Preserving viable infective stages of chicken ascarids under laboratory conditions facilitates the maintenance of characterized nematode strains for research purposes. We investigated the survivability of Ascaridia galli eggs exposed to low temperatures and the cryoprotectant dimethyl sulfoxide (DMSO). Two egg developmental stages (unembryonated or fully embryonated) were stored at 4°C, –20°, or –80°C in sterile water or with 5% and 10% DMSO for 1, 2, 4, or 8 weeks. Egg survival was assessed by morphology following post-storage incubation in 0.1 N H2SO4 at 26°C for unembryonated eggs or with a viability dye exclusion test of hatched larvae for the embryonated eggs. The results revealed that neither DMSO nor the hardy chitinous eggshell protected eggs from freezing damage, and not a single egg survived even for 1 week of storage at –20° or –80°C. DMSO at 10% significantly reduced (P < 0.0001) overall egg survival and embryonation capacity with increasing storage time at 4°C compared to water alone. For both egg developmental stages, egg survival was maintained in 5% DMSO at a rate similar to that in water alone. Unembryonated A. galli eggs survived refrigeration better than embryonated eggs with larval viability declining linearly at almost a double rate in the latter (9.75%/week) compared to the former (5.64 %/week). We conclude that DMSO is unlikely to provide cryoprotection for A. galli eggs and also causes concentration-dependent toxicity with increasing exposure time. Furthermore, survival during refrigeration is better for unembryonated than embryonated eggs.

China accounts for over 90% of global alveolar echinococcosis (AE) cases caused primarily by Echinococcus multilocularis. If left untreated, AE can have a 10-year mortality rate of 94%. Understanding its epidemiological patterns is essential for targeted control strategies. Surveillance data from 2006 to 2020 were obtained from the Public Health Scientific Data Center, and spatial and temporal trends were analyzed using spatial autocorrelation, hot spot analysis, and centroid migration techniques. A total of 51,403 echinococcosis cases were reported from 2006 to 2020, with an average annual incidence of 0.25 per 100,000. Most cases (71.33%) occurred in individuals aged 20–60 years. High-incidence areas centred in western/northwestern provinces, including Qinghai, Xinjiang, Xizang, Gansu, and Ningxia. Incidence and cases increased until 2017, then declined steadily. Spatial autocorrelation revealed persistent High-High clusters in Gansu and Ningxia (2008–2018) and Xizang (2010–2020), while Low-Low clusters persisted in central/eastern China. Hotspot analysis confirmed sustained high-risk zones in western/northwestern regions. Trend surface and centroid migration showed a southward disease shift within Qinghai. Echinococcosis remains endemic in western/northwestern China, with a trend of southward expansion. Strengthened, tailored interventions are urgently needed, particularly in high-burden areas like Xizang and Qinghai.

Based on morphological and molecular data, we describe a new species of Diaphorocleidus parasitizing the nasal cavities of Tetragonopterus argenteus from the Lima Campos weir, municipality of Icó, state of Ceará, Brazil. Diaphorocleidus radius n. sp. resembles other congeners in the morphology of the accessory piece, all by having a bifurcated accessory piece (pincer-shaped), composed of two subunits articulated. However, the new species can be easily distinguished from all congeners by the morphology of the sclerotized structures of the haptor (ventral anchor with well-developed superficial root, ornamented deep root, recurved blade, elongated and lightning-shaped tip; and ventral bar robust, plate-shaped, truncated in lateral ends). Phylogenetic analyses of LSU rDNA and COI mtDNA sequences, conducted using Bayesian Inference and Maximum Likelihood, placed Diaphorocleidus radius n. sp. within Diaphorocleidus, grouping it with species parasitizing acestrorhamphid hosts. Genetic distances between Diaphorocleidus radius n. sp. and other congeneric species such as D. armillatus and D. forficata showed clear differentiation. Both molecular markers support the distinctiveness of Diaphorocleidus radius n. sp., consistent with its recognition as a new taxon.

