I just brought home a foster puppy who had some very serious injuries and can't walk much. She's also terrified of humans. I was assured she didn't have worms, but I'm paranoid, so gave her deworming medication anyway. Apparently I'm not paranoid enough, because, just going on the claim from the vet that she didn't have worms, I let my cat get close to her (the cat even licked her face several times.) The puppy just pooped for the first time since the dewormer (about 10 hours ago) and it had a nice big worm in the poo! I think it was a roundworm, but the lighting wasn't very good, so not 100% sure. It was definitely a long, fairly thick, spaghetti like pale thing. I've got Drontal and Revolution for cats on hand. The last time I gave it to her was about 2 months ago. If I give it to her now, will it be wasted? Do I need to wait a week or so? Should I give it to her now and then again in a week or two? If it could prevent an infection from taking hold, that would be great, but I don't know if it works like that. (Bad cat mommy admission - I did ask the vet if the cat could be around the puppy and she said yes. And the people in charge of the rescue told me the cat might help the dog settle in since she's terrified of humans. But I still should have been more paranoid and not let them be together at all.) I'm completely grossed out, so any advice would be much appreciated. I've never had a cat with anything other than tapeworm and never had a dog at all, so I'm already completely in new territory just trying to take care of this puppy even w/o worms in the mix!