Natural variation in the binding pocket of a parasitic flatworm TRPM channel resolves the basis for praziquantel sensitivity.

The drug praziquantel (PZQ) is the key clinical therapy for treating schistosomiasis and other infections caused by parasitic flatworms. A schistosome target for PZQ was recently identified- a transient receptor potential ion channel in the melastatin subfamily (TRPMPZQ)-however, little is known about the properties of TRPMPZQ in other parasitic flatworms. Here, TRPMPZQ orthologs were scrutinized from all currently available parasitic flatworm genomes. TRPMPZQ is present in all parasitic flatworms, and the consensus PZQ binding site was well conserved. Functional profiling of trematode, cestode, and a free-living flatworm TRPMPZQ ortholog revealed differing sensitives (~300-fold) of these TRPMPZQ channels toward PZQ, which matched the varied sensitivities of these different flatworms to PZQ. Three loci of variation were defined across the parasitic flatworm TRPMPZQ pocketome with the identity of an acidic residue in the TRP domain acting as a gatekeeper residue impacting PZQ residency within the TRPMPZQ ligand binding pocket. In trematodes and cyclophyllidean cestodes, which display high sensitivity to PZQ, this TRP domain residue is an aspartic acid which is permissive for potent activation by PZQ. However, the presence of a glutamic acid residue found in other parasitic and free-living flatworm TRPMPZQ was associated with lower sensitivity to PZQ. The definition of these different binding pocket architectures explains why PZQ shows high therapeutic effectiveness against specific fluke and tapeworm infections and will help the development of better tailored therapies toward other parasitic infections of humans, livestock, and fish.

Effect of Moniezia Benedeni infection on ileal transcriptome profile characteristics of sheep.

BACKGROUND: The intestinal mucosal immune system, renowned for its precise and sensitive regulation, can provide comprehensive and effective protection for the body, among which the ileum is a critical induction site for regulating mucosal immune homeostasis. Moniezia benedeni parasitizes the small intestine of sheep and can cause serious pathological damage or even death to the host when the infection is severe. In this study, 5 sheep infected with Moniezia benedeni were selected as the infected group, and 5 uninfected sheep were selected as the control group. The ileal transcriptome profile characteristics of Moniezia benedeni infection were analyzed based on RNA-seq sequencing technology, aiming to lay a foundation for further exploring the perception mechanism of sheep intestines to Moniezia benedeni infection and formulating effective prevention and control strategies. RESULTS: The results showed that a total of 3,891 differentially expressed genes (DEGs) were detected in the ileum tissues of sheep between the infected and control groups with 2,429 up-regulated genes and 1,462 down-regulated genes. GO and KEGG pathway enrichment analysis of differential genes, as well as Clue GO analysis showed that differential genes were significantly enriched in immune and metabolic-related biological processes and signaling pathways. Particularly, in immune-related signaling pathways, the B cell receptor signaling pathway was significantly down-regulated, while in metabolic regulation related signaling pathways, Bile secretion, Fat digestion and absorption and Vitamin digestion and absorption were notably up-regulated. On this basis, the differential core genes related to immune metabolism were verified by qRT-PCR method. The results showed that OVAR, CD3E, CD8A, CD4 and CD28 were significantly up-regulated (P < 0.05), while CIITA, BLNK, BCL6 and CD79A were significantly down-regulated (P < 0.05), which were consistent with transcriptome sequencing data. CONCLUSIONS: The results demonstrated that Moniezia benedeni infection significantly affected the immune and metabolic processes in sheep ileum, particularly, it significantly inhibited the activation process of host B cells, and also led to an overactive function of bile acid metabolism. This finding provides a solid foundation for further elucidating the response mechanism of Peyer's patches in sheep ileum to Moniezia tapeworm infection.

Highly resolved genome assembly and comparative transcriptome profiling reveal genes related to developmental stages of tapeworm Ligula intestinalis.

