Secondary structures of the internal transcribed spacer 2 (ITS2) region of ribosomal RNA (rRNA) were reconstructed for 46 species belonging to 12 genera of the family Allocreadiidae. Most structures exhibited the classical four-domain conformation typical of ITS2, with some notable variants. The C-domains of Bunodera acerinae and Allocreadium sp. 2 were divided into three branches. Structures of Creptotrema funduli and Pseudoparacreptotrema macroacetabulata showed unique conformations, with unusually variable A and B domains. Ten-nucleotide sequence variation at the 5′ end of the ITS2 region correlates with phylogenetic relationships within the family. A dichotomous key based on ITS2 secondary-structure features is proposed, providing a novel, annotation-independent tool for species identification. Phylogenetic analysis based on ITS2 data is also presented, but we acknowledge the limitations of this marker for resolving deep relationships and interpret the resulting topology as a hypothesis complementary to 28S-based phylogenies. The presence of regulatory motifs and palindromic elements suggests that ITS2 functions as a primary hub-DNA product that accumulates regulatory information, potentially influencing RNA folding, stability, and transcription efficiency. ITS2 secondary structure analysis, combined with the proposed key, provides a powerful approach for understanding the evolution and systematics of this complex trematode family.

The serological diagnosis of human cestodiases, particularly cystic echinococcosis (CE) and neurocysticercosis (NCC), is frequently constrained by cross-reactivity associated with crude parasite extracts, limiting its utility in differential diagnosis. This review evaluates the potential of recombinant antigen-based multiplex serology to improve the differentiation between CE and NCC. We examine key diagnostic targets, including the chimeric antigens DIPOL and 2B2t for CE, and T24H together with lentil lectin-adherent glycoproteins (LLGP) for NCC. We further discuss bead-based multiplex platforms that allow the simultaneous detection of antibodies against multiple antigens from a single, small-volume sample. Current evidence indicates that these approaches may reduce cross-reactivity and provide a more nuanced characterisation of pathogen-specific immune responses. Multiplex immunoprofiling represents a promising step toward more integrated serological strategies for the differential diagnosis of human cestodiases. However, further standardisation and validation across diverse epidemiological settings are required prior to routine clinical implementation.

Cysticercosis, a zoonotic infection caused by the larval stage of Taenia solium, poses significant public health challenges in endemic regions. This community-based case–control study examined the seroprevalence, risk factors, and potential association between human cysticercosis and epilepsy in Southern Nigeria. Between September and December 2023, a door-to-door survey screened 23,027 residents across five communities using a validated 10-item questionnaire for epileptic seizures. Confirmed cases and age-matched community controls were tested for T. solium antibodies using enzyme-linked immunoelectrotransfer blot (EITB) and for taeniasis by stool microscopy. Of 79 participants tested serologically, the overall seroprevalence of cysticercosis was 12.7% (10/79), with no statistically significant difference between persons with epilepsy (PWE) (11.9%) and controls (13.5%) (p > 0.05). Taenia spp. eggs were detected by stool microscopy in 6.6% of PWE. Multivariable logistic regression identified increasing age (adjusted OR = 0.95; 95% CI: 0.92–0.98; p = 0.01) and consumption of frozen meat (adjusted OR = 0.23; 95% CI: 0.06–0.98; p = 0.04) as factors independently associated with lower odds of cysticercosis seropositivity. One case of neurocysticercosis (NCC) (2.4%) was confirmed among PWE. These findings suggest that, while T. solium transmission occurs in Southern Nigeria, cysticercosis is unlikely to be a principal aetiological driver of epilepsy in the studied communities. Strengthened food hygiene practices and larger population-based investigations are warranted to better inform public health control strategies.

