i have two cats in my house. they never go outside. i had fleas in my house in november. bathed, dusted, cleaned,washed everything and think they were gone. now it is august and they are back. where are they coming from? my house is about a 30 year old ranch with no basement. the yard has mature trees and a dry ravine behind it. how can i prevent this from happening again? should i treat outside the house? this has never happened to me previous at other houses/apartments.