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Most hosts, including humans, are simultaneously or sequentially infected with several parasites. A key question is whether patterns of coinfection arise because infection by one parasite species affects susceptibility to others or because of inherent differences between hosts. We used time-series data from individual hosts in natural populations to analyze patterns of infection risk for a microparasite community, detecting large positive and negative effects of other infections. Patterns remain once variations in host susceptibility and exposure are accounted for. Indeed, effects are typically of greater magnitude, and explain more variation in infection risk, than the effects associated with host and environmental factors more commonly considered in disease studies. We highlight the danger of mistaken inference when considering parasite species in isolation rather than parasite communities.

Microtus fortis ( M. fortis ) is the only mammal known in China that is intrinsically resistant to Schistosoma japonicum ( S. japonicum ) infection. Nevertheless, the underlying resistance mechanism of M. fortis against schistosomes are still unclear. In this study, we detected and compared colon aqueous extracts and serum metabolic profiles between M. fortis and ICR mice before and after S. japonicum infection using liquid chromatography–mass spectrometry (LC–MS). We identified 232 specific colon aqueous extract metabolites and 79 specific serum metabolites of M. fortis infected with or without S. japonicum at two weeks compared with those of ICR mice, which might be closely correlated with the time-course of schistosomiasis progression and could also be used as indicators for the M. fortis against S. japonicum , for example, nonadecanoic acid, hesperetin, glycocholic acid, 2-Aminobenzoic acid, 6-hydroxydaidzein and spermidine. And the enriched pathways were further identified, our findings revealed that S. japonicum infection induced the metabolic changes involved in a variety of metabolic pathways including amino acid metabolism, lipid metabolism, ABC transporters, central carbon metabolism in cancer and bile secretion. These results indicated that the colon aqueous extracts and serum metabolic profiles were significantly different between M. fortis and ICR mice before and after S. japonicum infection and will provide new insights into the underlying resistance mechanism of M. fortis against S. japonicum infection and identify promising candidates for the use of drugs against schistosomes.

Wood mice ( Apodemus sylvaticus ) and bank voles ( Myodes glareolus ) are often employed as natural study models in infectious disease ecology. Yet the identities of some elements of their parasite fauna have been subject to long-standing confusion. One instance of this relates to 2 nominal species of the capillariid nematode genus Aonchotheca : Aonchotheca annulosa (Dujardin, 1845) and A. murissylvatici (Diesing, 1851). Through literature review, analysis of recorded host- and site-specificity and tracing of taxonomic precedence, it is possible to confirm that A. annulosa is a valid species with a spicule c. 1000 microns long, a small intestinal site of infection and a wide host range centred in murine rodents (with A. sylvaticus the most common host). On the other hand, tracing the provenance of A. murissylavtici through to the works of the early naturalists reveals it is best assigned as a nomen nudum (lacking sufficient establishing description) or a junior synonym of A. annulosa and does not have precedence for the other Aonchotheca morphotype commonly found in Eurasian rodents. The first description consonant with this other morphotype, which has a short spicule (200–250 microns in length) and occurs primarily in the stomach of bank voles and other cricetids, was as Capillaria halli by Kalantarian in 1924. We thus recommend the suppression of A. murissyvatici in favour of Aonchotheca halli (Kalantarian, 1924) for this gastric-specialist short-spicule morphotype, particularly as the use of the A. murissylvatici name and its variants has previously been associated with substantial inconsistency and misidentification with A. annulosa .

Host–parasite interactions arise from a complex interplay of evolutionary history, ecological context, and community structure, yet these dimensions are rarely examined together. Here, we introduce a unified framework that links the macroevolutionary processes shaping host–parasite associations with the microevolutionary dynamics driving intraspecific viral and host diversity. This approach reveals how evolutionary and ecological forces jointly structure parasite and viral diversity across a host’s range. We used the hantavirus host Oligoryzomys longicaudatus in South America as a model system to explore this analytical framework. The objective of this study was to uncover potential factors contributing to parasite and viral diversity in this system in a framework that can be applied to other disease systems. Our data suggest that parasite richness peaks in environmentally optimal, central regions of the host’s range, while hantavirus diversity peaks toward environmental and geographic margins. This dynamic connection among host ecology, parasite community turnover, and viral evolution illustrates how geographic and environmental variation influence host-parasite evolution. By bridging micro- and macroevolutionary signals, our analytical framework provides a biologically sound approach for describing host, parasite, and viral diversification in a changing world, and a foundation to explain how diseases emerge across changing landscapes.

