Limpets are abundant and ecologically important gastropods in intertidal and some riverine ecosystems, yet their role in trematode transmission remains comparatively understudied. We investigated trematode infection in intertidal limpets from Otago Harbour, New Zealand, using a molecular approach. Two species were identified: the avian schistosome Gigantobilharzia cf. patagonensis in Siphonaria australis and Acanthoparyphium sp. A metacercariae in Notoacmea sp. Gigantobilharzia cf. patagonensis was detected at all five sampling sites, with prevalence ranging from 2.6% to 100%. Haplotype network analysis using cox1 revealed high haplotype diversity and a star-like topology, suggesting a recent population expansion. This study expanded the known diversity of marine schistosomes in the region and raises potential public health concerns with cercarial dermatitis. We also conducted a literature synthesis further demonstrating that limpets contribute to trematode transmission across 12 superfamilies and 23 families, with distinct parasitism profiles between freshwater and marine environments. These findings highlight limpets as overlooked but significant hosts in trematode ecology and emphasize the need for broader surveys and definitive host screening to resolve incomplete life cycles and assess epidemiological risks in coastal ecosystems.

Seabirds are largely used as indicators of Ocean health and are final hosts of several helminth parasites. However, the helminth fauna of seabirds is still poorly studied. Here, we quantified the diversity of gastrointestinal parasites in 52 individuals belonging to 10 seabird species with different habitat preferences and feeding strategies from the North-East Atlantic and Antarctica. Fresh carcasses were collected in Northern France and at Svarthamaren (Dronning Maud Land, Antarctica), helminth parasites were extracted from the gastrointestinal tract, and were identified by morphological inspection and DNA barcoding. In total, we identified 13 helminth taxa. North-East Atlantic seabirds hosted parasites from four helminth groups (Acanthocephala, Cestoda, Nematoda, Trematoda), while Antarctic seabirds hosted Acanthocephala and Cestoda only. The largest parasite diversity was found in northern fulmars Fulmarus glacialis (9 species), European shags Gulosus aristotelis (5 species), razorbills Alca torda (4 species), and black-legged kittiwakes Rissa tridactyla (4 species). Co-infections with multiple parasite species in single hosts were common. Oceanic diving species were found to be the most parasite-poor, with common guillemots Uria aalge and Atlantic puffins Fratercula arctica hosting no parasites. In contrast, oceanic surface-feeding seabirds had a large parasite diversity, which notably included trematodes, and was comparable to that of coastal species. To the best of our knowledge, this study identified 9 new host-parasite associations: Andracantha sp. in northern fulmars and south polar skuas Stercorarius maccormicki, C. septentrionale in northern fulmars and black-legged kittiwakes, a species of Microphallidae in black-legged kittiwakes, Cardiocephaloides longicollis in European shags, Cryptocotyle lingua in Sandwich terns Thalasseus sandvicensis, and a clophyllidean species in south polar skuas and Antarctic petrels Thalassoica antarctica.

We describe the marine horsehair worm Nectonema shimadai sp. nov., which was parasitic in a snapping shrimp (Alpheus sp.) collected at 4 m depth from the coastal water of Kikaijima Island, Japan, northwestern Pacific. The nematomorph was a female, 49 mm in length and 340 μm in width, salmon-pink when alive, with a translucent anterior body region and a distinct anterior chamber. The 18S sequence from N. shimadai sp. nov. was 12.8%, 9.8%, 9.6%, and 9.3% divergent in Kimura 2-parametar (K2P) distance from Nectonema sp. parasitic in the isopod Natatolana japonensis, Nectonema sp. parasitic in the crab Chionoecetes bairdi, N. munidae, and N. agile, respectively. In an 18S tree, N. shimadai sp. nov. was the sister taxon to a clade comprising three decapod-parasitic species, and species sharing the same host group or ocean were not monophyletic. The tree may reflect genetically distant warm- and cold-water lineages within decapod-parasitic nematomorphs.

