Highly Pathogenic Avian Influenza Virus (HPAIV) poses a serious threat to the poultry industry and public health due to its global spread to avian and non-avian hosts. To combat the spread of HPAIVs in poultry and reduce the risk of zoonotic transmission, the World Health Organization underscores the importance of strategic surveillance and advancements in vaccination strategies. For the prevention of avian influenza outbreaks in poultry and their transmission to humans and cattle, vaccination would be a critical tool. We critically review the limitations of current vaccine platforms and highlight innovative vaccine strategies against HPAIV that are essential for addressing future pandemic threats. The aim is to clarify the progress and challenges in AIV vaccine development and offer insights into recent technological advancements shaping future vaccination strategies.

ABSTRACT Erysipelas is caused by the bacterium Erysipelothrix rhusiopathiae and affects a wide spectrum of mammals and birds, including poultry such as turkeys, chickens, and waterfowl. This study retrospectively summarizes poultry outbreaks diagnosed at the Swedish Veterinary Agency from 1998–2023 with primary focus on laying hens during 2014–2023. For this purpose, case notes, bacterial culture results, farmer interviews, and whole genome sequencing were used. A total of 175 flocks were diagnosed, of which 155 (88.6%) outbreaks occurred in chickens (laying hens and parent breeders) and the remaining in turkeys, geese, and emus. Many of the outbreaks occurred in organic and free-range laying hen flocks. Multiple outbreaks occurred on 41.6% of the laying hen farms (range: 2–6 flocks/farm). In 2014–2023, 17.7% of all laying hen necropsy submissions were diagnosed with erysipelas (81 flocks). The disease was associated with a sudden onset of mortality and sometimes egg-drop. Newcastle disease or avian influenza was initially suspected in 16.1% of laying hen outbreaks (2014–2023). Bacterial co-infection was rare, and non-selective culture conditions were usually sufficient for diagnosis. Farmer interviews revealed that vaccination and euthanasia/slaughter were common interventions. Whole genome sequencing of isolates from laying hens identified serotypes 1a, 1b, 2, 5, and 6 of clade 2, 3, and i (intermediate). Multiple isolates within and between different flocks on the same farm were often closely related when outbreaks clustered in time (P = 0.0016). This is the hitherto largest erysipelas case series from poultry and provides useful information on an important emerging disease. RESEARCH HIGHLIGHTS Erysipelas is an important differential diagnosis of severe viral diseases. Most of the outbreaks occurred in organic and free-range laying hen flocks. Pre-enrichment or selective culture is useful in case of suspected co-infection. Isolates from temporally clustered outbreaks on a farm are often clonal.

Objective: To analyze the contamination of avian influenza virus (AIV) in poultry related environment in Shaanxi Province, and provide reference for the improvement of local avian influenza prevention and control. Methods: The relevant environments in 10 prefecture-level cities in Shaanxi from 2020 to 2024 (including urban and rural live poultry markets, large-scale poultry breeding farms, areas with small-scale poultry breeding houses, and slaughter houses and processing plants, etc.), were selected as surveillance points. External environmental samples such as poultry manure, surface swabs of poultry cages, poultry drinking water, and swabs of chopping boards were collected monthly. The subtypes of AIV were detected by real-time fluorescence quantitative RT-PCR, and finally descriptive analysis was conducted according to the surveillance time, area, site and sample type. Statistical analysis was performed by using software SPSS 25.0. Results: The annual average positive rate of AIV in poultry related environments was 3.54% (466/13 152) in Shaanxi from 2020 to 2024. Exhibiting two distinct positive rate peaks, with slight variation with years. AIV was mainly detected in the Loess Plateau area in northern Shaanxi (8.10%, 221/2 728) and the Qinba Mountain area in southern Shaanxi (3.34%, 121/3 622). The surveillance sites with relatively high positive rates included urban and rural live poultry markets (7.50%, 219/2 920) and poultry slaughtering and processing houses (7.19%, 32/445). The sample types with relatively high positive rates included swabs of chopping boards (10.95%, 81/740) and poultry cleaning wastewater (7.39%, 37/501), the differences were significant (P<0.001). In the positive samples, H9N2 virus was detected in all years, indicating that it was the most common subtype (81.76%, 381/466). Conclusions: From 2020 to 2024, the contamination of H9N2 AIV existed widely in poultry related environments in Shaanxi. The urban and rural live poultry markets and poultry slaughtering and processing houses in the Loess Plateau area in northern Shaanxi and the southern Qinba Mountain area in southern Shaanxi were the key places for the prevention and control avian influenza. It is necessary to strengthen the surveillance for the contamination of AIV in the poultry related environments. In the areas with high incidences, active and effective intervention measures should be taken in the places at high risk to reduce the risk of avian influenza outbreaks in humans and poultry.

