Pathogenicity and antigenic characterization of a novel highly virulent lineage 3 porcine reproductive and respiratory syndrome virus 2

Abstract

Background/purpose: Porcine reproductive and respiratory syndrome virus (PRRSV) is a pathogen with a negative economic impact on the global swine industry. In 2019, a suspected highly pathogenic strain, NPUST-108-929/ 2019 (108–929), was isolated from a pig farm in Pingtung with an outbreak of high mortality and analyzed. The characteristics of PRRSV 108–929 have barely been studied. Methods: This study was to evaluate pathogenicity through animal challenge experiments using PRRSV 108–929 and antigenic characterization of this novel PRRSV. Results: This PRRSV strain is PRRSV 2, belonging to lineage 3 based on open reading frame 5 sequence analysis. Four putative N-linked glycosylation sites (N32, N35, N44 and N51) are located on glycoprotein 5. Experimental results revealed that high fever occurred at 3 days postinoculation (dpi) in the high-titer inoculation (HIN) group (2 × 104 TCID50/mL), 8 dpi in the high-titer contact (HC) group, 4 dpi in the low-titer inoculation (LIN) group (2 × 103 TCID50/mL) and 9 dpi in the low-titer contact (LC) group. All pigs in each PRRSV 108–929 challenge and contact group showed severe clinical signs, such as high fever (>40.5 ◦C) and significant weight loss. Deaths occurred only in the HIN group; the survival rate was 60 %. All the piglets except the control group piglets showed high viremia titers (6.04–8.28 log10 copies/μL). Conclusion: The pathogenic characteristics of PRRSV 108–929 suggest that it is a highly virulent PRRSV strain at both the farm and laboratory levels.