Foodborne trematodes, particularly from families Opisthorchiidae and Fasciolidae, significantly impact human health. Research on trematode-related diseases has primarily focused on the hepatobiliary system and carcinogenic potential of these flukes. Nonetheless, chronic infection by these parasites likely affects other organ systems. This review emphasises the need to expand studies beyond the hepatobiliary system to fully understand the pathogenesis of liver fluke infections and advocates for a systematic approach to the management of affected humans. This review analyses scientific data from 1950 to 2025, including studies on laboratory animals, wild animals, and humans. Databases such as PubMed, Google Scholar, WHO, IARC, Rospotrebnadzor, and eLibrary were utilised. Common kidney injuries from trematode infections include glomerular and tubular damage, interstitial inflammation, and fibrosis. These injuries are influenced by liver damage and gut microbiome imbalances. Interspecies differences highlight the complexity of host–parasite interactions. Research indicates that foodborne-trematode–associated nephropathy exists in both humans and animals and involves immune complexes, oxidative stress, and biomarkers like KIM1. The documented renal damage underscores the need for further investigation into the mechanisms of the trematode-associated renal pathologies.

Domestic cats are the only felines living exclusively with humans, making them ecologically invasive and widespread across terrestrial habitats. Their domestication stems from their rodent control abilities and companionship. However, they are susceptible to gastrointestinal parasites such as Ancylostoma spp., Toxocara cati, and Dipylidium caninum, causing issues like anaemia, vomiting, and sometimes death, especially in kittens. These parasites can also pose zoonotic risks, transmitting diseases like visceral and ocular larva migrants to humans. A total of 100 cats with no deworming history were examined over six months. The overall prevalence of intestinal helminths was 23.0%, with Ancylostoma spp. being the most common (11.0%), followed by Toxocara cati (7.0%), Taenia spp. (2.0%), and mixed infections (3.0%). The prevalence was higher in females (26.92%) than in males (18.75%). Age-wise, kittens under 6 months had the highest infection rate (36.17%), while cats aged 6–12 months showed the lowest (10.71%). Non-descriptive breeds exhibited a higher infection rate (34.88%) than descriptive breeds (14.03%). Most cats were kept in confined spaces (72.0%), with 57.0% being descriptive breeds. Cats were mostly fed a mix of cooked and commercial cat food (59.0%), while only 33.0% were vaccinated and 20.0% dewormed. Behavioural issues like licking (51.0%) and self-biting (13.0%) were noted. Only 41.0% of owners were aware of zoonotic disease risks from cats. Chi-square analysis revealed significant associations between infection rates and risk factors (variables) such as breed, age, diet, vaccination, and deworming status. Non-descriptive breeds, unvaccinated cats, and those fed vegetarian diets had significantly higher infection rates (p < 0.05). Unconfined housing also contributed to increased infection risk, though not statistically significant. The research was significant because it highlighted the public health risks, as many cat owners and pet lovers were unaware of the zoonotic potential of intestinal helminths in cats.

During a helminthological survey conducted in the southern Peruvian Amazon, nematodes representing an undescribed species of Aplectana Railliet & Henry, 1916 (Cosmocercidae) were recovered from the intestine of Leptodactylus bolivianus Boulenger, 1898 (Anura: Leptodactylidae). The new species, Aplectana peruensis n. sp., is described herein based on an integrative taxonomic approach combining detailed morphological analysis using light and scanning electron microscopy with molecular characterization of the partial 18S rDNA gene. Aplectana peruensis n. sp. is distinguished from its congeners by a unique combination of characters, including 13 pairs of caudal papillae (3 precloacal, 5 adcloacal, and 5 poscloacal papillae) plus a single unpaired papilla, the presence of a gubernaculum, and relatively long spicules (152–194) with a clearly defined distal bifurcation. Phylogenetic analyses based on Bayesian inference methods recovered the new species as a well-supported sister lineage to A. hylambatis (Baylis, 1927) from the Neotropical region. Genetic divergence values further support its specific distinctiveness. This study represents the first description of an Aplectana species from L. bolivianus in the Amazon region of Peru and increases the number of recognized species within the genus.

