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.

A novel entomopathogenic nematode (EPN) species, Steinernema tarimense n. sp., was isolated from soil samples collected in a Populus euphratica forest located in Yuli County within the Tarim Basin of Xinjiang, China. Integrated morphological and molecular analyses consistently place S. tarimense n. sp. within the ‘kushidai-clade’. The infective juvenile (IJ) of new species is characterized by a body length of 674–1010 μm, excretory pore located 53–80 μm from anterior end, nerve ring positioned 85–131 μm from anterior end, pharynx base situated 111–162 μm from anterior end, a tail length of 41–56 μm, and the ratios D% = 42.0–66.6, E% = 116.2–184.4, and H% = 25.5–45.1. The first-generation male of the new species is characterized by a curved spicule length of 61–89 μm, gubernaculum length of 41–58 μm, and ratios D% = 36.8–66.2, SW% = 117.0–206.1, and GS% = 54.8–82.0. Additionally, the tail of first-generation female is conoid with a minute mucron. Phylogenetic analyses of ITS, 28S, and mt12S sequences demonstrated that the three isolates of S. tarimense n. sp. are conspecific and form a sister clade to members of the ‘kushidai-clade’ including S. akhursti, S. anantnagense, S. kushidai, and S. populi. Notably, the IJs of the new species exhibited faster development at 25°C compared to other Steinernema species. This represents the first described of an indigenous EPN species from Xinjiang, suggesting its potential as a novel biocontrol agent against local pests.

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.

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.

A variety of larvae and parthenitae of trematodes have been detected in gastropods in the intertidal zone in Japan. However, because of the difficulty associated with the morphological identification of these stages, they have rarely been identified to the species or higher taxonomic levels. In this study, trematodes of these stages were sampled from intertidal gastropods in the Japanese coastal regions and were identified to the species, genus, or family levels morphologically and molecularly to elucidate or predict their life cycles. Investigation of 17 gastropod species (682 individuals in total) from 14 localities led to the detection of trematodes in 47 individuals belonging to six snail species. The infected gastropods were morphologically identified as Nipponacmea fuscoviridis, Monodonta confusa, Trochus sacellum, Batillaria attramentaria, Littorina brevicula, and Purpuradusta gracilis. Our molecular analyses revealed that sporocysts, rediae, and metacercariae from the gastropods were divided into 14 species belonging to nine families: Philophthalmidae, Fellodistomidae, Gymnophallidae, Lepocreadiidae, Heterophyidae, Opisthorchiidae, Notocotylidae, Microphallidae, and Opecoelidae. These trematodes were thought to use fishes, octopuses, seabirds, and marine mammals as their definitive hosts. Marine organisms such as jellyfishes, crustaceans, and fishes are also thought to act as the second intermediate and paratenic hosts of few present trematode species. As for the other trematode species, DNA barcodes of trematodes from various marine organisms will also illuminate the life cycles in future.

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.

Haemonchus contortus is a parasitic nematode that causes significant economic losses in ruminant livestock worldwide. In this study, we assessed the global genetic diversity and population structure of H. contortus using mitochondrial COX1 and ribosomal ITS2 sequences retrieved from the NCBI GenBank database. In total, 324 haplotypes of the COX1 and 72 haplotypes of the ITS2 were identified. The haplotype diversity values were all higher than 0.5, and the nucleotide diversity values were higher than 0.005. The Tajima’s D value for COX1 (−1.65634) was higher than that for ITS2 (−2.60400). Fu’s Fs, Fu and Li’s D (FLD), and Fu and Li’s F (FLF) values also showed high negative values, indicating a high probability of future population growth. In addition, the high fixation index (FST) value suggests significant genetic differentiation among populations. The haplotype networks of H. contortus populations based on COX1 sequences revealed clear geographic clustering, whereas ITS2 sequences showed more haplotype admixture across regions. The results of phylogenetic analyses were consistent with the haplotype networks. These findings highlighted that H. contortus populations exhibit significant genetic variation and are undergoing rapid population expansion, with clear genetic differences across geographic regions. This study established critical baseline data for future molecular epidemiology studies, which could guide region-specific parasite surveillance and targeted control strategies, thus helping to mitigate the risk of cross-border parasite transmission and drug resistance.

