Dog: Fleas

General information

Other common/scientific names: Ctenocephalides felis, Ctenocephalides canis

Ectoparasites are parasites that live on the exterior or surface of an animal. The common canine ectoparasites include fleas, ticks, lice and mites. They can transmit various diseases and cause hypersensitivity and skin disorders in animals. Some ectoparasites (mites and lice) spend their entire life on the dog while other ectoparasites (fleas and ticks) spend part of their life cycle in the environment. Fleas, ticks and mites are not species specific, meaning they can infest animals of different species.


The dog flea is Ctenocephalides canis. However, the cat flea, Ctenocephalides felis, is the common flea found on the dogs in North America. The cat flea can also transmit disease and serve as a host for Dipylidium caninum or the tapeworm. The flea is a wingless ectoparasite with a flattened, brown body and long, specially developed, back legs. These legs allow a flea to jump (up to 200 times its own body length) between hosts. An adult flea is approximately 1/8 inch long.

Fleas have four life stages: egg, larva, pupa and adult. All stages can be found off the dog and on surfaces such as carpet, bedding or grass, although the adult flea spends most of its time on the dog. The adult flea requires a host for a blood meal. While on the host, female fleas can lay up to 50 eggs per day. These eggs will then fall off the dog and hatch into larvae within a few days. The larvae develop in the environment where they prefer warm, moist, dark places. Within 7 to 10 days, the flea larvae will develop into pupae which develop into adults within 1 to 2 weeks.

The pupa stage is the resilient stage of the flea and if the conditions are not optimum, pupae have the ability to remain dormant for up to a year. Warm temperatures, including body heat or activities such as walking or vacuuming will stimulate the pupae to emerge from their cocoons and develop into adult fleas. Because of this, a house or room which has been uninhabited can become infested with adult fleas in just hours.

None of the life stages can survive freezing temperatures, which is why flea populations and infestation problems decline in winter after the first frost. However, adult fleas can survive the winter in northern temperatures by living on hosts including wild or domestic mammals. Likewise, eggs can survive cold temperatures in the nests of wildlife. Dogs housed indoors enable fleas to breed and survive the colder months. Also, areas of the United States which are hot and humid and areas which have milder winters will have flea populations year-round.

Abb. GG1YBHCO: Photograph of a flea.


Dogs acquire fleas by contact with other dogs, animals or humans which have fleas.

Abb. GSRASJLI: Flea bites in a human.

Cardinal symptom

  • Itching
  • Flea Dirt


While the clinical signs of flea infestation include itching and flea dirt, not all dogs with fleas will scratch. Flea dirt is actually flea excrement or fecal matter. Flea dirt appears as small, black specks similar to sprinkled pepper and is most commonly found at the base of the tail but can be found anywhere on the dog’s body. Some dogs develop flea allergy dermatitis which is a hypersensitivity reaction to the flea’s saliva when the flea bites the dog. These dogs suffer from intense itching, hair loss and red, scabby skin.

Very young puppies and small elderly dogs can develop life-threatening anemia from blood loss due to fleas feeding on blood. These dogs will show signs of weakness, lethargy and pale gums.


Diagnosis of fleas is made by finding live fleas on the dog. This is best accomplished by combing the dog with a flea comb or fine tooth comb to trap the flea. Because some pets are effective at licking and grooming, it may be difficult to find live fleas on your dog. Flea infestation can also be diagnosed by finding flea dirt on the dog. Suspected flea dirt can be combed onto a white piece of paper and the paper moistened with water. Because flea dirt is composed of dried blood, the flea dirt will turn the paper a reddish brown color.

Abb. GG1YHDMD: Flea Comb.
With a fine tooth comb, fleas can be trapped and identified.


Treatment of flea infestation must involve the dog and the dog’s environment. The most common cause of flea treatment failure is failure to treat the environment. There are many different flea control products and medications. To obtain the best and safest results, consult your veterinarian before using any flea products.

Treatment of flea infestation on the dog

The oral and topical (spot-on) antiparasitic products are most commonly used to treat and prevent flea infestations. In cases of severe flea infestation, a quick, short acting oral antiparasitic is used to kill the adult fleas in addition to a longer acting, monthly product. Some of these products also kill the other stages of the flea’s life cycle. These products should be purchased from a veterinarian. Many of these products cannot be used in puppies under 7 weeks of age. In these cases, a flea spray or powder can be used.

Indoor Control

Floors, carpets and furniture should be vacuumed daily if an indoor dog has fleas. Vacuuming will remove adults, eggs, larvae and pupae. Both dog and human bedding should be washed in hot, soapy water. Insecticide sprays and bombs may need to be used for effective control. Insecticides which kill all stages of the life cycle are most effective. In cases where the flea infestation is severe or cannot be controlled, a professional exterminator may be necessary.

Outdoor Control

In severe cases of flea infestation, treatment of the dog’s outdoor environment with insecticides may be necessary.


Prevention of fleas in the form of monthly oral or topical (spot-on) antiparasitics is recommended. These monthly medications can be a combination of medications used to prevent tick, flea, mite, heartworm and endoparasite infections.


When applying the topical, spot-on medications, be sure to part the hair and apply the medication directly to the skin. Do not bath or allow your dog to swim for 2 days after application. The product may need to be re-applied more often than every 30 days. Vacuum bags should be removed and disposed after each use.


All animals living in a household must be treated for flea control to be effective!

Update version: 4/24/2014, © Copyright by
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The information offered by enpevet Ltd. is intended solely for information purposes and and does under no circumstances replace a personal consultation, examination or diagnosis through a veterinarian. Thus, the information serves as an addition to the dialogue between pet owner and veterinarian, but can never replace the visit to the veterinarian. enpevet® would like to ask all users, whose animals have health concerns, to see a veterinarian as required. If you have any questions regarding the health of your animal, we recommend that you turn to your trusted veterinarian , instead of starting, changing or breaking off treatments on your own. The content of enpevet® cannot and should not be used for making your own diagnoses or for the selection and application of treatment methods.