Cat fleas are capable of transmitting plague and murine typhus to humans, though such reports are rare. There are also varied allergic responses to their bites, depending upon the sensitivity of the host. Cat fleas serve as the intermediate host to an intestinal parasite, the dog tapeworm Dipylidium caninum, which is transmitted to the pet when a flea carrying a tapeworm cyst is ingested. Mostly, fleas simply act as a nuisance, since they feed on any warm-blooded animal. A common problem for the host is flea allergy dermatitis (FAD), a costly and uncomfortable ailment for both animals and humans.
In the USA, an estimated $2.8 billion is spent annually on flea-related veterinarian bills. Pet owners spend an estimated $1.6 billion annually for flea treatment through groomers, $4 billion for over the counter treatments, and $348 million professional flea control.