Snakes serve as important hosts for parasites at the interface of wildlife, humans and domestic animals. However, their helminth fauna in tropical regions, particularly Thailand, remains poorly documented. This study investigates the helminth fauna, community structure, infection patterns and their co-occurrence dynamics in the monocled cobra (Naja kaouthia) from urbanized areas of central Thailand, based on comprehensive analyses of 34 wild-caught individuals. Using integrated morphological and molecular approaches (e.g. mitochondrial 16S rRNA and COI gene sequencing), 11 helminth species were identified – 9 nematodes (Kalicephalus bungari, Kalicephalus sp. I and II, Paracapillaria najae, Paracapillaria siamensis, Serpentirhabdias orientalis, Strongyloides sp., a filarioid nematode and an unknown encysted nematode), 1 cestode (Duthiersia expansa) and 1 acanthocephalan (Sphaerechinorhynchus sp.) – including 2 newly described species: P. siamensis (infected in gastrointestinal tract) and S. orientalis (in respiratory tract). Serpentirhabdias orientalis and K. bungari were the most prevalent species (75.8%), while encysted nematodes exhibited the highest infection intensities (up to 500 parasites per host). Host–parasite network analysis revealed strong organ tropism in some helminth species (e.g. Paracapillaria spp.) and non-random co-occurrence patterns. Parasite abundance was positively correlated with host body condition, and females harboured greater species richness than males (11 vs. 8 taxa). The absence of trematodes is consistent with the host’s terrestrial ecology, while the low prevalence of filarioids (3.0%) suggests limited transmission. These findings underscore the value of integrative taxonomy in revealing hidden parasite diversity and highlight ecological drivers of infection patterns in snakes, with implications for wildlife health and zoonotic risk in human-modified landscapes.

Lagostonema ecasiense is a bursate nematode parasite of Lagostomus maximus in Argentina. New morphological data, geographical distribution, ecological data, molecular characterization and exploratory phylogenetic analysis are provided. The general morphology and measurements agree with the original description with minimal discrepancies. The geographical distribution of Lagostonema is expanded with 3 new provinces and 9 new departments in Argentina. The molecular characterization constitutes the first molecular contribution for the genus Lagostonema. The analysis of genetic distances and phylogenetic exploration allow considering L. ecasiense as a nominal species, confirming its nomenclatural taxonomic identity. Likewise, although morphological studies allow the identification of specimens from all populations as L. ecasiense, molecular studies show a major genetic distance in the population from Santiago del Estero Province concerning the rest of the populations. Consequently, the haplotypes are mentioned as Lagostonema sp. with the possibility that these specimens belong to a new species. This study is valuable because it contributes to the ratification of a nominal species described decades ago, adding new morphological aspects and providing an understanding of their value as a marker of host populations.

Exposure to environmentally transmitted parasites should increase with population density due to accumulation of infective parasites in space. However, resource competition also increases with density, lowering immunity and increasing susceptibility, offering an alternative pathway for density-dependent infection. To test the relationships between these two processes and parasitism, we examined associations between host density, resource availability, immunity, and counts of 3 common helminth parasites using a long-term study of red deer. We found evidence that immunity increased with resource availability while parasite counts declined with immunity. We also found that greater density correlated with reduced resource availability, and while density was positively associated with both strongyle and tissue worm burdens, resource availability was independently and negatively associated with the same burdens. Our results support separate roles of density-dependent exposure and susceptibility in driving infection, providing evidence that resource competition is an important driver of infection, exacerbating effects of density-dependent increases in exposure.

Comparative histopathological and ultrastructural investigations were performed on the livers of 2 fish species, namely, flounder (Platichthys flesus (L.)) naturally infected with the nematode Anisakis simplex (s.l.) (Rudolphi, 1809) larvae (L3) and tuvira (Gymnotus inaequilabiatus) (Valenciennes, 1839) harbouring the nematode Brevimulticaecum sp. (L3) (Shikhobalova and Mozgovoi, 1952). The intensity of infection by A. simplex (s.l.) larvae (L3) in flounders ranged from 3 to 10 parasites per organ. The worms were encapsulated by the peritoneal visceral serosa on the external surface of the liver. Infected P. flesus livers showed hepatocyte cytoplasmic rarefaction and cell swelling. A few immune cell types, such as macrophages, limited numbers of mast cells (MCs), lymphocytes and some epithelioid cells, were observed within the granuloma. The intensity of infection by Brevimulticaecum sp. (L3) in G. inaequilabiatus ranged from 4 to over 340 larvae per organ, and the nematode larvae were encircled by round-to-oval granulomas. Each granuloma possessed 3 concentric layers of cells and tissue: an inner layer in close proximity to the Brevimulticaecum sp. (L3) cuticle, formed by densely packed layers of epithelioid cells showing several desmosomes between each other; a middle layer of numerous MCs entrapped in a thin fibroblast-connective mesh; and an outer layer of fibrous connective tissue with thin, elongated fibroblasts. High numbers of macrophages and macrophage aggregates were scattered within the granuloma. This is the first study to compare the cellular nature of granulomas and the immune responses in the livers of paratenic fish hosts of 2 nematode species.

