Prevalence of PCV2 in Austrian and German boars and semen used for artificial insemination

Since epidemiologically-based science on PCV2 in porcine semen is patchy, we investigated 806 Austrian (A) and German (G) AI boars from five studs, and boars from Austrian farms used for on-farm semen collection, for the presence for IgG/IgM in blood by ELISA (n=754) as well as for PCV2 DNA in semen (n=472) and if positive, also in blood of a few boars by nested PCR and sequencing. A total of 420 boars were tested for both PCV2 in semen and antibodies in blood. Boars were aged between 8 and 82 months at sampling. None of the boars tested positive for IgM but 60.1% did for IgG. PCV2 DNA was detected in 86 (18.2%) semen samples. Minor differences were found between boar populations with respect to the number of antibody positive boars and no differences for DNA in semen. Phylogenetic analysis of 28 sequences revealed a genetic diversity of PCV2 in semen within and between boar populations, with sequences belonging to both PCV2 genotypes 1 and 2. Mean nucleotide sequence identity was 95.7%, with maximum pairwise difference of 8.8%. Boars < or =16 months were tested more frequently positive for IgG (P<0.001) and for PCV2 DNA in semen (P<0.05) than older boars. Of 80 boars tested positive in semen, 34 (42.5%) were antibody negative. A total of 58 semen positive boars with (n=33) and without (n=25) IgG were all tested negative for PCV2 DNA in serum. In conclusion, this study demonstrated the ubiquity of PCV2 in the Austrian and German boar population. Genetically diverse PCV2 can be encountered in boar semen. Shedder boars cannot be detected on the basis of serology. There is an apparent possibility of PCV2 being transmitted through semen.