Evolutionary characterization and pathogenicity of Senecavirus isolated from Shandong, China

Senecavirus A (SVA), previously called Seneca Valley virus, belongs to the family Picornaviridae, species Senecavirus A, in the Senecavirus genus. SVA infection causes vesicular lesions in sows and a sharp drop in neonatal piglet production. In this study, an SVA strain, SVA/SD/2023, was isolated from a pig farm in North China, and its genome was determined and analyzed. PCR, immunofluorescence, and western blotting revealed that the SVA/SD/2023 strain stably promoted the proliferation of BHK-21 cells. Electron microscopy showed that the purified virus was an icosahedral particle of approximately 27 nm in diameter. The 7286-nucleotide (not including the poly-A tail) genome of SVA/SD/2023 presented typical picornavirus features, including a single open reading frame of 5836 nucleotides encoding a 1604-amino-acid polyprotein. The amino acid sequence of the SVA/SD/2023 strain was highly conserved (from 87.8% to 99.4% homology) with 47 reference strains isolated from different regions. Phylogenetic analyses revealed that the SVA/SD/2023 strain shared the highest sequence homology (99.4%) with the USA/IA46008/2015. Animal regression tests revealed that infected animals demonstrated reduced appetite, fever, and depression, among other negative effects. SVA did not cause animal death. Increased Senecavirus A VP2 and neutralizing antibody levels were detected in the infected animals, and viral loads decreased with increasing antibody titers. Interestingly, the specific damage caused by viruses varied among different routes of infection. This study provides basic information for the subsequent exploration of SVA pathogenic mechanisms and disease progression.