The Galapagos sea lion (Zalophus wollebaeki) is an endemic and endangered species that plays a vital role in the ecosystem dynamics of the archipelago. In recent decades, they have faced a significant population decline, related to the effects of climate variability and anthropogenic influences. Thus, the co-occurrence of sea lion resting areas with mosquito breeding sites and the presence of free-roaming domestic dogs present significant health risks related to parasite transmission. This research demonstrates the occurrence of Dirofilaria immitis (canine heartworm) in Z. wollebaeki, indicating their possible function as a definitive host for this parasite. Blood samples collected in August 2023 from 50 individuals (juveniles and adults) in 2 rookeries of San Cristóbal Island, revealed a 2% prevalence of D. immitis in juvenile females, as confirmed by Knott’s test and polymerase chain reaction analysis. Results of this work emphasize the critical necessity for effective monitoring and conservation strategies to address the threat posed by D. immitis and to safeguard this endangered species.

Ectoparasites are ubiquitous and are often harmful to host fitness. Whereas protective responses to ectoparasitism in vertebrate hosts are well documented, our understanding of such defences in invertebrates remains limited. Here, we examined attachment-resistance in adult Drosophila to their naturally co-occurring ectoparasitic mites, Gamasodes pachysetis (Parasitidae). Significant differences in mite attachment duration were documented among 6 species of Drosophila, providing evidence for interspecific differentiation in attachment-resistance. Experiments with D. malerkotliana, a species exhibiting a relatively high rate of mite detachment, revealed that pre-infesting flies significantly reduced mite attachment duration compared to naïve controls, indicating a priming effect. In contrast, a reduction in attachment duration was not observed in D. malerkotliana after experimentally wounding the abdominal cuticle. These results suggest that the priming effect is not simply a response to cuticle damage, and that its activation may depend on mite-specific factors. Eight genes were individually tested for their effects on the rate of mite detachment from adult flies by deploying the GAL4-UAS gene knockdown system in D. melanogaster. Knockdown of heat shock protein 70Ba (Hsp70Ba) and prophenoloxidase 2 (PPO2), which underlie general stress and melanization responses, respectively, significantly prolonged mite attachment duration, implicating their involvement in host attachment-resistance to mites. Together the results support the existence of inducible protective mechanisms mediating parasitism by mites in a naturally occurring invertebrate host–ectoparasite symbiosis.

Distinguishing between Stomylotrema bijugum and S. vicarium is challenging due to their phenotypic plasticity. In this study, adult specimens were recovered from 9 host species in the Mexican tropical lowlands. To explore the morphological differences, 32 morphological characteristics were evaluated in 54 specimens. Linear discriminant analysis provided enough evidence to differentiate the 2 species. Additionally, a principal component analysis (PCA) was performed for each species. The PCA of S. bijugum revealed 3 groups separately corresponding to specimens from the 3 hosts, suggesting host-induced phenotypic plasticity, whereas the PCA of S. vicarium revealed that the specimens from 3 host species were clustered together, indicating morphometric homogeneity. To confirm the morphological differences between the 2 species of Stomylotrema, we sequenced 2 molecular markers: the D1–D3 domains of the large subunit (LSU) from nuclear DNA and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (Nad1) from mitochondrial DNA. Sequences of the LSU were aligned and compared with the LSU sequences of other congeneric species available in GenBank. Phylogenetic analyses supported the monophyly of Stomylotrema, with 2 main subclades that corresponded to S. bijugum and S. vicarium. A haplotype network was predicted with 25 Nad1 sequences, revealing the presence of 2 clusters representing the 2 species separated from each other by 98 substitutions. The current studies on S. bijugum and S. vicarium revealed new hosts and geographical regions in the Americas, suggesting that both species addressed in the current study can complete their life cycle in the Neotropical region of Mexico.

