Oh, for heaven's sake ! Ringworm is no big deal. Almost everyone gets it in their lifetime and it's certainly very common when you have an animal in your home - itchy skin and a rash for 5 - 6 weeks and then, usually, people never get it again. The kitten certainly could have been without symptoms so the SPCA wouldn't know it had it. I've had lots of cats/kittens without the tell-tale patchy, scaly circles and yet I've developed ringworm and shown symptoms first so we then know the cat has it. I just try to keep the cat from mixing with other cats for the course of the active ringworm because it is highly contagious to other cats. Ringworm, like many, many other medical ailments (URI viruses, etc.) can remain in a home on carpets and sofas for years and years but don't really cause any future problems. Bottom line is, if you are having animals in your home, you have to EXPECT all the possibilities that come with them - part and parcel of having a pet.