The reed vole ( Microtus fortis ) serves as a significant rodent model, particularly distinguished by its robust natural resistance to Schistosoma japonicum infection. To unravel the genetic basis of this remarkable immunity, we present the first chromosome-level genome assembly for M. fortis . Employing PacBio HiFi long-read sequencing combined with Hi-C scaffolding, we constructed a high-quality 2.29 Gb genome. This assembly is anchored into 26 pseudomolecules, achieving a contig N50 of 68.89 Mb and incorporating 97.73% of the sequence into scaffolds. The genome demonstrates high completeness (BUSCO score 96.3%, glires_odb10) and a repeat content of 42.93%. Comparative genomic analysis revealed a high degree of synteny (95%) and a well-conserved chromosomal structure between M. fortis and Mus musculus .Phylogenetic analysis positions M. fortis diverging approximately 4.9 million years ago from other examined Microtus species and supports its classification within the Alexandromys subgenus. Notably, gene family evolution analysis identified significant expansions in immunity-related pathways. These expansions prominently involve T-cell receptor (TRAV, TRBV) and Major Histocompatibility Complex (MHC) class I and II genes. Further analysis highlighted an extensive lineage-specific expansion and diversification of the MHC class I gene family, predominantly clustered on chromosome 22. These genomic attributes, particularly the amplified T-cell receptor and MHC gene repertoires, are likely key contributors to the potent immune response and natural parasite resistance of M. fortis . This high-quality genome assembly provides an invaluable resource for advancing research into the adaptive evolution and unique biological traits of M. fortis , especially its parasite resistance mechanisms.

Using diagnostic data and contemporary sampling efforts, we conducted surveillance for a diversity of pathogens, toxicants, and diseases of muskrats ( Ondatra zibethicus ). Between 1977 and 2019, 26 diagnostic cases were examined from Kansas and throughout the Southeast and Mid-Atlantic, USA. We identified multiple causes of mortality in muskrats, but trauma (8/26), Tyzzer’s disease (5/6), and cysticercosis (5/26) were the most common. We also conducted necropsies, during November 2018—January 2019 Pennsylvania muskrat trapping season, on 380 trapper-harvested muskrat carcasses after the pelt was removed. Tissue samples and exudate were tested for presence of or exposure to a suite of pathogens and contaminants. Gastrointestinal tracts were examined for helminths. Intestinal helminths were present in 39.2% of necropsied muskrats, with Hymenolepis spp. (62%) and echinostome spp. (44%) being the most common Molecular testing identified a low prevalence of infection with Clostridium piliforme in the feces and Sarcocystis spp. in the heart. We detected a low seroprevalence to Toxoplasma gondii (1/380). No muskrats were positive for Francisella tularensis or Babesia spp. Cysticercosis was detected in 20% (5/26) of diagnostic cases and 15% (57/380) of our trapper-harvested muskrats. Toxic concentrations of arsenic, cadmium, lead, or mercury were not detected in tested liver samples. Copper, molybdenum, and zinc concentrations were detected at acceptable levels comparative to previous studies. Parasite intensity and abundance were typical of historic reports; however, younger muskrats had higher intensity of infection than older muskrats which is contradictory to what has been previously reported. A diversity of pathogens and contaminants have been reported from muskrats, but the associated disease impacts are poorly understood. Our data are consistent with historic reports and highlight the wide range of parasites, pathogens and contaminants harbored by muskrats in Pennsylvania. The data collected are a critical component in assessing overall muskrat health and serve as a basis for understanding the impacts of disease on recent muskrat population declines.

Rodents serve as hosts for many species of parasites, including cestodes, but the taxonomy of rodent-infecting tapeworms, especially in Central Europe, is still understudied. Therefore, the current study was conducted to identify larval and adult cestodes in free-living rodents from Northeastern Poland. The fieldwork was conducted between 2014 and 2023 in three forest sites. Cestodes were collected from five rodent species (Clethrionomys glareolus, Alexandromys oeconomus, Microtus agrestis, Apodemus agrarius and A. flavicollis, and were identified through morphology and by several genetic markers (12S rDNA, cox1, nad 1, 28S rDNA, 12S-16S rDNA) using phylogenetic analyses. A total of 58 cestode specimens were analyzed using molecular and phylogenetic analyses. Species identified included Catenotaenia henttoneni, Spasskijela kratochvili, Mesocestoides litteratus, Mesocestoides melesi, and others. Three Paranoplocephala specimens were identified as P. kalelai based on nad1 sequences. Morphological and genetic analyses indicated that the dominant adult cestode in bank vole was C. henttoneni and Mesocestoides spp. were the dominant larval cestodes. This study combined genetic and morphological methods to identify the cestodes infecting rodents in Poland. It confirmed the existence of P. kalelai in Poland, suggesting that previously reported Paranoplocephala spp., identified by morphological characters, may have corresponded to this molecularly identified species. Our study also highlighted gaps in genetic databases that currently still do not allow precise species identification.