The freshwater fish fauna of southern Africa is highly diverse; however, the magnitude of parasitic species they host is unevenly known. The region’s documented adult trematode fish fauna is sparse, while the opposite is evident for intermediate trematode stages. Perceived difficulty in identification of underdeveloped stages lead to the exclusion of reporting metacercariae or lack either morphological or molecular data resulting in a depauperate comparative molecular data repository for species of the region and Africa as a whole. In an effort to address the morphological and molecular data void of the parasite fauna of southern African freshwater fishes, we sought to comprehensively investigate and characterise this fauna. Here we report on three metacercarial forms of Clinostomum (Clinostomidae) from three fish families (Clariidae, Mochokidae, and Mormyridae), provide the first report of a species of the Cryptogonimidae from a cyprinid host in South Africa, and include molecular data for the partial 28S rDNA, ITS1–2 and COI mtDNA regions of these metacercarial forms. Our clinostomid specimens morphologically and genetically corresponded with Clinostomum brieni (e.g., Clarias gariepinus) and Clinostomum ‘morphotype 2’ and ‘morphotype 3’ per Caffara et al. (2017) from the mormyrid Marcusenius pongolensis and the mochokid catfish Chiloglanis sp., respectively. Our cryptogonimid metacercariae did not correspond with any known species or available molecular sequence data; however, the presence of robust circumoral spines on the oral sucker indicated that they are either a species of Acanthostomum or Proctocaecum. The molecular data we provide are the first for an Acanthostomum/Proctocaecum-type cryptogonimid from Africa.

During nematode surveys conducted to investigate the biodiversity of plant-parasitic nematodes in Mediterranean olive groves with different management strategies (organic and conventional), a nematode population of the genus Neothada was detected in southern Spain. Application of integrative taxonomical approaches clearly demonstrated that it is a new species described herein as Neothada olearum sp. nov., also representing the first report of the genus in Spain. The new species is amphimictic, characterised by a short body (563–774 μm); cuticle widely annulated (2.5–3.0 μm); total number of body annuli 214–226; 16 longitudinal ridges giving a tessellate body surface; stylet without distinct basal knobs (9.0–11.0 μm); and tail elongate-conoid, with tip bluntly rounded. The results of molecular analysis of D2-D3 28S rRNA, ITS rRNA, partial 18S rRNA, and cytochrome oxidase c subunit 1 (COI) gene sequences support for the new species status and clearly separated from N. major and other species within Neothada. Phylogenetic analyses of ribosomal and mitochondrial markers of this study suggested that Neothada is a monophyletic genus, clearly separated from Thada.

Microbiomes are communities of microorganisms that form close associations with metazoan hosts and have important roles in host biological processes. With the advent of Next Generation Sequencing, the microbiomes of myriad animals and plants have been described. However, the microbiomes of parasites have received little attention, which is surprising considering their ecological and medical importance. This study characterizes, for the first time, the microbiome of Dujardinascaris helicina, a gastrointestinal nematode parasite of the American crocodile. Dujardinascaris helicina were isolated from crocodiles residing in two geographically separated habitats across Belize. Using 16S sequencing, we compare β-diversity between sampling locations using generalized linear mixed modeling. Our results show that D. helicina microbiomes differ in composition depending on location. We also show that D. helicina microbiomes show strong shifts toward consolidation of specific taxa when proximity to human modified environments increases.

