Infectious Bursal Disease (IBD) is an immunosuppressive viral disease caused by the Infectious Bursal Disease Virus (IBDV). It primarily affects young chickens, targeting the bursa of Fabricius, and poses significant economic threats to the poultry industry. To date, in addition to strict biosecurity measures, large-scale immunization is the optimal strategy and effective method to prevent and control IBDV infection. The emergence of new variant strains has made it more urgent to develop new vaccination strategies against IBD. Over the past few decades, many high-quality vaccines have been available on the market for the control of IBD, which can provide solid protection against the infections and diseases caused by classic IBDV to very virulent IBDV that had been continuously evolving and were endemic worldwide. However, viruses are not static. As they continue to circulate and evolve in the fields, novel antigenic variant viruses have been emerged in the last few years, and vaccines need to keep up with their pace. Collectively, this review summarizes the strategic evolution of IBDV vaccines from traditional methods to cutting-edge molecular platforms, providing promising strategies for developing the next-generation vaccines with higher safety, efficacy, and the ability to keep pace with the antigenic drift in IBDV.

Duck viral enteritis is a highly contagious and fatal disease of commercial waterfowl flocks. The disease occurs sporadically or epizootically in mainland China due to insufficient vaccinations. Early and rapid diagnosis is important for preventive intervention and the control of epizootic events in clinical settings. In this study, we generated two monoclonal antibodies (MAbs) that specifically recognized the duck enteritis virus (DEV) envelope glycoprotein B and tegument protein UL47, respectively. Using these MAbs, a colloidal gold-based immunochromatographic assay (ICA) was developed for the efficient detection of DEV antigens within 15 min. Our results showed that the detection limit of the developed ICA strip was 2.52 × 10³ TCID₅₀/mL for the virus infected cell culture suspension with no cross-reactivity with other pathogenic viruses commonly encountered in commercially raised waterfowl. Using samples from experimentally infected ducks, we demonstrated that the ICA detected the virus in cloacal swab samples on day three post-infection, demonstrating an 80% concordance with the PCR. For tissue homogenates from ducks succumbing to infection, the detection sensitivity was 100%. The efficient and specific detection by this ICA test provides a valuable, convenient, easy to use and rapid diagnostic tool for DVE under both laboratory and field conditions.

Pasteurella multocida is a zoonotic pathogen responsible for severe diseases in domestic and wild animals, posing threats to public health and causing substantial economic losses. Here, we describe a naturally attenuated P. multocida strain, FCF147, isolated from a mortality event involving black-necked swans (Cygnus melancoryphus) in a wildlife habitat in Fujian, China. Genomic and phylogenetic analyses revealed that FCF147 is evolutionarily distant from other P. multocida lineages and lacks the entire capsule gene cluster. Morphological observations revealed that the loss of the capsule exposed proteins on the bacterial surface. Phenotypic characterization demonstrated reduced capsule production, enhanced biofilm formation, and increased tolerance to heat stress. In vivo infection models confirmed that FCF147 exhibits markedly attenuated virulence in both mice and poultry. However, immunization with FCF147 did not provide effective protection against the challenge of a virulent capsular type A strain. These findings suggest that while FCF147 is poorly virulent, its ability to form robust biofilms and survive thermal stress may facilitate persistence in wild bird reservoirs and potential transmission routes. These findings offer novel insights into the ecological adaptation and pathogenic potential of naturally capsule-deficient P. multocida in wildlife, highlighting their relevance to wildlife surveillance and disease ecology.

