota composition, deviations in the host molluscs behavior, and acetylcholinesterase activity (ACE, an enzyme involved in neuromuscular transmission) in relation to infection. Infected snails displayed changes in their microbiome composition. Decreased ACE activity in snails was associated with reduced mobility, but whether it is associated with trematode infection remains unclear. The authors suggest a connection between the identified biochemical changes and the deformation of the shell of molluscs, changes in their behavior, and the associated microbiome. The role of parasitic systems formed by microphallid trematodes and Littorina snails in the nitrogen cycle at the ecosystem level is also assumed., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Indoplanorbis exustus, a freshwater pulmonate snail, is widely distributed in tropical and subtropical zones and plays a significant role as an intermediate host for trematode parasites. Various genetic markers have been used for species identification and phylogenetic studies of this snail. However, there are limited studies about their molecular genetics based on nuclear ribosomal DNA (rDNA) genes. A genetic analysis of I. exustus in Thailand was conducted based on the nuclear 18S rDNA (339 bp) and 28S rDNA (1036 bp) genes. Indoplanorbis snails were collected from 29 localities in 21 provinces covering six regions of Thailand. Nucleotide sequences from 44 snails together with sequences from the GenBank database were examined for phylogenetic relationships and genetic diversity. All sequences of the selected nucleotide regions exhibited a high level of similarity (99%) to the sequences of I. exustus in the GenBank database. The maximum likelihood tree based on the 18S and 28S rDNA fragment sequences of I. exustus in Thailand revealed only one group with clear separation from another genus in the family Planorbidae. The I. exustus 28S rDNA sequences showed intraspecific genetic divergence ranging from 0 to 0.78% and were classified into 8 different haplotypes. Conversely, the 18S rDNA data showed lower variation than the 28S rDNA data and revealed a single haplotype and intraspecific distances of zero among all sampled individuals. The haplotype network of 28S rDNA sequences of I. exustus in Thailand revealed six unique haplotypes and two haplotypes shared by at least two regions. Overall, both markers were successful in the identification of I. exustus. However, these markers, particularly the 18S rDNA, may not be suitable for genetic analysis within the species, particularly for population genetic studies, due to their limited variation as seen in this study. In summary, this study not only enhances understanding of genetic variation in I. exustus but is also useful for the selection of molecular markers in future genetic research., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Schistosoma japonicum had once caused the greatest disease burden in China and has still been transmitted in some hilly areas, for example, in Shitai of Anhui province, where rodents are projected to be the main reservoir. This may lead to a critical need of molecular tools with high efficiency in monitoring the dynamic of the rodent-associated S. japonicum, as an appropriate amount of schistosome input can re-establish its life cycle in a place with snails and then result in the re-emergence of schistosomiasis. Therefore, the goal of this study was to develop high polymorphic microsatellites from the whole genome of rodent-associated S. japonicum strain to monitor its transmission dynamic. We sampled the hilly schistosome isolate from Shitai of Anhui in China and sequenced the parasite with the next-generation sequencing technology. The whole genome was assembled with four different approaches. We then developed 71 microsatellite markers at a genome-wide scale throughout two best assembled genomes. Based on their chromosome mapping and the expected length of targeted sequences, we selected 24 markers for the development of multiplex reactions. Two multiplexes composed of 10 loci were finally developed, and their potential was revealed by their successful application on and capturing the genetic diversity of three schistosome populations. The selected 10 markers, each with clear chromosome location and characteristics, will be greatly useful in tracing the dispersal pathways or/and dynamics of the rodent-associated S. japonicum or others in the hilly area of China or elsewhere., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The trematode Postharmostomum commutatum is a parasite of the chicken Gallus gallus domesticus. Its heavy infection can cause inflammation and hemorrhage in the cecum of host birds. We found a severe infection of metacercariae of P. commutatum, which was identified based on DNA barcodes with morphology, in the introduced land snail Bradybaena pellucida and its related species in the Kanto region of Japan. Our field survey revealed that metacercariae were detected in 14 of 69 sampling locations in this region. B. pellucida was thought to be the major second intermediate host of metacercariae of the trematode because this snail was most frequently found in the study area and the prevalence and infection intensity were higher than those of the other snail species. The observed increase in metacercariae in introduced populations of B. pellucida can enhance the infection risk of chickens and wild host birds, probably owing to the spillback effect. Our seasonal field study showed that the prevalence and infection intensity of metacercaria seemed to be high in populations of B. pellucida during the summer and early autumn. Therefore, chickens should not be bred outdoors during these seasons to prevent severe infection. Our molecular analysis, based on cytochrome c oxidase subunit I sequences, showed a significantly negative value for Tajima's D in P. commutatum, suggesting an increase in its population size. Thus, P. commutatum distributed in the Kanto region may have increased its population size with the introduction of the host snail., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Ornamental fish are becoming increasingly popular, but the lack of knowledge regarding their various diseases is a major challenge. Skin diseases commonly found in freshwater fish include black spot disease (BSD), which is characterized by melanin deposits around the metacercariae of some trematode species. Since BSD remains poorly understood, this study describes an outbreak of BSD in Etroplus maculatus raised in outdoor ponds at a Brazilian fish farm. Metacercariae samples were collected, examined, and subjected to molecular phylogenetic analysis. The parasites were conspecific to an unnamed species, Crassiphiala lineage 5, recently found in Brazilian birds (Megaceryle torquata). Sequences obtained for longifurcate cercariae of the planorbid snail Biomphalaria straminea from the same region were identical to our metacercariae of Crassiphiala sp. These results suggest that Biompahalaria snails are likely an intermediate host of this parasite on farms where E. maculatus was found to be infected. We provide the first molecular evidence that Crassiphiala are the causative agents of BSD in fish from Brazil. Combatting snails and preventing access of fish-eating birds to outdoor ponds are strategies to control this disease in ornamental fish farms., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this study, rodents (Rattus rattus) and mollusks (Achatina fulica) were captured in a small forest located in a large metropolitan city in Brazil, and they were examined to investigate possible parasitism by Angiostrongylus cantonensis. The parasites were recovered as helminths from the pulmonary arteries of the synanthropic rodents and as third-stage larvae (with Metastrongylidae family characteristics) from the mollusks. To confirm the species, these larvae were used to experimentally infect Rattus norvegicus for the posterior recovery of adult helminths. To identify the adult helminths, morphological, morphometric, molecular, and phylogenetic techniques were employed. Furthermore, we also characterized the histological lesions associated with parasitism in naturally infected definitive hosts. Our results demonstrated the occurrence of a natural life cycle of A. cantonensis (with the presence of adult helminths) in definitive hosts, Rattus rattus, and third-stage larvae in an intermediate host, A. fulica. In free-living rodents, lesions of granulomatous pneumonia in the lungs and meningitis in the brain were also found. These results warn of the risk of accidental transmission of A. cantonensis to human residents around the park because of the extensive interaction among the fauna of the park, domestic animals, and the surrounding human population., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The presence of parasitic ciliates of the hymenostome genus Tetrahymena was examined in 150 mollusks belonging to six bivalve and 13 gastropod species in Slovakia, Central Europe. Tetrahymenids were detected only in two species, viz., in the invasive Lusitanian slug (Arion vulgaris) and in the native swollen river mussel (Unio tumidus). Although only 10.52% of the examined mollusk taxa were positive, their Tetrahymena infections were very intensive accounting for several hundreds of ciliates per host. Phylogenetic analyses of the 16S and 18S rRNA genes as well as of the barcoding region of the gene encoding for cytochrome c oxidase subunit I revealed that both isolates represent new taxa, T. foissneri sp. n. and T. unionis sp. n. The former species belongs to the 'borealis' clade and its nearest relative is T. limacis, a well-known parasite of slugs and snails. Besides molecular data, T. foissneri can be distinguished from T. limacis also morphologically by the body shape of the parasitic-phase form, dimensions of micronuclei, and the silverline system. On the other hand, T. unionis was classified within the 'paravorax' clade along with T. pennsylvaniensis, T. glochidiophila, and T. nigricans. Although these four species are genetically distinct, T. unionis could be morphologically separated only from T. nigricans by body shape and size. The present study suggests that both aquatic and terrestrial mollusks represent interesting hosts for the discovery of novel Tetrahymena lineages.

