Muscovy duck parvovirus (MDPV) causes high mortality and morbidity in Muscovy ducks, with the pathogenesis of the virus still unknown in many respects. Specific MDPV detection is often rife with false positive results because of high identity at the genomic nucleotide level and antigenic similarity with goose parvovirus (GPV). The objective of this study was to develop a sensitive, highly specific, and repeatable TaqMan-based real-time PCR (qPCR) assay for facilitating the molecular detection of MDPV. The specific primers and probe were designed based on the conserved regions within MDPVs, but there was a variation in GPVs of the nonstructural (NS) genes after genetic comparison. After the optimization of qPCR conditions, the detection limit of this qPCR assay was 29.7 copies/μl. The assay was highly specific for the detection of MDPV, and no cross-reactivity was observed with other non-targeted duck-derived pathogens. Intra- and inter-assay variability was less than 2.21%, means a high degree of repeatability. The diagnostic applicability of the qPCR assay was proven that MDPV-positive can be found in cloacal swabs samples, Muscovy duck embryos and newly hatched Muscovy ducklings. Our data provided incidents that MDPV could be possible vertically transmitted from breeder Muscovy ducks to Muscovy ducklings. The developed qPCR assay in the study could be a reliable and specific tool for epidemiological surveillance and pathogenesis studies of MDPV.

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.

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.