Newcastle disease (ND), caused by Newcastle disease virus (NDV), is a significant threat to the poultry industry and outbreaks of virulent strains can lead to substantial economic losses. Studies to identify molecular pathways that can be used for intervention or to reduce pathology are critical for mitigating losses due to ND. In this study, we demonstrate that chicken mir-26a-5p upregulation inhibited the replication of both lentogenic and velogenic NDV strains. Computational analysis identified a highly conserved miR-26a-5p binding site in the NDV polymerase gene and transfection of the miR-26a-5p mimic following viral infection demonstrated a direct inhibition of polymerase transcripts while inhibitor transfection led to partial rescue of the miR-26a-5p mediated repression. Alternately, stable overexpression of miR-26a-5p led to the downregulation of multiple genes in the innate immune sensing pathway and led to a small but significant increase in viral titer for a velogenic NDV strain suggesting a pro-viral role. These data identified new roles for chicken miR-26a-5p in regulating NDV replication.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12985-026-03096-3.

Influenza A viruses (IAVs) are responsible for respiratory infections in a wide range of species, including birds, swine and humans. The role of wild boar (Sus scrofa) in IAV epidemiology remains underexplored. Here, we present a longitudinal serologic and virologic surveillance study of wild boars in Spain from 2015 to 2023. A total of 1643 nasal exudates and 2932 serum samples were analysed using quantitative RT-PCR, ELISA and haemagglutination inhibition (HI) assays to detect IAV positive samples and IAV targeted antibodies to characterise circulating viral subtypes. In addition, in the context of highly pathogenic avian influenza H5N1 outbreaks, we explored the potential transmission of avian IAV to wild boar. In summary, 6% of the serum samples tested positive and one IAV H3N1 was isolated. The seroprevalence remained stable from 2015 to 2018, undetected in 2019 and increased significantly from 2020 to 2023. The most frequently detected subtype was Eurasian avian-like H1 (clade 1C) while pandemic H1 (clade 1A) and human-like H1 (clade 1B) were less common. Human seasonal-like H3 strains from the 2000s (2000s-like H3) emerged in 2017 and have become more seroprevalent in recent years. A subset of wild boar sera from areas overlapping with H5N1 HPAI outbreaks in poultry and wild birds tested positive for recombinant H5 by ELISA, although H5N1 HI assays were negative. The monitoring of IAV in wild boar population allowed the identification of the temporal and spatial trends and shifts in the prevalence and characterisation of the infecting IAV strains. Our data suggest potential spillover events from human or other sources and support the inclusion of integrated monitoring of the wild suids as IAV reassortment-prone hosts in influenza surveillance programs.

H9N2 avian influenza viruses (AIVs) are widely distributed, causing continuous outbreaks in poultry and sporadic infections in humans. This study assessed the humoral immune response induced by two inactivated vaccines largely used in poultry. Serum samples were collected from 70 specific pathogen-free chicks at days 21 and 28 post-vaccination and tested against recent avian-derived H9N2 strains from G1 and B (Y280) lineages, isolated in China, Egypt, Benin, Togo, Algeria, and Morocco. The Hemagglutination Inhibition (HI) test was used to measure antibody responses. In Group A (vaccinated with vaccine 1), HI titers showed a significant increase between day 21 and 28. In contrast, group B (vaccinated with vaccine 2) exhibited consistently higher HI titers at both time points but showed no statistically significant increases by day 28 for any strain (all P-values > 0.05). This suggested that vaccine 2 elicited a stronger initial immune response, but with limited further increase over time. Notably, both vaccines induced significantly lower, but still relevant, geometric mean HI titers against the China strain (A/Suzhou/GIRD01/2019) followed by the Algerian strain (A/chicken/Algeria/219/2017) compared to other isolates at both time points. The negative control group (NC) remained seronegative throughout the study. These findings highlight potential antigenic variations among different H9N2 strains and emphasize the need for careful vaccine selection to ensure optimal protection across different geographical regions.

