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We performed a parasitological examination of the gastrointestinal tract of farmed ring-necked pheasants ( Phasianus colchicus karpowi ) on two farms in Ehime, Japan. Fecal examination through flotation and sedimentation methods (43, 103, and 50 samples in three consecutive years from 2020, respectively) detected coccidian oocysts (5–58%), or capillarid (40–56%) and heterakid eggs (45–72%). Following artificial sporology, most sporulated coccidian oocysts were ellipsoidal without micropyle nor residuum, but with 1–3 polar refractile granules, morphologically reminiscent of Eimeria phasiani (Apicomplexa: Eucoccidiorida: Eimeriidae) . Intensive sequencing of mitochondrial cytochrome c oxidase subunit I gene ( cox-1 ) using pan-eimerian primers and multiple oocyst samples from different pheasants indicated a single species. We characterized, for the first time, the cox-1 sequence of E. phasiani , known to be prevalent in wild and captive ring-necked pheasants worldwide. Worm recovery under a dissection microscope revealed two capillariid and one heterakid nematode species: Eucoleus perforans (Nematoda: Trichocephalida: Capillariidae) in the esophageal epithelium (prevalence, 8–73%), Capillaria phasianina (Capillariidae) in the cecal mucosa (10–87%), and Heterakis gallinarum (Nematoda: Ascaridida: Heterakidae) in the cecal lumen (69–88%). The small subunit ribosomal RNA gene (SSU rDNA) of E. perforans was perfectly identical to that in a previous isolate from farmed Japanese green pheasants ( Phasianus colchicus versicolor ) at a distant locality in Japan. The SSU rDNA of C. phasianin a was characterized, for the first time, demonstrating a sister relationship with Capillaria anatis , parasites found in the ceca of domestic ducks, geese, and various wild anatid birds.

Background Within the class Enoplea, the earliest-branching lineages in the phylum Nematoda, the relatively highly conserved ancestral mitochondrial architecture of Trichinellida is in stark contrast to the rapidly evolving architecture of Dorylaimida and Mermithida. To better understand the evolution of mitogenomic architecture in this lineage, we sequenced the mitogenome of a fish parasite Pseudocapillaria tomentosa (Trichinellida: Capillariidae) and compared it to all available enoplean mitogenomes. Results P. tomentosa exhibited highly reduced noncoding regions (the largest was 98 bp), and a unique base composition among the Enoplea. We attributed the latter to the inverted GC skew (0.08) in comparison to the ancestral skew in Trichinellidae (-0.43 to -0.37). Capillariidae, Trichuridae and Longidoridae (Dorylaimida) generally exhibited low negative or low positive skews (-0.1 to 0.1), whereas Mermithidae exhibited fully inverted low skews (0 to 0.05). This is indicative of inversions in the strand replication order or otherwise disrupted replication mechanism in the lineages with reduced/inverted skews. Among the Trichinellida, Trichinellidae and Trichuridae have almost perfectly conserved architecture, whereas Capillariidae exhibit multiple rearrangements of tRNA genes. In contrast, Mermithidae (Mermithida) and Longidoridae (Dorylaimida) exhibit almost no similarity to the ancestral architecture. Conclusions Longidoridae exhibited more rearranged mitogenomic architecture than the hypervariable Mermithidae. Similar to the Chromadorea, the evolution of mitochondrial architecture in enoplean nematodes exhibits a strong discontinuity: lineages possessing a mostly conserved architecture over tens of millions of years are interspersed with lineages exhibiting architectural hypervariability. As Longidoridae also have some of the smallest metazoan mitochondrial genomes, they contradict the prediction that compact mitogenomes should be structurally stable. Lineages exhibiting inverted skews appear to represent the intermediate phase between the Trichinellidae (ancestral) and fully derived skews in Chromadorean mitogenomes (GC skews = 0.18 to 0.64). Multiple lines of evidence (CAT-GTR analysis in our study, a majority of previous mitogenomic results, and skew disruption scenarios) support the Dorylaimia split into two sister-clades: Dorylaimida + Mermithida and Trichinellida. However, skew inversions produce strong base composition biases, which can hamper phylogenetic and other evolutionary studies, so enoplean mitogenomes have to be used with utmost care in evolutionary studies.