Amphibian helminth diversity remains poorly documented in semiarid environments, despite its relevance for understanding host–parasite interactions and biogeographical patterns. We investigated the helminth community of the hylid frog Scinax x-signatus from a Caatinga remnant in Petrolina (Pernambuco, Brazil) and reviewed the current state of knowledge on helminth infecting South American Scinax species. Twenty-five S. x-signatus (11 adult females, 9 adult males and 5 juveniles) were examined; of these, 13 specimens (52%) harboured at least 1 helminth taxon, with infracommunity richness ranging from 1 to 7 taxa. We identified four nematodes (Oswaldocruzia sp., Oxyascaris caudacutus, Oxysomatium sp., Rhabdias sp.), two digeneans (adults of Catadiscus sp. and metacercariae of Neodiplostomum sp., and cystacanths of an acanthocephalan (Centrorhynchus sp.). Oxyascaris caudacutus was the most prevalent taxon (20%) and exhibited the highest mean intensity (4.0 ± 2.77). Four taxa (Oswaldocruzia sp., O. caudacutus, Oxysomatium sp. and Catadiscus sp.) represent new host records for S. x-signatus. Our literature review identified 45 publications from 1940 to 2026 and showed that helminth have been recorded for only 13 South American Scinax species, comprising 78 taxa in total (46 Nematoda, 20 Trematoda, 8 Acanthocephala and 4 Cestoda). Records are strongly geographically biased, being restricted to five countries (Brazil, Argentina, Peru, Paraguay, and Ecuador), and most taxa remain identified only to genus or higher taxonomic levels. Our results expand knowledge of Caatinga amphibian parasites and reinforce the need for integrative surveys to better estimate helminth diversity across the South American continent.

Geographic distance is often recognized as a leading factor structuring the diversity of parasite communities. However, specific ecological and biogeographic mechanisms underlying the influence of this factor are not always evident. We used the material on the helminths of Fulica atra Linnaeus, 1758 (Rallidae) from seven areas in the Palaearctic to study geographic differentiation of the parasite communities at the level of both component communities and infracommunities. The analysis of spatial patterns of the parasite communities included (i) a reconnaissance study exploring the directions of variability of the communities using principal component analysis (PCA), and (ii) a careful disentanglement of the relationships identified in the reconnaissance study using metric scaling in Euclidean space. The component communities showed a clearer differentiation associated with geographic factors as compared to the infracommunities. The differences in the species composition of the parasite component communities of F. atra. increased consistently with increasing longitudinal distance between the localities, while the differences in prevalence increased with increasing latitudinal distance. The longitudinal trend of similarity decay of species composition of the component communities is probably determined by the directions of the seasonal migrations of F. atra., which promote or prevent the exchange of parasite species between geographically isolated areas. The latitudinal gradient in the variability of the component communities in terms of prevalence may be associated with the latitudinal patterns in the temperature regime of the water bodies and their impact on the species composition and biomass of the food objects of F. atra.

Female nematodes were collected from the intestines of a road-killed Yucatan Neotropical rattlesnake, Crotalus tzabcan, in Yucatan, Mexico. Morphometric analysis of the nematode specimens allowed their identification to the genus Kalicephalus. However, the absence of male specimens prevented species-level identification. Notably, second- and third-stage larvae were observed in the reproductive tract of some Kalicephalus females. Additionally, the internal transcribed spacer (ITS) region, the cytochrome c oxidase subunit 1 (COI) gene, and the 28S rRNA gene (28S) were amplified and sequenced. Pairwise genetic distances between the Kalicephalus sp. sequences from C. tzabcan and those of other Kalicephalus species were calculated for the three molecular markers. In the phylogenetic tree (ITS1) of Ancylostomatina, the sequences of Kalicephalus sp. were clustered with Kalicephalus viperae from Iran with high support. This study reports, for the first time, the genus Kalicephalus in C. tzabcan, and the presence of larvae in the reproductive tract of Kalicephalus females naturally parasitising a snake.

The genus Contracaecum is an important group of anisakid nematodes containing species of veterinary, medical, and economic importance. However, current genetic sequences and the mitogenomic database for Contracaecum spp. are limited. In the present study, the nuclear 18S, 28S, and ITS regions and the mitochondrial cox1, cox2, and 12S data for C. ovale (Linstow 1907) were sequenced based on the newly collected specimens from Tachybaptus ruficollis (Podicipediformes: Podicipedidae) in China. These sequences exhibited 100% similarity in the 18S and 28S regions and 99.8% similarity in the ITS-1 region (the presence of only a single locus of nucleotide polymorphism), compared with samples of Contracaecum ovale from Podiceps cristatus australis in New Zealand. Molecular analysis of two different individuals of C. ovale, collected from T. ruficollis in China, showed no genetic divergence with respect to the 18S, 28S, ITS, cox1, and 12S regions, but a low level of divergence in the cox2 sequences (0.73%). The complete mitogenome of C. ovale, presented for the first time, is 13,769 bp in length and includes 12 protein-coding genes, 22 tRNA genes, 2 ribosomal RNAs, and 2 non-coding regions. The mitogenome of C. ovale represents the smallest known anisakid mitogenome, and its overall A + T content (71.5%) is the highest level of A + T content of any anisakid. The mitogenomic phylogeny of those Contracaecum spp. whose mitochondrial protein-coding genes (PCGs) have been studied suggests that C. rudolphii and C. ogmorhini are more closely related to each other than either is to C. ovale. The genetic and mitogenomic data presented herein will be helpful for future studies on the population genetics and phylogenetics of Contracaecum spp.

