Phylogeography of samples. (A) Map shows the location of the sampled Michigan bovine herd (star) and the location of milk processing plants where caprine (circles) and bovine (squares) samples were processed. Expanded shapes indicate the locations of the Michigan bovine herd and the six processing plants from which biweekly samples originated and the total number of samples tested. Expanded shapes also include a pie chart indicating detection and MST genotype results (blue = ST20, red = ST8, green = other unknown ST, grey = unable to genotype, white = negative). (B) Phylogenetic tree depicting all known MST genotypes. Colored arrows correspond to STs shown on the map. Tree was drawn according to Hornstra et al.  and rooted according to Pearson et al. .