Please read and be aware.

Ive just been reading another forum and someone has posted on there regarding something called the "depluming mite". As I put on this forum I had to have my silkie put to sleep this morning as she developed a limp on friday and got worse. In the end she was unable to stand and the vet mentioned that it may have been neurological. The other thing was (though I didnt take any notice of it ) she had lost the plume of feathers on the top of her head but I didnt worry about it and just put it down to normal feather loss. But the description of the deplumig mite is that"the feathers on the top of the head of certain breeds are lost due to a burrowing mite that destroys the base of the shaft and carries on burrowing and can cause a brain imbalance." Im sure thats what happened to her. You have to treat  the rest of the flock with a spray containing pyrethrum(sp)

Oooo nasty - at least youve found out to treat the rest of your chickens!!

The vet said not. She said its usually in much younger birds.

I've had chickens go down with Mareks disease at two years plus. Its a viral disease that can lie dormant within a chicken without any visible signs or symptoms. The symptoms useually present at times of stress such as the commencement of laying or moulting.
If you can find a vet who knows more than diddly squat about poultry and what ails them, then you are doing very well indeed. The vets who concentrate on poultry are very few and far between.
Depluming mite or feather mite as they are more commonly known, lead to bald chickens and not to them limping and having to have them culled.

very sorry to hear about your loss,

on a positive note, pymethrum (sp.) anti-mite powders are very readily available and cheap, so dosing the rest of the flock to control the mite or as a prevention is very easy. We have some for the canary, who i can asure you is a heck of a lot harder to treat than chooks are! and his peck hurts a hell of a lot more