Ligula intestinalis (Cestoda: Diphyllobothriidae) is an emerging model organism for studies on parasite population biology and host-parasite interactions. However, a well-resolved genome and catalogue of its gene content has not been previously developed. Here, we present the first genome assembly of L. intestinalis, based on Oxford Nanopore Technologies, Illumina and Omni-C sequencing methodologies. We use transcriptome profiling to compare plerocercoid larvae and adult worms and identify differentially expressed genes (DEGs) associated with these life stages. The genome assembly is 775.3 mega (M)bp in size, with scaffold N50 value of 118 Mbp and encodes 27 256 predicted protein-coding sequences. Over 60% of the genome consists of repetitive sequences. Synteny analyses showed that the 10 largest scaffolds representing 75% of the genome display high correspondence to full chromosomes of cyclophyllidean tapeworms. Mapping RNA-seq data to the new reference genome, we identified 3922 differentially expressed genes in adults compared with plerocercoids. Gene ontology analyses revealed over-represented genes involved in reproductive development of the adult stage (e.g. sperm production) and significantly enriched DEGs associated with immune evasion of plerocercoids in their fish host. This study provides the first insights into the molecular biology of L. intestinalis and provides the most highly contiguous assembly to date of a diphyllobothriid tapeworm useful for population and comparative genomic investigations of parasitic flatworms.

Co-Infection of Bertiella studeri and Mycobacterium tuberculosis in a Captive Rhesus Macaque (Macaca mulatta).

Bertiella studeri, a typical intestinal cestode of nonhuman primates, accidentally infects human beings. However, B. studeri infection in monkeys has been rarely reported in recent years. A case of B. studeri infection was identified in one captive rhesus macaque with natural infection of Mycobacterium tuberculosis. This study contributes to alerting the public of this helmintic zoonosis, though its infection rate is quite lower in recent years.

Population-level immunologic variation in wild threespine stickleback (Gasterosteusaculeatus).

Wild organisms are regularly exposed to a wide range of parasites, requiring the management of an effective immune response while avoiding immunopathology. Currently, our knowledge of immunoparasitology primarily derives from controlled laboratory studies, neglecting the genetic and environmental diversity that contribute to immune phenotypes observed in wild populations. To gain insight into the immunologic variability in natural settings, we examined differences in immune gene expression of two Alaskan stickleback (Gasterosteus aculeatus) populations with varying susceptibility to infection by the cestode Schistocephalus solidus. Between these two populations, we found distinct immune gene expression patterns at the population level in response to infection with fish from the high-infection population displaying signs of parasite-driven immune manipulation. Further, we found significant differences in baseline immune gene profiles between the populations, with uninfected low-infection population fish showing signatures of inflammation compared to uninfected high-infection population fish. These results shed light on divergent responses of wild populations to the same parasite, providing valuable insights into host-parasite interactions in natural ecosystems.

Anoplocephalid tapeworms in mountain gorillas (Gorilla beringei beringei) inhabiting the Volcanoes National Park, Rwanda.

Cestodes of the family Anoplocephalidae parasitize a wide range of usually herbivorous hosts including e.g. rodents, ungulates, primates, elephants and hyraxes. While in some hosts, the epidemiology of the infection is well studied, information is lacking in others. In this study of mountain gorillas in the Virunga Massif, an extensive sample set comprising adult cestodes collected via necropsies, proglottids shed in feces, and finally, fecal samples from both night nests and identified individuals were analysed. Anoplocephala gorillae was the dominant cestode species detected in night nest samples and individually known gorillas, of which only 1 individual hosted a Bertiella sp. It was shown that the 2 species can be distinguished through microscopy based on egg morphology and polymerase chain reaction (PCR) assays for diagnostics of both species were provided. Sequences of mitochondrial (cox 1) and nuclear (ITS1, 18S rDNA, 28S rDNA) markers were used to evaluate the phylogenetic position of the 2 cestodes detected in mountain gorillas. Both types of fecal samples, from night nests and from identified individuals, provided comparable information about the prevalence of anoplocephalid cestodes, although the analysis of samples collected from identified gorilla individuals showed significant intra-individual fluctuation of A. gorillae egg shedding within a short period. Therefore, multiple samples should be examined to obtain reliable data for wildlife health management programmes, especially when application of anthelmintic treatment is considered. However, while A. gorillae is apparently a common symbiont of mountain gorillas, it does not seem to impair the health of its host.