The 2021-2022 high pathogenicity avian influenza (HPAI) epizootic was the worst ever recorded in Europe in general and in Spain in particular. Between December 2021 and November 2022, H5N1 clade 2.3.4.4b HPAI viruses caused outbreaks in both wild birds and domestic poultry in Spain. We analysed the complete genome sequences of H5N1 HPAI viruses identified during this period in Spain and conducted comparative phylogenetic analyses to identify their origin and reconstruct their evolutionary and diffusion dynamics. We identified four different genetic reassortants of H5N1 clade 2.3.4.4b HPAI viruses. Our results suggest multiple wild bird introductions of H5N1 clade 2.3.4.4b HPAI viruses into different regions of Spain from other European countries. Bayesian phylodynamic analyses of H5N1 clade 2.3.4.4b HPAI viruses support that their initial entry into Spain occurred in the North-West and South-West through wild birds, which further spread the viruses to other regions within Spain. Andalusia (South) was the hotspot for maintenance of viruses in poultry. Wild Anseriformes played a crucial role in the introduction of the viruses into Spain and the subsequent transmission of these viruses to other host types of birds, both wild and domestic. This study highlights the role of wild birds in the ecology of H5N1 clade 2.3.4.4b HPAI viruses and provides further insight into the genetic diversity, evolution, and spread of these viruses between wild birds and poultry.

Avian influenza (AI) remains a major and persistent threat to animal and public health due to its high pathogenicity, zoonotic potential, and capacity for transboundary dissemination. The introduction of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b into the Americas in 2022 marked a critical shift in the regional epidemiological landscape, with Latin America emerging as one of the most vulnerable region. This review synthesises current knowledge on the aetiology, molecular determinants of pathogenicity, transmission dynamics, and the regional epidemiological situation of avian influenza from 2019 to 2025. Multiple Latin American countries, including Peru, Chile, Argentina, Ecuador, Mexico, Colombia, Brazil and Bolivia, have reported outbreaks in wild birds, domestic poultry, and mammals, alongside sporadic human cases. Key regional drivers include migratory bird flyways, informal live-bird trade, and uneven diagnostic and surveillance capacities, all of which facilitate viral persistence and spread. Management strategies are critically analysed, encompassing epidemiological surveillance, contingency planning and notification to the World Organisation for Animal Health (WOAH), farm-level biosecurity, movement restrictions, stamping-out and carcass disposal, vaccination approaches, and training of producers and veterinarians. Experiences from Mexico, Egypt, and China illustrate both the potential and the challenges of vaccination, reinforcing the need for risk-based application, DIVA-compatible diagnostics, and rigorous value-chain surveillance. Despite progress, structural weaknesses in veterinary infrastructure, cross-border coordination, and genomic surveillance persist. Strengthening One Health framework, harmonising regional policies, and sustained investment in laboratory and field capacities are essential to mitigate the continuing threat of HPAI and to safeguard food security, trade, biodiversity, and public health in Latin America.

Avian influenza research through the lens of One Health: A bibliometric study.

H5 high pathogenicity avian influenza virus (HPAIV) continues to spread globally, causing several high pathogenicity avian influenza (HPAI) outbreaks in poultry and significant economic losses. Biosecurity measures that prevent the introduction of HPAIV represent a top priority for controlling HPAI outbreaks on poultry farms. Although these measures are crucial for minimizing HPAI introduction, outbreaks of viral infection on poultry farms persist, underscoring the importance of continuously improving biosecurity protocols. Therefore, safe and effective microbicide disinfectants could play an essential role in reducing viral spread by inactivating viral particles on surfaces and in the air. This study assessed the efficacy of gaseous chlorine dioxide (ClO2) against H5 HPAIV under both gaseous ClO2 inactivation setting and in vivo conditions. In the gaseous ClO2 inactivation setting, only low virus titers were recovered (< 0.5–1.5 log10 TCID50/mL) when H5 HPAIV aerosols were exposed to gaseous ClO2 (0.05 ppmv, 0.14 mg/m3) for 5 min, corresponding to an approximately 2.0–3.0 log10 reduction. Furthermore, in vivo, all chicks exposed to aerosolized H5 HPAIV, which were treated with 0.1 ppmv gaseous ClO2, survived for 14 days post-challenge, demonstrating complete protection against the virus. The minimum effective concentration of gaseous ClO2 was 0.01 ppmv for 5 min of inactivation in the inactivation setting, and 0.05 ppmv for 5 min in vivo, indicating that relatively low concentrations are sufficient for effective viral inactivation. Therefore, gaseous ClO2 was effective at inactivating aerosolized H5 HPAIV and has potential for use as a disinfectant to prevent HPAIV introduction into poultry. (245/250) words.

