Practices Of Prevention And Clearance On Porcine Reproductive And Respiratory Syndrome In One Industrial Farm

Porcine blue-ear disease,also known as porcine reproductive and respiratory syndrome(PRRS),is a highly infectious disease caused by porcine reproductive and respiratory syndrome virus(PRRSV),which causes fever and anorexia,abortion,stillborn fetus and mummified foetus farrowed in pregnant sows,respiratory disorders in pigs of all ages(especially piglets).At present,PRRS is available in pig countries around the world.Since PRRS came to mainland in 1995,the disease has a high incidence in China.In 2006,the occurrence of highly pathogenic porcine reproductive and respiratory syndrome virus(HP-PRRS)caused great economic loss to Chinese swine industry.In recent years,new strains of PRRSV have been found in China successively,such as NADC30-like,GM2,for which there has no specific drug therapy.Integrated measures of prevention and control are mainly taken to limit it.The fundamental way to control PRRS is to purify pigery and area.In this research,through artificial active infection(serum domestication)and blocking pig herd,a large-scale propagation field(PRRS negative into a positive PRRS)converted virus positive to negative,which provide reference to making effective measures to control and eradication.1.Diagnosis of porcine reproductive and respiratory syndrome and identification of strain typeRT-PCR was used to detect PRRSV in lung tissues of diseased pigs,and PRRSV antibody was detected in serum of piglets,replacement gilt and sows by ELISA.PCR products of GP5 gene were cloned,recombinant,identified,sequenced and analyzed by molecular biology technology to determine the type of strain infected with PRRSV.The result shows that,PRRSV was detected in the lung tissues of dead pigs.Thirty-four PRRSV antibodies were detected in 85 serum samples,with a total positive rate of 40%,an average antibody S/P value of 0.43 and a dispersion of 75.2%.The critical antibody S/P value of 0.43 and a total of 19 positive serum samples of piglets were detected.The antibody S/P value of 0.43,a positive rate of 47.5%(19/40),an average antibody S/P value of 0.42 and a dispersion of 52.7%.The backup pigs were 0 and all were negative..Sows antibody level S/P value:0.51,the positive rate is 50%(15/30),the average antibody S/P value is 0.45,the dispersion is 71.8%.The amplified GP5 gene sequence(coded AHChen-20162017)was 64.7%-67.0%similar to the European type strain,86.1%similar to the American type representative strain VR-2332,97.4%similar to the HP-PRRSV highly pathogenic representative strain JXA1,and 93 5%similar to the domestic classic strain CH-1a.the similarity with the American variant NADC30-like strain(NVDC-R244-2014,NVDC-Hebl-2011)was 98.1%,and it was in the same branch with NVDC-R244-2014.2.Serum domestication,detox cleanse,close group monitoring and assessment of cleaning efficiencyFirst,determine the optimal positve serum dilution concentration according to the result of RT-PCR.The sample would be inoculated after dilution.After inoculation,pigery segregated and dosing group monitoring.During this period,the closed group of pigs had been continuously monitored about PRRSV pathogen,antibody and piglets,backup the production,the growth performance of pigs and sows.The results showed that the optimal dilution concentration of serum domestication was 1:200.650 sows,2mL/head,1400 piglets,0.5ml/head,1500 reserve pigs and 2mL/head were intramusculally injected.Then,The time of group management was 200 days.Lung samples were detected at 4,8,11,20 and 28 weeks after group closure.The pathogen of PRRSV was negative at the 20th and 28th week,and the positive rate of PRRSV antibody in serum was positive at the 20th and 28th week.The average S/P value of antibody decreased to 0.10 at 28 weeks,and 200 sows died at 2 weeks and 3 weeks.After the death rate dropped to 50,the number of deaths per week gradually declined and stabilized after 14 weeks,while sows gave birth to stillbirths.The number of live offspring,delivery rate and abortion of mummy fetuses were within the normal range after 20 weeks.The mortality rate of piglets declined gradually after the first 11 weeks of high and low mortality.In the 20th week,it reached the lowest point of 5.4%.After that,the overall situation remained stable and good This practice made the pig farm realize the purification of PRRSV,and the PRRS positive was changed to negative again.