Fasciolosis, a parasitic disease of ruminants, poses significant economic and animal-health challenges in Algeria. This study aimed to assess spatial, temporal, and species-specific patterns of fasciolosis prevalence across diverse agro-climatic zones and to estimate associated economic losses. Between 2013 and 2023, eight wilayas El-Tarf, Skikda, Jijel (Region I), Blida, Mila (Region II), and M’Sila, Medea, Laghouat (Region III) were surveyed. Systematic postmortem inspections of 1,569,392 animals (349,176 cattle; 982,669 sheep; 235,639 goats; 1,882 camels; 26 horses) were performed by qualified veterinarians, with liver and bile-duct examination for Fasciola. Data on region, species, year, and season were analyzed in R 4.4.0 using ANOVA, Kruskal–Wallis, Tukey’s post hoc tests, and principal component analysis (PCA). Economic losses were calculated from condemned liver weights in Blida, Laghouat, and Jijel, converted to USD. PCA distinguished three regional prevalence profiles, with PC1 (77.7% variance) separating overall prevalence levels. Region I exhibited the highest mean prevalence (2.47%), peaking at 3.54% in 2018 – significantly greater than Region II (1.39%) and Region III (1.96%) (p < 0.01). Cattle showed the greatest infection rate (mean 4.14%), significantly higher than sheep (1.32%; p < 0.001) and goats (0.25%; p < 0.001), while horses and camels remained uninfected. Seasonal analysis revealed highest prevalence in autumn and winter (≈2.1%) versus spring (≈1.5%). Economic losses totaled USD 10.6 million in Blida, USD 1.0 million in Laghouat, and USD 142.2 million in Jijel over the study period. Targeted control strategies, adapted to regional and seasonal risk patterns, are essential. Future work should investigate environmental and management factors driving regional differences and evaluate cost-effective interventions to mitigate fasciolosis impact in Algerian livestock.

Kalicephalus (Molin, 1861) comprises 33 species of gastrointestinal snake and lizard parasites with a cosmopolitan distribution, with seven taxa occurring in the Neotropical realm. In the present study, we describe Kalicephalus atroxi n. sp., found parasitising the snake Bothrops atrox, from the Eastern Amazon in the State of Amapá, North of Brazil. We used an integrative approach that included light microscopy, scanning electron microscopy, and sequencing of the internal transcribed spacer 1 (ITS1) region to describe Kalicephalus atroxi n. sp. The new species has a buccal capsule characteristic of the genus, a slight cuticular inflation in the cephalic region. The females have an amphidelphic reproductive system, a vulva with prominent lips, and a long tail, tapering posteriorly. The males have long and alate spicules, and the copulatory bursa is lobed with dorsal rays with distinct morphology compared to their congeners. Molecular analyses and phylogenetic reconstructions cluster the new species into a well-supported clade with K. costatus costatus, from Chironius fuscus, from the same locality in northern Brazil. Kalicephalus atroxi n. sp. is the eighth species of the genus in the Neotropics, the seventh in Brazil, the second described parasitising B. atrox in Brazil, and the first species of snake nematode described in the State of Amapá.

A new species of Loimos MacCallum, 1917 is described more than half a century after the last species was described in 1972. The new species was collected from the gills of Rhizoprionodon taylori (Ogilby, 1915) off the Central Queensland coast, Australia, and is the first Loimos species and the first representative of the Loimoinae Price, 1936 known from Oceania. A detailed morphological description and 28S rDNA molecular sequences are provided for the new species. In the molecular phylogeny based on available 28S rDNA sequences for relevant Monocotylidae, the new species grouped together with the only other Loimos sequence available in GenBank, that of the nonugen Loimos sp. from China (OM060238), sister to Loimosina wilsoni Manter, 1944. The estimated genetic divergence between the new species and the nonugen Loimos sp. sequence is low, between 0.0452 and 0.0737, suggesting that the nonugen sequence may represent the new species, or a very closely related congener. Host identity was confirmed by comparing COI sequences with those of known sharks in GenBank. We also provide the first 12S and 16S molecular sequences for this shark species.

Trematodes of the genus Paralecithodendrium parasitize bats worldwide. Among them, the identification of Paralecithodendrium longiforme and Paralecithodendrium cryptolecithum is complicated by their high morphological similarity. We studied Paralecithodendrium trematodes from the small intestine of bats inhabiting the Middle Volga region (European Russia). The aim of our study was to analyze these two Paralecithodendrium species using both morphological and molecular phylogenetic approaches. Here, we present the first complete morphological description and molecular phylogenetic analysis of Paralecithodendrium cryptolecithum from bats in Russia and confirm the validity of this species.

