Case analysis on the prevention and control of PRRSV NADC30-like based on PRRSV inactivated vaccine

In January 2018,a large-scale abortion occurred in sows in a pig farm in Yulin region, Guangxi Province. The inguinal lymph nodes of newborn piglets turned blue and purple, and the mortality rate reached more than 15%;nursery pigs began to develop fever one week after weaning, with obvious respiratory symptoms and high mortality 20%. In order to diagnose the disease of pigs on the pig farm, the experiment used RT-PCR to determine the pathogen of the infection and analyze its genetic evolution. Based on the diagnosis results, a vaccine immunization and drug treatment plan was formulated and implemented. The effect of the comprehensive prevention and control program was evaluated by the production performance indicators(such as the number of litters within 6 months, average litter size per litter, average healthy litter size per litter, piglet mortality rate in delivery room, and morlality rate of mursery piglets),monitoring the PRRSV pathogen by fluorescent RT-PCR methods, and antibodies in the sow’s serum. The results showed that the pathogen causing reproductive disorders in sows on the farm was PRRSV. Sequencing and genetic evolution analysis of its ORF5 and Nsp2 genes, the sequencing strain was named GXYL 2018, the virus strain and the PRRSV NADC30 2012 strain were on the same evolutionary branch, and the qenetic similarity was 91.7% and 90.6% respectively. After immunization with PRRSV inactivated vaccine and drug treatment programs, sows in the farm showed no symptoms of reproductive disorders. The PRRSV positive rates and antibody dispersion in the serum of sows, gilts and boars decreased by 64.16,48.19,80.00 percentage points, and 38.43,14.76,23.97 percentage points respectively. The number of healthy litters per sow litter increased by 1.61,and the mortality rates of farrowing room and nursery decreased by 9.72 and 10.02 percentage points respectively. The results suggested that PRRSV inactivated vaccine immunization and drug treatment can be used for the comprehensive prevention and control of sow reproductive disorders caused by PRRSV NADC30-like strain.