The person administering it sits on a little seat above the door of the milk parlor. When the cows are leaving the parlor after their milking, they get sprayed on the back with the dewormer. It leaves a purple streak on their backs.
According to the label, it treats and controls "gastrointestinal roundworms, lungworms, cattle grubs, mites, and four types of lice."
I've not seen one of these creatures - on our farm or anywhere else - ever. Thank goodness.
But just reading that makes my skin crawl. If you see me tomorrow with a purple streak on my back, don't be surprised.