Fig. 1

Neighbour-joining (NJ) phylogenetic tree calculated from the concatenated housekeeping gene sequences. Tree construction was achieved by the NJ method using the Jukes-Cantor matrix with the complete deletion option. Bootstrap values are shown next to the branches. The scale-bar indicates the number of nucleotide substitutions per site. The final data set contained 2877 positions. Animals infected with only one ST are symbolized by black circles. Those harboring more than one ST over time are represented by green, red, yellow, purple, light blue, pink and dark blue circles. Ambiguous nucleotides in heifers with different ST at the same collection date were resolved before tree construction. Animals infected simultaneously with two different ST are represented by diamonds at the respective time point