A dominance of Mu class glutathione transferases within the equine tapeworm Anoplocephala perfoliata.

The most common equine tapeworm, Anoplocephala perfoliata, has often been neglected amongst molecular investigations and has been faced with limited treatment options. However, the recent release of a transcriptome dataset has now provided opportunities for in-depth analysis of A. perfoliata protein expression. Here, global, and sub-proteomic approaches were utilized to provide a comprehensive characterization of the A. perfoliata soluble glutathione transferases (GST) (ApGST). Utilizing both bioinformatics and gel-based proteomics, GeLC and 2D-SDS PAGE, the A. perfoliata 'GST-ome' was observed to be dominated with Mu class GST representatives. In addition, both Sigma and Omega class GSTs were identified, albeit to a lesser extent and absent from affinity chromatography approaches. Moreover, 51 ApGSTs were localized across somatic (47 GSTs), extracellular vesicles (EVs) (Whole: 1 GST, Surface: 2 GSTs) and EV depleted excretory secretory product (ESP) (9 GSTs) proteomes. In related helminths, GSTs have shown promise as novel anthelmintic or vaccine targets for improved helminth control. Thus, provides potential targets for understanding A. perfoliata novel infection mechanisms, host­parasite relationships and anthelmintic treatments.

Distinct evolutionary lineages of Schistocephalus parasites infecting co-occurring sculpin and stickleback fishes in Alaska.

Sculpins (coastrange and slimy) and sticklebacks (ninespine and threespine) are widely distributed fishes cohabiting 2 south-central Alaskan lakes (Aleknagik and Iliamna), and all these species are parasitized by cryptic diphyllobothriidean cestodes in the genus Schistocephalus. The goal of this investigation was to test for host-specific parasitic relationships between sculpins and sticklebacks based upon morphological traits (segment counts) and sequence variation across the NADH1 gene. A total of 446 plerocercoids was examined. Large, significant differences in mean segment counts were found between cestodes in sculpin (mean = 112; standard deviation [s.d.] = 15) and stickleback (mean = 86; s.d. = 9) hosts within and between lakes. Nucleotide sequence divergence between parasites from sculpin and stickleback hosts was 20.5%, and Bayesian phylogenetic analysis recovered 2 well-supported clades of cestodes reflecting intermediate host family (i.e. sculpin, Cottidae vs stickleback, Gasterosteidae). Our findings point to the presence of a distinct lineage of cryptic Schistocephalus in sculpins from Aleknagik and Iliamna lakes that warrants further investigation to determine appropriate evolutionary and taxonomic recognition.

Infection of endemic chub Squalius tenellus with the intestinal tapeworm Caryophyllaeus brachycollis (Cestoda): histopathology and ultrastructural surveys.

The endemic chub Squalius tenellus (Heckel, 1843) was introduced more than 100 years ago to Lake Blidinje (Bosnia-Herzegovina). Only 1 species of enteric helminth was found in a sample of 35 chubs, the tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953). The paper includes histopathological investigation with identification of innate immune cells involved in host reaction and molecular data allowed correct designation of the cestode species. Of 35 specimens of chub examined, 21 (60%) harboured individuals of C. brachycollis and a total of 1619 tapeworms were counted, the intensity of infection ranged from 1 to 390 worms per fish (46.2 ± 15.3, mean ± s.e.). Histopathological and ultrastructural investigations showed strict contact between the worm's body and the epithelia and increase in the number of mucous cells, rodlet cells among the epithelial cells. Within the tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were noticed. This is the first study of the occurrence of C. brachycollis in chub from Lake Blidinje and on the response of the innate immune cells of S. tenellus to this tapeworm. Interestingly, in 3 very heavily infected chubs, perforation of the intestinal wall was documented; this is uncommon among cestodes which use fish as a definitive host.

First report of apparent praziquantel resistance in Dipylidium caninum in Europe.

