If you have a yard, then the yard can be a source for fleas. Treating the yard without poisoning the cats is a challenge.
Check out the web store Puppy Butts. You can just order on line. They have the stuff you rub on and lufenuron.
It might be worth the expense to pay someone to vacuum everyday. Just to get through this.
GoldenSun/Crossbone Isle diagrams/ 18 teams known https://photobucket.com/u/SwordOfWheat/a/9990a2ee-25f3-4242-ae79-7d2d4b882be4