Foodborne zoonotic trematode (FZT) infections are common neglected tropical diseases in Southeast Asia. Their complicated life cycles involve freshwater snails as intermediate hosts. A cross-sectional study was conducted in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, to investigate the diversity of cercariae of potential FZT and to construct the phylogenetic relationship of trematode cercariae based on the Internal Transcribed Spacer 2 (ITS2) region. Among 17 snail species collected from various habitats, 13 were infected by 10 cercarial groups among which parapleurolophocercous, pleurolophocercous, and echinostome cercariae were of zoonotic importance. The monophyletic tree separated cercarial sequences into different groups following the description of the cercariae families in which Haplorchidae, Opisthorchiidae, Echinochasmidae, and Echinostomatidae are important families of FZT. The overall prevalence was different among snail species and habitats and showed a seasonal trend. Parapleurolophocercous and echinostome cercariae emerged as the most common cercariae in snails in Yen Bai, while monostome, echinostome, and megalura cercariae were most common in Thanh Hoa. Using a molecular approach, we identified Parafossarulus striatulus as the first intermediate snail host of Clonorchis sinensis in Thac Ba Lake. Melanoides tuberculata and Bithynia fuchsiana were we identified preferred intermediate snail hosts of a diverse range of trematode species including intestinal flukes (i.e., Haplorchis pumilio and Echinochasmus japonicus) in Yen Bai and Thanh Hoa, respectively.

In circumstances where populations of invasive species occur across variable landscapes, interactions among invaders, their parasites, and the surrounding environment may establish local coevolutionary trajectories for the participants. This can generate variable infection patterns when parasites interact with sympatric versus allopatric hosts. Identifying the potential for such patterns within an invasive-species framework is important for better predicting local infection outcomes and their subsequent impacts on the surrounding native community. To begin addressing this question, we exposed an invasive snail (Bithynia tentaculata) from two widely separated sites across the USA (Wisconsin and Montana) to the digenean parasite, Sphaeridiotrema pseudoglobulus, collected from Wisconsin. Parasite exposures generated high infection prevalences in both sympatric and allopatric snails. Furthermore, host survival, host growth, the proportion of patent snails, and the timing of patency did not differ between sympatric and allopatric combinations. Moreover, passaging parasites through snails of different origins had no effect on transmission success to subsequent hosts in the life cycle. However, the number of parasites emerging from snails and the pattern of their release varied based on snail origin. These latter observations suggest the potential for local adaptation in this system, but subsequent research is required to further substantiate this as a key factor underlying infection patterns in the association between S. pseudoglobulus and B. tentaculata.

A new snail-eating leech, Batracobdelloides bangkhenensis sp. n., was discovered at Kasetsart University, Bangkhen Campus, Bangkok, Thailand. This species is found free living in the benthic zone of ponds; feeds on freshwater snails, including Bithynia siamensis siamensis, Indoplanorbis exustus, Radix rubiginosa, Physella acuta, and Pomacea canaliculata; and uses a shell as a shelter during the parental care period, with a colony of 7-15 juvenile individuals held on the venter inside the shell of host. Batracobdelloides bangkhenensis displays distinct morphological characters, including a rice-shaped body showing transparency, cephalization, two eye pairs merged on somite III, an anterior sucker twice as large as the cephalic region, a central mouth in the anterior sucker, seven light brown transverse rows in the neck region, absent dorsal papillae, rich green pigments on the dorsum, a male gonopore on XIIa2/XIIa3 (27-28), a female gonopore on XIIIa1/XIIIa2 (29-30), and diffuse aggregations of minute, spherical salivary glands in the neck region. Comparisons of the COI and COI-ND1 genes showed a monophyletic clade for Batracobdelloides, and the phylogenetic tree of the COI gene also indicated that B. bangkhenensis is distinct from other species in the genus, with strong support values.

Avian schistosomes are of medical and veterinary importance as they are responsible for the annually occurring cercarial dermatitis outbreaks. For Austria, so far, only Trichobilharzia szidati Neuhaus 1952 was confirmed on species level as causative agent of cercarial dermatitis. Here we present the first record of Trichobilharzia franki Müller & Kimmig 1994 in Austria. The species was detected during a survey of digenean trematodes in Upper Austrian water bodies. Furthermore, we provide DNA barcodes of T. franki as well as measurements of several parasite individuals to indicate the intraspecific diversity. We also recommend the usage of an alternative primer pair, since the "standard COI primer pair" previously used for Schistosomatidae amplified an aberrant fragment in the sequence of T. franki. Overall, our study shows how limited our knowledge about occurrence and distribution of avian schistosomes in Austria is and how important it is to acquire such a knowledge to estimate ecological and epidemiological risks in the future.

