First detection of porcine circovirus type 3 on commercial pig farms in Poland.

Porcine circovirus type 3 (PCV3) is a novel circovirus species recently discovered in USA and China in cases of porcine dermatitis and nephropathy syndrome, reproductive failure, respiratory disease and multisystemic inflammation. This study reports on the first identification of PCV3 in Europe, in serum from pigs from Polish farms. A total of 1,050 serum samples were collected between 2014 and 2017 from sows and 3-20 weeks old pigs from 14 commercial farms representing different regions of Poland, different size and health status. The samples were pooled by 4-6 and tested with real-time PCR for PCV3. PCV3 DNA was detected in 12 of 14 farms (85.7%). On the PCV3-positive farms, the virus was detected in 5.9% to 65% serum pools. PCV3 was most common among weaned pigs and finishers (26.1% and 28.0% of serum pools, respectively). Sequence analysis of 359 nucleotide fragment of ORF2 showed highest identity of 99.7% to PCV3-US/SD2016 from USA. Our results indicate that PCV3 is a common virus among Polish pigs but no links to unexplained disease conditions were established.