Echinococcosis, caused by cestodes of the genus Echinococcus, poses significant public health and veterinary concerns globally. In Armenia, cystic echinococcosis (CE) is well-documented in livestock and humans, while alveolar echinococcosis (AE) has long been considered non-endemic. However, a recent retrospective study identified human AE cases, suggesting an underestimation of the parasite’s presence. To address knowledge gaps, a pilot survey was conducted to identify Echinococcus species and other taeniids in free-roaming dogs and wild carnivores in Armenia. Fecal samples (n = 112) were opportunistically collected from eight wild carnivore species and stray dogs across six Armenian provinces between 2017 and 2018. Samples were analysed for taeniid eggs using flotation and molecular techniques. Echinococcus multilocularis was identified in a free-roaming dog, marking the first confirmed detection of the parasite in a definitive host in Armenia. Additionally, E. canadensis G6/7 and E. ortleppi were detected in a wolf, while E. canadensis G6/7, Taenia hydatigena, and T. laticollis were found in a lynx. These findings indicate the involvement of both domestic and wild carnivores in the transmission cycles of Echinococcus species and suggest the presents of a potential sylvatic cycle involving E. canadensis G6/7 and E. ortleppi. The presence of E. multilocularis in a dog underscores the risk of human infection, necessitating further epidemiological studies. This study provides initial insights into the epidemiology of Echinococcus in Armenia and highlights the need for continued surveillance to assess public health risks.

Population dynamics of aquatic parasites respond to factors like host availability, habitat age and quality. Amphipods are intermediate hosts for Acanthocephala, a widespread group of parasitic worms. Acanthocephalan infections of amphipods can easily be detected, and the widespread occurrence of amphipods makes their infection status an attractive potential proxy for the ecological status of their aquatic environment, including stressors introduced by urbanization. This study investigated the prevalence and the species-level and genetic diversity of Acanthocephala in the stream amphipod Gammarus fossarum. The study streams cross forested, agricultural and urban landscapes in the eastern foothills of the European Alps. Parasite prevalence ranged from 0% to 8.8% and increased towards downstream reaches independent of surrounding land use. Oxford Nanopore Technology was used to sequence the mitochondrial cytochrome oxidase I barcoding locus to identify parasite species and assess their genetic diversity. The majority of the parasites were Pomphorhynchus tereticollis, which use fish as definitive hosts. Despite their relative abundance in the studied streams, their genetic diversity was low and the most common haplotype was found at all sampling sites, which might indicate population expansion. Amphipods also hosted P. laevis and Polymorphus sp. type 1, the first evidence of this cryptic species within Polymorphus cf. minutus in Austria. Genetic diversity was high in Polymorphus sp. type 1, possibly reflecting a large effective population size due to gene flow maintained by the avian final hosts. The low and downstream-biased prevalence suggests that definitive hosts may be a limiting factor for Acanthocephala populations in small streams.

Ochoterenella is a large group of filarial parasites of anurans distributed throughout Central and South America. In the present study, we describe a new species of Ochoterenella parasitizing 2 frogs, Boana geographica and Boana multifasciata, from different localities in the Brazilian Amazon. The main morphological traits that differ Ochoterenella casiraghii n. sp. from its congeners are the smaller body size, a shorter cephalic plate, smaller parastomal structures, and the small, short and rounded cuticular bosses on the body of both sexes. The females have a shorter ovejector, and the number of caudal papillae distinguishes males. Pairwise sequence comparisons of the new species reveal a high level of divergence from Ochoterenella spp. Our phylogenetic analyses, based on cox1 and concatenated partial mitochondrial genes, support the monophyly of all subfamilies and genera examined herein. The new species represents the 17th in the Ochoterenella genus and a new parasite record for both anuran species. We provide the first ultrastructural description of the species in the genus and establish the phylogenetic relationships of the new species among parasites of amphibians and reptiles from the Onchocercidae.

High density should drive greater parasite exposure. However, evidence linking density with infection generally uses density proxies or measures of population size, rather than measures of individuals per space within a continuous population. We used a long-term study of wild sheep to link within-population spatiotemporal variation in host density with individual parasite counts. Although four parasites exhibited strong positive relationships with local density, these relationships were mostly restricted to juveniles and faded in adults. Furthermore, one ectoparasite showed strong negative relationships across all age classes. In contrast, population size – a measure of global density – had limited explanatory power, and its effects did not remove those of spatial density, but were distinct. These results indicate that local and global density can exhibit diverse and contrasting effects on infection within populations. Spatial measures of within-population local density may provide substantial additional insight to temporal metrics based on population size, and investigating them more widely could be revealing.

