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Schistosomiasis is a parasitic disease affecting more than 250 million people worldwide. Schistosomes infect humans by cercariae penetrating the skin in a freshwater environment. Findings obtained more than 100 years prior showed that miracidium develops into cercaria in freshwater snails, though detailed development dynamics have not been elucidated. Although results of histological analyses of development of schistosomes in snails were presented in our previous studies, findings obtained with dynamic imaging have yet to be reported. In the present study, imaging of schistosome infection and dynamics in snails occuring within a short period was performed using fluorescent labeling agents. Labeling of S. mansoni cercariae with carboxyfluorescein succinimidyl ester (CFSE) caused no toxicity, and allowed for monitoring of schistosome dynamics in snails for up to 10 days and release of infective cercariae without fluorescence in 40 days following infection., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The lifecycle of schistosomes must be continuously maintained to clarify and understand this parasite in various aspects in laboratory settings. In the previous studies by other researchers, preservation of schistosome larvae or eggs was attempted by freezing with liquid nitrogen or organic chemicals, but frozen schistosomes were substantially impaired. The present study was conducted to determine whether schistosome eggs can be preserved under a non-frozen condition. The results showed that Schistosoma mansoni eggs could be maintained in phosphate-buffered saline at 4 °C, with a high level of infectivity of miracidia to freshwater snails thereafter. Furthermore, the egg hatchability was maintained for up to 12 weeks with weekly exchanges of the medium. The cercariae derived from snails infected with miracidia from preserved eggs were highly infective to mice. This simple schistosome egg preservation method allow researchers to maintain the schistosome lifecycle without freezing or other special procedures., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A rich fauna of digenetic trematodes has been documented from the Great Barrier Reef (GBR), yet little is known of the complex life-cycles of these parasites which occur in this diverse marine ecosystem. At Heron Island, a small coral cay at the southern end of the GBR, the intertidal marine gastropod Clypeomorus batillariaeformis Habe & Kusage (Cerithiidae) is especially abundant. This gastropod serves as an intermediate host for 12 trematode species utilising both fish and avian definitive hosts. However, 11 of these species have been characterised solely with morphological data. Between 2015 and 2018 we collected 4870C. batillariaeformis from Heron Island to recollect these species with the goal of using molecular data to resolve their phylogenetic placement. We found eight of the 12 previously known species and two new forms, bringing the total number of digenean species known to parasitise C. batillariaeformis to 14. The families of this trematode community now include the Atractotrematidae Yamaguti, 1939, Bivesiculidae Yamaguti, 1934, Cyathocotylidae Mühling, 1898, Hemiuridae Looss, 1899, Heterophyidae Leiper, 1909, Himasthlidae Odhner, 1910, Microphallidae Ward, 1901, and Renicolidae Dollfus, 1939. Molecular data (ITS and 28S rDNA) were generated for all trematode species, and the phylogenetic position of each species was determined. The digenean community parasitising C. batillariaeformis includes several common species, as well as multiple species which are uncommon to rare. Although most of those trematodes in the community which exploit fishes as definitive hosts have remained common, the composition of those which utilise birds appears to have shifted over time., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Maritae of family Notocotylidae have no ventral sucker, an organ that serves for attachment in many other digeneans. Instead, attachment is accomplished through the ventral concavity which is formed by the whole body. Musculature providing such an attachment was previously described only in part, and specific patterns of body-wall and internal muscle arrangement in notocotylids