Frequency and Genetic Analysis of Porcine Circovirus Type 2, Which Circulated between 2014 and 2021 in Jiangsu, China.

Simple Summary: Porcine circovirus type 2 (PCV2) is currently the smallest known animal virus, and the diseases caused by its infection have caused huge economic losses to the pig farming industry worldwide. The virus evolves rapidly and is divided into nine genotypes, some of which pose significant challenges in preventing and controlling the disease. In this study, the polymerase chain reaction technique and bioinformatic analysis were used to investigate PCV2 infection in pig farms in Jiangsu Province, China. The results showed that the infection rate of PCV2 in pig farms in Jiangsu Province has been increasing annually, with genotypes PCV2a, PCV2b, PCV2d, and PCV2i. The genomic characteristics of the recently confirmed genotype PCV2i were elucidated. Porcine circovirus-associated diseases, caused by porcine circovirus type 2 (PCV2), are widespread and result in significant economic losses to the global swine industry. PCV2 can currently be divided into nine genotypes (PCV2a to PCV2i), with the currently dominant one being the PCV2d genotype. In this study, 2675 samples from 804 pig farms in 13 cities in Jiangsu Province, China, were collected between 2014 and 2021 and subjected to polymerase chain reaction analysis to investigate the frequency and genetic diversity of PCV2. The results showed that 41.42% (1108/2675) of samples tested positive for PCV2. The researchers further analyzed the genetic characteristics of 251 PCV2 strains and found that they belonged to the following four genotypes: PCV2a, PCV2b, PCV2d, and PCV2i. The dominant genotype was PCV2d, with a frequency of 49.80% (125/251). The detection rate of PCV2b was significantly higher than those of PCV2a and PCV2i, at 35.46% (89/251), 7.57% (19/251), and 7.17% (18/251), respectively. The percentage of different genotypes of PCV2 varied irregularly over time. We have further revealed the fingerprint of PCV2i genomic nucleotides for the first time. In conclusion, this study illustrates the high frequency and evolutionary features of PCV2 in Jiangsu Province over the past few years. [ABSTRACT FROM AUTHOR]