most of the world, flea infestation is the most common ectoparasitic condition
of dogs and cats. Flea allergy dermatitis is the most common small
animal dermatologic disease.
Efforts to control fleas have advanced in recent years because of the availability
of topically applied flea control products and have dramatically altered
attaining the goal of flea eradication.
development of effective topical and systemic flea control products has
decreased the necessity of treating the environment. Environmental
flea control may still be necessary at the onset of flea control when a
heavy flea burden exists or when a multiple pet household is treated or
when flea allergy dermatitis exists in pets or ownersand rapid eradication
of fleas is essential. The treatment of choice for the environment
is a residual insect growth regulator (methoprene, pyriproxifen) or other
larvicide in combination with an adulticide.
Knowledge of flea biology is necessary in order to determine the class
of flea control necessary for the individual pet and/or the environment.
The cat flea, Ctenocephalides felis felis, is most common flea
infesting dogs, cats, pet rabbits, guinea pigs and ferrets in United States.
The cat flea has a variable length of developmental cycle depending on
temperature and humidity. Under conditions of 75 F and 78%
relative humidity, the developmental cycle varies from 17 to 26 days depending
on the insect’s gender. Dryness, high heat and extreme cold will
prolong the life cycle and may be deleterious to larvae.
Flea eggs are laid on the host within 24-36 hours after flea’s
first blood meal. Approximately seventy percent of eggs fall from
haircoat within eight hours and are distributed in the any portion of
the environment to which the pet gains access. Flea larvae
are susceptible to heat and dessication. Flea pupae are resistant
to dessication. Adult fleas commence feeding and mating within the
first twenty-four hours. The cat flea is a permanent ectoparasite,
which means that once on the host, the flea is removed only by grooming
FLEA ALLERGY DERMATITIS (FAD)
Flea saliva contains a histamine-like compound, enzymes that have cytolytic,
anticoagulant, and proteolytic properties, and complete protein antigens
of 14-90 kilodaltons. Flea allergy dermatitis is characterized as
Type I, Type IV, late phase (IgE), and cutaneous basophil hypersensitivity.
The immunologic mechanism of flea allergy dermatitis that develops in
a specific animal is contingent upon the length and degree of exposure
to fleas and genetic predisposition. Animals with atopic dermatitis
are predisposed to development of flea hypersensitivity.
is no breed or sex predilection for flea allergy dermatitis. The
development of flea allergy dermatitis may occur at any age. The
disease initally may be seasonal. Flea allergy dermatitis may occur
year-round contingent on the environmental parameters conducive to flea
The lesions of flea allergy dermatis are multiple and consist of licking,
chewing, excessive grooming, especially involving the rear half of the
body, dorsal lumbosacral area and groin. Fibropruritic nodules are
uncommon lesions seen in dogs with chronic flea allergy dermatitis.
The lesions are usually located in the dorsal lumbosacral region of dogs
and are firm alopecic nodules of 0.5 to 2 cm in diameter.
Commonly noted signs of flea allergy dermatitis in cats include symmetric
alopecia (self induced) and miliary dermatitis (generalized or “collar”
pattern). Feline eosinophilic disease associated with flea allergy
dermatitis include eosinophilic plaques, indolent ulcers, and eosinophilic
granulomas. A peripheral eosinophilia has been documented in approximately
20% of cats diagnosed with flea allergy dermatitis.
Diagnosis and treatment of secondary pyoderma in dogs with flea allergy
dermatitis is an important component of therapy. Dogs with flea
allergy dermatitis may have accompanying lesions of pyotraumatic dermatitis,
superficial pyoderma, or deep pyoderma.(Figure 3) The lesions of
deep pyoderma with accompanying cellulitis seen in German Shepherd Dog
pyoderma are commonly associated with flea allergy dermatitis.
and fatty acid therapy is rarely effective in dogs and cats with flea
allergy dermatitis. Fatty acid therapy has been proposed for the
treatment of cats with flea-induced miliary dermatitis.
Immunodiagnostic tests available for diagnosis of flea allergy include
intradermal skin testing with total flea extract (1:1000 wt/vol).
An immediate reaction (20 minutes) will be observed in 80% of patients
with flea allergy dermatitis; 20% of patients will exhibit a delayed reaction
(48-72 hours). Serum in vitro testing has variable accuracy
in the diagnosis of flea allergy dermatitis. Multiple hyposensitization
studies have shown no significant benefit for therapy of canine or feline
flea allergy dermatitis.4-6
There are several important concepts to consider for effective flea control.
The most important concept is complete flea eradication. Treatment
of all “in contact” animals and possibly environment may be necessary.
It is important to focus on “source points” which are areas of most preferential
flea development. Individualized “personalized” protocols are the
most effective form of flea management.
The ideal treatment is safe, non-toxic, non-irritating, immediate effect,
repellant effect, long duration of action, and activity against multiple
stages of the flea cycle
FLEA CONTROL PRODUCTS
convenience of use, residual activity, activity on flea cycle (inhibitors
of chitin synthesis (lufenuron, cyromazine, diflubenzuron), repellent
activity (fenthion=Pro-Spot )
incomplete efficacy for flea allergic animals, limited efficacy on male
fleas (cythioate=Proban ) due to insufficient absorption during blood
ENVIRONMENTAL PUMP SPRAYS
good dispersion of products, focal treatment of source points
expensive cost, cumbersome application
ingredients: pyrethroids, organophosphates, insect growth regulators
convenience of use
expensive cost, insufficient concentration at source points, poor dispersion
around corners and under furniture
of action: toxic effect on flea larvae by ingestion (Dryden, unpublished
data, 1993), blockage of flea digestive tract?, abrasion of cuticle and
possible use of inert, non-insecticide compounds (e.g. sodium polyborate)
cumbersome application, poor aesthetic effect, variable expense, efficacy
decreased in presence of water-cannot shampoo carpets
of action: entomopholic nematode (Steinernema carpocapsae) larvae
is parasite of insect larvae (including flea larvae) and infested with
pathogenic bacteria; nematodes penetrate the insect cuticle and release
the pathogenic bacteria
non insecticide agents, specific, active, targeting of the flea larvae,
absence of mammalian toxicity
limited to outdoor use, destruction of some saprophyte insect larvae,
will not colonize, requires monthly application, outdoor use only, 20%
soil moisture requirement, cost?
