Although poultry meat production supports the livelihood and provides food security for billions of people worldwide, it is facing substantial challenges. The emergence of broiler breast myopathies (white striping, woody breast, spaghetti meat) at large scale is one of the most significant economic and welfare challenges that menace poultry production sustainability and for which there is currently no effective prevention, due to its unknown aetiologies. Here, by inviting and gathering several experts with diverse, but complementary disciplines, the objective of the present review is to highlight the current progress and knowledge on these myopathies. Five sections are presented, describing in detail the history and geographic occurrence of these breast myopathies, their macroscopic morphologies and microscopic characteristics, their putative aetiologies and causes as well as their underlying molecular mechanisms, and potential strategies and solutions. The is review summarizes both descriptive and functional mechanistic studies, highlights the complexity of these myopathies and the kinship between broiler genome, nutrition, and management, and outlines some of the promising molecular signatures. It aims to offer new fundamental frameworks for future investigations.

Eye drop (ED) and vent brush (VB) application of live infectious laryngotracheitis virus (ILTV) vaccine provides protective immunity against disease, but little is known regarding the immune responses following application. This study compared the gene expression of immune markers associated with VB and ED ILTV vaccination in the conjunctiva, trachea and cloaca at 3, 5, 7 and 10 days post-vaccination (dpv) and 3, 5 and 7 days post-revaccination (dprv). The relative gene expression of markers associated with inflammatory responses and their regulation (CCL4, CCR5, IL2, IL4, IL6, IL17C, IFNG), pathogen recognition receptors (TLR2-2, TLR4, TLR7) and cell surface markers (CD4, CD8A, CD14, CD80) was evaluated by RT-PCR after ED or VB vaccination and revaccination using the alternate route (ED/VB (primary/booster), VB/ED). There was increased expression of inflammatory markers at vaccination sites following primary vaccination. In the VB group, there was increased expression of IL6 and IFNG in cloaca (3 dpv) and IL2 in the conjunctiva (7 dpv) compared to the ED group ( < 0.05), while there was increased CCL4 expression in conjunctiva (5 dpv) in the ED group compared to the VB group. ED vaccination was associated with increased expression of IL2 and IL17C in trachea while VB vaccination was associated with increased expression of IL6 and IL17C in trachea. Similarly, ED/VB- and VB/ED-associated increases in IL2, IL6 and IL17C expression were observed at the revaccination sites. In conclusion, immune responses after the first and second ILTV vaccination were site-specific and associated with inflammatory responses in the mucosa of the vaccinated tissues and trachea. ILTV vaccination elicited inflammatory responses at the vaccination sites (conjunctiva and cloaca).Conjunctival or cloacal vaccination elicited similar inflammatory responses in the trachea after 3 and 5 days, respectively.Revaccination by a different route stimulated similar immune responses in conjunctiva, cloaca and trachea.

Broiler birds as compared to layers are more susceptible to avian colibacillosis.An aerosol challenge using an -APEC effectively evaluates disease pathogenesis.The -APEC persistently colonized the bursa of Fabricius after aerosol exposure.