The freshwater snail Bithynia siamensis goniomphalos serves as the first intermediate host of liver fluke Opisthorchis viverrini, a foodborne parasite, of which human infection has persisted in Southeast Asia for decades. The snail Filopaludina martensi martensi has been proposed as a biological control agent against B.s. goniomphalos, but knowledge on the snail ecology and population dynamics between the two species remains rudimentary. This study investigated selected abiotic and biotic factors influencing the distribution and abundance of B.s. goniomphalos and F.m. martensi. Water quality, soils, and snails were collected from 34 localities in Northeast Thailand. Soil properties and snail soft tissue elemental concentrations were analyzed. Experiments were performed to examine interspecific competition. Statistical analysis was conducted to explore the associations between water and soil properties and soft tissue elemental concentrations. The results showed that B.s. goniomphalos had the highest mean dominance in streams and red-yellow podzolic soils, while F.m. martensi snails preferred ponds and latosol soils. Negative correlation in species abundances was found between the two species. Interspecific competition was detected, with B.s. goniomphalos growth rates hampered by the presence of F.m. martensi. Despite the possibility of using F.m. martensi to control B.s. goniomphalos, B.s. goniomphalos exhibited a greater adaptability to different water and soil properties, suggesting that the species could colonize a wide range of environmental conditions. This study provides further insights into the ecology of the two snail species, underscoring the importance of considering abiotic factors when assessing the possible biological control agent to control O. viverrini transmission.

Human cercarial dermatitis is a parasitic disease that causes an allergic reaction in the skin (swimmer's itch) as a consequence of contact with cercariae of bird schistosomes present in water, mainly of the genus Trichobilharzia Skrjabin et Zakarow, 1920. The main objective of the study was to confirm the presence of the zoonotic disease agent following reports of human infections in recreational water in Slovakia. We identified two species of freshwater snails at Košice Lake, Radix auricularia (Linnaeus, 1758) and Physa acuta (Draparnaud, 1805). Trematode infections were observed only in R. auricularia. Of the 62 snails collected, 11 (17.7%) were infected with 5 different species of larval stages of trematodes. The blood fluke Trichobilharzia franki was found in 2 (3.2%) of the examined snails. The present record provides the first evidence that T. franki from the pulmonate snail R. auricularia represents a source of human cercarial dermatitis in recreational water in Slovakia. Our finding complements the easternmost records of both swimmer's itch and the confirmed occurrence of a bird schistosome in a waterbody in Europe. The present work suggests that the health risks associated with trichobilharziasis need to be further studied by detailed monitoring of the occurrence of the major causative agent of human cercarial dermatitis, T. franki.

Precise identification of avian schistosomes in the genus Trichobilharzia at the species level is difficult and requires both traditional morphological and molecular techniques. To obtain satisfactory results by traditional methods, the characteristics of the intact adults or large fragments of male and females are necessary. The present study aimed to introduce a more efficient method for collecting eggs and both fragments and intact worms for morphological identification of visceral Trichobilharzia spp. Thirty-eight domestic ducks (twenty-eight fresh and ten frozen) were studied. For fresh samples, warm saline (40-45 °C) was injected into the portal vein or liver tissue, followed by slicing of the liver to small pieces in a large Petri dish. All materials were then transferred into the laboratory sieves arranged from the largest to the smallest mesh size and while crushed with the hand, washed, and filtered using a trigger water sprayer. The collected materials were studied under a stereomicroscope for parasite eggs, fragments, and full-length worms. Out of 28 freshly killed ducks, 19 (67.9%) and of 10 frozen ducks 6 (60%) were positive for visceral Trichobilharzia spp. The full-length worms and large fragments of male worms were mostly recovered with the mesh no. 150 (diameter of 106 μm) and small fragments, especially of females, and eggs with the mesh no. 270 (diameter of 53 μm). In addition to large numbers of fragments, 15 full-length adults were obtained from fresh and 2 from frozen ducks. The number of collected full-length adults was related to the worm burden. Since morphological description of different species of the genus Trichobilharzia is primarily based on the availability of adult worms, the application of methods that provide a higher number of intact males and females will result in better characterization of the species and deposition of appropriate voucher specimens. These results show the present method as a suitable tool for the collection of quality adults of visceral Trichobilharzia spp. in ducks.

Parasite diagnostics were carried out on 11 Polish populations of Cepaea spp. In three of them, coming from the roadside ditches of a village (Rytel, northern Poland), very high (up to 60%) prevalence of Brachylaima mesostoma was observed. This study provides the first molecular evidence of the presence of B. mesostoma inside Cepaea spp. in Europe. In a few snails from a population found in a private garden in a small town (Chełmża, northern Poland), larvae of Brachylecithum sp. were present. Cercariae and/or metacercariae of B. mesostoma were observed in both species of Cepaea: C. hortensis and C. nemoralis, whereas larvae of Brachylecithum sp. were found only in C. nemoralis. Both species of parasites inhabited snail hepatopancreas whose structure was significantly damaged by larvae. There was no significant connection between parasite invasion and snail host morphotype. The research did not allow the reasons for the high prevalence of B. mesostoma in Cepaea spp. to be explained, and also did not explicitly indicate how the parasite invaded Cepaea spp. individuals making them, at the same time a second intermediate host. However, it poses important questions about the life cycle of the parasite that may threaten extensively kept small-size farms of poultry.

Accurate discrimination of the Schistosoma japonicum cercariae gender is very important for establishing monosexual infection animal models and for standardizing the real intensity of infection. In this study, a multiplex PCR technique consisting of two pairs of primers, of which one amplifies a 185-bp band specific for the W chromosome and the other amplifies a 420-bp band for the Z chromosome, was established to sex the S. japonicum cercariae. For male cercariae (ZZ), a single 420-bp band is expected, and for female cercariea (ZW), two distinct 185-bp and 420-bp bands can be observed. There was no cross-reaction with S. mansoni, S. haematobium, Clonorchis sinensis, Paragonimus westermani, and Trichinella spiralis. After sexing the cercariae escaped from a single snail, mice in group A were infected with 60 male cercariae and mice of group B were infected with 40 female cercariae. Meanwhile, mice in group C were infected with 10 male and 10 female cercariae that were sexed by multiplex PCR. At 45 days postinfection, male and female adult worms were recovered to verify the accuracy of multiplex PCR for sexing S. japonicum cercariae and to calculate the male and female survival rate and paired worm ratio. Our results showed that the multiplex PCR technique could distinguish male cercariae with 100% accuracy. However, sometimes the discrimination results of multiplex PCR mis-scored mixed sexual cercariae as female cercariae. The mean male adult worm burden in mice of group C was 10.7 ± 2.4, and the mean female adult worm burden was 7.7 ± 2.5. There was a significant difference between the male worm burden and female worm burden in group C. The P value was 0.013. The real paired worm ratio of group C was 74.2% (95%CI 56.6~91.8%). These results demonstrated a male-biased sex ratio in the mice model with equilibrated sex ratio cercariae infection, as predicted by our multiplex PCR technique. In conclusion, our multiplex PCR technique is an effective tool for sexing S. japonicum cercariae, especially for distinguishing male cercariae, which is of great value for establishing monosexual cercariae infection mice models to harvest male adult worms for anti-schistosomal drug screening.

