Chicken Mystery

Can anyone help with a solution as to why my chicken, Dotty, has a bright red rumpwith no feathers.  Also she has lost all the feathers on her back, breast and the top of one leg.  The feathers dont seem to want to grow back, there are black stumps but they dont turn into anything.  I have treated her all summer for mites, louse and worms (tho no sign of any) but to no avail. None of my other chickens have these problems.  They are kep in an enclosed pen with plenty of room and given corn and greens to peck at.

I have thought of taking her to the vet but I cant find one who knows anything about chickens.


I am mystified as to what is going on - any clues would be greatly appreciated. 

Hi - thanks for your comments.  I did think about some type of mite or lice and I have been dusting her with various different powders all summer to see if anything would work but still hasnt had any effect.  The red patch gets bigger and smaller but lately seems to be moving up to her tail so something is going on - just cant figure out what!

what about a wound powder followed by gentian violet to hide the red, just in case she is being pecked or doing it herself

I havent noticed the other hens pecking at her - there are only 6 altogether and Dotty is the largest so I dont think she is being intimidated by the others.  I have never seen any of them pecking at her - but good point.

Wound powder and Gentian Violet - I havent heard of them but have looked them up online and both/either could be a good idea - I will get some and try it out.

you should be able to get these items from any horsey shop and they aren't expensive. Good luck