First time cat owner, HELP :( Cat acting different... worms, diet???

[bingsoo]

Hi, so I've had my first cat for 7 months and just got another kitten a week ago. Since a couple days ago though my cat has been acting strange. He usually eats dry food but I wanted to start feeding him more wet food but after he ate the wet food he threw up. After that, he's been throwing up after every meal so I had him fast for a day. The following day, I gave him less than half the amount of dry food he normally eats which he ate without throwing up. However, today he seems to not have an appetite again and will not eat and he seems a bit more lethargic than usual. Not sure if that's just me being paranoid but I feel like he's been napping/loafing more than usual but every now and then he seems normal in terms of energy level.
Another theory why I think he may be like this is because of the new kitten. She was an outdoors kitten so she was infested with fleas when we got her so we think she may have parasites and gave it to my older cat. I also never got my older cat dewormed because I didn't know that kittens usually have worms so do you think it could be due to not getting him dewormed? Also, the kitten been having yellow-ish diarrhea but I'm not sure if that's because of possible worms or because we changed her diet. The previous owner said she was eating dry food but we switched her to wet food and since then she's been having the runs. We mixed dry food in her diet and then switched to only dry but she's still been having diarrhea. She's acting normal though other than that.

Any advice or suggestions on this would be greatly appreciated. Thank you!

 

[Furballsmom]

Hi! Welcome!

I would suggest contacting a vet, even if just through email with all the information above and see what they suggest.

Also these two articles may be of help to you

How To Introduce A Kitten To An Older Cat

First-time Cat Owner’s Guide

 

[Mamanyt1953]

I agree with Furball's mom. Contact your vet, tell them exactly what is going on, and let them advise you. The new kitten, having been outdoors, almost certainly has worms, and possibly other parasites/infections, and may have passed them to your cat. Your vet will give you the best advice possible.

I'd also like to know how long it took you to switch from dry to wet with both the cat and the kitten. You may have simply rushed things a bit, which will cause tummy upsets, some of them pretty severe with some cats.

 

[Hannah518]

Definitely a vet check up. I just got a new kitty from the shelter and she’s quarantined from my other cat right now because of introduction purposes and she had tapeworms, and possibly herpes or ringworm we are waiting for tests for. Sometimes fecal tests don’t test positive for worms unless you see them. Her first test was negative that was soft with blood. Next day I saw worms. After the first deworming it took several days for it to go back to normal but pumpkin helped.