South American ecosystems harbour diverse cricetid rodents and their associated nematode parasites, with implications for ecology and zoonotic risk. We conducted a systematic review following the PRISMA guidelines to catalogue nematode taxa reported from the digestive tract and accessory organs of cricetid rodents in Argentina and Chile. Searches were carried out in five databases (PubMed, WoS, Scopus, SciELO, and Google Scholar) up to 10 January 2026. Parasitological descriptors, such as prevalence (P), mean abundance (MA), and mean intensity (MI) were estimated. We analysed 53 studies examining 4400 rodents (33 species), with Abrothrix olivacea (n = 1000 specimens) and Akodon azarae (n = 775 specimens) most frequently sampled. Ninety-two nematode taxa were reported, with A. olivacea exhibiting the highest richness (17 taxa). Guerrerostrongylus zeta showed the highest P (97.56% in Oligoryzomys nigripes), followed by Stilestrongylus stilesi (92.5% in Necromys lasiurus) Peak infection intensities occurred with Stilestrongylus flavescens in O. flavescens (MA = 72.79/MI = 126.7) and St. stilesi in N. lasiurus (MA = 120/MI = 129.73). This review provides the first comprehensive synthesis of gastrointestinal and hepatopancreatic nematodes in cricetid rodents from Argentina and Chile, highlighting research biases and priorities for advancing our understanding of nematode–cricetid rodent dynamics in the region. The overrepresentation of A. olivacea underscores the need to expand the range of cricetid rodent sampled and to increase the use of non-invasive and molecular diagnostic tools. Addressing these gaps will improve our understanding of nematode diversity and associated zoonotic risks in cricetid rodents in these countries.

The genus Oochoristica Lühe, 1898 (Cyclophyllidea: Linstowiidae) primarily parasitizes reptiles. A new species of Oochoristica was collected from the small intestine of Eremias roborowskii (Bedriaga, 1906), from the Turpan Basin of the Xinjiang Uygur Autonomous Region, China. Following hematoxylin staining, through microscopic examination and detailed morphological description, a comparative morphometric analysis was conducted against closely related congeners, with particular emphasis on key taxonomic indicators, including the reproductive system and cephalic structures. Phylogenetic relationships were inferred using a multilocus analysis based on the 18S rRNA, ITS1-5.8S-ITS2 and COI gene regions. Genetic distances were calculated to support species delimitation. The parasite exhibits the following diagnostic features: proglottids significantly wider than long; a scolex lacking a rostellum and hooks; 20–25 spherical testes clustered in the posterior region of the proglottid; genital pores irregularly alternating along the lateral margins; a bilobed, highly branched ovary; and an elliptical vitellarium situated anterior to the ovary. Phylogenetic trees demonstrated that the new species formed a distinct, well-supported clade with lower intraspecific genetic variation than interspecific divergence, thereby supporting its status as an independent species. This new species is the 19th Oochoristica taxon recorded in the Palaearctic realm and the first novel cestode found in Eremias roborowskii. In the present study, an integrative taxonomic approach was employed, which combined comparative morphology with molecular phylogenetics and zoogeographic analyses, thereby elucidating the phylogenetic significance of this species within the genus Oochoristica.

This study reports the presence of Kudoa neothunni in yellowfin tuna (Thunnus albacares) landed in Portugal. The parasite was detected in fish harvested from the Indian and Pacific Oceans but not in the Atlantic Ocean specimens. Muscle samples collected from specimens were examined macroscopically and microscopically for parasitic infections. While no Kudoa cysts were observed macroscopically, microscopic analysis revealed K. neothunni in 10 fish (5 each from the Pacific and Indian Oceans), with a prevalence of 20.8% and 20%, respectively. Histological examinations confirmed the presence of Kudoa cysts in infected muscle tissue. Morphological analyses showed stellate spores with 6 polar capsules, and significant differences in spore length and polar capsule dimensions were found between isolates from the 2 oceanic regions. However, phylogenetic analysis based on small and large ribosomal subunit sequences indicated that both spores were consistent with K. neothunni and showed high (100%) similarity to previously published GenBank sequences. These results contribute to the current knowledge of K. neothunni occurrence in yellowfin tuna and indicate that infected specimens originating from the Indian and Pacific Oceans enter the European seafood market. Given that some Kudoa infections can induce post-mortem myoliquefaction and adversely affect fillet quality, this should be considered a potential concern.

