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Medical Watch

Flea Control for Dogs and Cats

The following information is provided as a public service only, and is NOT intended to replace the advice or recommendations of your pet’s veterinarian.

Flea Control for Dogs and Cats 

Successful flea control has two aspects.  Fleas must be controlled on your pets, and fleas must be controlled in your pets' environment.  Since cats and dogs share the same fleas, the presence of both species in your pets' environment can make flea control much more difficult.  All pets in a household must be effectively treated, even if it appears that only one pet is being bothered by fleas. 

Diagnosis of Flea Infestation 

When a dog or cat is heavily infested with fleas, it is easy to find the fleas.  If the numbers are small, it is best to quickly turn your pet over and look on its belly.  If you do not find fleas there, look on the back just in front of the tail.  Be sure to part the hair and look at the level of the skin.  Also look for "flea dirt."  Flea dirt is digested blood left behind by the fleas.  Flea dirt is actually fecal matter from the flea.  Finding flea dirt is a sure indication that fleas are present or have been present recently.   

Flea dirt looks like pepper.  It varies from tiny black dots to tubular structures about 1/32" (1-2 mm) long.  If you are not sure it is flea dirt, put the suspected material on a light colored tabletop or counter top.  Add one or two drops of water and wait about 30 seconds.  If it is flea dirt, the water will turn reddish brown as the blood residue goes into the solution.  Another trick is to put some of the material on a white paper towel and then wet the paper towel with water.  A red stain will become apparent if you gently wipe the material across the surface of the paper towel. 

Many people find tiny drops of blood in a pet's bedding or where the pet sleeps.  This is usually flea dirt that was moistened, then dried.  It leaves a reddish stain on the bedding material and is another sign that fleas are present. 

Life Cycle of the Flea 

To appreciate the complex issue of flea control, you must understand something about the flea's life cycle.  Although you are only able to see the adult flea, there are actually 4 stages of the life cycle.  The adult flea constitutes only about 5% of the entire flea population if you take into account all four stages of the life cycle.  Flea eggs are pearly white and about 1/32" (1-2 mm) in length.  They are almost too small to see without magnification. Fleas lay their eggs on the pet, but the eggs do not stick to your dog or cat's hair.  Instead, they fall off into the pet's environment.  The eggs make up 50% of the flea population.  They hatch into larvae in 1 to 10 days, depending on the temperature and humidity in the environment.  High humidity and high temperature favor rapid hatching. 

Flea larvae are slender and about 1/8-1/4" (2 - 5 mm) in length.  They feed on organic debris found in their environment and on adult flea feces, which is essential for successful development.  They avoid direct sunlight and actively move deep into carpet fibers or under organic debris (grass, branches, leaves, or soil).  They live for 5 to 11 days before becoming pupae. 

Moisture is essential for their survival; flea larvae are killed by drying.  Therefore, it is unlikely for them to survive outdoors in areas of strong, direct sunlight.  Outdoor larval development occurs only where the ground is shaded and moist and where flea-infested pets spend a significant amount of time.  This allows flea feces to be deposited in the environment.  In an indoor environment, larvae survive best in the protected environment of carpet, along baseboards, under and inside upholstered furniture, or in cracks between hardwood floors.  They also thrive in humid climates. 

Following complete development, the mature larvae produce a silk-like cocoon in which the next step of development, the pupa, resides.  The cocoon is sticky, so it quickly becomes coated with debris from the environment.  This serves to camouflage it.  In warm, humid conditions, pupae become adult fleas in 5-10 days.  However, the adults do not emerge from the cocoon unless stimulated by vibrations, carbon dioxide, and heat.   

Pre-emerged adult fleas can survive up to 140 days within the cocoon.  During this time, they are resistant to insecticides applied to their environment.  Because of this, adult fleas may continue to emerge into the environment for several weeks following insecticide application. 

