The occurrence of porcine circovirus 3 without clinical infection signs in Shandong Province.

Porcine circovirus type 3 (PCV3) was detected in Shandong, China. One hundred and thirty-two of 222 (59.46%) samples were PCV3 positive, while 52 of 132 (39.39%) samples were co-infected with PCV2. There were no clinical signs of infection in either multiparous sows or live-born infants. Two strains of PCV3 were indentified from natural stillborn foetuses. Phylogenetic analysis showed the two strains of PCV3 are 96% identical to the known PCV3/Pig/USA (KX778720.1, KX966193.1 and KX898030.1) and closely related to Barbel Circovirus. Further studies of the epidemiology of PCV3 and the co-infection with PCV2 are needed.