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.

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.

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.

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.

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.

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.

The diversity of Rhabdias includes 101 species, 71 of which parasitize the lungs of anurans, caudates, gymnophionans, and some occur in reptiles worldwide. Currently, 26 species are found in the Neotropical region, and in Brazil, there are 16 nominal species, a relatively low number considering the high diversity of potential hosts. Here, we describe a new species of Rhabdias found in Physalaemus albonotatus, with morphological and molecular data, as well as phylogenetic analyses using sequences of the mitochondrial gene Cytochrome Oxidase Subunit I (COI). Rhabdias taquariensis n. sp. differs from other known species by a set of morphometric traits and by presenting a well-defined internal shape of the cephalic dilation. Molecular analyses revealed that R. taquariensis n. sp. exhibits a significant divergence of 13.6% in COI compared to the Rhabdias cf. stenocephala species complex. Additionally, phylogenetic reconstructions indicate that the new species represents a distinct lineage, external to a clade formed by species such as Rhabdias fuelleborni, Rhabdias cf. stenocephala, and Rhabdias waiapi. Rhabdias taquariensis n. sp. is the 27th species described in the Neotropical region and the 16th in Brazil, the first description of a species of the genus Rhabdias for Physalaemus albonotatus, and one of the few Rhabdias species described for the Cerrado biome.

Acanthobothrium represents the most species-rich genus of onchoproteocephalidean cestodes, with adults parasitizing the spiral valves of elasmobranch fishes. Between October 2023 and August 2025, Acanthobothrium minus, previously reported from the Algerian coast in Raja asterias (Mediterranean starry ray), was collected from the spiral valve of Raja asterias, and the rough ray, Raja radula. This parasite is characterized by its small body size and reduced number of proglottids. In this study, we examine its host specificity and provide a redescription of A. minus from the type locality and host, and an additional host (R. radula) using light microscopy and molecular approaches. Furthermore, we present, for the first time, molecular and phylogenetic data based on 28S rDNA sequences for this species, along with a detailed morphometric comparison to other CategoryII Acanthobothrium species infecting Rajidae from the Mediterranean. Our phylogenetic results show all Acanthobothrium species 28S sequences from the Mediterannean grouping in the same clade and suggest close affinity with Acanthobothrium coronatum (Category 4). These results support that these taxonomic categories are a useful guide for morphological comparisons but are not correlated with true phylogenetic relationships. Furthermore, the regional grouping of these sequences from relatively distantly related definitive hosts (the shark Scyliorhinus stellaris L. and the skates R. asterias and R. radula) supports evolution of this elasmobranch-Acanthobothrium association in the Mediterranean through host switching due to shared ecological features of the hosts followed by speciation by isolation. However, additional support for this hypothesis would require more in-depth taxonomic representation of available sequence data.

Many parasitic nematodes exhibit a range of behavioural responses to host-associated stimuli, especially chemicals. The infective juveniles (IJs) of specialized insect-infecting nematodes, i.e., entomopathogenic nematodes (EPNs), can show directed movement (taxis) or other behaviours in response to odorants. However, relatively little is known in terms of IJ responses in the context of increases in non-directed movement (kinesis) resulting from physical contact with host chemicals, or the effects of insect semiochemicals on EPN behaviours. We individually exposed IJs of the EPN Steinernema carpocapsae to solutions representing five different treatments, including those containing the macerated tissues of a suitable insect host (greater wax moth larvae – waxworms) or a semiochemical (1-pentadecene) secreted by various insects. We conducted behavioural observations at six time points over an 8-h period, measuring the total number of movements by each IJ (orthokinesis), along with the occurrence of side-to-side movements (klinokinesis) or head-waving. We found that IJs in the waxworm or 1-pentadecene solutions showed high levels of overall movement, but waxworm-exposed IJs also exhibited the most sinusoidal movement, whereas IJs exposed to 1-pentadecene exhibited far more head-waving than nematodes in the other treatments. These results indicate that S. carpocapsae shows behavioural responses through kinesis when exposed to host chemical cues in an aqueous medium. As our study is only the second report of EPNs responding to an insect semiochemical, this is a promising area for future studies to better understand host-finding strategies by these nematodes, with possible applications for their use in insect biocontrol.

This study provides the description of a new species of Anisakidae, Contracaecum cocoi sp. nov., as well as the record of Contracaecum jorgei, both species parasitizing the Cocoi heron Ardea cocoi (Ardeidae) in a locality from the Buenos Aires Province, Argentina. An integrative taxonomic approach was used, involving phylogenetic analyses and the examination of diagnostic morphological features in the studied specimens. Among other features, the new species can be morphologically distinguished by the papillae arrangement on the male tail: while C. jorgei exhibits a simple morphotype A, C. cocoi sp. nov. presents an intermediate morphotype B. Mainly, the possession of three adcloacal papillae pairs is a diagnostic feature separating this new species from the rest of the Contracaecum species. The cox2 mtDNA isolates exhibited C. cocoi sp. nov. as a single node and grouped close to the clade formed by both species Contracaecum micropapillatum and C. bancrofti. The other cox2 mtDNA sequences showed a great concordance with C. jorgei. The K2P distances calculated for the cox2 mtDNA isolates of C. cocoi sp. nov. displayed a distance of 0.12 with C. bancrofti, 0.13 with C. micropapillatum, and 0.16 with C. jorgei. Contracaecum cocoi sp. nov. is proposed as a new taxon clearly supported by both phylogenetic analysis and distinctive morphological features that distinguish it from its congeners. The occurrence of C. cocoi sp. nov. together with C. jorgei in sympatric and syntopic conditions suggests that ecological or reproductive isolating mechanisms may be acting to maintain distinct lineages in shared environments. New records, particularly those involving intermediate and definitive hosts, will contribute to elucidating the distribution of these parasites in the Americas and potentially lead to the discovery of new species.

