Hi Marsi
I did a huge post on what I am now referring to as the Chicken Lice Fiasco - it's called "
Houston - we have a problem". If you scroll back a couple of days you should be able to find it. It outlines the treatment process in detail. At the very least it will give you something to laugh about
If you check around your chicken's vent area and under their wings, a lice infestation will be fairly easy to spot. They are a caramel brown colour and a bit flat looking, and they crawl. They also lay greyish clumps of eggs - Blerghhh! Mites are harder to see as they are fast as lightening, but they tend to be smaller and can be reddish/black in colour. These may also be visible on perches and in nesting boxes. Both mites and lice can cause feather loss.
I used a powder called
Pestene, which I bought from our local Farm Supply store. Hubby and I had to catch each one of our chickens and apply the powder everywhere, paying particular attention to their vent area, under their wings and across their backs. You have to rub it in all over the bird until it looks like it fell in a bucket of talc! The process then gets repeated a week later (to kill off the newly hatched eggs), and then you check another week after that to see if the powder has been successful.
All of the bedding and floor materials will need to be removed and burnt/disposed of. Your perches and nesting boxes have to be thoroughly disinfected too. It really is a pain in the neck! I put extra powder into the nest boxes afterwards so that each time the chickens lay they will get a dusting of powder across their bottoms!
Going forward, preventative measures might include a regular dusting of the birds and their nesting boxes and perches, and access to an outside area so that they can dust-bathe regularly.
I can't guarantee that lice or mites are definitely your problem - it could be any number of things. But these are quite common, and if one chicken has them I dare say they all will to a degree. That's a pleasant thought, isn't it!
Let us know how you go

Krista