Cat and dog fleas will infest the animal - generally cats & dogs but they aren't fussy and will take a bite out of anything warm blooded. Your pet's bedding will be infested too.
They'll happily feed away sucking up blood from their host then drop off and lay eggs in your pet's bedding, carpets, bedclothes indeed anywhere your pet has been.
Treatment to remove all fleas normally involves a thorough treatment of pets by the owner followed by spraying the infected areas. If pets have access to the whole property then this is the area needing to be sprayed.
Fish tanks need to be covered along with children's toys however once the spray is dry (usually within about 4 hours but may be longer depending on the weather conditions) it is safe for the occupiers to go home again.
If any areas are missed then re-infestation easily occurs making it hard to get rid of fleas without professional help.
Fleas have the ability to remain dormant for many months if there is nothing to feed on. Within a few hours of the property being re-occupied the dormant fleas emerge to feast on you or your pets.