Treating and Preventing Fleas on Cats

The ordinary cat flea (Ctenocephalides felis) is the most common parasite on the cat's skin. All cats can be affected except for those living at higher elevations, because fleas do not live above 5,000 feet. Cats living indoors can have fleas year-round.

Fleas survive by jumping onto a host animal, cutting open their skin, and feeding on the blood. In most cases, they cause only a mild itch; but a heavy infestation, especially of kittens or older, ill cats, might cause severe anemia or even the death of the cat. Fleas also are an intermediate host of tapeworm. Some cats experience hypersensitivity to flea saliva. This produces intense itching and a localized or generalized skin reaction.

Flea infestation can be diagnosed by finding fleas on the cat 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.

Look for fleas on your cat's back and around the tail and hindquarters by running a fine-toothed comb through her fur. Fleas are sometimes seen in the groin area, where it is warm and there is less hair. Itching is most pronounced in these areas.

New Methods of Flea Control

New products such as Program, Advantage, and Frontline have practically replaced the use of dips, powders, sprays, and shampoos to treat and prevent fleas. The new products are more effective and safer than the traditional insecticides. They are also easier to administer.

Program (the brand name for lufenuron) was the first and remains one of the most popular agents for controlling fleas on cats. Program is a tablet or liquid given once a month with a meal. There is also an injectable form that is given every six months.

The active ingredient accumulates in the cat's subcutaneous tissue and the flea must bite the cat for Program to work. Program 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 effect 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 cat to die of old age before you notice a reduction in itching and scratching. All pets in the household must be on Program for it to be effective.

Advantage (imidacloprid) is a once-a-month topical liquid that kills fleas by direct contact.

Following application, 98 to 100 percent of adult fleas are killed within 12 hours. Thus, any new fleas that infest the cat 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 cat's system, and therefore is nontoxic. Humans do not absorb the chemical after petting a treated cat. Advantage can be used on kittens 8 weeks and up.

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 cat to be killed. Frontline is a topical liquid that comes in tubes and is applied as described for Advantage.

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. Frontline Plus is labeled for kittens 8 weeks of age and up.

Revolution (selamectin), a heartworm preventive, is a once-a-month topical liquid that is applied to the skin of the cat's neck between the shoulder blades, as described for Advantage. It also controls adult fleas and prevents flea eggs from hatching. Selamectin can also be used to control ear mites, roundworms, and hookworms, as well as some ticks.

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