The genus Bursaphelenchus has attracted significant attention due to its economically devastating and quarantined species – notably the pine wood nematode B. xylophilus and B. cocophilus. Despite their ecological and agricultural importance, genomic data for this genus remain scarce. In this study, we sequenced and assembled the complete mitochondrial genomes of three Bursaphelenchus species (B. chengi, B. parantoniae, and B. sinensis) using high-throughput sequencing. The circular mitogenomes exhibited size variation, with B. chengi (17,670 bp), B. parantoniae (15,021 bp), and B. sinensis (18,386 bp) each containing the typical nematode mitochondrial gene complement: 12 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, and 22 transfer RNA (tRNA) genes. Phylogenetic analysis based on the concatenated amino acid sequences of the 12 PCGs revealed that these species form a sister clade to B. xylophilus and B. mucronatus. Comparative mitogenomic analysis demonstrated a conserved gene arrangement shared among Bursaphelenchus, Aphelenchoides, Caenorhabditis, Cruznema tripartitum, and Pristionchus pacificus, suggesting strong evolutionary conservatism across the families Aphelenchoididae, Neodiplogasteridae, and Rhabditidae. Our study enriched the mitochondrial genomic resources for Bursaphelenchus and advanced resolution of their intrageneric phylogenetic relationships.

Two Xiphinema species, one new and one known, were found from Bushehr province, southern Iran, and are herein described based on morphological and molecular data. These include Xiphinema pedrami sp. nov. and X. basiri, both belonging to the ‘Xiphinema non-americanum group’. The new dagger nematode is characterised by a body length of 3.54–5.00 mm, a lip region separated from the rest of body by a depression, odontostyle 128–148 μm long, 60–89 μm long odontophore, guiding ring at 107–138 μm from anterior end, female tail rounded to dorsally more convex with small bulge and four juvenile stages. Males have one pair of cloacal and three to five ventromedian single supplements. The new species belongs to morphospecies Xiphinema non-americanum group 5, characterised by having two equally developed female genital branches with uterine differentiation in the form of pseudo-Z-organ along with the rhomboid-shaped crystalloid bodies, and a short, rounded tail ending in a peg. The polytomous identification codes of the new species are A4, B2, C5a5b, D6, E56, F4(5), G23, H2, I34, J5a5b, K3, L2. Morphologically, the new species comes close to several known species (namely, X. andalusiense, X. artemisiae, X. baetica, X. hyrcaniense, X. ingens, X. macroacanthum and X. pseudocoxi) belonging to morphospecies group 5. The morphological differences of the new species and the aforementioned species are discussed. The second recovered species, Xiphinema basiri, belongs to the same group and has a pseudo-Z-organ in the shape of globular bodies close to pars dilatata uterus and short, conical, distinctly digitate tail. Integrative diagnosis was completed using molecular data obtained from partial sequences of the D2-D3 region of 28S rDNA, ITS1 rDNA, 18S rDNA, and COI mtDNA genes.

The taxonomic status of Sphincteristomum Oshmarin, Mamaev & Parukhin, 1961 (sensu lato) and Lobatotrema Manter, 1963 is controversial due to overlap/confusion in distinctive diagnostic characteristics for each genus and morphological/allometric ambiguity among some of their representatives and/or within records of the same species. To address these in-depth, morphological descriptions, molecular characterizations, and species delimitation analyses were conducted using a combination of comparative morphology, molecular phylogeny, multivariate analyses, and host-parasite data. Following a comprehensive review, a refined restricted concept of Sphincteristomum and Lobatotrema is proposed. Representatives of Lobatotrema comprise Lobatotrema aniferum Manter, 1963 (sensu lato) and the morphologically/phylogenetically distinct Lobatotrema droneni n. sp. Representatives of Sphincteristomum (sensu stricto) include Sphincteristomum acollum Oshmarin, Mamaev & Parukhin, 1961, and Sphincteristomum nikolaevi Parukhin, 1970. The taxonomic status of Sphincteristomum mediterraneae Abid-Kachour, Mouffok & Boutiba, 2013 is problematic based on its intermediate taxonomic position between the Megaperinae Manter, 1934 and the Schistorchiinae Yamaguti, 1942. Molecular datasets are employed in an attempt to delineate and interpret more phylogenetic relationships among schistorchiines in light of differences in oral sucker nature, oral sucker shape, and oral sphincter shape. Distributions of schistorchiines in the Indo-West Pacific are discussed. Testes arrangement as a characteristic in this group and glandular components within a muscular oral sucker are presented. We comment on the close phylogenetic relationship between members of the Schistorchiinae and the Megaperinae.