We investigated the effects of body mass, geographic range size, the within-range richness of host assemblages (diversity field) and the habitat breadth of small mammalian hosts from 6 biogeographic realms on the species richness of their flea and gamasid mite faunas. We also tested whether the probability of between-host ectoparasite sharing is related to host phylogenetic relatedness, trait similarity or geographic distance/environmental dissimilarity between their ranges. We asked whether the effects of host-associated determinants of ectoparasite richness and the probability of ectoparasite sharing differ between (1) biogeographic realms and (2) fleas and mites. Whenever significant effects of host body mass on ectoparasite richness were found, they were negative, whereas the significant effects of geographic range size, diversity field and habitat breadth were positive. The occurrence of each determinant’s effects on ectoparasite species richness differed (1) within fleas or mites between realms and (2) between fleas and mites within a realm. In all realms, the probability of a flea or a mite species being shared between hosts decreased with a decrease in the hosts’ phylogenetic relatedness, trait similarity, geographic distance between ranges or environmental similarity. The probabilities of an ectoparasite species being shared between hosts were most strongly related to the hosts’ trait similarity and were least related to the environmental similarity. We conclude that caution is needed in making judgements about the generality of macroecological patterns related to parasites based on the investigations of these patterns in limited numbers of localities and when pooling data on various taxa.

Male genital schistosomiasis (MGS), a gender-specific manifestation of urogenital schistosomiasis and neglected tropical disease, typically results from the entrapment of Schistosoma haematobium eggs within the male genital tract. Across the world, there are no current and accurate estimates of the burden of MGS, due to disease underreporting primarily from diagnostic challenges and a lack of general awareness within the health system. Diagnostic methods for MGS are extremely limited. Conventionally, semen microscopy for Schistosoma ova is used though this technique suffers from low sensitivity and lacks protocol standardization. The introduction of molecular diagnostics, such as polymerase chain reaction (PCR), has partly helped overcome this challenge of low sensitivity, though may not be suitable for use in resource-constrained settings. To address these challenges, in this review, we propose a two-step diagnostic algorithm for MGS in accordance with recent WHO guidelines, consisting of a high sensitivity serological test followed by a high specificity test (microscopy or molecular assay, dependent on setting). Further investigation is required into standardization of sample collection, processing, storage, and analysis in order to identify an evidence-based optimal diagnostic pipeline. New diagnostic tools are needed such as isothermal molecular assays, alongside optimization for semen analysis, which may alleviate barriers to diagnosis and present opportunities for integration with other sexual and reproductive health screening. These areas of future investigation underpin the development of a suitable diagnostic pipeline, as the continued neglect of MGS and its underdiagnosis presents a threat to the goal of elimination of schistosomiasis as a public health problem.

Female genital schistosomiasis (FGS) is a chronic disease manifestation of the waterborne parasitic infection Schistosoma haematobium that affects up to 56 million women and girls, predominantly in sub-Saharan Africa. Starting from early childhood, this stigmatizing gynaecological condition is caused by the presence of Schistosoma eggs and associated toxins within the genital tract. Schistosoma haematobium typically causes debilitating urogenital symptoms, mostly as a consequence of inflammation, which includes bleeding, discharge and lower abdominal pelvic pain. Chronic complications of FGS include adverse sexual and reproductive health and rights outcomes such as infertility, ectopic pregnancy and miscarriage. FGS is associated with prevalent human immunodeficiency virus and may increase the susceptibility of women to high-risk human papillomavirus infection. Across SSA, and even in clinics outside endemic areas, the lack of awareness and available resources among both healthcare professionals and the public means FGS is underreported, misdiagnosed and inadequately treated. Several studies have highlighted research needs and priorities in FGS, including better training, accessible and accurate diagnostic tools, and treatment guidelines. On 6 September, 2024, LifeArc, the Global Schistosomiasis Alliance and partners from the BILGENSA Research Network (Genital Bilharzia in Southern Africa) convened a consultative, collaborative and translational workshop: ‘Female Genital Schistosomiasis: Translational Challenges and Opportunities’. Its ambition was to identify practical solutions that could address these research needs and drive appropriate actions towards progress in tackling FGS. Here, we present the outcomes of that workshop – a series of discrete translational actions to better galvanize the community and research funders.

