Despite use of aMPV vaccines, clinical signs of disease caused by aMPV infection with field strains were widely reported in poultry production in Poland.The strains detected formed a distinct cluster of "Polish field strains".Two complete aMPV-B genomes revealed several non-synonymous mutations, especially in G and SH genes, that may account for the poor protection provided by the vaccines.Phylogenetic analysis of two Polish complete genomes revealed a significant genetic distance from available aMPV-B strains.

West Nile virus (WNV) is one of the most widely distributed zoonotic arthropod-borne viruses in the world and has been identified as the cause of potentially fatal disease in birds. While the pathomorphology and virus distribution in birds are well documented for WNV lineage 1 (WNV-1) epizootics in North America, few (histo-)pathological and immunohistochemical studies are available for Europe, where WNV lineage 2 (WNV-2) is co-circulating with WNV-1.WNV-2 infected dead birds were evaluated (histo-)pathologically at the German regional veterinary laboratories and academic pathological institutes. Immunohistochemical labelling (IHC) with an in-house rabbit anti-WNV polyclonal antibody (OM8) and subsequent evaluation of IHC signal distribution were performed at the National Reference Laboratory.In total, tissues of 54 birds from 32 different species including first-time descriptions in endangered avian taxa were analysed. Gross and histopathological findings aligned well with previous reports of avian WNV disease and the heart was once more confirmed as a reliable target organ for diagnostics. However, the frequent identification of WNV antigen (Ag) in enteric ganglial neurons and glial cells in several bird species as well as signs of prolonged disease duration in corvids contrasted with earlier findings on the North American continent.In conclusion, this study broadens the range of avian taxa, for which information on pathomorphology and distribution of viral Ag associated with fatal WNV disease is available, and will facilitate diagnostics in the field. Furthermore, some of the described findings differed from the available literature suggesting deviations in the pathogenesis of locally circulating WNV-2 strains.

The increasing prevalence of antigenic variations and genetic reassortments of Infectious Bursal Disease virus (IBDV) across various global regions, causing subclinical infections, poses a significant threat to the poultry industry, leading to substantial losses. In the current study, the protective efficacy of recombinant trivalent vaccine rHVT + IBD + H5, administered once at 1-day old (DO) in the hatchery was assessed against challenge with the most recent circulating novel variant IBD (nVarIBDV), A2dB1b, Egyptian isolate (IBD/EGY/F1335/2023) in commercial broiler, and specific pathogen free (SPF) chickens at 28 DO. A total of 210, commercial broilers and 120 SPF chicks, housed at BSL-3 conditions, were divided into 11 equal groups (Broilers, G1-G7, and SPF G8-G11, n = 30/group). The bursa/body weight ratio (BBR) and bursa/body weight index (BBI) scores calculated at 4-, 7-, 10-, and 14-days post-infection (DPC) revealed significantly higher scores in the vaccinated challenged broiler groups (especially G4) and in the vaccinated challenged SPF group (G8) as compared to their control non-vaccinated challenged groups, G2, G5 and G9, respectively. Additionally, the histopathological and immunohistochemical examinations indicated significantly higher protection in the vaccinated-challenged broilers (G1 and G4) and SPF (G8) groups in comparison to their controls. Overall, this study demonstrated higher protective efficacy of rHVT + IBD + H5 hatchery vaccination against Egyptian nVArIBDV, A2dB1b, especially in the broiler chickens G4 that had specific MDA.

