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In late 2015, an epizootic of Highly Pathogenic Avian Influenza (H5Nx) was registered in Southwestern France, including more than 70 outbreaks in commercial poultry flocks. Phylogenetic analyses suggested local emergence of H5 viruses which differed from A/goose/Guangdong/1/1996 clade 2.3.4.4b lineage and shared a unique polybasic cleavage site in their hemagglutinin protein. The present work provides an overview of the pathobiological picture associated with this epizootic in naturally infected chickens, guinea fowls and ducks. Upon necropsy examination, selected tissues were sampled for histopathology, immunohistochemistry and quantitative Real Time Polymerase Chain Reaction. In Galliformes, HPAIVs infection manifested as severe acute systemic vasculitis and parenchymal necrosis and was associated with endothelial expression of viral antigen. In ducks, lesions were mild and infrequent, with sparse antigenic detection in respiratory and digestive mucosae and leukocytes. Tissue quantifications of viral antigen and RNA were higher in chickens and guinea fowls compared to duck. Subsequently, recombinant HA (rHA) was generated from a H5 HPAIV isolated from an infected duck to investigate its glycan-binding affinity for avian mucosae. Glycan-binding analysis revealed strong affinity of rHA for 3'Sialyl-LacNAc and low affinity for Sialyl-Lewis X , consistent with a duck-adapted virus similar to A/Duck/Mongolia/54/2001 (H5N2). K222R and S227R mutations on rHA sequence shifted affinity towards Sialyl-Lewis X and led to an increased affinity for chicken mucosa, confirming the involvement of these two mutations in the glycan-binding specificity of the HA. Interestingly, the rHA glycan binding pattern of guinea fowl appeared intermediate between duck and chicken. The present study presents a unique pathobiological description of the H5 HPAIVs outbreaks that occurred in 2015-2016 in Southwestern France.

Compliance with required on-farm biosecurity practices reduces the risk of contamination and spread of zoonotic and economically important diseases. With repeating avian influenza epidemics in the poultry industry, the need to monitor and improve the overall level of biosecurity is increasing. In practice, biosecurity compliance is assessed by various actors (e.g., academic, private and public institutions), and the results of such assessments may be recorded and gathered in databases which are seldom shared or thoroughly analyzed. This study aimed to provide an inventory of databases related to the assessment of biosecurity in poultry farms in seven major poultry-producing European countries to highlight challenges and opportunities associated with biosecurity data collection, sharing, and use. The institutions in charge of these databases were contacted and interviewed using a structured questionnaire to gather information on the main characteristics of the databases and the context of their implementation. A total of 20 databases were identified, covering the gamut of poultry species and production types. Most databases were linked to veterinary health authorities or academia, and to a lesser extent interbranch organizations. Depending on the institutions in charge, the databases serve various purposes, from providing advice to enforcing regulations. The quality of the biosecurity data collected is believed to be quite reliable, as biosecurity is mostly assessed by trained farm advisors or official veterinarians and during a farm visit. Some of the databases are difficult to analyze and/or do not offer information concerning which biosecurity measures are most or least respected. Moreover, some key biosecurity practices are sometimes absent from certain databases. Although the databases serve a variety of purposes and cover different production types, each with specific biosecurity features, their analysis should help to improve the surveillance of biosecurity in the poultry sector and provide evidence on the benefits of biosecurity.

In poultry farms, the assessment of biosecurity is usually based on checklists designed for production systems that do not allow access to a free-range area. However, providing outdoor access may increase the risk of contamination by certain pathogens (e.g., soil borne pathogens or those transmitted by wild birds). Therefore, in free-range systems, biosecurity assessment should specifically cover practices related to this particular environment. In this scoping review, we aimed to (1) identify and categorize specific biosecurity measures (BSMs) that could be assessed in free-range poultry farms in high-income countries based on published protocols, and (2) describe the context in which these studies were carried out. A systematic search was conducted in four databases (PubMed, Scopus, Agricola, and Web of Science) and reports were screened according to PRISMA-ScR guidelines. Studies were first deduplicated in EndNote™ and then screened in Rayyan. After screening 481 records, 15 studies were retained as eligible for the extraction of contextual data and the list of BSMs specific to free-range poultry systems. The studies relied on the assessment of a heterogeneous number of BSMs, and a total of 52 unique BSMs were identified and subsequently classified into 8 categories and 23 subcategories. Most measures were related to the presence of other species on the outdoor range—mainly wild birds (including attraction, interaction and direct observation), followed by effective range use by poultry. However, some aspects of biosecurity were seldom or only superficially addressed, such as access to the range by workers and equipment, the characteristics of the range, or methods for wild birds scaring. The proposed list and classification of BSMs should provide additional insights into how biosecurity assessment could be adapted and applied in free-range poultry production systems.