Gastrointestinal nematode infections, particularly , pose challenges to the poultry industry especially in free-range chickens. These nematodes employ sophisticated immunomodulation strategies to evade host immune defences, allowing them to establish chronic infections. Excretory-secretory (ES) products, including extracellular vesicles (EVs), play a pivotal role in host-parasite communication. Thus, this study aimed to investigate the immunomodulatory properties of nematode-derived ES/EVs, and evaluate the impact of ivermectin (IVM) on these interactions . Adult worms were collected from the jejunum of infected chickens and cultured with or without IVM treatment. ES products were collected, and EVs were enriched using size-exclusion chromatography. T-cell proliferation and macrophage activation assays were performed to assess the immunomodulatory effects of ES/EVs. -derived ES products suppressed T-cell activation (CD25+CD57+ cells) and reduced blast transformation in both CD4+ and CD8+ T-cells (< 0.05). Furthermore, ES promoted TLR4-induced macrophage NO production, changed macrophage-activated surface phenotype, and inhibited macrophage phagocytosis in high concentration but promoted it in low concentration (< 0.05). Additionally, -derived EVs were detected in culture supernatants, and this EV secretion was decreased with the IVM treatment (< 0.05). Fourier-transform infrared spectroscopy confirmed IVM treatment altered EV cargo composition. Finally, the EVs influenced cytokine profiles of activated macrophages, decreasing pro-inflammatory cytokine gene expression (IL-1β and IL-8, < 0.05) which may mirror immune evasion . In summary, this study highlights immunomodulatory mechanisms of ES/EVs and provides fundamental information for developing diagnostic and therapeutic strategies targeting nematode ES products including EVs.RESEARCH HIGHLIGHTSExcretory-secretory (ES) products, including extracellular vesicles (EVs), demonstrated immunomodulatory properties. ES suppressed T-cell activation, proliferation, and macrophage phagocytosis. ES, including EVs, may help in evading the host immune system.

The circulating serotypes/genotypes of avian infectious coryza (AIC) in Iran have not been fully characterized, and disease control in layer and breeder flocks largely relies on imported vaccines. Given the correlation between genotypes and serotypes based on the previously proposed genotyping method, this study aimed to determine the genotypes of 28 Iranian isolates collected over a 7-year period (2018-2025), using sequences of region 1 and the hypervariable region (HVR) of the gene. PCR amplification of both regions was performed, and the resulting sequences were analysed alongside reference strains retrieved from GenBank. Two datasets were generated: one based on region 1 (aligned with the Page serotyping scheme) and the other based on concatenated sequences (corresponding to the Kume scheme). Phylogenetic analysis identified five previously known genotypes (I, II, VI, VIII, and IX), corresponding to serovars A-1, A-2, C-4, C-3, and an undetermined Kume serovar, in 24 isolates. Notably, two isolates (AP-20 and AP-28) formed distinct, well-supported phylogenetic clusters and were designated as novel genotypes XV and XVI, respectively. The HVR could not be amplified in two additional isolates (AP-17 and AP-18); however, analysis of their region 1 sequences indicated a close relationship to United States non-pathogenic strains. These findings suggest that the currently proposed genotyping scheme may be inadequate for classifying non-pathogenic strains. The circulation of multiple genotypes in Iran underscores the need for continued surveillance and re-evaluation of currently used vaccines, as effective control of AIC requires serotype-specific bacterins in vaccination programmes.

Newcastle disease (ND), caused by Newcastle disease virus (NDV), has posed a continuous threat to Iran's poultry industry since its first detection in the early 1950s, with subgenotype VII.1.1 currently recognized as the dominant circulating strain. To gain deeper insights into the evolutionary dynamics of NDV in Iran, we performed genome sequencing and phylogenetic analysis on 60 viruses isolated from domestic poultry and wild birds between 2017 and 2024. Maximum likelihood and Bayesian phylogenetic analyses of the fusion (F) and haemagglutinin-neuraminidase (HN) genes revealed that all viruses belong to subgenotype VII.1.1, forming a well-supported monophyletic group, indicative of independent evolution of this subgenotype within Iran after its introduction. The F and HN genes displayed high sequence identities of over 97% and 93%, respectively. All viruses contained a polybasic cleavage site in the F gene (R-R-Q/K-K-R↓F), consistent with virulent NDV strains. The estimated evolutionary rates for the F and HN genes were 1.31 × 10 and 9.62 × 10 substitutions/site/year, respectively. The most recent common ancestor of the subgenotype VII.1.1 F gene was dated to 2007 (95% highest posterior density: 2005-2009), likely originating from the Middle East. Bayesian skyride analysis showed an exponential increase in viral diversity between 2020 and 2024. Continuous surveillance of NDV in both poultry and wild birds in Iran is essential to track ongoing viral evolution, monitor potential changes in virulence or transmissibility, and identify emerging threats to poultry health and production.