Following the recent report of strongyloidiasis caused by Strongyloides fuelleborni within a semi-captive colony of baboons in a UK safari park, we investigated the genetic relationships of this isolate with other Strongyloides isolates across the world. Whole-genome sequencing data were generated with later phylogenetic analysis of mitochondrial (mt) cytochrome oxidase subunit 1 (cox1) and nuclear ribosomal 18S sequences against 300 published Strongyloides reference genotypes. The putative African origin of the UK S. fuelleborni was confirmed and full-length mt genome sequences were assembled to facilitate a more detailed phylogenetic analysis of 14 mt coding regions against all available Strongyloides species. Our analyses demonstrated that the UK isolate represented a novel African lineage not previously described. Additional complete mt genomes were assembled for several individual UK safari park worms to reveal a slightly altered mt genome gene arrangement, allowing clear separation from Asian S. fuelleborni. Furthermore, these UK worms possessed expanded intergenic regions of unknown function that increase their mt genome size to approximately 24 kilobases (kb) as compared with some 16 kb for Asian S. fuelleborni; this may have arisen from unique populational founder and genetic drift effects set within the peculiar mixed species baboon and drill ancestry of this semi-captive primate colony. A maximum likelihood phylogeny constructed from 14 mt coding regions also supported an evolutionary distinction between Asian and African S. fuelleborni.

Toxoplasmosis, caused by the obligate intracellular parasite Toxoplasma gondii, is one of the most prevalent zoonotic parasitic infections worldwide. When acquired during pregnancy, T. gondii can be transmitted to the fetus, with clinical outcomes influenced by gestational age at time of infection and the parasite’s genotype. Prenatal screening enables the detection of maternal seroconversion and offers a critical window for intervention. In Uruguay, despite mandatory serological screening during pregnancy, national data on T. gondii seroprevalence and maternal seroconversion have not been updated in two decades. In addition, the genetic diversity of local strains remains poorly characterized. In this study, we analysed publicly available serological data from pregnant individuals attending Uruguay’s largest public maternity hospital between 2019 and 2023. We found that seroprevalence has modestly declined from 50% (reported in 1998) to 45.5%, with a congenital transmission rate of 0.58%. Clinical analysis of affected newborns revealed chorioretinitis as the predominant manifestation. To investigate parasite diversity, we performed genotyping of T. gondii strains using in silico PCR-RFLP following molecular detection. Our findings revealed substantial genetic diversity, including novel allele combinations not previously described in the region. These results highlight both the continued public health burden and the evolving genetic landscape of T. gondii in Uruguay. Our findings underscore the need to strengthen surveillance and prevention strategies for congenital toxoplasmosis in South America.

Current liver-stage Plasmodium falciparum models are complex, expensive and largely inaccessible, hindering research progress. Here, we show that a 3D liver spheroid model grown from immortalized HepG2/C3A cells supports the complete intrahepatocytic lifecycle of P. falciparum. Our results demonstrate sporozoite infection, development of exoerythrocytic forms and breakthrough infection into erythrocytes. The 3D-grown spheroid hepatocytes are structurally and functionally polarized, displaying enhanced albumin and urea production and increased expression of key metabolic enzymes, mimicking in vivo conditions – relative to 2D cultures. This accessible, reproducible model lowers barriers to malaria research, promoting advancements in fundamental biology and translational research.

Detection approaches based on environmental DNA (eDNA) are widely used for free-living species but remain underutilized for parasite species. This study applies eDNA detection methods to elucidate the life cycle of the trematode Curtuteria arguinae, which infects the socioeconomically and ecologically important edible cockle (Cerastoderma edule) as its second intermediate host along the northeastern Atlantic coast, including Arcachon Bay, France. The first intermediate and definitive hosts remained unknown. To identify these hosts – presumed to be a gastropod and a shorebird – we developed a quantitative PCR (qPCR)-based eDNA approach targeting partial cox1 and SSU gene regions of C. arguinae. We tested for C. arguinae eDNA presence in water samples containing separately five dominant gastropod species and fecal samples from known cockle predators, the European oystercatcher (Haematopus ostralegus) and gulls (Larus spp.), collected in Arcachon Bay. C. arguinae eDNA was only detected in water containing the needle snail (Bittium reticulatum), with cercarial emergence confirming infection in 1.6% of individual hosts. Morphological analysis of the cercarial and metacercarial stages revealed variability in collar spine visibility. Additionally, C. arguinae was detected by qPCR in 42% of oystercatcher feces and no gull feces, suggesting oystercatchers are the definitive host. This study is the first to elucidate the complete life cycle of C. arguinae, identifying B. reticulatum as its first intermediate host and H. ostralegus as its definitive host. Our findings highlight the potential of eDNA approaches for resolving parasite life cycles and enabling advances in ecological research on C. arguinae.