SO glad I found this thread, really great info for a novice owner who inherited 5 hens all who seem to have gotten lice after 3 weeks of ownership.
My question is this, however. My birds ALL show classic signs, it started with slowing of egg production, 3, 2 , 1 then none a day, decreased appetite, lots of picking and scratching, and lots of feathers all over my property. These hens have obviously never really been handled, because they are a drag to catch and once you do, it's a real struggle. So tonight, I opened the hen house and had a peek with a flash light while they were roosting. Much easier, but I saw no lice, just a lot of bald spots and what can only be described as a "moth eaten" appearance to the feathers at the vent and under the wings. I saw what looked like could have been egg clusters at the feather base, but the feathers were so messed up, maybe they were just matted? Hard to say.
Having not seen any critters should I just prophylactically dust them? This problem started about 2 weeks ago and I am anxious for them and to solve the problem.