Fleas are a common proplem in dogs and cats.  Fleas are tiny, wingless insect parasites that can infest many different types of animals, including dogs, cats, birds, squirrels, other wildlife, etc.  Pets can pick up a flea infestation from other dogs and cats, or from the outdoor environment.  Female fleas bite the pet to take a blood meal, which they use for egg production.  Flea eggs fall off pets and hatch in the local environment (eg, bedding or carpet), where they develop into larvae that feed on organic material and flea excrement.  Eventually the larva spins a cocoon (pupa) from which the adult emerges.  Adult fleas immediately seek a lifelong host to continue their cycle of blood feeding and reproduction.  Left untreated, a single pair of fleas can produce a massive infestation in only several weeks time.

Flea bites cause irritation, itching, and often skin infection.  Although fleas prefer to feed on dogs and cats, they will also bite people when present in large numbers in the household environment.  Fleas can also pass on diseases such as tapeworm infection, cat scratch disease, and certain blood parasites, including those that cause feline infectious anemia.  In many cases, dogs and cats will develop flea bite allergy, leading to intense irritation and itching from the bite of even a single flea.

Adult fleas look like small, brownish red sesame seeds.  They hide within the thick hair coat of dogs and cats, making them difficult to find.  Often, the only visible sign of a flea infestation may be your pet's scratching and biting, especially on the rump and around the tail.  You may also notice crusty, reddish brown material within the fur or in your pet's bedding.  This flea "dirt" is actually flea excrement that contains digested blood.

Many topical and oral products are available to kill fleas and prevent their reproduction, and many are effective for a month or longer after a single application.  Your veterinarian can help you choose a product that is safe and effective for your pet.

Written and reviewed by John A. Bukowski, DVM, MPH, PhD and Susan E. Aiello, DVM, ELS