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.

Giardiasis remains a significant global health burden, constrained by limited diagnostic tools, the emergence of drug-resistant Giardia lamblia strains, and the absence of a licenced human vaccine. To address these critical gaps, this review provides a comprehensive functional analysis of the Giardia proteome, emphasizing molecular targets essential for the parasite’s survival and pathogenesis. We systematically examine the structural proteome, specifically the tubulin reservoir and the diverse giardin family (α-, β-, γ- and δ-giardins), elucidating their indispensable roles in the ventral disc attachment mechanism. Beyond structural components, we detail the ‘pathoproteome’, and moonlighting enzymes, highlighting how the secretome – including cathepsin B-like cysteine proteases (notably giardipain-1) and variant-specific surface proteins facilitate immune evasion and host intestinal epithelial damage. Furthermore, the review explores the metabolic and encystation proteomes, identifying unique enzymes such as carbamate kinase and fructose 1,6-bisphosphate aldolase that offer high therapeutic selectivity. By synthesizing these proteomic insights, this work identifies high-priority candidates for the development of next-generation therapeutics, prophylactic, and diagnostic interventions aimed at mitigating the global impact of this neglected disease.

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.

Pentanchids (Elasmobranchii) are among the most species-rich groups of chondrichthyans. In the North Atlantic Ocean, the Icelandic catshark [Apristurus laurussonii (Saemundsson)], white ghost catshark (Apristurus aphyodes Nakaya & Stehmann), and mouse catshark [Galeus murinus (Collett)] are commonly found in deepwater habitats. However, information on their parasite communities remains scarce. This study provides the first comprehensive characterization of the metazoan parasite communities of the 3 pentanchid species. In total, 56 specimens were collected in Icelandic waters at depths of 466–1322 m between 2023 and 2024 and examined using standardized parasitological protocols, including morphological and molecular methods. Infection patterns were assessed in relation to size, maturity, body condition and capture area of hosts. Parasite intensities in all sharks ranged from 2 to 227 individuals, comprising 15 different taxa and resulting in 27 new parasite–host records, some of which likely representing new species. Eight out of 9 commonly found parasites did not display a high degree of host-specificity, indicating similar feeding habits, niche preferences, and trophic position of these sympatric species. Nonetheless, multivariate analyses revealed significant differences in the structure and composition of their parasite assemblages, with some parasites representing indicator species and occurring more abundantly and frequently in a certain deepwater catshark species. In addition, significant small-scale geographic differences were detected. At a broader geographical scale, North Atlantic pentanchids showed higher parasite richness and diversity, and lower dominance compared to standardized data from Mediterranean counterparts. Ecological factors underlying these patterns on host–parasite dynamics in (deepwater) cat sharks are discussed.

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.

During a parasitological survey of the cockscomb hydrobe, Littoridinops monroensis (Gastropoda: Cochliopidae), sympatric saltmarsh fishes and the American alligator, Alligator mississippiensis (Alligatoridae) within a saltmarsh pond in the Bon Secour Bay (Mobile Bay, Alabama, north-central Gulf of America) and other localities, we collected specimens of Proctocaecum diploporum (Stunkard, 1931) Baugh, 1957 and Proctocaecum coronarium (Cobbold, 1861) Brooks, 1980 (Cryptogonimidae). Fish scales were infected with 2 metacercarial cyst size classes, a small (<200 μm) and a large (>240 μm), suggesting the presence of distinct but closely related sympatric cryptogonimids. Morphological and nucleotide evidence demonstrated that P. diploporum (small cyst) and P. coronarium (large cyst), previously regarded as taxonomic synonyms, share the same first intermediate host (cockscomb hydrobe), are encysted within the scales of the same fish host species, and mature in the intestine of the same definitive host. The taxonomy of these trematodes and that of another similar American alligator trematode, Caimanicola pavida (Brooks and Overstreet, 1977) Brooks, 1980, needed reconsideration. Herein, we describe the first complete and naturally occurring life cycle of a reptile-infecting cryptogonimid, provide the first nucleotide data for a species of Proctocaecum, taxonomically reassess both P. diploporum and P. coronarium, and designate a neotype for P. coronarium. We consider C. pavida a junior subjective synonym of P. coronarium. Phylogenetically related and sympatric trematodes that use the same invertebrate and vertebrate hosts such as these Proctocaecum spp. could be a good model to further explore the mechanisms of speciation and host specificity among trematodes with complex life cycles.

