Epidemiological Investigation And Purification Of Swine Fever And Swine Pseudorabies In Large Scale Swine Farms

Classical swine fever?CSF?and Pseudorabies?PR?are two important diseases affecting pigs.The Ministry of Agriculture classified swine fever as a class of animal diseases in 2008 and pseudorabies as a class II animal disease.These two diseases are currently present.In China,some large-scale pig farms are widespread,which directly or indirectly affects the sustainable and healthy development of China's pig industry.In recent years,with continuous breakthroughs and innovations in CSF and PR diagnostic technologies and comprehensive prevention and control measures in China,and the maturity of CSF and PR purification technologies,the purification of CSF and PR in large-scale pig farms has been included in the Middle and long-term Animal Disease Control Plan?2012-2020?.In order to further explore and improve the scientific and feasible purification programs for CSF and PR in large-scale pig farms,this study will monitor and purify the established pig farm swine fever and swine pseudorabies treatment program in large-scale pig farms.In addition,epidemiological investigations of CSF and PR on large-scale pig farms and isolation and identification of pathogens were conducted under the conditions of purification.In order to provide some reference for the prevalence,variation,prevention and control and purification of CSF and PR in large-scale pig farms in the later period.1.Serological investigation of swine fever and swine pseudorabies in scaled pig farmsIn order to better implement the CSF and PR purification programs,ELISA tests of CSF and PR antibodies were performed on 1 430 blood samples taken from a large-scale pig farm in Guizhou prior to the implementation of the plan.The results showed that PRVs were the samples tested.The positive rate of gB antibody was87.2%?1 247/1 430?.The positive rate of PRV gB antibody in breeding pigs,reserved pigs,nursery pigs and finishing pigs were all above 85%.The positive rate of PRV gE antibody was 4.48%?46/1 430?;the positive rate of PRV gE antibody detected in nursery herds was the highest,being 5.26%?12/228?,and the lowest positive rate in finishing pigs was 4.14%?11/266?.The positive rate of swine fever antibody was84.27%?1 205/1 430?.The positive rate of swine fever antibody antibody in breeding pigs,reserved pigs,nursery pigs and finishing pigs was all above 80%.The results of this study provide background investigations for the purification of large-scale CSF and PR in the later period,and provide reference for the epidemic situation of CSF and PR in Guizhou.2.Investigation of the etiology of CSFV and PRV in swine farmsIn order to master the infection status and corresponding pathogenic characteristics of CSFV and PRV in large-scale pig farms,mPCR and single PCR/RT of CSF and PR were performed on 1 430 tonsil and blood samples collected from a large-scale pig farm before the implementation of the project in Guizhou Province.-PCR detection and identification of CSFV and PRV in PCR/RT-PCR positive samples.The results showed that the positive rate of pathogenic rabies virus in pigs was 1.96%?28/1 430?.A pig pseudorabies virus was successfully isolated and named as Guizhou-T1 strain.The strain was inoculated with Vero cells in blind passage to the third passage and began to produce CPE.The passage from the blind passage to the fifth passage showed stable CPE with a TCID₅₀0 of 10^-10.11/100?L.The electron microscope showed an oval,capsule,and diameter.For 120-180 nm virions,the inclusion of viruses in the nucleus appears to be in the form of a lattice;virus infiltration after filtration of the virus causes itching and paralysis in rabbits.The positive rate of pathogenic nucleic acid of swine fever virus was 2.59%?37/1 430?.The highest positive rate of wild pigs in the nursery was 3.07%?7/228?.A swine fever virus was isolated and identified as GZA strain.After the strain was inoculated with PK-15 cells,continuous transmission of 7-generation RT-PCR could amplify positive bands of CSFV E2 gene.Indirect immunofluorescence assay showed that CSFV did proliferate in PK-15 cells;virus particles were elliptical or circular under electron microscopy with diameters of 30-80 nm.The results of the study preliminarily figured out the pathogenic characteristics of PRV and CSFV in large-scale pig farms,and provided a baseline survey for the purification of CSF and PR in large-scale pig farms in the later period.3.Epidemiological survey of molecular CSFV and PRV in large-scale pig farmsTo understand the molecular epidemiological status of CSFV and PRV in a large-scale pig farm in Guizhou province,this study tested the cloning and sequencing of CSFV E2 and PRV gE genes in the positive CSFV and PR partial samples from the large-scale pig farms.And sequence analysis.The results showed that the gE gene homology of the 4 PRV Guizhou epidemic strains was 99.6%-99.9%,the amino acid homology was 99.1%-99.8%,and the Guizhou-T1-T4 strain had aspartame in positions gE48 and gE496.Insertion of acid?Asp D?;phylogenetic tree shows that the gE gene sequence belongs to the same branch as the mutant strain reported after 2011.The Guizhou-T1 strain shared 97.5%and 99.3%homology with the GZ-Z1 strain and the Guizhou-DY strain,respectively;there were 8 amino acid mutation sites between the Guizhou DY strain and 26 strains between the GZ-Z1 strain and the Guizhou DY strain.Amino acid mutation sites.The nucleotide homologies of the CSFV GZA strain and GZB strain E2 gene and the reference strain CSFV E2 gene were 82.8%-83.4%,and the amino acid homology was 88.7%-90.6%.There was a significant difference between the E2 gene and the reference strain of the CSFV Guizhou isolate.This study provided a reference for genetic variation of CSF and PR in large-scale pig farms in Guizhou.4.Study on purification effect of swine fever and pseudorabies in scaled pig farmsIn order to study the application effect of the purification plan for swine fever and swine pseudorabies in large-scale pig farms,the trial collected 4 programs to implement 1,776 tonsil and 1 776 blood samples from the farm,using the established CSFV RT-PCR test.Technology?GB/T 16551-2008?,PRV gE/gB-ELISA detection method?GB/T 18641-2002?and the laboratory established mPCR method for identifying wild swine fever and swine pseudorabies wild virus and vaccine virus,A purification study was conducted on CSF and PR in a large-scale breeding farm in Guizhou Province.The purification of CSF and PR in a large-scale pig farm in Guizhou province was conducted in four phases.The results showed that the PRV gB antibody positive rate increased from 83.98%?367/437?to 98.17%?429/437?after the purification protocol was implemented;the PRV gE antibody positive rate dropped from 5.72%?25/437?to 0.23%?1/437?;The positive rate of pathogenic rabies in pigs decreased from 2.75%?12/437?to 0;the positive rate of swine fever antibody increased from 85.81%?375/437?to 98.63%?431/437?;the pathogenicity of swine fever was positive.The rate dropped from 2.06%?9/437?to 0,indicating that the use of this purification scheme has achieved the expected results for the purification of pig farm swine fever and swine pseudorabies.The study provided a certain reference for purification ideas of pig farms and swine pseudorabies in large-scale pig farms.