I had one girl with quite a few lice eggs near her vent after she was treated and bug free. I found that they didn't wash off easily, but I had used a small scissors and clipped the worst feathers off. To clip around the vent you need to wrap the chicken up so that she can't flap her wings and she will relax. Not particularly love it, but at least not fight. If you have someone to help by holding her while you clip the feathers, that can be eassier. I used the poultry dust and it worked great. Made a "powder puff" out of a panty hose leg (filled it with the dust and tied a knot in the leg and just powdered them thoroughly especially around the vent and under their wings and bellies. I now do that periodically as a preventative.