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.

Large gulls (Laridae) have expanded from coastal regions into inland Central Europe, where they increasingly exploit fishponds, landfills, and urban habitats. This shift alters their exposure to trematode parasites and their role in linking parasite transmission across ecosystems. We examined the trematode communities of 5 gull species (Larus argentatus, Larus cachinnans, Larus canus, Larus hyperboreus, and Larus marinus) collected in the eastern Czech Republic between 2022 and 2025. Complete helminthological examinations were performed on 207 individuals. Trematodes were detected in 82% of the birds, but the infection patterns differed among host species. Assemblages were overwhelmingly dominated by freshwater-transmitted taxa associated with cyprinid fish, particularly Diplostomum spp. and related genera. Pond-foraging gulls (L. argentatus and L. cachinnans) presented high prevalence, richness, and infection intensity, with frequent co-infections indicating repeated exposure within freshwater food webs. In contrast, L. canus and landfill-associated birds were often uninfected or lightly infected, reflecting limited participation in aquatic transmission cycles. Marine and brackish trematodes occurred sporadically and at low intensities, which is consistent with carry-over infections acquired in coastal regions without inland transmission. Community assemblages at the individual-host level were aggregated and consistent with stochastic exposure once the host species were considered. Maturity had little influence on helminth richness or diversity in gulls. Trematode assemblages closely reflected gull foraging strategies and habitat use, indicating that freshwater pond systems are the primary settings in which inland gulls may influence parasite transmission.

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.

Cryptosporidium muris is a gastric species primarily infecting rodents, whereas natural infections in cats are rarely documented and biologically poorly characterized. Oocysts of C. muris were detected in a cat and monitored for 120 days. Molecular characterization was performed on the small subunit rRNA, actin, 70-kDa heat shock protein, Cryptosporidium oocyst wall protein and thrombospondin-related adhesive protein of Cryptosporidium-1 loci. Oocyst morphology was evaluated microscopically. Infectivity and shedding dynamics were assessed in BALB/c mice and compared with C. muris RN66 and C. proliferans. Oocyst integrity during storage at 4°C was monitored for 60 days at 15-day intervals using flow cytometry and viability assays. The infected cat shed oocysts for 97 days, with a maximum intensity of 371 200 oocysts per gram (OPG), yet remained clinically asymptomatic. Developmental stages were confirmed histologically in gastric biopsy specimens. Haematological and biochemical parameters remained within reference ranges, and no concurrent parasitic, bacterial or viral infections were detected; only seropositivity to Toxoplasma gondii was recorded. All analysed loci showed 100% identity with C. muris RN66. Oocyst morphology did not differ from reference isolates. However, oocysts originating from the cat exhibited markedly reduced environmental stability, with a 90% decline in integrity within 60 days. Experimental infection of mice confirmed infectivity, but total oocyst output (32 300 OPG/days) was several orders of magnitude lower than that of C. muris RN66. Although genetically identical to rodent isolates, the feline-derived C. muris displayed altered biological properties, including reduced oocyst stability and transmission fitness. Cats may serve as susceptible but epidemiologically inefficient hosts.

