Capillaria Moravec, 1987, is a genus of thin, threadlike roundworms infecting various hosts, including fishes. Fifteen species have been described from freshwater, brackish-water and marine fishes, primarily based on morphological characters. However, species identification remains challenging, and no molecular information is currently available for previously described Capillaria species. Utilizing morphological, scanning electron microscopy, and molecular evidence, we describe Capillaria (Procapillaria) nubthaiensis Chan, 2025 as a new species of capillariid infecting the commercially important fish Scomberomorus commerson from the Gulf of Thailand. Examination of 30 male and 30 female specimens revealed key morphological features distinguishing Capillaria nubthaiensis sp. nov. from other members of Capillaria (Procapillaria). These morphological characters include a unique female vulva that appears slightly protruding and forms a ‘knob-like’ shape appendage and a small papilla near the base of each male lobe with another pair of small papillae near the anus. Molecular phylogenies obtained from the nuclear 18S ribosomal RNA and the mitochondrial cytochrome c oxidase subunit I genes also support the distinction from other species in the family Capillariidae. The discovery of C. nubthaiensis sp. nov. represents the first record of a Capillaria species infecting S. commerson, and it is also the first to be recorded in Thailand’s marine waters. Alongside molecular information, this study contributes vital information beneficial for the taxonomy and biodiversity of capillariids in marine fishes.

The phytohormone auxin plays a crucial role in the development of so-called syncytia induced by cyst nematodes upon feeding on plant roots. However, it is unknown whether nematode-derived auxin contributes to plant parasitism by cyst nematodes. To do so, plant-parasitic nematodes should be able to produce and release auxin into the environment. Here, we investigated whether this is the case. Mass-spectrometry analyses show that the cyst nematode Globodera pallida is able to synthesize and release the auxin indole-3-acetic acid (IAA) and indicates that its biosynthesis can be stimulated by root diffusate. Using a collection of known auxin biosynthesis genes from well-studied pathways in bacteria and plants we revealed that in the genome of G. pallida candidate genes are present for 5 major biosynthesis pathways, which could be responsible for auxin production. RNA-seq data supported the genomic analysis and revealed the upregulation of various candidate biosynthesis genes during parasitic life stages of the nematode, suggesting a possible role in plant parasitism. However, genomic analysis within the phylum Nematoda showed that the potential auxin biosynthesis genes are wide-spread and also occur in bacterivorous, fungivorous, entomopathogenic and animal-parasitic nematodes. Therefore, our data show that G. pallida is able to synthesize and release auxin into the environment, but that potential auxin biosynthesis pathways are not unique for plant-parasitic nematodes. So, auxin biosynthesis may play a broader role in the life history of nematodes. However, a more specialized role for nematode-produced auxin in plant parasitism cannot be excluded and needs further investigation.

The family Camallanidae includes nematodes traditionally classified based on the morphology of their buccal capsules. However, several questions have been raised about the validity of these characteristics for their classification. Despite having a remarkable diversity, our knowledge of camallanids in Brazil remains limited, leaving gaps in our understanding of the true species diversity in the country, their geographical distribution and host species associations. Therefore, this study presents a checklist of species in the family Camallanidae recorded in Brazil, including a review for the classificationa and new dichotomous key for identifying the genera. Camallanidae comprises 2 subfamilies with 13 valid genera, classified based on the morphology of the buccal capsule and trident, and on the presence, shape and distribution of internal ridges on the capsule. Thirty-seven species, distributed across 7 genera, have been recorded in Brazil so far, parasitizing 276 host taxa, including fish, chelonians and snakes, with no records of these nematodes parasitizing amphibians in the country. We reallocated five species of Spirocamallanus and 2 species of Procamallanus to Denticamallanus, and 1 species of Camallanus was reallocated to Serpinema. Spirocamallanus is the most diverse genus, with 16 species, and Spirocamallanus inopinatus exhibited the highest host taxa association diversity (144) and the widest geographical distribution. Until further molecular studies are conducted, the new dichotomous key presented in this checklist contributes to a better understanding of the classification of the family Camallanidae, based on the morphology of the buccal capsule and accessory structures.

