Why do cats and dogs have fleas?

Fleas are parasitic creatures and they live by sucking the blood of a host animal. There, are many species of fleas. Its long hind legs help it to jump long distances. It can jump 20 cm into the air and jump forward at least 30 cm. Fleas infest cats, dogs, rabbits, rats, squirrels and tame birds. In the Middle Ages, flea-infested rats spread the plague.