This study examined the metacercariae of trematodes in cnidarian jellyfish around Japan to demonstrate the importance of the jellyfish as the second intermediate or paratenic hosts. Trematodes were sampled from cnidarian jellyfish in seven coastal regions of Japan between 2024 and 2025. Trematodes (adults and metacercariae) were also obtained from marine fish and arrow worms and included for data comparisons. DNA barcoding was used for the species identification of metacercariae in the jellyfish and for elucidating their partial life cycles. Eight cnidarian species (245 individuals) were sampled, with metacercarial infection detected in seven host species. Based on morphological and molecular analyses, the metacercariae were classified into nine species belonging to three families, Accacoeliidae, Hemiuridae, and Lepocreadiidae. Six of these species were identified as the same species of adults isolated from fish hosts around Japan, although species names of two of the six remained unclear. The remaining three trematode species were assumed to belong to Lepocreadiidae, a major group of fish trematodes. These findings indicate that cnidarian jellyfish are important intermediate or paratenic hosts of fish trematodes in Japanese waters, as has been reported in other areas in previous studies. Moreover, a metacercaria occasionally detected in an arrow worm was identified as the same species as those in jellyfish, suggesting predator–prey relationships between these hosts. The study also synonymised Tetrochetus hamadai Fukui and Ogata, 1935, T. aluterae (Hanson, 1955), and T. mitenevi Zubchenko, 1978, with T. coryphaenae Yamaguti, 1934, based on molecular and morphological data.

Avian schistosomatids are blood flukes parasitizing a wide spectrum of aquatic birds. However, its research in the Neotropics is ongoing with several putative new taxa pending description. Although waterfowl represent the most important avian hosts for these flukes, only a small proportion of these birds have been assessed for schistosomatids. This study aimed to describe avian schistosomatids from two native ducks from the Southern Cone of South America. A total of 24 Chiloe wigeon (Mareca sibilatrix) and three Cinnamon teals (Spatula cyanoptera) from different localities in Chile and Argentina were dissected to retrieve schistosomatids. The retrieved worms were described through an integrative approach considering morphology (staining and SEM) and molecular tools (PCR: COI, 28S rRNA genes). The new schistosomatid: Trichobilharzia kulfu sp. nov. was recovered from the viscera of Chiloe wigeon. It was closely related to other undescribed Trichobilharzia taxa from the United States, also from Mareca ducks. The new species was morphologically and molecularly different from other Trichobilharzia species, and it was included in the clade Q. In addition, SEM imaging proved to be an important tool to describe unnoticed traits on the tegument of worms. This new species represents the second Trichobilharzia taxon from the Neotropics described through an integrative approach. Furthermore, the Cinnamon teals harboured Trichobilharzia querquedulae. Considering there are several avian schistosomatids described only through morphological or molecular tools, there is a clear need to include a comprehensive approach in the description of avian schistosomatids, considering the remarkable richness of schistosomatids in Neotropics.

The genus Alloophistolecithum was recently created and comprises species that were previously included in the genus Lecithaster. The two genera form the subfamily Lecithasterinae. The genera includes species that predominantly parasitize marine fish, and occasionally those inhabiting fresh or brackish water. This study describes a new species of Alloophistolecithum, which is a parasite of the Argentinian silverside (Odontesthes bonariensis), a fish species that inhabits brackish waters. Alloophistolecithum magaliae n. sp. is characterized by smooth, unnotched testes; a uterus extending to the posterior end of the body; and short caeca that do not reach the anterior edge of the vitellary. As genetic analyses are currently limited to a few species within the genus, it is premature to establish clear relationships between them. The Argentinian silverside is considered to be of great economic importance, having spread not only within Argentina but also to other countries for commercial exploitation. The anthropogenic spread of silversides outside their natural range could pose a risk of biological invasion, so studying their parasitological fauna is important.

Trichostrongylus spp. are globally distributed gastrointestinal nematodes that affect ruminants and humans, posing significant veterinary and public health challenges. Despite their zoonotic potential, the temporal dynamics of Trichostrongylus infection remain poorly understood globally. This study aimed to estimate long-term trends in Trichostrongylus prevalence in humans, ovines, and bovines using time series modelling. A systematic review identified 240 eligible studies with annual prevalence data across 60 countries. Following Kalman smoothing, annual prevalence time series were constructed for each host species covering 1947–2024 for humans, 1966–2024 for ovines, and 1962–2024 for bovines. ARIMA models were fitted separately: ARIMA(0,1,1) for humans, ARIMA(3,0,0) for ovines, and ARIMA(0,1,1) for bovines. Model selection was based on Stationary R2, RMSE, MAPE, and the Ljung-Box Q test for residual independence. Forecast 95% confidence intervals were reported to convey uncertainty in the projected trends. All three models demonstrated good in-sample fit and adequate residual diagnostics. Infection rates in humans and bovines are projected to decline, from 4.64% to 3.73% in humans and from 20.11% to 11.76% in bovines by 2034. In contrast, the ovine model forecasts an increase in infection rates, from 6.50% to 15.56%. This increase in ovines may reflect greater pasture exposure and environmental persistence of infective larvae, while improvements in hygiene and livestock management likely contribute to the declining trends observed in humans and bovines. The rising infection rate in ovines, coupled with sustained zoonotic risk, underscores the need for integrated One Health surveillance and control efforts.