Pasteurella multocida (Pm) is a zoonotic pathogen that poses a significant threat to animal health and causes substantial economic losses, further aggravated by rising tetracycline resistance. To restore the efficacy of tetracyclines to Pm, we evaluated the synergistic antibacterial activity of doxycycline combined with metformin, an FDA-approved antidiabetic agent. Among several non-antibiotic adjuvant candidates, metformin exhibited the most potent in vitro synergy with doxycycline, especially against capsular serogroup A strain (PmA). The combination demonstrated minimal cytotoxicity and hemolysis in both mammalian and avian cells and effectively inhibited resistance development under doxycycline pressure. At 50 mg/kg each, the combination of metformin and doxycycline significantly reduced mortality in mice and ducks acutely infected with PmA (from 100% to 60%), decreased pulmonary bacterial burdens, and alleviated tissue inflammation and damage. Mechanistic validation confirmed that metformin enhances membrane permeability in Pm without compromising membrane integrity, dissipates membrane potential, increases intracellular doxycycline accumulation, and downregulates the transcription of the tetracycline efflux gene tet(B). Morphological analyses further revealed pronounced membrane deformation and possible leakage of intracellular contents. These findings highlight metformin as a potent, low-toxicity tetracycline adjuvant with cross-species efficacy, offering a promising therapeutic approach for managing tetracycline-resistant Pm infections.

Riemerella anatipestifer (RA) is the primary causative agent of infectious serositis in ducks, causing significant economic losses. In this study, a rapid and visual loop-mediated isothermal amplification (LAMP) assay targeting the conserved region of the ompA gene was developed. Specific primers and a FAM-labeled probe were designed, and amplification products were visualized using phenol red-based colorimetric detection and a lateral flow dipstick (LFD) system. Among the five candidate primer sets, primer set 2 was selected because it showed the highest amplification efficiency and specificity, with no cross-reactivity detected against 12 common waterfowl pathogens. Under optimal conditions, the phenol red-based LAMP assay yielded visible results after incubation at 65 °C for 30 min, while the LAMP-LFD assay required an additional 3~5 min probe hybridization step, with detection limits of 7.76 × 10² copies/μL for the phenol red-based method and 7.76 × 10⁰ copies/μL for the LAMP-LFD method. Thirty clinical samples suspected of RA infection were analyzed using conventional PCR and the developed visual LAMP assays. The positive detection rates obtained with the LAMP-LFD and phenol red-based LAMP methods were 63.3% and 60%, respectively, showing high concordance with conventional PCR (56.7%). In conclusion, the LAMP assay integrating phenol red visualization and lateral flow dipstick detection is rapid, sensitive, and easy to perform, and both detection formats show potential for point-of-care or on-site applications, and can be used for the early diagnosis and detection of RA.

The rise of antibiotic-resistant bacterial infections necessitates alternative therapeutic strategies, such as phage therapy. This study investigates the potential of phage vB_PmuM_CFP3 (CFP3) as a therapeutic agent against avian cholera caused by Pasteurella multocida (P. multocida). Phage CFP3 was isolated from the feces and wastewater of a laying hen farm and underwent comprehensive biological characterization, including host range, lytic activity, and environmental stability. Transmission electron microscopy revealed CFP3′s typical myovirus morphology, with a head diameter of approximately 60 nm and a tail length of about 120 nm. CFP3 demonstrated high stability across a pH range of 4–10 and temperatures of 30–40 °C, making it suitable for oral administration in poultry. The phage exhibited a latent period of about 90 min and an optimal multiplicity of infection (MOI) of 1. Despite its narrow host range, with a lysis rate of 28.2% against avian-derived type A P. multocida, CFP3′s specificity minimizes impact on non-target bacteria. Whole-genome sequencing revealed a 32,696 bp linear double-stranded DNA genome with 46 predicted open reading frames (ORFs) and no tRNA or antibiotic resistance genes, enhancing its safety profile. Phylogenetic analysis indicated a close evolutionary relationship with Haemophilus phages HP1, HP2, and Pasteurella phage F108. While CFP3 shows promise as a precision therapeutic tool, further in vivo studies are required to evaluate its efficacy and safety. Future research should focus on expanding the phage library, optimizing phage mixtures, and exploring synergistic effects with other antimicrobial strategies. This study provides foundational data supporting the development of CFP3 as a viable alternative to antibiotics for controlling avian cholera.