I had a bad outbreak of Pox (wet and dry) here last fall. Before then, I'd never even HEARD of it before!
For the boys, FishZole seemed to do the trick. For some reason, my roos didn't get it as bad as my hens. The entire flock got FishZole water, and while that worked for MOST cases, there were some that needed something a bit more serious.
I had a few hens that had terrible cases of the yellow plaque in their mouths and down their windpipe. One hen seemed to get the infection around her eye, leaving her mouth and throat unaffected.
The first hen to get it was a HUGE learning experience for me. She had the infection in her windpipe, so breathing was a grand struggle for her. I hand fed her for four days - she couldn't eat on her own. I was giving her fish zole in a 4x dose level, but she wasn't improving. It was all she could do to just keep breathing, and that was a strain.
My vet gave me a bottle of Azithromycin Suspension, and told me to give the hen 1/4 of the dropper length once daily. On day 1, I gave two doses, and then continued with once daily. (She weighed 3 pounds.)
After her first night she was noticeably better (not 100%, but better than she has been for days). Her breathing was half as strained, and she had even more of a desire to "wander" on top of the washing machine during feed times. She was still not showing much interest in self-feeding, but it was looking up. She still had good poo's, and that's what I used as a gauge to know that at least I was getting good amounts of food and liquids in her. That was a big concern for me.
She was treated with Azithromycin for 10 days. At the end of her treatment, she was reunited with her flock and is still today alive and WELL! She lays an egg almost daily. She made a remarkable recovery.
I looked online for information regarding Azithromycin and birds, and most of what I've found is that it's being tested for use with exotic birds, and there are writings in vet journals.
Because there seemed to be so many things going on, the vet had me treat the other hens that showed the yellow plaque symptoms with the following:
Azithromycin Suspension: 1/4 dropper daily
Acyclovir Suspension: 1 full dropper daily
Cephalexin Suspension: 1/4 dropper daily
He gave one hen (she was the worst case I had) a leg injection of Baytril while she was at the vet's office.
I ended up having to treat 8 birds in total from my entire flock. When it was possible, I would carefully remove any of the plaque with a round-tip pair of tweezers. It was a very time consuming process, but I believe it helped keep things from building up in the cases that I caught VERY early. The infection certainly made its rounds. When it was all said and done, I lost 1 hen. I consider myself, and my hens, very fortunate.