Molecular Epide Miology Of PRRSV And PCV In Several Provinces Of South China

In recent years,the swine industry in in Several Provinces of South C hina is booming.Porcine Reproductive and Respiratory Syndrome Virus(PRRSV),Porcine C ircovirus Type 2(PCV2),and Porcine C ircovirus Type 3(PCV3)are still serious important pathogens for the swine industry and continue to cause enormous economic losses.In this study,molecular epidemiology and genetic evolution analysis of PRRSV,PCV2 and PCV3 in in Several Provinces of South C hina were conducted.The main research contents are as follows.About PRRSV study,a double RT-PCR method for simultaneous detection of the ORF5 gene of North American and European PRRSV was established and applied to molecular epidemiological survey of PRRSV.The results showed that there were 62 North American PRRSV positive samples(6.47%),10 European PRRSV positive samples(1.04%)and 5 North American PRRSV/European PRRSV co-infection samples(0.52%)were detected.The results also showed that 19 strains belonged to subgenotype 4,6 strains belonged to subgenotype 5,1 strain belonged to subgenotype 6,and 1 strain belonged to a new subgenotype 7.Among them,1 strain(CH/GDY DZZZ/ 2016)with 3-nucleotide deletion in ORF5 region was isolated,and its genome was 15304 bp in length.Moreover,15 strains of European PRRSV were analyzed.The results indicated that 15 European PRRSV strains were all divided into pandemic subgenotype 1,but had their unique variation and further clustered three small branches.About PCV2 study,162 positive samples(16.91%)were detected by conventional PCR.PCV2 was further detected by differential PCR,the positive samples of PC V2 ae is 14(1.46%)and PCV2 bcd is 48(5.01%).9 PCV2 genomes were amplified from those positive samples.The phylogenetic analysis showed that 4 of 9 isolates belonged to PC V2 b,4 belonged to PCV2 d and 1 belonged to PCV2 a.Interestingly,1 strain had a close relationship with Buffalo1,and 1 strain had a close relationship with RN1.While other 2 strains were closely to RN2 and Buffalo3,and 1 was closely related to JS2015.The results showed that the genome sequence similarity was 95% ~ 100% and 94.3% ~ 99.8%,respectively,compared with these 9 strains each others and some domestic or overseas isolates and vaccine strains.About PCV3 study,15 positive samples(1.56%)were detected by conventional PCR,1 positive sample was from Jilin in 2016,and 13 positive samples were from Gua ngdong during 2013~2016.Among those positive samples from Guangdong,3 samples were from the Pearl River Delta region in 2013 and 2014,respectively,while 3 and 5 samples were from western Guangdong in 2015 and in 2016,respectively.Two complete genome sequences of PCV3 were obtained and they had 2000 nucleotides in length.The whole genome sequence analysis showed 98.7% ~ 100% nucleotide similarity with the reference strains from mainland C hina and abroad,and the point mutation of GDBL32013 ZSJ strain nucleotide sequence only occurred at positions 223 and 330.For the ORF1 sequence,nucleotide similarity was 99.6% with each other,and 99.2% ~ 99.7% with the other reference strains.The amino acid similarity of O RF1 was 99.3% with each other and 99.0% ~ 100% with other reference strains.Compared with amino acid sequences,the results showed that only the strain GDBL32013 ZSJ changed at position 75 from H to Y.For the ORF2 sequence,nucleotide sequence similarity was 97.7% with each other,and 97.7% ~ 99.5% with other strains.The mutations of GDBL32013 ZSJ strain occurred at amino acid positions 75,147,153,207,270,469,564 and 594,but at amino acid positions 12 and 33 for CCZS2016.Their amino acid sequence similarity of ORF2 was 98.6%,and 98.1% ~ 100% with the others.The amino acid sequence alignment results showed that only GDBL32013 ZSJ strain changed from A to T at amino acid position 157.