Litter Box Cleaning

Question
Our cat is about 3.5 year old domestic shorthair that we've had since he was about 6 weeks old.  He's neutered and still has his claws.

Within the last three or four months, he's become aggressive anytime my wife or myself cleans his litter box.  We've resorted to either shutting him in the bedroom while we do it (and about 10 minutes after) or one person will run interference while the other does the cleaning.  He's always gone after the person doing the cleaning, never the shield.

After a few minutes, he's back to his normal, loving self.  We've not changes his box in anyway.  Same litter, same box, same location...  Any idea why the change in behavior and what we can do to stop it?

Answer
Cory,

I can suggest that if you only have one litter pan you look into purchasing another as the rule of thumb is one litter box per cat plus one. He may feel territorial over his box and therefore feel threatened when anyone else (human or cat) is around it. I would suggest that since this is not a common behavior you have him examined by your vet including blood and urine panels to ensure that no medical issue is missed. I am concerned about the fact that his aggression is directed at people, and if it is purely behavioral you do not want to punish or discipline him around the litter box as he may decide not to use it, so be careful with that in mind. Please let me know if getting another litter box or even two helps, if so you can rest easy knowing that he just felt threatened about the litter and possibly losing his territory. If your house is multi story I would suggest a minimum of one litter box per story. The other thing that I want to caution you about is even though your cat is obviously upset by having his litter cleaned you must do it at least once a day. For the moment until you have a chance to have him examined by your vet I would suggest that you continue with shutting him into another room for the few minutes that it takes to clean his box and as I mentionned before do purchase 1-2 more boxes, you may find that solves your problem...If it doesn't I will talk to my vet and see what she thinks that the cause may be. Please do not hesitate to contact me with further questions or concerns...