A) Representative microscopic (10×) IFAT images of sera from the cow which was used to isolate BoHV-4-U. The presence of anti-BoHV-4 antibodies in the first and second sample (6 months following the first) are detectable by green cells when observed with a FITC filter and the negative controls appears brown due to the Evans blue dye. Counterstaining with Evans blue dye observed with a TRITC/filter (red pictures) was used to monitor the integrity of the cell substrate. The merged pictures (FITC/TRITC) allow co-localization of the anti-BoHV-4 antibody staining with the cellular substrate. B) Representative phase contrast microscopic images (10×) of BoHV-4-U cytopathic effect generating plaques. C) Representative phase contrast microscopic images (10×) of BoHV-4-U plaques immuno-peroxidase stained with anti-BoHV-4 antibodies.