Host age can indicate where avian helminths are acquired, but age patterns may also reflect seasonality, cumulative exposure and parasite persistence. We analysed age-specific prevalence, abundance and infection intensity in our long-term dataset of individually examined birds from the Czech Republic. Helminth taxa were classified statistically according to age and seasonal effects, and, independently, trematodes were assigned a priori to biogeographic groups based on their life cycles and intermediate-host distributions. Among 177 taxa retained for statistical analysis, 34 showed a pronounced adult-biased effect (Category A), 9 showed neither a strong adult effect nor significant seasonality (Category B) and 134 showed significant seasonal effects without meeting the Category A criterion (Category C). The independent biological classification provided clearer evidence of geographic acquisition. Trematodes associated with wintering grounds in southern Europe or Africa occurred in 0.21% of first-year and 3.12% of adult host–taxon associations. In contrast, nonlocal trematodes completing their life cycles elsewhere in Europe or marine taxa occurred in 0.70% and 2.01%, respectively. In contrast, cosmopolitan trematodes and those completing their life cycle locally were more prevalent in first-year associations. Most qualifying nonlocal species showed adult-biased prevalence, although Psilotrema oligoon and Psilotrema simillimum showed the opposite pattern. Several biologically nonlocal taxa were assigned to Category B or C because age and sampling month were strongly confounded, showing that failure to detect an independent age effect does not imply local transmission. Age-structured helminth data, therefore, provide a useful signal of migration-mediated parasite acquisition when interpreted together with parasite life cycles, intermediate-host distributions, seasonality and persistence.

Infectious diseases result from multiple interactions among microbes and hosts, but community ecology approaches are rarely applied. Manipulation of vector populations provides a unique opportunity to test the importance of vectors in infection cycles while also observing changes in pathogen community diversity and species interactions. Yet for many vector-borne infections in wildlife, a biological vector has not been experimentally verified, and few manipulative studies have been performed. Using a captive colony of fruit bats in Ghana, we conducted the first study to experimentally test the role of bat flies as vectors of Bartonella species. We observed changes in the Bartonella bacteria community over time following the decline of bat flies and again after their subsequent restocking. Reduced transmission rates led to microbial community changes attributed to ecological drift and potential species sorting through interspecific competition mediated by host immunity. We demonstrate that forces maintaining diversity in communities of free-living macroorganisms act in similar ways in communities of symbiotic microorganisms, both within and among hosts.

Ascaridia galli and Heterakis gallinarum, the most prevalent nematodes of chickens, inhabit the small intestine and caeca, respectively, and often co-occur. Current excreta egg count (EEC) methods do not differentiate between their eggs, and although chickens produce two distinct excreta types – intestinal excreta (IE) and caecal excreta (CE) – the distribution of eggs of these species across them remains poorly understood. Forty Hy-Line Brown laying hens (40 weeks, mean body weight (BW) 2·07 ± 0·02 kg), cleared of prior nematode infection and artificially infected with A. galli (n = 20) or H. gallinarum (n = 20) were housed in separate floor pens and monitored for 26 weeks. Assessments included clinical signs, EECs from IE, CE and mixed excreta (ME), and worm recovery from subsets of birds at 8, 14, 20 and 26 weeks. Neither infection resulted in clinical signs, but A. galli slightly reduced BW gain (0·5 g/week/hen) than H. gallinarum (2·8 g/week/hen). Egg detection aligned with worm predilection sites: A. galli eggs were predominantly found in IE, while H. gallinarum eggs were largely confined to CE. In ME samples, egg counts were reduced by 45% relative to IE for A. galli and 60% relative to CE for H. gallinarum. EECs showed a negative but non-significant association with excreta moisture content. Natural re-infection produced a stable adult worm population in both infections. These findings demonstrate that analysing IE and CE separately provides a practical, non-lethal approach for differentiating these infections, while ME appears to have limited diagnostic utility. Further studies should evaluate these patterns across broader conditions and individual variation.

