Epidemiological Survey Of Porcine Reproductive And Respiratory Syndrome In Some Farms In Shanxi Province

Porcine reproductive and respiratory syndrome(PRRS)is a kind of sow reproductive and respiratory stage caused by Porcine reproductive and respiratory syndrome virus(PRRSV).Respiratory diseases are characteristic of viral infections that seriously affect the global swine industry.They are commonly known as "blue ear disease" in China.The disease has been in North America and Europe for more than 30 years.It has been popular in China for more than 20 years.So far,it has not been effectively controlled on a global scale,and the impact and harm to the pig industry still exist.In this trial,from September 2016 to January 2019,6518 serum collected from large-scale pig breeding sites in 8 provinces of Shanxi Province were tested for PRRSV in serum using PRRSV ELISA kit(IDEXX).The level of antibody,comprehensive analysis data found that: 8 vaccines used in pig farms are Nannong high-tech inactivated vaccine,of which 5385 positive samples(S / P ≥ 0.4),the positive rate was 82.62%,S / P > 2.5 The sample was 514,which accounted for 7.89%;the collected 6518 sera were divided into different regions,the positive rate ranged from 0.00% to 92.39%,and the highest positive rate in Yuncheng A area was 92.39%,the lowest positive rate in H area of Shuozhou City is 0.00%,and the ratio of S/P>2.5 in serum samples in different regions is 0.00%-14.85%.Among them,the ratio of S/P>2.5 in the E area of Luliang City is the highest.For the case of 14.08%,the S/P>2.5 in the H area of Shuozhou City is at least 0.00%;the serum collected from each pig farm in 8 areas is divided into different time periods,and the positive rate of pig farms in the A area of Yuncheng City The highest is 84.38%-100%,and the proportion of S/P>2.5 is 2.05%-49.35%.The positive rate of antibody in pig farm is 0.00%,the proportion of S/P>2.5 is 0.00%,and the proportion of S/P>2.5 in pig farm in F area of Shuozhou City is 0.00%-61.54%,and the positive rate is 33.33.%-100%.The above data indicates that the PRRS immune effect in Shanxi Province is not ideal,and some pig farms have PRRSV infection.This study provides an effective theoretical basis and scientific basis for the diagnosis and monitoring of PRRS in Shanxi Province.Classical PRRSV,HP-PRRSV,NADC-like strains were classified by RT-PCR according to the two pairs of primers available in our laboratory.,and 19 samples collected from free-range household pig farms in different regions of Shanxi Province from 2018 to 2019.For the test,the free-range PRRS vaccine was not tested in the free-range pig farms.The results showed that there were 4 positive samples with a positive rate of 21.1%.Among them,sample No.3 was a NADC30-like strain,and samples No.6,8,and 10 were classic strains.It is speculated that the prevalence of PRRSV genotypes in Shanxi Province is mainly dominated by classical strains,but existing NADC30 strains have become popular.MARC-145 cells were inoculated with samples of NADC30-like cells for virus isolation,and RT-PCR identification showed successful separation.One strain of NADC30-like strain was obtained.ORF5 gene encodes PRRSV GP5 protein.Due to the high variability of structural protein GP5,domestic and foreign scholars have used the variation of ORF5 gene as an important marker to analyze the prevalence of PRRSV.In order to understand the prevalence and variation of PRRS in Shanxi Province,this experiment The ORF5 sequences of 4 positive strains from 19 samples collected from the free-range household pig farms in different areas in Shanxi Province from 2018 to 2019 were amplified,sequenced for genetic evolution and homology analysis,and the results showed that The strains were prevalent.The sub-subgroups represented by CH-1a and the sub-V subgroup represented by NADC30,respectively,are presumed to be the classical strains of PRRSV strains in Shanxi Province,and the NADC30 strains are prevalent.GP5 of PRRSV epidemic strains has different degrees of variation,so it is necessary to carry out continuous detection of PRRSV epidemic and mutation,in order to prov Ide a scientific reference for clinical diagnosis and disease prevention and control.In summary,through the serological investigation and molecular epidemiological survey of pig farms in some areas in Shanxi Province in recent years,the overall immune effect of PRRS in Shanxi Province is not satisfactory,and some pig farms have been infected with PRRSV.The main epidemic strains are classical strains,but some NADC30 strains have become popular.This experiment provides a theoretical basis and reference basis for the control and prevention of porcine reproductive and respiratory syndrome in Shanxi Province and the purification in the early stage.