Monitoring And Analysis Of Clinically Prevalent Strains Of PRRSV In Anhui Province

Porcine reproductive and respiratory syndrome(PRRS)is a sow abortion,premature birth,stillbirth,and mummified fetus caused by Porcine reproductive and respiratory syndrome virus(PRRSV).Pigs at various stages are characterized by respiratory diseases and high mortality.Since the first report of PRRS in China,the disease has been epidemic and evolving for 20 years,especially in 2006,China's outbreak of highly pathogenic PRRS(HP-PRRS),causing huge economic losses to the pig industry.In 2008,the PRRSV variant NADC30 was isolated in the United States,and its Nsp2 protein has a discontinuous deletion of 131 amino acids.Since 2012,PRRSV NADC30-like with the same missing features has appeared in many provinces and cities in China,and has been reorganized with domestic PRRS V strains.PRRSV is highly variable,which leads to increased diversity of strains and different pathogenicity of different strains.This poses a huge challenge to the prevention and control of PRRS in China.In order to understand the prevalence and variation characteristics of PRRS in the past two years,and further explore the epidemic strains,investigate the clinical infection of PRRSV in Anhui from 2017 to 2018 and monitor the clinical epidemic strains to understand the pig population in Anhui.The characteristics of PRRSV and the incidence of infection were in control of the prevalence of PRRSV clinically prevalent strains in pigs in Anhui,thus providing basis and support for scientific,rational and effective prevention and control of PRRS in Anhui.In this study,we used the real-time fluorescence quantitative RT-PCR method to detect and identify PRRSV in the case of suspected PRRSV(dead)pigs with clinical symptoms of respiratory symptoms and reproductive disorders in the period from 2017 to 2018,and serum,saliva and semen.To determine the infection status;on this basis,real-time quantitative RT-PCR detection was used to identify PRRSV as an American-type classical strain,or HP-PRRSV,or PRRSV NADC30-like,or American-type strain;for undetermined strains The unidentified strain type was verified by amplification and sequencing of the PRRSV ORF5 gene and the Nsp2 partial gene.The results showed that a total of 416 samples were sent to 16 cities in Anhui,and 223 positive PRRSV samples.The positive detection rate was 53.6%.The PRRSV test results of different types of samples,different regions,different quarters,different stages and different clinical symptoms were statistically analyzed.The positive detection rates of PRRSV in diseased tissue and saliva were 56.8%and 58.8%,respectively,which were significantly higher than serum.And semen;PRRSV infections existed in 16 cities in Anhui,the positive detection rate was between 26.7%and 77.0%;the positive detection rates of PRRSV from the first quarter to the fourth quarter were 72.3%and 64.5%,respectively.55.6%,36.5%,no significant difference;the positive detection rates of PRRSV in different growth stages(dead and weak,nursery,fattening pigs)were 29.2%,69.0%,46.3%,respectively,the difference was not significant;clinical manifestations were The positive rate of PRRSV in respiratory symptoms was 65.6%,which was significantly higher than the positive detection rate of reproductive disorders by 29.2%.Among the 223 PRRSV positive samples,the positive detection rate of American classic strains was 19.7%,the positive detection rate of HP-PRRSV was 44.8%,and the positive detection rate of PRRSV NADC30-like was 13.0%.The positive detection rate of the strain was 22.4%,and the positive detection rate of HP-PRRSV was the highest.Four different types of strains were detected in different types of samples,different regions,different quarters,different growth stages and different clinical symptoms of PRRSV strains,mainly HP-PRRSV.The results showed that the positive detection rate of PRRSV in Anhui area was 53.6%in 2017-2018,which was more serious in the country;the detection rate of PRRSV was the highest in the disease tissue and saliva samples,and the PRRS in Anhui did not show obvious season.Sexual and regional,pigs in each stage of growth can be infected with PRRSV,and the clinical symptoms are mainly respiratory symptoms.At present,the dominant strain of PRRS in clinical practice is HP-PRRSV;the prevalence of PRRSV strains varies regionally,but it is not related to seasonality.Different types of samples and PRRSV detection dominant strains in different growth stages are different,causing The strains with reproductive disorders are more common in HP-PRRSV,while the strains causing respiratory diseases coexist.