Fleas in Dogs and Cats: Prevention, Treatment, and How to Eliminate an Infestation

– by Justin Chan, DVM –

Fleas: The Itchy Bloodsucker

Picture this: it is a nice, calm afternoon, and Fluffy has just come in from doing his regular “business” outside. He is now standing by your feet with eyes that seem to ask why he has not been fed yet. As you prepare his hearty breakfast made with extra love, you suddenly notice him chewing at his back end as if something just bit him. Thinking nothing of it, you give him a meal fit for a king and return to your daily routine.

Fast forward a couple of days, and suddenly it seems that all Fluffy can do is itch. He itches during the day, he itches during the night, and he seems to have lost interest in doing the things he usually enjoys. You reach down to pet him and notice that he appears to be losing hair at the base of his tail and behind his thighs. Taking a closer look, you see that the skin is red and bumpy, and there are small black specks scattered throughout the area. Then BAM—one of the black specks suddenly jumps as if to greet you.

Startled, you jump back, and that is when it all clicks together.

“Oh no! Fluffy has fleas!”

This is a common scenario that veterinarians encounter on a regular basis. A dog that has never previously been itchy suddenly presents with unexplained scratching and discomfort. But what exactly are fleas, and how did our dear friend Fluffy get them?

 

What Are Fleas and How Do Pets Get Them?

Fleas are tiny, wingless insects that survive by feeding on the blood of animals and humans. They are particularly known for their incredible jumping ability and their tenacity. Fleas can live on virtually any mammal but prefer cats, dogs, opossums, rats, and other rodents.

Oftentimes, fleas are introduced into an area by wildlife or feral animals that travel through your pet’s favorite outdoor spaces and leave a few unwanted hitchhikers behind. The fleas then lie in wait until a warm-blooded animal passes by, quickly taking the opportunity for an easy meal.

Fleas can also be transmitted through direct contact with infested animals. If Fluffy recently interacted with another animal carrying fleas, he may have picked them up that way.

 

How Can I Prevent and Get Rid of Fleas?

Thankfully, there are several effective options available to help prevent fleas.

Topical products such as Seresto (permethrin), Frontline (fipronil), Revolution (selamectin), and Advantage II (imidacloprid) have been on the market for 15–30 years and are typically effective at preventing fleas when used properly and when an active infestation is not already present.

Unfortunately, it is becoming increasingly common for pet owners to report flea problems despite consistently using these products. Although improper application can sometimes reduce effectiveness, it is also likely that fleas have developed resistance to some of these medications over time due to their long-term use.

Outside of veterinary medicine, compounds such as fipronil, permethrin, and imidacloprid have historically been used in large-scale pest control operations. As a result, overuse of these products has likely contributed significantly to the development of resistance.

Due to the increasing resistance seen with some topical products, the veterinary industry has largely transitioned to medications in the isoxazoline drug class for flea and tick prevention. This medication class is used exclusively in veterinary medicine and first became available in 2014.

Medications in this class include Bravecto, NexGard, Simparica, and Credelio. While resistance may eventually develop in the future, we remain hopeful that these medications will continue to provide effective protection for years to come.

Because these medications require a prescription and veterinary oversight, discuss with your veterinarian whether an isoxazoline product is appropriate for your pet.

 

I Started My Pet on Flea Prevention, But I’m Still Seeing Fleas. Why?

Achieving flea control after an infestation develops requires a multifaceted approach. Not only do we have to treat the fleas on the pet, but we also have to address the fleas living in the environment.

To understand why, it helps to understand the flea life cycle.

There are four distinct life stages of a flea: egg, larva, pupa, and adult.

When fleas hatch from eggs, they emerge as larvae. During this stage, the larvae move freely and feed on organic matter and adult “flea dirt” (feces) to obtain the nutrition needed for development. Oftentimes, larvae do not live on the host animal. Instead, they burrow deep into carpets, soil, and other materials where they remain protected.

Once the larvae have developed appropriately, typically within 5–20 days, they form a protective cocoon and enter the pupal stage. During this phase, the cocoon protects the developing flea and renders most insecticides ineffective.

Fleas can remain in the pupal stage for days, weeks, or even longer until they detect vibrations, warmth, or carbon dioxide from a nearby host. Once triggered, the adult flea emerges, finds a host, begins feeding, and starts reproducing.

Within hours of feeding, adult fleas can mate and begin laying eggs, continuing the cycle all over again.

Because fleas can remain protected in the pupal stage for extended periods, it can take up to 90 days to fully eradicate a flea infestation.

 

What Can I Do to Eliminate a Flea Infestation?

As discussed above, both the pet and the environment must be treated aggressively for a minimum of 90 days to completely eliminate a flea infestation.

• Consult your veterinarian for a topical or oral flea prevention; they may recommend an isoxazoline product due to its long duration of action and proven effectiveness. Products such as Bravecto, available in oral and topical forms, provide protection for up to 90 days and can help keep your pet protected throughout the flea eradication process.
  
  
• Explore an injectable formulation of flea prevention. Bravecto Quantum provides up to 12 months of protection against fleas and most tick species, eliminating the need to administer flea and tick medications every 30–90 days.
  
  
• Once your pet is on an effective flea control product, the next step is treating the environment. Hiring a professional pest control company is always an option. However, with some elbow grease and dedication, many flea infestations can be managed successfully at home.
  
  • Start by washing and drying all washable bedding, sheets, blankets, and similar items using high heat settings for both cycles. If an item cannot be washed, place it in a sealed trash bag for 4–8 weeks to ensure that any fleas, larvae, and pupae have died. Store the bag away from other fabric-based items in case the seal is compromised.
    
    
  • For rugs and carpets, vacuum thoroughly at least once weekly throughout the entire 90-day treatment period. Bagged vacuums are ideal because the contents can be quickly disposed of in an outdoor trash receptacle, preventing any surviving fleas from escaping back into the home.
    
    
  • Furniture is often one of the most challenging areas to treat due to its size and the difficulty of thoroughly vacuuming every surface. When possible, vacuum furniture aggressively and follow up with an environmental treatment product such as Knockout Spray by Virbac.
    
    
• Over-the-counter area flea treatment products may also help reduce flea populations. Be sure to follow the manufacturer’s instructions carefully regarding application frequency, duration, and safety precautions. Most of these products require people and pets to stay out of treated areas during application and for a specified period afterward. Always ensure the area is adequately ventilated before re-entry.

 

Conclusion

Fleas are resilient pests and can be frustrating for both pets and their owners. However, with a comprehensive approach that treats both the pet and the environment, most flea infestations can be successfully eliminated.

Unless you live in an area completely free of wildlife and stray animals, it is highly likely that your pet will encounter fleas at some point in life. As with most health concerns, prevention is far easier than treatment.

Talk with your veterinarian about which flea prevention product is best for your pet and how to develop an effective long-term flea control plan.

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