Digenean parasites feature a series of stages with a distinct appearance, reproduction mode, and lifestyle that together constitute their well-known, complex life cycle. Species descriptions of Digenea have always been based on one of these stages-the marita, or sexually reproducing adult in the final host. However, in some cases, data on the life cycle are essential for the differential diagnosis of closely related species. Here, we present the case of Notocotylus atlanticus, where different stages of its life cycle were discovered for the first time since the species description, and across the Atlantic. We used a material from a naturally infected intertidal marine snail, Ecrobia ventrosa, and several waterfowl species and also carried out infection experiments. For morphological studies, we employed light microscopy, SEM, and CLSM; molecular data obtained include sequences of ITS1 and 28S rRNA gene. We demonstrate that N. atlanticus adult worm morphology is barely sufficient to distinguish it from several other species. Cercariae morphology and identity of the first intermediate hosts provide crucial additional information. According to our preliminary phylogenetic reconstructions, two notocotylid lineages are associated with two major gastropod lineages-the Caenogastropoda and the Heterobranchia. The traditional character to identify notocotylid genera (structure of ventral organs) fails to explain the phylogeny and thus requires reassessment. Further reliable morphological, life cycle and molecular data on other species are likely to reveal more patterns in notocotylid systematics, host specificity, and evolution.

Swimmer's itch has historically been controlled by applying copper sulfate (CuSO 4 ) to lakes as a way to eliminate snails that serve as the intermediate hosts for swimmer's itch-causing parasites. CuSO 4 is still sometimes applied specifically to areas of lakes where swimmer's itch severity is high. It is unclear whether targeted application of chemical molluscicides like CuSO 4 is effective for controlling swimmer's itch. Previous research has found that the larval stage of the parasites responsible for swimmer's itch are released from infected snails and are concentrated by onshore and alongshore winds, and thus, may not be affected by such focused applications. In this study, we evaluated the impact of targeted CuSO 4 application to a specific recreational swimming area in a lake in Michigan. We measured the effect on snail populations, as well as on the presence/abundance of swimmer's itch-causing parasites using qPCR. Ultimately, while CuSO 4 was confirmed to significantly reduce populations of snails within the treatment area, it was found to have no significant impact on swimmer's itch-causing parasites in the water, likely due to the free-swimming larval stages (cercariae) moving into the treatment area from surrounding regions.

Data on the life cycles and morphology of the developmental stages of Notocotylus magniovatus, Catatropis vietnamensis n. sp., and Pseudocatatropis dvoryadkini n. sp. were obtained. The Pseudocatatropis genus was restored based on our results. For the studied trematodes, the snails Parajuga spp., Helicorbis sujfunensis (Russia), and Melanoides tuberculata (Vietnam) serve as first intermediate hosts. It has been established that C. vietnamensis n. sp. differs from Catatropis harwoodi and Catatropis pakistanensis in the length of the ridge and metraterm and the location of the anterior papillae. In the life cycle of P. dvoryadkini n. sp., as in Pseudocatatropis joyeuxi, cercariae do not leave the first intermediate host. Both species are very similar in morphometric features, despite the fact that they share no common first intermediate hosts in their life cycles, and the areas of the European and Asian populations of flukes do not overlap. In phylogenetic trees and genetic distances based on the nucleotide sequences of the 28S gene and the ITS2 region of ribosomal DNA, Notocotylus attenuatus, Notocotylus intestinalis, and Notocotylus magniovatus are combined into one systematic group, while C. vietnamensis n. sp. and Catatropis indicus form another group. A third group includes members of different genera: P. dvoryadkini n. sp., and Notocotylus malhamensis, as well as three unclassified Notocotylus spp. The presence in the last group of flukes with three rows of papillae and a median ridge and lateral papillae indicates that these systematic criteria are not determinant in establishing membership of the parasitic worms to one or another genus of Notocotylidae.

The potential for local biodiversity to 'dilute' infection risk has been shown to be particularly important in aquatic trematodes, where non-host organisms can feed on free-living infective stages (cercariae) and reduce transmission rates to target hosts. Non-host organisms could also impact transmission during other stages of the trematode life cycle. In Philophthalmus spp., cercariae encyst as metacercariae on external surfaces, where they remain exposed to the adverse effects of non-host organisms. In laboratory experiments, we tested the potential for a range of non-host organisms to (i) prey on cercariae, (ii) induce early (i.e., faster) encystment and (iii) prey on or destroy metacercariae. Our results show that intertidal anemones, and to a lesser extent clams, can consume substantial numbers of cercariae. However, we found no strong evidence that the presence of these predators causes cercariae to encyst faster as a way to escape from predation. We also found that grazing snails can reduce numbers of encysted metacercariae, either by eating or crushing them. Our findings add to the growing evidence that trematode transmission success can be strongly affected by the local diversity of non-host organisms. They also reinforce the notion that parasites are potentially important food items for many organisms, thus playing roles other than consumers in many food webs.

This study is part of an effort to document the diversity of avian schistosomes in ducks and snails in Northern Iran, a major flyway (Black Sea/Mediterranean) for migratory birds and where cercarial dermatitis (CD) is prevalent in rice growing areas. CD is an allergic skin reaction from schistosome trematodes that emerge from aquatic snails. Most CD cases are reported from recreational swimmers or aquaculture farmers. Much of the work on the epidemiology of CD has focused in recreational waters in the Americas and Europe, with fewer studies in aquaculture, particularly in Iran. The artificial environment at aquaculture sites support dense populations of snails that are hosts to schistosomes, as well as domestic ducks. Thus, are domestic ducks reservoir hosts of species of Trichobilharzia, one of the main etiological agents of CD in Northern Iran? This study focused on a survey of domestic ducks for the presence of the nasal schistosome, T. regenti, that has been reported widely in Europe. Trichobilharzia regenti were found in domestic ducks in the Guilan Province of Iran based on morphological and molecular analyses. The presence of this species in Northern Iran indicates that the domestic duck can serve as a reservoir host for this species and that one of the local snail species is likely the intermediate host. The continued study and surveillance of this species is important because it is a neuropathic schistosome that can use a diversity of bird definitive hosts and Radix snails that are widespread across Eurasia.

