Although I've never seen a case of ringworm in a ferret, I can't say its not possible, but not that common. There are several types of ringworm and only one of these types (M. canis) fluoresces with a UV light 60% of the time. So there are many cases of ringworm that don't fluoresce (light up) with a UV light. Scaly, dead skin (flakes of skin) can also fluoresce and give a false positive reading. The best way to diagnose ringworm is to pluck a few hairs from the area and place them in a culture which will turn red if its positive (takes about 7-10 days). I caught the tail end of this conversation, but I hope it helps. Dr Weiss 301-299-4142 [log in to unmask] [Posted in FML issue 1117]