This study aimed to gain insight into the pathogenesis of Mannheimia haemolytica (M. haemolytica)-associated polyserositis in veal calves. Necropsies were performed on 53 cases and 54 controls. Samples for bacteriological culture were collected from the peritoneum, pleura, pericardium (cases only), nasal cavity, palatine tonsils, bronchial mucosa, spleen, cerebellum, and retropharyngeal, bronchial, and mesenteric lymph nodes. 125 M. haemolytica isolates were sequenced. Calves were tested for bovine respiratory syncytial virus, parainfluenza virus, bovine coronavirus, M. haemolytica serotypes A1/A6 and A2, Histophilus somni, Pasteurella multocida, Mycoplasma bovis, influenza D virus, bovine herpesvirus-1 (qPCR) and bovine viral diarrhea virus (antigen ELISA). Pneumonia was diagnosed in 32.1% of cases and 24.1% of controls. In cases, M. haemolytica was detected in 98.1% of pleural, 94.3% of peritoneal, and 84.9% of pericardial samples, and in 54.7-84.9% of other tissues. Case-isolates were 94.2% serotype A2 and 5.8% A1. Controls showed lower M. haemolytica prevalence (maximum 22.2% in tonsils) and predominantly serotype A1 isolates (71.4%). Within individual cases, A2 isolates were clonal. Sequencing revealed between-serotype divergence (10,121 SNPs) but limited within-serotype variation (A2 ≤129; A1 ≤355 SNPs). Bronchial lymph node positivity for M. haemolytica was associated with peritoneal infection, and retropharyngeal lymph node positivity with pericardial infection. Cases were associated with age >56 days, higher body condition, German origin, and P. multocida-positive bronchial mucosa, but not with pneumonia. The findings support the hypothesis that virulent A2 strains enter circulation via the respiratory tract, causing septicemia and acute fatal polyserositis in calves in good condition, without necessarily inducing bronchopneumonia.

Feline panleukopenia virus (FPV) is a highly contagious pathogen that causes severe disease in cats; however, the mechanisms underlying FPV-induced inflammatory responses remain poorly understood. In this study, we investigated whether FPV infection induces macrophage pyroptosis and explored the underlying molecular mechanisms. FPV infection induced characteristic pyroptosis-associated changes in feline macrophages, including cellular swelling, plasma membrane disruption, increased lactate dehydrogenase (LDH) release, and intracellular reactive oxygen species (ROS) accumulation. Mechanistically, FPV infection activated the NLRP3 inflammasome and promoted Caspase-1 activation and gasdermin D N-terminal fragment (GSDMD-N) formation, indicating activation of the canonical pyroptotic pathway. Pharmacological inhibition of ROS with N-acetylcysteine (NAC), NLRP3 with MCC950, or Caspase-1 with YVAD-CHO significantly attenuated FPV-induced pyroptotic responses, confirming the involvement of the ROS/NLRP3/Caspase-1/GSDMD signaling axis. Furthermore, expression of the FPV capsid protein VP2 induced mitochondrial dysfunction and increased ROS production, suggesting that VP2 may contribute to oxidative stress during FPV infection. Collectively, these findings demonstrate that FPV induces macrophage pyroptosis through ROS-dependent NLRP3 inflammasome activation and identify a potential role of VP2 in regulating oxidative stress, providing new insights into the pathogenesis of FPV infection.

Anthropogenic land-use change is intensifying contact among wildlife, humans, and livestock in tropical ecosystems, increasing opportunities for cross-species transmission of infectious agents. Chimpanzees (Pan troglodytes schweinfurthii), owing to their close phylogenetic relationship with humans, are particularly susceptible to pathogen spillover. We performed a microbiome-based screening of potentially pathogenic bacteria in faecal samples from a chimpanzee-human-livestock interface in western Uganda using full-length 16S rRNA gene sequencing. A total of 21 bacterial genera, categorized as potentially pathogenic, were detected across all three studied host groups, from which several taxa of potential zoonotic or health relevance, including Clostridium perfringens, Salmonella enterica, Shigella spp., and Streptococcus suis, were detected in chimpanzees, humans, and goats. Our findings indicate an overlap in bacterial taxa across the interface. The relative abundance of potentially pathogenic bacterial taxa was descriptively lower in chimpanzees than in humans and livestock, but carried both enteric and respiratory bacterial species previously associated with disease outbreaks in captive and wild populations. These findings support integrating bacterial monitoring into conservation-oriented One Health frameworks.