Dipylidium caninum is a common tapeworm of dogs. Two cases of praziquantel resistance have been described in D. caninum in the United States. No further reports have been published to the authors' knowledge. Here, the case of a dog imported to Switzerland from Spain with a history of chronic excretion of tapeworm proglottids and unresponsiveness to praziquantel treatments is reported. Clinical signs were mild (restlessness, tenesmus, anal pruritus, squashy feces) and flea infestation could be ruled out. Infection with D. caninum was confirmed through morphological and genetic parasite identification. Different subsequently applied anthelmintic compounds and protocols, including epsiprantel, did not confer the desired effects. Proglottid shedding only stopped after oral mebendazole administration of 86.2 mg kg−1 body weight for 5 consecutive days. Clinical signs resolved and the dog remained coproscopically negative during a follow-up period of 10 months after the last treatment. This case represents the first reported apparent praziquantel and epsiprantel resistance in D. caninum in Europe. Treatment was extremely challenging especially due to the limited availability of efficacious alternative compounds.

Two proteocephalid cestodes in the fish Malapterurus electricus and Heterobranchus bidorsalis from Lake Nasser, Egypt: a morphological, molecular, and histopathological study.

Despite the importance of the electric catfish (Malapterurus electricus) and the African giant catfish (Heterobranchus bidorsalis) in the foodweb of Lake Nasser, Egypt, little is known about their diseases and parasitic fauna. This work describes, for the first time, cestodiasis in M. electricus and H. bidorsalis. Corallobothrium solidum and Proteocephalus sp. were identified morphologically and molecularly from M. electricus and H. bidorsalis, respectively. Using PCR, sequencing, and phylogenetic analysis, the two cestodes shared rRNA gene sequence similarities yet were unique and the two new sequences for the proteocephalid genera were submitted to the GenBank database. The prevalence of infection was 75% and 40% for the two fish species, respectively. Infections significantly increased in the summer and spring and were higher in female fish than in male fish. The intestine was the preferred site of the two adult cestodes. However, in the case of C. solidum some larval cestodes were found outside the intestine in between the skin and abdominal musculature, attached to the mesentery, and within intestinal tunica muscularis. Desquamation of the intestinal epithelium and inflammation at the site of infection in addition to congestion of the intestinal wall of the tapeworm infected fish were evident, indicating that C. solidum and Proteocephalus sp. impacted the infected fish. The larval stages of C. solidum attempted to penetrate the intestine and sometimes they were encircled within fibrous layers infiltrated with inflammatory cells. The infected fish's musculature was free of cestode infections. Preventive measures should be implemented to prevent the spread of infections.

Dasyrhynchus giganteus plerocercoids encysting in the musculature of Indian halibut (Psettodes erumei): seasonal prevalence, morpho-molecular characterization, and histopathological alterations.

This study investigated the prevalence, morphology, molecular identification, and histopathological effects of larval tapeworms (plerocercoids) infecting the skeletal muscles of the Indian halibut (Psettodes erumei) collected from the coastal waters of the Arabian Gulf. Numerous oval or round blastocysts, measuring 13-26 mm, were found embedded within the muscular tissues of the Indian halibut, rendering the fish unsuitable for human consumption. Morphological and molecular analyses identified the plerocercoids as Dasyrhynchus giganteus (family Dasyrhynchidae), with an overall prevalence of 15.4%. The seasonal prevalence was the highest in summer (14.6%), followed by spring (10.6%), winter (4.4%), and autumn (3.5%). Infection rates increased with fish size. Histopathological examination revealed fibrous connective tissue capsules surrounding the larvae, causing muscular atrophy and degenerative changes, with few inflammatory eosinophilic cells. Molecular and phylogenetic analysis of the 28S rDNA gene sequences confirmed the specimens as D. giganteus, clustered closely with other sequences of D. giganteus with 100% bootstrap values. This study provided valuable insights into the parasitic infection dynamics, seasonal variation, molecular identification, and histopathological effects, highlighting the importance of monitoring fish for food safety and public health implications.

