A cluster of farms experiencing severe porcine circovirus associated disease: Clinical features and association with the PCV2b genotype

The objective of this study was to characterize the clinical, histopathological, and virological features of an outbreak of severe porcine circovirus associated disease (PCVAD) on four farms located in the same geographical region of Kansas. The outbreak of PCVAD was evident by increased mortality and the appearance of postweaning multisystemic wasting syndrome, porcine dermatitis and nephropathy syndrome, and neurological signs. Whole porcine circovirus type 2 (PCV2) genomes were derived by sequencing polymerase chain reaction (PCR) products amplified from tissues. Nucleotide differences between North American and European isolates were used to construct a genotype-specific PCR assay for detection of different genotypes. Genetic sequencing of PCV2 from 12 PCVAD-affected pigs showed that all viruses were associated with the PCV2b genotype and were distant from historical PCV2a isolates. Routine virus isolation from tissues of PCVAD-affected pigs yielded both PCV2a and PCV2b viruses, as well as a porcine teschovirus.The identification of PCV2b in Kansas is consistent with the increased incidence of both severe PCVAD and variant PCV2 genotypes worldwide. The ultimate source of the PCV2b virus within the production systems studied remains unclear. Genotype-specific PCR assays provide new tools for understanding the contributions of PCV2a and PCV2b viruses to PCVAD.