Morphologically similar diplostomid metacercariae were found infecting four species of Pampean rivulid fishes – Austrolebias bellottii, Amatolebias patriciae, Argolebias nigripinnis, and Titanolebias elongatus – from temporary freshwater ponds in the Pampean region of Argentina. Although these larvae occur in different host species and localities, comparative morphological analyses revealed extensive overlap in diagnostic characters. To assess whether this morphological similarity reflected conspecificity, molecular analyses based on partial 28S rDNA and ITS2 rDNA sequences were performed. Phylogenetic reconstructions recovered all metacercariae from rivulid hosts as a single, well-supported lineage, consistent with their assignment to a single lineage Posthodiplostomum species. Genetic distances among ITS2 sequences were zero, indicating complete sequence identity across hosts and localities. Infection parameters varied among host species and populations, with Austrolebias bellottii and Titanolebias elongatus exhibiting the highest values. Differences in infection levels could reflect variation in local environmental conditions, habitat characteristics, and the availability of avian definitive hosts, potentially influencing parasite transmission dynamics. This study provides integrative morphological and molecular evidence consistent with all metacercariae representing a single Posthodiplostomum lineage infecting multiple Pampean rivulid species and contributes to a better understanding of parasite diversity and transmission patterns in South American temporary ponds.

Disease macroecology relies on large, complex datasets to understand the biotic and abiotic factors shaping parasite distributions and emerging infectious disease risk. These datasets span local to global host–parasite interactions and often integrate diverse host or parasite traits across evolutionary histories. Selecting appropriate statistical approaches requires first asking key questions about the study system: How well is the system understood? How important is predictor accuracy? How much bias is present in the data? We outline three broad analytical pathways commonly used in disease macroecology (frequentist models, Bayesian approaches, and machine learning) and link them to typical data contexts, providing R coding examples using current packages. We emphasise that these pathways are intended as flexible guidelines rather than prescriptive frameworks. Although more advanced approaches have grown in popularity over the last three decades, traditional significance tests remain widely used. While these tests remain appropriate for well-controlled or small-scale experimental systems, they are often unsuitable for complex ecological datasets, where violations of assumptions, hierarchical structure, and sampling biases can lead to unstable or difficult-to-reproduce inferences. We advocate for reporting biologically meaningful predictors, effect sizes, measures of uncertainty, and transparent analytical workflows. By explicitly linking common data challenges in disease macroecology to their consequences for model choice and inference, we encourage more reproducible, transparent, and context-appropriate statistical practices for understanding and forecasting parasite distributions and emerging disease risks.

Species of Hexangium (Microscaphidiidae) were collected from 12 species of rabbitfishes (Siganidae) from multiple Indo-West Pacific locations: three on the Great Barrier Reef in Queensland, two in south-east Queensland, Ningaloo Reef in Western Australia, New Caledonia and Japan; no specimens were found from Palau or French Polynesia. Parallel molecular (cox1 mtDNA, ITS2 and 28S rDNA) and morphological analyses, together with consideration of host and geographical distribution, lead us to recognise six species. Specimens from Siganus fuscescens (Houttuyn) from Japan are identified as the type species, H. sigani Goto & Ozaki, 1929, which was originally described from S. fuscescens from off Japan. Hexangium affinum Tubangui & Masiluñgan, 1944, originally described from Siganus javus (Linnaeus) from the Philippines but previously considered a synonym of H. sigani, is reinstated, and H. secundum Annereaux, 1947 is considered its junior synonym. Four new species are described: H. urabeae n. sp., H. kuramochii n. sp., H. robustum n. sp. and H. reimeri n. sp. Based on morphology alone, individual specimens of several combinations of these species are difficult to distinguish. Although none of the combinations of species are entirely mutually cryptic, we consider taxonomy of this genus to be dependent on molecular analysis; morphological distinction of species requires substantial numbers of well-preserved specimens. Most species of Siganus examined harbour two or three species of Hexangium; sometimes one species is dominant, but in several two species were both common. All six Hexangium species recognised here have been found in multiple locations; four species were found at each of two Great Barrier Reef sites.