Y. enterocolitica and Y. pseudotuberculosis are the causative agents of yersiniosis - zoonosis important for public health. The aim of this study was to detect the presence of Y. enterocolitica and Y. pseudotuberculosis in tundra reindeer, European mouflons and Shetland ponies, determine the bioserotype and genotype of the isolated strains, and assess their susceptibility to antimicrobial agents. To the authors' knowledge, this is the first study in world literature on the occurrence and characteristics of Y. enterocolitica strains in Shetland ponies. Five molecularly confirmed strains of Y. enterocolitica were isolated from 7 Shetland ponies (71.4%) and one from 9 European mouflons (11.1%). Y. enterocolitica was not isolated from tundra reindeer and Y. pseudotuberculosis was not isolated from any of the tested species. All Y. enterocolitica strains belonged to biotype 1 A and were ystB-positive. Strains isolated from Shetland ponies were classified as genotype G1, while strain isolated from a European mouflon was defined as genotype G3. Two of the strains isolated from Shetland ponies showed resistance to five antimicrobial agents, another two strains were resistant to six chemotherapeutic agents and the last two strains - one from Shetland pony and one from European mouflon, showed resistance to seven chemotherapeutic agents. All strains were susceptible only to ciprofloxacin. The results of this study showed that ystB-positive, multidrug resistant Y. enterocolitica strains are present in Shetland ponies and direct contact of children and adults with these animals may pose a potential threat.

Infectious bursal disease virus (IBDV) infection still severely threatens the poultry industry, which needs more effective prevention and control measures. The tripartite motif proteins (TRIMs) play vital regulatory roles on virus replication and may be identified as potential targets. Therefore, we first employed high-throughput sequencing to screen and identify avian-derived TRIMs associated with IBDV infection and found that IBDV infection dramatically increased the expression level of TRIM71 in vivo and in vitro. These findings suggest that TRIM71 might be closely related to IBDV infection. Subsequently, the overexpression experiment showed that TRIM71 promoted IBDV replication, while knockdown of TRIM71 significantly inhibited IBDV replication. Mechanistically, TRIM71 interacted with the structural proteins VP1 and VP3. Besides, truncation assay showed that the NHL domain was the key domain for the interaction between TRIM71 and VP1, VP3. The study is the first to reveal that the avian-derived TRIM71 acts as a host proviral factor to promote IBDV replication by interacting with VP1 and VP3 depending on the NHL domain. Collectively, these findings not only provides a new insight into the interaction between IBDV and the host, but also provides a potential target for the development of novel prevention and control strategies.

Myristic acid (MA), which is typically synthesized by various cellular processes as a physiological metabolite, has recently emerged as an endogenous immune regulator through N-myristoylation. This post-translational modification (PTM) has been shown to suppress STING-mediated production of type I interferon (IFN-I), leading to inhibition of antiviral innate immunity in mammals. Although a variety of mammalian viruses manipulate N-myristoylation for efficient replication and immune evasion, little is known about whether avian viruses also exploit MA-induced PTM for their benefits. For this purpose, our present study used primary chicken embryo fibroblasts (CEFs) as a model to analyze the effects of MA on the IFN-I production induced by the STING signaling pathway, and evaluated whether MA facilitates replication of Marek's disease virus (MDV) in vitro. In the context of cGAMP stimulation, the mRNA levels of both TBK1 and IRF7 were decreased by MA treatment, leading to suppression of IFN-β synthesis. Interestingly, the presence of MA significantly dampened the expression of IRF7 and IFN-β transcripts at 72 h post-infection with MDV. This inhibitory effect can be reversed by the N-myristoyltransferase inhibitor DDD85646. Noticeably, MA treatment significantly elevated the expression of MDV glycoprotein gC and led to larger viral plaques, indicating enhanced cell-to-cell spread; however, MDV replication was not improved in the presence of MA. Moreover, metabolomic analysis revealed that MDV infection caused significant alterations in multiple metabolic pathways, including glycerophospholipid metabolism, amino acid biosynthesis, and cofactor biosynthesis. In MDV-infected CEFs, MA exacerbated abnormalities of lipid metabolism and specifically activated inflammation-related pathways such as arachidonic acid metabolism and α-linolenic acid metabolism. Taken together, the present study provides a novel understanding on how MDV manipulates N-myristoylation to establish a favorable metabolic program for efficient cell-to-cell spread.

