I've been having a lot of trouble with one of my Buff Orpington hens. She is 3 years old and free ranges often, and was very healthy up until this point. Nearly a month ago I saw that she was making gasping motions and having trouble breathing. There were no bubbles in the eyes or swelling. She would make little sniffling sounds when she breathed, and that was the only symptom. I figured it may be gapeworm. I researched it and decided to deworm her with fenbendazole, which is supposed to take care of gapeworm. She was still having a little trouble so I had her on the antibiotic Duramycin for about four days. I would have continued a week, but she nose-dived, and she almost died. Her crop stopped, but after many massages it started emptying again a day or two later. After this treatment she was fine. She would run around, peck in the dirt, and act just as a normal chicken should. Then, about a week later, all the symptoms came back I bought the Safeguard (fenbendazole) horse dewormer paste and gave her perhaps six or seven treatments (about an eraser size dot for each treatment) two to three days apart for a while. She never got fully better. I have her on antibiotics now (Duramycin again), and it is now day ten of her treatment. I have not seen much improvement at all. It's as if no matter what I do, whatever this stuff is keeps coming back. Her breathing is worse on cold days, and she's lost weight. Any thoughts on what it could be? Is there anything I've forgotten to do? I'm scared to give her any larger dose of dewormer. I'm perhaps doubling the recommended dosage as it is. Thank you for any ideas!