Cats can pick up fleas from environments where other flea-infested animals have been. This could be your home, backyard or other outside areas. It is rare for adult fleas to jump directly from one animal to another. The flea life cycle consists of four stages; eggs, larvae, pupae, and adults. Of these, only the adults live on your cat, with the rest found in the environment where your cat lives and sleeps. One female flea can lay up to 50 eggs per day.
These fall off into the environment to develop into larvae, then pupae and finally emerge as new adult fleas 3 weeks to 12 months later, depending upon temperature and humidity. It is these newly emerged adult fleas that may re-infest your cat. These environmental stages actually account for 95% of the problem – the adult fleas you may see on your cat are only the tip of the iceberg.