Evidence of PRRSV recombination from field samples in northeastern Italy

Recombination of different PRRSV strains has been reported both in vitro and in vivo. However field evidences of recombination are rare and mainly obtained comparing sequences from large-scale sampling (i.e. countries). This work investigates this phenomenon on a smaller scale using 213 samples (serum and lung) originating from three regions of northeastern Italy, collected during 2009-2012. The presence of rapid and effective transmission of moderately different strains between farms creates appropriate conditions for co-infection to occur, justifying the high number of recombination events recorded. Further studies and field sampling should be devoted to demonstrate the effect of recombination on viral fitness and pathogenicity, providing further insight in the still highly debated role of recombination on PRRSV evolution.