Retrospective Study of Porcine Circovirus Type 2a and 2b Between 1999 and 2016 in Taiwan

Porcine circovirus type 2 (PCV2) is one of the major swine viral diseases and caused significant economic loss to pig producers worldwide, including Taiwan. PCV2 has been considered as the causative agent of postweaning multisystemic wasting syndrome (PMWS) as well as other clinical diseases. All these associated syndromes have been categorized as PCV2 associated diseases (PCVAD). The purpose of this study was to investigate the positive rate and genetic shift of two distinct genotypes of PCV2, which include PCV2a and PCV2b, in Taiwanese pig farms. A total of 1094 specimens originating from pigs between years 1999 and 2016 were analysed. The PCV2a and PCV2b sequences were amplified and distinguished using 1oop-mediated isothermal amplification (LAMP). Results showed that 24.8% (272/1094) pigs were PCV2a positive, 67.3% (737/1094) were PCV2b positive. These results also indicated that PCV2a was the predominant virus between 1999 and 2001, and that PCV2b became the most prevalent virus since 2003.