When one of the three heifers that spent the winter on another farm came home with warts all over her face, we did a computer search and found multiple sites that said 1) that warts are caused by a viral infection (we knew that); 2) that cows often get them, and they are infectious; 3) that after a couple of months the cow develops an immunity and they go away again. In short hand, that means that if you aren’t wanting to sell that cow right away, don’t worry about it. We are now in a position to add our own little bit to the online wisdom, to whit: the warts did not go away in a couple of months, it has been more like six months, but yes, after spreading over much of her face and even onto one shoulder, they are finally receding. No one else showed up with warts, which are supposed to be spread by cows using the same rubbing posts or trees as the affected cow, but in an intensive grazing system paddocks change so often that maybe there’s no opportunity for repeated visits to the same tree.
May this be some help if your cow turns up with facial warts.