Bees are key species for pollination and apiculture. Within the multiple biotic threats, parasites are one of the main players involved in bee health. Among them, trypanosomatid parasites have been the focus of recent studies that have placed them as one of the most prevalent microorganisms in the digestive tract of bees around the world. Here, we review what is known in epidemiology, cell biology and genetics of these parasites in bees with a particular focus on the work made on honeybees. We also discuss the possible implications for honeybee health and describe research gaps to be explored both from the honeybee host and trypanosomatid parasites sides.

An extensive survey of North American catostomid fishes yielded insights into the diversity, host specificity and phylogenetic relationships of monopisthocotylans belonging to Pseudomurraytrematidae. Parasites were recorded from 14 of 16 host species surveyed. In total, 22 species of Anonchohaptor, Icelanonchohaptor and Pseudomurraytrema were collected, including 7 new species. Most species were recovered from gills, whereas two Icelanonchohaptor species were found on fins. Phylogenetic analyses based on 28S rDNA support the monophyly of Pseudomurraytrematidae and its sister relationship to Diplectanidae. Within the family, Pseudomurraytrema asiaticum – a parasite of the East Asian fish Myxocyprinus asiaticus – was recovered as sister to the clade of Nearctic pseudomurraytrematids, a placement that may reflect geographic and host-associated separation. The remaining Pseudomurraytrema species parasitize North American Catostominae and form a well-supported clade sister to the clade comprising species of Anonchohaptor and Icelanonchohaptor, primarily associated with Ictiobinae. Under this topology, Pseudomurraytrema, as currently circumscribed, may be paraphyletic. Relationships between morphologically similar species of Anonchohaptor and Icelanonchohaptor remain unresolved: in the 28S tree, Anonchohaptor is paraphyletic (with Icelanonchohaptor nested within it), whereas the concatenated 18S–ITS1–28S analyses recover a single clade with Icelanonchohaptor (2 spp.) sister to the remaining species of Anonchohaptor. The parasite phylogeny broadly reflects host relationships, though several incongruences point to historical host switching. Morphological data also support the monophyly of Pseudomurraytrematidae via a synapomorphic male copulatory organ (U-shaped copulatory tube with a submedial spine, 3-ramus accessory piece), indicating structural conservatism within this family.

The genus Apharyngostrigea comprises a group of diplostomoidean digeneans that parasitize birds of the family Ardeidae (herons), with approximately 20 species described worldwide. Despite numerous efforts, a robust phylogenetic framework to delimit species within the genus is still lacking, mainly due to the limited morphological variation among its members. This study employed an integrative taxonomic approach, combining nuclear and mitochondrial DNA sequences with morphological data to assess species boundaries within Apharyngostrigea based on specimens collected from southeastern Mexico. Using a combination of species discovery (Automatic Barcode Gap Discovery, Assemble Species by Automatic Partition, General Mixed Yule Coalescent and Poisson Tree Processes) and validation methods based on Bayesian gene tree topologies (BPP and PHRAPL). We found high diversity within this genus in southeastern Mexico. Our analyses supported the delimitation of four nominal species that were previously described and validated in this study, along with the redescription of three of them. In addition, through species delimitation methods and morphological examination, we identified two candidate species and/or lineages that require further evidence to be formally described. This study demonstrates that an integrative taxonomic approach provides a robust framework for species delimitation in taxonomically complex groups such as Apharyngostrigea.

Global warming is widely recognized as a key driver of current and future changes in marine ecosystems. Parasitic trematodes are highly sensitive to temperature changes, which can lead to drastic impacts on surrounding communities. Copiatestes spp. (Family Syncoelidae) are relatively little-known trematodes with atypical life cycles that have been associated with a mass mortality event of seabirds in the Chatham Islands. As they forage at sea, seabirds get their legs tangled with the sticky, free-living infective stages of Copiatestes, which impairs their ability to take off and land. We tested the impact of seasonally fluctuating sea temperature on the dynamics of Copiatestes thyrsitae at various life stages (infecting second-intermediate host, Nyctiphanes australis euphausiid, and the third free-living infective stage in the water column) by sampling plankton biweekly for 12 months in Otago Harbour, New Zealand. We reveal that higher temperatures are significantly correlated with increases in prevalence and abundance of Copiatestes infections in euphausiids, with a rapid response observed within days to weeks following temperature increases. No correlation was observed between temperature and abundance of free-living stages. Infected euphausiids were smaller in size compared to uninfected individuals. The higher infection levels in euphausiids following warmer temperatures suggest a heightened risk of entanglement for coastal seabirds at these times. Smaller-bodied, surface-feeding seabird species that consume euphausiids are particularly at risk of entanglement. Our findings suggest that even short-term heatwaves can lead to higher risk of seabirds being entangled with Copiatestes filaments, with potentially dire ecological consequences during mass parasite releases.