Ascaris species are common soil-transmitted helminths infecting both humans and pigs. It is recognized as one of the Neglected Tropical Diseases and is currently targeted in global eradication initiatives. This study employed mitochondrial ‘NADH dehydrogenase subunit 1 NAnad1) and Cytochrome Oxidase 1 (cox1) gene’ sequences comprising newly generated and publicly available data to investigate the genetic diversity, evolutionary relationships, and potential zoonotic transmission between Ascaris lumbricoides and Ascaris suum. Phylogenetic analysis revealed distinct clustering, with Indian A. lumbricoides sequences showing close genetic affinity to Chinese and Brazilian sequences (Human and Pigs), indicating possible historical gene flow. This genetic relatedness indicates the presence of intra-species variability and supports earlier evidence of potential hybridization between A. lumbricoides and A. suum. Haplotype network analysis based on nad1 identified 27 haplotypes, including both shared and unique variants. Hap_1 and Hap_2 were widely distributed, while several Indian haplotypes were distinct, suggesting localized diversification or genetic divergence. Cox1-based analysis identified 25 haplotypes, with human sequences forming both global and region-specific clusters, and pig-derived A. suum sequences forming a separate clade. These results highlight substantial genetic diversity and underline the importance of molecular surveillance in understanding Ascaris transmission and zoonotic risk.

Schistosomiasis mansoni, caused by the trematode Schistosoma mansoni, is a major public health issue in Northeastern Brazil. This study compares the diagnostic performance of Kato-Katz (KK) and spontaneous sedimentation (Lutz) techniques in detecting S. mansoni infections in three areas of Sergipe, Northeastern Brazil, each with varying degrees of schistosomiasis endemicity. We compared the performance of Kato-Katz (KK) and spontaneous sedimentation (SSM) in three localities of Sergipe and Alagoas with different endemicity levels. Stool samples were examined by both methods, and individuals were considered positive if at least one test was positive. KK showed higher sensitivity across all sites (88.5%–100%), while SSM performed better in moderately endemic areas (up to 61.5%). These complementary performance profiles suggest that using both methods in combination could yield a measurable increase in case detection – potentially improving prevalence estimates, guiding more accurate treatment interventions, and strengthening surveillance strategies in areas with heterogeneous transmission intensities.

Psalidodon bifasciatus is a small characiform, originally described as endemic to the Iguaçu River basin. However, a recent study recorded a population of P. bifasciatus in the Piquiri River basin (upper Paraná), although data on its geographic distribution and parasitological aspects are still limited. The study characterized the parasitic fauna of P. bifasciatus in two streams, one from each basin, and compared them in terms of richness, diversity, and parasite community structure. Twenty-six females were collected in a stream in the lower Iguaçu River basin, and 25 females in a stream in the Piquiri River basin (upper Paraná) in September 2018. The parasite community structure of P. bifasciatus differed between areas, with a predominance of monopisthocotyls and greater richness of parasitic taxa for hosts in the lower Iguaçu River basin. In the Piquiri River basin (upper Paraná), the parasite community was characterized by a higher prevalence of larval nematodes and a lower richness of parasite taxa. The differences in the richness and structure of the parasite communities between the two areas support the hypothesis of the introduction of P. bifasciatus into the Piquiri River basin (upper Paraná). Therefore, we emphasize the need for further studies addressing the distribution pattern of P. bifasciatus, as well as additional parasitological studies to determine whether the parasitological taxa of P. bifasciatus are shared in other hydrological systems. This study contributes to the knowledge of the biological aspects of P. bifasciatus in both basins and improves our understanding of how host-parasite interactions can be informative in species introduction scenarios.

Climate change is projected to alter the biology and distribution of many helminth species. We investigated the influence of climate on the current distribution of Parapharyngodon sceleratus, a monoxenic, generalist nematode parasite infecting 29 lizard species in South America, and evaluated its potential future range shifts under climate change. Using ecological niche modelling, we predicted the species’ current and future range distributions. Precipitation-related variables were the primary determinants of the spatial distribution of the worm. Areas of medium to high environmental suitability are concentrated in regions with seasonal tropical warm climates, as well as temperate regions with dry summers and mild winters. Future projections indicate a progressive reduction of highly suitable areas and an expansion of areas with low suitability, particularly in northern and central South America, by 2100. However, the Atlantic Forest, the northeastern Brazilian coast, a site within the semiarid Caatinga, and open vegetation areas in Chile persist as refugia of high habitat suitability. Our findings suggest that rising temperatures and altered precipitation patterns may constrict the geographic range of this helminth. Contrary to predictions for other parasite taxa, our results highlight a negative impact of climate change on the distribution of a monoxenic helminth.