Strongyloidiasis, caused by Strongyloides stercoralis, is a neglected parasitic disease and a major global public health issue. This infection exhibits diverse clinical manifestations that, along with the high rates of asymptomatic cases and low-sensitivity diagnostic methods, contribute to the underreporting of the disease. With an estimated 600 million people infected worldwide, this disease is particularly prevalent in tropical and subtropical regions with poor sanitary conditions, which includes Brazil. Understanding the epidemiology of the disease is essential for the development of control strategies, but the lack of comprehensive data makes it difficult to identify the real impact of the infection, thus leading to underreporting and a lack of awareness of its severity on public health. Given this scenario, this literature review aimed to summarize the reported prevalence and associated factors of strongyloidiasis in Brazil. A total of 33 articles published between 2005 and 2025 were retrieved from PubMed, Science Direct, Scielo, and LiLacs databases using keywords related to strongyloidiasis in Brazil. The data collected in this review indicate that the majority of the published studies are concentrated in the Southeast region of Brazil, with the state of Minas Gerais accounting for the highest number of publications. It was also observed that the prevalence of strongyloidiasis is underestimated due to diagnostic challenges and high rates of false negatives, especially among asymptomatic patients. In addition, the scarcity of specific studies on the disease in Brazil limits the understanding of its true incidence, underscoring the need for further research.

Zoonotic diseases caused by parasites of wildlife origin represent a global health problem. As a top mammalian predator, the brown bear (Ursus arctos) can spread various parasites, including those that are potentially hazardous to human health. However, data on brown bear parasite fauna in Europe, and especially its seasonal dynamics, are scarce. The aim of this study was to analyse brown bear gastrointestinal parasites (helminths and protozoa) and to investigate their seasonal dynamics. Brown bear scats were collected from the eastern part of Estonia during one year, from spring 2022 to spring 2023. At first, we performed genetic host identification and selected 148 scat samples for further analyses. Parasite eggs and oocysts were identified based on morphology. The results revealed that the endoparasite prevalence among brown bears of Estonia is one of the highest in Europe (FO = 75%). The most prevalent were nematodes (60%), followed by protozoa (16%), cestodes (7%), trematodes (4%), and a single finding of an acanthocephalan. Of all endoparasites, the bear nematode Baylisascaris transfuga had the highest prevalence (51%). Importantly, the prevalence of nematodes and protozoa was season-dependent: highest for nematodes in autumn and lowest in spring, whereas protozoa followed the opposite dynamics. The vast majority of identified parasite taxa were zoonotic and are thus potentially hazardous to humans. This highlights the importance of monitoring wildlife parasites as an essential part of the One Health approach.

Ulcerative colitis (UC), a chronic recurrent inflammation of the colonic mucosa, has become a global emergency. With the restricted response and significant side effects of traditional drugs, a search for alternatives is mandatory. The current study aimed to evaluate the therapeutic effects of hydatid cyst fluid (HCF) and laminated layer (HLL) derived crude extract of E. granulosus, combined with the standard medication sulfasalazine (SLZ), for treating acetic acid-induced colitis. Mice were divided into 7 groups. A colitis model using acetic acid (150 μl of 5% con.) intrarectally was induced. On the 8th day following colitis induction, the mice were sacrificed. We assessed the severity of colitis using survival rate, disease activity index, colon weight/length ratio, colon weight/bodyweight ratio, and gross and histopathological score of colon damage. Immunohistochemistry for Foxp3 T-reg expression in colonic tissues was done. The levels of inflammatory cytokines tumor necrosis factor-α and IL-10, oxidative stress marker malondialdehyde, and total antioxidant capacity in serum samples were assessed. Groups treated with a combination of SLZ+HCF and SLZ+HLL revealed a statistically significant improvement compared to the colitis group by improving disease activity index, colon weight/length ratio and colon weight/bodyweight ratio, and gross and histopathological colon damage scores. Additionally, there was a significant rise in IL-4, TAC, and Foxp3+ Treg cell expression and decreased TNF-α and MDA expression. E. granulosus-derived HCF and HLL potentiate the protective effect of SLZ by increasing anti-inflammatory and antioxidant properties against murine colitis, suggesting the potential for novel therapeutic approaches.

