The emergence of a highly pathogenic porcine reproductive and respiratory syndrome virus with additional 120aa deletion in Nsp2 region in Jiangxi, China

Highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS), which emerged in China in 2006, was characterized by high fever, high morbidity and high mortality. The causative agent of the disease was a highly pathogenic variant of porcine reproductive and respiratory syndrome virus (also called HP-PRRSV), which has a discontinuous deletion of 1 + 29 amino acids (aa) in the Nsp2 coding region, compared to classical PRRSV. In 2014, fattened pigs on a pig farm in Jiangxi Province suffered from clinical symptoms of high fever, dyspnoea and death. A PRRSV, termed JX2014T2, was isolated from samples of the dead pigs. Genomic analysis of the isolated PRRSV indicated that the genome of the virus was 14,960 bp in length and belonged to the North American genotype. In the Nsp2-coding region, there was a discontinuous deletion of 1 + 29 aa, similar to HP-PRRSV; however, an additional continuous deletion of 120 amino acids between aa 628 and 747 was found. Further analysis of the pathogenicity of PRRSV JX2014T2 was performed in piglets, and the results indicated that all infected piglets suffered from typical clinical symptoms of PRRS, such as high fever, cough, mental depression, anorexia, dyspnoea and palpebral swelling and died within 15 days postinfection (dpi). This demonstrated that the newly isolated PRRSV JX2014T2 strain containing an additional deletion of 120 aa is highly pathogenic to piglets, suggesting that a highly pathogenic variant with new genetic features is circulating in China.