I'm treating a captive bred (produced her myself in 2001) for an infection related to the parasite giardia right now. Apparently this parasite overwhelmed her and caused irritation of the digestive track to the point that I noticed a visible infection in the vent area. Her vent scale didn't sit flat, I could see dark inflamed tissue under it, she left ooze trails on the cage floor, and crawled around with her tail in the air all the time (not just when defecating). I'm not sure where she got the parasite from as the only other snake she has been with was her captive bred father for a breeding attempt last winter. My suspicion is that it may have come from feeder mice (she went back from rats to mice about 6 months ago).
With the vet visit, the fecal exam to diagnose the parasite, the antibiotics, and the flagyl to treat the parasite it cost me about $90 however I already had a feeding syringe to administer the meds and I think it cost about another $20.
She is responding well and her symptoms are already gone in less than two weeks so hopefully she will be back to eating again soon.