Trichobilharzia spp. have been identified as a causative agent of swimmers' itch, a skin disease provoked by contact with these digenean trematodes in water. These parasites have developed a number of strategies to invade vertebrates. Since we have little understanding of the behavior of these parasites inside the human body, the monitoring of their invasion in snail host populations is highly recommended. In our research, lymnaeid snails were collected from several Polish lakes for two vegetation seasons. The prevalence of bird schistosomes in snail host populations was significantly lower than that of other digenean species. We were the first to detect the presence of the snails emitted Trichobilharzia regenti (potentially the most dangerous nasal schistosome) in Poland. In addition, by sequencing partial rDNA genes, we confirmed the presence of the snails positive with Trichobilharzia szidati in Polish water bodies, showing that swimmer's itch is more frequent during summer months and that large snails are more often infected with bird schistosomes than small ones.

In freshwater ecosystems, snails can significantly influence the competition between primary producers through grazing of periphyton. This activity can potentially be modified by trematodes, a large group of parasites which mostly use molluscs as the first intermediate host. Available studies, however, show contradictory effects of trematodes on snail periphyton grazing. Here, we used four different freshwater snail-trematode systems to test whether a general pattern can be detected for the impact of trematode infections on snail periphyton grazing. In our experimental systems, mass-specific periphyton grazing rates of infected snails were higher, lower, or similar to rates of non-infected conspecifics, suggesting that no general pattern exists. The variation across studied snail-trematode systems may result from differences on how the parasite uses the resources of the snail and thus affects their energy budget. Trematode infections can significantly alter the grazing rate of snails, where, depending on the system, the mass-specific grazing rate can double or halve. This underlines both, the high ecological relevance of trematodes and the need for comprehensive studies at the species level to allow an integration of these parasite-host interactions into aquatic food web concepts.

Although feline platynosomosis has been commonly reported in several parts of the world, the taxonomy and epidemiological chain related to cat liver flukes remain controversial. In this study, nuclear ribosomal ITS, 28S, and mitochondrial cox1 sequences obtained for Platynosomum illiciens from cat, marmoset, lizard, and snail found naturally infected in Brazil reveal no significant molecular differences between these isolates. Moreover, sequence data confirm that Brazilian P. illiciens from different hosts is conspecific with parasites obtained from cats in Vietnam, supporting wide distribution of the species. The lack of pronounced specificity of P. illiciens to definitive hosts is confirmed here for the first time using molecular approach. The results are discussed in context of the epizootology of platynosomosis.

For the first time, alterations in the oxidative metabolism of Achatina fulica experimentally infected with different parasite loads of Angiostrongylus cantonensis were determined. For this, the hemolymph activities of lactate dehydrogenase (LDH) and hexokinase and the glucose concentrations in the hemolymph, as well as the polysaccharide reserves in the digestive gland and cephalopedal mass, were assessed. Additionally, the contents of some carboxylic acids in the hemolymph of infected and uninfected snails were determined by high-performance liquid chromatography (HPLC), permitting a better understanding of the alterations related to the host's oxidative metabolism. As the main results, activation of oxidative pathways, such as the glycolytic pathway, was demonstrated in response to the increase in the activity of hexokinase. This tendency was confirmed by the decrease in the contents of glucose in the hemolymph of parasitized snails, indicating that the infection by A. cantonensis alters the host's metabolism, and that these changes are strongly influenced by the parasite load. This metabolic scenario was accompanied by activation of the anaerobic fermentative metabolism, indicated not only by an increase in the activity of (LDH), but also by a reduction of the content of pyruvic acid and accumulation of lactic acid in the hemolymph of parasitized snails. In this circumstance, maintenance of the host's redox balance occurs through activation of the fermentative pathways, and LDH plays a central role in this process. Together, the results indicate that A. cantonensis infection induces activation of the anaerobic metabolism of A. fulica, characterized not only by the accumulation of lactic acid, but also by a reduction in the pyruvic acid and oxalic acid contents in the hemolymph of the infected snails.

Thousands of lesser scaup (Aythya affinis) die during spring and fall migrations through the upper Midwest, USA, from infections with Cyathocotyle bushiensis and Sphaeridiotrema spp. (Class: Trematoda) after ingesting infected intermediate hosts, such as non-native faucet snails (Bithynia tentaculata). The lesser scaup is a species of conservation concern and is highly susceptible to these infections. We collected female lesser scaup from spring migratory stopover locations throughout Illinois and Wisconsin and assessed biochemical and morphological indicators of health in relation to intestinal helminth loads. Helminth species diversity, total trematode abundance, and the infection intensities of the trematodes C. bushiensis and Sphaeridiotrema spp. were associated with percent body fat, blood metabolites, hematological measures, and an index of foraging habitat quality. Helminth diversity was negatively associated with percent body fat, albumin concentrations, and monocytes, whereas glucose concentrations displayed a slight, positive association. Total trematode abundance was negatively associated with blood concentrations of non-esterified fatty acids and albumin. Infections of C. bushiensis were positively related to basophil levels, whereas Sphaeridiotrema spp. infection intensity was negatively associated with packed cell volume and foraging habitat quality. Thus, commonly measured health metrics may indicate intestinal parasite infections and help waterfowl managers understand overall habitat quality. Intestinal parasitic loads offer another plausible mechanism underlying the spring condition hypothesis.

Inducible defences against parasites that are only activated when needed can mitigate the cost of immune or behavioural evasion of parasites. Priming of the immune system and activation of behavioural defences can follow exposure to cues associated with imminent infection risk. In contrast, prior infection can cause immune depression or leave the host with less energy to defend itself against further infections. We investigate the priming of anti-parasite defences and the effect of prior infections in the amphipod Paracalliope fluviatilis, the second intermediate host of the trematode Coitocaecum parvum. During experimental infections, amphipods that had been primed by exposure to chemical cues (from first intermediate snail hosts infected by C. parvum) of infection risk were not better at avoiding further infection than control amphipods. All amphipods showed the same swimming behaviour, whether or not they had been primed by chemical cues from infected snails, or whether or not they were in the presence of live infective stages. In contrast, regardless of whether or not they had been exposed to control water or chemical cues from infected snails, amphipods harbouring prior infections acquired in nature were significantly more likely to acquire new parasites under controlled conditions. These results suggest that the induction of defences via external cues associated with the threat of infection do not play a role in the amphipod's anti-parasite strategy. However, prior infections may pre-dispose a host to acquire further parasites, with consequences for the distribution of parasites among host individuals and the regulation of the host population.