Trypanosoma (Megatrypanum) pestanai is a parasite of the Eurasian badger (Meles meles), reported in various European countries. However, its presence in the Iberian Peninsula had not been previously investigated. To address this knowledge gap and to assess its occurrence and potential risk factors associated with infection, we analyzed DNA from the spleens of 145 badgers sampled across 4 autonomous regions in northern Spain. Two real-time PCR assays using a reference 18S rRNA partial sequence of T. pestanai (92 bp) were developed: one based on SYBR Green chemistry and the other employing a TaqMan probe. Both protocols demonstrated excellent concordance. Defining a sample as positive when at least 1 assay yielded a positive result, the overall prevalence was 35%, consistent with values previously reported in other European populations. A logistic regression model indicated a significantly higher occurrence in badgers from the Eurosiberian bioregion (42%) compared to those from the Mediterranean bioregion (19%). No significant associations were found with age or sex. A subset of positive samples was further analyzed by conventional PCR targeting approximately 900 bp of the 18S rRNA gene and sequenced. All 9 high-quality sequences shared 99.75–100% identity with known T. pestanai sequences. These findings confirm that T. pestanai is a common parasite of Iberian badgers and suggest that more humid climatic conditions may favour its persistence, potentially through effects on host ecology or vector dynamics.

The Liolopidae Dollfus, 1934 is a small family of digenetic trematodes with sexual adults parasitic in aquatic reptiles and amphibians. Liolopids exploiting snakes are constrained to Harmotrema Nicoll, 1914, but the genus includes species with presumably freshwater life cycles parasitic in terrestrial snakes as well as species with presumably marine life cycles parasitic in viviparous sea snakes and amphibious kraits. We hypothesize that this ecological distinction implies substantial separation in evolutionary history and propose Sagaratrema De Silva, Pathirana & Martin n. g. to accommodate the liolopids in marine snakes. Three species are delineated through an integrated approach, from novel collections of viviparous sea snakes in Sri Lanka, Sagaratrema rajapaksei De Silva, Pathirana & Martin n. sp., Sagaratrema rajakarunae De Silva, Pathirana & Martin n. sp. and Sagaratrema indicum (Chattapadhyaya, 1970) n. comb. (= H. indica) originally reported from India. Three other species known from marine snakes are transferred from Harmotrema to the new genus: S. laticaudae (Yamaguti, 1933) n. comb. (designated as the type-species), S. eugari (Tubangui & Masilungan, 1936) n. comb. and S. linguiforme (Wang, 1987) n. comb. (= H. linguiforme). The 3 species from Sri Lanka are similarly genetically distinct in sympatry as each is relative to S. laticaudae from Japan. Following these proposals, Harmotrema is revised and rendered monotypic for the type-species H. infecundum. Morphologically, Sagaratrema is distinguished from Harmotrema and other liolopid genera by the arrangement of the excretory vesicles, distribution of the vitellarium and size and shape of the body.

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.

Egg hatching is a critical stage in the life cycle of parasitic nematodes and is strongly influenced by abiotic factors. This study investigates, under in vitro condition, the effects of temperature (5 °C, 10 °C, 20 °C, 30 °C) and salinity (0–70 psu) on egg hatching success in the two sibling species Contracaecum rudolphii sp. A and C. rudolphii sp. B, which have been hypothesized to be adapted to brackish/marine and freshwater environments, respectively. Hatching was completely inhibited at 5 °C in both species. At temperature of 10 °C and above, both taxa showed successful hatching with largely overlapping thermal profiles; however, C. rudolphii sp. A achieved a marginally significantly higher success, with maximum hatching observed at 30 °C – a value chosen to simulate a potential heatwave scenario. Temperature also influenced developmental timing, with faster hatching occurring at higher temperatures. In contrast, significant marked differences were observed along the salinity gradient: C. rudolphii sp. A hatched across a wide range (0–70 psu); while C. rudolphii sp. B was restricted to 0–20 psu, with a steep decline above 10 psu. The observed species-specific hatching dynamics, primarily driven by salinity factor, support differential ecological adaptation of the two taxa in their respective aquatic habitats. These findings also provide a basis for predicting parasite responses to environmental change, including rising temperatures and salinity shifts in aquatic ecosystems.

