Flea Problems in Pets

posted: by: CCVC Tags: "Clinic Specials" "News" 

Flea Problems in Pets

General Information:

Flea season begins as soon as daytime temperatures start to hit 60o and continues until the ground freezes in the late fall/early winter.  The number of fleas increases throughout the season, making flea problems worst during the fall months.  Fleas only spend 5-15% of the time on the animal.  The rest of the time they are in the environment.  The egg, larvae, and pupae stages make up about 95% of the flea life cycle and are always present in the environment.  This means that for every flea seen, there are hundreds more that are not seen. In addition, fleas reproduce very quickly. A small number of adult fleas can generate hundreds of thousands of fleas within a few months. 

Fleas are programmed to find a source of food (a warm animal), and good warm places (a warm animal and a heated home) to reproduce, to keep their population growing over the winter, so we still see problems with fleas after the ground freezes.  Some pets may also encounter wild animals outside who might be infested, including their housing/dens, with fleas.  These facts are important to keep in mind as to why monthly, year-round prevention is important for those pets still going outside in winter. 

Once a flea infestation occurs, it usually takes a minimum of four to eight weeks to completely eradicate the flea population.  Even the most effective prescription-strength medications on the market today cannot treat the pupae stage.  For this reason, treating an existing flea problem requires both diligence and patience.  It is recommended, therefore, that all at-risk animals be on preventative therapy monthly for pets still going outside in winter, or from mid-March until a hard fall/winter freeze for those who don't go outside in winter.  By using preventative therapy, it is possible to avoid most flea infestations.

Flea Life Cycle:

Eggs:  Flea eggs are so tiny that they are very difficult to see without magnification.  They are present in the soil, carpet fibers, bedding, in cracks between floor boards, and other such places in your pet's environment.  Eggs hatch in two days to two weeks depending on environmental conditions.

Larvae:  Fleas in the larval stage are wormlike creatures, ¼" in length and not much thicker than a thread.  They live in the environment and feed on the excrement of the adult fleas and other organic debris.  Generally, this life stage lasts about five to 18 days before the larva spins a silken cocoon and moves into the pupa stage.

Pupae:  The pupal stage is the most frustrating of all life stages for several reasons.  First, the pupae are dormant in a well-armored cocoon anchored firmly in the environment and are, thus, not affected by any of the flea products currently on the market.  Second, the length of this stage varies greatly from three days to a year or more. This can make it difficult to completely eradicate fleas once they are well established in the environment. 

Adult:  This is the flea stage that most affects people and their pets.  Fleas eat only blood meals from their host, but do not remain on the host.  In fact, fleas usually only spend 5-15% of their time on your pet.  An adult female can lay up to 50 eggs a day and lives for several months.

While the length of the life cycle is highly variable depending on conditions, in the typical home environment, the cycle lasts about six weeks. For this reason, it is very important to treat fleas aggressively for at least two consecutive months in order to ensure eradication of the population.  With well established infestations, it is necessary to treat all pets on the premises (both indoor and outdoor), the house, and sometimes the yard during this period.

Flea Allergies:

Flea allergies occur when your pet is hypersensitive to the saliva that a flea leaves behind when it bites your pet.  Pets with flea allergies do not necessarily have a visible "flea problem" because it only takes one or two flea bites to set off an allergic reaction lasting for many days.  In most cases, however, the fleas or signs of flea exposure (flea dirt) can be seen on your pet's skin.

Pets with flea allergies typically have a distinct pattern of itchiness, hair loss, and/or skin changes that can be identified on a physical examination.

Flea infestations and flea allergies can be treated and the recurrence of signs prevented by applying one of the prescription-strength flea products to your pet on a MONTHLY basis.  Most over-the-counter products that are sold at pet stores and groceries are simply not strong enough to kill every single flea and prevent the allergic reaction.  It is recommended that pets with flea allergies be kept on flea prevention year-round to prevent future break-outs and the need for aggressive treatment of the house and lawn beyond the first treatment sequence. In multi-pet households, it is ESSENTIAL to treat every pet in the household and on the property (including outdoor only animals), not just the pet with the visible problem.  If this is not done, fleas can live on the untreated animals and the flea problem can persist. 

Treating Your House:

This is usually only necessary if a flea population becomes established within your home.  Most of the prescription-strength products are so effective at prevention, that this step is not necessary if your pets are receiving monthly prevention. 

For established infestations or in cases of flea allergies, home treatment becomes VERY important.  It is essential to treat the house in order to get flea populations and flea allergies under control.  While you may never actually see the fleas in your home, know that they are there hiding in the carpet and upholstery.  Fleas spend less than 15% of their time on your pet.  The rest of the time, they are hiding in your house.  If you do not treat the house, the fleas cannot be effectively eradicated.  This becomes especially important if your pet has flea allergies.

Area spays such as Knock Out® (available at CCVC) are more effective than foggers because they can be sprayed under furniture, behind furniture, and in the corners of the rooms where the foggers won't reach.  Knock Out® kills adult fleas, flea eggs and flea larvae.  Repeat use in six weeks to kill fleas that emerge from the pupae stage.  Areas should always be well-ventilated and all pets and people should be out of the treated area until the area has had time to dry completely (at least several hours). 

