Very sick Leghorn

[henpecked56]

We need some help. I have a three year old hen who began to have a dirty vent. I also noticed she was standing almost upright in order to accomadated her swollen abdomen. At first I thought she was egg-bound but I would've expected her to be dead by now. I looked at her poop and it appeared to be normal... I picked her up and noticed her abdomen was the size of a catalope and her breast bone protruding. She eats and drinks normally but sleeps alot. No nasal discharge or any other obvious symptoms. She's been like this for a month. Having nothing else on hand, I gave her a small amount of injectable Naxcel... I also noticed something very unusual: the feathers where her abdomen rubs close to the ground, appear to have almost a white fungus around the base of the feather.
Any ideas? I can take a photo and send it if you'd like.
Dede Crout