The parasite fauna of Sardina pilchardus from the Black Sea coast of Türkiye was investigated. The parasitological survey was conducted on a total of 136 fish collected monthly from October 2024 to May 2025. A total of 7 parasite species were recovered: 5 digeneans (comprising 3 adult stages and 2 metacercarial stages), 1 larval nematode and 1 coccidian. The identified taxa included the adult digeneans Pronoprymna ventricosa, Lecithaster confusus and Aphanurus stossichii, metacercariae Stephanostomum sp. and Renicola sp., nematode Hysterothylacium aduncum, and coccidian Eimeria sardinae. Prevalence (%) and infection intensity indices were determined for each parasite species. Overall infection prevalence (82.35%), mean intensity (8.28 ± 0.74) and mean abundance (6.82 ± 0.67) were calculated. Infection parameters for each parasite species were determined and statistically compared across fish length groups, seasons, sex and host body condition factor. The results revealed that parasite abundance and intensity varied significantly among fish length groups and seasons, whereas no significant correlations were found with host body condition or fish sex. Spearman’s correlation analysis was performed to examine co-occurrence patterns among parasite species. A moderate positive correlation was detected between H. aduncum and Stephanostomum sp. (r = 0.494, P < 0.01). In contrast, associations among other parasite species were weak or negligible, indicating largely independent occurrence. Except for H. aduncum, all identified species represent new host records for this species in the Black Sea and Türkiye. Notably, Renicola sp. constitutes the first record of this genus for the parasite fauna of Türkiye.

Urbanization and tourism are intensifying human–animal interactions, yet their implications for cross-species parasite transmission remain poorly understood. This study investigates behavioural and ecological mechanisms underlying parasite transmission dynamics across interconnected human, dog and macaque populations sharing the same urban and touristic environment at Swayambhunath Temple, Kathmandu. We assessed parasite prevalence, diversity and infection intensity, combining parasitological analyses, participant questionnaire and behavioural observations to evaluate how anthropogenic factors and host behaviours influence parasitism and potential cross-species transmission. Humans displayed practices that may increase transmission risk, including close animal interactions, food provisioning and limited hygiene measures. Parasite prevalence was highest in macaques and dogs compared to humans, with macaques exhibiting the highest parasite diversity. Several parasites occurred in more than 1 species; notably, Entamoeba spp. was detected across all 3 species, indicating shared exposure pathways and zoonotic potential. In dogs, neither social nor anthropogenic variables predicted parasite metrics, but parasite diversity was linked to self-scratching, an indicator of anxiety, suggesting environmental pathway as a key drive of parasite transmission. In macaques, parasite diversity was shaped by interactions between dominance rank, provisioning and grooming, highlighting the interplay between social dynamics and human influence. Overall, these findings show that urban and touristic environments not only facilitate direct pathogen exposure but also indirectly shape parasite infection risk through behavioural and social mechanisms. Integrating behavioural ecology with urban disease ecology is essential for understanding and managing zoonotic risks in densely shared human–domestic animal–wildlife systems, with important implications for public and animal health and urban biodiversity management.

Avian Plasmodium, Haemoproteus and Leucocytozoon (Apicomplexa) are common parasites of birds that are highly prevalent around the globe. Despite their broad impacts on avian hosts, remarkably little is known about their transmission ecology, including the identity of competent vector species. Both Plasmodium and Haemoproteus are known to detrimentally impact mosquito survival but have generally been neglected in the consideration of mosquito ecology in the UK. Here, I sampled mosquitoes across 4 sites in Lincolnshire, east England, across 2 summers (April – July inclusive). 1026 mosquitoes were caught across 2 years, comprising 12 species, identified morphologically and confirmed genetically. Nine species (21 individuals; 5·8%; n = 363) had haemoparasite DNA in their salivary glands, with 2 lineages of Plasmodium, 3 of Haemoproteus and 1 of Leucocytozoon returning high-quality sequence. Ochlerotatus detritus is reported for the first time as a potential vector of Plasmodium vaughani (SYAT05), and Ochlerotatus annulipes and Anopheles messeae are reported for the first time as potential vectors of avian Plasmodium sp. (lineage LK06). Avian haemosporidians are diverse and widespread in UK birds and mosquitoes, and should be more widely considered in mosquito ecology in order to understand their complex transmission dynamics.

Micromammals are abundant in nature and have a significant role as reservoirs for various parasites and pathogens. Very little is currently known about Sarcocystis prevalence and species richness in wild micromammals from Mediterranean Spain. In the present study, a pool of heart, lungs, and brain of 371 individuals representing three species, Algerian mouse (Mus spretus), wood mouse (Apodemus sylvaticus), and white-toothed shrew (Crocidura russula), was screened for Sarcocystis using molecular methods. Animals were sampled across 4 seasons in both natural and agricultural habitats. Prevalence in white-toothed shrew (28%) was significantly higher than in wood and Algerian mouse (17% and 18%, respectively). The lowest prevalence occurred in autumn, whereas no significant differences were detected between habitats. Analysis of 28S rRNA sequences revealed 11 Sarcocystis lineages, with the highest lineage diversity observed in the Algerian mouse. Based on comparative sequence and phylogenetic analysis, most of these lineages are suspected to use snakes as definitive hosts (DHs), three are associated with birds, and the DHs for two lineages are likely mammals. Notably, cox1 sequences could not be used to confidently identify all lineages. Our results reveal substantial diversity of Sarcocystis in Mediterranean micromammals and provide new insights into their transmission cycles.

