I think my cat has worms

After I fed my cats this morning, they came back upstairs when they were done eating. My female cat, who is about 8 years old, started meowing and growling. At first I thought one of the other cats was trying to intimidate her or play rough. That wasn't the case and she continued meowing. I could tell she wasn't feeling well. I picked her up and put her in my bedroom away from the other cats, with a fresh bowl of water and a clean litter box.

About 5 minutes later, she went to the litter box. While she was going to the bathroom, she was meowing like she was in pain. I looked at her feces when she was done. It was kind of slippery or mucousy. I then noticed a white thing crawling on the feces, which I assume is a worm. I've never heard or noticed her meowing in pain while relieving herself. I also never noticed worms on her feces before. She does seem to be feeling better since she relieved herself, but of course I don't want her feeling sick everytime she has to go to the bathroom.

I've read that over-the-counter deworming medications aren't very effective and can also do more harm than good. So, I do plan on taking her to the vet today or tomorrow. I researched a bit, to get an average cost of deworming treatment and it was about $60 to $100. Only concern I have is, she is not up to date on her shots. She has been an indoor cat her entire life, along with my other cats. She is healthy, besides this recent problem. Is it really necessary for her to get a bunch of shots? Will the vet require it or can I choose to just follow through with the deworming treatment?

I think the interesting thing is how did an indoor cat get worms?  Since she is 8 it's highly unlikely (in my view) she has had them since being a kitten.  Has she escaped out at all?  Any sign of flease?

Either way, Drontal are highly effective and are safe, and you might be able to get those without seeing a vet.  As to $60 to $100 - that sounds way too much especially at the high end.

I don't think the vet can require shots, but you don't want to be there with a cat spreading respiratory viruses around.

Unfortunately Drontal are pretty large so it can take skill & cunning to get one down a cat - the sort of skill & cunning vet nurses usually have.

I haven't noticed any fleas. Although it is a monthly treatment, I give all of my cats Feline Advantage every 3 months. I've never had problems with fleas or ticks. It's unlikely she's had worms for 8 years... Wouldn't she be very sick by now, if that was the case? I haven't noticed any problems since I've had her, until this morning.

I just went through this with one of mine, I took him to the vet and the vet said that I should treat all my cats with prescription flea treatment and then after a week I went back to get the shot to get rid of the worms. For one cat with the flea treatment(revolution) and shot, it was about 70$.