Viral diseases are a major cause of economic losses in the poultry industry. Among these is infectious bursal disease (IBD), which poses a threat to global poultry production. The epidemiology of IBD is changing, while very virulent IBDV (vvIBDV) remains endemic and represents the dominant clinical threat in regions such as Africa and parts of South America, the regional transition towards novel variants (nVarIBDVs) and reassortants (A3B1) is particularly pronounced in Asian and European poultry production, respectively. This review synthesises global IBD epidemiological data reported up to December 2025 and analyses the evolution of molecular genogrouping and fitness. Ongoing IBDV evolution is accelerating, with Asia becoming the epicentre of nVarIBDV (genogroup A2d), which circumvents maternally derived antibodies (MDA) and classical vaccine protection. In Europe, the A3B1 reassortant has become the dominant field IBDV strain. The review highlights a nomenclature conflict regarding the A9 designation, which currently refers to both attenuated strain and pathogenic variant from Portugal. Considering the 9% divergence threshold, the attenuated IBDV strain should be returned to the A1 genogroup lineage "b" (A1b), while A9 denotes Portuguese variants. Furthermore, phylogenetic analysis reveals that the evolution of segment B (VP1) is independent of segment A (VP2), necessitating a bi-segmental approach. The rapid antigenic drift in VP2, combined with the crucial role of the conserved segment B and the RNA-dependent RNA polymerase (RdRp) in viral pathogenicity, necessitates a shift to a standardised dual-segment phylogenetic classification system (A#xB#y binomial nomenclature) for effective global surveillance.

The GVI-1 genotype of infectious bronchitis virus (IBV) has become increasingly prevalent in Asia. In this study, a highly pathogenic GVI-1 strain (GVI-1-WT) was attenuated by 110 serial passages in embryonated chicken eggs, yielding an attenuated strain (GVI-1-E110). Comparative genomic analysis identified two amino acid substitutions, S523I, Q653R and a nine-amino-acid truncation in the spike (S) protein. To evaluate the contribution of the two point mutations to virulence attenuation, recombinant viruses carrying Q653R and S523I substitutions were generated using a reverse genetics system based on the GVI-1-WT strain as the backbone. Their replication and pathogenicity were assessed in embryonated eggs and specific pathogen-free chickens. The Q653R substitution was associated with reduced viral replication in embryonated chicken eggs and pathogenicity in specific pathogen-free chickens, whereas the S523I mutation alone showed a limited effect but enhanced attenuation when combined with Q653R. However, the attenuation phenotype of the recombinant viruses did not fully recapitulate that of the passaged strain GVI-1-E110, suggesting that additional mutations, including the identified truncation and mutations in replicase-associated genes outside the S protein, may also contribute to virulence attenuation. This study indicates that spike protein mutations are involved in the attenuation of GVI-1 IBV strains, and provides insights into the molecular basis of IBV attenuation during serial passage. Further studies are required to elucidate the underlying mechanisms and to evaluate their potential relevance for vaccine development.

APEC Hcp2b protein translocates into HD11 cells and induces significant cytotoxicity.Hcp2b elicits incomplete autophagy, characterized by blocked autophagic flux.Proteomic analysis demonstrated Hcp2b impairs lysosomes, blocking autophagy.

Four atypical S. Infantis variants differ in the infection dynamics in broilers.Non-motile S. Infantis variants regain motility following host passage.

The H9N2 subtype of avian influenza A virus has been endemic in poultry populations across Asia and the Middle East, posing ongoing economic and public health concerns. Since their initial detection in Pakistan in the 1990s, H9N2 viruses have caused repeated outbreaks in commercial poultry, leading to substantial economic losses and raising concerns about zoonotic transmission. To characterize the recent genetic evolution and zoonotic potential of circulating strains, five H9N2 isolates were obtained from poultry in Pakistan between January and March 2023. Phylogenetic analysis of the haemagglutinin gene revealed that all five isolates belong to the G5.3.2, formerly known as B2, sub-lineage of the G1 Eurasian lineage, in accordance with the revised global classification system for H9 viruses. Comparative genomic analysis confirmed that all eight gene segments were closely related to previously reported Pakistani strains, with no evidence of recent reassortment, suggesting localized persistence and ongoing genetic drift. Notably, several mammalian-adaptive mutations were identified in internal gene segments of the isolates, suggesting a potential risk of cross-species transmission. In addition, all five isolates exhibited dual receptor-binding characteristics, recognizing both α2,3-linked (avian-type) and α2,6-linked (human-type) sialic acid glycans, with a stronger affinity for α2,6-linked glycans. These findings underscore the need for continuous surveillance and risk assessment of H9N2 viruses circulating in Pakistan.

