Animal Hospital at Thorndale, INC.

Flea Control for Cats

It is very difficult to control fleas in a cat that spends most of its time out of doors
It is very difficult to control fleas in a cat that spends most of its time out of doors

At certain times of the year, fleas on new patients visiting our hospital seems to be an everyday occurrence at the Animal Clinic at Thorndale. One of our primary teaching responsibilities is to help pet owners learn how to practice good flea control.

Successful flea control has two aspects. Fleas must be controlled on your cat, and fleas must be controlled in your cat’s environment. Since cats and dogs share the same fleas, the presence of a dog in your cat’s environment makes flea control much more difficult. Fleas can be identified as specifically dog or cat fleas, but they do cross over and bite the other species.

Diagnosis of Flea Infestation

When a cat is heavily infested with fleas, it is easy to find them. If the numbers are small, it is best to quickly turn your cat over and look on its belly. If you do not find them 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. When the numbers are very small, 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. If you use a fine toothed flea comb over the cat’s hind end, you can often capture fleas or retrieve flea dirt.

Flea dirt looks like pepper. It varies from tiny black dots to tubular structures about 1/32″ (1/2 mm) long. If you are in doubt of its identification, put the suspected material on a light colored paper 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 solution. Another trick is to put some of the material on a white paper towel and then dampen 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 cat’s bedding or where the cat 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.

The Flea’s Life Cycle

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 too small to see without magnification. Fleas lay their eggs on the cat, but the eggs do not stick to the cat’s hair. Instead, they fall off into the cat’s environment. The eggs make up 50% of the flea population. They hatch into larvae in 1 to 10 days, depending on temperature and humidity. High humidity and temperature favor rapid hatching.

Flea larvae are slender and about 1/8 – 1/4″ (2 to 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 a pupae. Moisture is essential for their survival; flea larvae are killed by drying. Therefore, it is unlikely that they survive outdoors in shade-free areas. 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 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 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 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 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 to 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 (adult flea –> egg –> larvae –> pupa –> adult) can be completed in 14-21 days with the proper temperature and humidity conditions or be prolonged in the pupa stage. 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 cat having an insufficient number of red blood cells, which is known as anemia. In young or debilitated cats, the anemia may be severe enough to cause death.

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

Flea Control

Successful flea control must rid the cat of fleas and it must rid the cat’s environment of fleas. In fact, environmental control is as important as treatment of the cat. If your cat remains 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 new topical products (see below). However, the cat that goes outdoors or stays outdoors presents a somewhat 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 cat. Also, these are primarily geared to kill adult fleas. Flea powders, sprays, and shampoos may kill the fleas present on your cat at the time of application. However, most of these products have little or no residual effects, so the fleas that return to your cat from his environment are not affected. Fleas also have developed resistance to some of these products.Thus, your cat may be covered with fleas within a day after having a flea bath or being sprayed or powdered. The toxicity of these products to your cat are generally higher than spot on products such as Frontline Plus.

Flea sprays and spot on products containing insect growth regulators are helpful in managing the overall problem because they help to break the flea life cycle. Always read the label when first using any new product on a cat. Never use a product on a cat that is only labeled for use on dogs. Fatalities have resulted. It is also not advisable to use flea products restricted to dogs on your dogs if your cats are in close contact with your canin companions.

Topical Products

There is a host of topical “spot-on” products available on the market. Read the directions and ingredient list very carefully. Keep in mind that pyrethrin and permethrin products have added toxicity and may not be effective. Topical treatments are applied to the nape of the neck. We recommend Frontline Plus/Gold and Revolution. Frontline Plus is not absorbed into your cat’s body. Revolution is absorbed but gives protection against certain other parasites as well.

As fleas evolve, so do the products available to knock them down and kill them. A product that was very effective 10 years ago, may have limited effectiveness today.

Flea Product Safety

Also, be very, very careful to never, never use on a cat a flea product labelled only for use on dogs. Toxicities and even deaths of cats have been caused by well meaning owners. Some “dog safe” labelled products have even made cats very ill who groom the dog, or sleep next to the dog. We recommend that when there are cats in the house, the only flea products that are used are those labelled safe for all your pets. Look to see that cats and dogs are specifically listed on the label.

Environmental Control

Environmental flea control must be directed at your house and your yard.

House. Even though fleas may be in your house, most people 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. (There are exceptions to this.) A professional exterminator may be called to treat your house or you may use a a long-lasting spray. These sprays are very effective for adult fleas, but they will not kill adults that are still in their cocoon. You should purchase 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. Foggers have the disadvantage that you have no control over the product and must abandon the house and clean surfaces thoroughly before use. Sprays can be directed where needed and can be used in one room at a time.

There are companies that will treat your carpet with a flea-killing powder. The powder is non-toxic 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. However, the self application kits do not offer a guarantee.

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 during the warm months of the year. You should use a 30-day residual product each time. Your veterinarian is able to help you choose the most effective product for your situation. Be especially aware of environmental toxicity of all outside products. Be aware of run off of water and how area birds and fish may be aversely affected.

Re-emergence 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 cat 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 and have not been brought home with the pet.