My gerbil has become very ill over the last few days. She is lethargic, weak, and has labored breathing (but we know she does not have a respiratory infection) and a ruffled coat. Her hindquarters are soiled as well. We took her to the vet and she was put on the antibiotic Metronidazole for what the vet thinks is a gastrointestinal infection, but she has had 5 doses of the medicine since then, and her condition has only worsened. We have been offering lots of fresh foods to her and her cage is set up in a quiet room, but nothing is helping.
What could possibly be wrong with her?