This study reports the first rediscovery and redescription of Euclinostomum lauroi in more than 40 years, based on an adult specimen recovered from the oesophagus of a great white pelican (Pelecanus onocrotalus) in Lake Tana, Ethiopia. An integrative taxonomic approach combining detailed morphological examination and molecular analyses (ITS rDNA and COI mtDNA) was employed. Scanning electron microscopy revealed additional features, including the fine surface morphology of the cirrus and genital opening. The same host individual harboured 2 Clinostomum species, C. phalacrocoracis and C. tilapiae, for which updated morphological redescriptions are provided. The record of C. tilapiae represents a new geographical record for Ethiopia. These findings expand current knowledge of African clinostomid diversity and identify Lake Tana as an important hotspot of trematode biodiversity. The newly generated morphological and molecular data refine species boundaries within Euclinostomum and Clinostomum and support the use of integrative approaches to resolve persistent taxonomic uncertainties in clinostomid systematics.

Parasite transmission can be disrupted when their free-living larval stages are consumed by non-host organisms. Yet, the contribution of benthic scrapers to this process remains insufficiently explored. Here, we experimentally assessed the ability of the North American pulmonate snail Physa acuta to reduce the abundance of free-living digenean larvae – cercariae of Diplostomum sp. and Trichobilharzia sp., and adolescariae of Notocotylus sp. – and evaluated how this effect is modulated by snail body size and colonisation by other organisms. Larval consumption by P. acuta occurred in all treatments and was highest for settled Notocotylus sp. adolescariae, particularly among larger individuals. The extent of larval reduction varied with infection by digenean metacercariae (xiphidiometacercariae), which either enhanced or inhibited feeding depending on parasite identity. It also varied with colonisation by Chaetogaster limnaei limnaei, whose presence increased the ingestion of planktonic cercariae, likely due to the combined feeding activity of the snail and its commensal oligochaete. Most snails harboured metacercariae, indicating that P. acuta frequently functions as a second intermediate host in its non-native range. Our findings highlight the dual ecological role of P. acuta – both as a consumer of free-living parasite stages and as a competent host. This trophic interaction may disrupt parasite transmission while providing nutritional benefits that support the ecological success and spread of this non-native species. Conversely, by serving as a host, P. acuta may facilitate the persistence and dissemination of parasitic taxa in invaded ecosystems.

Parasitic worms have significant medical, veterinary and economic importance. Numerous studies have therefore addressed various aspects of parasitic worms’ biology. In contrast, the ploidy of parasitic worms remains comparatively understudied, despite a few known triploid species. Polyploidy is known to have phenotypic and genetic effects in animals, which can lead to changes at the evolutionary scale. The evolutionary consequences of polyploidy have been addressed in host–parasite systems; however, most studies have focused on the host perspective, with relatively few studies examining the parasitic side of the story. This review provides available information on the distribution of triploidy among parasitic worms, along with information on such aspects as reproduction, origin of triploidy and life history. Across 100 selected papers (out of 416 screened), triploidy was reported for 15 parasitic Platyhelminthes and 13 parasitic Nematoda. Most triploid species of parasitic worms (24 out of 28) were documented at the adult stage. Triploid lineages reported for the adult stage reproduce predominantly via parthenogenesis. Finally, the paper discusses the potential effects of ploidy variation for host–parasite dynamics and adaptation rates of parasitic worms. In particular, how parasitic worms adapt to their hosts despite potential constraints of asexuality. As well as whether triploid individuals outcompete diploid conspecifics when both ploidy levels coinfect the host, as could be expected if triploids have higher virulence.

A fossil assigned to the extant ixodid genus Haemaphysalis was previously described from the Late Cretaceous (ca. 99 Ma) Burmese amber. Haemaphysalis (Alloceraea) cretacea was considered the oldest, and only, fossil representative of this genus. Significant criticism was raised regarding possible misidentification of this amber fossil. Microtomography of the original holotype and new material allows new perspectives on this controversy. A new fossil nymph is described and both fossils are considered Alloceraea cretacea comb. nov. nymphs based on a series of morphological characters: no genital aperture, eyeless, 11 festoons, coxa I simple with a short, wide triangular spur. Specific morphological features for the ‘structurally primitive’ Alloceraea are discussed and include palpi elongate, with long setae on palps, the hypostome dorsally longer than the chelicera and the corona visible distally and with a specific distribution of the denticles. Alloceraea and its sister genus Archaeocroton (that includes amber fossil taxa), share a common ancestor with Haemaphysalis sensu stricto, indicating a minimum divergence time of at least 100 MYA for these lineages. In addition, a fossil of Bothriocroton has also been described from Burmese amber. This genus with Cryptocroton groups basal to the Alloceraea/Archaecroton-Haemaphysalis assemblage forming a monophyletic clade named Haematobothrion. A synthesis of the fossil information and the current systematic understanding of the Haematobothrion allows new hypotheses about the origins of this group and the various lineages it comprises. Notably that the major Haematobothrion lineages originated and diverged during the time period when the Burma terrane was migrating from Australia to Asia.