American mink ( Neovison vison ) is an invasive species in the sylvatic environment of Poland. Mink are exposed to different parasite infections as their preys serve as intermediate and/or paratenic hosts. The study aimed to discriminate the pattern of intestinal parasite infections in mink inhabiting Biebrza (BNP) and Narew (NNP) national parks. Gastrointestinal tract examinations revealed Coccidia, Echinostomatidae, Taenidae, and Capillariidae parasites. There was no significant difference in the parasite burden of mink, but patterns of infections varied between both localizations. Coccidia were found in 3.8% of BNP vs. 6.7% of NNP mink. Fluke prevalence was significantly higher in NNP 27.5% compared to 7.7% in BNP mink. Tapeworms were only found in 3.4% of NNP mink. Significantly more Aonchotheca eggs were found in BNP 34.6% vs. 11.4% in NNP mink. The intensity of coccidiosis and aonchothecosis was low in both parks. Fluke intensity varied between low to moderate (ranging from 1 to 16) in BNP and low to massive (ranging from 1 to 117) in NNP mink. Coinfections of various parasite species were noted in both areas. Morphological and DNA analysis revealed that flukes belonged to Isthiomorpha melis and tapeworms to Versteria mustelae . It was the first isolation of V. mustelae in mink of those localizations. In conclusion, our study showed that mink indwelling Biebrza and Narew national parks are moderately infested with parasites. Results suggest that mink play an important role as a reservoir for parasites endangering endemic mustelids, becoming also a potential risk factor in case of accidental transmissions to farm mink. That is why, more strict biosecurity measures are required to protect farm mink.

Background The family Capillariidae is a group of thread-like nematodes of 27 genera and over 300 species that infect a great variety of hosts including humans. Among these, some taxa such as the genus Aonchotheca have remained controversial regarding their systematic status for decades. The aim of the current study was to verify Aonchotheca ’s systemic status and to further determine whether it is a distinct genus from Capillaria using molecular and phylogenetic analyses. Results We sequenced the mitochondrial (mt) genome and nuclear small subunit (18S) rRNA gene of Aonchotheca putorii , a representative species of the genus, and investigated its systematic status in Trichinellida using maximum likelihood and Bayesian inference. The differences in amino acid sequences of 13 protein-coding genes were 12.69–67.35% among Aonchotheca , Capillaria , Eucoleus , and Pseudocapillaria with cox 1 (12.69%) and atp 8 (67.35%) as the most and the least conserved gene, respectively, and the difference of two mt rRNAs was 18.61–34.15%. Phylogenetic analyses of the complete mt genome and 18S rRNAs unequivocally showed that Aonchotheca was a distinct genus from Capillaria . Conclusions Large difference exists among Aonchotheca , Capillaria , Eucoleus, and Pseudocapillarias . Aonchotheca putorii is the first species in the genus Aonchotheca for which a complete mitogenome has been sequenced. These data are useful for phylogenetics, systematics and the evolution of Capillariidae. Graphical Abstract

One new and one already known species of nematodes are described based on specimens collected from synbranchiform fishes of the River Ganga, India, in 2021 and 2022. Pseudocapillaria (Discocapillaria) trilobularisn. sp. (Capillariidae) from the intestine of cuchia Monopterus cuchia (Hamilton) (Synbranchidae) is mainly characterised by the presence of the large ventral postcloacal lobe in the male, the spicule length 351 µm, eggs size 60–69 × 30–36 µm (with protruding polar plugs) and by the body length (male 10.50 mm, females 11.02–12.44 mm). It is the fourth species of this genus recorded from fishes in India. The species Heliconema alatum (Majumdar, 1965) (Physalopteridae) is resurrected. This nematode is redescribed from specimens collected from the intestine of zig-zag eel Mastacembelus armatus (Lacepède) (Mastacembelidae). The examination by SEM revealed some previously not reported morphological features in this nematode species, e.g., the presence of cephalic papillae or a lateroterminal depression and two inner flat dorsoventral teeth on each pseudolabium. Based on these findings, H. monopteri Moravec, Chaudhary & Singh, 2019 is considered a junior synonym of H. alatum.

