Mites and lice are a problem in every climate. For management I use cedar shavings (if you have enough ventilation the fumes don't bother the birds, if you don't have enough ventilation...fix it!) with about a cup of food grade diatomaceous earth in it (my pens are either 4x8 or 6x8, adjust for size of your pens), since mites love to find cracks in wood to live in I use PVC perches, and as little wood as I can in the coop in general, for clean legged birds I have been known to use sand in their pens for bedding, which seems to help some as well. Usually I just hit the birds with a dose of Eprinex (bonus, gets worms too) and that takes care of it. If they persist I will treat topically with either Diatomaceous Earth or other poultry dust.