Detection of vaccine-like strains of lumpy skin disease virus in outbreaks in Russia in 2017.

Lumpy skin disease (LSD) has affected many regions of Russia since its first occurrence in 2015. The most devastating year for Russia was 2016, when the virus resurged following a modified stamping-out campaign, causing 313 outbreaks in 16 regions. To avoid unwanted adverse reactions following the use of live attenuated vaccines against LSD virus (LSDV), sheeppox-based vaccines were administered during vaccination campaigns. As a result, LSD was successfully contained in all Russian regions in 2017. In the same year, however, LSD emerged anew in a few regions of the Privolzhsky Federal District of Russia along the northern border of Kazakhstan, which then necessitated vaccinating cattle with a live attenuated LSDV vaccine. Although live attenuated LSDV vaccines are prohibited in Russia, several vaccine-like LSDV strains were identified in the 2017 outbreaks, including commercial farms and backyard animals exhibiting clinical signs consistent with those of field LSDV strains. Sequence alignments of three vaccine-like LSDV strains showed clear similarity to the corresponding RPO30 and GPCR gene sequences of commercial attenuated viruses. How vaccine-like strains spread into Russian cattle remains to be clarified.