Commercial inactivated vaccines improved the clinical picture of H5N1 in challenged birds.The developed vaccines induced protective antibody titres against HPAIV clade 2.3.4.4b within 4 weeks.The developed vaccines provided full protection against challenge by HPAIV clade 2.3.4.4b.The developed vaccines provided a significant reduction in virus shedding.

First complete genome sequencing of a DHAV-3 strain from Egypt using m-NGS.Discovery of a novel duck astrovirus co-infecting with DHAV-3.Phylogenetic analysis reveals cross-border transmission links with Asian strains of both DHAV-3 and DAstV-5.

Velogenic NDV genotype VII.2 detected in vaccinated chickens in southern Vietnam.Isolate was highly virulent with ICPI 1.81 and MDT of 56 h.Rapid onset of disease, severe lesions, and efficient oral/cloacal viral shedding.Findings call for improved NDV surveillance and tailored vaccination in Vietnam.

North-Western European reassortants (A3B1) were found in Italy for the first time.Local A3B1 clade, related to Russian and Middle Eastern strains, also persisted.Infectious pressure was seemingly stable despite this epidemiological shift.

Identified 26 antibiotic resistance genes, including novel plasmid IncI1-(α) never described in Gallinarum.Revealed 107 virulence genes and multiple complete SPIs like SPI-1 and SPI-2.SNP analysis suggested reversion to virulence in eight vaccine-related strains.

This paper describes the investigation of the epidemiology of fowl adenoviruses (FAdVs) among fast-growing meat-type breeder parent chickens in Sweden, based on serology, PCR and partial genome sequencing of samples collected during rearing and egg production. Blood samples ( = 1910) from breeder flocks at 16 (79 flocks), 24 and 36 (52 flocks) weeks of age were analysed for FAdV antibodies. Ninety-four percent of the flocks had seroconverted at 16 weeks of age, and at 36 weeks of age all 52 flocks were seropositive. From 35 of these flocks, dead-in-shell chicks (DIS,  = 949) from eggs laid at 26-27 and 36-37 weeks of age were sampled, and pooled liver and caecal tonsils were analysed by PCR. Nucleic acid from FAdV was not detected. Negative PCR results were confirmed by testing tissues from 62 broiler breeders and 80 DIS from four additional seropositive flocks, collected at age 24-26 weeks. From six other breeder flocks, liver and caecal tonsils were sampled from one bird (when available) per day during rearing from 1-112 days of age. From 6 weeks of age, in 4/6 flocks, FAdV species A and/or D were detected by PCR and partial hexon gene sequencing. In conclusion, FAdVs were detected during rearing in breeder birds but not in DIS. This suggests that vertical transmission of FAdVs was prevented by immunity acquired early in life. However, it should be noted that high antibody titres in breeder birds does not necessarily confer protection against vertical transmission. The majority of 16-week-old parent flocks were seropositive to FAdV.FAdV was not detected by PCR in dead-in-shell chicks from seroconverted flocks.FAdV-A and D were detected in broiler breeders during rearing from 6 weeks of age.Results suggest that vertical spread was prevented by immunity in breeder birds.

This study examined the genetic diversity in a collection of field isolates of and compared that with the diversity in the serovars A-D and F-I reference strains and available whole genome sequences. Phylogenetic analysis of the 16S rRNA gene of the nine Australian isolates and twelve sequences of overseas isolates resulted in six clusters with the Australian isolates not closely related to either the type strain or the serovar reference strains. The suitability of low-cost finger printing techniques, ERIC-PCR and rep-PCR, when applied to were also evaluated. The fingerprints generated through ERIC-PCR were more informative and this method subsequently used to examine the genetic diversity of the isolates and the reference strains. The ERIC-PCR patterns confirmed the isolates and strains were quite diverse, with 15 different patterns detected. These results suggested that the Australian isolates were genetically distinct from the overseas strains, consistent with the genetic distinction observed in the phylogenetic study. Whole genome sequences of the Australian isolate BR2963 and the 15 genomes identified as in the Genome Taxonomy Database confirmed that serovars F, K and M form a cluster distinct from other and probably represent a distinct species within the genus . Additionally, the Australian isolate BR2963 had an average nucleotide identity level with the type strain (DSM15997) below the accepted 95% threshold for species suggesting that the isolate is a member of the genus but not within the species .