When the adult flea emerges from its cocoon, it immediately seeks a host because it must have a blood meal within a few hours to survive.  It is attracted to people and pets by body heat, movement, and exhaled carbon dioxide.  Following the first blood meal, female fleas begin egg production within 24 to 48 hours. One female flea typically produces 40 to 50 eggs per day. Egg production can continue for as long as 100 days, which means that a single flea can produce thousands of eggs in her short lifetime! 

This entire life cycle (adult flea >>> egg >>> larvae >>> pupa >>> adult) can be completed in 14-21 days with the proper temperature and humidity conditions, but it may also take much longer if environmental conditions are not ideal.  This adds to the problem of flea control. 

If untreated, the female flea will continue to take blood for several weeks.  During that time, she will consume about 15 times her body weight in blood.  Although the male fleas do not take as much blood, they, too, contribute to significant blood loss.  This can cause a pet to have an insufficient number of red blood cells, which is known as anemia.  In young, small or debilitated dogs and cats, this anemia may become severe enough to cause death.  

Flea Control 

Successful flea control must rid your pets of fleas and it must rid your pets' environment of fleas.  In fact, environmental control is as important as treatment of your pet.  If your dog or cat remains primarily indoors and you do not have other pets that come in from the outside, environmental control is relatively easy, especially with the advent of the newer topical and oral products (see below).  However, the dog or cat that goes outdoors frequently, or stays outdoors, presents a greater challenge and a few fleas may occasionally be seen indoors. 

Many of the older insecticides (which have been the mainstay of flea control for years) have limited effectiveness against fleas because they are only effective for a few hours after application on the pet.  Also, these are primarily geared to kill adult fleas.  Flea powders, sprays, and shampoos will kill the fleas present on your pet at the time of application.  However, most of these products have little or no residual effect, so fleas that return to your pet from his environment after the pet is treated are not eliminated by these products.  Thus, your dog or cat may be covered with fleas within a day after having a flea bath or being sprayed or powdered.   

However, there are some newer, more effective sprays that can be a valuable part of the overall treatment plan.  Some kill adult fleas only.  Flea sprays containing other ingredients, called “insect growth regulators”, are helpful in managing the overall problem because they help to break the flea life cycle by decreasing the number of flea eggs that hatch.  In general, flea sprays, collars, powders and dips have become less popular since the introduction of the newer, safer and more effective products. 

Newer Products 

Program^TM (Sentinel^TM) is a meat-flavored, monthly “flea pill”.  This medication does not kill adult fleas but it does kill flea eggs and larvae.  When the female flea produces eggs, the eggs do not hatch.  In effect, this product acts like a birth control product for the flea.  Giving this product has the effect of treating your house for fleas without spraying anything in your house.  This very safe product is available for both dogs and cats.  The monthly pill for dogs is available alone (Program^TM tablets) or combined with Interceptor^TM, a very effective heartworm preventative and intestinal worm treatment. This combined meat-flavored tablet is called Sentinel^TM.  Cats may also take a monthly Program^TM tablet or monthly Program^TM liquid oral preparation. In addition, there is an injection available for cats to be administered by your veterinarian which will provide the Program^TM flea egg control for 6 months after a single injection.  Because of its effectiveness in controlling the flea egg population, the consistent use of Program^TM (or Sentinel^TM) is an excellent way to help prevent a flea infestation from occurring in your home in the first place! 

Comfortis^TM is another meat-flavored “flea pill” that is administered once a month to kill the adult stage of the flea.  It is currently approved for use in dogs only, but research is ongoing regarding a possible future formulation for cats.  Comfortis^TM  has one big advantage over the topical monthly medications discussed below - it kills the adult fleas on your pet much faster, thereby reducing the number of flea eggs shed into your pet's environment.   

Trifexis^TM for dogs is the newest entry in the flea control armamentarium.  This monthly meat-flavored tablet is actually a combination of a very effective Heartworm preventative and intestinal worm treatment (the same active ingredient that is in Interceptor^TM) and the adult flea treatment, Comfortis^TM. 

