Coaching pet owners through unrelenting flea infestations

Joan Capuzzi, VMD

Vetted, Vetted May 2020, Volume 115, Issue 5

Fleas have a supersonic life cycle and fireball breeding power, but many veterinary clients don’t grasp the behemoth problems these arthropodal dynamos can create. That’s where you come in.

We all know the story: A dog walks into a bar—ahem—your veterinary practice, and says, “I’m itchy.” You see patchy hair loss and excoriated skin and know that the possibilities are endless. But one rake with a flea comb yields an immediate diagnosis and the news is delivered.

This initial flea diagnosis is where you, super-vet, must sound the alarm. What I tell owners is that in the event of a nuclear war the only survivors will be horseshoe crabs, cockroaches and, you guessed it, fleas! I’m joking, of course, but I want my clients to take the problem seriously because if they don’t act quickly, aggressively and with painstaking rigor, they will be combatting these hardy invaders for a long time. But sometimes clients just don’t get the message the first time around.

Give them the facts

Fast forward many months, and the owner is back in your office because the fleas won’t go away, or the owner “got rid of them and now they are back.” Get real with your client by reviewing with them these facts:

  • The adult fleas you see on your cat or dog—Ctenocephalides felis—likely number fewer than 20,1-3 but these buggers are just the tip of the iceberg.
  • Each female flea lays 10 to 50 eggs a day,4,5 with a lifetime total of up to several thousand. Fleas reproduce following a blood meal, with a new generation of fleas emerging every few weeks.
  • The length of flea life stages varies depending on environmental conditions: eggs (3-21 days), larvae (1-2 weeks), pupae (1-3 weeks to one year) and adults (2-7 months).4,5
  • Your pet’s fleas never really went away. The “new” infestation is likely another generation of the original batch, still thriving because the life cycle was never broken.
  • You cannot break the flea life cycle without chemicals. Natural remedies (e.g. garlic, coconut oil, borax) won’t put a stop to it.
  • With rare exception, if one pet in the household has fleas, every pet has fleas. Surprised because your other pet(s) are not manifesting flea allergy dermatitis and/or pruritus? Don’t be! Flea infestations in some pets are clinically silent.
  • If your pet has fleas, your home and likely your yard are also infested.
  • Leaving an infested environment, like a vacation home, does not necessarily make the fleas die. Adult fleas can live for a few months without a food source, and pupae can survive for up to a year in a barren house; adults are triggered to emerge by vibrations, carbon dioxide and warmth.

Recommend a holistic approach

After reviewing the principles that lay the groundwork for persistent flea infestations, I ask how the initial infestation was managed. Then, together, the client and I identify the smoking guns. The most common oversights are (1) failure treat all pets in the household at the same time for an adequate duration and (2) failure to treat every part of the environment at the same time as every pet is treated.

Treating the pet

I tell owners, “Let’s turn your pet into a walking exterminator.” By treating the animal immediately with an adulticide, the fleas currently on the pet and those that jump on when the pet goes home will die quickly, before they have a chance to lay eggs. I get an adulticide such as nitenpyram on board before the pet leaves my office, thereby killing any fleas that might leap onto the fur from the cat carrier or the car during the ride home, and bringing the pet immediate relief.

I advise the owner to bathe the pet well, manually removing adult fleas in the process. They can then begin, or resume, using an oral or spot-on insect growth regulator such as lufenuron, methoprene or pyriproxyfen. These must be given monthly—according to the product instructions—in order to dismantle the flea life cycle successfully. At a minimum, they should be continued for at least two months after the last flea is seen, and then ongoing depending on individual risk factors.

Treating the environment

The entire home must be treated, right down to the cracks between the floorboards, where flea eggs can drop and safely mature:

  • Mop floors, then rinse the infected mop immediately under running water so all fleas, larvae and/or eggs are washed down the drain.
  • Flea eggs, which are dry and fall from the pet’s coat, can sink deeply into carpet. So vacuum all carpets immediately and repeatedly. Put used vacuum bags into sealed bags, and dispose of them in an outdoor trashcan. Then wipe down the bottom of the vacuum cleaner and, for bagless machines, the canister itself with a cloth dampened with water or (even better) an insecticide solution.
  • Fabric can harbor any of the four flea life stages, particularly pupae, which cling well to fibers. Launder in hot water or dry clean all removable fabric in the home, from pet bedding to human bedding to furniture upholstery to curtains.
  • Treat hidden spots where fleas can multiply with abandon, such as corners and crevices, beneath furniture, and inside garages and sheds.
  • Treat your yard, particularly near the entrances to the home.
  • Vacuum/clean and treat all vehicles and transport devices (i.e. cat carrier) the pet has come in contact with, as fleas in these areas can re-infect treated pets.

Chemical treatment of the home and yard, I tell owners, is sometimes best left to professionals. For a stubborn flea problem, dial an exterminator. Owners wishing to do it DIY-style can use pyrethroid foggers and sprays in home and outdoor areas.

Is it safe to come out yet?

I explain to owners that if all goes according to plan, it will take a couple months to completely eradicate the flea infestation. More commonly, these diehards wax and wane over six to 12 months as adults die and eggs hatch. When my clients are in this position, I help them identify weak links in their flea management plan and assure them that once we revamp the plan the end really will be in sight.


1. Hsu M-H, Hsu T-C, Wu WJ. Distribution of cat fleas (Siphonaptera: Pulicidae) on the cat. J Med Entomol2002;39:685–688.

2. Rinaldi L, Spera G, Musella V, et al. A survey of fleas on dogs in southern Italy. Vet Parasitol 2007;148:375–378.

3. Guzman RF. A survey of cats and dogs for fleas: with particular reference to their role as intermediate hosts of Dipylidium caninum. N Z Vet J 1984;32:71-73.

4. Little SE, Starkey LA. Conquering fleas: preventing infestations and limiting disease transmission. Today Vet Pract 2012;Nov/Dec:33-39.

5. Bowman DD. Arthropods. In: Bowman DD, ed: Georgis’ parasitology for veterinarians, 9th ed. St. Louis: Saunders Elsevier; 2008:5-83.

Dr. Joan Capuzzi is a small animal veterinarian and journalist based in the Philadelphia area.

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