Detection of porcine circovirus 2 in mammary and other tissues from experimentally infected sows

The aim of this study was to determine whether porcine circovirus 2 (PCV2) may infect the mammary gland of sows and be shed in the milk. Six pregnant sows were inoculated intranasally with PCV2 three weeks before their expected farrowing date and two further sows acted as uninfected controls. The animals remained clinically healthy and farrowed normally. Milk samples were collected from all sows on the first, second and third days of lactation. PCV2 DNA was detected in the milk of infected sows from day 1 of lactation but not in the milk of uninfected controls. PCV2 antigen and DNA were detected in the mammary gland and other tissues by immunohistochemistry and in-situ hybridization, respectively. Simultaneous detection of viral protein and DNA provided molecular evidence of PCV2 infection and replication within these tissues.