The genus Strongyloides (Nematoda; Strongyloididae) comprises over 50 species of nematodes parasitic in terrestrial vertebrates, including humans (Homo sapiens), dogs (Canis lupus familiaris) and cats (Felis catus). Taxonomy of the genus has been shaped by over a century of morphological research, with the most widely adopted framework established in the late 1980s. Advances in molecular genetics have increasingly revealed cryptic diversity and yielded new insights into interspecific and intraspecific relationships within the genus. Despite the rapid expansion of molecular genetic data over the past decade, particularly for Strongyloides spp. infecting humans and companion animals, a synthesis of these findings remains lacking. Here, we review historical and contemporary literature on the taxonomy of Strongyloides spp. infecting humans (Strongyloides stercoralis, Strongyloides fuelleborni), dogs (S. stercoralis, including host-specific lineages and cryptic taxa) and cats (Strongyloides felis, Strongyloides planiceps, Strongyloides tumefaciens and S. stercoralis). We provide an updated overview of taxonomic histories, host ranges and key morphological features for genus identification and species differentiation, along with a synthesis of available molecular taxonomic data informed by phylogenetic and population genetic studies. This work is intended to serve as a renewed reference for researchers, diagnosticians and clinicians working with Strongyloides spp. in medical and veterinary contexts, supporting accurate diagnosis and guiding future taxonomic research on these nematodes.

Strongyloides stercoralis is an intestinal nematode capable of infecting humans and dogs. Occurrence in dogs from temperate, traditionally non-endemic regions remains poorly characterized, often due to the absence of accessible veterinary diagnostic tests. Recent reports of infections from temperate metropolitan areas have raised concerns about the extent of S. stercoralis prevalence in dogs in these regions. This study investigated the presence of S. stercoralis DNA in canine faecal samples from Sydney, New South Wales, Australia, using a real-time quantitative PCR (qPCR) targeting the 18S rRNA gene, with a limit of detection of 2 DNA copies. Archived faecal DNA (n = 448) collected between 2014 and 2024 from 2 university veterinary hospitals were screened. Of all samples, 1 (0.02%) was positive for S. stercoralis DNA, corresponding to approximately 6.8 × 103 18S rDNA copies, equivalent to 3.2 of S. ratti third-stage larvae, per 250 mg of dog faeces. Partial cox1 and 18S rDNA loci (HVR-I and HVR-IV) deep amplicon sequencing confirmed that S. stercoralis circulates between dogs and humans. The positive sample originated from a Border Collie puppy presenting with gastrointestinal signs. Although detection was rare, this confirms the parasite’s presence in companion dogs within a temperate urban environment. The results highlight the diagnostic utility of 18S rDNA-based qPCR for retrospective surveillance and support the inclusion of S. stercoralis in molecular diagnostic panels for dogs with gastrointestinal disease. Expanded, targeted molecular and coproscopic surveillance is warranted to clarify the prevalence, distribution and zoonotic potential of S. stercoralis in dogs across Australia’s non-endemic regions.

Coinfections of hosts by multiple parasite species and strains are widespread in nature. Theory suggests that these infections have a key influence on the virulence, or harm caused, to hosts. However, it is still unclear whether multiple parasites, which may compete for resources and space, are indeed worse for hosts across the tree of life. To test this hypothesis, we conducted separate meta-analyses based on different expectations derived from virulence in single infections. We included 68 effect sizes from 19 experiments on non-human animal host species and 38 parasite species combinations. We found that coinfections are overall more virulent than the mean degree of harm caused by both parasites in retrospective single infections. That said, the coinfection virulence level is similar to that of the most virulent parasite, and less than the additive virulence of both single infections. These results suggest that the most virulent parasite is the primary driver of virulence in coinfection. This finding has implications for parasite spread in nature and suggests we focus on controlling the more harmful parasites in the first instance, when trying to limit the damage caused by coinfection.

Antimalarial drug resistance has evolved repeatedly and independently in both Southeast Asia and South America, but functional studies of parasite resistance have almost all concentrated on Asian isolates. Colombia contributes nearly one-third of all Plasmodium falciparum cases in South America, primarily focused on the Pacific Coast. We assessed the presence of resistance associated genotypes and phenotypes in this region using a panel of P. falciparum isolates collected across 23 years, with a specific focus on sensitivity to historically used antimalarials chloroquine, mefloquine, pyrimethamine and sulfadoxine. The sensitivity profiles were predicted genetically using a combination of quantitative PCR assays and sequencing of known resistance-associated loci, including the artemisinin resistance-associated gene PfKelch13. The isolates were then assessed phenotypically by introduction to in vitro culture allowing both antimalarial sensitivity testing and the establishment of a biobank of Colombian isolates for further work. We established that multiple antimalarial resistance associated genotypes and phenotypes, particularly for chloroquine and mefloquine, persist across the Colombian Pacific Coast but found no evidence for the presence of artemisinin resistance-associated polymorphisms. The continued presence of resistance against historically used antimalarials argues against the use of these drugs as partner therapy for artemisinin and highlights the unique epidemiological environment of the Pacific Coast which allows for long-term maintenance of resistance.

