Features of the epizootic process and ways to improve measures to combat avian flu

1. This study examined the dynamics of the 2019-2023 avian influenza (AI) outbreak on large-scale poultry farms in Russia and explored the management factors associated with morbidity levels.2. Six industrial poultry farms were included in the study, with repeated observations taken annually. Data on AI morbidity and mortality, biosecurity practices, vaccination coverage and virus sub-type distribution were collected from veterinary surveillance reports and farm health records. Descriptive statistics were used to summarise morbidity and mortality levels across intervention periods. Welch's t-tests and non-parametric tests were used to compare morbidity and mortality rates before and after the introduction of enhanced control measures in 2021.3. Correlation analysis evaluated the relationship between morbidity and mortality. Linear regression models examined the associations between management factors and morbidity levels. Temporal changes in virus sub-type distribution were analysed using chi-squared tests.4. Morbidity rate fell from 11.6% prior to the intervention period (2019-2020) to 8.9% following the implementation of enhanced control measures (2022-2023), while the mean mortality rate decreased from 5.8% to 4.2%. Regression analysis revealed a significant association between higher vaccination coverage and lower morbidity levels.5. Biosecurity indicators were significantly related to morbidity variation across farms. Temporal analysis revealed significant changes in the distribution of sub-types, with H5N1, H5N8 and H9N2 detected throughout the observation period.6. These results suggested that integrated disease control strategies are associated with improved management of AI in large-scale poultry production systems. The observed reductions likely reflected a combination of farm-level interventions and broader national and ecological trends.