Flea Biology and Consequences

PetSmart - PetSmart
April 24, 2009

The most common flea to infest dogs is Ctenocephalides felis, the cat flea.

The flea life cycle begins with the adult female flea living on the dog's skin. She bites the dog, taking a blood meal. She then lays her eggs, and these eggs drop off the dog into the environment. Eggs hatch in 1 to 10 days (depending on environmental conditions) into free-living larvae. These larvae feed on organic debris in the environment, carpeted areas of a house provide the ideal micro-climate for the larvae to thrive.

After one to two weeks, the larvae spin a cocoon and enter the pupal stage of development. The pupal stage may persist for several months, depending primarily upon temperature and humidity. Under most circumstances, adult fleas emerge from the pupae after about 5 to 10 days. They immediately begin searching for an acceptable host, and the life cycle repeats. The entire life cycle usually takes 3-4 weeks to complete. The key thing to remember is that the adult fleas on the animal represent less than 5% of the total flea load in any given environment. Egg and larval stages represent about 80%, and pupae make up about 15%.

Flea infestations result in a myriad of health problems for dogs. Some dogs have an immunological reaction to the bite of the flea, resulting in flea allergy dermatitis (FAD). FAD is characterized by intense itching, erythema (redness) of the skin, alopecia (hair loss), and secondary pyoderma (bacterial infection of the skin). These lesions, especially the hair loss, are most pronounced over the back and hindquarters of the dog. Dogs with FAD can suffer from severe dermatitis with only a mild flea infestation.

Fleas also can carry larval stages of the tapeworm Dipylidium caninum. Dogs can then become infected with tapeworms by inadvertently ingesting the affected fleas while chewing at their skin. In the western half of the United States, fleas transmit the bacterium that causes bubonic plague! In young or debilitated animals, a heavy flea infestation can result in enough blood loss to make the animal anemic, possibly to the point of requiring a blood transfusion!

Flea infestations occur throughout the United States, but areas of high elevation and/or low humidity have lower numbers of fleas. As with many other dog health problems, it is easier to prevent fleas from affecting our pets than to treat a pre-existing infestation.

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