Transboundary and Emerging Diseases最新文献

Persistent infection with foot-and-mouth disease virus (FMDV) develops in over 50% of infected ruminants, presenting major obstacles to disease control and eradication. To clarify host immune correlates of FMDV persistence, we characterized systemic T- and B-cell responses, as well as mucosal responses in 15 vaccinated cattle following experimental FMDV challenge. The prevalence of FMDV persistence was 53.3%. While peripheral CD4⁺, CD8⁺, and γδ T-cell populations and their respective naïve/memory/effector subpopulations showed comparable frequencies between carriers and noncarriers, carriers exhibited significantly lower frequencies of IFN-γ-producing CD4⁺ and CD8⁺ T lymphocytes during early infection, indicating compromised cell-mediated immune responses essential for viral clearance. During persistent infection, carriers displayed a distinctive immunological profile characterized by significantly reduced peripheral B-cell frequencies and increased secretory IgA (sIgA) levels in oropharyngeal fluid (OPF), with comparable systemic antigen-specific and neutralizing antibody titers across groups throughout the study period. Notably, the combination of peripheral B cell frequencies with OPF sIgA levels demonstrated superior diagnostic specificity for vaccinated carrier identification compared to either indicator alone. Our findings highlight key immune features of FMDV persistence and propose a dual-biomarker approach for detecting asymptomatic carriers.

Porcine reproductive and respiratory syndrome virus (PRRSV) causes major economic losses in swine production worldwide, characterized by reproductive failure and respiratory disease. In China, the cocirculation of diverse strains drives ongoing viral evolution and the emergence of novel recombinants, posing serious challenges for disease control. Here, we report the isolation and characterization of a novel PRRSV strain (JS-YZ/2023) from a PRRS-suspected pig farm. Genomic analysis revealed a unique recombinant pattern between NADC30-like and HP-PRRSV lineages, distinct from previously reported recombinants. Experimental infection in piglets demonstrated significant pathogenicity, with persistent fever, severe anorexia, progressive weight loss, and pathological lesions including interstitial pneumonia with lymphocyte infiltration and marked disruption of intestinal villi. Notably, JS-YZ/2023 exhibited strong intestinal tropism, inducing a local cytokine storm in the small intestine and showing PRRSV-N protein antigen accumulation in crypt epithelial cells, as detected by immunohistochemistry. In addition, we successfully constructed a full-length infectious cDNA clone of JS-YZ/2023 incorporating a green fluorescent protein (GFP) reporter gene (rGFP-JS-YZ/2023). This engineered virus provides a valuable tool for investigating the pathogenic mechanisms of NADC30-like recombinants and facilitating vaccine development.

Duck Tembusu virus (DTMUV) is an emerging avian pathogenic flavivirus that causes neurological disorders and acute egg drop syndrome in ducks. Multiple genotypes of DTMUV, including clusters 1, 2, and 3, have been identified, and recent evidence suggests a correlation between viral genotype and disease severity. Our recent study demonstrated that DTMUV cluster 2.1 induces more severe clinical disease in ducks than cluster 1; however, the underlying mechanisms responsible for this difference remain unclear. Macrophages are key target cells for DTMUV replication and play a crucial role during the early stage of viral pathogenesis. Therefore, we hypothesized that distinct DTMUV genotypes may differentially regulate macrophage apoptosis, thereby influencing viral replication and modulating T lymphocyte responses. To investigate this, we developed an in vitro protocol to generate duck monocyte-derived macrophages (MDMs) and assessed their response to infection with two different DTMUV genotypes: cluster 1 and cluster 2.1. Our results showed that DTMUV cluster 1 infection significantly increased macrophage apoptosis and reduced cell viability. In contrast, DTMUV cluster 2.1-infected MDM exhibited higher cell viability and fewer apoptotic cells. Correspondingly, viral titers in supernatants from DTMUV cluster 2.1-infected cultures were significantly higher than those from cluster 1. Furthermore, culture with DTMUV cluster 2.1 resulted in enhanced proliferation of Th (CD3⁺CD4⁺BrdU⁺) and cytotoxic T lymphocyte (CTL; CD3⁺CD8⁺BrdU⁺) lymphocytes in both naïve peripheral blood mononuclear cells (PBMCs) and macrophage-peripheral blood lymphocytes (PBLs) co-culture systems. These results suggest that the inhibition of apoptosis in DTMUV cluster 2.1-infected macrophages may enhance antigen-specific T lymphocyte responses. Overall, our findings reveal a genotype-dependent mechanism by which DTMUV modulates macrophage survival, thereby influencing both viral replication and T cell activation, and ultimately contributing to genotype-specific immunopathogenesis. These insights deepen our understanding of DTMUV immunopathogenesis and may inform the development of more effective genotype-targeted vaccination and disease control strategies.

