Diagnosis of Flea Infestation

When a dog is heavily infested with fleas, they're easy to find. If you suspect a light infestation, look at the stomach and back (just in front of the tail). Part the hair and examine the skin closely for "flea dirt." Flea dirt is made up of fecal matter - or digested blood - from the flea. If you find it, fleas have been or are present.

Flea dirt looks like pepper. It varies from tiny black dots to tubular structures about 1/32" long. If in doubt, put the suspicious material on a light-colored surface. 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 becomes a solution. Another trick is to put some of the material on a white paper towel, then wet the paper towel with water. A red stain will become apparent as you gently wipe the material across the surface of the paper towel.

Many people find tiny drops of blood in a dog's bedding or where the dog 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 a Flea

To appreciate the complex issue of flea control, you must understand something about the flea's life cycle. Under normal conditions, you will only be able to see the final stage of the flea's 4-stage life cycle - adulthood - and adults represent only about 5% of the entire flea population.

Stage 1: Flea eggs are pearly white and about 1/32" in length. They are too small to see without magnification. Fleas lay their eggs on the dog, but the eggs do not stick to the dog's hair. Instead, they fall off into the dog's environment. The eggs make up 50% of the flea population. They hatch into larvae in 1-10 days, depending on temperature and humidity. The eggs hatch fastest in high humidities and temperatures.

Stage 2: Flea larvae are slender and about 1/8 - 1/4" 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 a pupae.

Moisture is essential for larvae survival; therefore, they cannot survive outdoors in shade-free areas. Outdoor larval development occurs only where the ground is shaded and moist, and where flea-infested animals spend a significant amount of time. This allows flea feces to be deposited in the environment. In an indoor environment, larvae survive best in carpet or between cracks in hardwood floors. They also thrive in humid climates.

Stage 3: Mature larvae produce a silk-like cocoon for the next step of development. 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 physical pressure, carbon dioxide, or 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 up to 3 weeks following insecticide application.

Stage 4: When the adult flea emerges from its cocoon, it immediately seeks a host because it must have a blood meal within a few days to survive. It is attracted to people and pets by body heat, movement, and exhaled carbon dioxide. It seeks light, which means that it migrates to the surface of the carpet so that it can encounter a passing host. Following the first blood meal, female fleas begin egg production within 36-48 hours. Egg production can continue for as long as 100 days, which means that a single flea can produce thousands of eggs.

This entire life cycle (egg > larvae > pupa > adult) can be completed in 14-21 days with the proper temperature and humidity conditions. 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 lead to the dog having an insufficient number of red blood cells, which is known as anemia. In young or debilitated dogs, the anemia may be severe enough to cause death.

Contrary to popular belief, most dogs have rather limited itching due to flea bites. However, many dogs become allergic to the saliva in the flea's mouth. When these dogs are bitten, intense itching occurs, causing the dog to scratch and chew on its skin.

Flea Control

As stated above, successful flea control must rid the dog and the dog's environment of fleas. In fact, environmental control is as important as treatment of the dog. If your dog 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 new topical products. However, the dog that goes outdoors frequently, or stays outdoors, presents a somewhat greater challenge and a few fleas may occasionally be seen indoors.

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

Newer, more effective sprays can be a valuable part of the overall treatment plan. They kill adult fleas rapidly and are safe enough to use daily, if necessary.

Flea sprays containing insect growth regulators are helpful in managing the overall problem because they help to break the flea life cycle. However, these are usually only recommended for weekly application. Always read the label first when using any new product on a dog. In general, flea sprays, collars, powders, and dips have become less popular since the introduction of newer products.

Four relatively new products have come onto the market in the last couple of years. The "flea pill" is an oral medication that is given to the dog once a month. This product, Program, does not kill adult fleas but is helpful in breaking the life cycle of the flea. When the female flea produces eggs, they are sterile and do not hatch. Three new topical treatments are applied to the nape of the neck; they are Advantage, Frontline Top Spot, and Revolution. All are safe and very effective.

Environmental Control

Newer topical products do not require the aggressive environmental control that is necessary if only dips, sprays, or collars are used. This is one reason that they have become so popular with pet owners. Please consult with your Valley View vet about the requirements for your specific situation.

When environmental flea control is indicated, it must be directed at your house and your yard.

House: Even though fleas may be in your house, you'll probably never see them. Fleas greatly prefer cats and dogs to people; they only infest humans when there has not been a cat or dog in the house for several days (with some exceptions). A professional exterminator may be called to treat your house, or you may use a house fogger or long-lasting spray. These foggers and sprays are very effective for adult fleas, but they will not kill adults that are still in their cocoon. You should look for 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.

Some companies will treat your carpet with a flea-killing powder that is nontoxic to people. It is worked deeply into the carpet to prevent it from being removed by vacuuming. This treatment has proven very successful, even in the face of heavy flea infestations. However, the treatment does not address fleas in your yard. The same chemical, a form of boric acid, is also available for application by the homeowner, but the self-application kits do not offer any guarantees.

Yard: A professional exterminator may also do yard control with various insecticides or you may use some 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, using a 30-day residual product each time. Your veterinarian can help you choose the most effective product for your situation.

Reemergence of Fleas

If you recall, pre-emerged adult fleas 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, pre-emerged adults remain in their cocoon. Even if the house was treated with an insecticide, their cocoon protects them. When people and pets return to the house, adults emerge from their cocoons and immediately begin to seek a blood meal. They jump on cats, dogs, and even people. Although it may appear that a dog just returned from boarding brought fleas to your home, it is also very possible that a sudden emergence of adult fleas may account for the fleas present. If large numbers of fleas are seen, they are almost certainly newly hatched fleas that were not brought home with the pet.