A prompt and accurate diagnosis of respiratory viral diseases in intensive poultry production is essential to safeguard animal health and ensure the economic sustainability of farms. Currently, much effort is being devoted to preventing the spread of the avian influenza virus in farms. However, the diagnosis of other relevant respiratory viruses, as infectious laryngotracheitis virus (ILTV), is also crucial. Indeed, infection by ILTV does lead to substantial economic losses due to high morbidity, reduced growth, and decreased productivity, making rapid detection a critical aspect of disease control. Conventional diagnostics, including PCR and qPCR, while sensitive and specific, require expensive laboratory infrastructure and well-trained personnel, limiting their deployment in field settings where immediate intervention is most valuable. To address these limitations, this protocol describes a portable molecular diagnostic workflow based on loop-mediated isothermal amplification (LAMP) combined with gold nanoparticle–DNA nanoprobes for specific and visual detection of ILTV directly at the point of need. Gold nanoparticles synthesized via the Turkevich method are functionalized with thiolated DNA probes, which undergo full-length, sequence-specific hybridization to LAMP amplicons, enabling a naked-eye colorimetric readout. The procedure integrates streamlined steps for DNA probe preparation, nanoparticle synthesis and assembly, and minimal sample processing, compatible with on-farm deployment. Results obtained with this workflow on field samples demonstrated 100% sensitivity and specificity, matching the performance of gold-standard assays. This approach offers a rapid, cost-effective, and equipment-free detection system of viral pathogens, enabling timely decision-making for disease containment and biosecurity. By overcoming the barriers of conventional diagnostics, this protocol enables producers with powerful tools for efficient monitoring and response to respiratory outbreaks in poultry farms.Key features• Direct ILTV detection in respiratory swabs in 35–45 min, bypassing DNA extraction with a rapid viral lysis step.• Specific colorimetric readout via DNA nanoprobes with visual interpretation, requiring no specialized equipment or lab infrastructure.• Achieves 100% sensitivity and specificity compared to qPCR, with a detection limit of 200 viral copies per reaction; validated in lab conditions with field samples.• Modular design: Enables multiplex and customizable detection of other poultry pathogens, supporting rapid kit development and broad field application.

Newcastle disease (ND) is a highly contagious and economically important viral disease of poultry, caused by virulent strains of Orthoavulavirus javaense (OAVJ). In Slovenia, vaccination is mandatory in commercial poultry and selected avian species, whereas backyard and free-range flock remain largely unregulated. In January and February 2025, two unrelated backyard and free-range flock of laying hens experienced acute outbreaks with severe clinical signs, increased mortality and distinct gross necropsy findings (haemorrhages in the mucosa of the gastrointestinal tract, multifocal pale foci in the liver, atrophy to enlarged hyperaemic spleen, oophoritis and salpingitis). OAVJ was detected in cloacal, oropharyngeal, and brain samples from both outbreaks using real-time RT-qPCR. Analysis of complete fusion (F) gene revealed identical nucleotide sequences in both outbreaks, with the cleavage site motif, characteristic of velogenic strains (amino acid sequence 112RRQKR116 at the C-terminus of the F2 protein and F at residue 117, the N-terminus of the F1 protein). Further phylogenetic analysis of the F gene demonstrated that both viruses belong to class II, sub-genotype VII.1.1, showing 99.6-100% identity with strains recently detected in Poland. The hemagglutinin-neuraminidase (HN) glycoprotein comprised 571 amino acids, consistent with genotype VII viruses, with several amino acid substitutions previously associated with functional relevance. These results highlight that, despite the absence of ND in Slovenia for more than three decades, local poultry populations remain highly susceptible to the introduction of the virus, especially in backyard flocks where monitoring and disease control are difficult to implement. Although a virulent virus was confirmed in both outbreaks, no further spread to other poultry holdings was detected.