Understanding how parasite abundance changes over time is inherently challenging, as trematodes, nematodes and cestodes degrade quickly and are poorly preserved. Here, I propose a novel approach for investigating the spatiotemporal dynamics of parasitic nematode infection by exploiting a key component of the snail immune system – the ability to trap and encapsulate these parasites within their shell. By utilising museum and modern collections, I was able to understand how nematode populations fluctuated in two species of snails (Cepaea nemoralis and C. hortensis) from three locations (Point of Ayr in Wales, Formby in England and Strathy beach in Scotland) from 1962 to 2024. I show that in vivo parasite populations collected from Point of Ayr in 1962 were initially low, with 8% of shells infected, but this dramatically increased to 60% in 2016 and fell to 10% in 2024. The number of C. nemoralis shells infected from Formby in 2016 was 18% but increased to 31% in 2024, and 27% of C. hortensis shells from Strathy beach in 2016 were infected by nematodes but plummeted to 3% in 2024. Thus, dramatic spatiotemporal changes in nematode abundance can be seen over several decades. By combining preserved snails in conchology collections with collections of modern specimens, empirical evidence of how parasite numbers change over time can be quantified.

We report new collections of trematodes currently assigned to the Faustulidae Poche, 1926, from fishes of the Pomacanthidae and Ostraciidae in the tropical Indo-West Pacific. Phylogenetic analyses demonstrate that these species, and several other faustulid taxa, form a well-supported clade within the Zoogonidae Odhner, 1902 (Microphalloidea), distant from the Faustulidae sensu stricto (Gymnophalloidea). We recognise the subfamily Antorchiinae Skrjabin & Koval, 1957 within the Zoogonidae for Antorchis Linton, 1911, Neoparantorchis Hafeezullah & Siddiqi, 1971, Parantorchis Yamaguti, 1934, Paradiscogaster Yamaguti, 1934, Discogastroides Strand, 1934, Parayamagutia Machida, 1971 and Trigonocryptus Martin, 1958, and propose four new genera. Scaticola n. g. is proposed for two species of Bacciger Nicoll, 1914 that resolve within the Antorchiinae rather than with Bacciger sensu stricto. Crassitrema n. g. and Findovitellus n. g. are proposed for two species of Paradiscogaster that resolve distant from all other sequenced species of Paradiscogaster. Nasoantorchis n. g. is proposed for Nasoantorchis nasonis (Cribb, Bray, Hall & Cutmore, 2015) n. comb., previously considered a member of Antorchis. From pomacanthids, we describe two new species of Parantorchis, Parantorchis vaili n. sp. and Parantorchis parviovatus n. sp., and two new species of Paradiscogaster, Paradiscogaster hoggettae n. sp. and Paradiscogaster ningalooensis n. sp. We also report Neoparantorchis pomacanthi (Hafeezullah & Siddiqi, 1970) Hafeezullah & Siddiqi, 1971 and Paradiscogaster machidai Cribb, Anderson & Bray, 1999. From ostraciids, we report Discogastroides ostracii (Yamaguti, 1934) Skrjabin & Koval, 1957, Discogastroides macrostomus Shimazu & Kamegai, 1990, and Parayamagutia ostracionis Machida, 1971.