First molecular characterisation of Hydatigera taeniaeformis (Cestoda: Taeniidae) from Rattus rattus in urban market centres from Tamale, Ghana.

BACKGROUND: The common cat tapeworm, Hydatigera taeniaeformis, is widely distributed across many regions of the world but its global genetic diversity, ecology, and other biological features are not fully understood. The predator-prey relationship of felids and rodents sustains the transmission in both sylvatic and synanthropic or urban settings. This study was carried out in three urban market centres in Tamale, Ghana to determine the prevalence of H. taeniaeformis infection in urban rats and characterise the local population genetics using the mitochondrial nad1 gene sequences. METHODS: From January to May 2023, rats were captured and euthanized to identity and isolate the H. taeniaeformis metacestodes. The full mitochondrial nad1 gene was amplified, sequenced and used to characterise the cestode population. RESULTS: In total 64/80 rats from the three market centres were found naturally infected with metacestodes of H. taeniaeformis. Averagely, infected rats harboured two cysts with one exceptional case of 25 cysts in one liver. Each cyst harboured one metacestode. The DNA sequences revealed four haplotypes in a star-like distribution network across the three market centres. All four haplotypes were found to be unique, clustered with H. taeniaeformis sensu stricto (s.s.) global isolates and had only marginal variation among themselves. CONCLUSION: This is the first account of the genetic variability within H. taeniaeformis in Ghana and would contribute to ongoing and future studies on African regional biogeographic distribution of the common cat tapeworm.

Non-lethal detection of Eubothrium crassum (Cestoda) in farmed Atlantic salmon, Salmo salar, using anal swabs and real-time PCR.

Detection of intestinal parasites in fish typically requires autopsy, resulting in the sacrifice of the fish. Here, we describe a non-lethal method for detecting the tapeworm Eubothrium crassum in fish using anal swabs and real-time PCR detection. Two assays were developed to detect cytochrome oxidase I (COI) mitochondrial DNA and 18S ribosomal DNA sequences of E. crassum, respectively. The assays were tested on swab samples from confirmed pathogen free Atlantic salmon (Salmo salar L.) and on samples from farmed Atlantic salmon, where the presence and intensity of parasites had been established through autopsy. The COI assay was shown to be specific to E. crassum, while the 18S assay also amplified the closely related E. salvelini, a species infecting Arctic charr (Salvelinus alpinus L.) in freshwater. The COI assay detected E. crassum in all field samples regardless of parasite load while the 18S assay failed to detect the parasite in two samples. The results thus demonstrates that this non-lethal approach can effectively detect E. crassum and can be a valuable tool in assessing the prevalence of infection in farmed salmon, aiding in treatment decisions and evaluating treatment effectiveness.

Taxonomic inflation or hidden diversity: unveiling the fact surrounds Lytocestus indicus (Cestoda: Caryophyllidea).

The tapeworms belonging to the order Caryophyllidea (Platyhelminthes, Eucestoda) represent a widespread group of intestinal parasites found in cypriniform and siluriform fishes. This group comprises four families (Balanotaeniidae, Capingentidae, Caryophyllaeidae, Lytocestidae), 42 genera and approximately 130 described species. Additionally, over a hundred new taxa have been reported from India. While many of these taxa are endemic and have unique evolutionary importance, a considerable number of putative new taxa were also invalidated because the quality and reliability of the published data did not meet the requirements. Various researchers have synonymised 28 species into a single representative, Lytocestus indicus (Moghe, 1925) Woodland, 1926. Consequently, L. indicus was chosen as a model organism to investigate whether there is taxonomic inflation or hidden diversity. Newly collected specimens of L. indicus were subjected to various fixatives for morphological assessment, and hologenophores of the same were obtained to determine whether true variations exist in their genotype or if they are merely fixation-induced variations. Despite morphological variations associated with fixation, molecular data indicated that they were indeed the same specimens. The taxonomic status of 43 new taxa was critically evaluated, with most of them tentatively synonymised with L. indicus. Others were also found to be conspecific with L. indicus but were classified as unavailable names based on their first description in unpublished dissertations.

