Serosurvey Investigation And Countermeasure Of Prevention And Control Of PRRS In Chenzhou City

Porcine Reproductive and Respiratory Syndrome(PRRS) is a infectious disease caused by PRRS Virus(PRRSV), it can cause immune suppression and further lead to a secondary infection. The pandemic and great harm of PRRS brought a very serious economic losses to the pig farmers.The pathogen is still in variation and has not been eliminated effectively, the situation of prevention and control is still grim, and in some pig farms there are even had a trend of outbreak, so it is of a great importance to the development of big industry to do a epidemical investigation of the disease and a research on prevention and control measures.Research content and method:1.In2011-2012, we conducted ELISA tests to the PRRS antibody of3633serum samples from74pig farms in8counties of Chenzhou City, and made conclusions by analyzing the data that collected based on different regions, pig herds, immune situations and farming methods.2. we selected200postpartum14-day-old piglets from a pig farm in Guiyang County, Chenzhou City.The200piglets were divided into four groups, and immunized of highly pathogenic blue-ear live vaccine (the JXA1-R strain),the respective dose of the vaccine in1to4group was0.1head,0.2head,0.5head andl head per pig.20pigs per group were randomly selected to detect the antibody0day,7days,14days28days, and42days after the immunization, the growth situation was observed at the same time. Select800sows, divided into two groups (group1:immunization group; group2:control group). The sows in group1were immunized of highly pathogenic blue-ear live vaccine (the JX-A1strain) of0.5head per sow, while group2were1head per sow. Antibody detection were did at4th month and8th month after starting the immune, and statistical analysis the antibody status for each sow. Make a conclusion of proper immunization does of the pigs by comprehensive and comparative analysis of the antibody changes, survival rates, and production performance.Research results:1.The positive rate of antibody S/P>0.4of the8counties were between40.7%to90.3%, the positive rate of PRRSV antibody (S/P>0.4) of pig serum was relatively high in Yongxing County, Suxian District and Guiyang County, the values were90.3%,88.9%,85.2%. The value of S/P>2.5were between8.4%to25.3%, the positive rate of PRRSV antibody (S/P>2.5) of pig serum in Jiahe County was the highest(25.3%). The value of S/P>0.4in different herds were between67.0%to91.5%,and the gilts had a highest serum antibody S/P>0.4.The value of S/P>2.5in different herds were between8.3%to32.3%, the gilts had a highest serum antibody S/P>2.5, reach to32.3%, and fattening pigs reached to23.1%. The value of S/P>0.4in different immunization situation were between59.6%to90.2%, while the value of S/P>2.5were between6.4%to25.7%. The herds immunized with variant vaccine had the highest positive rate.the respective statistical results of positive rate of antibody S/P>0.4and S/P>2.5for the large-scale farms are86.3%and10.9%, while those for the backyard farms are60.8%and27.1%.2.The strain JXA1-R used with a dose of0.1-0.2head per pig got an ideal effect and showed no obvious clinical manifestations, while using a dose of0.5head per pig could lead to obvious clinical manifestations, and the mortality was6%higher. The positive rate S/P>2.5were respectively30.0%,2.3%and0%, showed an obviously decrease4month after the immunization. The positive rate S/P>2.5in the control group was between8.3%-15.6%. The production performance of sows in immunization group was obviously higher compare with those in the control group.Conclusion:1. The districts with higher serum antibody S/P>2.5also have a higher density of pigs, in these counties, the backyard farms were facing a more serious situation with PRRS, and the districts with a higher density of pig raise also had more risk of PRRS outbreak. The gilts and fattening pigs were more serious in infection. With more introduction and transport of the pigs, the PRRSV in farms became more active, especially in backyard farms, introduction without quarantine and monitoring, direct introduction into herds and gregarious, were the main reasons lead to the unstable of PRRSV. In addition, more attention should be pay to the dose of the vaccine when immunity, or it could cause a unstable of PRRSV in the herds.2. The strain JXA1-R used with a dose of0.1-0.2head per pig or the pathogenetic strain JXA1-R used with the dose of0.5head per pig was a proper immunization dose. A high dose of JXA1-R strain could lead to the unstable of PRRSV in the sows and a decrease in the production performance of the sows.