There are several topical treatments that are applied to the back of the pet's neck.  Frontline Plus^TM and Advantage^TM are two very effective products; because they remain topical and are not absorbed through the skin they are also extremely safe.  Both kill adult fleas for approximately one month.  There are many other products that are designed to be used once a month and are applied in a similar manner to these two.  All have specific advantages and disadvantages.  Ask your veterinarian about any of these products prior to using them.  Be careful!  Some of these other products cause severe illness or fatalities if used on cats or debilitated dogs.  Never use any flea product that is labeled “for dogs only” on a cat; fatal reactions can occur!   

If you have any pet species other than dogs or cats in your household, check with a veterinarian familiar with the species to determine which product(s) will be most safe and effective for them. 

Environmental Control 

The newer oral and topical products do not require the aggressive environmental control that is necessary if only dips, sprays, or collars are used.  This is one reason why they have become so popular with pet owners.  Many people try the newest products for 1-2 weeks to see if they provide adequate flea control alone.  Please consult with us about the requirements for your specific situation.   

When environmental flea control is indicated, it must be directed at both your house and your yard. Remember:  adult fleas live on animals; flea eggs, larvae and cocoons are everywhere else. Therefore, when treating the environment, concentrate on killing those eggs and larvae!  Remember also, no chemical will kill the cocooned pupal stage of the flea.  The only way to eliminate the cocooned stage is to wait for the adult flea to emerge, and then kill the resulting adult flea.  Your veterinarian will be able to help you choose the most effective products for your situation. 

House.  Even though large numbers of flea eggs, larvae and cocoons may be in your house, most people never see them.  A professional exterminator may be called to treat your house or you may use a house fogger or a long-lasting spray.  You should purchase a fogger or a spray that kills the adult fleas and inhibits development of the eggs and larvae.  In climates with extended warm temperatures and high humidity, it may be necessary to treat two or three times with a 30-day residual product before all stages of the fleas are removed from the house.  The second treatment is most effective if it is done 2 weeks after the first. 

As a rule, flea eggs and larvae tend to concentrate at the edges of rooms, along the baseboards, under furniture, inside upholstered furniture and deep inside carpets.  Thus, sprays applied directly to these areas are generally more effective than foggers.  Fogger mists tend to fall out of the air in the center of the room, and access areas under and inside furniture very poorly.  Fogger sprays also do not turn corners well, so an individual fogger is generally necessary for each room in the house.  Therefore most homes require less product to be used if sprays are utilized instead of foggers. 

Yard.  Yard control may also be done by a professional exterminator or with various products you may use yourself.  Be sure that any insecticide that you use has a 30-day residual.  This keeps you from having to spray every week.  In climates with extended warm temperatures and high humidity, it will often be necessary to treat monthly during the warm months of the year.  You should use a 30-day residual product each time. Concentrate your spraying to the cool, moist areas of your yard, especially the areas where your pets like to stop and rest.   

Re-emergence of Fleas 

If you recall, a pre-emerged adult flea can survive up to 140 days within the cocoon.  This is significant when your pets are gone from home for extended periods of time.  During the time that the house is quiet and empty, the fleas present in your home continue their development from egg to larvae to cocoon.  But without their mammalian hosts' activity in the house, the pre-emerged adults remain in their cocoons.  Even if the house was treated with an insecticide, their cocoon protects them.  When people and pets return to the house, the adult fleas emerge from their cocoons en mass and immediately begin to seek a blood meal.  They jump on cats, dogs, and even people.  Although it may appear that a pet just returned from boarding brought fleas into your home, it is also very possible that a sudden emergence of adult fleas from their cocoons may account for the fleas present.  If large numbers of fleas are seen, they are almost certainly newly hatched fleas and have not come home with your pet. 

Re-cap: 

To effectively control fleas, you must kill all of the flea eggs and larvae in your pets' environment, prevent the flea eggs from hatching, or kill all of the adult fleas before they have a chance to lay eggs. A “multi-modal approach” (doing all of these things) is usually the most effective way to control these hardy parasites.

For an appointment at Striegel Animal Hospital, please call (618) 457-4133.