Bovine respiratory disease complex (BRDC) is one of the primary causes of morbidity, mortality, and economic loss in cattle worldwide. Accurate and rapid identification of causative pathogenic agents is essential for effective disease management and control. In this study, a novel multiplex fluorescence-based quantitative polymerase chain reaction (qPCR) assay was developed for the simultaneous detection of eight major pathogens associated with BRDC. The targeted pathogens included the following: bovine viral diarrhea virus (BVDV), bovine parainfluenza virus type 3 (BPIV3), bovine respiratory syncytial virus (BRSV), bovine coronavirus (BcoV), Mycoplasma bovis (M.bovis), Pasteurella multocida (PM), Mannheimia haemolytica (MH), and infectious bovine rhinotracheitis virus (IBRV). The assay was rigorously optimized to ensure high specificity with no cross-reactivity among targets. The limit of detection (LOD) was determined to be as low as 5 copies per reaction for all target pathogens. The coefficient of variation (CVs) for both intra-assay and inter-assay measurements were consistently below 2%, demonstrating excellent reproducibility. To validate the clinical utility of the assay, a total of 1012 field samples were tested, including 504 nasal swabs from Farm A and 508 from Farm B in Jiangsu Province. BVDV, BcoV, PM, and MH were detected from Farm A, with a BVDV-positive rate of 21.63% (109/504), BcoV-positive rate of 26.79% (135/504), PM-positive rate of 28.77% (145/504), and MH-positive rate of 15.08% (76/504). Also, BcoV, PM, MH, and IBRV were detected from Farm B, with a BcoV-positive rate of 2.36% (12/508), PM-positive rate of 1.38% (7/508), MH-positive rate of 14.76% (75/508), and IBRV-positive rate of 5.51% (28/508). Notably, a significant proportion of samples showed evidence of mixed infections, underscoring the complexity of BRDC etiology and the importance of a multiplex diagnostic approach. In conclusion, the developed multiplex qPCR assay provides a reliable, rapid, and cost-effective tool for simultaneous detection of multiple BRDC-associated pathogens, which will hold great promise for enhancing disease surveillance, early diagnosis, and targeted intervention strategies, ultimately contributing to improved BRDC management and cattle health outcomes.

Feline infectious peritonitis (FIP) is a highly lethal disease caused by feline infectious peritonitis virus (FIPV), which poses significant diagnostic challenges in clinical practice. FIPV is divided into two serotypes (serotype I and serotype II) based on distinct serological responses driven by substantial sequence divergence in the spike (S) protein. Serotype I predominates in Europe and North America, whereas serotype II is more common in Asia. In this study, we developed a triplex reverse transcription quantitative PCR (RT-qPCR) assay for simultaneous detection and serotyping of FIPV. Primers and TaqMan probes were designed to target the conserved nucleocapsid (N) gene and serotype-specific regions within the S gene. After systematic optimization of reaction conditions, the final assay employed an annealing temperature of 64 °C and optimized primer–probe concentrations. The assay exhibited excellent linearity (R² > 0.99 for all targets), with amplification efficiencies ranging from 97.39% to 109.97%. No cross-reactivity was observed with other common feline pathogens, confirming high specificity. The limit of detection was as low as 0.5 copies/µL, and intra-assay repeatability showed coefficients of variation below 2.1%. Clinical validation using 63 feline samples revealed an overall FIPV positivity rate of 21.63%, with serotype II (17.46%) markedly more prevalent than serotype I (3.17%). Collectively, this triplex RT-qPCR assay demonstrates high sensitivity, exceptional specificity, and robust reproducibility, making it a valuable tool for rapid clinical diagnosis through the simultaneous detection of feline coronavirus (FCoV) and serotyping of FIPV.

African swine fever (ASF) is a highly lethal viral disease of pigs caused by the African swine fever virus (ASFV). The mortality rate is nearly 100%. Currently, it is known that the ASFV has a complex structure, and its genome encodes various immune escape proteins. However, the pathogenic mechanism of ASFV remains to be studied. This study found that ASFV pD345L significantly inhibits the activation of the ISRE promoter triggered by interferon (IFN) β and the production of downstream IFN-stimulated genes (ISG). We further reveal that pD345L may degrade STAT1 via the autophagy pathway and impede its nuclear translocation; this inhibitory effect is closely associated with its exonuclease activity. Our research results have clarified the impact of ASFV pD345L on the JAK/STAT signaling pathway, expanding our understanding of the inhibitory effect of ASFV-encoded proteins on the host’s innate immunity, and to some extent, contributing to the development of an African swine fever vaccine.