The anthropozoonotic metastrongyloid nematodes Angiostrongylus cantonensis and Angiostrongylus costaricensis, as well as Angiostrongylus vasorum, Crenosoma vulpis, Aelurostrongylus abstrusus and Troglostrongylus brevior are currently considered as emerging gastropod-borne parasites and have gained growing scientific attention in the last years. However, the knowledge on invertebrate immune responses and on how metastrongyloid larvae are attacked by gastropod immune cells is still limited. This work aims to describe an in vitro system to investigate haemocyte-derived innate immune responses of terrestrial gastropods induced by vital axenic metastrongyloid larvae. We also provide protocols on slug/snail management and breeding under standardized climate conditions (circadian cycle, temperature and humidity) for the generation of parasite-free F0 stages which are essential for immune-related investigations. Adult slug species (Arion lusitanicus, Limax maximus) and giant snails (Achatina fulica) were maintained in fully automated climate chambers until mating and production of fertilized eggs. Newly hatched F0 juvenile specimens were kept under parasite-free conditions before experimental use. An improved protocol for gastropod haemolymph collection and haemocyte isolation was established. Giemsa-stained haemolymph preparations showed adequate haemocyte isolation in all three gastropod species. Additionally, a protocol for the production of axenic first and third stage larvae (L1, L3) was established. Haemocyte functionality was tested in haemocyte-nematode-co-cultures. Scanning electron microscopy (SEM) and light microscopy analyses revealed that gastropod-derived haemocytes formed clusters as well as DNA-rich extracellular aggregates catching larvae and decreasing their motility. These data confirm the usefulness of the presented methods to study haemocyte-mediated gastropod immune responses to better understand the complex biology of gastropod-borne diseases.

In contrast to the well-studied trematode fauna of lymnaeid snails, only little is known about the role of small planorbid snails as first intermediate hosts for trematodes in temperate freshwater systems. This study aims at closing this gap by assessing the diversity and composition of larval trematode communities in Gyraulus albus and Segmentina nitida in a Central European reservoir system, and by providing an updated comprehensive review of the published trematode records of these snail hosts. A total of 3691 planorbid snails (3270 G. albus; 421 S. nitida) was collected in three consecutive years from four reservoirs of the River Ruhr catchment area in Germany. Gyraulus albus showed a higher overall trematode prevalence (11.7%) and more diverse trematode fauna (12 species) compared to S. nitida, which harboured three species and showed a lower trematode prevalence (1.7%). Altogether, 13 trematode species belonging to four families were identified in both hosts. Seven trematode species encountered in this study represent novel records for these hosts, and/or constitute first records of these larval stages from Germany. Trematode component communities in G. albus were stable across seasons and years, indicating excellent conditions for trematodes in this snail host and the continuous presence of the final hosts of the most dominant trematode species. Overall, this study reveals the importance of small planorbid snails, in particular G. albus, as first intermediate hosts for a species-rich trematode fauna in European freshwater systems, and highlights the parasites' contribution to the ecosystem's biodiversity.

Angiostrongylus cantonensis (A. cantonensis), a parasitic nematode, is the important neurotropic pathogen which causes human angiostrongyliasis. It has a complex life-cycle and severe parasite-host interaction in contrast to free-living nematode. Establishment of a well-suited life-cycle and in vitro cultivation of A. cantonensis in the laboratory will be one of the key techniques to elucidate the mechanism of parasite-host interaction. However, the low survival and growth rate of worms is still to be the problem. We optimized the known life-cycle of A. cantonensis in the laboratory, showing that small in size, easy to breed, and high compatibility of Biomphalaria straminea precede the common snails as an intermediate host of A. cantonensis. Furthermore, the egg hatching rate in Ham's F-12 medium reached approximately 80% using the eggs of mature female adult worms. We also demonstrated that the survival of larvae could be sustained for more than 30 days by in vitro cultivation of L1 larvae in DMEM with mixed antibiotics (100 units/mL of penicillin G potassium, 50 μg/mL of streptomycin sulfate, and 0.5 μg/mL of amphotericin B) and L3, L4, and L5 larvae in Waymouth's medium with 20% fetal calf serum and mixed antibiotics. Infective L1 and L3 larvae kept high infective rate to the snail and rat after cultivation in these media, respectively. It will provide the basis for studying on genetic manipulations for functional genes, new drug screening, and the mechanism of parasite-host interaction of parasitic nematodes.

Zygocercous (aggregating) cercarial larvae were recently discovered emerging from a physid snail during a molecular survey of cercariae from molluscs in lakes in central Alberta, Canada. This manuscript delves into the characterization of these cercariae through morphological and molecular techniques and provides the first genetic information for a zygocercous larval trematode. Analyses of cytochrome c oxidase I of mitochondrial DNA and two partial regions of nuclear ribosomal DNA sequences revealed the zygocercous cercariae to belong to the genus Australapatemon Sudarikov, 1959. Further analyses of sequences of Australapatemon burti (Miller, 1923), from cercariae and adults collected from across North America, indicate a complex of nine genetically-distinct lineages within this species, a surprising level of diversity. The zygocercous cercariae, along with adult worms collected from ducks in Manitoba, Canada, and from Mexico, represent one of these lineages, and are herein described as Australapatemon mclaughlini n. sp. Seven lineages cannot yet be identified, but one is tentatively identified as Australapatemon burti.

Schistosomiasis is a chronic, parasitic disease caused by flukes (trematodes) of the genus Schistosoma, which presents the most important global burden of the 17 neglected tropical diseases listed by the World Health Organization. China has made great achievements in schistosomiasis control, and now China is planning to move forward, to eliminate schistosomiasis within 2020, but the fact cannot be denied that the possibility of schistosome infection is still there in some endemic due to its zoonotic nature as well as wide distribution of its intermediate hosts (snails). Thus, how to interrupt the transmission in areas with distribution of schistosomes and intermediate snails becomes a very serious challenge that China is facing. In this paper, it is reported an advanced schistosomiasis japonica case of a 15-year-old boy which is extremely rare in the current schistosomiasis control in China. Thus, it is supposed to strengthen health education of school children and to train professional physicians of local hospitals.

Larvae of the eye fluke, Diplostomum, emerge from snails and infect fish by penetrating skin or gills, then move to the lens where they may impair the vision of the fish. For the fluke to reproduce, a bird must eat the infected fish, and it has been suggested that they therefore actively manipulate the fish's behaviour to increase the risk of predation. We found that round gobies Neogobius melanostomus, a species that was recently introduced to the Kalmar Sound of the Baltic Sea, had an eye fluke prevalence of 90-100%. We investigated how the infection related to behavioural variation in round gobies. Our results showed that the more intense the parasite-induced cataract, the weaker the host's response was to simulated avian attack. The eye flukes did not impair other potentially important anti-predator behaviours, such as shelter use, boldness and the preference for shade. Our results are in accordance with the suggestion that parasites induce changes in host behaviour that will facilitate transfer to their final host.

