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.

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.

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.

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.

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 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.

Haemonchus contortus, a highly pathogenic gastrointestinal nematode, significantly impacts small ruminant production, causing substantial economic losses in sheep and goat farming. This study examined the genetic diversity and population structure of 171 H. contortus isolates collected from the abomasa of sheep slaughtered across 8 distinct regions in Xinjiang, China. Using sequence analysis, phylogenetic reconstruction and population genetic analyses of the mitochondrial nad4 gene, we identified 163 haplotypes, with haplotype diversity ranging from 0.995 to 1.000 and nucleotide diversity from 0.02007 to 0.03145. The Tacheng population displayed the highest nucleotide diversity. Analysis of molecular variance revealed that 91.83% of genetic variation occurred within populations, with minimal differentiation among them (Fst: −0.01296 to 0.04274). Neutrality tests (Tajima’s D and Fu’s Fs) indicated no recent population bottlenecks. Phylogenetic and haplotype network analyses showed no distinct geographic clustering, suggesting extensive gene flow, likely facilitated by host movement. These findings provide critical insights into the genetic structure of H. contortus in Xinjiang, informing strategies for managing anthelmintic resistance and controlling this economically significant parasite.

Research on helminth parasites of amphibians and reptiles has a long-standing history and has seen continuous growth. Recent efforts by various authors to compile comprehensive checklists are crucial for advancing our understanding of parasite diversity, ecology and evolution. Nematodes belonging to the family Molineidae parasitize vertebrates worldwide, with the genera Kentropyxia, Oswaldocruzia, Poekilostrongylus, Schulzia and Typhlopsia identified as infecting amphibians and reptiles across the Neotropical and Panamanian regions. While these parasites are relatively common, there is a lack of updated identification keys and incomplete information about their morphology, biology, distribution and host range. In this paper, we conducted an extensive bibliographic survey of Molineidae nematodes in amphibians and reptiles and provide a checklist of 53 species found in the Neotropical and Panamanian regions, including the Caribbean islands, along with updated details on their diversity, host range and geographic distribution.

Besnoitia besnoiti is an apicomplexan parasite, the causal agent of bovine besnoitiosis. This disease is characterised by cyst formation in the skin and mucosa. During early infection, fast proliferating tachyzoites invade and replicate within host endothelial cells. In non-excitable cells, extracellular signals activate the inositol-triphosphate/calcium (InsP3/Ca2+) pathway, which depends on phospholipase C (PLC) activation, inducing an increase in IP3 levels, followed by intracellular Ca2+ release. Despite the understanding of Ca2+ signalling, this process in B. besnoiti tachyzoites is unclear. This work aimed to study Ca2+ dynamics during B. besnoiti infection in bovine umbilical vein endothelial cells (BUVEC) and the role of the InsP3/Ca2+ pathway during B. besnoiti infection. Ca2+ dynamics during tachyzoite replication were determined in B. besnoiti-infected BUVEC loaded with fluo-4-AM. The role of InsP3/Ca2+ signalling for parasite invasion was evaluated by treatments with Ca2+ chelators (BAPTA, EGTA) or PLC inhibitors (U73122, D609). PLC activation was studied in fluo-4-loaded free tachyzoites using the PLC activator m-3M3FBS, in the presence or absence of PLC inhibitors. Current data show an infection-driven increase in total Ca2+ signals in B. besnoiti-infected BUVEC over time. BAPTA, but not EGTA, treatments of tachyzoites affected their invasion, reducing infection rates by 85.4 ± 9.3%, suggesting that intracellular Ca2+ sources are necessary for B. besnoiti invasion. In line, treatments with U73122 and D609 reduced infection rates by 79.3 ± 9.4% and 49.7 ± 8.9%, respectively, demonstrating that PLC participation is required for host cell infection. Finally, m-3M3FBS treatments induced a PLC-independent Ca2+ flux in B. besnoiti tachyzoites.

