The Importance of Fighting Fleas

They're more than just a nuisance - they transmit disease and can be hard to eradicate.

Awitty pet store owner once used the following sign to sell puppies: Buy one dog, get one flea. Unfortunately for cat owners, not only do fleas rarely travel alone, but neither do they limit themselves to our canine friends. It has been estimated that Americans spend approximately $1 billion every year in the attempt to eradicate fleas from both our homes and our pets. There are hundreds, if not thousands, of products to choose from when battling these jumping, biting monsters; however, in order to eliminate them, the fleas lifecycle must first be understood.

Fighting Fleas

Bev Caldwell


Although there are many species of fleas, Ctenocephalides felis felis (a.k.a. the cat flea) is by far the most common in the United States, infesting cats, dogs and humans as well as other mammals and birds. They thrive in warm, moist climates and feed on their hosts blood. A flea bite can be differentiated from a spider bite by determining how many puncture marks there are in the center of the bite; a flea bite will have a single puncture, while a spider or ant bite will have two punctures. William H. Miller, Jr., VMD, a professor of dermatology at Cornell Universitys College of Veterinary Medicine and medical director of the Companion Animal Hospital within the Cornell University Hospital for Animals, explains that the fleas saliva is the cause of flea allergy dermatitis (FAD). “Flea saliva is a complicated substance with over a dozen components that can be either irritating or allergenic,” says Dr. Miller, who is board-certified by the American College of Veterinary Dermatology. “This is why fleas can so quickly become more than a nuisance.

In addition to bringing inevitable discomfort to their hosts, fleas can also spread any number of diseases. As Dr. Miller explains, “Fleas can transmit the dog tapeworm and various bloodborne infectious agents – it depends on the type of flea and the agent around. The worst example is bubonic plague, which is transmitted by the rat flea.”

The Stages of the Flea’s Lifecycle

There are four stages in the fleas lifecycle: egg, larva, pupa and adult. According to Dr. Miller, a newly emerged adult flea can survive from approximately 12 days to over 100 days, depending on the availability of a food source. An adult female can lay up to 50 eggs per day, or 500 to 600 in her lifetime. The eggs are white and roundish and do not stick to their host; they often fall off the host animal into the soil, carpet or bedding. Dwight Bowman, MS, PhD, a professor of parasitology in the Department of Microbiology and Immunology at Cornell, explains that the time it takes for eggs to hatch varies depending on the temperature: “The time for hatching increases from a day and a half to six days as temperatures decrease from 32C to 13C; a temperature of 3C for one day kills 65 percent of the eggs, and longer times at that temperature will kill all eggs.”

The larvae are one-quarter inch long and semi-transparent white, with small hairs along their bodies that permit them to move around and eat. They feed on the feces of adult fleas (which are composed mostly of dried blood) and any other organic debris that may be found in the soil, carpet or bedding. The larval stage usually lasts from five to 18 days; the larva then spins a silken cocoon and pupates. “The pupal stage can be as short as ten days, but the pre-emerged adults might remain in the cocoons for up to six months,” says Dr. Bowman. “This pupal window may cause problems in control measures and has to be understood by pet owners.” Heat and pressure – both of which are signs that a host may be nearby – can cause emergence.

The most important thing to remember when preparing to battle fleas is that the typical flea population is composed of 50 percent eggs, 35 percent larvae, 10 percent pupae and five percent adults. Obviously, a single treatment designed only to kill adult fleas “once and for all” will not eliminate the flea problem completely; the eggs will soon hatch, the larvae will pupate, the adults will emerge from the cocoons, and you will still be scratching.

According to Dr. Bowman, “We have found that the best means of control (besides turning off the heat for a week in the middle of a New York winter) is integrated pest management using the pet as the source of the medication. Topical, oral or injectable applications to the pet of adulticides or products with activity

Fighting Fleas

Bev Caldwell


against developing stages have brought the problem well under control with year-round use. Only massive infestations will require the administration of products to the environment.” It is important to note that, when using any over-the-counter flea-control products, you should read the entire label and carefully follow the directions; many products contain ingredients with the potential to be harmful if used improperly.

Effective Flea-Control Methods

Excellent flea-control products are now available from your veterinarian – spot treatments, oral tablets and injectables.

Spot treatments are generally applied to a small area of the skin behind the head or neck. Dr. Miller describes how they work: “Spot treatments work either by spreading over the cats entire skin surface or by being absorbed through the skin at the point of application, circulating through the blood, and being transported back to the skin over the whole body by the blood and through sebaceous gland secretions. Some products (e.g. Advantage Multi) use both mechanisms. Those products that envelop the skin can be absorbed into the sebaceous glands with subsequent replenishment of the surface insecticide when the sebaceous glands secrete.”

Advantage, Frontline, Revolution, Promeris and Vectra 3-D are some of the spot treatments available from your veterinarian.

There are other spot treatments available over the counter, but Susan Farmer, DVM, owner of the Bath Veterinary Hospital in Bath, New York, cautions against their use. “Over-the-counter spot-on flea-control medications are made with pyrethrins [which are derived from the chrysanthemum plant and are less expensive to produce]. Pyrethrin toxicity is a known entity; however, some fleas seem to have grown resistant to pyrethins.”

Oral tablets include Program, Sentinel and Comfortis, which are designed to be administered on a monthly basis, and Capstar, which is given more frequently and in conjunction with an insect growth regulator. Program is also available as an injectable treatment, but only for cats. All of these treatments contain repellents, insecticides and/or insect growth regulators, etc. and effectively interrupt the fleas life cycle. Your veterinarian can help determine which product(s) will best suit your pet and situation.

By being both knowledgeable and persistent, pet owners can significantly reduce and possibly even eliminate the annoyance and harm caused by fleas. At the very least, your cat will be a much happier companion!