Molecular identification and prevalence of plerocercoid larvae (Cestoda: Diphyllobothriidae) in some commercial fish species from Peru.

Diphyllobothriosis, a fish-borne zoonosis in South America, is mainly caused by the Pacific broad tapeworm Adenocephalus pacificus Nybelin, 1931, a parasite of considerable concern in fishery resources due to its impact on public health. A new diphyllobothrid, Diphyllobothrium sprakeri Hernández-Orts et al. Parasites Vectors 14:219, 2021, was recently described from sea lions from the Pacific Coast, but marine fish acting as intermediate hosts are unknown. The objective of this study was to confirm the presence of plerocercoid larvae of Diphyllobothriidae Lühe, 1910 (Cestoda: Diphyllobothriidea) in nine fish species of commercial importance in Peru. Of a total of 6999 fish (5861 Engraulis ringens, 853 Sciaena deliciosa, 6 Sciaena callaensis, 171 Scomber japonicus, 40 Trachurus murphyi, 40 Ariopsis seemanni, 18 Merluccius peruanus, 5 Sarda chiliensis, and 5 Coryphaena hippurus), 183 were infected with plerocercoid larvae, representing a total prevalence of 2.61% and a mean intensity of 3.2. Based on mtDNA cox1 sequences of 43 plerocercoids, a phylogenetic analysis revealed that 41 belong to A. pacificus and two to D. sprakeri. These findings are first molecular data for D. sprakeri larvae, and the infections of E. ringens and T. murphyi by plerocercoid larvae represent the first records of intermediate/paratenic hosts for this species. Hence, the findings of the current study enhance our understanding of the presence of diphyllobothriid species in commercial fish from the Southeastern Pacific Ocean and their potential impact on seafood safety for local human populations.

Integrative taxonomy of metazoan parasites of the bluntnose sixgill shark Hexanchus griseus (Bonnaterre, 1788) in the Mediterranean Sea, with the resurrection of Grillotia acanthoscolex Rees, 1944 (Cestoda: Trypanorhyncha).

Appropriate diagnoses of parasites of apex marine predators are crucial to understand their biodiversity, host specificity, biogeography, and life cycles. Such diagnoses are also informative of ecological and biological characteristics of both host and environment in which the hosts and their parasites live. We here (i) investigate the parasite fauna of a bluntnose sixgill shark Hexanchus griseus (Bonnaterre, 1788) obtained from the Gulf of Naples (Tyrrhenian Sea), (ii) characterize molecularly all its metazoan parasites, and (iii) resurrect and report the main morphological features and phylogenetic position of Grillotia acanthoscolex, a cestode species previously synonymized with Grillotia adenoplusia. A rich parasite fauna represented by eight different taxa was found, including two monogeneans (Protocotyle grisea and Protocotyle taschenbergi), one digenean (Otodistomum veliporum), four cestodes (Crossobothrium dohrnii, Clistobothrium sp., G. acanthoscolex, and G. adenoplusia), and one copepod (Protodactylina pamelae). Sequencing of these samples accounts for an important molecular baseline to widen the knowledge on the parasitic fauna of bluntnose sixgill sharks worldwide and to reconstruct their correct food chains. The bluntnose sixgill shark was found to be a definitive host for all endoparasites found here, confirming that it occupies an apex trophic level in the Mediterranean Sea. The taxa composition of the trophic parasite fauna confirms that the bluntnose sixgill shark mostly feeds on teleost fish species. However, the occurrence of two phillobothrid cestodes (C. dohrnii and Clistobothrium sp.) suggests that it also feeds on squids. Finally, we emphasize the importance of using integrative taxonomic approaches in the study of parasites from definitive and intermediate hosts to elucidate biology and ecology of taxa generally understudied in the Mediterranean Sea.

Extracts and Terpenoids from Stevia Species as Potential Anthelmintics for Neglected Tropical Diseases Caused by Cestode Parasites.

