Flea Infestation (Canine)

Canine flea infestation is caused by fleas, which are small, wingless blood-sucking insects. The cat flea is by far the most common flea and is able to live and breed on both dogs and cats. The cat flea also can bite humans and other small pets. The flea life cycle includes egg, larva, pupa and adult. Most elimination strategies are directed toward control of adults, eggs and larvae.

Common names: Fleas, Cat flea, Flea bite allergy, Flea allergy dermatitis.
Scientific name: Ctenocephalides felis (cat flea)

Diagnosis

Signalment
All dogs and cats are susceptible to flea infestation. Almost every dog will become infested with fleas at some time during its life. The adult flea and flea dirt are the two most visible signs of flea infestation. Fleas do not show a preference for a particular dog breed. Dogs between 1 and 3 years old are most commonly affected.

Incidence/prevalence
Flea infestation is one of the most common health problems in dogs. Flea allergic dermatitis is the most common allergy in dogs and is caused by the saliva of flea bites. Adult fleas require a blood meal for survival and reproduction.

Female fleas lay 20 to 25 eggs daily, which fall off the pet into the environment (on floors, sofas, bedding, etc.) The eggs hatch in one to two weeks and larvae emerge, which mature into pupae, which emerge as adult fleas. Ten adult fleas can lay 6,000 eggs monthly, which will then mature and continue the cycle. Under proper conditions, approximately 75 percent humidity and between 70 and 90 degrees Fahrenheit, the lifecycle completes in 30 to 75 days.

Geographic distribution
In temperate climates, problems with fleas are usually restricted to warm-weather months. In hot climates, flea infestations may occur year around.

Clinical signs (primary, most to least frequent, scientific term, synonyms)
Skin irritation and hair loss, predominantly over the lower back, tail and perineum. Presence of fleas and flea dirt. Flea dirt is a term to describe the blood-containing feces excreted by adult fleas. This looks like black specks on the pet and its bedding, itching and agitation—the pet will become very restless and annoyed and will scratch excessively.

Clinical signs (secondary, most to least frequent, scientific term, synonyms)
Anemia, Tapeworms (Dipylidium caninum) - A larval flea consumes the eggs of tapeworms along with flea dirt. A dog licks the flea and swallows it while grooming. The tapeworms attach themselves to the dog's intestine, where it lives out its life. In this way, tapeworms steal important nutrition from the dog. To determine if your dog has a tapeworm, look for debris around the dog's rectal area and in the dog's stool that looks like grains of rice.

Causes (scientific, common term)
Fleas (Ctenocephalides felis).

Organ systems affected (most to least affected)
Skin, Blood, Intestinal tract.

Diagnostic tests
Careful examination of the dog's hair and skin. Some dogs efficiently groom away (consume) fleas, making the isolation of a live flea very difficult. Visualization of tapeworms' segments on the dog's body or in feces, Allergy testing, Skin biopsy, Apply flea-control product and evaluate dog's response, Use of flea comb to capture and confirm flea infestation.

Differential Diagnosis
Skin mites, Skin infection, Allergic dermatitis.

Overview

Canine flea infestation is typically caused by Ctenocephalides felis, the cat flea, which is a small, wingless blood-sucking insect. The cat flea is able to live and breed on both dogs and cats. Fleas undergo a complete metamorphosis including egg, larva, pupa and adult, which under ideal conditions takes 30 to 75 days. Flea development is ideal in warm, humid climates, but development can continue indoors in cool temperatures.

Flea infestation results in disease conditions manifested by hair loss, redness, scabs, and bumps on the lower back, with intense itching as the primary complaint. Flea allergy dermatitis results from an allergic response to flea saliva.

Severe flea infestation can cause anemia, requiring transfusions, especially in very young and old pets. Fleas are a common transmitter of tapeworms (Dipylidium caninum). While grooming, dogs swallow fleas that have ingested tapeworm eggs. The tapeworms begin stealing nutrients from the dog. Dogs between 1 and 3 years old are most commonly affected.

Treatment

Home care
Eradicating all fleas in the home is essential and requires all pets be treated. There are many different products designed to control fleas. Flea products should be used strictly according to label directions. Dog products should never be used on cats, and before products are used on young, old, sick or debilitated pets, a veterinarian should be consulted. In addition, many products are not approved for use on kittens or puppies.

Topical spot-ons, sprays, foams and powders, as well as oral medications, are available. Successful flea eradication requires a comprehensive program designed to kill both adult and developing fleas. Flea-infested areas where pets spend the most time should be treated with products designed for such use. Thorough vacuuming of your home, paying particular attention to areas where your pets sleep and eat, can help decrease infestation. Be sure to throw out the vacuum bag regularly to avoid reinfestation. The yard may also require treatment. Finally, you might consider professional extermination.

Professional Care
Veterinarians diagnose flea infestation by taking a thorough history and doing a physical exam. If no fleas are seen, the veterinarian may do skin-allergy testing or the diagnosis may be based on how your pet responds to treatment.

Once the diagnosis is made, the veterinarian will develop an individual treatment plan. Treatment is tailored to your pet and can include a flea-control medication for your dog and treating the indoor and outdoor environments to kill adult and developing fleas. The veterinarian may also prescribe oral antibiotics, anti-inflammatory drugs and antiparasitic medications. An ongoing preventative regimen is recommended, especially for the allergic pet.

Action
Diagnosis and treatment should be made by a veterinarian. Strict flea eradication is the only effective treatment. Decreased scratching and healthy skin indicates a successful program. Prognosis is good if strict flea control is instituted and maintained.

References/Additional Readings

Muller, GH and Kirk, RW. Flea Allergy Dermatitis. In: Small Animal Dermatology. Philadelphia: W.B. Saunders Company, 1969; 287-289.

Medleau, L and Hnilica, KA.Small Animal Dermatology. Philadelphia:W.B. Saunders Company, 2007; 2nd edition.

Wilkinson, TG. and Harvey, RG.Small Animal Dermatology. Mosby,1994, 2nd edition.

Tilley, LP. and Smith, WF. Flea Bite Hypersensitivity and Flea Control. In: The 5-Minute Veterinary Consult Lippincott Williams and Wilkins, 2004, 3rd edition; 486-487

Author

Geruza Paiva, DVM

Editor

Steven Hansen, DVM, MS, MBA, DABVT, DABT

© 2007. The American Society for the Prevention of Cruelty to Animals (ASPCA)