Epidemiological investigation on the latent infection with porcine reproductive and respiratory syndrome virus in Hebei Province

To investigate the latent infection status of porcine reproductive and respiratory syndrome virus(PRRSV) in Hebei Province,1 565 samples of lung or lymphonodi pulmonales from 228 slaughterhouses were tested for highly pathogenic porcine reproductive and respiratory syndrome virus(HP-PRRSV) and classical porcine reproductive and respiratory syndrome virus(C-PRRSV) by RT-PCR,respectively.In result,the positive rate of PRRSV in the slaughterhouses was 41.58%.The positive rate of HP-PRRSV was 12.08%,and the yearly positive rates were 28.45%,40.74%,12.01% and 7.31% from 2006 to 2009,respectively.The mean of C-PRRSV-positive rates were 2.36%,and the yearly positive rate was 3.45%,3.70%,3.90% and 1.46% from 2006 to 2009,respectively.Co-infection of PRRSV with other pathogens was also detected,which was mainly double or triple infection,and the co-infection rates of PRRSV,HP-PRRSV,C-PRRSV with other pathogens were 59.73%,57.67%and 43.24%,respectively.HP-PRRSV and C-PRRSV were not detected from the same sample.In summary,the latent infection of PRRSV,especially HP-PRRSV,was wide spread in pigs in Hebei Province,which deserves more attention.