Background Capillariid nematode eggs have been reported in archaeological material in both the New and the Old World, mainly in Europe and South America. They have been found in various types of samples, as coprolites, sediments from latrines, pits, or burial. Modern parasitological records show that around 300 species of capillariids have been described in all vertebrate taxa, including humans, making it a very diversified group. The main proposal of this work is to characterize and identify capillariid eggs found in archaeological sites from Europe and Brazil. Methods A total of 39 samples of archeological sites from Europe, deposited in the paleoparasitological collection of the University Marie & Louis Pasteur, Besançon, France was analyzed. In addition, 80 coprolites from the pre-Colombian archaeological site Gruta do Gentio II , Brazil, deposited in the Paleogenetic Laboratory at Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, were evaluated. Samples were treated according to the protocols of each laboratory and then analyzed under light microscopy. Capillariid eggs were classified according to length, width, plugs, and eggshell sizes, and statistical analysis of the morphometric dataset was performed. Using a reference dataset of specimens provided by both Institutional Collections, three approaches to species identification were applied: discriminant analysis, hierarchical clustering, and artificial intelligence/machine learning. Results A total of 10 samples from Europe and 4 from Brazil were positive for capillariid eggs, showing 13 different morphotypes. As European samples were mainly collected from latrines and pits, parasite–host information was absent, and consequently, species identification was impaired. In contrast, the availability of host information rendered the identification of capillariid species for the Brazilian coprolites. The new methodology indicates capillariid species identified on various samples, resulting in the presence of Capillaria exigua (Dujardin, 1845) in feline coprolite, Baruscapillaria resecta (Dujardin, 1845) in opossum, and Aonchotheca bovis (Schnyder, 1906) in bovid, in the Brazilian site, while in European sites, Capillaria venusta (Freitas e Mendonça, 1958), Aonchotheca myoxinitelae (Diesing, 1851), Eucoleus madjerdae (Bernard, 1964), and Baruscapillaria spiculata (Freitas, 1933) were found. Conclusions The study provides new results by applying innovative methodologies for parasite identification and gaining insights into the past host (human or animal)/parasite relationships. Graphical Abstract

Fine nematodes of the family Capillariidae parasitize various organs and tissues in fish, amphibians, reptiles, avians, and mammals. Currently classified into more than 20 genera, these nematodes are primarily distinguished based on the caudal structures of male worms. Morphological and molecular analyses were conducted on 15 mammal-parasitic species belonging to the genera Aonchotheca (A. putorii, A. suzukii n. sp., A. suis n. comb. (syn. Capillaria suis), A. riukiuensis, and A. bilobata), Pearsonema (P. neoplica n. sp., P. feliscati, P. iharai n. sp., and P. toriii n. sp.), Liniscus (L. himizu), Calodium (C. hepaticum), Echinocoleus (E. yokoyamae n. sp.), and Eucoleus (E. kaneshiroi n. sp., E. aerophilus, and Eucoleus sp.), using specimens from various wild and domestic animals in Japan and brown rats in Indonesia. As demonstrated in this study, nearly complete SSU rDNA sequencing is a powerful tool for differentiating closely related species and clarifying the phylogenetic relationships among morphologically similar capillariid worms. Additionally, most capillariid worms detected in dogs and cats are suspected to be shared with their respective wildlife reservoir mammals. Therefore, molecular characterization, combined with the microscopic observation of these parasites in wildlife mammals, provides a robust framework for accurate species identification, reliable classification, and epidemiological assessment.