Enzootic nasal tumor virus (ENTV) is the etiological agent responsible for enzootic nasal adenocarcinoma (ENA), a chronic and contagious disease predominantly affecting sheep and goats. ENTV is classified into two distinct types: ENTV-1, which infects sheep, and ENTV-2, which infects goats. ENA has been globally reported in small ruminant-rearing regions, causing significant mortality and substantial economic impacts in affected flocks. There is currently no standardized detection method for ENA. In this study, we successfully generated a monoclonal antibody (mAb) and a polyclonal antibody (pAb) against the ENTV-2 capsid protein (p27), and identified the epitope of the mAb, which was found to be highly conserved among different ENTV-2 isolates. An antigen capture ELISA (acELISA) was then successfully developed using the mAb as the capture antibody and the pAb as the detection antibody to specifically detect p27 of ENTV-2 in nasal secretions. The cut-off value of the acELISA was determined to be 0.1052 by analyzing S/P values. The detection limit of this assay was 0.16 ng/mL of rp27 protein and equivalent to 844 copies/μL of ENTV-2 RNA. Specificity tests showed that the method had no cross-reaction with other prevalent small ruminant pathogens. The coincidence rates of the developed acELISA compared with western blotting and qRT-PCR assays were 98.95% (189/191) and 96.34% (184/191), respectively. Furthermore, the acELISA was applied to assess ENTV-2 in 1228 clinical nasal swab samples collected from seven provinces in China. The results demonstrated that the positivity rate varied between 0.00% and 28.21%. In conclusion, we successfully developed an acELISA with high specificity, sensitivity and reproducibility for the detection of ENTV-2 antigen. This high-throughput method for the detection of ENTV-2 represents a significant advancement in the field and may contribute to the prevention and control of ENTV-2.

Honey bees are dying due to a disease complex consisting of viruses, parasites, chemicals, nutritional deficiencies, and management problems. In the present study, pathogens and hemocytes were analyzed in honey bee hemolymph samples using third-generation sequencing and flow cytometry in three apiaries over a honey bee season. Using nanopore sequencing, several viruses and bacteria were identified, including the first reported presence in European honey bees of La Jolla virus and Apis rhabdovirus 5. Seasonal pathogen peaks were found, with spring and summer showing the highest loads which coincide with the main flowering periods. Notably, viral infections often did not persist after initial detection despite the continuous appearance of new bees, hinting at colony-wide transgenerational immunity. However, Hubei partiti-like virus 34 remained endemic in one apiary and was found even in young bees, raising concerns about its ability to evade the transgenerational immunity. Additionally, dynamics in total hemocyte counts (THCs) were identified. Understanding pathogen and immune factor dynamics throughout the bee season will help identify weak colonies and provide valuable insights into colony collapse and its prevention.

The emergence of the NADC30-like (Lineage1.8) porcine reproductive and respiratory syndrome virus (PRRSV) has accelerated the evolutionary divergence of PRRSV, causing significant economic losses to Chinese swine industry. In the present study, a novel Lineage 7 (L7/Prime Pac-like) PRRSV strain FJZHK-2025 was isolated in China. Full-length genome analysis revealed that FJZHK-2025 is closely related to L7 PRRSV and exhibits the highest nucleotide homology (96.4%–96.5%) with the L7 PRRSV reference strains. Notably, FJZHK-2025 contained a 36 amino acid (aa) insertion within Nsp2 that was identical to the Prime Pac PRRS vaccine strain. Phylogenetic analysis, recombination detection, and regional genomic homology comparisons revealed that FJZHK-2025 originated from inter-lineage recombination between L7 and lineage 1.8 (NADC30-like) PRRSV-2 strains. Animal challenge experiments showed that piglets infected with FJZHK-2025 developed a persistent high fever, displayed mild to moderate clinical symptoms and presented with moderate lung pathological lesions, indicating that the FJZHK-2025 strain is pathogenic to piglets. Therefore, it is critical to develop an effective strategy to prevent and control the spread of L7 PRRSV in China.