Lizards represent a diverse group, adapted to a wide variety of environments, and interact with a wide range of parasites. The composition of a parasitic community can be influenced by several factors, including the host, the environment, and the parasite itself. This study evaluated the composition of the helminth community in three species of lizards of the genera Ameiva, Ameivula, and Tropidurus, from a Carrasco habitat in Chapada do Araripe, Brazil. Carrasco is a little-explored environment in which the diversity of hosts and parasites is still poorly understood. The composition of the helminth community associated with lizard species was evaluated by comparing richness, evenness, dominance, and diversity among component communities, including host sex and size as influencing factors, using different statistical comparison tools. The community consisted of 12 taxa from eight genera of parasitic helminths, seven of which were Nematoda and one Cestoda. The factors analysed had different influences on the different parasitic communities of each host species. It was possible to determine the dissimilarity between host populations based on their parasitic communities, and it was observed that the host species itself represented the most important factor in the structuring of helminth communities. The information recorded here converges with other results obtained in different studies with lizards, but points to patterns in the helminth community that differ from those observed in other areas of the Caatinga. The results obtained reveal complex patterns of association between parasites and hosts, demonstrating the existence of ecological relationships that can be shaped by specific factors.

Nematodes are one of the most diverse groups of organisms, but much of their evolutionary history remains unresolved. Genetic tools have greatly advanced this field, especially in cases of cryptic diversity. Here, we reconstructed the mitogenomes of four parasitic nematodes, each from a different genus of the family Pharyngodonidae (Nematoda: Oxyuroidea): Spauligodon, Pharyngodon, Parapharyngodon, and Thelandros. For each species, whole genome sequencing was performed, using an Illumina HiSeq 2500 platform. Mitochondrial genomes were reconstructed using both reference-based mapping and bait-based iterative assembly approaches. The resulting mitogenomes were 13,692 to 16,700 bp long, included 12 protein-coding genes, 22 tRNAs and the 12S and 16S rRNA regions and all lacked the ATP8 gene. All genes were on the same strand and in the same orientation, which is congruent with the composition and organization observed in other oxyurid nematodes. Also as observed in other nematode groups, the four mitogenomes exhibited major differences in gene order. It is still unknown what promotes such extensive gene order rearrangements within nematodes, even amongst related groups, but it is expected to influence the rates of evolution, especially for parasitic species, and help to explain their impressive diversity.

Research on parasite-induced regulation has identified the conditions under which parasites can destabilise host population dynamics: high levels of aggregation, delayed density-dependence, and moderate negative effects on fitness (reproduction, survival). Gastrointestinal helminths with direct life cycles and a single definitive host provide ideal systems to test these predictions. In this study, we first determined which helminths infect common voles (Microtus arvalis) in NW Spain, where populations are cyclic. We showed that the helminth community is dominated by Syphacia sp., a gut-restricted, directly transmitted nematode.

We then examined how the prevalence and abundance of Syphacia sp. varied with host sex, season, and population cycle phase (increase, peak, or crash), and tested if vole condition (relative body mass and organ hypertrophy) and female fecundity (litter size) correlated with the prevalence of Syphacia sp. Infections were highly aggregated in Syphacia sp. and parasite abundance peaked during the crash phase of the vole cycle. We found that vole condition did not vary with the prevalence of Syphacia sp., but vole litter size showed a season-dependent association, with infected females producing smaller litters in spring and summer.

These findings suggest that even low-pathogenic, directly transmitted parasites could exert reproductive effects, potentially shaping host population dynamics in combination with ecological and demographic factors. Experimental approaches are required to clarify causality and potential regulatory feedback.

