My rats have reoccurring URIs, and I feel really bad. My vet says it's because I've been using aspen in their digging box and have wooden toys. I feel really bad about it. She said that all wood shavings were bad, not just cedar and pine, but she really didn't know what aspen was at first. They keep on getting these URIs, so I'm thinking - maybe it's mycoplasmosis? She said it's concerning because they've been in several times and seem to be reinfecting themselves somehow. This would make so much sense to me if it was mycoplasmosis, but the vet has never said that's what this is. I have a course of baytril for them, but I almost feel like they need to be on it for the long haul. They're about six months old now.