Yesterday, one of our roos was walking like he was in pain -- very delicately putting his feet down, resting between steps, etc. I picked him up to take a look and found that the feathers around his vent were thickly caked with mite eggs. His skin was raw, red and bleeding and there were mites crawling all over him. We dusted him and gave him a dose of eprinex topically between his shoulders. This morning he was completely mite free. We checked each and every one of our 75 chickens, and every single one of our roosters had the infestation, while the hens did not (some hens had a few mites, but no eggs). We dusted the roosters and gave every single chicken a dose of eprinex. Any ideas why all of our roosters would have a horrendous mite infestation while none of the hens do?