How Fleas Affect Dogs
Fleas are more than just annoying insects. They are the leading cause of itchiness (pruritis), scratching and skin irritation in companion dogs. Fleas cause some degree of irritation simply by crawling around on a dog’s skin. Inevitably, once they settle on a host, they quickly begin to dine. Fleas survive by biting into their host’s skin and feeding on its blood. Some dogs have fairly mild reactions to flea bites. Others, however – especially young puppies and small-breed dogs – become severely anemic and gravely ill from the blood loss caused by heavy flea infestations.
Symptoms of Flea Infestation
One of the most common problems caused by fleas is a hypersensitivity reaction. In a nutshell, this is a severe allergic reaction to certain substances that are found in flea saliva. Dogs that are hypersensitive to flea saliva can have horrible reactions from only a few flea bites. They become intensely itchy. The most frequently affected areas are the rump, thighs, tail base, belly, flanks and upper arms (especially under the arm pits). Owners of dogs with fleas may notice one or more of the following signs in those or other areas:
- Skin abrasions (sores) - often red, raw, weeping and/or bloody
- Pus oozing out of skin sores (pyoderma) – caused by secondary bacterial infection
- Patchy areas of hair loss (alopecia)
- Tapeworm segments on or around the dog’s anus and in the stool
- Tapeworm larvae on or around the dog’s anus and in the stool (look like rice)
A dog’s self-mutilation in reaction to flea bites sets the stage for potentially devastating secondary bacterial skin infections, which can be fatal. Many dogs that do not have flea allergies still develop severe flea bite dermatitis as a result of the mechanical skin irritation caused by these biting bugs.
In addition to causing skin damage, fleas can carry and transmit a number of potentially serious diseases. Fleas are intermediate hosts for Dipylidium caninum tapeworms. Dogs that ingest adult fleas during their licking and chewing episodes are at high risk for becoming infected with these tapeworms. Children can also develop tapeworm infections if they get fleas into their mouths through any route.
Fleas act as carriers of other infectious microorganisms, including those that cause plague (the bacteria Yersinia pestis), tularemia (the bacteria Francisella tularenis), typhus (Rickettsia bacteria) and myxomatosis (Leporipoxvirus, which causes severe generalized disease in rabbits).
Dogs at Increased Risk
Dogs living in hot, damp climates in close quarters with other dogs are at increased risk for becoming infested with fleas. Fleas thrive in such environments and, because of their remarkable jumping abilities, they frequently leap from one animal to another.