IMIDACLOPRID (ADVANTAGE )
Imidacloprid is a nitroguanidine compound that binds to postsynaptic
portion on nicotinic receptors preventing impulse transmission.
Advantage® is available as a 9.1% solution for dogs and cats.
Advantage® is applied as a spot treatment every 28 days; more optimal
response (flea allergic animals) requires therapy every 21 days and in
some cats every 14 days. Ease of application greatly enhances owner
compliance. Manufacturer literature shows no evidence of toxicity
in animals receiving exaggerated dosages. There is concern for breakdown
after bathing or water exposure, therefore, limit shampooing and swimming
between applications or reapply.
FIPRONIL (FRONTLINE )
Fipronil is a phenylpyrazole compound that disrupts CNS activity by interference
with chloride ion passage through GABA-regulated chloride channels of
invertebrates; selective neurotoxicity for insects. Frontline®
is available in spray and spot-on formulations, is acaracidal and has
been labeled for ticks. There have been anecdotal reports of clinical
success for treatment of sarcoptic acariasis with aggressive application
once every 2 weeks for 3 treatments. There have also been reports
of improvement in treatment of Otodectes (ear mites). Use
of Frontline® for sarcoptic acariasis and Otodectes is extralabel
Frontline® has an affinity for sebaceous secretions. The chemical
is found in hair follicles and sebaceous glands and is redistributed to
skin surface for residual activity. Studies using Frontline spray
monthly with weekly benzoyl peroxide, anti- seborrheic or emollient shampoos
demonstrate that a reduced residual efficacy may occur. To control
fleas in flea allergic cats, it may be necessary to reapply Frontline®
every 2-3 weeks. Frontline® should be used every 30 days to
control fleas on dogs. Multiple reports of toxicity with use in rabbits
indicate that Frontline Spray or Topspot usage is contraindicated.
Toxicity may be related to the vehicle.
LUFENURON (PROGRAM )
is a benzoylphenyl urea. Program ® is considered an extremely
safe flea medication with no mammalian toxicity since mammals do not produce
chitin There is no direct toxic effect on adult fleas and the time factor
to disrupt the flea life cycle is significant (60-90 days). The
adult flea must feed on animal to ingest; thereby inducing an allergic
reaction. There is a significant potential for reinfestation by
ova from untreated animals with access to environment. Injectable
lufenuron is available for cats and is administered subcutaneously once
every 6 months. Report of possible fibrosarcoma associated with
injectable form. Program® should be administered with a meal
or decreased absorption may be noted. Program® has limitations
as sole therapy in a flea allergic animal but may be used adjunctive therapy
or as a component of an integrated pest management program.
PERMETHRIN W/PYRIPROXIFEN (KNOCKOUT ) [DOGS ONLY!!]
Knockout® is a 2% permethrin (mechanism of action: activity on sodium
channels) and pyriproxifen (insect growth regulator) at 0.05% concentration.
Knockout® has efficacy against fleas and ticks as well as a repellent
effect. It is one of the lesser expensive new forms of canine flea
control. For enhanced efficacy in flea allergic dogs, use Knockout®
twice weekly for first month, then on a weekly basis. The product
is intended for usage in adult dogs only. Reapplication is necessary
after swimming or bathing. The alcohol base provides “knockdown”
effect to fleas.
The product is not intended for use in cats. The Knockout®
product is also available in an environmental spray and may be used outdoors
as pyriproxifen is not inactivated by sunlight.
SELAMECTIN (REVOLUTION )
Selamectin was released in September 1999. Selamectin (Revolution®),
an avermectin, kills fleas by inducing neuromuscular paralysis.
Revolution® is distributed into sebaceous glands. Revolution®
kills adult fleas and manufacturer literature reports prevention of eggs
from hatching. Revolution® is also labeled for treatment of
ear mites, sarcoptic acariasis, intestinal nematodes, and for use as a
heartworm preventative. A concern exists for efficacy with frequent
shampooing with sebum-stripping products, therefore, Revolution® may
need to be reapplied for optimal efficacy. Treatment is once monthly.
Revolution® has FDA labeling; Advantage and Frontline are EPA labeled.
RESISTANCE AND INTEGRATED PEST MANAGEMENT
Integrated pest management (IPM) has been recommended to decrease the
incidence of resistance to the newer flea control products. The
cat flea, of all of the species of fleas tested, is resistant to the greatest
number of categories of insecticides.
Dryden has shown that even with the newer insecticides (fipronil and
imidacloprid), insecticide selection pressure can produce resistant fleas.
The resistance concentration significantly reduces the residual efficacy
of the products.
A program has recently been initiated by the Bayer Corporation to monitor
the susceptibility of field flea populations to imidacloprid (Advantage®).
The program will develop susceptibility assays, identify flea strains
with reduced susceptibility, determine the mechanisms of reduced susceptibility,
and develop strategies to counter any decrease in efficacy. The
initiative involves international researchers in flea biology and control.