Monoplectanum monogeneans are gill parasites specific to fish in the family Sillaginidae. The sillaginid fish were collected from the middle and upper Gulf of Thailand and the Andaman Sea, Thailand, from May 2024 to January 2025. A total of 2096 fish belonging to 5 species- Sillago aeolus, S. asiatica S. indica, S. ingenuua and S. sihama were identified. Three species of Monoplectanum monogeneans were detected in 3 fish species, including 1 newly described species, M. sillaginis sp. nov. Monoplectanum sillaginis sp. nov. was found to infect 3 fish species, S. aeolus, S. indica and S. sihama, collected from the upper Gulf of Thailand. Monoplectanum youngi infected S. indica, representing a new host record, and S. sihama from both the middle and upper Gulf of Thailand. Monoplectanum australe was found to infect only S. aeolus, which was collected from the upper Gulf of Thailand. Overall prevalence and mean intensity of infections were 11.21% and 1.72, respectively. Regarding morphological features, no significant differences in key characters of both M. australe and M. youngi were observed when comparing the current and original descriptions. Monoplectanum sillaginis sp. nov., can be distinguished from these 2 species by the characteristics of its sclerotized male copulatory organ, particularly in the terminal part of the posterior prostatic reservoir, which is shuttle-shaped, as well as the number of rodlet rows in the squamodisc.

Calodium hepaticum (syn. Capillaria hepatica) is a generalist nematode that infects liver parenchyma of mammals worldwide and can cause human infections. Prevalence ranges from 0% to 100% in wildlife across small geographic areas, making it an ideal parasite for understanding ecological drivers of variation given intensive land use or cover change. Here, we quantify prevalence of Calodium hepaticum and present initial surveys of synanthropic small mammals. Cross-sectional rodent trapping was conducted within and around households over 2 consecutive dry seasons in 4 villages with differing land cover. DNA was extracted from liver tissue and the 18s rRNA gene of C. hepaticum was amplified to confirm presence of C. hepaticum. Landscape structural diversity was classified by tree crown density and mean canopy height derived from 30 m LiDAR data within a 0.5 km buffer. Multivariable binomial generalized linear models were fit to C. hepaticum prevalence. Calodium hepaticum infection was common (overall 34.5%, CI 95%: 27.9–41.0) and found in rodent and shrew species inside and outside residences. We observe village-level differences in prevalence (18.2–75.0%), with higher C. hepaticum prevalence associated with lower relative proportion of native rodent species to Rattus rattus (adjusted OR = 0.55, CI 95%: 0.33–0.92). Host diversity appears to be protective against parasite prevalence. Differences in molecular and gross parasitological identification highlight challenges in diagnosis and a need for more specialized molecular tools. Further investigation is required to understand individual host and community variation in pathogen infection intensity and implications for zoonotic risk.

Species of genus Clavellotis (Castro-Romero & Baeza-Kuroki, 1984) are parasites of marine fishes across the world. During the course of a survey on the metazoan parasites of marine fish across the Yucatán Peninsula, Mexico, specimens of a lerneapodid copepod consistent with the concept of Clavelotis were collected from the gills of three species of sparids, and were described as a new species using morphological and molecular characters. Clavellotis mayae n. sp. represents the second species of the genus reported in Mexican coastal waters. The new species morphologically resembles C. dubius and C. sebastidis in the trunk shape but can be readily distinguished by having a short maxilla which is separated to its distal end, a sub-oval and conspicuously larger aliform process, and a distal margin of the trunk bearing pronounced subcircular flaps covering the attachment sites of the egg sacs. The new species further differs from all other known congeners by having a short genital process and mandibles without secondary dentition. Molecular analyses through 28S rDNA and cox1 sequences further corroborate all these morphological distinctions and support the taxonomic placement of the new species within Clavellotis. The relationships of this species with other congeners are discussed in light of molecular evidence.