The nematodes isolated from three species of Chanodichthys were completely consistent with the morphological description of Rhabdochona coronacauda. We provide new morphometric data for R. coronacauda, which slightly differ from those of the original description. For the first time, we performed a phylogenetic analysis by using both primary (linear) and secondary (folded structures) sequences of the complete 18S rRNA gene for three superfamilies of Spiruromorpha. The interspecific genetic distances within the genus Rhabdochona were 0.13%–3.06% between 18 species. Rhabdochona coronacauda was sister to a sub-group consisting of the type species R. denudata, R. hospeti, R. hellichi, and R. turkestanica. The secondary structures reconstructed for 35 species of three superfamilies from the order Spiruromorpha comprised 16 conformations of the region including helix 39 and expansion segment 9, and two conformations of helix 17. Helix 39 can be used to differentiate single species or separate species groups of Rhabdochona. The structures of helix 39 in both Rhabdochonidae and Cystidicolidae with Salmonema had an identical 39a domain but differed in the 39b domain and expansion segment 9. In addition, the structure of the helix 39–expansion segment 9 domain within and between families of different superfamilies and their resolution on the phylogenetic tree in combination did not correspond to the accepted classification of spiruromorph nematodes. Helix 17 did not differ within Rhabdochona, or between Rhabdochonidae and Cystidicolidae. At the superfamily level, helix 17 can distinguish Thelazioidea, Spiruroidea, and Habronematoidea from Rhabdochonidae, and Cystidicolidae from Spirocercidae, Thelaziidae, and Pneumospiruridae.

Metacercariae of Diplostomum spp. are widespread fish parasites. In this study we obtained the first data on infection of Bullhead Cottus koshewnikowi with these larvae in five rivers of northern Europe (Finland and Russia) using molecular and morphological description. Three Diplostomum spp. were revealed in the eyes of bullheads. Diplostomum spathaceum and D. mergi Lineage 3 sensu Georgieva et al. (2013) were found in the lens, while Diplostomum sp. Lineage 6 sensu Blasco-Costa et al. (2014) was found in the retina. We obtained molecular data on these three species and provided morphological characteristics of the latter two species. Partial sequences of the cytochrome c oxidase subunit 1 (cox1) and ITS1-5.8S-ITS2 were amplified for 20 isolates. Using molecular data, we ascertained the species identification and obtained new information on the life cycles of D. mergi Lineage 3 and Diplostomum sp. Lineage 6. Partial cox1 sequences were used to assess the haplotype diversity of D. mergi Lineage 3 and Diplostomum sp. Lineage 6 in the study area. Discriminant analysis showed that D. mergi Lineage 3 was morphometrically close both to the species of the lens complex (D. mergi Lineage 2, D. mergi, D. nordmanni, and D. parviventosum) and to the species from the retina (D. pungiti, D. volvens). Dimensions of Diplostomum gobiorum lay far outside the confidence interval of D. mergi Lineage 3. Our molecular and morphological data and the new information about the hosts and the distribution of these parasites are a crucial step towards elucidating the diversity and life cycles of these important parasites. The data on the infection of bullheads in the River Utsjoki (a tributary of the River Teno, Finland) with metacercariae of Diplostomum spp. offer some insights into the relationships between the introduced host and the native parasites. Infection of bullheads, which are considered invasive in the Teno River system, with metacercariae of Diplostomum spp. may lead to increased infection levels in resident fish.

Echinococcus equinus is a parasitic cestode primarily maintained within an equine-canine life cycle, with horses, donkeys, mules, and other ungulates serving as intermediate hosts. Although E. equinus has historically been considered non-zoonotic, recent molecular studies suggest that this assumption may need to be reevaluated. This study aimed to investigate the presence and molecular characterization of E. equinus in equids from Türkiye. A retrospective analysis of 52 equine necropsies performed between 2020 and 2025 identified hydatid cysts in one Arabian horse and two donkeys. Gross and histopathological examination confirmed the presence of hydatid cysts in the liver and lungs, exhibiting characteristic structural features. Molecular identification was conducted through PCR amplification targeting the mitochondrial cytochrome c oxidase subunit 1 (mt-CO1) gene, with all positive samples confirmed as E. equinus through sequence analysis. Phylogenetic analysis demonstrated a close relationship between the obtained sequences and reference E. equinus strains from other geographic regions. These findings provide the molecular confirmation of E. equinus in equids from Türkiye and underscore the need for targeted surveillance to better understand its distribution, transmission, and zoonotic relevance, especially considering the first confirmed human case reported in the country in 2021.

The interaction of helminth infections with type 2 diabetes (T2D) has been a major area of research in the past few years. This paper, therefore, focuses on the systematic review of the effects of helminthic infections on metabolism and immune regulation related to T2D, with mechanisms through which both direct and indirect effects are mediated. Specifically, the possible therapeutic role of helminths in T2D management, probably mediated through the modulation of host metabolic pathways and immune responses, is of special interest. This paper discusses the current possibilities for translating helminth therapy from basic laboratory research to clinical application, as well as existing and future challenges. Although preliminary studies suggest the potential for helminth therapy for T2D patients, their safety and efficacy still need to be confirmed by larger-scale clinical studies.

Cryphodera guangdongensis n. sp. was collected from the soil and roots of Schima superba in Guangdong province, China. The new species is characterised by having a nearly spherical female, with dimensions of length × width = 532.3 (423.8–675.3) × 295.6 (160.0–381.2) μm, stylet length of 35.7 (31.1–42.1) μm, protruding vulval lips, a vulval slit measuring 54.2 (47.4–58.9) μm, an area between the vulva and anus that is flat to concave, and a vulva–anus distance 49.3 (41.1–57.6) μm. The male features two lip annules, a stylet length of 31.7 (27.4–34.8) μm and basal knobs that are slightly projecting anteriorly, while lateral field is areolated with three incisures and spicules length of 27.1 (23.7–31.0) μm. The second stage juvenile is characterised by a body length of 506.1 (441.8–564.4) μm long, two to three lip annules, a stylet length 31.2 (29.7–33.2) μm which is well developed, basal knobs projecting anteriorly, a lateral field that is areolate with three incisures, and a narrow rounded tail measuring 63.2 (54.2–71.3) μm long, with a hyaline region of 35.6 (27.4–56.6) μm long that is longer than the stylet. Based on morphology and morphometrics, the new species is closely related to C. sinensis and C. japonicum within the genus Cryphodera. The phylogenetic trees constructed based on the ITS-rRNA, 28S-rRNA D2–D3 region, and the partial COI gene sequences indicate that the new species clusters with other Cryphodera species but maintains in a separated subgroup. A key to the species of the genus Cryphodera is also provided in this study.