Infectious laryngotracheitis virus (ILTV) remains a significant viral disease in the poultry industry worldwide and vaccination has proven to be an invaluable tool for disease control. Vaccine type, dose and route of administration are important parameters that determine the success of vaccination programmes and control strategies. The current study aimed to investigate the optimal dose for drinking-water vaccination with ΔgG-ILTV, an attenuated glycoprotein G-deficient ILTV vaccine that is efficacious when administered by eye-drop. Three groups of 1-week old specific-pathogen-free chickens were vaccinated with increasing doses of ΔgG-ILTV (10, 10 and 10 plaque-forming units per bird) via the drinking-water. Additional groups of birds included an eye-drop vaccination control ( = 20), and two unvaccinated control groups ( = 20 and 10, respectively). Three weeks after vaccination, all groups, except one unvaccinated control group ( = 10), were challenged with virulent ILTV. Vaccine efficacy was assessed after challenge by recording mortality rate and scoring of clinical signs and gross tracheal pathology. Challenge resulted in severe clinical disease and a high mortality rate in unvaccinated birds. Eye-drop vaccination resulted in complete clinical protection against this specific challenge. The efficacy of drinking-water vaccination showed a direct association with the administered vaccine dose. Results from this study highlight the need for improved understanding of virus-host interactions and immunological responses that occur following drinking-water vaccination, in order to improve the efficacy of vaccination strategies that use this route.

Heterogeneous methods of evaluation are applied in the context of avian disease surveillance, with 26 attributes identified.Sensitivity resulted as the attribute most frequently used, with slight variations in definition across studies.The human behavioural dimension and the effectiveness of spatial coverage in surveillance systems were infrequently addressed.Highlights the need for standardized guidelines for evaluation of disease surveillance.

Infectious bursal disease (IBD) is an immunosuppressive disease that increases susceptibility to avian coccidiosis, but the contrary is unclear. In a battery trial, this study evaluated whether prior (ET) infection of Egyptian Baladi chickens increased the virulence of the very virulent IBD virus. Birds grouped as follows: G1 (control), G2 (ET, 1.5×10 oocysts), G3 (ET, 5×10 oocysts), G4 (IBDV), G5 (G2+BDV), and G6 (G3+IBDV). At 21 days of age (d), chickens were sham- (G1 and 4) or ET- (G2, 3, 5, and 6) challenged. Four days later, G4-6 received IBDV by intranasal/ocular route. The birds were evaluated for growth performance and inspected clinically. The phagocytic test, cloacal viral shedding, and immunological organ index were evaluated on days 28 and 32. On day 28, the bursa of Fabricius (BF), spleen, and caecum were histologically analyzed, and caecal lesions were scored macroscopically. Compared to the G1, all challenged groups displayed worse growth performance ( ≤ 0.01). G5 and 6 outperformed G4 regarding weight gain and FI (P≤0.01), however, they still lagged behind G2 and 3 ( ≤ 0.01). Interestingly, the BF of G2 and 3 had a higher mean severity index (MSI) than G1 ( ≤ 0.01), indicating histological evidence of Eimeria stages. Nonetheless, G4's MSI was higher than G2's and G3's ( ≤ 0.01). Compared to G4, G5 and G6 displayed a substantially lower MSI and a higher BF' index. Mortalities in G4 and G6 were 10% and 5%, respectively. Compared to G4, G5 and 6 displayed increased viral shedding titers ( ≤ 0.01). Regarding coccidiosis, G5 and G6 exhibited lower phagocytic activity and higher oocyst counts and caecal lesion scores than G2 and G3 ( ≤ 0.01), suggesting that exposure to IBDV after ET enhanced ET pathogenicity and reproduction. Conclusions: ET interfered with the IBDV pathogenesis (increase in viral shedding, but less severe lesions compared to mono-infected birds); this could be because prior ET infection modulated T cells.

