Your kitten will need their rear end checked daily to make sure they don't have any poop stuck to their fur. Persians are extremely fluffy. What I do is keep their fur trimmed short around their rear and sometimes down the back of their legs. This can be done with scissors or electric clippers. Take care not to cut your baby's skin! When their rear end, or feet, get dirty, simply wash that area with warm (not hot) water and Dawn or baby wash. Kittens will also occasionally (accidentally) step in his poop while in the litter box, so check the bottom of feet as well as the rear while he's young. This issue will improve with age. While kittens are growing up it is your job as Mom or Dad to keep them clean.