First detection of NADC34-like porcine reproductive and respiratory syndrome virus strains in Japan

Porcine reproductive and respiratory syndrome virus (PRRSV) is an important pathogen in the swine industry. We report for the first time the detection of NADC34-like PRRSV strains in Japan. Serum samples from 18 piglets in Okinawa Prefecture were analyzed for the open reading frame 5 (ORF5) gene encoding glycoprotein 5, which revealed that all samples belonged to sublineage 1.5 (L1A) of Lineage 1. Phylogenetic analysis, restriction fragment length polymorphism patterns, and glycosylation site characteristics confirmed the presence of NADC34-like strains that caused severe outbreaks in the U.S. and Asia. Despite its known pathogenicity, the farm showed only a transient increase in mortality. These findings highlight the need for further investigation into the pathogenicity of PRRSV strains and their potential for the emergence of new variants in Japan.