Dientamoeba fragilis transmission is a basic aspect of this intestinal parasite’s biology that is poorly understood. Early historical reports reflecting the absence of a cyst are often cited as a central argument in debates supporting the lack of a D. fragilis cyst. While D. fragilis cysts have been described since Dobell’s original description, their existence is not universally accepted. Here, Dobell’s, Wenyon’s and Hoare’s collection of historical faecal smears stored at the Natural History Museum (London), dating back to the 1890s and the early 1900s, was examined for forms consistent with modern descriptions of D. fragilis cysts, and an example was found in 1 slide. Such rare forms were also detected during examination of stained faecal smears archived in the parasite reference laboratory collection at the United States Centers for Disease Control and Prevention. We discuss these observations in the context of literature describing cyst formation in parabasalids. Additionally, we report some incidental findings from past immunofluorescence experiments on cultured D. fragilis, which suggest differential staining that appears to correlate with life cycle stages. Considering published literature on the subject of D. fragilis cysts and the broader picture of cyst formation across diverse members of Parabasalia, we recommended that future investigations on D. fragilis transmission consider mounting evidence for the role of a true cyst despite its rarity in human faecal specimens. The factors leading to cyst formation and further characteristics of this life cycle stage require further study.

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.

Paraxerus cepapi is an arboreal tree squirrel that occurs in the Savanna biome of Africa, and information on its parasite diversity is limited and mostly qualitative. The aim of the study was to record the diversity and abundance of ecto- and helminth parasites associated with P. cepapi across its distribution in South Africa. P. cepapi individuals (n = 94) were opportunistically obtained from eight localities during 2020 to 2024. In total, 21 parasite species (19 ectoparasites and two nematodes) and one tick species group were identified. This included lice, ticks, fleas, a mesostigmatic mite, chiggers, nematodes and cestodes. Nematodes were the most prevalent (93·67%), followed by lice (80·85%). Syphatineria cepapi was recorded in 92·41% of P. cepapi, while an unknown Strongyloides species, resembling S. robustus, was recorded in 21·52% of squirrels. The lice species displayed variation in parasitope preference, while chiggers were primarily recorded in the ears. This study provides new country records for the lice species Werneckia paraxeri and Enderleinellus heliosciuri, for the chigger species Microtrombicula polymorpha, and for the nematode S. cf. robustus. New locality records were documented for the nematode S. cepapi in South Africa, and P. cepapi is a new host record for the eight chigger species and S. cf. robustus. It is evident that P. cepapi in South Africa hosts a considerably larger diversity of parasite taxa than previously recorded. Nematode counts were related to host length. These findings warrant future studies on the parasite diversity of P. cepapi in Africa.

Plasmodium vivax RH5-interactive putative protein (RIPR) is present in micronemes and might participate in erythrocyte invasion. In this study, the polymorphism of pvripr gene was examined. In 7 P. vivax isolates from southern Mexico (SM), the pvripr gene was amplified and sequenced. Other pvripr sequences were retrieved from PlasmoDB; 15 from SM and 78 from other locations. The genetic parameters, deviation from neutrality, Z selection test, haplotype networks, FST index of differentiation and the amino acid substitutions were analysed. The phylogenetic tree of 22 SM isolates suggested 2 genetic groupings, and these isolates had lower nucleotide diversity (n = 22; π = 0.0007, Hd = 0.671) than Colombian, Peruvian and Asian parasites (π = 0.0011–0.0017, Hd > 0.9). The haplotype network of Mexican pvripr had haplotypes separated by 1–13 mutational steps among them, and a complex structure was observed in parasites from Peru, Colombia and China. No significant deviation from neutrality was estimated; however, Tajima’s D values across 3′ segment were negative in parasites from all locations. The Z test was significantly positive only for Latin American parasites, and the codon-level selection analysis showed several codons with dN–dS positive values in East Asia and Southeast Asia parasites. Given the lack of long-term in vitro culture for P. vivax, in silico epitope mapping across global sequences provides a pragmatic, hypothesis-generating framework. Globally, 12 polymorphic residues involved charged amino acid changes, many within predicted B-cell epitopes, consistent with immune-mediated selection on PvRIPR.