Why Fleas Surge in the Fall

The "dog days" of summer are almost behind us, but that doesn't mean your pets can get by without flea protection. In fact, in most areas, fall is the worst season for fleas. Dr. Michael Dryden, professor of Veterinary Parasitology in the Department of Diagnostic Medicine and Pathobiology at Kansas State University College of Veterinary Medicine, Manhattan, calls it "the fall flea surge."

Dryden discovered that the number of fleas on animals in the fall were 70 percent higher than in the spring! He theorized that the "flea surge" occurs because in the fall there is generally an increase in precipitation and the temperatures stay around 70 degrees. Fleas thrive in these conditions. In fact, in the fall, pet owners tend to believe that their flea prevention program isn't working because the fleas are so abundant!

Fleas reproduce very efficiently. They start feeding on the blood of your pet within fifteen minutes upon their arrival and within 24 hours, they begin to breed. Each female flea will lay approximately 28-50 eggs per day.

The eggs are sticky at first but after a short time, they dry and fall off your pet into the environment and can hatch within 2-5 days. While it's possible to bring a flea into our environment on our clothing, unprotected pets are most likely the ones that deliver them; several at a time. "This is another reminder that cats that go outdoors at all also require protection," Dryden notes.

It is also important to remember in order to effectively eliminate fleas you must treat the environment as well as the pet. This means the carpet, furniture, beds and yards. Dryden also notes that home infestations occurring in the fall may exceed those in spring. Flea eggs that have fallen off the pet eventually hatch into larvae. Since larvae do not like light, they burrow down into the carpet or into fabric fibers where they remain for the next 7-14 days preparing to become pupae.

Pupae are protected by a cocoon the larvae spin and remain dormant until the conditions are right for the adult flea to emerge. The hatch can be stimulated by vibration such as vacuuming, walking or running, changes in light, carbon dioxide or the ideal temperature. Temperatures above 85 degrees encourage the dormant state, but when the temperature hovers around 70 degrees, fleas will begin hatching in very large numbers and they can live in a warm house all year round.


In the fall, pets begin getting their winter coats making them ideal homes for fleas to feed and breed. The thicker coat also makes it more difficult to groom fleas off. Plus, only 5% of the fleas you see are the adult fleas, which means, that 95% are in the stages you don’t see, the egg, larvae and pupae stage.

If you only treat the adult fleas, it won't be long before you get another infestation. Flea products that contain an IGR, insect growth regulator, are the most effective against fleas; as they not only kill the adult flea stage, they also inhibit the growth of the immature flea stages.

A few topical products that control fleas in this manner are: Advantage® II, K-9 Advantix® II and Frontline® Plus. There are also oral products, like Capstar® & & the prescription product, Sentinel®, that work to eliminate flea populations this way as well. Sentinel® is an effective oral flea treatment that contains lufenuron. Lufenuron is an insect development inhibitor that has been proven to be 100% effective in preventing flea populations and can also be used in combination with flea adulticides. Sentinel® also has the added benefit of preventing heartworm disease. There are many good flea and tick treatments to choose from. Your veterinarian can recommend which products will be most beneficial for your pet's circumstance.


Does your pet roam around your house, sit on your lap or sleep in your bed? Everywhere your pet goes, flea eggs are being shaken off. Remember, the larvae like to bury themselves in carpet and material fibers to get away from the light. If you don't do anything about them, they eventually hatch when the conditions are right and the flea cycle starts all over again.

First, vacuum floors and furniture to suck up as many of these unwanted pests as you can and discard the vacuum bag. To eliminate the stages you can't see use sprays like Siphotrol® Plus II Premise Spray and Zodiac® FleaTrol Fogger. A product that contains an IGR works best as it will affect the remaining eggs and larvae and lay down a residue to kill the adults when they emerge. Be sure to use Health Guard Laundry Additive & Disinfectant to launder all blankets and bedding as well.


A flea can jump up to 8” high and 12” laterally. Your pet is not only shaking the eggs off into their favorite places, the hatched adult fleas are re-boarding your pet the minute they walk by. They are not picking up these fleas in the middle of your yard in direct sunlight. They are picking them up under bushes, decks and trees; and other places where untreated wildlife frequently visit. Your outdoor treatment should focus on these areas. We suggest using Adams Plus Yard Spray, Tempo®, or Permethrin 10%.

Fleas are not just a parasite problem, they are a medical problem. Fleas spread diseases, as well as tapeworms, when they feed on your pet's blood. Protect your pet from fleas' harmful effects by effectively eliminating them from your pet and your environment.

If you need help, call us at 1-800-786-4751.

-Dr. B
Don Bramlage, DVM, Director of Veterinary Services at Revival Animal Health

The materials, information and answers provided through this website are not intended to replace the medical advice or services of a qualified veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.

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