Study of Swine Influenza Virus circulation in the Italian pig population: chasing the variability of an endemic virus

Swine influenza viruses significantly threaten animal and human health, as exemplified by the 2009 H1N1 pandemic. Pigs are particularly susceptible to infection by various influenza strains due to their ability to bind both avian and human influenza virus receptors. This characteristic makes them ideal "mixing vessels" for viral reassortment, a process that can lead to the emergence of novel viruses with pandemic potential. Understanding swine influenza viruses’ genetic and antigenic evolution is crucial for predicting and preventing zoonotic transmission. Swine influenza infections not only impact animal health and welfare but also have significant economic consequences for producers. Infected pigs experience reduced growth performance, increased production costs, and decreased reproductive performance. Comprehensive biosecurity measures, including strict hygiene, controlled animal movement, and vaccination, are essential for effective swine influenza control and prevention. This work had the purpose of analyzing widely the influenza A viruses circulating in the Italian pig population: at a National level: describing first the circulation of IAVs in the Italian pig population, examining the viral strains detected recently from 2017 to 2020 and their source of introduction; in epizootic and enzootic forms, in combination with other pathogens, through the monitoring of influenza virus circulation in pig farms in Northern Italy for three years, 2021-2023, focusing on viral and bacterial co-infections combining active and passive monitoring; in the wild boar population: describing the viral subtypes detected from active surveillance in Northern Italy; at the farm level: A longitudinal study was performed on two pig farms to examine circulation dynamics among groups of animals before and during the farrowing stage, evaluating vaccination as an IAV control strategy.