Cestodes are etiological agents of neglected diseases such as echinococcosis and cysticercosis, which are major public health problems. Antiparasitic treatment relies on a small number of approved drugs, which are often only partially effective, poorly tolerated and require prolonged administration. Thus, the discovery of novel potential treatments is critical. The Stevia genus (Asteraceae) includes species that are recognized as a source of bioactive compounds, with many species associated with medicinal uses. In this study, the cestocidal activity of four South American Stevia species that previously showed antiprotozoal activity was analyzed using a motility assay on the laboratory cestode model, Mesocestoides vogae. The four Stevia extracts showed cestocidal activity, with S. alpina var. alpina as the most active. The sesquiterpene lactones estafietin and eupatoriopicrin were purified from S. alpina var. alpina and S. maimarensis, respectively, and tested on M. vogae. Estafietin showed cestocidal activity, inhibiting parasite viability in a dose-dependent manner, even from the first day of incubation. Consistent with the motility effects, the extract of S. alpina var. alpina and estafietin induced marked alterations in the morphology of the parasite. The results of this report show that Stevia species represent a source of new molecules with potential for the treatment of neglected tropical diseases caused by cestodes.

Cestode diversity in shrews from islands in the Sea of Japan and the Sea of Okhotsk.

A comparative analysis of taxonomic diversity on shrew cestodes among four islands in the Sea of Japan and the Sea of Okhotsk (Sakhalin, Kunashir, Hokkaido, and Moneron) was performed. Cestode species shared among the islands were identified and their host specificity was investigated. On Sakhalin Island, 33 species of the families Hymenolepididae, Dilepididae and Mesocestoididae were recorded in four shrew species (Sorex caecutiens, S. gracillimus, S. minutissimus and S. unguiculatus). In S. caecutiens, S. gracillimus, and S. unguiculatus on Kunashir Island, 22 species of the same families were found and, on Hokkaido Island, 23 species of the families Hymenolepididae and Dilepididae were recorded. On Moneron Island, three species of cestodes were registered in S. tundrensis. The Sakhalin-Hokkaido-Kunashir complex of shrew cestodes includes eastern-Palearctic, trans-Palearctic and endemic species. High endemism (~22%) of shrew tapeworms in the Sakhalin-Kunashir-Hokkaido Islands was noted as compared to continental territories. The different numbers of cestode species in S. unguiculatus (31), S. caecutiens (29), S. gracillimus (19) and S. minutissimus (1) were found. It was concluded that the cestodes species diversity of shrews of Sakhalin-Kunashir-Hokkaido depended primarily on the history of island formation, their modern physical and geographical features, the abundance of definitive and intermediate cestodes hosts and, to a lesser extent, on the size and remoteness of the islands from the mainland and the diversity of host species.

A new species of Versteria (Cestoda: Taeniidae) parasitizing Neogale vison and Lontra canadensis (Carnivora: Mustelidae) from Western Canada.

Via molecular and morphological analyses, we describe adult specimens of a new species of Versteria (Cestoda: Taeniidae) infecting mink and river otter (Carnivora: Mustelidae) in Western Canada, as well as larval forms from muskrat and mink. These sequences closely matched those reported from adult specimens from Colorado and Oregon, as well as larval infections in humans and a captive orangutan. We describe here a new species from British Columbia and Alberta (Canada), Versteria rafei n. sp., based upon morphological diagnostic characteristics and genetic distance and phylogeny. Versteria rafei n. sp. differs from the three other described species of the genus in the smaller scolex and cirrus sac. It also differs from V. mustelae (Eurasia) and V. cuja (South America) by having an armed cirrus, which is covered in hair-like bristles, and in the shape of its hooks, with a long thorn-like blade, and short or long handle (vs. a short sharply curved blade and no difference in handle size in previously described species). The poorly known V. brachyacantha (Central Africa) also has an armed cirrus and similarly shaped hooks. However, it differs from the new species in the number and size of hooks. Phylogenetic analysis of the cox1 and nad1 mitochondrial regions showed that our specimens clustered with isolates from undescribed adults and larval infections in North America, and separate from V. cuja, confirming them to be a distinct species from the American Clade.