CHAPTER 15 BITING AND STINGING INSECTS 245
Hymenoptera
Sarcoptic/notoedric mange
Cheyletiellosis
Bacterial folliculitis
Demodicosis
Pemphigus foliaceus
DIAGNOSTICS
Flea Bite Dermatitis and Hypersensitivity
Biopsy: superficial, perivascular to diffuse inflammation with eosinophils and mast
cells; eosinophilic intraepidermal microabscesses.
Allergy testing; intradermal testing more reliable than serum testing for FBH: large
number of FBH dogs are positive to flea antigen; positives may also be seen in normal
patients: not reliable, especially if negative.Elimination of other causes of pruritus.
Fecal identification ofDipylidium caninumsegments.
Response to adequate flea control.
Spider Bite Dermatitis
Biopsy: epidermal and dermal necrosis with inflammation extending into the subcu-
taneous tissue; vasculopathy and mixed inflammatory infiltrate.
Visualization of puncture marks.
History of exposure to arachnids.
Fly Dermatitis
Biopsy: hyperkeratosis with erosions and serocellular crusting; dermal fibrosis, often
with interstitial and perivascular plasma cell and eosinophil infiltrate.
Elimination of other causes of lesions.
Response to appropriate fly control.
Mosquito Bite Dermatitis and Hypersensitivity
Biopsy: severe, eosinophil-rich superficial and deep dermal infiltrate; foci of
eosinophil degranulation with flame figures and eosinophilic mural folliculitis.
Allergy testing (intradermal and/or serum) positive to culicoides antigen: not reliable,
especially if negative.
Response to application of insect repellants or being placed in a mosquito-free
environment.