Avian orthoreovirus (ARV) is an important pathogen responsible for viral arthritis in poultry, causing significant economic losses to the poultry industry. In this study, an ARV strain designated QD25 was isolated from 28-day-old commercial broilers with tarsal joint swelling and paralysis in Shandong Province. The complete genome of QD25 was sequenced to enable comprehensive molecular characterization. Phylogenetic analysis based on the σC-encoding gene classified QD25 within genotype I subvariant, with 88.9-89.6% homology to strain ISR5225 and only 73.3% homology to vaccine strain S1133. Notably, phylogenetic analysis of the σNS non-structural protein encoded by the S4 segment positioned QD25 within the same clade as genotype III strains, suggesting that this strain has undergone a typical inter-genotype reassortment event involving σNS. Pathogenicity tests revealed that QD25 caused 40% mortality and significant growth suppression in specific pathogen-free chickens with severe histopathological lesions in multiple tissues. These results highlight the evolutionary features of ARV genetic reassortment. Moreover, the complete genome data offer robust evidence for strain tracing, molecular subtyping, and epidemiological monitoring, while also providing a theoretical basis for the rational prevention and control of ARV.

The presence of maternally derived antibodies (MDAs) can affect infection dynamics and the immune response in piglets during swine influenza A virus (swIAV) infection. This study aimed to investigate the impact of MDAs on swIAV infection characterized by the duration of swIAV RNA shedding, and serological antibody response in piglets under field conditions. The study was conducted in two Danish sow herds over a six-week period and included five sows with each four piglets in both herds. In addition to unknown previous natural swIAV exposure, sows had been vaccinated with Respiporc FLU3 in Herd 1 one month before study initiation and with Respiporc FLUpan in Herd 2 four months before study initiation. Blood and colostrum samples were collected from the sows on the day of farrowing, whereas nasal swabs and blood samples were collected twice and once weekly, respectively from the piglets. Viral load was estimated by reverse-transcriptase quantitative PCR and swIAV antibody levels in serum and colostrum were assessed by an swIAV-NP ELISA, serum neutralization and hemagglutinin inhibition -tests. Marked variation in antibody levels was observed between herds, sows, and piglets. swIAV RNA was detected in 6/20 piglets in Herd 1 and 17/20 in Herd 2. Due to the twice-weekly sampling interval, exact shedding durations could not be determined. Antibody titers at day 3 were not associated with protection against infection (p > 0.05). However, higher swIAV-NP titers prior to infection were negatively associated with shedding duration in Herd 2 (ρ = -0.67, p < 0.01). Higher swIAV-NP MDA levels were also associated with decreased serological responses after infection (ρ = -0.57, p < 0.05). Overall, MDAs showed limited protection against infection and suppressed adaptive antibody responses in a titer-dependent manner. These findings highlight substantial variability in passive immunity under field conditions and its importance for immune development in piglets.

Encephalomyocarditis virus (EMCV) is an important pathogen capable of infecting multiple host species and causing severe myocarditis and neurological dysfunction. EMCV infection induces endoplasmic reticulum (ER) stress, a process closely associated with disruption of intracellular calcium homeostasis. However, the regulatory role of calcium signaling in EMCV replication and the underlying host defense mechanisms remain to be fully elucidated. In this study, Western blotting, quantitative PCR, viral titration, and live‑cell calcium imaging were used to demonstrate how EMCV infection triggers ER calcium release, leading to elevated cytosolic Ca[2 +] levels, which in turn promotes viral proliferation. Further investigation revealed that the ER molecular chaperones protein disulfide-isomerase A3 (PDIA3) and calnexin (CANX) effectively counteract virus‑induced cytosolic calcium surge. Proteomic analysis identified fibroblast growth factor receptor 4 (FGFR4) as a key target commonly downregulated by CANX and PDIA3. Overexpression of PDIA3 or CANX suppresses FGFR4 expression at both the mRNA and protein levels, thereby establishing a negative feedback loop that prevents excessive calcium signaling. Of note, FGFR4 acts as a host antiviral restriction factor that becomes activated upon EMCV infection and suppresses viral replication through appropriately induced calcium release. In conclusion, EMCV hijacks ER calcium stores and elevates cytosolic calcium levels to create a microenvironment favorable for its own replication, whereas the host cell counteracts EMCV replication by targeting FGFR4 via PDIA3 and CANX to maintain calcium homeostasis. This study elucidates a novel antiviral mechanism centered on ER molecular chaperones and FGFR4, providing new insights into EMCV-host interactions.

