LAUSR

Simple Summary Swine erysipelas caused by the Erysipelothrix rhusiopathiae occurred frequently among pigs in Japan mostly by the serovar 1a variant featured by two amino acids in the surface protective antigen A protein. To determine if current vaccines are effective against the variant infection in pigs, one inactivated vaccine, SER-ME containing serovar 2a as the immunogen, was representatively evaluated. All vaccinated pigs survived without any apparent clinical signs after lethal challenge with the Fujisawa reference strain or the variant. This indicates that the serovar 2a immunogen of SER-ME vaccine effectively protects pigs against the E. rhusiopathiae variant and was not related to the emergences of the variant. Abstract Erysipelothrix rhusiopathiae causes swine erysipelas (SE). Sporadic SE outbreaks in Japan are mostly caused by the E. rhusiopathiae serovar 1a variant featured by methionine (M) and isoleucine (I) at amino acid positions 203 and 257 of the surface protective antigen (Spa) A protein (M203/I257 SpaA-type). To determine if current vaccines are effective against infection with this variant in pigs, one representative inactivated vaccine, SER-ME (containing E. rhusiopathiae serovar 2a), was evaluated. All vaccinated pigs survived without any apparent clinical signs after lethal challenge with the Fujisawa reference strain or the variant. This indicates that the SER-ME vaccine effectively protects pigs against the infection of E. rhusiopathiae M203/I257 SpaA-type variant. Current vaccines in Japan, including SER-ME, suggest that outbreaks in Japan are unlikely caused by vaccine failure.