In the present study, antigen-chitosan-PLGA nanoparticles were explored as the delivery system for inactivated whole infectious bursal disease virus (IBDV) antigens. The immunized birds showed the peak antibody level (ELISA titre 4095.65 ± 55.74) at the 3rd week post-immunization, which was significantly higher than that of the commercial inactivated vaccine (titre 2257 ± 30) ( < 0.0001). The virus-loaded chitosan-coated PLGA nanoparticles induced good cell-mediated immunity. The immunized birds showed better resistance against the challenge infection with a very virulent IBDV. Only one bird out of the five challenged showed viral antigens in the bursa (80% protection), whereas, in the commercial vaccinated group, two chickens showed viral antigens in the bursa (60% protection). The histopathological lesions were also found to be very mild in the same group. The birds which were immunized with the antigen-chitosan-PLGA nanoparticles did not show any sign of immunosuppression. It is concluded that antigen-chitosan-PLGA nanoparticles afford the best protection among the groups, which lays a foundation for further development of a vaccine delivery platform in this line. First report on the use of Chitosan/PLGA nanoparticles with inactivated IBD virus.Nanoparticles prepared by solvent evaporation method.Elicited better humoral and cell-mediated immunity in chickens.Protection is better than commercial vaccine.

Metabolomics and 16S rRNA were used to explore the mitigating effect of naringenin on heat stress.Naringenin relieves heat stress through specific metabolic pathways.Changes in gut microbiota caused by naringenin and heat stress may affect host metabolism.

ARV strains of the same genotype had distinct pathogenic and transmission traits.LambdaC, muB, and sigmaC genes made a difference.SigmaC-based genotyping obscures pathogenicity differences.

The host B locus and the IBDV pathotype impact development of clinical disease.The host B locus has significant effects on IBDV-induced early mortality.The host B locus has no significant effect on IBDV-induced bursal damage.

Avian pseudotuberculosis infection usually presents as well-demarcated visceral necrotic foci, typically affecting the gastrointestinal tract, liver and spleen. This case series describes an atypical presentation of (Yptb) characterized by severe chronic myositis, arthritis and osteomyelitis in five village weavers (), and acute osteomyelitis and myositis associated with septicaemia in an oriental magpie robin () from a zoological collection. Clinical signs of the weavers included lethargy, poor flying ability and focally extensive periarticular and muscular swelling, whereas the magpie robin was found dead without premonitory signs. Radiography revealed focal lytic and proliferative bone lesions with loss of articular congruity and increased radiopacity of skeletal muscles, which was compatible with severe necrotizing, granulomatous osteomyelitis and polyphasic myositis with large intralesional bacterial colonies on histology. Most ( = 4/5) birds with available histology exhibited only mild to moderate heterophilic to histiocytic inflammatory lesions in their intestines, spleen and liver. Bacterial cultures typically yielded Yptb from joint and muscle samples (3/3), and less consistently from visceral organs (6/11) and bone marrow (0/5). Bacterial typing using Fourier-transform infrared (FT-IR) spectroscopy suggested that weaver Yptb strains were closely related. Whole genome sequencing of two Yptb strains identified one as ST14 serotype O:2a and the other ST42 serotype O:1a, with the presence of virulence genes including plasmid-borne and chromosomally encoded virulence genes and . Weavers may be prone to develop atypical pseudotuberculosis with the musculoskeletal system as a predilection site for bacterial growth and associated granulomatous lesions.