Ecological processes that shape animal assemblages act at multiple levels. Limited information is available on the factors that drive spatial variation in parasite communities, particularly in nematodes. This study aimed to reveal the role of host and environment as determinants of nematode species compositional similarity among three rodent taxa (Rhabdomys spp., Micaelamys namaquensis, and Otomys unisulcatus) that occur sympatrically in the Fynbos and Succulent Karoo biomes of the Western Cape Province of South Africa. In total, eight monoxenous and three heteroxenous nematode species were recorded. Seven species occurred in Rhabdomys spp., six in M. namaquensis, and five in O. unisulcatus. Nematode communities were more similar between Rhabdomys and Otomys, which also share comparable microhabitats. Nematodirus sp. and Neoheligmonella capensis, both with free-living larval stages, contributed strongly to between-host differences that were also correlated with low-lying habitat use. However, part of the between-host differences in species assemblages reflects host-restricted Syphacia spp. The influence of environmental factors on the composition of nematode infracommunities was also contingent on host life history. Overall, host diet, microhabitat use, as well as social and spatial behaviour appeared to exert a strong influence on the composition of nematode infracommunities. Results suggest that microhabitat use plays an important role in nematode community assembly, although direct environmental covariates were not formally analysed. Since between-host dissimilarities were influenced by host-restricted nematode species, habitat-driven patterns should be interpreted after accounting for host identity. The data generated here contribute to a broader understanding of the ecological niches preferred by parasitic nematodes of rodents.

The Allocreadiidae comprise a diverse group of digeneans infecting freshwater fishes worldwide, with South America harbouring a particularly rich fauna. Within this family, Creptotrematina includes five valid species parasitizing primarily characid fishes, most of which have been recorded from the La Plata Basin. Despite the large geographic extent and hydrological complexity of this basin, the genetic structure and evolutionary relationships of Creptotrematina species across its sub-basins remain poorly understood. The inclusion of a new ITS sequence of Martorellia liciae recovered the same topology observed in the 28S phylogeny, supporting Martorellia as the sister genus of Creptotrematina. In the present study, specimens of Creptotrematina spp. collected in the Paraná and Iguazú rivers were analysed using partial sequences of 28S rDNA, ITS, and mitochondrial COI genes. Phylogenetic analyses based on individual markers recovered the new material within Creptotrematina batalhensis with strong support. Genetic divergence between Argentine and Brazilian populations of C. batalhensis was extremely low or absent across all markers, despite the large geographic distances and differences in hosts infected. These results indicate basin-wide genealogical cohesion and the absence of detectable phylogeographic structure. The observed pattern suggests that hydrographic subdivision within the La Plata Basin has not acted as an effective evolutionary barrier for this species. Instead, the strong association of Creptotrematina spp. with closely related characid hosts supports the hypothesis that host phylogeny and host-mediated dispersal may play a central role in shaping parasite diversification, with hydrological dynamics modulating connectivity rather than driving lineage fragmentation.

A new entomopathogenic nematode, Steinernema hattingi n. sp., was isolated during a survey in Mpumalanga Province of South Africa. Morphological and morphometric traits place the species in the glaseri-group, characterised by large infective juveniles (IJs) with average body length exceeding 1000 μm. The IJs of S. hattingi n. sp. have a mean body length of 1059 μm, lateral fields composed of eight equally spaced ridges (nine incisures) at mid-body (formula 2, 6, 8, 4, 2), a relatively short tail (c ratio 16 on average) with a hyaline region occupying approximately 45% of its length, and are relatively slender (a ratio 33 on average). Male spicules are curved, brown, with a pointed tip and an elongate manubrium (length/width ratio 1.8:1); male tails are non-mucronate or occasionally with a short papilla-like mucron in second-generation males. First-generation females have a moderately protruding, slightly asymmetrical vulva without postanal swelling, whereas second-generation females display a protruding, asymmetrical vulva and a slightly developed postanal swelling. The species is further characterised by sequences of the internal transcribed spacer (ITS) and partial 28S rDNA (D2–D3) regions. Phylogenetic analyses place S. hattingi n. sp. within the Khoisanae clade of the glaseri-group.

We report trematodes conforming to the generic concept of Parachrisomon Madhavi, 2008, infecting multiple species of goatfishes (Mullidae) from Moreton Bay (south-eastern Queensland) and off Lizard Island (northern Great Barrier Reef) on the eastern coast of Australia, and from Ningaloo Reef on the western coast. Initial morphological analyses suggested the possible presence of multiple species; however, no morphological distinctions proved consistent. Molecular analyses demonstrate a distinction between western and eastern Australian samples, especially in mt cox1 sequence data, but the differences are interpreted as intraspecific geographical variation. Specimens from all localities share a bipartite terminal organ with an irregularly shaped and lobed anterior part; the other eight species of Parachrisomon are reported with unspecialised, bipartite terminal organs. We recognise the specimens as representing a new species, Parachrisomon debonoae n. sp., that exhibits significant intraspecific morphological variation, especially in body size, pharynx size, and shape and size of the ovary and testis. Additionally, we report novel molecular data for Parachrisomon delicatus (Manter & Pritchard, 1961) Madhavi, 2008.

