Yes I have noticed the weak get lice or mites when the others don't.This is the hen I've mentioned a few times who I believe has cancer.
A few days ago she staggered out of the coop (the others were already in the coop run) with her face covered in blood.
She was no problem to catch and when I had her on my lap to clean her up and see what the damage was I noticed she had lice, but not mites. You can just see a louse on her lower eyelid in one of the pictures.
While the wound bled a lot and was quite deep it looked like a single hard peck at the base of her comb.
I cleaned her up and disinfected the wound. I didn't have the Permethrin spray with me. The next day I sprayed under her wings and the back of her neck and applied some around her eyes and ears with a cotton bud soaked in the liquid from the spray.
The lice are gone and her comb has healed up.
What I've noticed is that the lice seem to move in when a hen is sick. I don't think it's the lice making them sick, although they are very irritating. I think it's a sign of not being well enough to clean themselves properly.
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