| This study separated a virus from swine farms,which was identified as the foot and mouth disease virus Asia I by using cell culture,electron microscope,serology neutralization technology and sending to Lanzhou Institute of Veterinary,national foot and mouth disease reference laboratory for identification.By ultracentrifugation,virion with a diameter of about 25-30nm can be observed in the electron microscope.The suckling mice treated with FMDV Asia I standard blood serum were live and others were dead.A pair of primers was designed according to the complete gene sequence of FMDV Asia I in GenBank to amplify capsid protein VP1 gene and the gene of 1012bp was amplified.The gene sequencing showed cDNA of VP1 of this strain was in size of 633nt and having a GC contents of 59.56%.The VP1 gene homology of this strain versus other strains reported in China was 82.0%-99.2%,and that versus strains reported abroad was 82.9%-98.4%.Sequence homology comparison showed that this strain does not belong to the four genotypes reported at 2001.China's FMDV Asia I mainly have two different prevailing genotypes,which are Genotypesâ…£before 2006 such as Gansu 1,Yunnan,and the new genotype reported after 2006 including this isolation.The comparison showed the VP1 amino acid sequence of this strain has two mutations in the 149(Pro)and 154(Asp) respectively which was not reported in other papers.In this research,seventy sows and seventy piglets were randomly divided into seven groups,each group having 10 sows and 10 piglets(group1-3:inoculated FMDV Asia I-O association vaccine;group4-6:inoculated FMDV Asia I vaccines;group 7:inoculated FMDV O vaccines),the former two treatments were each inoculated for 3 different immunization doses which was normal dose,1.5 times of normal dose and repeated inoculation at 15 days after normal dose.Each group was fed equally,and serums were separated from ears' intravenous blood at the time of inoculating,7d,15d,30d,60d,90d,120d after vaccination.The antibody efficacy was examined by means of liquid-phase blocking enzy-linked immunosorbent assay(LPB-ELISA),which is recommended by the OIE.In view of vaccination doses,the result showed that sows treated with 1.5 times of normal dose and piglets inoculated repeatedly at 15 days after normal dose having more antibody efficacy;in view of different vaccines,the result showed that the antibody efficacy induced by FMDV Asia I vaccine was higher than that of FMDV Asia I-O association vaccines;in view of the antibody efficacy of FMDV O,the result showed the difference of antibody efficacy was not significant between FMDV O group and FMDV Asia I-O group.The statistics on the number of pigs that were immuno-protected showed that inoculated with FMDV Asia I-O association vaccine,70% of sows and 60%of piglets were protected;inoculated with FMDV Asia I vaccine,83%of sows and 73%of piglets,were protected.Antibody monitoring results indicated that around 15 days after immunization swine show a maximum antibody titer,which then drop gradually;besides repeated immunization can enhance antibody efficacy when antibody is less than 4.0.According to results of the trial,FMDV Asia I vaccine is recommended for the first immunization;1.5 times of normal dose for first immunization and an enhancement on the 120th day for sows, normal dose for first immunization and enhancements on 15th and 120th days respectively for piglets are also recommended. |
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