The unprecedented 2.3.4.4b. A(H5N1) outbreak in dairy cattle, poultry, and spillover to humans in the United States (US) poses a major public health threat. Population immunity is a critical component of influenza pandemic risk assessment. We assessed the pre-existing cross-reactive immunity to 2.3.4.4b A(H5N1) viruses and analyzed 1794 sera from 723 people (0.5–88 yrs) in multiple US geographic regions during 2021–2024. Pre-existing neutralizing and hemagglutinin (HA)-head-binding antibodies to A(H5N1) were low, but there were substantial cross-reactive binding antibodies to N1 neuraminidase (NA) of 2.3.4.4b A(H5N1). Antibodies to group 1 HA stalk were also prevalent and increased with age. A(H1N1)pdm09 infection and influenza vaccination did not induce neutralizing antibodies to A(H5N1) viruses but induced significant rise of functional NA inhibition (NAI) antibodies to N1 of 2.3.4.4b A(H5N1), and group 1 HA stalk antibodies. Moreover, pre-pandemic stockpiled 2.3.4.4c vaccine can elicit cross-reactive neutralizing antibodies to 2.3.4.4b A(H5N1) viruses. Understanding population susceptibility is essential for pandemic preparedness.

Spillover risks of contagious diseases affecting both wildlife and farm animals are of growing concern. Since late 2020, several waves of highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4b have been observed in poultry farms in Denmark, impacting the poultry industry. Concurrently, many wild birds have been found infected and dead of this disease. As the epidemic developed, 49 farm outbreaks and over 2000 infected wild birds were detected in Denmark from late 2020-2024. Thus, it is important to investigate the interactions between wild birds and poultry farms and identify the spillover risks of HPAIV from free-living wild birds to domestic poultry. Using a previously developed mechanistic model for HPAIV in Danish wild birds and statistical tests (including correlation tests and logistic regressions), we quantified this spillover risk in Denmark in space and time. The mechanistic model identified a constant hot spot of HPAIV spillover risk in southern Zealand which corresponds to the hot spot previously identified using reported poultry outbreaks. The model estimated farm-specific risks with a precision level of 78 % for the simulated period. The population changes of the barnacle goose (Branta leucopsis) were found to be significantly associated with poultry outbreaks. A 3-week time lag across Denmark between wild bird HPAIV detections and subsequent poultry outbreaks was discovered, together with regional differences of this time lag. Our study showed the relationships between wild bird populations/detections and poultry outbreaks and the simulated weekly risk maps can help decision-making for prevention and surveillance.

Poultry workers in Washington, USA, were infected with highly pathogenic avian influenza A(H5N1) virus and recovered. The viruses were clade 2.3.4.4b genotype D1.1, closely related to viruses causing poultry outbreaks. Continued surveillance and testing for influenza A(H5) clade 2.3.4.4b viruses remain essential for risk assessment and pandemic preparedness of zoonotic influenza viruses.

This report summarises the outcomes of avian influenza (AI) surveillance activities conducted in 2024 in the context of the Avian Influenza Data Collection (AIDC), the One Health (OH) initiatives of the EU4Health Programme (EU4H, 2022 co‐funded grant agreements on emerging and re‐emerging zoonotic pathogens) and the SENTINEL project. Surveillance encompassed poultry, captive and wild birds, and mammals across EU Member States (MSs) and selected non‐EU countries. A summary of the outbreaks reported in the Animal Disease Information System (ADIS) is also provided. A total of 276,621 records were submitted under the AIDC by 31 reporting countries, 16,755 under OH and 9804 under SENTINEL. Additionally, 204,851 poultry population records were voluntarily provided. Surveillance was risk‐based, aiming to detect highly pathogenic (HPAIV) and low pathogenic influenza A viruses (LPAIV), enhance early warning capacity and improve understanding of zoonotic potential. In poultry, in the context of the AIDC, 27,739 establishments were sampled, yielding 218,667 samples. HPAIV was detected and reported in 107 visits, mainly subtype H5N1 and LPAIV in 53. The highest HPAIV activity occurred in the first quarter. In total, 394 poultry outbreaks were reported in the EU and 66 in non‐EU countries through the ADIS. In captive birds, 296 visits were reported via the AIDC, resulting in seven HPAIV and one LPAIV detections. Ninety outbreaks were reported in 12 EU countries and 53 in five non‐EU countries through ADIS. In relation to wild birds, samples from 36,668 animals were submitted via the AIDC and 6375 via OH and SENTINEL, yielding a total of 1317 HPAIV detections, primarily in waterfowl. Twenty‐three EU countries and eight non‐EU countries reported a total of 910 outbreaks through ADIS. Mammal surveillance included 89 AIDC and 8960 OH samples. Four HPAIV detections were reported via AIDC, while additional virological and serological positives, mainly in carnivores, were identified in OH programme.