Human strongyloidiasis, caused by Strongyloides stercoralis, is a neglected disease of high worldwide prevalence, with considerable potential for severe, fatal outcomes in complicated cases. Studies using the rodent parasite Strongyloides venezuelensis as a model have provided valuable insights into strongyloidiasis, yet efficient, standardised methods for isolating large quantities of viable parasite eggs for biomedical research remain scarce. This study revisits and modernises the classical flotation principle, presenting a saturated-solution centrifugation protocol for egg recovery from infected clawed jirds (Meriones unguiculatus). Saturated NaCl outperformed sucrose, primarily due to enhanced egg visualisation and reduced microbial contamination, achieving mean recovery of 84.8 ± 6.7% (peaks to 94%). Key variables – including faecal suspension volume, solution concentration, reprocessing, and the NaCl gradient – were systematically optimised to maximise recovery and viability. The resulting protocol is cost-effective, rapid, and practical, enabling scalable collection of viable S. venezuelensis eggs (and likely other nematodes) for different applications, including hatching studies, larval development, microenvironmental assays, and drug screening. By integrating classical diagnostics with parametric optimisation, this study exemplifies how methodological advances preserve and renew foundational knowledge, underscoring its epistemological value in experimental parasitology.

The alternation between wet and dry seasons in tropical regions can dramatically affect parasite infection dynamics by influencing larval survival, intermediate-host density, definitive-host foraging behaviour, and host immune function. Freshwater chelonians are excellent models for studying parasite-host ecology. Their longevity, site fidelity, and dietary breadth make them valuable sentinel species for aquatic ecosystem health. Here, we identified the gastrointestinal helminth fauna of scorpion mud turtle (Kinosternon scorpioides) from Marajó Island and evaluated seasonal effects on parasite community dynamics. We observed a 71% reduction in parasite load during the dry season and substantial compositional shifts, in addition to species-specific responses: Spiroxys figueiredoi exclusively during floods and Nematophila grandis peaking during dry periods. Parasite species with flexible transmission pathways may thrive while specialists decline. Kinosternon scorpioides and its parasites function as sentinels, and monitoring helminth community composition could more accurately track ecosystem health than measuring host abundance alone.

Marsupials have been the subject of experimental and natural parasitological studies on helminths in the Americas. Brazil has a significant proportion of the American marsupial fauna, with approximately 15 genera and 69 species out of 95 extant. Helminths have been reported for approximately one-third of the Brazilian marsupial species. Consequently, an update of this information is necessary to ensure the correct identification of the species. This work represents the first comprehensive review of the helminths of the Brazilian marsupials, including taxonomic information on both parasites and hosts. The data were extracted and compiled from references published from 1819 to 2023 and organised according to the classification of the helminths by the host name of the original description, followed by the updated host species nomenclature, geographical distribution, site of infection, and references. In total, 1,047 records of helminths parasitising 22 marsupial species in Brazil were compiled. The list included 93 identified species, including five of the phylum Acanthocephala, 58 of the phylum Nematoda, and 30 of the phylum Platyhelminthes. In addition, 51 other morphospecies were reported. This work may serve as a reference for future studies.

Metacercariae of Diplostomum spp. are globally distributed pathogens that infect the eyes and brains of fish and lampreys, including populations in northern latitudes. This study investigated the species diversity and distribution of Diplostomum in juvenile Atlantic salmon Salmo salar and brown trout Salmo trutta from 11 rivers in northwestern Russia. Phylogenetic analyses revealed two diplostomid species: ‘D. mergi’ Lineage 3 and D. numericum. It is the first record of these species in the Russian part of the Arctic. These species, previously recorded in Western/Central Europe and Russian Karelia, likely spread via major migratory flyways of their avian definitive hosts. The species composition of Diplostomum metacercariae in riverine salmonids of the studied region was notably poorer than in lacustrine salmonids from other Arctic localities. The haplotype distributions of recorded Diplostomum species showed no spatial structuring, consistent with broad-scale dispersal processes.

This study provides the first integrative analysis of Megacoelium spinicavum Thatcher & Varella, 1981 (Digenea: Haploporidae) from the Amazon sailfin catfish Pterygoplichthys pardalis Castelnau, 1855 (Siluriformes: Loricariidae) in the Peruvian Amazon. A detailed morphological description is presented, including the first scanning electron microscopy (SEM) images of tegumental structures, which revealed two distinct types of tegumental spines: (1) small, button-like spines and (2) sharply pointed spines. Partial sequences of the 28S rDNA and mitochondrial cox1 genes were generated and analysed to investigate the phylogenetic position of Megacoelium Szidat, 1954, within the Haploporidae Nicoll, 1914. Phylogenetic analyses placed M. spinicavum within the ‘robust species’ clade of Saccocoelioides Szidat, 1954, clustering with S. bacilliformis Szidat, 1973, although with weak support. These results provide additional evidence that Saccocoelioides is not monophyletic and support restricting the genus to the ‘minute species’ clade containing the type species. The ‘robust species’ clade appears to comprise at least three divergent lineages, potentially representing distinct genera, one of which includes M. spinicavum. The absence of molecular data for M. plecostomi Szidat, 1954, the type species of Megacoelium, continues to obscure its phylogenetic placement. We highlight the need for comprehensive morphological and multilocus molecular analyses, including SEM, to clarify the taxonomic status of Megacoelium and to resolve the evolutionary relationships of chalcinotrematine digeneans in Neotropical fishes.