Fleas in Puppies and Dogs

Fleas are a real health hazard

Dog scratching fleas

Carol Yepes / Getty Images

There are more than 2,200 species of fleas recognized worldwide, but only a handful affect dogs in North America The cat flea is the most common flea that infests dogs and can cause far more than itching. To pick the best anti-flea weapons, you must first understand the enemy. The adult flea you find crawling through your puppy’s fur could represent the tip of the iceberg. Fleas can cause allergies and anemia and transmit tapeworms; they are also the agent that causes cat scratch disease.

Signs of Fleas in Dogs and Puppies

Puppies with fleas are usually quite itchy and this can impact both your pet's quality of life and your own. Fleas prefer the back end of dogs causing your pet to chew at its flanks and above its tail region. If you part your pet's fur you might see "flea dirt," which looks like tiny black specks. This is digested blood present within the feces of the adult flea. Flea dirt appears red when placed on a damp cloth or paper towel.

Pets with flea allergies have severe itching in response to a single flea bite. These pups are allergic to the saliva from the flea. Products that both repel and kill fleas work best for dogs with flea allergies.

illustration of signs your dog has fleas
The Spruce / Kelly Leigh Miller

Causes of Fleas

Fleas are flightless external parasites of both birds and mammals. About 1/10-inch long, they have flat bodies and strong claws that make it easy to cling to a host's skin, fur, or feathers. Fleas have mouthparts that allow them to pierce the skin and drink blood. When on the move, fleas can hop long distances. Adult fleas represent only 5 percent of the total flea population; the remaining 95 percent, composed of flea eggs, larvae, and pupae, lurk in the surrounding environment.

Flea bites cause itching and in dogs with flea allergies, signs can progress to skin swelling, irritation, ulceration, and hair loss. Fleas also carry a wide range of diseases, some of which are deadly. Flea-borne diseases have ravaged human communities and can have a devastating impact on pets.

Fleas can lay 20 to 40 eggs per day, and it only takes 10 female fleas to create almost 250,000 different life stages in a single month. Newly emerged flea larvae can survive two weeks without a blood meal, and pre-emerged fleas (pupae/cocoon stage) can survive six months without feeding.

Treatment

Treating fleas involves removing and killing existing adult and juvenile fleas. Flea products address the egg, larvae and adult stages, but no insecticide kills the cocoon (pupal) stage. Until all the immature fleas have hatched out of the pupae in their environment, you will continue to see fleas, therefore you must wait until it hatches to kill it. It takes 14 to 21 days for the lifecycle to be complete.

Many pet owners want to pursue non-chemical flea control methods. The safest and most “natural” flea control technique involves using a flea comb and entails manually removing fleas, eggs, and flea dirt. Frequent vacuuming of the carpet removes up to 90 percent of flea eggs and 50 percent of larvae. You must also wash pet beds, carriers, blankets, and throw rugs as well as any sofa cushions or other favorite pet resting places.

Bathing puppies can get rid of existing fleas but won't necessarily keep them off. Be cautious of so-called "natural" flea products as they may still be dangerous for youngsters.

While the above-mentioned options can help reduce flea populations, products that contain insect growth regulators (IGRs) are the best choice for precise control because they prevent immature fleas from maturing into biting adults. They typically last a long time with a single application, some as long as seven months.

IGRs attack insects but not the pet and are one of the safest of the flea ingredients around. For example, methoprene fools flea larva into thinking it’s a larva forever, so it never turns into a biting adult flea. Another early IGR called lufenuron (once-monthly pills for your pet) inhibits the development of the exoskeleton of the flea and sterilizes the bug so it can’t reproduce. Pyriproxyfen (Nylar) works like methoprene but with an increased potency that also kills flea eggs and larva.

A better understanding of flea biology also helped researchers to develop ingredients that specifically attack the flea's nervous system. These include imidacloprid (Advantage), fipronil (Frontline), selamectin (Revolution), and nitenpyram (Capstar.) These are applied as spot-on treatments once a month. Each of these four active ingredients takes 24 to 48 hours to be fully effective and each offers slightly different benefits.

  • Imidacloprid kills adult fleas and has a month-long effect.
  • Fipronil also kills adult fleas for a month as well as ticks.
  • Selamectin protects for a month against a host of pests including fleas, ear mites, heartworms, and certain types of ticks.
  • Nitenpyram, taken as a pill, kills adult fleas that feed on a treated pet within 20 minutes but is only effective for 24 hours and isn’t helpful for flea-allergic animals.

Some of the most effective flea and tick products today combine an adulticide to kill adult fleas with an IGR to control the immature bug population. You can find a fipronil and methoprene combination product that kills fleas and ticks (Frontline Plus), as well as etofenprox partnered with pyriproxyfen (Nylar) or methoprene in various over-the-counter spot-on products that help control fleas and ticks. Products that contain imidacloprid with permethrin (K-9 Advantix, for dogs only) or spinosad (Comfortis for dogs) also are available.

How to Prevent Fleas

Fleas hate direct sunlight and prefer outdoor shaded areas with sand, leaves, or other debris. So, in part, the lifestyle of your puppy determines their risk for exposure. Indoor couch potato pups probably don't need the same protection as hunting dogs that roam in the field. But even pups that visit the yard on a leash have enough exposure to warrant flea protection.

Keep the grass on your lawn short to ensure enough sunlight. Most parasites find this an unappealing environment. Keeping pets away from problem areas and treating the bug habitats helps reduce the pest population. Nematodes—worms that eat immature fleas—are available from lawn and garden supply outlets.

Age and overall health status influence the type of product you should choose. Read the label carefully to make sure the flea or tick protection says it’s safe for your pets. For example, some products are unsafe for puppies.

While parasites are most active during warmer months and they are susceptible to extreme cold, it's hard to predict when fleas are most likely to be a problem. Thus, the Companion Animal Parasite Council (CAPC) recommends year-round protection against fleas and ticks.

Consult with your veterinarian about how to best protect your puppy in the battle against fleas. The most effective products are available only by prescription. If you choose an over-the-counter product, examine the label carefully and strictly follow product instructions to ensure the health and safety of your pets.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.