Garden and poultry dust with Permethrin. They are mites, but that's not to say that there aren't a few lice...because of the feather base.
I have 20 or so birds, so bathing them isn't completely out of the question. I may just bathe them BEFORE they go back into the barn. I am so disgusted. :/
Lice and mites can coexist on chickens and wreack havoc, as I learned this summer when I purchased birds that had an infestation (unbeknown to me and the breeder). The mites were almost microscopic, practically invisible to the eye until they crawled by the hundreds onto the vets hands during close examination to find out what was wrong....and then onto my hands during bathing. I discovered that lice are most easily seen visible around the vent, they like to congregate where the moisture is. Thus, you can sometimes see them around the eyes. Unfortunately, while mites are species specific and only live on chickens...they will definitely bite humans as I discovered. They won't live on your household pets or in your carpet, thank goodness.
A two prong approach is needed to combat these parasites... kill the bugs and then retreat in 7-10 days to kill the bugs that hatch out from the eggs. Once you get everything under control, a regular preventive program may be helpful.
I bought Mycodex from my vet, which is a flea and tick shampoo with pyrethrins and piperonyl. This contains the same ingredients as Rid shampoo for humans. I think Adams Flea and Tick shampoo is a similar product. Adams also has a dip and a spray. I believe that Hawkeye has had very good success with Sevin powder. The vet at Cornell U told me permethrin dust is good, but she did not suggest a particular brand. Note that all these products are very strong and definitely not organic, so wear gloves and even a mask if you are dusting.
I tried using Poultry Protector, which is all natural, and it worked on many of the bugs. But the infestation was really too severe...the bugs were resistant even to subcutaneous ivermectin injections. After this very negative experience in which one bird died, I did quite a bit of research on lice and mites in poultry. Apparently, mites and cocci are considered the top two killers of chickens. Mites seem to be everywhere and pop up in flocks that even have the tightest Biosecurity programs. In regard to toxic overload, in my case...our vet very carefully calculated the treatment dosages based on age and weight of the chickens. I would be very cautious about overloading the birds with a lot of toxic products..
I would like offer to come help you bathe and dust, but we are having a gas shortage due to the hurricane. Gas deliveries are being rerouted to the NYC area and several of our local gas stations are closed. I can send you my cell phone via PM if that helps.
Tina G.