My two cats are strictly indoor cats. What's the recommendation for flea treatment? I don't have any windows open downstairs but my storm doors have pull down windows on top. The opening on top has screens. I do feed strays/ferals outside. My cats sit in the windows upstairs. I do know that fleas jump and I'm concerned about the downstairs screens on the doors and fleas coming in. I didn't worry last year because I wasn't feeding strays and there were no other cats around. I don't want to use chemicals on them if its not really necessary. Or should I treat them as a precaution? Any recommendations as to what flea treatment?