Haemonchus contortus is considered the most pathogenic gastrointestinal nematode of sheep and, due to the increasing resistance to synthetic anthelmintics, it poses a serious challenge to small ruminant production systems. The aim of this work was to evaluate the in vivo and in vitro anthelmintic activity of quebracho-chestnut tannin extract against Haemonchus contortus in lambs. The in vitro assays (egg hatching inhibition and larval migration inhibition) were performed to determine the effective concentrations required to inhibit 50% of egg hatching and larval migration (EC50), which were 3.8 and 1.4 mg/mL, respectively. For the in vivo trial, 18 lambs used were divided into three groups: Group 1 (control), Group 2 (a tannin dose equivalent to 0.3% of dry matter intake), and Group 3 (a tannin dose equivalent to 3% of dry matter intake). No significant differences (p > 0.05) were observed among treatments in faecal egg counts, larval counts from coprocultures, or adult H. contortus recovery. The tannin extract was effective in inhibiting egg hatching and larval migration in vitro at low concentrations. However, when administered in vivo at 0.3% and 3% of dry matter intake, it failed to show any effect on faecal egg counts, larval counts in coproculture, or adult worm burden. Adult worms, eggs, and infective larvae were further examined using scanning electron microscopy. The observations revealed significant cuticular alterations in adult worms, which could potentially interfere with normal feeding and reproductive processes. Additionally, eggs and infective larvae exhibited shell rupture and cuticle damage.

A systematic review and meta-analysis were conducted, and published estimates determined the pooled prevalence of gastrointestinal nematode parasites affecting free-ranging chickens in Africa. Peer-reviewed articles published between 1993 and 2024 were systematically searched and screened. Prevalence estimates based on 76 eligible articles showed that of the 74,789 free-ranging chickens screened, 13,625 were infected with gastrointestinal nematodes with an overall pooled prevalence of 15% (95% CI: 13–18%). Twenty-seven nematode species were recorded, of which Ascaridia galli and Heterakis gallinarum were the commonly reported species. Southern Africa recorded the highest pooled prevalence (22%; 95% CI: 13–33%), and western Africa had the lowest (5%; 95% CI: 0–2%) despite recording the highest nematode species diversity. Tetrameridae had the highest family-level pooled prevalence of 46% (95% CI: 28–64%), and Spiruridae had the lowest 1% (95% CI: 0–3%). Most studies were conducted between the period 2014 and 2024; however, the highest pooled prevalence was observed between 1993 and 2002 (17%; 95% CI: 11–24%). The necropsy technique recorded the highest pooled prevalence (17%; 95% CI: 14–20%) compared to coproscopy (10%; 95% CI: 7–14%). The quality effects model revealed a high heterogeneity and publication bias among studies due to the diagnostic method used (P <0.05). This systematic review provided insightful information on the occurrence and potential burden of gastrointestinal nematode species of free-ranging chickens in Africa, highlighting the need for enhanced biosecurity and further research to safeguard their health, production, and food security of rural economies.

Grey seals, Halichoerus grypus (GSs), inhabit cold temperate and subarctic waters along the North Atlantic Ocean. Individuals of GS can regularly disperse towards southern areas (ca. 38°N–39°N) but occurrence at lower latitudes is exceptional. On 18 February 2022, a 217-cm-long male of GS was detected in waters off the SW Atlantic coast of Spain (37°N), then entered the western Mediterranean Sea and wandered for 15 days until he died. Here, we use gastrointestinal parasites to investigate the geographical origin of the GS and the length of the journey towards Mediterranean waters. Seven helminth taxa were found, namely, the digeneans Ascocotyle septentrionalis and Cryptocoyle lingua, the nematodes Contracaecum osculatum s.s., Anisakis simplex s.s., and A. pegreffii, and the acanthocephalans Corynosoma sp.1 and C. magdaleni (= strumosum) or C. nortmeri. The parasite composition closely resembles that reported in native harbour seals (Phoca vitulina) of the Wadden Sea (ca. 51°–55°N), from where A. septentrionalis is apparently endemic. Considering that (i) A. septentrionalis cannot be acquired out of the Wadden Sea, and (ii) the lifespan and population structure of the parasites found, we infer that the GS came from waters near the Wadden Sea, and the length of the journey was ca. 1 month, with presumably little ingestion of (parasitized) food. To our knowledge, this is the first study using parasites to unveil the geographical mobility of pinnipeds.