Invasive agriolimacid slug Krynickillus melanocephalus was found infected by several species of malacopathogenic nematodes of the genus Pellioditis. Now, this Caucasian slug is actively spreading across Europe. Pellioditis is a genus of nematodes capable of killing molluscs, and its two species have been developed into widely used biological control agents. As malacopathogenic nematodes can pose a threat to survival of native, susceptible gastropod species, the distribution of K. melanocephalus and examination of associated parasites are needed. All Pellioditis species found in association with K. melanocephalus were of Caucasian origin. The new Pellioditis species was found to belong to a different clade within the genus than the other five Caucasian species and is the first representative of the clade Papillosa in the Caucasus.

The family Brachycladiidae (Digenea) is a species-rich taxon restricted to marine mammals, well-known for its associated pathogenic load, but otherwise poorly understood. A major gap in our knowledge is their circulation pathways, as the life cycle has been elucidated only for a single brachycladiid species, Orthosplanchnus arcticus, a parasite of pinnipeds. Our goal was to determine whether small ocellate metacercariae previously reported from the Barents Sea edible cockles (Cerastoderma edule) belong to the brachycladiids. We searched for brachycladiid metacercariae in nine bivalve species across three sub-Arctic Seas. They were found in three cardiid species (Ciliatocardium ciliatum, C. edule, and Serripes groenlandicus) and a scallop, Chlamys islandica. Surprisingly, we discovered numerous brachycladiid metacercariae in a single infected whelk, Buccinum undatum. Obtained molecular genetic data (mitochondrial and nuclear ribosomal) indicated that all these metacercariae belong to O. arcticus. We used statistical analysis to explore potential preferences for the second intermediate hosts in this brachycladiid species. The results suggest that bivalve size, rather than species, more accurately predicts infection patterns with O. arcticus metacercariae. We also found no significant differences in morphology between metacercariae from different bivalve species. As such, O. arcticus exhibits broad specificity for the second intermediate hosts, with larger bivalve individuals showing higher infection rates. We discuss the factors underlying this broad specificity, the benefits of larger bivalve preference, and the unequal contribution of different hosts in the transmission of a parasite. Finally, we highlight the potential zoonotic risk associated with O. arcticus due to human consumption of its intermediate hosts.

Schistosoma mansoni is a parasitic helminth that is vectored through freshwater snails. While the anti-schistosome defense of the South American snail, Biomphalaria glabrata, is well studied, little is known about the immune response of the African snail, Biomphalaria sudanica. We measured expression of five candidate immune genes in B. sudanica 8, 24, and 72 hours post-exposure to S. mansoni using reverse transcription quantitative PCR. Expression patterns of incompatible snails were compared to compatible snails and those sham exposed. We also assessed how diet (lettuce vs. pellet) affected expression of three genes, given prior findings that pellet-fed snails were more susceptible to S. mansoni. Results indicated that incompatible snails constitutively expressed higher levels of superoxide dismutase 1 (SOD1) than compatible snails at multiple time points, and of toll-like receptor (TLR) and granulin (GRN) at a single time point. Parasite-induced expression occurred at 8 hours in SOD1, biomphalysin 2, thioester protein 1 (TEP1), and granulin (GRN); however, for biomphalysin 2 and TEP1, induced expression was only detected for susceptible snails. At 24 hours, biomphalysin 2 expression increased in exposed resistant snails, and at 72 hours, all exposed snails decreased biomphalysin 2 expression compared to controls. Parasite-induced expression of SOD1, biomphalysin 2, TEP1, and GRN supports the hypothesis that these genes play a role in B. sudanica anti-schistosome defense; however, increased expression does not necessarily yield clearance of S. mansoni. SOD1 expression was higher in lettuce-fed snails at 8 and 24 hours, consistent with their greater resistance. Together, these results demonstrate the conserved and unique aspects of the B. sudanica anti-schistosome response.

This study investigates the endohelminth parasites of three-spined stickleback, Gasterosteus aculeatus, across marine, anadromous, and freshwater populations in the White Sea (Russia). A total of 241 sticklebacks were collected in Velikaya Salma Strait during 2022–2024. Thirteen helminth species were identified using morphological and molecular methods. Genetic analysis confirmed the presence of Anisakis simplex sensu stricto, Hysterothylacium aduncum, Phyllodistomum folium, Brachyphallus crenatus, and Alloopistholecithum cf. salmonis. We identified variability in parasite communities between 2022+2023 and 2024 both within and between marine, anadromous and freshwater host populations. The most striking temporal changes were observed in the parasite communities of the anadromous stickleback population, which is probably due to the different periods of time spent by the fish in fresh water in the years studied. This study highlights differences in infection of marine, anadromous, and freshwater populations of three-spined stickleback, providing insights into host-parasite dynamics across different aquatic environments in the White Sea basin.