Tigecycline is considered a last-line therapeutic option for treating infections caused by multidrug-resistant (MDR) Gram-negative bacteria. The emergence of tmexCD1-toprJ1, a plasmid-mediated resistance-nodulation-division (RND) efflux pump gene cluster, poses a growing threat to tigecycline efficacy. While this gene cluster has primarily been identified in Klebsiella pneumoniae, its presence in other species remains poorly characterized. In this study, we investigated the occurrence, genetic features, resistance profile, and virulence potential of tmexCD-toprJ-positive Raoultella ornithinolytica isolates from a swine farm in China. A total of 126 samples were collected from a swine farm and screened for tigecycline-resistant isolates. Species identification was performed using MALDI-TOF MS, while PCR and sequencing were applied to detect tmexCD-toprJ. Antimicrobial susceptibility testing was assessed by agar and broth microdilution methods. Whole-genome sequencing with hybrid assembly provided insights into genetic organization. Conjugation and electroporation experiments were conducted to assess plasmid mobility, and virulence was assessed using the G. mellonella infection model. Six R. ornithinolytica isolates (4.76%) were identified as carrying tmexCD1-toprJ1 and exhibited multidrug resistance, including reduced susceptibility to tigecycline (minimal inhibitory concentrations [MICs] 4–16 mg/L). The resistance genes were located on highly similar IncFIB plasmids, which lacked typical conjugative elements. However, IS26 sequences flanking the gene cluster suggested potential for horizontal transfer. Phylogenetic analysis indicated possible clonal dissemination. All isolates carried chromosomally encoded virulence genes, and in vivo assays in G. mellonella revealed moderate to high pathogenicity. These findings expand the ecological distribution of tmexCD1-toprJ1 to R. ornithinolytica in livestock environments, underscoring the role of swine farm water systems as potential reservoirs. The coexistence of antimicrobial resistance and virulence determinants highlights the urgent need for strengthened surveillance and containment strategies to prevent further dissemination of tigecycline resistance.

The red-crowned crane (Grus japonensis) is one of the rarest cranes with a global population of less than 4000 individuals. The population of red-crowned crane could be influenced by health threats, including metabolic and infectious diseases. In the Wildlife Rescue Center of Suining County of Jiangsu Province, gouty arthritis (GA) was observed in all four red-crowned cranes since March 2024. A pooled fecal supernatant was first submitted to metagenomics sequencing for screening disease-associated pathogens. Enterobacteria phage phiEcoM-GJ1 was detected as the predominant virus while Escherichia coli and Aeromonas hydrophila were the dominated bacteria in the mixed fecal sample from red-crowned cranes. The 16S rRNA gene sequencing was further performed on both the mixed fecal sample and four individual samples, which showed that Escherichia-Shigella, Lactobacillus, and Enterococcus were the most abundant gut flora in both mixed and individual fecal samples. Furthermore, bacteria isolation and identification with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) confirmed that Escherichia coli was predominant (19/29 colonies, 65.52%) in the feces. Therefore, anti-uricacid and antibacteria treatments using plantain herb, doxycycline, Vitamin AD3 and multivitamin B were adopted, leading to a full behavioral recovery within 1 month. Overall, this case-based observational study provides first clue on the gut-joint axis in red-crowned cranes, supporting that gut microbiota dysbiosis is closely associated with GA in red-crowned cranes.

Pentatrichomonas hominis (P. hominis) has traditionally been regarded as a commensal or opportunistic inhabitant of the intestine. However, a growing number of studies have identified this protozoan as the sole pathogen in cases of intestinal disorders, including diarrhea, in both humans and animals, suggesting it may be a neglected zoonotic pathogen. To investigate the pathogenicity of P. hominis, we here systematically evaluated its effects on healthy immunocompetent BALB/c mice. Our findings revealed that infection with P. hominis induced injury in the large intestine, marked by inflammatory cell infiltration, epithelial cell necrosis, and intestinal mucosal sloughing. These pathological changes persisted and worsened throughout the 90-day observation period. Furthermore, infection appeared to disrupt goblet cell maturation or secretion, as indicated by increased periodic acid–Schiff (PAS) staining alongside decreased MUC2 production. Elevated levels of pro-inflammatory cytokines were also detected in both intestinal lavage fluid and serum. Finally, P. hominis infection altered the composition of the gut microbiota, increasing both its richness and diversity. Notably, it raised the relative abundance of the inflammation-associated genus Desulfovibrio, while reducing the abundance of beneficial bacteria, such as Akkermansia, Roseburia, and Lactobacillus. Collectively, these results provide compelling evidence that P. hominis acts as a zoonotic pathogen capable of inducing chronic intestinal inflammation. Therefore, the clinical significance of P. hominis infection warrants attention.