The Monitoring Of PRRSV Antibody Levels In Large-Scale Piggery And The Study Of PRRSV Attenuated Vaccine On The Immune Efficacy Of CSFV Vaccine

Porcine reproductive and respiratory syndrome which caused by porcine reproductive and respiratory syndrome virus is a infectious disease with the characteristics of reproductive failure, respiratory disease, and growth retardation in pigs, and leading to huge economic loss in swine industry worldwide. Monitoring the PRRSV antibody levels is quite necessary to prevent and control the disease efficiently. Meanwhile, the PRRSV can cause host immunosuppression which reduces the immune effect of vaccine. However, the main measure to prevent CSF efficiently is immunization in China. How to choose these two kinds of vaccines or combinate to use on clinic have always been concerns in swine industry.Experiment I, PRRSV antibody of serum samples were determined by enzyme-linked immunosorbent assay to monitoring the PRRSV antibody levels of pigs.4061serum samples were collected from five piggeries in three cities in Gangxi, among which there were2037collected in2011and2024collected in2012. The detection indicates that the average positive rate was73.6%(1500/2037), with the highest positive rate of94.9%and lowest of44.5%in2011; while the average positive rate was74.9%(1515/2024), with the highest positive rate of95.9%and lowest of50.0%in2012. The antibody levels have significant difference in different farms. The average positive rates in the farm Q and J without vaccination respectively were46.1%(378/820) and55.3%(575/1039), which indicates that the two farms had PRRSV infection. Whereas the highest average positive rates in the farms with vaccine or serum inoculation was95.9%and the lowest was84.2%, which indicated the two measures can offer enough protective efficacy.Experiment Ⅱ, fifteen piglets were raised under CSF virus (CSFV) and PRRSV free conditions and randomly distributed into three groups (n=5) at the age of28days. In group A, every piglet vaccinated with a classical swine fever modified-live vaccine. In group B, every piglet was vaccinated with PRRSV attenuated vaccine and the classical swine fever modified-live combo vaccine. The group C was negative control group. The vaccination was administered intramuscularly (i.m.) for all pigs. After vaccination, clinical manifestations and record the rectal temperature of all piglets were observed and recorded every day, every piglet carried on the first weighing when the trial period conclusion carried on a weighing again. The blood samples were collected on days0,7,14,21, and28post-vaccination. Serum samples from non-heparinized blood were used to measure the antibody titers against CSFV. The assay demonstrated that all pigs did not show any obvious changes in body temperature and clinical signs of PRRS or CSF throughout the experiment. The average daily gain has not significant difference (P>0.05) among three groups. There was no significant difference (P>0.05) was observed between group A and B in the CSFV antibody leves. That indicates vaccination of pigs with classical swine fever modified-live vaccine and in combination with the PRRSV attenuated vaccine at the same time, the PRRSV attenuated vaccine did not lead to immunosuppression to the immune response of pigs with classical swine fever vaccine.