Diagnosis of a Large Number of Death Cases of Newborn Piglets and Isolation and Identification of HP-PRRSV

The assay was aimed to provide theoretical references for the prevention and control of newborn piglet epidemic diarrhea which was characteristic of high morbidity and mortality.An outbreak of newborn piglet epidemic featuring diarrhea,emesis and lassitude was reported in January 2013 in a large-scale pig farm in Yulin,Guangxi province.The morbidity and mortality in the epidemic were 80% and 80% to 100%,respectively.To identify the causes,ten samples of small intestines,spleens,lungs and lymph glands were collected for the bacterial isolation,PCR,virus isolation,determination of TCID₅₀,gene sequencing and analysis.The detection results showed that PEDV and PRRSV were positive while those of CSFV,PRV,TGEV and PRoV were negative.No pathogenic bacteria were isolated.Clone and sequence results of ORF7 and Nsp2 genes of the isolate indicated that the isolate was an American PRRSV,with ORF7 of 372 bp (123 amino acids) and Nsp2 of 2 850 bp (950 amino acids).There was a discontinuous deletion of 30 amino acids of Nsp2 gene at sites 481 and 532 to 560,which was consistent with Nsp2 of highly pathogenic PRRSV JXA1,so the isolate could be determined as a HP-PRRSV strain.48 h after Marc-145 cells being inoculated by pathological sample,the typical CPE of PRRSV appeared,and TCID₅₀ of PRRSV isolate was 10^-5.75/0.1 mL.The newborn piglet epidemic diarrhea was caused by PEDV infection and HP-PRRSV subsequent infection.