Porcine circovirus type 2 is one of the most widespread and economically relevant infections of swine.
Four genotypes have been recognized, but currently, only three (PCV2a, PCV2b and PCV2d) are effectively
circulating. The widespread livestock trade and rapid viral evolution have contributed to determining the
high heterogeneity of PCV2 and the dispersal of potentially more virulent strains. Italian swine farming
and the related processing industry are relevant in the national economy. Despite the noteworthy losses
associated with direct and control measure costs, no data are currently available on the molecular epidemiology
of PCV2 in Italy. Our study, which was intended to fill this gap, considered 75 completed genome
PCV2 sequences, which were obtained from samples collected from the highly densely populated
area of Northern Italy between 2007 and 2014. Phylogenetic analysis and comparison with reference
sequences demonstrated the co-circulation, with different prevalences, of PCV2a, PCV2b and PCV2d
within the national borders, with PCV2b being the most prevalent. Recombination between different
genotypes was also proven to be frequent. Phylogeographic analysis demonstrated that the marked variability
of Italian PCV2 strains can be attributable to multiple introduction events. The comparison of the
phylogenetic analysis results, the location of different haplotypes and the international commercial routs
of live pigs allow the speculation of several links as well as the role of Italy as both an importer and exporter
of PCV2 haplotypes, mainly from and to European and Asian countries. A similarly intricate contact
network was demonstrated within national borders, with different haplotypes being detected in the same
province and different provinces harbouring the same haplotype. Overall, this paper represents the first
description of PCV2 in Italy and demonstrates that the high variability of circulating Italian strains is due
to multiple introduction events, wide circulation within national boundaries and rapid viral evolution.