Feline leukemia virus (FeLV) is a major pathogenic gammaretrovirus causing severe immunosuppression, hematopoietic disorders, and high mortality in cats worldwide. Currently, effective and well-tolerated long-term antiviral therapies for clinical FeLV infection remain limited. This study evaluated the anti-FeLV efficacy, molecular mechanism, pharmacokinetics, and safety of tenofovir alafenamide fumarate (TAF), a second-generation tenofovir prodrug. The antiviral activity of the earlier-generation prodrug tenofovir disoproxil fumarate (TDF) was also evaluated in vitro for comparison. Molecular docking and 100-ns molecular dynamics simulations revealed that tenofovir diphosphate (TFV-DP), the common active metabolite of TAF and TDF, stably binds to the active pocket of FeLV reverse transcriptase (FeLV-RT) via stable hydrogen bonds with a binding free energy of -50 kcal/mol, competitively blocking viral DNA synthesis. In F81 cells, both TAF and TDF showed dose-dependent anti-FeLV activity with EC50 values of 284.1 nM and 98.2 nM, respectively. TAF exhibited markedly lower cytotoxicity (CC50 = 1781.3 μM) than TDF (CC50 = 142.7 μM), with selectivity indices of 6272 and 1456, respectively. Given the poor bioavailability of the parent tenofovir and the safety limitations associated with TDF, TAF was selected for in vivo evaluation. In cats experimentally infected with FeLV, 45 days of oral TAF (1.5, 5, 15 mg/kg) reduced viral loads in lungs, lymph nodes, and spleen, and suppressed viremia and oronasal viral shedding in a dose-dependent manner. Pharmacokinetic analysis showed rapid oral absorption and dose-proportional exposure. Serum biochemistry confirmed no obvious hepatic or renal toxicity during the treatment period. Collectively, these findings provide preliminary evidence that TAF can suppress FeLV replication and viral shedding in experimentally infected cats and support further evaluation of TAF as a potential therapeutic option for FeLV infection.

Streptococcus suis is a critical zoonotic pathogen that poses a significant threat to global public health and the swine industry. However, comprehensive epidemiological and genomic data on S. suis in swine herds across southern China remain limited. In this study, we conducted a large-scale surveillance of S. suis isolates from pig farms in Guangxi, China. A total of 210 S. suis isolates were recovered from 2706 throat swabs (7.76%) collected across 12 representative pig farms. Antimicrobial susceptibility testing revealed high resistance rates to erythromycin, trimethoprim/sulfamethoxazole, and florfenicol, with widespread multidrug resistance (MDR) phenotypes. Whole-genome sequencing (WGS) uncovered high diversity in predicted cps types and sequence types (STs). Furthermore, 21 antimicrobial resistance genes associated with seven antimicrobial classes were identified, with resistance genotypes largely correlating with the observed phenotypes. Notably, closely related isolates with minimal single-nucleotide polymorphism (SNP) variations were identified across geographically distinct farms, indicating the clonal dissemination of specific strains within the region. Global phylogenetic analysis demonstrated that the Guangxi isolates clustered closely with both swine- and human-derived strains from public databases. Taken together, these findings highlight the high prevalence, genetic heterogeneity, and extensive MDR profiles of S. suis in southern China, underscoring the critical need for continuous surveillance and prudent antimicrobial use under a One Health framework.

