Wow, thos is all good info; particularly since i've been under the assumption (...I know ) that DE will control mites and lice. We clean our henhouse every day,dust the floor and crevices every day and replace clean newspaper also.
We rake our pen and place clean grass hay twice a week. Also dust the whole pen with DE at the same time... I giess my question is: is this adequate husbandry???
Since mites and lice and other parasites can be introduced by wild birds, I suspect (though I may be wrong) that your flock can randomly get them at any time of year depending on what wild birds com to visit.
If by adequate husbandry you are just asking about sanitation, sounds like your flock has a nice clean place to call home!