Investigation And Control Of Pseudorabies Infection In Large-scale Pig Farms In Guizhou Province

Pseudorabies(PR),also known as Aujeszky’s disease(AD),which is a common,acute and highly contagious infectious disease caused by the Psudorabies virus(PRV).A variety of livestock and wild animals could be infected and characterized by fever,itching(excluding pigs)and encephalomyelitis.Pigs are the most common one as the only storage host for PRV.Most of the infection in adult pigs can cause recessive infection,with continuous detoxification and discharge and become the main source of infection.Infection of pregnant sows is mainly caused by reproductive failure such as abortion,stillbirth or mummy.The infection symptoms of piglets are the most serious with fever,vomiting or obvious nerve symptoms,and the death rate can up to 100%.Therefore,the occurrence of PR brings huge economic losses to pork production.Facing the new situation of pseudorabies,pig farms adopt different prevention and control strategies.At present,the use of gene deletion vaccine combined with detection and elimination method is one of the effective means to control the disease in large-scale pig farms.Due to the lack of relevant reports on the epidemiology of Guizhou,this study investigated the wild infection situation and distribution characteristics of the swine pseudorabies virus in Guizhou pig farms,and studied the growth and decline of immune antibodies in pigs with different population to improve biological safety and optimize the immunization procedures.This study also investigated the technical model of prevention to put forward comprehensive prevention and control measures,for the basis of the prevention and control of the disease and purification.First,in order to fully understand the prevalence of porcine pseudorabies in Guizhou area,by the gE-ELISA method,we investigated and systematically analyzed the epidemiology of wild PRV in 155 pig farms from the whole province,and established a suitable PR prevention and control schemes for some pig farms.The results are showed as follows: The positive rate of whole pig farms was 75.48%(117/155),and the positive rate of the total samples was 22.38%(477/2131).The positive rate of the pig breeding farm was64.29%(18/28)and the positive rate of the sample from the pig breeding farm was 30.81%(65/211);The positive rate of the immune piggery was 61.9%(13/21)and the positive rate of the samples was 36.30%(49/135).Besides that,1061 samples from 26 immune piggery weredetected by gE-ELISA and gB-ELISA,respectively.Their positive rates of pig farms were46.15%(12/26)and 100%(26/26),and the positive rates of samples were 5.75%(61/1061)and 60.79%(645/1061),respectively.In addition,a total of 179 tonsils from slaughterhouses were detected by fluorescent PCR and the positive rate was 0.56%(1/179).Our survey showed that the situation of pseudorabies virus recessive infection in pig farms in Guizhou was serious and there existed wild PRV infection.On the other hand,immune antibody was detected in immune piggerybut the positive rate of individual immune antibody is not high.For that,it may be the recessive virulence that affects the immune effect or the variation of the virus that influences the immune effect of the vaccine.In addition,we further studied the antibody growth and decline rule of PRV in Guizhou to monitor the immune status,and explore the vaccine’s rational immunization program to provide the basis for the prevention and control of the swine pseudorabies in the scale pig farms of Guizhou.The results in our present study showed that the high maternal antibody level in piglets greatly reduced the active immune effect of piglets after infected by wild venom.Further study showed that,under the background of negative maternal gE and gB antibodies,the piglets were immunized with gene deletion vaccine at D15 first and re-immunized at D45.The effective protective immune antibody was detected and gradually increased 15 days after the first immunization.The immune antibody level reached the peak one month after the 45 days of immunization.The effective protective rate reached 70% at the age of D120,which was suitable for the immunization program of commercial fattening pigs until pigs were released.Under the background of negative maternal antibody gE,sows were immunized 40 days before delivery,and live vaccines were given to newborn piglets after delivery.Gene deletion vaccines were firstly given at D50 and secondly at D80.The protective rate dropped to 70% when the maternal antibody lasted to 45 days.When live vaccine was inoculated at D50,its antibody would rise at D70.If strengthen the injection with gene deletion vaccine at D80,antibody will reach the peak at D120 and start to decrease at D150,then drop to 50% at D185,suitable for pig or the reserve sow.This study studied the rule of wild pseudorabies virus infection in large scale pig farms in Guizhou,and the study on the growth and decline of antibodies in different pig farmsprovided a data support for the formulation of immunization procedures in local large-scale pig farms.At the same time,some suggestions for the prevention and control of epidemic diseases in large-scale pig farms were put forward.This investigation will provide some references for the development of PR purification and eradication in Guizhou and even in the whole country.