The Fleas are here!

By Carol S. Foil, DVM, MS, Diplomate A.C.V.D. Board-certified specialist through the American College of Veterinary Dermatology

Fleas are the most common external parasite of companion animals. Flea allergy dermatitis is the most common skin disease of dogs and cats! Flea control has always been a challenge for veterinarians and pet owners because the adult fleas cause the clinical signs, yet the majority of the flea population (eggs, larvae and pupae) are to be found off the pet in and around the home. The deal flea control program utilizes products that target the various stages of the flea life cycle, not only the adult fleas on the pet. In order to help you to select the most appropriate products to achieve a flea-free existence for an allergic pet, we will start by telling you about the life cycle of the flea.

The Life Cycle of the Flea: Ctenocephalides felis

Eggs are laid in the hair coat and are designed to fall off the host. They are resistant to insecticides, but susceptible to various insect growth regulators. Larvae develop in the host’s environment and feed on adult flea feces (blood) that fall out of the hair coat of the pet. Larvae are susceptible to traditional insecticides, borates and insect growth regulators. Larvae eventually spin cocoons (often within carpet fibers) for pupation. Pupae are resistant to freezing, desiccation, and insecticides. Pupae can lie dormant for many months; they are stimulated to expupate as emergent adults by vibration, warming and increased carbon dioxide. Normally, expupation occurs when a host is near and the new flea finds the pet within seconds of emergence. Emergent fleas are fairly mobile and can survive a few days without a host, if in a suitable environment. New fleas begin feeding within hours of finding a dog or cat. Once a blood meal has been taken, the flea can survive only a short time if it is dislodged from the host. New fleas experience very high mortality on healthy adult hosts. Most fleas do not survive 72 hours on an animal that is itching and able to groom itself.

Unfortunately, limited egg production does occur even on allergic animals. The entire life cycle of C. felis can be completed in as few as 16 days!

Flea Control Recommendations

For the flea allergic patient, continuous excellent flea control is required to remain symptom free. Even very minimal exposure may be sufficient to perpetuate itching in a hypersensitive patient. In the past, veterinarians and pet owners always had to try to control fleas by treating the environment of the animal for the immature stages of the flea. This approach, although effective when properly instituted, is labor intensive and requires frequent repetitive applications. Also, some of the older products made for killing fleas on our pets do not kill fleas instantly or are not long lasting enough to really help flea allergy patients, because the female fleas survived long enough to lay a few eggs and perpetuate the life cycle.

Today’s Flea Control Products

Today, veterinarians have some great flea control products in our arsenal. There are now several highly efficacious, long lasting and very safe new products to choose amongst.

Program® and Sentinel® (Lufenuron) from Novartis

These prescription drugs are available as a once a month flavored chewable (soy and pork) pill or oral liquid suspension to be given with a full meal. Female fleas that feed on pets treated with lufenuron produce sterile eggs. The product does not kill adult fleas. It is a very easy way to break the life cycle but pets remain fully susceptible to the emergence of any fleas from pupa already present in the environment. Therefore, 4 to 7 months may pass before the flea free state is reached. In order to stop the life cycle, every animal in the patient’s environment must receive lufenuron or another insect growth regulator. Pets should be treated for fleas with an adult flea-killing product during the first few weeks of starting Program®.

Advantage® (imidacloprid), K9 Advantix® (with permethrin), Advantage Multi® (with moxidectin) from Bayer

These products are available as a spot ons for either dogs or cats. Advantage Multi® is a prescription drug that also is a heartworm preventive. Advantage® seems to be very well tolerated by sensitive cats. It provides flea knockdown in about 8 hours. 100% killing can be maintained for at least two weeks. It is susceptible to wash off, therefore outdoor active dogs and dogs that swim or that must be bathed because of dermatitis must be re treated frequently. (Weekly re treatment is allowed with Advantage only®). Imidacloprid has no efficacy against ticks, but K–9Advantix®, with permethrin does. K9 Advantix is only labeled for once a month, and ONLY FOR DOGS.

Frontline® Spray, Frontline Plus® and Frontline Top Spot® (fipronil) from Merial

Fipronil is a broad spectrum insecticide available as a spray or a drip-on. Fipronil binds chemically to the hair and is absorbed through the hair follicle by the sebaceous glands. In spray formulation fipronil may kill fleas at 95% for up to 30 days after application on dogs and stands up to biweekly bathing. It is labeled for puppies and kittens of 8 weeks (10 weeks for Top Spot®). It is also affective against ticks. The major problem with the spray is the high volume of alcohol based product that must be applied. Many cats will show minor adverse reactions with this application technique. The product is labeled to be applied no more than once a month. Frontline Plus® contains the insect growth regulator, S-methoprene and so provides control of eggs and adult fleas.

Revolution® (selamectin) from Pfizer

This prescription drug is designed as a once-a-month heartworm preventive and flea preventive for dogs and cats as young as 6 weeks old. It also kills adult fleas and can be used to treat sarcoptic mange, ear mites and ticks. It also helps control roundworms and hookworms in cats. The product is placed on the skin at the back of the neck, but is absorbed into the body to have its effect when female fleas ingest it with a blood meal. Adult fleas will die slowly, but more importantly, female fleas stop egg production as soon as they are exposed. It is most useful as a preventive for flea infestation and in the presence of a flea problem in an allergic pet, but it is an excellent flea control product for cats.

Capstar® (nitenpyram) from Novartis

This is a prescription tablet for dogs and cats as young as 4 weeks of age. It offers extremely rapid and complete killing of adult fleas on the pets after administration. It is safe enough that the tablets may be used as needed, as often as once per day, whenever you see fleas on your pet. This is designed to be used in combination with an insect growth regulator to knock out fleas when these slower products are being used for long-term control. It can also be used when the pet has visited a flea-infested environment for rapid protection. When given every-other-day, it is a useful flea control for single cat households.

Comfortis ®for Dogs (spinosad) from Elanco Animal Health Division of Eli Lilly

This monthly prescription tablet for fleas represents a completely new class of drugs in flea control. It is available for use on puppies and dogs 14 weeks of age or older and is available in 5 different sized flavored (soy and pork) chewable tablets. It is meant to be used once a month and preliminary results show it will be very useful for flea allergic pets as it has a rapid kill rate.

About Traditional Insecticides / Over-the-Counter Flea Control Products

Several adulticide insecticides or shampoos are available and some have insect growth regulators such as s-methoprene included. Shampoos are less effective than sprays, dips or spot ons because they have little residual activity. For cats, pyrethrins as sprays or foaming mousses may useful for safe, quick knock-down of fleas. For dogs, permethrin sprays or spot-on products with methoprene or Nylar may be effective, but cats MUST NOT BE EXPOSED directly or indirectly to permethrin products. There is some resistance in fleas to permethrin products now documented. Over-the-counter products with etofenprox and S-methoprene can be used with some caution in cats and may be effective in some settings but are not fast enough for good results in flea allergy.

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