Giardiasis is the most common enteric protozoan infection notifiable in New South Wales (NSW), Australia. Surveillance by NSW Health had shown a steady increase (prior to the COVID-19 pandemic) in the number of cases reported since 2012 and the reasons for this currently remain unknown. This study aimed to investigate the occurrence of Giardia intestinalis assemblages causing human infection in NSW. Individual faecal specimens were collected from participating hospitals and private laboratories, and the presence of Giardia and co-infections was confirmed by real-time multiplex-polymerase chain reaction (PCR). Samples were genotyped by sequence analysis of the triose phosphate isomerase (tpi) gene and the small subunit rDNA. Combined genotyping showed that most samples belong to assemblage B, and only a small percentage were infected with only assemblage A. Mixtures of assemblages A and B in individuals were relatively common. Co-infections were observed in ∼ half of the cases, with the most common co-infection being Blastocystis hominis and Dientamoeba fragilis. Although giardiasis was more prevalent in males, the assemblage distribution between the sexes appeared uniform. The age distribution was bimodal, with peaks in 0–15-year-olds and in adults in their 30s. The overall largest number of cases was collected from patients aged 30–49 years. Interestingly, females aged 5 years old and under had a greater risk of assemblage B infection than their male counterparts. No significant correlation was found between assemblage and clinical symptoms. This study provides new insights into the molecular diversity of giardiasis in NSW and helps inform enhanced surveillance and prevention strategies in Sydney.

Parasites can strongly influence host populations, particularly when the host is an ecosystem engineer. Oysters are ecosystem engineers that support estuarine communities and fisheries but are susceptible to 2 protozoan parasites, Perkinsus marinus (causing Dermo) and Haplosporidium nelsoni (causing MSX). Although both parasites are known to be influenced by environmental conditions, fine-scale temporal and spatial patterns remain underexplored in southeastern US estuaries. We examined parasite prevalence and intensity biweekly from April to October 2023 across 4 intertidal reefs on Sapelo Island, Georgia, and analysed concurrent water quality data (temperature, salinity, dissolved oxygen, pH) to identify potential environmental drivers of parasite prevalence and intensity. Parasite prevalence was high overall, 88% of oysters were infected with at least 1 parasite, and 34% were co-infected. Haplosporidium nelsoni prevalence was consistently high across sites, while P. marinus prevalence showed greater spatiotemporal variability, increasing through late summer and fall. Models indicated a time-lagged effect of environmental conditions on P. marinus prevalence, specifically with temperature and dissolved oxygen. Prevalence of H. nelsoni remained high throughout the year among sites and was best explained by temperature variability, salinity, and dissolved oxygen. Intensity levels did not differ among sites for either parasite. Our results demonstrate that even at small spatial scales and over time, oyster–parasite dynamics are shaped by multiple, interacting environmental factors, with time-lagged responses particularly evident for P. marinus. Understanding these dynamics is essential for predicting disease impacts under changing environmental conditions and informing management, restoration, and aquaculture strategies.

The digenean trematode, Corrigia vitta, is a frequently reported component species in studies of helminth communities of wild rodents in Europe, especially those of wood mice and bank voles. It has been known since Dujardin first described the species in 1845, and yet its life cycle is still poorly defined, although Dicrocoeliidae typically have at least 3 hosts in their life cycles. Here, we review the history of nomenclature changes of the species, morphological studies, definitive mammalian host species range and evidence for the identity of intermediate hosts. We also review the epidemiology of C. vitta, searching for commonalities between studies that have assessed the effects of intrinsic and extrinsic variables on both prevalence and abundance of the species in wood mice. Furthermore, we identify gaps in knowledge and propose key objectives for future work on the species. We emphasize that if the life cycle of C. vitta could be established in the laboratory and maintained in laboratory mice, as a hepatopancreatic specialist in its definitive host, the parasite may turn out to be the source of novel medicines for the treatment of human pancreatic/liver diseases.

The heligmosomid nematodes Heligmosomum mixtum and Heligmosomoides glareoli are dominant helminths infecting bank voles (Clethrionomys glareolus) in the temperate forests of NE Poland. Both are relatively long-lived species that accumulate in hosts with increasing host age. Based on studies showing that the closely related species, Heligmosomoides bakeri is immunomodulatory in murine hosts, we hypothesized that heligmosomid-infected bank voles should show higher prevalence and abundance with other helminths. To test this hypothesis, we analysed a database containing quantitative data on helminth parasites of bank voles (n = 922), comprising worm burdens recorded during 4 surveys, conducted at 3- to 4-year intervals, in 3 forest sites, during late summer of each year. After controlling for both intrinsic and extrinsic factors, the presence of heligmosomid nematodes was significantly associated with higher species richness of other helminth species, with the greater likelihood of voles carrying other helminth species, with higher worm burdens of other helminths and with significant positive covariance of heligmosomid burdens with those of other concurrently residing helminths. These patterns might be explained by a number of biological processes, including correlated host exposure or correlated host susceptibility not driven by the parasitic infections themselves. However, we consider it most likely that these results are consistent with the idea that like H. bakeri, the heligmosomid nematodes of bank voles employ non-specific immunomodulation to facilitate their own long-term survival, with the consequence that other concurrently infecting intestinal helminths benefit.

