his picture just 'spoke' to me - I instantly connected with him and knew that I would not forgive myself if I did not help the little guy.
Congratulations and thank you for helping the kitten.That was very kind of you.
Last night, I dewormed him, bathed him with a special flea shampoo and when he was dry, treated him with Frontline Combo solution for fleas.
Oops. Frontline should not be used within a week of a bath. Frontline distributes through the animal's skin layer by attaching to the skin oils - the same skin oils that you removed when you bathed him. So the Frontline you applied right after the bath had no way of distributing through the skin layer, making it effectively useless. The flea bath apparently removed the visible fleas, but it would be a good idea to buy a flea comb and comb him daily until it's safe to administer another dose of Frontline.
I have two cats of my own - a 4 year old and a 7 month old. Now the question is: how long do I have keep the stray isolated until I can be sure that the fleas won't jump onto my two cats?
How long do you expect to be fostering this kitten? If it's only going to be for a few days, there's no need to incorporate him into your household of other cats. As far as fleas are concerned, if the kitten still has fleas, the fleas can and will leave your bathroom on their own and get into the rest of your apartment with your other cats. It won't require the kitten getting out of the bathroom.
I got the pet-safe spray for treating the apartment in general, though I'm not sure how often that should be done.
All flea sprays are not created equal. Some work and some don't. Make sure you buy only flea control products recommended by your vet and use them according to label instructions, including removing the animals from the premises for as long or longer than recommended.
Also, if they begin communicating, will that mean that I need to deworm my two kitties as well, just in case they have ingested some larvae eggs?
If the stray was dewormed with a vet-approved dewormer, and you remember to give the follow-up dewormer as prescribed by your vet, your other cats should be at no risk of contracting the types of parasites killed by the dewormer. There are, however, protozoal parasites like giardia and coccidia that are not killed by normal dewormers and that may not show up in a fecal exam. If the stray has these types of protozoa, it is possible for them to be transmitted to your other cats by sharing litterboxes.