Impact of Vaccination Against Influenza A (H1N1)pdm09 Virus on Key Reproductive Performance Indicators in a Subclinically Infected Sow Herd

Abstract Even though viral replication and typical clinical symptoms of the infection in pigs are exclusively limited to the upper and lower respiratory tract, there have been case reports demonstrating correlation of IAV with reproductive health issues in sows, probably related to the effect of cytokines. The trial was conducted in a subclinically infected high-performing 8,000-head sow herd immunised against the influenza A (H1N1)pdm09 virus using RESPIPORC FLUpan H1N1 (Ceva Santé Animale, Libourne, France). The aim of this longitudinal field investigation was to evaluate the alterations in key reproductive performance indicators (i.e. abortion rate, return to oestrus rate, farrowing rate, and number of piglets born alive, stillbirths, and born weak per litter) before and after implementation of the vaccine. A significant improvement in selected indicators was achieved. After implementation of the vaccination against the influenza A (H1N1)pdm09 virus, the mean abortion rate decreased significantly ( p =0.0025) in site A, whereas it remained unaffected in Site B. The return to oestrus rate increased significantly ( p =0.0091) in Site B only (2.23% to 2.97%). The mean number of piglets born alive increased significantly at both locations ( p <0.0001), reaching 17.7 animals per litter in each. The mean number of weak piglets born per litter was not significantly affected. Analysis of the number of mummified and stillborn piglets revealed a significant reduction of these parameters at both locations. The mean farrowing rates were not significantly altered by the vaccination. The findings highlight the role of less obvious problems affecting porcine reproduction.