The ability of commercial vaccines H120 and 4/91 to protect against Moroccan-Italy 02 infectious bronchitis virus (Mor-It02) was investigated in specific-pathogen-free (SPF) chickens and commercial broiler chickens. Commercial broiler chicks (Experiment 1) were vaccinated at the hatchery with H120 vaccine at Day 1, and challenged at Day 21 with 104 50% egg-infective dose (EID50) of Mor-It02. All chicks were observed daily for clinical signs attributable to Mor-It02 infection during the 10 days postchallenge (pc). At 5 and 10 days pc, chicks were humanely sacrificed for necropsy examination, and tissues were collected for histopathology evaluation. To better understand the findings on commercial broilers, day-old SPF chicks were divided into five groups in a second experiment: Group Mass/4-91, vaccinated with H120 and 4/91 respectively at Days 1 and 15 of age; Group Mass/Mass, vaccinated by H120 at Days 1 and 15; Group Mass, vaccinated with H120 at Day 1; Group NV, kept unvaccinated; and Group NC, kept as a negative control (unchallenged). At Day 24 of age, Groups Mass/4-91, Mass/Mass, Mass, and NV were challenged with 104 EID50 of Mor-It02. In both experiments, blood samples were collected at different periods for serologic analyses. Oropharyngeal swabs were collected for virus detection by reverse-transcription PCR. In Experiments 1 and 2, respiratory signs started as early as 24 hr pc and maximum severity was observed on Days 3 and 4 pc. The viral shedding rate was significantly lower in Group Mass/4-91 compared to other challenged groups. Serologic analysis in both experiments showed that the sera of challenged group exhibited significantly higher antibody titers than sera collected before challenge. Histopathologic investigations in SPF birds showed deciliation and hyperplasia in Group NV and less-pronounced lesions in Groups Mass/Mass and Mass. In commercial broilers vaccinated with H120 alone, hyperplasia and deciliation were observed in 90% of the tracheas. These experiments illustrated that Mor-It02 is pathogenic for chickens and a combination of live H120 and 4/91 vaccines given respectively at Day 1 and Day 15 of age confer a good protection against Mor-It02.

Coronaviruses of the genus Gammacoronavirus cause major poultry diseases, including infectious bronchitis in chickens and enteritis in turkeys and guinea fowl. Until now, no enteric coronavirus distinct from infectious bronchitis virus had been reported in chickens. Between late 2024 and 2025, severe enteritis outbreaks affected broiler farms in southwestern France, causing increased mortality, wet litter, cyanosis, lethargy, ruffled feathers, and high slaughter condemnation rates. Necropsy and histopathology revealed diffuse enteritis and dehydration. Metagenomic sequencing identified abundant coronavirus reads as the only pathogenic viral signal. Whole-genome phylogeny showed a novel gammacoronavirus lineage closely related to guinea fowl coronavirus but distinct from infectious bronchitis virus and turkey coronavirus. Viral RNA was detected in enterocytes by RNAscope in situ hybridization, and electron microscopy revealed coronavirus-like particles. These findings describe a novel enteritis-associated coronavirus in broiler chickens (ChECoV), although the drivers of its host-range expansion into chickens remain to be elucidated.

Following the emergence of highly pathogenic avian influenza (H5N8) in France in early December 2020, we used duck mortality data of the index case to investigate within-flock transmission dynamics. A stochastic epidemic model was adjusted to the daily mortality data and model parameters were estimated using an approximate Bayesian computation sequential Monte Carlo (ABC-SMC) algorithm. Results suggested that the virus was introduced 4 days (95% credible interval: 3 – 5) prior to the day suspicion was reported and that the transmission rate was 3.7 day-1 (95%CI: 2.6 – 5.3). On average, ducks started being infectious 3.1 hours (95%CI: 0.4 – 8.0) after infection and remained infectious for 4.4 days (95%CI: 3.1 – 5.6). Model outputs also suggested that the number of infectious ducks was already 3239 (95%CI: 26 – 3706) the day before suspicion, emphasising the substantial latent threat this virus could pose to other poultry farms and to neighbouring wildlife. These estimations can be applied to upcoming outbreaks and made available to veterinary services within few hours. This study illustrates how mechanistic models can provide rapid relevant insights to contribute to the management of infectious disease outbreaks of farmed animals. Competing Interest Statement The authors have declared no competing interest.