The pathology of schistosomiasis mansoni, a neglected tropical disease of great clinical and socioeconomic importance, results from the parasite eggs that become trapped in host tissues, particularly in the liver and intestines. Continuous antigenic stimulation from these eggs leads to recruitment of inflammatory cells to the sites of infection with formation of periovular granulomas. These complex structures have variable size and composition and are the most striking histopathological feature of schistosomiasis mansoni. However, evaluation of granulomas by conventional microscopy methods is time-consuming and limited, especially in large-scale studies. Here, we used high resolution Whole Slide Imaging (WSI), which allows fast scanning of entire histological slides, and multiple morphometric evaluations, to assess the granulomatous response elicited in target organs (liver, small and large intestines) of two models of schistosomiasis mansoni. One of the advantages of WSI, also termed virtual microscopy, is that it generates images that simultaneously offer high resolution and a wide field of observation. By using a model of natural (Nectomys squamipes, a wild reservoir captured from endemic areas in Brazil) and experimental (Swiss mouse) infection with Schistosoma mansoni, we provided the first detailed WSI characterization of granulomas and other pathological aspects. WSI and quantitative analyses enabled a fast and reliable assessment of the number, evolutional types, frequency and areas of granulomas and inflammatory infiltrates and revealed that target organs are differentially impacted by inflammatory responses in the natural and experimental infections. Remarkably, high-resolution analysis of individual eosinophils, key cells elicited by this helminthic infection, showed a great difference in eosinophil numbers between the two infections. Moreover, features such as the intestinal egg path and confluent granulomas were uncovered. Thus, WSI may be a suitable tool for detailed and precise histological analysis of granulomas and other pathological aspects for clinical and research studies of schistosomiasis.

The reed vole, , is the only known natural non-permissive mammalian host of . However, the molecular mechanisms underlying this resistance have not been fully understood. We performed single-cell RNA-seq to investigate the peripheral blood mononuclear cells (PBMCs) responses to in and the susceptible host, Kunming mice. The samples were collected from uninfected animals (control group) and infected animals at 10 dpi. The major cell types identified in the PBMCs of the two species were monocytes, dendritic cells (DCs), T cells, NK cells, B cells, and erythrocytes. We observed that the population of monocytes decreased considerably in the bloodstream after infection in both and Kunming mice. However, differential gene expression analysis revealed that Cxcl9 was upregulated in monocytes after infection, while it was not detected as a DEG in Kunming mice. In addition, we observed that infection induced the upregulation of IL2 and IL4 in CD4+ T cells, and the expansion of the Th2 cell population. Regarding B cells, we did not observe any significant alteration among B cell subpopulations after infection compared to the control. However, DEG analysis revealed that Igha, Ighg1, and Ighg3 were upregulated in antibody secreting cells (ASCs) but not in Kunming mice. Together, our results suggest that both the innate and adaptive immune responses were activated in the peripheral blood of at 10 dpi, while their activation was not obvious in Kunming mice at the same moment.

Drivers of patterns of ectoparasitism in rodents in patchy Mojave Desert wetlands were investigated. A total of 1,571 ectoparasites in Mesostigmata, Trombidiformes, Siphonaptera and Ixodida were collected from 341 rodents ( Microtus californicus scirpensis , Mus musculus , Reithrodontomys megalotis , Peromyscus eremicus , and Neotoma lepida ) at eleven marshes. Trombiculids accounted for 82.5% of mites, followed by the mesostigmatid Ornithonyssus bacoti (17.5%), with chiggers predominating on voles and harvest mice. There were at least three genera of chiggers ( Eutrombicula alfreddugesi , Euschoengastia sp. novel, and Blankaartia sp. novel). Fleas included Orchopeas leucopus (90.3% of all fleas) and O . sexdentatus (9.7%), and ticks were the novel endemic Ixodes mojavensis (82.1% of ticks) and Dermacentor similis (17.9%). On all hosts and at all marshes, coverage-based rarefaction sampling was over 96%, indicating coverage sufficient for analysis. Dissimilarities in ectoparasite community structure were driven mainly by chiggers, I . mojavensis and O . leucopus . Northern marshes were dominated by chiggers; central marshes by I . mojavensis ; and southern marshes by O . leucopus . Primary determinants of ectoparasite community structure were host species, patch size, and parasite interspecific interactions. Host species richness and environmental factors such as patch distance and water and plant availability were not significantly associated with patterns of ectoparasitism. There were nine (60%) significant negative pairwise associations between ectoparasite taxa and no significant positive relationships. Ixodes mojavensis had the highest number of negative associations (with five other species), followed by chiggers and O . bacoti with two negative associations each. The study area is among the most arid in North America and supports numerous rare and endemic species in increasingly isolated wetland habitat patches; knowledge of ectoparasite ecology in this region identifies potential ectoparasite vectors, and provides information needed to design and implement programs to manage vector-borne diseases for purposes of wildlife conservation.