My cats were attacked by the evil dermatophyte. My vet prescribed Program both for those who had it and prophylactically for those who didn't. I also discovered a wonder med called Trezaderm. This stuff works gangbusters. It also works for ear mites. Trezaderm has much better tox profile than Conafite. I'm not sure why the meds cost $130. Be careful about some of the ringworm meds; some can be quite toxic. Program has the virtue of being very low toxicity, and the cats like the treat-like pills.

The best bet is to isolate anyone with active ringworm together, vacuum the heck out of anywhere they were in the general population, and watch the general pop. for spots and have the Trezaderm handy. Not everyone will get it. I have three kittens in the same room: two got it and one didn't.

Good luck!