Infectious laryngotracheitis (ILT) and Newcastle disease (ND) are two important avian diseases that have caused huge economic losses to the poultry industry worldwide. Newcastle disease virus (NDV) has been used as a vector in the development of vaccines and gene delivery. In the present study, we generated a thermostable recombinant NDV (rNDV) expressing the glycoprotein gB (gB) of infectious laryngotracheitis virus (ITLV) based on the full-length cDNA clone of the thermostable TS09-C strain. This thermostable rNDV, named rTS-gB, displayed similar thermostability, growth kinetics, and pathogenicity compared with the parental TS09-C virus. The immunization data showed that rTS-gB induced effective ILTV- and NDV-specific antibody responses and conferred immunization protection against ILTV challenge in chickens. The efficacy of rTS-gB in alleviating clinical signs was similar to that of the commercial attenuated ILTV K317 strain. Furthermore, rTS-gB could significantly reduce viral shedding in cloacal and tracheal samples. Our study suggested that the rNDV strain rTS-gB is a thermostable, safe, and highly efficient vaccine candidate against ILT and ND.

Novel goose parvovirus (NGPV), a genetic variant of goose parvovirus, has been spreading throughout China since 2015 and mainly infects ducklings with the symptoms of growth retardation, beak atrophy, and protruding tongue, leading to huge economic losses every year. A safe and effective vaccine is urgently needed to control NGPV infection. In this study, virus-like particles (VLPs) of NPGV were assembled and evaluated for their immunogenicity. The VP2 protein of NGPV was expressed in Spodoptera frugiperda insect cells using baculovirus as vector. The VP2 protein was efficiently expressed in the nucleus of insect cells, and the particles with a circular or hexagonal shape and a diameter of approximately 30 nm, similar to the NGPV virion, were observed using transmission electron microscopy (TEM). The purified particles were confirmed to be composed of VP2 using western blot and TEM, indicating that the VLPs of NGPV were successfully assembled. Furthermore, the immunogenicity of the VLPs of NGPV was evaluated in Cherry Valley ducks. The level of NGPV serum antibodies increased significantly at 1–4 weeks post-immunization. No clinical symptoms or deaths of ducks occurred in all groups after being challenged with NGPV at 4 weeks post-immunization. There was no viral shedding in the immunized group. However, viral shedding was detected at 3–7 days post-challenge in the non-immunized group. Moreover, VLPs can protect ducks from histopathological lesions caused by NGPV and significantly reduce viral load in tissue at 5 days post-challenge. Based on these findings, NGPV VLPs are promising candidates for vaccines against NGPV.

Fowl adenovirus (FAdV) serotype 4, recognized as the causative agent of hydropericardium syndrome (HPS) in chickens, causes substantial economic losses in poultry farming. To develop a simple, rapid, and reliable diagnostic method for the timely detection of FAdV-4 nucleic acid, we integrated the CRISPR/Cas12a system with recombinase-aided amplification (RAA). This approach enables visual detection of FAdV-4 with a sensitivity of one genome copy. The results can be obtained within 40 to 50 min without the need for complex instrumentation, making it ideal for remote field applications. Using this method, we investigated the prevalence of FAdV-4 in both common farm poultry and wild birds. Our results indicated that the FAdV-4-positive rate in wild birds was 51.19%, suggesting that wild birds may serve as specific reservoirs for this virus. In summary, we present a sensitive, swift, accurate, and inexpensive detection method for FAdV-4, along with an investigation of its epidemic situation in birds. Our study advances the detection and epidemiological understanding of FAdV-4 transmission among farm poultry and wild birds.

Diarrhea and impaired intestinal development are major constraints in newly hatched domestic pigeons raised for meat production, leading to reduced growth performance and increased reliance on antimicrobial interventions. Cecropin AD (CAD) is a broad-spectrum antimicrobial peptide with potential activity against bacterial pathogens and may represent an alternative strategy for improving intestinal health in poultry. In this study, we evaluated the safety and biological effects of a recombinant Newcastle disease virus (NDV) expressing CAD (rTS-CAD₃) in one-day-old domestic pigeons. Pigeons were inoculated with rTS-CAD₃, parental TS09-C, or PBS and monitored for growth performance, diarrhea incidence, viral RNA persistence, inflammatory responses, intestinal bacterial abundance, gut microbiota composition, intestinal morphology, and epithelial barrier function. rTS-CAD₃ caused no mortality, detected only transient viral RNA, and did not induce excessive inflammatory responses. Compared with TS09-C and PBS controls, rTS-CAD₃ significantly increased body weight gain and average daily gain while reducing diarrhea incidence. Importantly, rTS-CAD₃ decreased intestinal Escherichia coli abundance, reshaped the gut microbiota by reducing Proteobacteria and Escherichia–Shigella while increasing Firmicutes and Lactobacillus, improved villus height and the villus-to-crypt ratio, and enhanced occludin expression. These findings demonstrate that NDV-vectored CAD delivery can reduce intestinal bacterial burden, increase occludin expression, and alleviate diarrhea in domestic pigeons. The rTS-CAD₃ represents a promising antimicrobial peptide-based strategy for reducing spontaneous diarrhea and dependence on conventional antibiotics in poultry production.

Vaccination remains the core strategy for the prevention and control of Newcastle disease (ND). The inherent thermosensitivity of traditional Newcastle disease virus (NDV) vaccines imposes major limitations on their transportation, storage, and field application. To address these challenges, a novel liquid, thermostable, live ND vaccine was developed in the present study. Firstly, Tris/HCl buffer at near-neutral pH was identified as the optimal basic buffer system. On this basis, further screening and formulation optimization of vaccine stabilizers were conducted, and NDV strains with excellent thermal stability were used to verify the stability-conferring properties of the developed stabilizer. The results showed that the formulation composed of 0.5% gelatin, 4% trehalose, 0.1% L-glutamic acid, and 0.5% thiourea was confirmed as the optimal stabilizer for ND liquid vaccines. This formulation maintained the stable storage of the tested NDV for 12 months at 4 °C and exhibited promising stability for 30 days at 25 °C, marking a significant advancement toward development thermostable NDV vaccines that are independent of a continuous cold chain. More importantly, the liquid vaccine stored at 4 °C for 12 months still induced high levels of NDV-specific antibodies in specific pathogen-free chicks and provided 100% protective efficacy against challenge with virulent NDV. In conclusion, the liquid vaccine stabilizer developed in this study not only significantly enhanced the thermostability of the vaccine but also effectively maintained its immunogenicity, thereby providing an important theoretical basis for the research and development of liquid ND vaccines.