Digenetic trematodes of the genus Clinostomum are widely distributed in many species of freshwater fish and are known to cause the zoonotic disease Halzoun. Humans may become accidental hosts if they ingest raw freshwater fish containing metacercaria of Clinostomum complanatum, which causes pharyngitis or laryngitis. The yellow grub parasitizing cultivated ayu (Plecoglossus altivelis) and loach (Misgurnus anguillicaudatus) was one of the most serious problems in fish farms from 1977 to 1979 in Taiwan. The present study revealed, for the first time, frequent occurrence of C. complanatum metacercaria in various fish species in a natural environment, the Dahan River, in Taiwan. We examined 1503 fish specimens belonging to four families and 162 snails representing six species. C. complanatum metacercaria was mainly from the fish family Cyprinidae, and only cercaria from the snail Radix swinhoei was recovered. The prevalence and mean intensity of metacercaria were 9.8% and 9.35 parasites/infected fish, respectively. The prevalence of cercaria was low, 0.62%, in snails. Acrossocheilus paradoxus, Zacco barbata, Zacco pachycephalus, Zacco platypus, Onychostoma barbatula, and Hemibarbus labeo are new host records. Metacercariae were primarily found in the operculum, mandible, muscle, and oral cavity of fish. Morphological description and molecular analysis with 18S rDNA sequencing allowed for rapidly identifying C. complanatum. Encysted and excysted metacercariae cultivated at 22 °C in physiological saline died within 60 h. The mean intensity of infection increased with an increasing length of Z. pachycephalus. We found no association between monthly parasite prevalence and mean intensity at each sampling location. No C. complanatum metacercaria survived after 8 h of salting. The Dahan River has suitable conditions and hosts (snails, fish, and fish-eating birds) for maintaining the life cycle of C. complanatum.

Nanos is a necessary factor in the differentiation and migration of primordial germ cells. It is closely associated with the development of genitalia in a wide range of species. We questioned whether Nanos was involved in the reproductive organ development of Schistosoma japonicum. Firstly, by in situ hybridization, S. japonicum Nanos1 (SjNanos1) gene was expressed mainly in reproductive organs of S. japonicum. Then, the paired schistosome of 28 days post-infection (dpi) was transfected with SjNanos1 small interfering RNA three times and cultured in vitro for 10 days. SjNanos1 expression suppression in the mRNA and protein levels were confirmed compared to that of the controls. The morphological changes in reproductive organs and egg production were observed after SjNanos1 gene knockdown. The results observed by confocal laser scanning microscopy showed significant changes in the morphology of reproductive organs of parasites, especially the female ovaries, vitellarium, and the male testes, after RNAi. In addition, SjNanos1 silencing also induced the reduction of eggs, and affected the changes of reproduction-related genes, like Pumilio, CNOT6L, and Fs800. Therefore, our findings demonstrate that the SjNanos1 gene is essential in the development of reproductive organs and the egg production of S. japonicum.

Schistosomiasis is caused by the genus Schistosoma and affected more than 250 million people worldwide. Schistosoma japonicum was once seriously endemic in China and nearly 60 years of efforts has seen great success in disease control. However, due to its zoonotic nature and complex life cycle, the schistosomiasis transmission control and final elimination would require, besides an intersectoral approach, deep understanding of population genetics of the parasite. We therefore performed a snail survey in two marshland villages of Anhui province of China and collected S. japonicum cercariae from infected snails. By using the recent developed microsatellite panel comprising seven loci, we genotyped the sampled parasites and analyzed the population genetic diversity and structure. The results showed much lower infection prevalence of S. japonicum in snails and low infected snail density in either marshland village. Through population genetic analyses, a considerable genetic diversity of parasites was revealed, whereas a small number of clusters were inferred and the sign of bottleneck effect was detected in each village. For the first time in S. japonicum in two villages, we provided estimates of effective population sizes with two different approaches. The results indicated that the parasite in two villages could eventually be eradicated with the ongoing integral control measures, but with potential risk of reinvasion of immigrant parasites through the Yangtze River. Such would be of great importance in assessment of the effects of ongoing control measures and prediction of the transmission capability for S. japonicum, thus guiding decisions on the choice of further control work.

Schistosomiasis is a neglected tropical parasitic disease of great public health significance worldwide. Currently, mass drug administration with praziquantel remains the major strategy for global schistosomiasis control programs. Since 2005, an integrated strategy with emphasis on infectious source control was implemented for the control of schistosomiasis japonica, a major public health concern in China, and pilot studies have demonstrated that such a strategy is effective to reduce the prevalence of Schistosoma japonicum infection in both humans and bovines. However, there is little knowledge on the long-term effectiveness of this integrated strategy for controlling schistosomiasis japonica. The aim of this study was to evaluate the long-term effectiveness of the integrated strategy for schistosomiasis control following the 10-year implementation, based on the data from the national schistosomiasis control program released by the Ministry of Health, People's Republic of China. In 2014, there were 5 counties in which the transmission of schistosomiasis japonica had not been interrupted, which reduced by 95.2% as compared to that in 2005 (105 counties). The number of schistosomiasis patients and acute cases reduced by 85.5 and 99.7% in 2014 (115,614 cases and 2 cases) as compared to that in 2005 (798,762 cases and 564 cases), and the number of bovines and S. japonicum-infected bovines reduced by 47.9 and 98% in 2014 (919,579 bovines and 666 infected bovines) as compared to that in 2005 (1,764,472 bovines and 33,736 infected bovines), respectively. During the 10-year implementation of the integrated strategy, however, there was a minor fluctuation in the area of Oncomelania hupensis snail habitats, and there was only a 5.6% reduction in the area of snail habitats in 2014 relative to in 2005. The results of the current study demonstrate that the 10-year implementation of the integrated strategy with emphasis on infectious source has greatly reduced schistosomiasis-related morbidity in humans and bovines. It is concluded that the new integrated strategy has remarkable long-term effectiveness on the transmission of schistosomiasis japonica in China, which facilitates the shift of the national schistosomiasis control program from transmission control to transmission interruption and elimination. However, such a strategy seems to have little effect on the shrinking of areas of snail habitats.