Amerotyphlops brongersmianus (Vanzolini, 1976) is the only representative of its family in Argentina, and to date, there have been no records of its parasites. Between 2013 and 2018, 46 specimens of A. brongersmianus were collected in Corrientes province and investigated for helminths. Eighty-three specimens of Serpentirhabdias aff. vellardi were collected from the lungs of nineteen hosts. Sixty-nine percent of the nematodes were collected from the vascular lung mostly, with a prevalence of 41.3% and a mean intensity of 3.74 worms. Adult snakes had higher prevalence and mean abundance than juveniles; the mean intensity was similar between sexes and sexual maturity groups. The association between sexual maturity and the presence of lungworms was statistically significant. Lungworm abundance, weight, and length of adult snakes showed weak to strong positive correlations, with stronger correlations in males; however, these were not statistically significant. Nematodes followed a negative binomial distribution. Seasonal differences in parasitological descriptors and mean body length of lungworms were not statistically significant. Nonetheless, a significant negative correlation was observed between lungworm abundance and body length in spring, suggesting a clustering effect. Our results are discussed based on host phenology, ecology, biology, and anatomy. The life cycles of lungworms, the abundance of potential transport hosts, as well as abiotic factors (rainfall and temperature), are also considered. This is the first report of lungworms in A. brongersmianus throughout its range, the second global report of helminths in a Typhlopidae species in the 21st century, and the first in South America and Argentina, providing ecological data.

TEM analyses of germinal elements in miracidia and 6-day-old mother sporocysts of Echinostoma caproni were performed. Germinal elements in miracidia are represented by undifferentiated cells and germinal cells. They are localised in the posterior half of the body and form the primordium of the germinal mass, which plays the role of the gonad. In mother sporocysts the germinal mass is located caudally and plays the dual role of the gonad and the uterus. In addition to the undifferentiated cells and germinal cells, it contains embryos, which develop there up to the stage of germinal balls and then move into the sporocyst’s schizocoel, which plays the role of the brood chamber. New germinal cells are formed only by division of undifferentiated cells. No differences between undifferentiated and germinal cells in miracidia and those in sporocysts were found.

The white mullet, Mugil curema (Mugilidae), is a catadromous euryhaline fish with an omnivorous diet, and is distributed mainly along the Pacific and Atlantic coasts of the Americas. Mullets represent an important economic resource for the artisanal fisheries in Mexico. In this study, 73 individuals of M. curema were analysed; specimens were sampled in 4 coastal lagoons of the Yucatán Peninsula, Mexico, between 2022 and 2024. Parasite identification was accomplished by using DNA sequences. Nineteen parasite taxa were found, including 1 monopisthocotylan, 1 copepod, 1 acanthocephalan, 1 nematode, and 15 trematodes. Specimens were sequenced for a nuclear or mitochondrial molecular marker. Ten taxa are reported for the first time in this host species, including the adult trematodes Saccocoelioides olmecae; Schikhobalotrema sp. 1 and sp. 2, Hemiuridae gen. sp., the larval trematodes Mesostephanus microbursa, M. cubaensis, Cardiocephaloides medioconiger, Saccularina sp., Bucephalus sp., as well as the larval nematode Contracaecum fagerholmi. Of the 21 metazoan parasites recorded, 58% were adults and 42% were larval stages. The checklist of the metazoan parasites of M. curema was updated. Our study contributes to the understanding of the parasite diversity of an economically important fish species with a wide distribution range and corroborates the usefulness of combining morphological and molecular data for species identification and for linking larval forms with adults to complete parasite life cycles. Our results will be useful in further studies of parasites as bioindicators of ecosystem health, and studies of the role of parasites in food webs in coastal lagoons.

An adult female great curassow (Crax rubra) and an adult female crested guan (Penelope purpurascens) were examined post-mortem and found to harbour trematode flukes in their pulmonary air sacs and coelom, with severe pathological changes. Seven trematode specimens (four from C. rubra and three from P. purpurascens) were stained with hydrochloric acid–carmine for optical microscopy, while four specimens (two from each bird species) were submitted to molecular analysis. Morphological and molecular analyses identified the specimens as Circumvitellatrema momota. Phylogenetic analysis showed that C. momota from different geographical origins constitutes a single species within the subfamily Cyclocoelinae and is clearly distinct from other cyclocoelid genera. This is the first documented case of C. momota infecting members of the Cracidae family. These findings highlight the importance of monitoring parasitic infections in captive and free-ranging cracids under conservation programmes.

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.

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.

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.

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.

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.

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.

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.

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.

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.