Page 1478 - Clinical Small Animal Internal Medicine

1416 Section 12 Skin and Ear Diseases

common hypersensitivity in dogs and cats in flea‐
VetBooks.ir endemic areas. Fleas can be a perennial problem in sub-
tropical and tropical climate zones, seasonal in more
temperate climate zones, and practically nonexistent in
arid, high elevation, or cold climates. Even if fleas are
considered to be absent from a particular area, there is a
possibility that animal movement or contact may bring
fleas into the area.

Signalment
Any dog and cat in a flea‐endemic area can become aller-
gic to fleas but no breed or sex predilection has been
identified. Although FAD can develop at any age, dogs
predisposed to FAD will generally develop clinical signs
by 5 years of age.

History and Clinical Signs
The most typical clinical sign associated with fleas is
pruritus, but FAD must be differentiated from flea infes-
tation. Clinical signs associated with flea infestation are
variable. The pruritus is generally intermittent and an
increased number of fleas is common.
The typical predilection sites for FAD in dogs are the
lumbosacral area, tail base, and caudomedial thighs, and
minimal flea burden is typical. In cats, skin lesions are
commonly found on the caudodorsal area, as in dogs, but
can also be present on the head and neck. Many dogs and
cats suffering from FAD may have concurrent atopic der-
matitis and/or cutaneous adverse food reaction which
may complicate the clinical presentation and diagnosis. Figure 160.4 Five‐year‐old female spayed mixed‐breed dog with
The most common skin lesions seen in dogs with FAD flea allergy dermatitis exhibiting alopecia, erythema, excoriations,
and seborrhea along the caudodorsal aspects of the trunk, tail,
are erythematous papules and in more severe and and hindlegs.
chronic cases, self‐induced alopecia, lichenification, and
seborrhea on the predilection sites (Figure 160.4).
In cats, skin lesions range from miliary dermatitis
(crusted papules) to excoriations to self‐induced alope-
cia. Cats also often show skin lesions consistent with
eosinophilic granuloma, especially indolent ulcers on the
upper lips which can be found in up to 60% of flea‐aller-
gic cats (Figure 160.5).

Diagnosis
Any pruritic skin disease should be considered as a
potential differential diagnosis for FAD and mainly
includes other ectoparasitic disorders, microbial skin
infections, or other hypersensitivities. Diagnosis is based
on history, clinical signs, and response to therapy. The
presence of fleas is not an adequate indicator of FAD and
allergy skin testing with flea allergen can show false‐
negative results. Nevertheless, flea combing should be Figure 160.5 An indolent ulcer in a 4‐year‐old female spayed
performed for direct identification of fleas or flea feces. domestic shorthair cat with flea allergy dermatitis.