The broader impact of small ruminant lentiviruses (SRLV) infections on overall sheep health remains insufficiently characterized, despite their recognized clinical importance. Τhis prospective longitudinal study evaluated the impact of SRLV infections on clinical health indicators and hematological profiles in 407 Chios and Lacaune dairy ewes from four intensive farms. Blood samples collected at pre-mating and pre-lambing over two consecutive lactation periods were tested for SRLV antibodies using ELISA and for viral DNA using real-time PCR. Individual health and welfare indicators were recorded including body condition score, foot and respiratory disorders, body abscesses, udder lesions and deformities, and wool quality. Hematological analyses quantified white blood cell, red blood cell and platelet counts and associated parameters. Mixed-effects binary and linear regression models were used to assess the associations of serological status, infection status (ELISA and PCR), and temporal infection and serological patterns with clinical and hematological outcomes. Ewes classified as PCR-positive but seronegative exhibited higher likelihood of lameness, arthritis, enlarged supramammary lymph nodes, udder skin and wart-like lesions. Also, infected animals demonstrated significantly lower white blood cell, lymphocyte, granulocyte, and monocyte counts, while the infected seronegative ewes had higher hemoglobin concentrations and reduced platelet distribution width, white blood cell, lymphocyte, and monocyte counts. These findings underscore the value of a prospective study design and the combined use of ELISA and PCR for elucidating the broader health consequences of SRLV infections. Further research is needed to explore the diagnostic utility of hematological profiles for the detection, staging, and monitoring of SRLV infections in dairy sheep.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne zoonosis caused by severe fever with thrombocytopenia syndrome virus (SFTSV) and is associated with high case-fatality rates in humans and cats. No vaccines or antiviral drugs are currently available for the prevention or treatment of feline SFTS. We hypothesized that some cats that recover from naturally acquired SFTS develop high neutralizing antibody titers and may serve as a source of convalescent serum for passive immunotherapy. We measured 80% plaque-reduction neutralization test (PRNT80) titers in convalescent sera from six human SFTS survivors and 14 cats that had recovered from naturally acquired SFTS, and then evaluated the therapeutic efficacy of convalescent cat serum in SFTSV-infected, interferon receptor-deficient AG129 mice. Some SFTS-recovered cats exhibited high PRNT80 titers. Passive administration of high-titer convalescent cat serum early after infection protected SFTSV-infected mice. A single dose given at 2 or 3 days post-infection completely protected mice, whereas treatment at 4 days post-infection resulted in 40% survival. In the repeated-dose experiment, early treatment was associated with lower blood viral RNA levels than controls at 6 dpi, and surviving mice also showed low viral RNA levels at 13 dpi. Sera from three additional SFTS-recovered cats also improved survival. Collectively, these findings indicate that some SFTS-recovered cats can develop high neutralizing antibody titers and that their sera can exert therapeutic effects in an SFTSV-infected mouse model, supporting further evaluation of passive immunotherapy as a treatment strategy for feline SFTS.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important swine pathogen without effective antiviral agents. Here, we constructed recombinant PRRSV reporter viruses expressing secreted NanoLuc luciferase (Nluc) based on the PRRSV TA-12 strain and established a quantitative antiviral screening platform. The selected rGNluc reporter virus exhibited stable replication characteristics and enabled rapid evaluation of PRRSV replication. Screening of a library of 146 gut microbial metabolites identified several antiviral candidates, among which lithocholic acid (LCA) exhibited potent inhibitory activity against PRRSV replication with a favorable selectivity index. LCA exhibited antiviral activity against multiple PRRSV-1 and PRRSV-2 strains, although susceptibility varied among strains, and primarily inhibited viral replication at post-entry stages. Mechanistic studies demonstrated that LCA reduced viral genomic RNA and subgenomic RNA synthesis and early viral protein expression, while its antiviral activity was independent of the bile acid receptors FXR and TGR5. Furthermore, cholesterol supplementation almost completely rescued PRRSV replication inhibited by LCA, suggesting the involvement of host cholesterol homeostasis in its antiviral activity. These findings establish a robust high-throughput screening (HTS) platform and identify LCA as a promising host-directed antiviral candidate.

Despite the widespread use of porcine circovirus type 2 (PCV2) vaccines in commercial swine production, evidence from randomized comparative field studies conducted under routine commercial production conditions remains limited. We conducted a prospective, randomized, blinded, parallel-group equivalence trial to evaluate whether a PCV2b whole-virus inactivated vaccine could achieve growth performance equivalent to that of two established commercial PCV2 vaccines under shared natural exposure. A total of 309 piglets were randomly allocated to three vaccination groups at 27 days of age and commingled throughout the study to minimize differences in management and infection pressure. Average daily gain (ADG) from 27 to 158 days of age was predefined as the primary endpoint and evaluated using a prespecified equivalence margin of ±35 g/day. Secondary outcomes included safety, mortality, morbidity, treatment burden, and longitudinal virological and serological responses. Following prespecified exclusions, 73, 77, and 75 pigs remained in Groups A, B, and C, respectively, for the primary analysis. The ANCOVA-adjusted difference was 6.2 g/day for Group A versus Group B (90% CI, -14.1-26.6) and -11.3 g/day for Group A versus Group C (90% CI, -31.7-9.2); both confidence intervals were entirely contained within the prespecified equivalence margin. No statistically significant between-group differences were detected in mortality, morbidity, treatment burden, or longitudinal PCV2 viremia. Serological responses differed at selected time points, but these differences were not accompanied by corresponding differences in growth, clinical, or virological outcomes. These findings demonstrate equivalent growth performance between the evaluated PCV2b whole-virus inactivated vaccine and each comparator under the conditions of this single-farm field trial.