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 ideal 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 100% flea control is required to
remain symptom-free. Even very minimal exposure may be
sufficient to perpetuate itching in a hypersensitive patient
(one or 2 bites per week are enough!). Until very recently,
veterinarians and pet owners have had 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. Application of adulticides on the animal has
merely been of palliative value. The safe insecticides
previously available to us did not kill fleas instantly or were
not long-lasting enough to ensure adequate protection from flea
bites. The female flea survived long enough to lay a few eggs
and perpetuate the life cycle.
Today’s Flea Control Products
Recently, some new products have been added to our flea control
arsenal. These appear to be highly efficacious, long lasting and
have a very low potential of harmful side effects. It may well
be that these promising products will revolutionize flea control
in the United States.
Program® And Sentinel® (Lufenuron) from Novartis This is
available as a once a month pill or oral liquid suspension to be
given with a full meal. These are prescription drugs. Adult
fleas that feed on animals 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. Pets should be sprayed for fleas with an adulticide
during the first few weeks of starting Program®.
Nylar® (Pyriproxifen)
This is a new insect growth regulator that is extremely
effective against flea eggs. It remains 100% effective for 150
days after a single spray application! It is an excellent option
in cases when Program® may be too expensive because of a
multiple pet household or in situations where Program® is
ineffective. It is presently available as a spray-on and as a
drip-on in combination with permethrin for dogs and a spray with
pyrethrins for cats and also as Nylar flea control collars for
dogs and cats. Environmental foggers and sprays are also being
marketed.
Traditional Insecticides
Several adulticides insecticides or shampoos can be used along
with Program® or Nylar®. Shampoos are considered inferior to
sprays, dips or drip-ons because they have little to no residual
activity. For cats, pyrethrins as sprays or foaming mousses are
useful. Examples include Mycodex Fast Act® and Fast Act 2®
(these products have a reduced level of alcohol which is much
more easily tolerated by cats). For dogs, permethrin sprays are
recommended. Over-the-counter Hartz Mt®. produces with
phenothrin can be used with some caution in cats.
Advantage® (Imidacloprid) from Bayer
This is marketed as a drip-on for both dogs and cats. Advantage®
seems to be very well-tolerated by sensitive cats. It provides
flea knockdown in 24 hours. For cats, 100% killing can be
maintained for 21 days; for dogs 90% for 28 days. It is
susceptible to wash off, therefore outdoor active dogs and dogs
that swim or must be bathed because of dermatitis must be
re-treated frequently. (Weekly re-treatment is allowed.)
Imidacloprid has no efficacy against ticks, but K-9Advantix®,
with permethrin does. K9 Advantix is only labeled for once a
month, and is 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 kills fleas at 95% for over 80 days after
application on dogs and for 1 month with biweekly bathing. It is
labeled for puppies and kittens of 8 weeks (10 weeks for Top
Spot®) and the product is not washed off by bathing. 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 must 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 product 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, any eggs laid prior to death
will never develop. It is most useful as a preventive for flea
infestation and in the presence of a flea problem in an allergic
pet, other insecticide treatment will be recommended at first.
It is a prescription drug.
Capstar® (Nitenpyram) from Novartis
This is a an oral 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.
The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.
