Flea Control in Flea Allergy Dermatitis

Chapter 97


Flea Control in Flea Allergy Dermatitis




Flea infestations within a home or outdoor environment can be a constant or recurring problem for humans and their pets. Although many pets experience flea bite dermatitis, some also may develop flea allergy dermatitis. The most common flea found in North America is the cat flea, Ctenocephalides felis felis, which affects dogs and cats as well as nondomestic wildlife such as opossums, raccoons, skunks, foxes, and coyotes. Wildlife can be a problematic continual reservoir of fleas for domestic pets that may be challenging to eliminate or control. The purpose of this chapter is to provide guidance for the practitioner regarding the important factors to consider when designing a flea-control strategy for a patient.



Flea Biology


The adult flea spends its entire life on the dog or cat host, with the female laying up to 50 eggs per day and potentially several thousand eggs over a lifetime. Eggs are shed into the environment when laid on the host and hatch in 1 to 10 days into larvae, which move deep into carpet fibers or soil. Larvae are susceptible to desiccation at low humidity and extreme temperatures and survive outdoors only in shady moist areas protected from sunlight or heavy rain. Carpeted areas within the home can provide optimum conditions for larval survival. Larvae molt twice before spinning a cocoon that is impervious to chemicals or environmental hazards. Within the cocoon, the larva pupates and becomes a preemergent adult until a suitable host is present. Pupae can remain dormant for several months; however, in ideal conditions, the flea life cycle can be completed in about 2 to 3 weeks. Adult fleas feed within minutes of finding a host, may mate within 8 hours, and can begin egg production within 24 hours of acquiring a host.



Flea Allergy Dermatitis


A variety of flea salivary proteins have been identified that elicit positive intradermal skin test results and elevated immunoglobulin E antibody responses detectable on enzyme-linked immunosorbent assay. In dogs, the disease is characterized by pruritus and a papular dermatitis affecting the caudodorsal trunk, tail base, perineum, caudomedial thighs, flanks, or ventral abdomen. Pyotraumatic dermatitis (“hot spots”) on the rump is a feature in some affected dogs, as is a secondary staphylococcal pyoderma or yeast (Malassezia) dermatitis. In cats, a similar regional localization of pruritus and lesions may occur. However, cats additionally may have lesions and pruritus in other body locations including the head, neck, and trunk, and this may manifest as miliary dermatitis. Further, some flea-allergic cats have eosinophilic granuloma complex lesions such as indolent ulcers of the upper lip, eosinophilic plaques of the ventral abdomen, and eosinophilic granulomas. Thus the clinical signs are significantly more varied and less distinctive in the cat than in the dog. For both dogs and cats, a diagnosis of flea allergy dermatitis (FAD) is confirmed upon resolution of clinical signs following institution of an aggressive flea-control therapeutic trial.



Flea-Control Strategies



General Points


The term flea control may be interpreted in several ways by pet owners. Clients may be content with seeing just a few fleas on their pet, which may be adequate for pets without FAD. However, for pets with FAD, reduction of flea exposure to zero is the goal whenever possible, and this must be communicated clearly to the client. Achieving this goal may require frequent application of possibly more than one product to the affected pet, at least initially. Routine flea control for all pets should be implemented continuously throughout the year in households with a flea-allergic pet.


Clients often buy over-the-counter (OTC) products that may look similar to prescription products and have names that sound familiar. Unfortunately, many OTC products have active ingredients whose properties are not as favorable, nor are they are as effective as the prescription products. Furthermore, even when products are purchased OTC that previously were prescription products, owners are unlikely to obtain professional advice and expertise regarding proper dosing, dosing intervals, treatment of other pets, and management of the environment, which puts them at risk of failed flea control and apparent flea resistance.



Factors That Influence the Strategy


Flea eradication is essential for those pets exhibiting FAD; the goal must be zero flea exposure, at least for the initial 4 to 8 weeks of the flea-control therapeutic trial. This can be challenging considering the variety of environments in which pets reside, which necessitates customized flea-eradication plans for each household; that is, strategy will vary significantly depending on the specific circumstances. The following factors should be considered:



• Speed of flea kill: The more rapidly fleas are killed, the less they feed and the less salivary allergens are injected to continue the allergic reaction. Although most products kill fleas fairly rapidly when first applied, this effect may be diminished significantly 3 or 4 weeks later, so residual speed of kill also is important. This is why many dermatologists will apply spot-on formulations every 2 weeks during the flea-control therapeutic trial to ensure maximal residual speed of kill.


• Compliance: There may be large differences in owner compliance with regimens requiring a daily tablet, a monthly spot-on formulation, and a 6- to 8-month collar.


• Spectrum of activity: Treatment may be directed solely at flea control or there may be a need for tick control, heartworm prevention, or activity against other parasites (such as mites, lice, or mosquitoes).


• Route of administration: Some owners prefer oral medications over topicals, whereas some dogs or cats tolerate topicals better than oral medication.


• Product characteristics: Consideration of whether frequent bathing or wetting is likely to occur may favor oral or systemic agents. If the patient is undergoing a food trial for a possible adverse food reaction at the same time, the use of many oral medications (including some flea-control products and heartworm preventives) is precluded because of the presence of flavorings in the medications that may negate the food trial. Some owners find the odor of topical spot-on formulations unacceptable and thus prefer oral medication.


• Pet’s environment and all possible sources of flea exposure: Wildlife, neighboring animals, and feral cats are major sources of exposure to fleas.


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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Flea Control in Flea Allergy Dermatitis

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