Differences in testes arrangement and length of post-testicular region between Australian specimens of Paraschistorchis seychellesiensis sensu Magro, Cutmore, Carrasson & Cribb, 2023 and the original description of Paraschistorchis seychellesiensis (Toman, 1989) Blend, Karar & Dronen, 2017 from the Indian Ocean have raised a question whether such variations are intraspecific or interspecific variations. To address this, in-depth morphological descriptions and species delimitation analyses were conducted using a combination of comparative morphology, multivariate classification analyses, and host-parasite data. The Australian population of P. seychellesiensis differs from all known species of Paraschistorchis Blend, Karar & Dronen, 2017 by a broad linguiform body, a ventral sucker noticeably smaller than the oral sucker, a subquadrate pharynx that is partly dorsal to the oral sucker, and testes arrangement in a cluster configuration, as well as its distinct spatial clustering within all multivariate classification analyses without any intrusion into the space occupied by another cluster. Furthermore, the distinctive extension of the anterior vitellarium, significant differences in anterior testis/ovary ratios, and egg sizes indicate that Australian and Indian specimens of P. seychellesiensis are two distinct species. The apparent comparatively distant geographic localities, each with distinct ecosystems (Seychelles Islands vs Great Barrier Reef [GBR], Australia), are an interesting outcome of the recognition of separate species. Accordingly, Paraschistorchis australiensis n. sp. is established to accommodate this Australian record. Given the detailed review and newly added data provided herein, we discuss the nature of the excretory vesicle within schistorchiines and amend the key to the recognized species of Paraschistorchis.

Cercariae of two trematode species from the family Notocotylidae were found in the snails Radix auricularia and Boreoelona ussuriensis. Sexually mature flukes were obtained by experimentally infecting a duckling and a few chickens, respectively, with metacercariae from the found cercariae. Based on a combination of morphological and molecular (nuclear and mitochondrial markers) evidence, the trematodes grown in the duckling were identified as Notocotylus ikutai. The adult flukes obtained from the infected chickens were assigned to trematodes previously grouped into the genus Catatropis on the basis of morphological characteristics, including the structure of tegumental papillae. However, according to molecular data, the found trematodes were differentiated at the generic level from other Notocotylidae. Based on the above evidence, we here erect a genus, Neocatatropis n. g., to accommodate the type species Neocatatropis primorskii n. g. n. sp.

We describe a new species of the genus Platynosomoides Yamaguti, 1971 (Trematoda: Dicrocoeliidae) from the bile ducts of the cricetid Akodon cursor (Winge, 1887) (Rodentia: Sigmodontinae) from Itatiaia National Park (Parque Nacional do Itatiaia, PNI), in the state of Rio de Janeiro, Brazil. The species is characterized by the following diagnostic features: body size; dimensions and relative proportions of the testes in relation to the body length; extracecal and asymmetrical vitelline glands commencing at the level of the acetabulum, the left vitellarium terminating at the mid-region of the second third of the body, and the right one extending to the anterior margin of the posterior third; and the relative size of the suckers, with the ventral sucker being approximately 60% larger than the oral sucker. The morphological characteristics were described with the assistance of optical microscopy images to observe the internal structures, and their external details were provided by scanning electron microscopy (SEM). Additionally, molecular phylogenetic analyses based on the 18S rRNA gene were conducted to assess the phylogenetic placement of the genus within Dicrocoeliidae. These analyses accompany the description of Platynosomoides macrotestis sp. nov. and contribute to a better understanding of trematode diversity. Furthermore, this study highlights the importance of parasitological research in conserving helminth biodiversity. Its occurrence in conservation areas, such as the PNI, supports the maintenance of unique ecological interactions and species conservation.