Isolation And Characterization Of Porcine Reproductive And Respiratory Syndrome Virus

In May 2006, A unknown severe pig disease designated "high fever" diseases occurred in many pig farms and subsequently spreaded over half of China. Infected pigs were highly contagious and high mortality rates,which more than 2 million pigs were infected and 400 thousand pigs were dead. The "high fever" disease has caused tremendous economic losses to the hog industry in China. In July, The disease appeared in Fujian Province, but spreaded rapidly . The pig samples which had the "high fever" symptoms were collected from the swinery in Fujian province. The suspected viruses isolation and identification were done from the samples. RT-PCR test was used to identify PRRSV.A porcine reproductive and respiratory syndrome virus (PRRSV) was isolated in a pig farm which had highly pathogenic and mortality rate for pigs. The biological characteristics were examined, which included cell growth characteristics, agglutination of red blood cells, and TCID50. In order to confirm the virulence, this isolate was inoculated healthy pigs which the PRRSV antibodies were negative by the nasal or intramuscular injection, and the healthy pigs were inoculated normal cell cultivation as a negative control group. The viral titers of nasal or injection challenge were 2.0 mL of virus cultures. The challenged pigs (6 piglets/group) were monitored daily for clinical signs. Viral isolation were recovered from those animals showing apparent clinical symptoms. Autopsies were performed for further examination of the pathological lesions. The results showed that the virulence of the isolate was highly than the general PRRSV, and the clinical symptoms of highly pathogenic PRRSV were different from that of general PRRSV, and the pathological changes were usually more obvious.10 specific primers were designed and synthesized to clone the ORF2～7 genes and NSP2 gene of this isolate. The T-vector cloning strategy was employed to generate the recombinant plasmid for sequencing. The results showed that there were 30 amino-acid deletion in NSP2 of the isolate, but the PRRSV was grouped into Northern American genotypes.