Understanding the dynamics and evolution of swine influenza viruses in Europe - relevance for improved intervention and sustainable pig production - SE2217

Pig production has grown dramatically worldwide over the last 20 years, leading to increased herd sizes, higher replacement rates and weekly production cycles of piglets. This has resulted in a constant flow of susceptible animals, providing an optimal environment for swine influenza A virus (swIAV) circulation and diversification. Thus, the dynamics of swIAV are changing globally from acute respiratory outbreaks to self-sustaining continuous infection of affected herds. Stable environmental conditions contribute to uninterrupted virus circulation in pigs, while the possibility of both transmission of seasonal human influenza virus to pigs, and transmission of swine viruses from pigs to humans remains a genuine risk. Since the 2009 influenza pandemic, caused by a reassortant IAV of swine origin, the predominant swIAVs in Europe include this pandemic H1N1 (H1N1pdm) lineage and the formerly enzootic lineages, avian-like swine H1N1 and human-like reassortant swine H1N2 and H3N2 lineages, with relative frequencies varying geographically. Concurrent exposure of pigs to different swIAVs and human IAVs increases the probability of genomic reassortment. Most often, the new reassortants emerge sporadically, but novel circulating swIAVs have also been detected regionally. Moreover, an increasing number of emerging antigenic variants have been described, although antigenic drift in swIAVs has historically been regarded as minimal, most likely through lack of surveillance. Thus, the genetic and antigenic diversity of swIAVs in European pig populations has dramatically increased in recent years, possibly driven by changes in rearing conditions, but this has not been systematically investigated. This research grant is supported by a co-fund between the EU and ICRAD/ERAnet and includes a consortium of six partner European countries. APHA will be the lead and major contribution to WP2 focussing on the genetic and antigenic evolution of swine influenza A viruses in European pig herds. WP2 will develop workflows for a unified genetic and antigenic characterization of swIAVs identified. Data will be integrated to relate the pig host and production system to virus evolution, genotype patterns, antigenic relatedness (including use of cartography), disease dynamics and potential mitigation points. The project incorporates three scientific work packages. Longitudinal studies will be implemented in selected herds typical for the production systems that face continuous swIAV infections in each partner country. They will provide epidemiological, virological and immunological data, while the diversity of swIAV strains identified will be studied at the genetic and antigenic levels. Mitigation points will be identified, linking viral diversity to production systems where possible. Potential control strategies will also be evaluated. APHA will be the lead and major contributor to WP2, which will investigate genetic and antigenic evolution of swIAVs in European pig herds.