Vicious cycle of respiratory illness

[am7039]

Over the course of a year I have been battling respitory illness in my flocks. It started when I purchased 4 chicks from a local hatchery. By day 2 or 3 of having them I noticed respitory issues. I kept them isolated and treated with antibiotics. I lost one and the remainder got better. Although they were completely seperate from my older flock, they all developed symptoms. My guess is even though I went through every precaution not to transfer it, I did. They all fully recovered but about 2 weeks ago one of my older girls developed symptoms again. She was completely separated because she is a surrogate mom to fertile eggs that she hatched. I quickly started her and chicks on antibiotics and she quickly recovered and somehow the chicks never got sick! Fast forward and yesterday one of my older girls was very lethargic. I added electrolytes to her water and now the other two in the flock are showing respiratory symptoms and the girl who was lethargic is in really bad shape. She is laying down and wont move. I feel completely defeated by this illness.

 

[am7039]

I just fear this is going to be a constant back and forth between flocks where I get one better and the next are sick. I have a newer flock that is about 3 weeks old and my anxiety is through the roof that eventually they will also get sick. I do everything I can to prevent the spread including wearing booties over my shoes to prevent cross contamination on my shoes. I thought I was dealing with infectious bronchitis but I'm not sure anymore.