Epide Miogical Investigation Of PRRVS In Guangdong Province From 2014-2016 And Genetic Variation Analysis Of NADC30-LIKE

To analyze the prevalence of PRRSV in Guangdong Province in recent three years,1120 tissue samples and 5046 serum samples were collected from large-scale pig farm in Guangdong Province from 2014 to 2016.Antigen test data showed that positive rate of PRRSV were 38.6% 、31.6% and 31.6% in 2014 to 2016,respectively.The positive rate of PRRSV was the highest in 2014,slightly decreasing in 2015,and rebounding in 2016.At the same time,the antigen detection data were analyzed on a quarterly basis and month basis.The results showed that there were significant differences in the positive rates of antigens in the same quarter of different years and in the different quarters of the same year,as well as in the the same month of different years and in the different quarters of the same year.The antibody test data of recent three years showed that the positive rate of PRRSV were 83.5% 、64.1% and 63.1% in 2014 to 2016,respectively.The positive rate of PRRSV antibody was gradually decreased.At the same time,the antibody detection data were analyzed on a quarterly basis and month basis.The results showed that there were significant differences in the positive rates of antibody in the same quarter of different years and in the different quarters of the same year,as well as in the the same month of different years and in the different quarters of the same year.According to the regional division,in the year of 2014,the antigen positive rate of PRRSV was the highest in the western of Guangdong and the lowest in the eastern of Guangdong.In 2015,the antigen positive rate of PRRSV was the highest in the northward of Guangdong,and the lowest in the eastern of Guangdong.In 2016,the antigen positive rate of PRRSV was the highest in the northward of Guangdong,and the the lowest in the Pearl River Delta of Guangdong.The results showed a trend of decreasing firstly and then rising in the Pearl River Delta of Guangdong.The antigen positive rate of PRRSV was gradually decreased in the western of Guangdong.The antigen positive rate of PRRSV showed a trend of decreasing first and then rising in the eastern of Guangdong.The antigen positive rate of PRRSV showed a trend of rising firstly and then decreasing in the northward of Guangdong.The antibody test results showed that,in 2014 year,the antibody positive rate of PRRSV was the highest in the eastern of Guangdong,and the lowest in the western of Guangdong.In 2015 year,the antibody positive rate of PRRSV was the highest in the eastern of Guangdong,and the lowest in the Pearl River Delta of Guangdong.In 2016 year,the antibody positive rate of PRRSV was the highest in the western of Guangdong,and the the lowest in the eastern of Guangdong.The antibody positive rate of PRRSV showed a trend of decreasing first and then rising in the Pearl River Delta of Guangdong.The antibody positive rate of PRRSV was gradually decreased in the western of Guangdong.The antibody positive rate of PRRSV was gradually decreased in the eastern of Guangdong.The antibody positive rate of PRRSV was gradually decreased in the northward of Guangdong.Genetic phylogenetic trees analysis of PRRSV ORF5 gene showed that 40 strains belonged to subtype I represented by JXA1.Thirteen strains belonged to subtype II represented by HB-1(sh)-2002.Only one strain belonged to subtype IV represented by VR-2332.Fifteen strains belonged to subtype VI represented by GM2.The results showed that PRRS strains were mainly represented by JXA1 in Guangdong.In this study,nine PRRSV isolates were analyzed for genomic,ORF3,ORF4,O RF5,ORF6,ORF7 and Nsp2.The results showed that the genomic,ORF3,ORF4,ORF5,ORF6,ORF7 and Nsp2 genes of the nine PRRSV isolates were all on the branch of JXA1 strain.The Nsp2 amino acids of the nine PRRSV isolates presented a deletion of 30 amino acids at positions 481 and 533-561,indicating that the nine PRRSV isolates were PRRSV mutants.The O RF5 gene and Nsp2 gene of 10 PRRSV strains detected in large-scale pig farms in Fujian,Henan and Hebei provinces were analyzed.The results showed that the ORF5 gene and Nsp2 gene of the 10 PRRSV strains belonged to the NADC30 branch and there is a characteristic deletion of 131 amino acids at 323aa-433 aa,481aa and 533aa-551 aa.