This study describes Vairimorpha rumexii sp. nov., a newly identified microsporidian parasite infecting Gastrophysa viridula, the green dock leaf beetle, in northeastern Türkiye. Microscopic examination revealed 2 distinct spore types, with light microscopy and Giemsa staining confirming both disporoblastic and octosporoblastic sporulation cycles characteristic of the genus Vairimorpha. Transmission electron microscopy provided detailed insights into spore ultrastructure, including polar tube configuration, spore wall stratification and nuclear arrangement. Molecular characterization using partial small subunit ribosomal RNA (SSU rRNA) and RNA polymerase II gene sequences, combined with phylogenetic analyses (maximum likelihood and Bayesian inference), placed V. rumexii sp. nov. in a distinct clade, closely related to but genetically separate from Vairimorpha gastrophysae. Notably, pairwise comparison of SSU rRNA sequences revealed a genetic distance of 0.0608 between the 2 species, supported by 72 nucleotide substitutions and 32 deletions, clearly indicating molecular divergence. The integration of morphological, ultrastructural and multilocus molecular data robustly supports its taxonomic distinctiveness as a novel species. This discovery expands the known diversity of microsporidia associated with Chrysomelidae, highlights the value of integrative taxonomy in resolving cryptic species and contributes to the understanding of Türkiye’s microsporidian fauna, potentially informing future biological control strategies.

The genus Contracaecum comprises anisakid nematodes with complex life cycles involving aquatic intermediate hosts and piscivorous birds as definitive hosts. The black-crowned night heron (Nycticorax nycticorax) is a widespread ardeid species known to host diverse helminth communities, including Contracaecum spp., although species-level identification is often lacking. In this study, we describe a new species, Contracaecum fioravantii n. sp., based on an integrative morphological and molecular approach. Adult nematodes were collected from 3 N. nycticorax individuals in Israel and examined using light and scanning electron microscopy. The new species is characterized by a distinct combination of morphological features, including robust, subequal spicules, a sagittate tail tip in males, and a specific arrangement of caudal papillae and phasmids, distinguishing it from closely related taxa such as C. microcephalum and members of the C. rudolphii complex. Multivariate morphometric analyses supported its separation from congeners. Molecular characterization based on ITS (Internal Transcribed Spacers) rDNA and cox2 mtDNA sequences revealed high similarity with previously unidentified Contracaecum spp. from ardeid hosts in China, and phylogenetic analyses placed the new species in a well-supported, distinct clade. These findings highlight the hidden diversity within Contracaecum and underscore the importance of combining morphological and molecular data for accurate species delimitation. The identification of C. fioravantii n. sp. contributes to a better understanding of host–parasite relationships in piscivorous birds and suggests a wider geographic distribution linked to migratory pathways of N. nycticorax.

Six freshly dead adult great cormorant Phalacrocorax carbo sinensis (Blumenbach, 1798) were collected during the winter season of 2025 from the coast of Canneviè lagoon (Northern Adriatic Sea, Italy). All 6 P. carbo sinensis (prevalence 100%) were infected with nematodes of the genus Contracaecum Raillet and Henry, 1912, with the intensity of infection ranging from 39 to 550 worms per host (212.8 ± 80.7; mean ± s.e.). From the same lagoon, 41 European seabass, Dicentrarchus labrax (L.), were examined for helminths and in 27 specimens (65%) L3 larvae of C. rudolphii were encountered in extraintestinal sites of the seabass. In this study, 40 adults and 30 larvae of C. rudolphii from cormorants and 40 nematode larvae from seabass were characterized at species level using the diagnostic key based on the Restriction Fragment Length Polymorphism of 2 ribosomal regions, the nuclear ITS and the mitochondrial rrnS (12S). Adult nematodes from cormorants were identified as Contracaecum rudolphii B 83.8% (31/37) and the remaining 16.2% (6/37) were C. rudolphii A. Of the 30 larvae recovered from bird stomach 84.2% (16/19) appeared to be C. rudolphii B and 15.7% (3/19) were C. rudolphii A and all parasites from the seabass were third stage larvae of C. rudolphii A. Histological sections of cormorant alimentary canal showed that the nematodes went into the depth of the gastric folds and induced detachment of epithelial cells and secretion of excessive mucus. Furthermore, near the worm site of attachment, different types of innate immune cells were documented.