I have one hen who has a raw red featherless chest and belly with broken feathers. She's acting strangely and has been isolating herself. She's still eating well but is losing weight. I suspect she has some kind of blood sucking lice. I dusted her with pyrethin poultry dust about a month ago and a lot of lice fell off her. I did a follow up dusting a week later and there was no lice this time. I dusted her again this morning and no lice appeared. But something is very wrong and I suspect that it is some type of nocturnal feeder. I just got pour on ivermectin that I was going to de-worm all my chickens with. The other 10 older hens do not seem to be having health problems but I do notice some feather issues around their butts and they all free range so I'm sure they are vulnerable to internal parasites as well. Here are my questions: how do you de-lice a large barn? Do I do a pyrethrum fogger? I have baby chicks and 7 week old chickens as well. I read about the walls and floors but it seems impossible to do the whole barn without using a LOT of poison. Do you think there could be a problem other than parasites? Should I use the ivermectin pour on even though the hen is rather weak and I dusted her this morning? I'm concerned about using too much poison on her. What should I do about the 7 week old chickens? They are not exhibiting any abnormal scratching like they have lice. The baby chicks are in a contained area and do not seem to be involved with lice yet. This will be the second time I dewormed my flock. I dewormed them in the fall according to instructions from threehorses and think it's time to do it again. Thanks for any advice.