have never been studied before. In this paper we describe muscle system organization in maritae of three notocotylid species by means of fluorescent actin staining and confocal microscopy. A very special U-shaped pattern of body-wall longitudinal muscle fibres is found to support the ventral concavity. Together with very prominent dorsoventral musculature this pattern must play a key role in actions of ventral concavity. Other details concerning the muscle system are provided, including the musculature of ventral protrusions, oral sucker, walls of digestive tract and reproductive organs. We discuss functionality of the musculature and also make comparisons with cercariae of this family., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In the Japanese Archipelago, Ezohelix gainesi, a member of bradybaenid land snails, is endemic mainly to the island of Hokkaido. During July to August of 2016, a survey to detect trematode infections from E. gainesi was carried out at a forest city park in Asahikawa, Hokkaido. Systemic infections of the snails with sporocysts containing short-tailed cercariae were found in 5.3% of 94 individuals examined. Furthermore, most of them (90.4%) harbored non-encysted metacercariae within their kidneys. A DNA sequence identification revealed that both of the sporocyst and the metacercaria belong to an unknown species of the family Brachylaimidae. The metacercariae showed a genetic diversity with 6 haplotypes of mitochondrial DNA (mtDNA) even in the limited sampling area. A definitive host of the unknown species could not be determined, although 34 field mice (Apodemus speciosus) and 21 voles (Myodes rufocanus) from the city park were examined for intestinal parasites. To examine the adult stage, the metacercariae were perorally administrated to mice, together with anti-inflammatory treatment with methylprednisolone. Fully matured adult worms were recovered from the intestinal ileum 8 and 14days postinfection. The gravid adults showed typical features of the genus Brachylaima. A morphological and biogeographical evaluation prompted us to propose Brachylaima ezohelicis sp. nov. for the parasite from E. gainesi. The autochthony of the first intermediate host and the spatial heterogeneity of mtDNA suggest that the new species found in the city park is not a recently expanded population of immigrant origin., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Cercariae of digenean family Notocotylidae are characterized by a set of morphological traits which make them easily distinguishable from any other. One of the key features is absence of ventral sucker. This affects basic ways of locomotion and attachment. To understand how these functions are fulfilled we studied musculature arrangement in cercariae of two species by means of fluorescent-phalloidin staining and confocal microscopy. We used Cercaria Notocotylidae sp. No. 11 and 12 Deblock, 1980 from mud snails Ecrobia (=Hydrobia) ventrosa. Information on gross morphology (especially body-tail junction) and basic behavioural patterns of these cercariae is also updated. Major special features of musculature are associated with the ventral concavity: extreme development of dorsoventral muscle fibres and formation of annular arrangement of longitudinal muscle fibres on the ventral side. Additional body-wall and internal muscle bundles in the anterior region are also specific for notocotylid cercariae and seem to play important role in twisting movements during substratum testing. Musculature of dorsal adhesive pockets, oral sucker and tail is also described. These results are discussed in relation to observed locomotory patterns., (Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.)

The morphology of sporocysts and cercariae of Neoplagioporus elongatus (Goto and Ozaki, 1930) is described for the first time. A cotylomicrocercous cercaria obtained from the sorbeoconch snail Semisulcospira nakasekoae was confirmed to be the cercaria of N. elongatus, based on the degree of sequence identity of the COI gene to that of adult worms. Freshwater annelids (oligochaetes and leeches) and some aquatic insects (odonates) were demonstrated experimentally to be potential second intermediate hosts., (Copyright © 2017. Published by Elsevier B.V.)

