perhaps giving him a bath to get whatever it is off of him or at least bathe his back end. if he is itchy you can put some hydrocortisone cream on it.
Another option you can use is a 70% isopropyl alcohol and water solution if you have tile or laminate floors heck even crate floors. It cleans, disinfects and dries quickly. I wouldn't recommend it for true hard wood floors as too much can start to remove the finish.