Evoluzione della biosicurezza avicola: indagine conoscitiva in un terrritorio della Regione Lombardia negli anni 2017-2025

Over the years, the regulatory framework governing poultry biosecurity has become progressively more stringent, in response to the changing epidemiological scenario linked to outbreaks of Highly Pathogenic Avian Influenza (HPAI), placing increasing demands for adaptation on both the production sector and the Veterinary Services. This process has been further complicated by the transformation of the poultry sector itself, with the emergence of small mountain enterprises and the spread of family-run (rural) holdings, which represent potential risk factors for the entire production system. The present study proposes a retrospective epidemiological analysis aimed at evaluating the temporal evolution of biosecurity levels in 134 poultry farms located in an area of the province of Bergamo, over the period 2017-2025, divided into four production sectors: meat poultry, layers, rearing farms and rural holdings. Compliance percentages for individual items on the official ministerial checklists were analysed using the tenth percentile (P10), employed as a dynamic critical threshold to identify, year by year, the 10% least-performing items, with a further distinction drawn between external and internal biosecurity measures. Results for the industrial sector show a progressive decline in the provincial P10 from 100% (2017) to 33.33% (2021-2024), which should not be interpreted as an actual deterioration in the field but rather as a "screening effect" linked to the expansion of the checklists (from 29 to 59 items), followed by a recovery to 50% in 2025. External biosecurity proved to be systematically more critical than internal biosecurity across all sectors, with predominantly structural weaknesses (proximity to water sources, natural ventilation, vehicle access) accompanied, in more recent years, by internal management shortcomings. The rearing sector emerged as the most vulnerable, with the P10 collapsing to 6.67% in 2025. The rural sector, assessed using a constant number of items over time, displayed a "bell-shaped" trend, with a marked improvement in 2021-2022 followed by a worrying decline in 2025. The study confirms the overall soundness of the biosecurity level achieved, while also highlighting how the P10 indicator represents an original and effective tool to support Veterinary Public Health, capable of isolating relative vulnerabilities even where absolute compliance levels are high. Future improvements in poultry biosecurity will depend not solely on the introduction of new regulatory requirements, but above all on the structural upgrading of farms, the strengthening of operator training, and the maintenance of continuous epidemiological surveillance, within an approach to biosecurity understood as a dynamic process rather than a static set of requirements.