The probability that a disease will manifest is highly variable. Susceptibility to disease is influenced by genetic background, environment and lifestyle choices. In this review, we put forward the premise that evolution of disease susceptibility may be partially influenced by the interaction of divergent pathogen DNA-binding proteins with variable binding sites in the host genome. The hypothesis put forward is derived from recent data obtained from work on the protozoan parasite, Theileria annulata, together with related evidence from viral and bacterial pathogens that have been postulated to modulate host epigenome architecture. The pathogen proteins highlighted have the potential to mimic functions of mammalian epigenome organisers linked to a range of disease syndromes. It is feasible, therefore, that the evolutionary relationship between pathogen and host impacts susceptibility to a range of conditions, such as autoimmune disorders and cancer, which are not directly linked to pathogen infection.

Ectoparasites are commonly found on wild birds and might play an important role as vectors of pathogens. The Balearic Islands archipelago (Spain) is an ecological hotspot for wild birds due to its geographical location and habitat diversity. Although the avian fauna of the archipelago is well studied, little information is available regarding the ectoparasites infesting its wild bird populations. This study aimed to identify the diversity of ectoparasites (chewing lice, louse flies and ticks) and feather mites on wild birds in several locations on Menorca Island, as well as to assess the prevalence based on the migration status and season. Our research revealed that ten of the 13 species of chewing lice collected in this study are reported here for the first time in the Balearic Islands, including two that are also new records for Spain. We did not find statistically significant differences in the prevalence of ectoparasites or feather mites between sedentary and migratory birds. Likewise, no significant differences were observed in feather mite prevalence among migratory birds from Illa de s’Aire between prenuptial and postnuptial migrations. This study provides valuable insights into the prevalence and diversity of ectoparasites, shedding light on their potential role as vectors for avian pathogens. Further research is needed to explore the pathogens these ectoparasites may carry and transmit, contributing to a better understanding of the epidemiology of avian diseases in Menorca.

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 nematode genus Rhabdias comprises over 100 species of parasitic nematodes that infect amphibians and reptiles, with a wide geographical distribution. To date, 25 species have been reported from the Neotropical region. Despite this diversity, few integrative studies, combining morphological and molecular data have been conducted to characterize species within the genus. Therefore, the main objective of the present study is to describe, through an integrative approach, a new species of Rhabdias found parasitizing the lungs of an anuran with a high concentration of skin toxins, Dendrobates tinctorius, from the Brazilian Amazon. The new species of Rhabdias is characterized by an elongated body, uniform cuticular inflation attenuated at the extremities, 4 submedian lips and 2 lateral lips, a cup-shaped buccal capsule, and an elongated tail. The morphology of the buccal capsule in Rhabdias camposi n. sp. is also unique among Rhabdias representatives, as this morphological character is known so far. Thus, we emphasize that a detailed study of this morphological trait for species of the genus will be crucial for species diagnosis. Molecular and phylogenetic analyses were performed using mitochondrial COI gene sequences. We observed that the new taxon is closely related to Rhabdias waiapi, a parasite of Pristimantis chiastonotus. Rhabdias camposi n. sp. represents the 26th species of the genus reported from the Neotropics in amphibians and the first described from a Dendrobates tinctorius host in Brazil.

Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris and Sappinia spp. are free-living amoebae that can infect humans and cause serious disease; therefore, these organisms are commonly referred to as pathogenic free-living amoebae (pFLA). Diagnosis and treatment of pFLA infections have historically been very challenging. If a diagnosis is made, treatment regimens currently include a combination of antifungals, antimicrobials and anticancer agents that have, to date, proven to be of little help in resolving the disease. Discovery of new therapies is critical to reduce the >90% mortality rate for the brain infections that these microbes can cause. Molecular tools that allow for the study of gene function, generation of reporter cell lines and drug target validation would greatly improve drug discovery efforts. To date, transfection approaches for use with pFLA have been limited, hindering these types of molecular studies. Based on sequence comparisons, the pFLA harbour proteins that are involved in cargo delivery to the nucleus and DNA repair mechanisms, suggesting that fundamental pathways believed to be required for stable transfection are present. However, the amoebae lack homologs to genes connected to stable maintenance of transgenes and RNA interference in other systems. While these differences may limit our ability to alter gene expression, it is also possible that unrecognized components fulfill the roles of the missing homologs. Given the value of robust transfection approaches in drug discovery and gene function studies, resolving these mechanisms would be impactful, leading to improved understanding of amoebae biology and enhancement of drug discovery efforts.