What's Biting You? Or, All About the Flea

Back from vacationing at the beach, Fido and Kitty sniff out familiar haunts around the yard. Meanwhile, their owners plop down on the family room carpet with the month's mail. He scratches an ankle, then the other one, then a leg. She does the same - then looks down and sees why she's scratching: fleas!

During the weeks before vacation, fleas feeding and breeding on the pets deposited unborn offspring all over the homestead. And during the vacation, fleas at various life stages evolved, nourished by dried-blood flea excrement, "flea dirt," in the carpet and elsewhere. The result: A population explosion of fleas ravenous for fresh blood! Let's face it: Left uncontrolled, bloodsucking pests can infest not just your cat or dog, but your entire house - and you!

Common household fleas don't usually transmit diseases to pets and people. The tiny insects are mainly "just a nuisance," says Marcia Larkins, D.V.M., chief of the companion and wildlife drugs branch in the Food and Drug Administration's Center for Veterinary Medicine. "They generally cause a lot of itching and scratching. They may also cause some discomfort due to possible allergic flea bite dermatitis."

Fortunately, a wide array of pest control products for pets are available: foggers, sprays, dips, powders, dusts, collars, oral liquids and tablets, and even a liquid one-spot topical treatment. There are new oral products that interrupt the flea's life cycle, a Lyme disease vaccine for dogs, and a pesticide product that mimics mouse nesting material to reduce ticks outdoors.

The FDA shares regulation of these products with the Environmental Protection Agency and the U.S. Department of Agriculture. If a pest-control product for pets is given by mouth, injected, or absorbed through the skin, FDA regulates it. Otherwise, EPA does. USDA licenses products that treat or prevent animal illness caused by pests. States sometimes add licensing requirements.

American Fleas: Pulex irritans (the human flea), Ctenocephalides felis (the cat flea)

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 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."

The 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.