Over the years, the number of parasitic helminth species discoveries has not ceased to increase and the popularisation of the use of molecular methods has contributed greatly to sustain the growth in knowledge. However, molecular approaches evolved rapidly in the last 20 years. I argue that the research community working on parasitic helminths has lagged behind in the application of molecular methods that examine multiple loci to study species diversity. In this paper, I review the recent historical trends in the molecular markers used to study trematode diversity. Except for the emergence of pioneer mitogenome studies, the use of markers has not changed in the past 10 years. It is still restricted to single locus or a combination of two, rarely three, mitochondrial and ribosomal loci. I identify past and current molecular approaches providing data on multiple loci across the genome which have found resistance in the trematode and the helminth parasitology fields over the last four decades. I discuss how the knowledge gained from the analysis of genome-wide markers would benefit research on parasite diversity today, in particular for cases of species complexes, cryptic (or nearly cryptic) species, recently diverged species, and species with a complex taxonomic history, or a history of suspected mitonuclear discordance as well as for taxa with wide geographical distributions or species with disjoint distributions. Furthermore, I argue that both, studies with classical markers and reduced-representation genome studies providing genome-wide markers should not walk different paths but feedback on each other to advance the field forward. I examine some challenges and make recommendations for obtaining high-throughput molecular data of parasitic helminths.

Five species of monorchiids are known from fishes of the family Gerreidae, of which one is from Australian waters. Here, we report it and two new monorchiids from three species of Gerres Quoy & Gaimard, 1824 from off Lizard Island, northern Great Barrier Reef, and Moreton Bay in south-eastern Queensland: Gerres oyena (Forsskål), Gerres oblongus Cuvier and Gerres subfasciatus Cuvier. One of the new species, found only in G. oblongus at Lizard Island, conforms most closely to the concept of Proctotrema Odhner, 1911. However, it differs from species of Proctotrema in oral sucker shape and location of intestinal bifurcation and termination. It is phylogenetically distinct from two sequenced species of Proctotrema; thus, we propose Obscuromonorchis ranae n. g., n. sp. The second new species infects all three gerreids, occurs at both Lizard Island and Moreton Bay, and is morphologically most similar to the concept of Monorchicestrahelmins Yamaguti, 1971. However, the combination of the length of the caeca, size of the testis and post-testicular region, and the form of spination in the genital atrium presents a clear genus-level distinction that warrants proposal of a new genus. There are no molecular data for the three recognised species of Monorchicestrahelmins. We propose Argenticola shuyinae n. g., n. sp. for this species. New specimens of Gerricola queenslandensis Wee, Cutmore & Cribb, 2021 were collected from off Lizard Island and Moreton Bay. The three species form a well-supported clade but with internal branch lengths and topology consistent with genus-level differentiation.

Data on the infection of Middendorffʼs eelpout, Hadropareia middendorffii, by metacercariae of the trematodes Cryptocotyle lingua Creplin, 1825 and Liliatrema skrjabini Gubanov, 1953, which are causative agents of black spot disease, is provided here for the first time for Taui Bay, Sea of Okhotsk. The prevalence of infection of fish by larvae of C. lingua reached 79%, while the intensity of infection varied from one to 278 individuals (with an average of 53). The prevalence of infection by L. skrjabini was lower (40%), with an intensity from one to 22 larvae (on average, eight). Metacercariae of both trematode species were surrounded by two envelopes: an outer, connective tissue capsule formed by the host’s cells, and an inner cyst formed by the parasite. The examined metacercariae were found in all regions of the fish’s body (head, trunk, and fins), with approximately equal numbers of individuals of both species found in tissues of the head and trunk regions. Metacercariae of C. lingua were localised in the fishes’ muscles, not only immediately under the skin but also in deeper layers. The capsules formed around metacercariae of both trematode species were dominated by fibroblasts and collagen fibres and did not show pronounced signs of inflammation. Studying the distribution of black spot disease and its effects on fish is crucial for understanding disease patterns in relation to fish population dynamics. It may also inform the development of effective anthelmintic treatments for use in aquaculture farms.