Although venomous snakes from the family Viperidae, such as Bothrops atrox, are recognized for their medical importance due to snakebite accidents, few studies on parasitological aspects have been carried out with them, especially in the Amazonia region. Using morphological and molecular tools, we described a novel haemogregarine species infecting the common lancehead snake B. atrox from Eastern Amazonia, Brazil. Hepatozoon atrocis sp. nov. has mature gamonts that are morphologically distinct from those reported in the literature, which are often compact, with dispersed or encapsulated cytoplasm and chromatin. In the phylogeny recovered from the 18S rRNA gene, the Hepatozoon atrocis sp. nov. sequences formed a new clade, comprising a sister group to Hepatozoon spp. detected in other snakes, anurans, lizards and marsupials. This study reports the first Hepatozoon species described in the common lancehead snake. In addition, it provides a robust review of haemogregarine species infecting viperids from all over the world.

Phlebotomine sand flies are found across multiple regions of Thailand, with growing recognition of their role in transmitting zoonotic pathogens. Environmental factors, including climate variability and vector ecology, may influence their distribution and activity, contributing to the potential spread of zoonotic pathogens in Southeast Asia. However, comprehensive data on sand fly distribution in Thailand remain limited. To address this gap, a systematic review was conducted following PRISMA guidelines. Out of 112 records retrieved, 33 met the inclusion criteria and quality assessment for further analysis. As per results, sand flies are widespread in Thailand, with a high level of species diversity comprising 42 species of 6 different genera. However, several provinces lack data on the presence and distribution of sand flies. Eleven species were identified as the overall abundant species throughout the studies from January 2007 to June 2025 and grouped by abundance: low-abundance species (Sergentomyia barguesae, Sergentomyia phadangensis, Sergentomyia barraudi and Sergentomyia indica), abundant but understudied species (Sergentomyia sylvatica, Sergentomyia anodontis and Neopulpus vietnamensis) and most abundant species (Sergentomyia hodgsoni, Sergentomyia gemmea, Sergentomyia iyengari and Sergentomyia khawi). From the most abundant species, S. khawi tested positive for several pathogens, such as Leishmania spp., Trypanosoma spp., Bartonella spp. and orbivirus. Besides, S. khawi has been shown to exhibit human-biting behaviour through the analysis of blood meal. These findings raise concerns about its potential role in pathogen transmission, especially concerning zoonotic pathogens. However, vector competence remains unproven for some of these pathogens, suggesting the need for further research.

We applied 2 methods of phylogenetic regionalization (evoregions and phyloregions) for the distributions of fleas and their rodent hosts across Mongolia. We investigated the congruence between these 2 regionalization schemes and their alignment with physiographic and ecological subdivisions of Mongolia. We identified evoregions and phyloregions for both fleas and hosts. Ancestral regional distributions were reconstructed, and a phylogenetic correspondence analysis identified key contributing lineages. Using the V-measure, we tested for the congruence between (a) evoregions or phyloregions identified for fleas and evoregions or phyloregions, respectively, identified for their hosts and (b) evoregions and phyloregions identified for either fleas or hosts and each of the physiographic/ecological regionalization schemes of Mongolia. Four evoregions and 8 phyloregions were identified for both fleas and hosts, exhibiting distinct spatial patterns. Host-parasite regionalizations demonstrated moderate spatial similarity (V-measure 0.49–0.50), a significantly higher congruence than previously reported at the larger Palearctic scale (0.33). Flea regionalizations exhibited stronger congruence with environmental schemes than did host regionalizations. We concluded that evoregionalization and phyloregionalization capture distinct evolutionary signals, reflecting the role of in situ diversification vs. phylogenetic turnover resulting from dispersal. Host-parasite co-regionalization is scale-dependent, with increased congruence at regional scales. Despite adult fleas’ obligate host dependence, their regionalization is not merely a passive reflection of host biogeography but is also profoundly shaped by environmental conditions. These findings emphasize the importance of method choice, scale and eco-evolutionary interactions in shaping complex biogeographic patterns.

