A small number of fleas on adult dogs or cats trigger slight damage, unless the host becomes allergic to matters in spittle. The illness that ensues is known as flea allergy dermatitis. Small animals with great swarms can lose sufficient bodily liquid to feeding fleas that could end in desiccation. Cat fleas likewise might be accountable for infection distribution via humans, and have been assumed as distribution proxies of outbreaks.
Cat fleas spread additional vermin and contagions to dogs, cats, and even humans. The most well-known of these are Bartonella, murine typhus, and apedermatitis. The tapeworm Dipylidium caninum can be transferred when an undeveloped flea is ingested by pets or humans. Furthermore, cat fleas have been noticed to transport Borrelia burgdorferi, the etiologic cause of Lyme disease, but their aptitude to spread the illness is undecided.