My cat is 9 yrs old, and over the past year she has started losing hair around her back legs and tail. Initially, I thought it may have been due to fleas, so I got her on a once a month flea tablet that works very well. However, her hair still hasn't been coming back and now she will not use any of the litter boxes. We have not changed the type of litter we use or any of her food, so I am at a loss. We have other cats and dogs and none of them show any signs of illness or behaviors like she has. Any help would be appreciated.
As someone who has similar issues with my own cat, this kind of behavior around the litter box always ends with the same results... my cat has a UTI.
If your cat is acting strange she is trying to tell you something, "Take me to the vet!"
The hairless hindquarters in my experience is usually allergy related, not necessarily like a rash, but an internal allergic reaction that usually requires regular treatment.
But only your vet can tell you for sure.
If you want to try something first before a vet visit, you could try a different brand of litter.
Consider also that missing hair could be the result of licking. Do some careful observing to see if that's happening. This could be helpful information if you do end up taking your cat to the vet for this problem.