Dog Fleas, Cat Fleas, Pet Flea Control

While there are more than 200 species of fleas in this country, the main troublemaker for pets is the cat flea. Happy to feed on anyone in the household--cat, dog or human--these wingless insects will most likely choose a pet, whose fur provides warm camouflage for their breeding ground.

The flea life cycle, illustrated in a 794K PDF file, has four stages: eggs, larvae, pupae, and adults. Female fleas lay as many as 50 eggs a day, starting a life cycle that can be completed in as little as three weeks, depending on temperature and humidity. The eggs hatch into larvae, which feed on "flea dirt", excrement of partially digested blood. Larvae grow and molt twice, then spin cocoons, where they grow to pupae and then adults. The adult remains in the cocoon until vibrations indicate a host is nearby. This waiting can extend the life cycle. It also explains why large numbers of fleas often are seen when an empty building is reoccupied. Six-legged adults emerge and attach to a host to feed and breed, beginnning the cycle all over again.

Even when fleas elude detection on a pet, their black poppyseed-like excrement gives them away.

The main problem with fleas--itching--is due not only to their bites, but also to their crawling over the skin.

Other flea bite problems and their symptoms include: anemia in young, older or ill pets--pale gums, weakness, lethargy transmission of tapeworm to pets--irritability, erratic appetite, shaggy coat, mild diarrhea, weight loss, seizures transmission by rodent fleas of plague to cats--fever, swollen lymph nodes, mouth sores, swollen tongue, cough, pneumonia. Also, some pets are extremely allergic to flea bites. In these pets, fleas may cause a rash, inflammation, and hair loss. In response, cats may compulsively overgroom.

Preparations made from antigens extracted from fleas may help, says David Espeseth, D.V.M., deputy director of USDA's Division of Veterinary Biologics. USDA has licensed several.

"If a pet shows a reaction in a skin test," Espeseth says, "that antigen may be effective in treating the animal against that sensitivity. When allergic animals don't react in the skin, this may mean you don't have the right antigen."

FDA has approved new types of prescription flea-control products:

Proban (cythioate), first oral insecticide for dogs--A liquid or tablet, Proban is given once every three days or twice a week. Several weeks' treatment may be needed if fleas reinfest the dog.

Pro-Spot (fenthion), first topically absorbed insecticide for dogs--A liquid, Pro-Spot is applied to one spot between the dog's shoulder blades no more than once every two weeks. Treatment length depends on the rate of flea infestation.

Program (lufenuron), first oral insect growth regulator (IGR) for dogs--A tablet, Program is given once a month with a full meal. The IGR interrupts the flea life cycle: Upon biting the pet, the female flea ingests the IGR, which deposits in her eggs to stop them from developing.

Program (lufenuron suspension), first oral IGR for cats--A liquid, Program is given once a month, mixed with food. Cats must be at least 6 weeks old.

Washing the pet's bedding regularly and vacuuming frequently also helps keep the flea population down. The vacuum bag should be changed after vacuuming and the used one burned, if possible, to prevent it from serving as a flea incubator. Cats who don't go outside have the least risk of getting fleas.


To protect pets from the discomfort and illness caused by fleas and ticks, it's important to rid the pets of the pests. It's also important to treat a pet's environment to prevent or reduce the incidence of reinfestation, says FDA's Larkins.

Products to control these pests are not risk-free, however. (See "Improving Safety.") Approved or registered products must warn users about the risks the product poses and give directions for safest use. Proban's label, for example, warns that the product is not for use in greyhounds, who are sensitive to the insecticide it contains, an organic phosphate. Also, some products should not be used together or when a pet is taking certain medicines.

Larkins advises, "Follow directions for use very carefully, even with over-the-counter products. If you don't understand the directions or have questions, talk to your veterinarian."

EPA product manager Rick Keigwin agrees. As pesticides are intended to kill pests, they generally are inherently toxic, he says. "Some products pose some risks, but they also offer significant benefits. We balance the risks with the benefits."

La Rocca adds that with cats, use only products labeled for cats. "Cats are more sensitive than dogs in general," he says. "It also has to do with their size--just like children are more sensitive than adults--and their grooming habits. Dogs groom, but cats groom more, so they would ingest more of a topical product."

Virtually hundreds of pesticides and repellents are approved or licensed to control fleas and ticks on cats and dogs or in their environment.

To select proper products for your pet's individual needs, talk to your veterinarian, says Larkins. "It's a personal choice between you and your veterinarian about the best product to use and how to treat the animal, as well as the environment."

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