Suddenly growling

We have a cat who will be two soon. We got her at an animal rescue place. Apparently, her original owners kept her in their car in which they lived. They put a leash on her and they had been seen holding her by the leash in the air by her neck. At the rescue place, she was wild--racing around the room to the top of the cat tree, file cabinet. There was clearly something playful about it.

A year later, we brought home a younger male cat and she treated him like a mother cat with her young. It was beautiful. As they got older and got to know one another, they began to chase each other and play "leap on each other and fight." She's an affectionate cat, rubbing up against our legs even when she's not hungry and just loving to have her head and ears scratched, of course.

All the sudden, a few weeks ago, she began exhibiting a worrisome behavior. Every other day or so, she suddenly begins growling and, usually, if we get near her, she'll hiss and maybe take a swipe at us. At first, it seemed to be just while looking outside through the glass sliding door. We had to get near to open the door but at the same time we had to watch ourselves. As soon as the door was opened, she'd race out. Her behavior seemed more defensive than aggressive, as in, "don't mess with me or I'll act even more threatening." Any sudden movement from us and she takes a stance like she's ready to strike with her claws or pounce. In fact, she has swiped a bit at us and scratched my wife. Also, it's not just at the door but seems unconnected at times with the door or a desire to get out. When it is a matter of getting out, she'll come in later and be her affectionate self.

My wife is worried that she might have distemper or something.

What do you think?

I'm pretty inexperienced, but this sounds like a case of redirected aggression. This happens when a cat is being stressed by something, if he/she can't get to it or do anything about it they end up taking it out on someone nearby. The most common cause is a strange cat outside causing territorial issues, and if it's happening while she is looking out the window this sounds like it might be the case for you.

Usually for this type of aggression the best thing is to leave the cat alone, and go about your normal routine. Trying to soothe her will not help and she will just end up lashing out at you while she is stressed. You could also try keeping her indoors for a while, and covering up the windows so she is not worried by whatever is happening outside for a while. The best solution is prevention of whatever is worrying her, so you may want to try and find out what is causing her stress and try to find a way to avoid it.

I would also check out the stickies at the top of this forum, there are a few listing forms of cat aggression and possible solutions.

Since her behavior is sudden, I would take her to the vet and get her checked out. Her aggressive behavior may be related to pain/illness. to you and to your kitty that you can get to the bottom of her behavior.