A 5-Year Review of Senecavirus A in China since Its Emergence in 2015

Abstract

Senecavirus A (SVA), previously known as Seneca Valley virus, is classified into the genus Senecavirus in the family Picornaviridae. This virus can cause vesicular disease and epidemic transient neonatal losses in swine. Typical clinical signs include vesicular and/or ulcerative lesions on the snout, oral mucosa, coronary bands and hooves. SVA emerged in Guangdong Province of China in 2015, and thereafter gradually spread into other provinces, autonomous regions and municipalities (P.A.M.s). Nowadays more than half of the P.A.M.s have been affected by SVA, and asymptomatic infection has occurred in some areas. The phylogenetic analysis shows that China isolates are clustered into five genetic branches, implying a fast evolutionary speed since SVA emergence in 2015. This review presented current knowledge concerning SVA infection in China, including its history, epidemiology, evolutionary characteristics, diagnostics and vaccines.

Keywords: China; diagnostics; epidemiology; phylogenetic analysis; senecavirus A; vaccines.

Figure 1

Characteristics of Senecavirus A. Transmission electron microscopy of purified SVA virion (a). Schematic representations of SVA virion: front (b) and section (c) views. Schematic representation of SVA genome (d). Cleavage sites (arrow-headed) within SVA polyprotein (e). Typical cytopathic effect, cell rounding, at 24 h post infection with SVA (f), and non-infected cell monolayer as mock (g). Plaque formation (arrow-headed) of SVA-infected cell monolayer (h). Multi-step growth curve (MOI = 0.001) of rescued SVA CH-LX-01-2016 cultivated in BSR-T7/5 cells (i). IRES, internal ribosome entry site; 3C^pro, 3C protease; RS, ribosomal skipping; ?, unknown.

Figure 2

Clinical signs of pigs infected with Senecavirus A in Fujian Province of China in 2017. Fluid-filled vesicles on snout (a, red arrow) and coronary bands (b,c, red arrows). Ruptured vesicle with ulceration and erosion beneath the toe (d, red arrow), and lesions on dewclaws (d, yellow arrowheads). Adapted from the reference (23) with permissions of the Elsevier (License No.: 4892830654384).

Figure 3

Geographical distribution of Senecavirus A-affected and -free P.A.M.s in China during 2015 and 2019. P.A.M, province, autonomous region and municipality.

Figure 4

Phylogenetic analysis on genomes of SVA isolates. The Neighbor-joining method and Kimura-2-parameter model were used for construction of the phylogenetic tree using MEGA 7.0 software. Numbers indicated the bootstrap value (1,000 replicates). SVA isolates from China, the USA, Canada and other countries were marked with “,” “,” “,” and “,” respectively.