Before treatment, the areas should be well vacuumed and the vacuum bag discarded. If using a canister vacuum, be sure to empty the canister, and spray the canister with Knock Out.  When treating, be sure to spray the product uniformly to lightly cover the entire area without saturating.  Lift or tilt furniture to spray underneath and behind, remove couch cushions and spray underneath, spray beneath tables, chairs, etc.  Start at one end of the room and work backward toward the exit.  Once a room has been sprayed, do not re-enter it until the area is completely dry.  Pet owners who do not wish to treat the house themselves should contact an exterminator to arrange for service.

In addition to chemically treating the house, it is a good idea to wash all of the pet bedding, blankets, stuffed toys, and household bedding in the hottest temperature water recommended, using bleach whenever possible.  This kills flea eggs and larvae in these hard-to-treat areas. 

This entire process of spraying and thorough cleaning should be repeated again six weeks later.  This ensures that fleas in the pupae stage at the time of initial treatment are killed once they emerge (virtually nothing will kill fleas in the pupae stage).  The pupae stage can last up to six weeks under normal household conditions dictating the necessity for this six-week treatment interval.  After two house treatments six weeks apart, there should not be a need for further house treatment as long as prescription flea prevention is used year-round and your pet is not suffering from flea allergies.  Avoid the need for future house treatments by continual use of prescription strength flea prevention year-round.

Treating the Yard:

For many pets, the yard is the place where flea infestations begin.  In cases of severe flea allergies, for flea infestations that remain uncontrolled after two months of aggressive treatment, or when choosing pet flea treatments that don't have flea repelling properties, it is important to treat the yard as well as the house. 

A variety of products are available for yard treatment.  Some are spray bottles that attach to a garden hose for fast and easy distribution, while others are dusts or granules that can be sprinkled on the surface of the lawn.  Lawn treatment companies and exterminator services can often provide professional yard treatment if that is desired. 

Regardless of the treatment option chosen, it is important to closely follow product recommendations regarding safety for both pets and people following treatment.  Never allow your pet to eat the grass or other vegetation on a treated lawn.  Just as with the house treatment, it is important to retreat according to product recommendations (usually every week to ten days, especially after a rain unless using time-release granules) to ensure that all fleas in the pupae stage at the time of initial treatment are killed.

In some cases, a series of lawn treatments covering a six-week interval is enough to stop the flea infestation.  In other cases, repeated treatments through the warmer months may be necessary at regular intervals.  This is especially true if adjacent neighbors have pets and are more lax on flea control or if the yard is shared by wildlife species such as raccoons, opossums, or deer.  The degree of flea sensitivity of your pet may also dictate the frequency and extent of yard treatment required for complete flea allergy control.

Flea Treatment Check-list for Persistent Flea Infestations

Answer "Yes" or "No" to each of the following questions:

______ Have I been treating the current flea problem for at least two months?  If "no", please review the flea life cycle.  Nothing kills the pupa stage.  Newly emerged adult fleas may be seen for four to eight weeks after treatment begins.  Be patient and diligent in treating the problem.

______ Have I treated ALL pets on my property including barn cats, outdoor only cats and dogs, and small exotic mammals?  If "no" these animals are probably serving as reservoirs for the flea population.  All animals on the premises MUST be treated for two consecutive months.

______ Have I treated both the house and the yard according to the recommendations in this handout?  If "no" these treatments may be necessary before the flea population can be completely eradicated.

______ Have I carefully read all instructions on all flea products before using them and followed all instructions exactly as written?  If "no" go back and re-read product instructions or ask one of our staff members to verbally explain the proper use and application of each product.  Flea control products cannot work if they are not used properly.  Topical products must be applied directly to the skin, not to hair.  This is a common mistake made in product application.

______ Have I used products recommended specifically by the veterinarians and staff at CCVC?  If "no" be sure to ask for recommendations and try the products that we recommend.  Not all flea products are created equal.  Over time, fleas develop resistance to the active ingredients of many products.

______ Am I sure that this is truly a flea problem?  If "no" be aware that bites from chiggers, bedbugs, and other parasites are sometimes misidentified as flea bites in humans.  Animals who are still itching despite flea treatment may have allergies or other skin parasites.  If no fleas or flea dirt are currently seen, it may be time to consider other causes for the problems.


If you answered an honest "yes" to every question above, you may need to take more unconventional actions to eradicate the flea infestation.  Consider the following suggestions:

1.       Wildlife and/or stray/feral domestic animals may be bringing fleas onto your property and serving as a reservoir for the flea population.  Wildlife deterrent sprays or fencing may be helpful.  It may be necessary to trap and relocate animals that are residing on your property.

2.       Fleas may be infesting areas such as crawl spaces or attics that that are not easily accessible for standard home treatments.  While it is rare for fleas to inhabit these remote regions of the house, it can happen.  If you have exhausted all conventional treatment options, it is time to call a professional exterminator.  Be sure to get a written guarantee that the treatment they provide will eliminate the problem.  If you are having trouble controlling the problem with conventional means, an exterminator may not be successful with their standard treatments.  A written guarantee will ensure that you are not paying for their services again and again.