Molecular Epidemiological Investigation Of Porcine Reproductive And Respiratory Syndrome Virus In Sichuan

Porcine reproductive and respiratory syndrome is caused by Porcine reproductive and respiratory syndrome virus (PRRSV), which can cause some clinical features such as fever, abortion, the high mortality rate of piglets and respiratory disorders of different ages for pigs. In this study, epidemiological investigation, clinical observation and necropsy were conducted in part of pig farm which was suspected high pathogenic PRRSV. The lung, lymph nodes, spleen were also collected from diseased pigs which were used for the amplification of Nsp2and ORF5gene by RT-PCR. The sequences were analyzed for the variation of recently prevalent PRRSV in Sichuan province.From epidemiological survey, the high pathogenic PRRSV was spread widely in Sichuan province which means in total of126samples were detected as PRRSV positive. And also the infected pigs showed classical PRRSV clinical symptoms. From the necropsy result, it was showed that most of PRRSV positive pigs were co-infected with the other pathogen.8Nsp2gene and17ORF5gene were obtained by RT-PCR. The sequence analysis revealed that these Nsp2gene shared97.2%-100%nucleotide and91.5%～100%amino acid identity to each other,75.3%～77.0%nucleotide and58.3%～60.8%amino acid identity with VR2332,42.9%-43.7%nucleotide and20.2%-20.6%amino acid identity with LV strain. Compared with some Chines isolates previously in2006(CH-1A,HB-1,HB-2), they showed75.2%～88.6%nucleotide and58.7%～79.2%amino acid identity. At the same time, compared with some Chines isolates which were identified as high pathogenic PRRSV strains (HUN4, JX2006, JXwO6-81c, WUH1), they showed 94.8%～97.1%nucleotide and92.8%～94.8%amino acid identity. Meanwhile, the obtained17ORF5gene shared94.7%～100%nucleotide and85.4%～100%amino acid identity to each other,86.6%～88.7%nucleotide and69.6%～74.7%amino acid identity with VR2332,63.9%～65.1%nucleotide and77.2%～93%amino acid identity with LV strain. Compared with some Chines isolates previously in2006(CH-1A,HB-1,HB-2), they showed90.1%～96.6%nucleotide and95.6%～99.4%amino acid identity. At the same time, compared with some Chines isolates which were identified as high pathogenic PRRSV strains (HUN4, JX2006, JXwO6-81c, WUH1), they showed94.8%～97.1%nucleotide and88%～96.8%amino acid identity. This result showed that all the obtained sequence belong to North American and had a big mutation with the standard strain, but had a high identity rate with Chinese high pathogenic PRRSV strains.In terms of sequence analysis with obtained strains and standard strains from GenBank, all the Sichuan strains belong to PRRSV subgroup Ⅲ, and stay in the same brand with high pathogenic strains (HUN4, JX2006, JXwO6-81c, WUH1), which meant that they maybe come from the same original stain.