Highly pathogenic avian influenza virus (H5N1) continues to cause substantial losses in the poultry industry of Bangladesh, with ongoing genetic evolution. This report presents the complete genome sequence of an H5N1 subtype of avian influenza A virus isolated from a recent outbreak on a commercial layer chicken farm in Bangladesh.

The arrival of H5N1 clade 2.3.4.4b genotype B3.2 in South America marks an unprecedented geographic expansion of highly pathogenic avian influenza viruses. The continent remains the only region with sustained H5N1 transmission in wild marine mammals. To investigate the evolution of H5N1 in this novel context, we conducted genomic surveillance in marine wildlife along the northern Patagonian coast in Argentina (August 2023 – February 2024). Phylogenetic analyses revealed two B3.2 subclades: an avian subclade linked to poultry outbreaks in central Argentina, and a marine mammal subclade that persisted locally and repeatedly spilled back into seabirds, causing mortality in terns. Notably, most seabird viruses retained mammalian-adaptive mutations; however, one tern cluster exhibited reversion only at PB2-N701D. These findings suggest the ability of South American seabirds to sustain mammal-adapted H5N1 viruses, potentially enabling long-distance spread and establishment in novel wildlife reservoirs, thereby threatening biodiversity and increasing risks to animal and public health.

The H5N1 clade 2.3.4.4b avian influenza virus outbreak in poultry and dairy cattle is a potential pandemic threat for humans. A safe and effective H5N1 influenza vaccine will be needed if the virus acquires the capacity for efficient human-to-human transmission and may also be useful as a veterinary vaccine. In this study, we demonstrate robust vaccine protection in a lethal model of H5N1 clade 2.3.4.4b influenza infection in cynomolgus macaques. We vaccinated 24 cynomolgus macaques with mRNA or rhesus adenovirus serotype 52 (RhAd52) vaccines expressing the hemagglutinin (HA) from H5N1 clade 2.3.4.4b by the intramuscular or intratracheal route and challenged them with the H5N1 human isolate hu-TX37-H5N1. Of sham control animals, 83% (five of six) developed severe rapidly progressive consolidative pneumonia and were euthanized by days 5 to 7 after challenge. In contrast, 100% (17 of 17) of vaccinated macaques survived and controlled virus replication to undetectable titers in both the upper and lower respiratory tracts by days 4 to 14 after challenge. Mucosal boosting with the RhAd52 HA vaccine generated robust mucosal antibody and T cell responses and afforded 6.3 and 5.1 log10 median viral load reductions in viral RNA with no detectable infectious virus titers compared with sham controls in bronchoalveolar lavage and nasal swabs, respectively. These data demonstrate that an adenovirus-vectored vaccine can protect against lethal H5N1 clade 2.3.4.4b challenge in nonhuman primates and further highlight the importance of vaccine-elicited mucosal immunity.

Poultry farming is threatened by regular outbreaks of Escherichia coli (E. coli) that lead to significant economic losses and public health risks. However, traditional surveillance methods often lack sensitivity and scalability. Early detection of infected poultry using minimally invasive procedures is thus essential for preventing epidemics. To that end, we leverage recent advancements in computer vision, employing deep learning-based tracking to detect behavioural changes associated with E. coli infection in a case–control trial comprising two groups of 20 broiler chickens: (i) a healthy control group and (ii) a group infected with a pathogenic E. coli field strain from the poultry industry. More specifically, kinematic features derived from deep learning-based tracking data revealed markedly reduced activity in the challenged group compared with the negative control. These findings were validated by lower mean optical flow in the infected flock, suggesting reduced movement and activity, and post-mortem physiological markers of inflammation that confirmed the severity of infection in the challenged group. Overall, this study demonstrates that deep learning-based tracking offers a promising solution for real-time monitoring and early infection detection in poultry farming, with the potential to help reduce economic losses and mitigate public health risks associated with infectious disease outbreaks in poultry.