| Pseudorabies(PR)is a kind of acute infectious disease caused bypseudorabies virus(PRV)in many domestic animals,which is characterized by fever,itching and encephalomyelitis.Pseudorabies virus is a double stranded DNA virus,belonging to Herpesviridae(subfamily alphaerpesvirinae),Varicellovirus(Varicellovirus)[1-9].Pig is the primary infection host of PRV.It can establish lifelong latentinfectioninpigs,Latent infected pigs are the potential source of pseudorabies,So,It is veryimportantto prevent PRV from establishing latent infection and to clear the infectedpigs.Inrecent years,the positive rate of pseudorabies virus infection in sows isrelativelyhigh.In order to prevent piglets from being infected with pseudorabies virus and turn positive,In thisstudy,we want to determine the first immunization time and optimize the immunization procedure from the aspects of the effect of emergency vaccination,thegrowth and decline of maternal antibody of pseudorabies in piglets and the timenodesof wildtype virus infection in piglets,so as to breed the negative reserve pigsand laythe foundation for the control and eradication of pseudorabies.Experiment 1 Study on the effect of PR clinical emergency vaccination In order to study the effect of emergency vaccination of Pseudorabies Vaccine,The samples of suspected pseudorabies cases were selected for PCR detection,sequencing,genetic evolution analysis of PRVg E gene and infection test of rabbits.The PRVg E antibody blocking ELISA test was performed on the blood samplescollected.The results of PCR test,antibody test and rabbit infection test showed that all the pigs were infected by PRVg E wild virus.The results of virus sequence analysis showed that,theisolates are in the same branch with the domesticstrains HN1201,QYY and JS-2012,and have close genetic relationship.There are two different branches of this strain,Becker,Kaplanand Kolchis,which are far from eachother.There was no new case after emergency inoculation of PR live vaccine onpigs threatened by PRV.The results showed that PRV infection and spreadcould be effectively prevented by emergency vaccination of PR vaccine in healthy pigs.Experiment 2 Study on the optimization of PR immune program In order to optimize the immune program of the breeding pig farm,the blood Samples of sows and their piglets were collected at 7,14,21,28,32,45,60,80 and 120 days.A comparative study on the effect of intranasal immunization on Piglets was carried out.The neutralizing antibody titer and PRVg B and PRVg E antibody and to study the growth and decline of maternal antibody and time node of PRVg E infection in the piglets of sows inoculated with Swine Pseudorabies Vaccine(SA215 strain).The results show that the antibody level of sows was high,the average titer of neutralizing antibody was 8log2,and all piglets obtained high level of maternal antibody.With the increase of age,the antibody level showed a downward trend and the titer of maternal antibody was 4.67log2 on 21 d,5log2 on28 d,3.33log2(<4log2)on 32 d,and 3.67log2(<4log2)on 45 d.The positive rate of PRVg B antibody in piglets were 100% at 7d,14 d,21d,28 d and 32 d.After that,the level of PRVg B antibody decreased with the increase of age,67% at 45 d and33% at 60 d.The results show that the effect of intranasal immunization was better than that of non intranasal immunization,the infection rate of PRV in the reserve pigs decreased,and the anti PRV infection ability increased.Taking into account the growth and decline of neutralizing antibody of PRV and the time node and the rate of positive transfer of wild virus infection in piglets,the procedure of vaccinating piglets against PR was determined as follows: Piglets were immunized by intranasal instillation for 0 days at a dose of 1 share;piglets were immunized by intramuscular instillation for 21 days at a dose of 1 share;piglets were immunized by intramuscular instillation for 60 days at a dose of 1 share.Experiment 3 Application of key technologies for control and eradication of Pseudorabies in large scale pig farms In order to further verify the applicationv effect of the key technologies of pseudorabies control and eradication in large-scale pig farms,five different pig farms were selected for validation and promotion.It is concluded that through the application of this integrated key technology of Pseudorabies control and eradication in large-scale breeding pig farms,it solves the respiratory diseases of PRV in pig breeds,controls the reproductive disorders of boars,reserve sows and sows after PRV infection,the PRVg E wild virus infection rate was reduced,and the PRVg E wild virus infection was prevented from turning into positive in the reserve pig group,and then the positive multiparous sows were eliminated to supplement the negative reserve pigs,so as to achieve the purpose of eradication of pseudorabies,the controland eradication effect of PR was significant. |