Notocotylids are common digeneans parasitising birds and mammals. They have a two-host life cycle with cercariae encysting in the open. Particular life cycles remain unknown for majority of notocotylid species, including a common parasite of sea ducks Tristriata anatis. Here we resolve the life cycle of T. anatis by means of D2 LSU, ITS1 and CO1 DNA sequence analysis, showing that the first intermediate hosts for this species are periwinkles Littorina spp. Morphological descriptions of rediae and cercariae are provided for the first time, and we also supplement the existing morphological data on adults. Apart from differential diagnosis, we discuss some features of cercariae and rediae biology, geographical distribution and host range. Our molecular data confirm that genus Tristriata is monotypic and that T. anatis has circumpolar distribution. CO1 sequence analysis has shown that isolation exists between the Atlantic and Pacific populations of T. anatis, suggesting that there are geographical races. We suppose that their formation may be linked to the Last Ice Age events, when trans-Arctic bird migrations ceased and periwinkle ranges shrunk. These made transfer of parasites across the Arctic impossible, and it still has not resumed. We discuss the possible influence of host vagility and adults' lifespan on digeneans' potential for geographical colonisation.

Oncomelania hupensis snails along the Yangtze River and the low positive rate and infectiosity of human and livestock schistosomiasis still pose a threat to public health in China. Adult blood flukes were recognized as Schistosoma japonicum, which are found in the portal system of the sentinel mice bred in the laboratory for 35 days after contact with the water. However, 35 days was too long from the field test to dissection, and the dissection in the laboratory was also time-consuming and labor-intensive. Serum peptides in mice at different times after infection were measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. ClinProTool was used to establish the proteomic detection pattern (PDP), based on the differentially expressed peptide between the infection and healthy control groups. Under experimental conditions, characteristic PDP were detected in 5 % (3/60), 35 % (21/60), 75 % (45/60), 87.93 % (51/58), and 98.15 % (53/54) of infected mice from weeks 1 to 5 post-infection, whereas ELISA and dissection examination for adult blood flukes missed the first 2 weeks. At 35 days post-infection, the infectiosity assay showed 40 % (4/10), 50 % (5/10), and 80 % (8/10) positivity with the PDP test in mice infected with 4, 6, and 10 cercariae, respectively, as well as 100 % (10/10) positivity in mice infected with 14, 18, and 22 cercariae. Five stored sera of positive sentinel mice with parasite detection were verified correctly in the PDP test. The results confirm that PDP can be used as a rapid and early detection method for S. japonicum infection in experimental mice, which are expected to apply in early surveillance for schistosomiasis.

Schistosomiasis is a snail-borne disease caused by worms of the genus Schistosoma. Worldwide, human schistosomiasis remains a serious public health problem, threatening ∼800 million people in 78 countries with a loss of 70 million disability-adjusted life years. Schistosoma japonicum is the only human blood fluke that occurs in China. As one of the countries suffering greatly from schistosomiasis, over the past 65 years, China has made great strides in controlling schistosomiasis, blocking the transmission of S. japonicum in five provinces, remarkably reducing transmission intensities in the other seven endemic provinces, and China is currently preparing to move toward the elimination of this disease before 2025. However, while on the road to schistosomiasis elimination, emerging challenges merit attention, including severe advanced cases, increased movements of population and livestock, large-area distribution of intermediate host snails, limitations of new drug developments and no vaccine available, as well as imported schistosomiasis and its potential risk.

Neorickettsia are endosymbiotic bacteria that infect digeneans (Trematoda). These bacteria are of interest worldwide because of their ability to move from the parasite to its host, where they can cause serious diseases of humans and animals. While several disease-forming species of Neorickettsia have been well studied, and numerous Neorickettsia types have been identified in regions such as North America and parts of Asia, records from other locations are sparse. To date, there have been no reports of Neorickettsia from New Zealand. We screened ten species of digeneans infecting seven native gastropod species (both marine and freshwater) found near Dunedin, New Zealand, for the presence of neorickettsial infections. A >1300 bp long section of 16S rRNA belonging to a Neorickettsia bacterium was isolated from opecoelid digeneans of two individuals of the mudflat topshell snail Diloma subrostrata. These sequences represent the first evidence of neorickettsial infection in native New Zealand animals and are also the first Neorickettsia found in digeneans of the family Opecoelidae.

Digenean trematode distributions, compatibility profiles with their snail hosts, and complete life cycles remain mysteries in many parts of the world. Surveys of digenean biology and ecology provide further insight and perspective into just how incredibly diverse and important helminth parasites are in shaping local ecosystems. Past surveys have provided substantial characterizations of adult digeneans within their definitive hosts, and many now have contributed toward furthering our understanding of larval digeneans within their intermediate host communities. However, much information about the diversity of digeneans and their relationships with their snail intermediate hosts are lacking in many locations across the globe. This is certainly true in Canada, where few records related to digenean-snail relationships exist. Currently, there is a need for more information about the presence and distribution of digeneans across Canada, and how this compares to other parts of North America and beyond. To address this diversity gap in Western Canada, six lakes within central Alberta were surveyed for the presence of snails and larval digenean species and their associations. This investigation into the diversity of digeneans utilized a combined approach of morphological and molecular tools to identify 39 digenean species among five snail host species, from biweekly collections, taken over the course of 2 years (2013-2014). Here, digenean-snail combinations, presence, and distribution across sampling sites and lakes are reported. Overall, this survey contributes new information toward digenean-snail compatibility, life cycles, and distribution in Northern lake ecosystems within North America.

Preliminary findings of a high prevalence of Clonorchis sinensis in wild-caught fish in a North Vietnam reservoir (Thac Ba reservoir, Yen Bai Province) prompted a longitudinal epidemiological study of fish infections. Monthly collections of fish from September 2014 to August 2015 were processed for recovery of metacercariae; 1219 fish, representing 22 species, were examined. Seven species were infected with C. sinensis metacercariae. Four species, Toxabramis houdemeri, Hemiculter leucisculus, Cultrichthys erythropterus, and Culter recurvirostris, had high prevalence (31.1 to 76.7 %); metacercarial intensities ranged from 3.9 to 65.7 metacercariae/fish. A seasonal variation of C. sinensis prevalence was observed in T. houdemeri. Variation in intensity of infection occurred in C. erythropterus and H. leucisculus. Intensity and prevalence of C. sinensis in the most highly infected species, T. houdemeri, varied by fish size; prevalence was higher in fish weighing more than 3 g, and intensity was higher in fish weighing more than 5 g. The distribution of metacercariae in the body region of T. houdemeri was significantly higher in the caudal fin (14.7 metacercariae/g), compared to the body and head regions (0.7 and 1.4 metacercariae/g, respectively). Further epidemiological investigations on C. sinensis in this reservoir region should include assessing the relative risk of the different fish species for humans based on the latter's food preferences, and the prevalence of C. sinensis in the community. The snail intermediate host(s) in the reservoir should also be identified along with the ecological factors influencing its exposure to C. sinensis eggs and its subsequent transmission of cercariae to fish. Also needed are investigations on the relative importance of wild and domestic reservoir hosts as sources of egg contamination of the reservoir.