Genetic evidence indicates that Progamotaenia macropodis Beveridge, 1976 (Cestoda: Anoplocephalidae), found in various macropodid host species, is a complex of cryptic species. However, the genetic data are incomplete, and no morphological re-appraisal of the species has been undertaken since its original description. Here, additional mitochondrial cytochrome c oxidase I sequence data have been added from the type host, Macropus giganteus, as well as other host species, and a morphological study of all available material undertaken. A new species, Progamotaenia mollicula sp. nov., is erected for specimens from the tammar wallaby, Notamacropus eugenii, which are smaller, and the testes in pre-mature and mature proglottids occur invariably in two lateral groups. Specimens from the remaining host species, Macropus fuliginosus, Notamacropus parryi, N. rufogriseus, Osphranter robustus, and Wallabia bicolor are highly variable with obvious differences in length and proglottid shape, but with no reliable internal morphological characters for separating the various genotypes. The study was limited by incomplete molecular data (N. rufogriseus) and the poor quality of some of the preserved material.

Trichinellosis is a parasitic zoonosis caused by a nematode parasite of the Trichinella (T.) genus. It poses significant public health issues due to limited effective and safe treatment options, especially for the muscle-encysted larval stage. Citrus paradisi (C. paradisi), with its high content of flavonoids and polyphenols, has been recorded to possess anti-parasitic properties and numerous therapeutic applications. The present work aimed to assess the efficacy of C. paradisi extract peel extract as a therapeutic agent, either alone or combined with albendazole (ABZ), against T. spiralis in experimentally infected mice. Sixty-six lab-bred Swiss albino mice were divided into control and treatment groups, then received either ABZ, C. paradisi extract, or a combination of both during the enteral, migratory, and encapsulation phases of infection. Parasitological, histopathological, and immunohistochemical examinations were performed to evaluate the efficacy of the treatments. All treated groups displayed a highly significant difference (p < 0.001) in larval counts compared to the positive control group, with the combination therapy group having the highest efficacy and the lowest mean count value during different treatment regimens. In addition, treated groups showed improved muscle integrity compared to the positive control group. Moreover, the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) showed the highest expression reduction in the combination therapy group. These findings highlight the potential of C. paradisi as a complementary therapy to albendazole for treating trichinellosis through muscle larva reduction and mitigation of inflammation.

Cystic echinococcosis is a zoonosis caused by Echinococcus granulosus sensu lato, which leads to serious public health problems. Considerable phenotypic variation has been described between parasites depending on the intermediate host and genotype. Knowledge of species/genotypes present in an endemic region is clue for control programs. Although DNA sequencing is the most accurate tool for this purpose, its high cost makes it less affordable. A multivariate study of the morphometric parameters of rostellar hooks of E. granulosus sensu lato of human origin from Neuquén was carried out using Principal Components Analysis and classification trees. A valid classification criterion to differentiate E. granulosus species using morphometry of rostellar hooks in human hydatid cysts was determined. Seventy-six human fertile hydatid cysts (48 E. granulosus sensu stricto G1 and G3, and 28 E. canadensis G6) were included. Overall, 2,280 hooks were measured. The rostellar hooks belonging to E. granulosus sensu stricto were significantly smaller than those of E. canadensis. The Large Total Length (LTL) was sufficient to classify a new isolate into the 2 species: if LTL < 25.3 μm, then it corresponds to E. granulosus sensu stricto, and if LTL ≥ 25.3 μm to E. canadensis. This is the first multivariate study that establishes a morphometric cut-off value to discriminate between 2 species of E. granulosus sensu lato from human patients, using a significant number of cysts of both species identified by sequencing of mitochondrial genes. It constitutes a useful predictive tool in endemic areas where both human infective species overlap.