First serological survey on rotavirus A (RVA) in domestic and wild pigeons.RVA widely distributed (∼80%) in domestic and feral pigeons but not in wild common wood pigeons.Almost all adult domestic pigeons (98.1%) possess anti-RVA antibodies.Antibody titres in vaccinated juvenile pigeons are similar to reconvalescents and adults.

The immunosuppressive effects of the infectious bursal disease virus (IBDV), together with its ongoing genome evolution, still represent a major challenge for poultry farmers. This study characterized a novel reassortant IBDV strain, named UK2020, which was isolated in broiler farms from the United Kingdom in 2020 and has now spread across Europe. The phylogenetic analysis revealed that UK2020 belongs to the genotype A3B1, with segment A derived from a very virulent strain (vvIBDV) and segment B from a classical attenuated virus. The pathogenicity studies conducted in both specific-pathogen-free and commercial broiler chickens, with and without maternally-derived antibodies (MDAs), demonstrated that UK2020 caused subclinical infections. These infections resulted in splenomegaly, moderate inflammation of the bursa with histopathological changes, such as lymphoid depletion, inflammatory cell infiltration and plical oedema, and a significant humoral response, despite the absence of clinical signs. The efficacy of a commercial IBD immune complex (Icx) vaccine was also evaluated. Vaccinated birds showed significantly higher antibody titres and reduced lymphoid organ damage compared to mock-vaccinated controls. These results highlight the need for continuous field surveillance to monitor the circulation and impact of reassortant IBDV strains under the current control programmes. The complete sequencing of segments A and B is essential for accurate detection and classification of such strains. The use of Icx vaccines may contribute to mitigating bursal and splenic lesions associated with A3B1 infections like UK2020, especially in flocks with variable MDA levels.

Combined supplementation of benzoic acid (BA) and oregano essential oil (OEO) performed better than anticoccidial drugs.BA and OEO reduced Eimeria infectivity and faecal scores more than salinomycin in treated chickens.BA and OEO supplementation ameliorated gut structural damage caused by Eimeria infection.BA and OEO upregulated zonula occludens-1 and claudin-1 gene expression in the intestine.

In the present study, the virulence of two Mycoplasma synoviae (MS) field isolates was evaluated in specific pathogen-free (SPF) and modern-day commercial broilers. Both MS isolates belonged to Multilocus Sequence Typing (MLST) clonal complex (STCplx) 56, the most prevalent STCplx isolated from the respiratory tract of Dutch commercial poultry in the last two decades. Additionally, in this study, a well-defined histologic air sac lesion (ASL) score was combined with an in situ hybridization (ISH) test to further study the cellular reaction in the air sacs and tracheal tissue. Birds were challenged intratracheally with MS at 5 days of age. The synergistic effect of a mild infectious bronchitis virus (IBV) H120 vaccine given 5 days prior to MS challenge was also evaluated in the commercial broilers. The clinical impact of the MS strains was comparable to earlier studies with older isolates, as were the synergistic effects of IBV. The present study demonstrated a difference in effect on growth, macroscopic air sac lesions (mASL) and histologic (h)ASL between the two broiler types. A relevant new finding with economic impact for the poultry industry was that ascites was observed related to both isolates; however, the mechanisms underlying MS-associated ascites require further investigation. The hASL, combined with the MS ISH assay, revealed differences in cellular reaction in the air sacs compared to the trachea, explaining the lower MS detection rate in the air sacs in the chronic phase of MS infection. This also emphasizes the risk of misdiagnosing MS-related airsacculitis in broilers.