Fish blood flukes (Aporocotylidae) are important pathogens of farmed finfish around the world. Among them, Cardicola spp. infecting farmed tuna are considered to be serious threats to tuna farming and have received tremendous attention. We conducted periodical samplings at a tuna farming site in Japan between January and May, 2015 to determine the life cycle of Cardicola spp. We collected over 4700 terebellid polychaetes from ropes, floats and frames of tuna culture cages and found nearly 400 infected worms. Sporocysts and cercariae found in Nicolea gracilibranchis were genetically identified as Cardicola orientalis by 28S and ITS2 ribosomal DNA sequences. This was the first discovery of the intermediate host for this parasite species. Infection prevalence and the abundance of N. gracilibranchis significantly varied between sampling points and the highest number of infected terebellids were collected from ropes. We also demonstrated morphologically and molecularly that asexual stages found in a single Amphitrite sp. (Terebellidae) and adult worms isolated from farmed juvenile tuna were Cardicola forsteri. This is the first report of C. forsteri in Pacific bluefin tuna (PBT) Thunnus orientalis in Japan. Our results demonstrated that all three species of Cardicola orientalis, C. forsteri and Cardicola opisthorchis exist in Japanese farmed PBTs and that they all use terebellid polychaetes as the intermediate hosts., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Notocotylus attenuatus (Digenea: Notocotylidae) is a monostome fluke parasitizing the intestinal caeca of waterfowl that uses an injection apparatus to infect its intermediate snail host. Morphology of the invading larva (a sporocyst), and the intramolluscan larval development of this fluke have not been characterized extensively. In this study, experimental infections of Lymnaea stagnalis using N. attenuatus eggs resulted in the development of sporocysts containing one germ ball or mother redia between 12 and 21 days post exposure (p.e.) within the hepatopancreas. Independent mother rediae and developing daughter rediae were present between day 25 and day 42 p.e. Cercariae, within the body of rediae, were detected 42 days p.e. The development of daughter rediae and cercariae started posteriorly in the body of parent redia and these larvae migrated anteriorly during development towards the birth pore. A cercaria was also observed emerging from the birth pore and released cercariae maturated further within the snail hepatopancreas prior to leaving the snail. The intramolluscan development was completed 45 days p.e. when the first fully formed cercariae were shed into the outer environment. These data detail the fascinating post-embryonic development of N. attenuatus and highlight the intricate nature of larval transitions within its snail host., (© 2013.)

Malformations and increased mortality due to infection by the digenetic trematode, Riberioa ondatrae have been reported for many species of amphibians. Severe malformations have also been reported in the Common Hourglass Tree Frog, Polypedates cruciger induced by pleurolophocercous cercariae in Sri Lanka in addition to the changes in the behaviour, development and survival of the host. We exposed pre-limb bud stage tadpoles (Gosner stages 25-26) of the Asian Common Toad, Duttaphrynus melanostictus to the same pleurolophocercous type cercariae under laboratory conditions. Molecular and morphological identification showed that these cercariae belonged Acanthostomum burminis infecting freshwater snakes as definitive hosts. These cercariae induced malformations (27.8%) and reduced survival to metamorphosis (53.8%). The magnitude of the effects increased with the dose of cercariae. Types of malformations were mainly axial, such as scoliosis and kyphosis. Severe limb malformations such as extra or missing limbs as reported for amphibians exposed to R. ondatrae were not observed in the D. melanostictus. Same authors reported a higher percentage of malformations previously when P. cruciger was exposed to the cercariae A. burminis compared to D. melanostictus. However, tadpoles of D. melanostictus, which are smaller compared to those of P. cruciger, experienced higher mortality than P. cruciger tadpoles. Trematode induced malformations and mortality in amphibians are highly variable and depend on multiple factors such as host species differences such as resistance to infection and tolerance, life-history characteristics such as size at metamorphosis and length of the metamorphosis period, and other factors such as size of the amphibian at the time of trematode exposure., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Schistosomiasis mekongi is prevalent in the Khong district of Lao PDR, made up of one big island, Khong, and numerous small islands in the Mekong River. Schistosoma mekongi is spread by Neotricula aperta as the intermediate host along the Mekong River. Therefore, even if an epidemic of S. mekongi were stamped out in a certain village, infection may recur if the source of infection is a village located in the upper reaches of the Mekong River. The purpose of this study was to construct a mathematical model for the transmission of S. mekongi among villages from the upper to lower Mekong River to estimate the effect of control measures against it. The chief characteristic of the present model is competence in dealing with the spread of infection among villages through the Mekong River in consideration of the reduction in longevity of cercariae and miracidia and their diffusion in the river. The model also takes into account seasonal fluctuation in the water level of the Mekong River, which affects human behavior in terms of water contact. The results of simulations indicated that the prevalence of schistosomiasis mekongi would be suppressed to a low level for a long time in a village further downstream when universal mass treatment is performed in villages further upstream simultaneously., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)