Thanks for the link to the article about Coccidia. It was helpful to read. Luckily Spook doesn't have diarrhea at this point, and we've been watching him closely. He uses his own litter box, so the other cats shouldn't be exposed to it, either. He hasn't found their litter boxes, which are upstairs, because he hasn't ventured upstairs yet. His litter box is in the carrier, and the carrier door is propped open just enough so that he can fit through and get into it, but the other cats are too big. He doesn't act sick or anything. He pesters the bigger cats constantly when he's awake. He plays and plays and plays and plays, and then plays some more! Oh, and did I mention that he PLAYS!