The yellowfin, Thunnus albacares (Bonaterre), is one of the most important resources for commercial fisheries along the Mexican Pacific coast. The parasite fauna of this important marine resource has been documented in different regions across its global distributional range. However, few studies have been conducted on parasites of tuna populations in the Cortezian Marine Ecoregion (CME) in northwestern Mexico, despite the development of the fresh and frozen sushi/sashimi-grade tuna market in recent decades. Our study aimed at identifying the metazoan parasite fauna of T. albacares in the CME. Between 2023 and 2024, 17 individuals were studied for parasites before being processed. Parasites were collected and identified using morphological and molecular data. One hundred twenty-five metazoan parasites were collected, representing 10 species, including the monogeneans Hexostoma thynni (Delaroche, 1811) Rafinesque, 1815, Neobenedenia girellae (Hargis, 1955) Yamaguti, 1963, and Capsala sp., the digenean Hirudinella ahi (Pallas, 1774) Baird, 1853, the larval cestode Heterosphyriocephalus tergestinus (Pintner, 1913) Dallarés, Carrassón and Schaeffner, 2016, larval forms of the nematode Anisakis typica (Diesing, 1860) Baylis, 1920, the acanthocephalan Rhadinorhynchus laterospinosus Amin, Heckmann, and Ha, 2011, and three species of copepods, Euryphorus brachypterus (Gerstaecker, 1853), Pseudocycnus appendiculatus Heller, 1865 and Brachiella thynni Cuvier, 1830. Anisakis typica reached the highest prevalence of infection in our samples, and along with R. laterospinosus, it reached the highest mean intensity values. This study reports a species that represents a zoonotic risk (A. typica) and contributes to the understanding of the parasite diversity of commercially important fish in the CME.

Based on morphological and molecular studies, including analysis of variation of four molecular markers, there are two orientocreadiid species, Orientocreadium cf. pseudobagri and O. cf. elegans, in the south of the Russian Far East. Trematodes of these two species possess morphological and molecular variation that is most possibly related to population formation processes for these species in the investigated territory. Our molecular data show that the trematode assemblages studied were subdivided for 28S rDNA markers into two large groups related to basins in different water bodies. Nucleotide sequences of these groups are closely related to each other. Within each group there are specific nucleotide substitutions that are unique for several geographical local samples of trematodes. This variation reflects local processes of divergence of these worms. Results of the median-joining network analysis based on concatenated mitochondrial cox1 and nd1 gene sequences support this inference, showing the existence of four groups of haplotypes of Orientocreadium trematodes that are associated with geographical locations.

Environmental DNA (eDNA) metabarcoding has lagged in parasite biodiversity assessments. We implemented this method to examine parasite diversity in sediment and water from 4 physically connected aquatic habitats in coastal South Carolina, USA, as part of a ParasiteBlitz in April 2023. Sediment was collected using a syringe corer, and water was sampled using active filtration and passive collection. Five amplicon libraries, using primers targeting portions of the mitochondrial COI of platyhelminths and 18S ribosomal RNA genes of nematodes, myxozoans, microsporidians, and protists, successfully yielded parasite sequences. Out of >5.8 million sequences, we identified >1,000 parasite amplicon sequence variants (ASVs) corresponding to ~600 parasite operational taxonomic units, from 6 parasite groups. Most diversity was observed among the microsporidians, whose assay demonstrated the highest fidelity. Actively-filtered water samples captured ASVs of all 6 groups, whereas sediment captured only 4, despite yielding 3× as many ASVs. Low DNA yields from passive water samples resulted in fewer, but some unique, ASVs representing 3 parasite groups. The most efficient sampling method varied with respect to parasite group across habitats, and the parasite communities from each habitat were distinct regardless of sampling method. We detected ASVs of 9 named species, 4 of which may represent introductions to the US. The abundance of our results demonstrates the effectiveness and efficiency of eDNA metabarcoding for assessing parasite diversity during short, intensive surveys, and highlights the critical need for more comprehensive sequence databases and the development of primers for those parasite taxa that elude detection using eDNA methods.

