Molecular Characterization of Lumpy Skin Disease Virus in Bulgaria: Phylogenetic Insights Based on the RPO30 Gene

Capripoxviruses are important viral pathogens of domestic ruminants and include lumpy skin disease virus (LSDV), sheeppox virus (SPPV), and goatpox virus (GTPV). In recent years, the spread of LSDV into Southeastern Europe has renewed interest in its molecular epidemiology, particularly in Balkan countries. This study analyzed partial RPO30 gene sequences obtained from clinical samples collected during the 2016 LSDV outbreak in Bulgaria. Viral DNA was detected by real-time PCR, and RPO30 amplicons obtained by conventional PCR were subjected to Sanger sequencing. The obtained sequences were compared with representative LSDV reference sequences retrieved from GenBank, and phylogenetic relationships were reconstructed using the Maximum Likelihood method. The five Bulgarian sequences included in the final analysis were positioned near Balkan and Neethling-type LSDV reference sequences and showed high sequence similarity within the analyzed partial RPO30 region. Single nucleotide polymorphisms enabled differentiation among the analyzed sequences and revealed limited variation within the Bulgarian sequence set. Haplotype analysis identified 10 haplotypes across the final 30-sequence dataset; however, all haplotype, SNP, distance-based, and phylogenetic results derive from the same partial RPO30 marker and were interpreted accordingly. The data provide additional information on the molecular characteristics of the analyzed Bulgarian LSDV sequences from the 2016 outbreak, while emphasizing the need for higher-resolution genomic approaches for recombinant or vaccine-like strain characterization and fine-scale epidemiological inference.