Calodium hepaticum is a zoonotic nematode with a worldwide distribution. Although the host range of C. hepaticum includes a wide spectrum of mammals (including humans), this parasite is predominantly associated with the families Muridae and Cricetidae. Several Sigmodontinae species from Argentina were found to be infected by C. hepaticum, with a high prevalence in Akodon azarae. The present study focuses on C. hepaticum eggs from natural infection of three species of sigmodontine rodents from Argentina. Eggs were genetically characterized (intergenic 18S rRNA region). The objectives of this work are: (i) to propose a new analytical methodology; and (ii) to morphologically characterize C. hepaticum eggs, from three Sigmodontinae species (A. azarae, Calomys callidus and Oligoryzomys flavescens). Analyses were made by the Computer Image Analysis System based on the new standardized measurements and geometric morphometric tools. The resulting factor maps clearly illustrate global size differences in the parasite eggs from the three Sigmodontinae species analysed. The degree of similarity between egg populations was assessed through pairwise Mahalanobis distances, showing that the largest distances were detected between parasite eggs from C. callidus and O. flavescens. Herein, the phenotypical plasticity of C. hepaticum eggs is shown. Significant positive correlations were obtained between each egg parasite principal component 1 and rodent corporal characteristics: weight; liver weight; rodent length; and rodent body condition. The usefulness of the geometric morphometric analysis in studies of the relationship between C. hepaticum and its host must be highlighted. The high prevalence observed in A. azarae, associated with the wide size range of the parasite eggs evidenced by principal component analysis, suggests A. azarae to be the Sigmodontinae host species that plays the most important role as reservoir host for C. hepaticum in the New World.

Objectives Rodents play an important role to spread zoonotic diseases through society. The current study was carried out to collect informative data on the intestinal helminthic infections of wild rodents in Taleqan County, Alborz Province, the center of Iran, emphasizing their zoonotic aspects. Results Sixty-two killed rodents by local farmers belonging to five species were collected, among which 24 were identified as Mus musculus , 15 as Meriones persicus , 12 as Meriones libycus , 10 as Apodemus witherbyi , and 1 as Dryomys nitedula . Of them, 30 (48.4%) were infected with at least one helminth species. Rodents were infected with Hymenolepis diminuta (42%), Syphacia obvelata (21%), Hymenolepis nana (17.7%), Heligmosomoides polygyrus (9.6%), Trichuris muris (8%), and as well as a capillariid nematode that was isolated for the first time from D. nitedula in Iran. The findings of the present study revealed a significant intestinal helminthic infection of rodents in Taleqan County. Improving hygiene practices, and making a preventive attitude can be helpful to reduce the hazards of rodent-borne diseases in the area where humans, livestock, and synanthropic rodents are living close to each other.

Gastrointestinal helminth parasites can be transferred during conservation translocations and impact their outcome. The current study applied non-invasive coprological sampling to investigate the helminth infection rates and dynamics in translocated and resident European ground squirrels, during and after a population reinforcement. The FLOTAC method was calibrated and applied for the first time for the target species. In the studied coprological samples, helminth eggs belonging to Acanthocephala and Nematoda were found; the latter were morphologically identified as belonging to the families Capillariidae (Enoplida) and Trichostrongylidae (Strongylida) and superfamily Spiruroidea (Spirurida). The overall helminth prevalence and their diversity were higher in the donor colony compared to the resident one before the reinforcement. Pronounced seasonal dynamics in the parasite prevalence and diversity were observed, and their values were considerably lower in spring than in summer in both translocated and resident hosts. A year after the start of the translocation, the helminth prevalence and number of species detected in the reinforced colony had increased significantly. This is in accordance with epidemiological models and other empirical studies that predict a positive relationship between the population density of a host and the prevalence and species richness of parasites.