Prevalence and pathological characteristics of porcine circovirus-associated disease in pigs from Jeju

Abstract

Porcine circovirus type 2 (PCV2) has become a major viral pathogen in the swine industry as the causative agent of porcine circovirus-associated disease (PCVAD). This study aimed to investigate the prevalence and pathological characteristics of PCVAD in Jeju. For the period from 2003 to 2010, a total of 1,003 pigs submitted for diagnostic examination were reviewed, of which 313 (31.2%) were diagnosed as PCVAD. The most common clinical signs were wasting and respiratory distress such as dyspnea. Histopathologically, interstitial pneumonia and lymphoid depletion in lymph nodes were predominant lesions. Co-infection with porcine reproductive and respiratory syndrome virus was most frequently detected in PCVAD-affected pigs. Genotypic analysis using PCR revealed that PCV2a and PCV2b were detected in 44% and 98.7% of the examined cases, respectively. The proportion of PCV2b-positive pigs gradually increased from 2003 to 2005 and then remained nearly 100% until 2010, indicating the predominance of the PCV2b genotype in Jeju during this period. For the retrospective analysis of archival samples from 1994 to 1998, PCR examination of paraffin-embedded tissues confirmed that PCV2 antigens already existed in Jeju pigs as early as 1995. These findings suggest that PCV2 had been circulating in Jeju swine populations since the mid-1990s, and that PCV2b became the dominant genotype after the early 2000s. Continuous monitoring of genotype shifts is essential for understanding the epidemiology and control of PCVAD.