Garra gotyla is a benthopelagic freshwater cyprinid fish native to Asia, valued for both food and ornamental purposes; nevertheless, its parasitic diseases are poorly understood. The present study investigated the presence and ecological indices (prevalence and intensity) of monogenean parasites infecting G. gotyla in Mizoram, northeast India. Additionally, the study aimed to assess the phylogenetic relationships among three closely related dactylogyrid genera: Dactylogyrus, Dogielius, and Dactylogyroides. Monogeneans were initially identified based on the comparative morphology of their sclerotised haptoral and reproductive structures, followed by BLASTn comparisons of their partial 28S rRNA gene sequences. Two dactylogyrid species, Dactylogyrus labro sp. n. and Dogielius salpinx sp. n., were recovered and are described herein as new to science. Dactylogyrus labro was found to infect all examined fish, whereas D. salpinx had a slightly lower prevalence, ranging from 76.5% to 83.3% across different sampling sites. The phylogenetic insights from these species presented in this study highlight the complex evolutionary relationships within these three genera. Further, this study provides the first confirmed molecular data for a Dogielius species, allowing for much-needed phylogenetic studies on the genus and filling a gap in sequencing data for Indian monogeneans. Since all monogeneans are potentially hazardous parasites, more studies are needed to map their diversity and effects on host fishes in this region.

We report the first identification of nematode parasitism in a nemertean host (Arctostemma arcticum), representing a novel host-parasite interaction in marine ecosystems. Larvae of the anisakid nematode were discovered within the rhynchocoel of A. arcticum collected from the White Sea, suggesting transmission via ingestion of infected crustaceans – a previously undocumented pathway. The nematode was identified as Phocanema bulbosum through both morphological and molecular analyses.

The presence of nematode in nemertean A. arcticum implies trophic transmission through nemertean predation on infected amphipods, supported by hoplonemertean feeding strategy. While some fish occasionally consume nemerteans, their low predation frequency suggests A. arcticum could act as a dead-end host.

This study expands the known host range of Anisakidae, though it remains uncertain whether nemerteans serve as competent hosts in the P. bulbosum life cycle. Nevertheless, the findings highlight the need to assess nemerteans’ potential influence on parasite dynamics in fisheries and aquaculture, particularly where they coexist with intermediate and definitive hosts.

The genus Aphelenchoides Fischer, 1894, encompasses nearly 200 species with significant ecological and economic importance, yet its taxonomy remains complex due to morphological similarities among species and limited molecular data. In this study, we describe a new species, Aphelenchoides vinhphucensis sp. n., collected from the rhizosphere of rice (Oryza sativa L.) in Vinh Phuc Province, Vietnam. The new species is distinguished by its morphological characteristics, including a slender stylet (9.6–12.7 μm), distinct lateral fields with four lines, a conical tail with a pointed mucro, and a well-developed post-uterine sac. Males feature three pairs of caudal papillae and arcuate spicules. Scanning electron microscopy provided detailed insights into surface features, complementing light microscopy observations. Molecular analyses of the D2-D3 regions of 28S rRNA and 18S rRNA supported the distinct phylogenetic placement of Aphelenchoides vinhphucensis sp. n., differentiating it from closely related species. Bayesian phylogenetic analysis confirmed its divergence, contributing to our understanding of biodiversity of the genus Aphelenchoides. This integrative approach highlights the importance of combining classical morphological methods with modern molecular tools for accurate species identification. The discovery of Aphelenchoides vinhphucensis sp. n. underscores the nematode diversity in Vietnam, especially those associated with rice cultivation.

This study presents data on helminth communities from 93 Hooded Crows (Corvus cornix). The dataset includes historical and contemporary records from three localities in Ukraine with different levels of urbanisation: Kyiv, the Middle Dnipro River, and Polissya. Thirty-two helminth species were identified, including 14 trematodes, six cestodes, 11 nematodes, and one acanthocephalan. The nematodes Eufilariella delicata and Hadjelia truncata are documented in Hooded Crows for the first time. During the statistical analysis, it was revealed that the used dataset is insufficient for robust inference regarding the impact of urbanisation on helminth communities due to its temporal and spatial biases. Despite the limitation, the data offer information for future research on the influence of urbanisation on helminth biodiversity in avian hosts.