Update on Senecavirus Infection in Pigs

Abstract

Senecavirus A (SVA) is a positive-sense single-stranded RNA virus that belongs to the Senecavirus genus within the Picornaviridae family. The virus has been silently circulating in pig herds of the USA since 1988. However, cases of senecavirus-associated vesicular disease were reported in Canada in 2007 and in the USA in 2012. Since late 2014 and early 2015, an increasing number of senecavirus outbreaks have been reported in pigs in different producing categories, with this virus being detected in Brazil, China, and Thailand. Considering the novel available data on senecavirus infection and disease, 2015 may be a divisor in the epidemiology of the virus. Among the aspects that reinforce this hypothesis are the geographical distribution of the virus, the affected pig-producing categories, clinical signs associated with the infection, and disease severity. This review presents the current knowledge regarding the senecavirus infection and disease, especially in the last two years. Senecavirus epidemiology, pathogenic potential, host immunological response, diagnosis, and prophylaxis and control measures are addressed. Perspectives are focused on the need for complete evolutionary, epidemiological and pathogenic data and the capability for an immediate diagnosis of senecavirus infection. The health risks inherent in the swine industry cannot be neglected.

Keywords: Seneca Valley virus; emergent disease; neonatal mortality; picornavirus; swine; vesicular disease.

Figure 1

Lesions associated with senecavirus infection. (A) Fluid-filled vesicles on the snouts of senecavirus-positive sows. (B) Ulcerative lesions on the foot of a three-day-old piglet (left) and diphteric gengivitis in a one-day-old piglet (right), both positive for senecavirus.

Figure 2

Senecavirus global distribution from 1988 up to early 2017.

Figure 3

Evolutionary relationships of senecavirus strains identified in the USA, Canada, Brazil, China, and Thailand from 1988 to 2016. Phylogenetic tree constructed with 56 partial (541 bp) nucleotide sequences of the VP1 region of senecavirus genome. Year of sample collection and GenBank accession numbers for each senecavirus strain are presented within the tree. The evolutionary history was inferred using the Neighbor–Joining method [44]. The percentage of replicate trees in which the associated senecavirus strains clustered together in the bootstrap test (1000 replicates) are shown next to the branches [45]. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method [46] and are in the units of the number of base substitutions per site. Evolutionary analyses were conducted in MEGA7 [47].