ABSTRACTEnterococcus cecorum lesions include bacterial chondronecrosis with osteomyelitis (BCO) of the femur and free thoracic vertebrae. Mechanical stress can be applied using wire-obstacle models and has been suggested as a predisposing factor for BCO. Here, the effect of a wire-obstacle model was assessed following inoculation with E. cecorum. Two groups SPF broilers were orally inoculated at day of hatch with 10[7.6] colony-forming units of E. cecorum in peptone physiological saline (PPS) per bird. In one group, a wire-obstacle was placed between the feed and water. This obstacle had a 66% slope, a height of 30 cm and was covered with iron mesh. Additionally, two control groups were inoculated with PPS, with an obstacle placed in one group. At 3, 7, 10, 14, 21, 28, 35, and 42 days post-inoculation, 20 birds from the E. cecorum-inoculated groups and eight birds from the PPS-inoculated groups were euthanized and macroscopically examined. Samples from spleen, femur and free thoracic vertebrae were subjected to bacteriological examination. No significant differences in the number of birds with typical lesions or positive reisolations were observed between the E. cecorum-inoculated groups with and without the obstacle. Typical lesions were observed in 58 of the 320 inoculated birds, with pericarditis being the most common lesion (46 birds). Femoral BCO was observed in seven birds. E. cecorum was reisolated in 45 of the 320 inoculated birds and in none of the controls. A wire-obstacle model does not predispose for BCO in an E. cecorum model using SPF broilers.

Anatid herpesvirus 1 (AnHV-1) is still a significant limiting factor in the waterfowl industry, and there is a clear demand for field-applicable serodiagnostic assays that are robust, sensitive and reproducible. In this report, we designed and conducted a comprehensive comparative evaluation of whole virus or recombinant glycoprotein C (gC), glycoprotein D (gD) alone or a mixture of gC-gD ELISA, to determine which one had the better diagnostic performance. The recombinant proteins were produced, purified, and optimized for use in indirect ELISA, and subsequent validation was carried out using a set of 120 field serum samples. Receiver operating characteristic (ROC) curve analysis demonstrated that the combined gC-gD ELISA exhibited an almost perfect diagnostic performance (AUC = 0.9925), and high sensitivity (93%) and specificity (95%), surpassing those of two antigen-based assays and the whole virus assay. Although both gC ELISA (high sensitivity 95% but moderate specificity 80%) and gD ELISA (outstanding sensitivity 99%, but lower overall accuracy: AUC = 0.9150) performed well, the sensitivity of the whole virus ELISA was lower (87%) with marked variation. In particular, intra-assay precision analysis showed a significant decrease in the coefficient of variation for the gC-gD ELISA (∼4%) compared with the gD (∼15%), gC (∼20%) and whole virus (∼40%) formats, indicating the highest reproducibility of the gC-gD ELISA. Taken together, these results demonstrate that the gC-gD ELISA provides a novel and robust tool for high-throughput AnHV-1 serosurveillance, which represents a major breakthrough in terms of economy when compared to traditional whole virus-based ELISAs for large field applications.

Five vaccination-challenge trials were performed with a live attenuated vaccine which includes an infectious bronchitis virus (IBV) Massachusetts strain (H120, GI-1), an IBV Q1 strain (BNF 28/86, GI-16), and a Newcastle disease virus (NDV) cloned strain. The efficacy of the vaccine was tested in maternally-derived antibody-positive (MDA+) commercial layers against challenge with IBV M41, 793B, D388(QX) or Q1 challenge virus. The efficacy of the vaccine was also tested in SPF layers against challenge with IBV M41, D388(QX) or Variant 2 challenge virus. The vaccine was applied at day of hatch, and all challenges were performed at 3 weeks of age. At 5 days post-challenge, the ciliary activity of tracheal explants was examined to determine the level of protection. The level of protection induced by the vaccine in commercial layers against IBV M41, 793B, D388(QX) and Q1 challenge was 91%, 94%, 73% and 84%, respectively. The level of protection in the SPF layers against IBV M41, D388(QX) and Var2 challenge was 89%, 69%, and 96%, respectively. In summary, vaccination with a live attenuated vaccine which includes an IBV Massachusetts strain (H120, GI-1) and an IBV Q1 strain (BNF 28/86, GI-16) provides a substantial level of protection against the homologous and most heterologous challenge viruses, which are representatives of the IBV strains circulating worldwide.