Fig. 2

Phylogenetic tree of equid herpesvirus-1 based on 515 bp fragment from the ORF68 gene. The evolutionary history was inferred by using the Maximum Likelihood method based on the Kimura 2-parameter model [31]. The tree with the highest log likelihood (− 742.11) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches. Initial tree(s) for the heuristic search were obtained automatically by applying Neighbor-Join and BioNJ algorithms to a matrix of pairwise distances estimated using the Maximum Composite Likelihood (MCL) approach, and then selecting the topology with superior log likelihood value. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 41 nucleotide sequences including Polish EHV-1 sequences (n = 13) and international sequences (n = 28) sourced from GenBank (accession numbers included in the figure). All positions containing gaps and missing data were eliminated. There were a total of 495 positions in the final dataset. Evolutionary analyses were conducted in MEGA7 [32]. The clusters were labelled as groups I - VI according to [22]. The sequences obtained in the current study are labelled with red rectangles