Rattus rattus is a known reservoir of zoonotic pathogens, including Bartonella and Rickettsia, transmitted by ectoparasites such as fleas, mites, lice and ticks. The circulation of Bartonella and Rickettsia in these vectors in Chile remains poorly characterized. To evaluate the association between ectoparasite abundance, prevalence and diversity (including lice, fleas, mites and ticks) and the presence of Bartonella and Rickettsia within ectoparasites collected from R. rattus across different anthropogenic gradients in Chile, a total of 1,339 ectoparasites were collected from 411 R. rattus individuals across 27 localities. Ectoparasites were identified morphologically, and molecular detection of bacteria was performed using conventional and qPCR, targeting multiple genetic markers. Haplotype diversity and phylogenetic relationships were assessed. Bartonella and Rickettsia DNA were detected in fleas, ticks, mites and lice of R. rattus, with prevalence values reported separately for pooled and individually analysed ectoparasites. Bartonella tribocorum, B. rochalimae and B. mastomydis were identified. Rickettsia felis was confirmed in multiple ectoparasite groups. High haplotype diversity was observed in Bartonella but not in Rickettsia. Urbanization and tick prevalence were negatively associated with Bartonella occurrence; flea and tick prevalences were negatively associated with Rickettsia. Rattus rattus and their ectoparasites harbour a diverse range of potentially zoonotic Bartonella and Rickettsia species. These findings highlight the need for integrated surveillance and vector control strategies, especially in areas with variable human-wildlife interaction.

Recently introduced parasites are predicted to cause more severe infections because of a lack of host-parasite co-evolution. When new parasites co-occur with similar parasites they may compete for resources within a host, with mixed species infections potentially resulting in antagonistic, synergistic or additive effects. We tested Ostrea chilensis flat oysters in New Zealand for infections by two species of haplosporidian oyster parasites. Bonamia exitiosa is an endemic parasite to New Zealand, whereas Bonamia ostreae is an introduced species first detected in New Zealand in 2015. We investigated the infection intensity of each parasite by estimating gene copy numbers using species-specific digital droplet PCR (ddPCR) across Bonamia spp. allopatric and sympatric ranges. Our results showed that B. ostreae had significantly higher gene copy numbers than B. exitiosa. However, concurrent infections of both Bonamia parasites had similar intensities (based on gene copy number) to single-species infections, with no detectable interactive effects. Collectively, the results indicate that B. ostreae remains a significant risk to O. chilensis, although coinfections may not exacerbate disease. This study demonstrates the value of ddPCR screening and the importance of considering evolutionary ecology in the management of commercially important marine diseases.

Theileria parva, a protozoan parasite, is the causative agent of East Coast fever (ECF), an economically important disease of cattle in sub-Saharan Africa. The Muguga cocktail vaccine which comprises 3 T. parva strains, namely Muguga, Kiambu 5 and Serengeti transformed, is used for immunization of cattle to control ECF. However, the relative contributions of these T. parva strains to vaccine efficacy are not fully understood. This study compared the in vitro infectivity of the strains at varying concentrations of 2.75, 84.5, and 169 infected acini/ml using peripheral blood mononuclear cells isolated from a bovine donor. The presence of Schizonts in cytospin smears was used to determine infectivity rates. The results indicated significant differences in the overall infectivity among the 3 strains at the concentrations 2.75 and 84.5 infected acini/mL but not at 169 infected acini/mL (p ≤ 0.05). These results suggest that infectivity potential reduces as the concentration increases. This was also supported by the observation that contamination increased at higher concentrations, complicating visualization and analysis. The findings reinforce the need to support the balanced composition of the Muguga cocktail vaccine to ensure broad-spectrum protection against ECF. This study emphasizes maintaining strain proportions in vaccine formulations. Future research should focus on advanced molecular techniques to refine infectivity assessments and explore strain-specific immune responses in vivo, contributing to optimized vaccine efficacy and sustainable control of ECF in endemic countries.