Preschool children in the Kingdom of Eswatini are excluded from the national school-based deworming programme and had never been surveyed for parasitic infection. During June 2019 we conducted a cross-sectional baseline survey of 261 children (mean age 4.8 ± 0.75 years) attending 16 kindergartens and community care points across 4 provinces. Enterobius vermicularis was sought on peri-anal cellophane/Scotch-tape swabs (n = 261); Schistosoma haematobium in single urine specimens by the chamber-tube microscope-slide (CTMS) sedimentation method (n = 232); and intestinal helminths and protozoa in single stool specimens by the merthiolate–iodine–formaldehyde (MIF) concentration method (n = 175). Pinworm prevalence was 3.8% (10/261) and did not differ by sex (p = 0.76) or province (p = 0.83). S. haematobium ova were found in 0.9% (2/232), both in boys from recognised endemic foci. Intestinal parasites were detected in 41.1% (72/175), with no significant sex (p = 0.64) or regional (p = 0.70) variation; protozoa predominated (97.2% of positives) over helminths (4.2%; all Ascaris lumbricoides), the commonest species being Blastocystis hominis (61.1%) and Giardia lamblia (34.7%). These first baseline data reveal a high burden of intestinal protozoa alongside a low but measurable burden of pinworm and urogenital schistosomiasis in Eswatini preschool children, and support extending screening and preventive chemotherapy to this previously unmonitored age group using the simple, field-deployable cellophane-swab, CTMS and MIF methods.

Creptotrema funduli Mueller, 1934, has long presented an uncertain systematic position within the family Allocreadiidae. Previous phylogenetic analyses based on partial 28S rDNA sequences recovered this species as distinct from other members of Creptotrema, suggesting that its current generic placement may not reflect its evolutionary relationships. In the present study, we re-evaluate the taxonomic status of C. funduli through an integrative approach combining morphological observations and phylogenetic analyses based on 28S rDNA sequences. Our results consistently recover C. funduli outside the clade containing species currently assigned to Creptotrema. In addition, several morphological traits distinguish this species from congeners, supporting its recognition as a separate evolutionary lineage within Allocreadiidae. Based on these findings, we propose a new genus to accommodate C. funduli. The new genus is compared with closely related genera within Allocreadiidae, particularly those with one pair of oral lobes like Creptotrema. Our results highlight the need for continued taxonomic revision within the family and illustrate the value of integrating molecular and morphological evidence in resolving the systematics of allocreadiid trematodes.

Anuran amphibians play essential ecological roles and are considered important bioindicators. This is especially true during the larval stage, when tadpoles exhibit high sensitivity to parasitic infections, including trematode metacercariae. These infections can profoundly affect the physiology and morphology of juvenile hosts, potentially compromising tissues involved in osmoregulation, locomotion, and development. We analysed naturally infected tadpoles, performing parasitological screening and histopathological evaluation. Through field collection, euthanasia, histological processing, and microscopic analysis of the tissues, our results revealed that the presence of metacercariae is directly associated with progressive tissue damage. In the kidneys, after the establishment of the parasite in a previously healthy renal tubule, we observed alterations ranging from mild changes, such as a slight reduction in glomerular density in individuals with low infection intensity, to severe damage in highly infected individuals. In the tail musculature, the metacercariae were encapsulated between muscle bundles, forming cysts delimited by fibrous capsules, accompanied by alterations in the organisation of muscle fibres, disruption of connective tissue, and the presence of inflammatory infiltrate. Capsules surrounding the parasites were composed of both host tissues and parasite-derived structures. Their formation was frequently associated with necrotic areas and functional impairment. These findings demonstrate that trematode infection exerts progressive effects on the structure and morphology of renal and muscular tissues in tadpoles, with the severity of tissue damage increasing according to parasite infection intensity. Such alterations may compromise host tissue integrity and represent an important pathological consequence of natural trematode infections during the larval stage.