Controlling and Preventing Fleas in Dogs

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The ordinary cat flea (Ctenocephalides felis)is the leading cause of itching and scratching in dogs and cats. Fleas survive by jumping onto a host animal, cutting open their skin, and feeding on the blood. In many dogs, the bites cause only a mild itch, but a heavy infestation in a puppy or small dog can cause severe anemia and even death.

Some dogs develop a marked hypersensitivity to the saliva of fleas and experience intense itching which results in skin abrasions, hair loss, and secondary pyoderma (see Flea Allergy Dermatitis). Fleas are also an intermediate host for tapeworms.

Flea infestation can be diagnosed by finding fleas on the dog or by seeing black-and-white, salt-and-pepper-like grains in the coat. These particles are flea feces (the “pepper”) and flea eggs (the “salt”). Fecal material is made up of digested blood. When brushed onto a wet paper, it turns a reddish brown.

The adult flea is a small dark brown insect about 2.5 millimeters in size and can be seen with the naked eye. Although fleas have no wings and cannot fly, they do have powerful back legs and can jump great distances. Fleas move through the hair rapidly and are difficult to catch. Run a fine-tooth flea comb through the hair to look for fleas on your dog's back, in the groin, and around the tail and hindquarters. Itching is most pronounced in these areas.

New Methods of Flea Control

• Program (the brand name for lufenuron)works by inhibiting flea eggs from growing and hatching. This leads to a steady drop in the number of new fleas in the environment. Its affect is limited to the hard outer shell of the flea, making it completely harmless to mammals. However, because mature fleas are not affected, it can take 30 to 60 days or longer for the adult fleas on the dog to die of old age before you notice a reduction in itching and scratching.

For more immediate results, and especially if the dog is suffering from flea allergy dermatitis, Program should be combined with a flea shampoo or some other topical insecticide treatment. Advantage or Frontline can be added to Program to kill adult fleas within one to two days. It may be necessary to eliminate fleas on the premises using insecticides.

• Sentinel combines Program with the heartworm preventive Interceptor. This broad-spectrum preventive not only controls fleas, but also protects against heartworms, ascarids, hookworms, and whipworms.
• Advantage (imidacloprid) isa once-a-month liquid preparation that kills fleas by direct contact. Fleas don't have to bite the dog for the preparation to work. Advantage comes in a tube and is applied to the dog's skin between the shoulder blades (you must carefully part the hair to make sure you get the liquid on the skin) and to three or four additional sites along the dog's back for larger dogs. The amount to apply depends on the size of the dog, and will be prescribed by your veterinarian. One application protects a dog for up to 30 days.

Advantage kills fleas on direct contact and may reduce hatching eggs and larvae. Following application, 98 to 100 percent of adult fleas are killed within 12 hours. Thus, any new fleas that infest the dog should be killed before they have a chance to lay eggs. This breaks the flea life cycle and eventually eliminates fleas in the environment. Advantage is not absorbed into the dog's system, and therefore is nontoxic. Humans do not absorb the chemical after petting a treated dog. Advantix is a new formulation that also acts against ticks.

One drawback of Advantage is that it loses some of its effectiveness if the dog's coat becomes thoroughly wet more often than once a week. If this happens, the dog can be retreated as often as once a week.

• Frontline and Frontline Spray contain the active ingredient fipronil,which kills fleas on contact within 24 to 48 hours. The fleas do not need to bite the dog to be killed. Frontline is a liquid that comes in tubes and is applied as described for Advantage. The effectiveness of Frontline is not diminished if the dog's coat becomes wet. The product has a residual effect that lasts up to 90 days in some dogs. Like Advantage, Frontline is not absorbed and thus appears to be nontoxic. One additional benefit is that it also kills ticks for up to 30 days.
• Frontline Plus has (S) methoprene, which is labeled to kill adult fleas, flea eggs, and larvae. It also treats chewing lice and is used as part of a program to control sarcoptic mange.
• The heartworm preventive Revolution (selamectin) is a once-a-month liquid preparation applied to the skin of the dog's neck between the shoulder blades, as described for Advantage. It also controls adult fleas and prevents flea eggs from hatching.

This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.