Also Known As: Ctenocephalides canis, Ctenocephalides felis

Transmission or Cause: Fleas are found in the environment. Their survival depends on a warm-blooded mammal for nourishment and they thrive in warm, humid environments. The most common type of flea is the cat flea, although its name is actually a misnomer, as it does not prefer cats and infests dogs just as frequently.

Affected Animals: Fleas can infest dogs and cats of all ages, sexes, and breeds. Animals that spend a lot of time outside are at increased risk of getting fleas.

Overview: Fleas are familiar pests; few pet owners escape the trials of ridding their dog or cat of this common parasite. However, fleas can be eradicated more easily today than ever before. For example, advanced flea control products available through veterinarians require only a single monthly application to the back of the neck or along the spine to achieve reliable flea control on the pet.

A flea is a tiny, laterally flat, wingless insect that subsists on the blood of its host. It has long legs that enable it to jump tremendous distances, such as from one animal to another. A flea's life cycle consists of the adult, egg, three larval stages, and pupa. Currently available flea control products are effective at deterring fleas at one or more of these stages, with the exception of the pupa, which defies current treatments. Although dogs and cats are the preferred hosts for fleas, they can exist on other mammals if necessary.

Clinical Signs: Presence of fleas or flea feces, itching, hair loss, moisture dermatitis or "hot spots", and more severe symptoms can be noted in animals with flea bite allergy. Tapeworm infestations can occur as a result of ingesting fleas.

Symptoms: See clinical signs.

Description: Fleas can be terrible nuisances for animals and humans. They reproduce quickly in warm, humid weather, resulting in large numbers of the parasite appearing within a short period of time. Because fleas take blood as nourishment, they can pose a threat to small, frail animals. Both kittens and puppies can become overwhelmed by a flea infestation and die due to blood loss anemia. Animals with allergies also may develop extremely uncomfortable skin disease from reactions to flea saliva. Normal animals, however, simply will be irritated by their presence. Fleas also can infect animals with tapeworms, an intestinal parasite, if fleas are accidentally swallowed.

The first step in flea control is recognizing the problem. Animals should be checked frequently for fleas by being brushed while standing over a white sheet; the flea feces, small, black flecks of digested blood, will fall off easily, indicating the presence of fleas. A flea comb with very fine teeth also is helpful to remove flea debris and may remove some adult fleas, if enough are present.

Most fleas congregate over the rump and tail area of the pet. If evidence of fleas is noted, the animal should also be checked for tapeworm segments, which appear as cream colored, rice-like segments stuck in the fur around the anus or in the feces.

Diagnosis: Diagnosis is based on the presence of fleas, flea feces, itching, and hair loss.

Prognosis: With a proper flea control plan and dedicated treatment, fleas usually can be kept under control. Flea control is a more difficult endeavor in year-round warm climates.

Treatment: Getting rid of fleas involves treating all animals, and eradicating their presence from both the indoor and outdoor environments. Navigating through the myriad of flea control products available today can be extremely confusing; in addition, some products are toxic to particular species. A veterinarian can recommend several different products and can help design a complete treatment program. The house and outdoor environment either can be treated by the owner or by a professional exterminator, and environmental products which contain both an insecticide (permethrin, pyrethrin) to kill adult fleas and an insect growth regulator (nylar, methoprene) to prevent development of eggs/pupae should be used.

All flea control products work at one or more stages of the flea's life cycle. Attacking the fleas at different stages will result in faster eradication. The only stage that is resistant to treatment products is the pupa stage. The pupa is wrapped in a cocoon that renders it virtually indestructible. Eventually, though fleas at this stage will be eradicated when they emerge as an adult flea.

Fleas can hide in many places indoors, so piles of old newspapers and magazines should be disposed, and non-carpeted surfaces and crevices should be mopped and disinfected. Vacuum cleaner bags should be changed and discarded after each use, since the eggs can survive within the bag and be deposited back into the carpet when the vacuum cleaner is used next.

Prevention: Most flea collars are not particularly effective in the fight against fleas. Some special collars that control flea eggs, however, can be more helpful. The best eradication is achieved with advanced topical products that require a single monthly application at the back of the neck or along the spine; these products currently are available only through veterinarians.