Detection And Complete Genome Sequencing Of Porcine Circovirus Type 2 In Different Pig Herds

Porcine circovirus type 2 (PCV2) is a small non-enveloped single-stranded circular DNA virus classified in the Circoviridae family. PCV2 was identified in pigs with various disease syndromes, such as PMWS, PDNS and PRDC. PMWS is an immunosupressive disease characterized by progressive weight loss and multisystemic pathological lesion in the 6-8 week-old piglets. PCV2 was first identified in China in 2000, and since then, the distribution of PMWS has spread in all over country, caused significant economic losses and present a threat to the pig industry. But there was no reported about the detection of PCV2 and the evolution of the genetic diversity in pigs without PMWS. This study included as following:1. According to the published genome sequence of Porcine circivirus type 2(PCV2), two pairs of primers were designed and a nested PCR assay was developed to detect PCV2. The results showed that a 647bp gene fragment was obtained by the outer pair of primers, and 219bp was amplified by the inner pair of primers. After optimizing the amplification conditions of PCR, 10^-5mg/mL DNA of PCV2 could be detected by the first amplification, and 10^-8pg/mL DNA could be detected by the second amplification, which sensitivity being increased by 1000 times. Among 85 disease samples of piglets with clinical signs, 51 samples were positive to PCV2 by nested PCR, meanwhile, 39 samples were positive to PCV2 by conventional PCR. It indicated that PCV2infection is common in DeZhou of Shandong province.2. PCV2 in the 826 clinical samples from ten provinces and 146 healthy samples from five shambles, were detected with nested PCR. The results showed that the numbers of positive samples were 316 for the clinical samples and 64 for the healthy samples, and the average positive detection rate was 38.3% and 43.8%. It indicated that PCV2 infection was prevalent in the tow different pig herds.3. PRRSV,PPV and CSFV in the 283 PCV2 positive samples from nine provinces except Gansu province, were detected with PCR assay. The results showed that the...