Study On Control Of Porcine Reproductive And Respiratory Syndrome Virus NADC30-like Strain Infection Via Vaccination Scheme

Porcine reproductive and respiratory syndrome(PRRS)has spread worldwide,causing severe economic losses to the pig industry.PRRS is characterized by reproductive disorder in late pregnancy,premature birth,stillbirth foetus,and respiratory symptoms in piglets.Porcine reproductive and respiratory syndrome virus(PRRSV)is highly susceptible to mutation,prevention and control of PRRS have increased difficulties.At present,NADC30-Like PRRSV strains have been detected in many provinces of China,especially the rate of Henan is up to 50%.The infection and prevalence of NADC30-like strain poses a greater challenge to the prevention and control of PRRS,and no control scheme has been found.In this study,we aim at investigating the immunization control program for NADC30-like PRRSV strain.This research composed of two parts experiments,the clinical infection background of the experimental pig farms and infected by NADC30-like strain confirmed through gene sequencing was one part.120 sows of second-trimester age and above were selected from the farms and divided into four groups: attenuated vaccine immunization group,inactivated vaccine immunization group,attenuated vaccine and inactivated vaccine combined immunization group and non-immunization group,then the abortion rate of sows,the number of mummies,stillbirths,live piglets and antibody levels before and after immunization were comparatively counted.Finally,400 piglets aged 14 days were selected from the fields and divided into four groups: attenuated vaccine immunization group,inactivated vaccine immunization group,attenuated vaccine and inactivated vaccine combined immunization group and non-immunization group,the daily gain,incidence and casualty of piglets under four different immunization projects were counted and we make statistical analysis of these data.Combining with the changes of antibody levels before and after immunization,the different vaccination schemes were formulated based on serology and clinical production.Another part is to re-screen the experimental pig farm and re-evaluate the effect of different schemes.The results showed that: the combined immunization groups with attenuated and inactivated vaccine were superior to the attenuated vaccine immunization group and inactivated vaccine immunization group in eight groups of sows.The antibody level of the combined immunization group was the highest,the fastest and the production performance improved was the most obvious.In the eight groups of piglets tested,the combined immunization group was superior to the attenuated vaccine immunization group and inactivated vaccine immunization group,and the antibody level was the highest and fastest,and the production performance was the most significant.In summary,the combined immunization of attenuated vaccine and inactivated vaccine is an effective way to control NADC30-like infection.