Got ox warbles on a couple of my 3 year old cows. They got hit pretty bad, maybe about 30 - 40 bumps each on their backs and ribcages. Just noticed today. Problem is, I have been using ivermectin pour-on since they were calves. Their last dose was 09/11/09. Any idea why the warbles appeared? What's the best thing to do, let them run their course? A neighbor told me to shoot them up with LA-200. I appreciate any information.