Great article and pictures.
The second part ‘Prevention of external parasites’ is a need to know for everyone with chickens.
I’d prefer prevention over treating and until now I never needed to use Permethrin or any other poison to keep away /destroy lice or mite.
For me its no go to keep songbirds out of the chicken domain so I need to check often, especially in summer.
I do use DE in their sand bath, mixed with sand under the bedding in the nest-boxes, and use it as a paint (with water) to prevent a red mite infestation. The two times I discovered a few lice I could act quickly (cleaning and applying DE afterwards) to get in control again.