I hate to tell you guys this but we had these fleas as well. Talked to a vet that specializes in chickens and he told me they would be impossible to get rid of. We sprayed the pens and chickens every 2 weeks for 6 mths. Dusted the pens with DE and sevens dust. Ivermectin the chickens and even bleached all perches, nest boxes and floors. Nothing kills these things. Also found out they can be brought in by coons or other pests. We had a family of coons getting in the pen. We would trap them and because they were in the pen overnight we think the fleas got in our pen.
By accident we figured out how to get rid of them. A few of my hens got out and we couldn't catch them. They were bald headed and you could see the fleas. After a week I noticed the hens that were out (3 of them) the fleas were disappearing and their feathers were coming back. We have 4 acres so we built another pen on the opposite side of the property and put the 3 hens (After some late night catching in the dark) and a couple others in the new pen. Coated the floor with sevens dust. First night we sprayed them with the flea spray and again in 2 weeks. By the end of the month they were flea free and the feathers were coming back. So we built a chicken tractor out of pvc and wire. Moved a dozen chickens at a time and treated with the same spray every 2 weeks and as they were flea free moved them to the new coop. We had over 100 chickens so this took some time but we are now flea free. We woud move the tractor around the property so if any fleas got into the ground their eggs couldn't reinfect the chickens. We have left the old coop empty of chickens for 6 months now. We have alot of chicks hatching now so looking at putting chickens back out in it. We have left the water bowl on a white towel with the heat lap trick and no fleas in the water. We also would get attacked on our legs if we walked into the pen before. They haven't done that the last few weeks. We didn't get a cold winter either so it wasn't the weather that helped get rid of them (central Florida).
So we are going to clean it back up and spray it. Hopefully it will stay flea free.
So in summary (LOL) the only way we were able to get rid of them was to empty the coop and give the fleas nothing to feed on. I think it is they infest the area so you have to empty it to get rid of them. You don't have to empty it for as long as we did but at least a month or more would be best.
