Porcine Circovirus Type 2

Porcine circovirus (PCV) is a single-stranded DNA virus (class II), that is nonenveloped with an unsegmented circular genome. The viral capsid is icosahedral and approximately 17 nm in diameter. PCV is a member of the virus family Circoviridae. PCVs are the smallest viruses replicating autonomously in eukaryotic cells. They replicate in the nucleus of infected cells, using the host polymerase for genome amplification. There are 2 strains: type 1 and type 2. Porcine Circovirus Associated Disease is caused by porcine circovirus type 2 (PCV2). PCV-2 (first isolated in 1997) causes PMWS. However, viral infection by itself tends to cause only mild disease, and co-factors such as other infections or immunostimulation seem necessary for development of severe disease. For example, concurrent infection with porcine parvovirus or PRRS virus, or immunostimulation lead to increased replication of PCV-2 and more severe disease in PCV-2-infected pigs.