Treatment of AMD should begin with clipping the hair of the affected area, taking care to prevent further trauma to the skin.2-4 Clipping should be performed beyond the visibly affected margin, as lesions often extend into the haired skin and can be difficult to visualize. Once the area is clipped, the area around the primary lesion should be examined to locate satellite lesions. Folliculitis or furunculosis is likely when satellite lesions are present and may necessitate the need for systemic antibiotics.1,3 The affected area should then be cleaned with a topical biocidal solution (eg, 2% chlorhexidine solution).3,7 If lesions are infected based on cytologic findings, topical treatment (eg, 2% chlorhexidine solution, antimicrobial spray or mousse containing chlorhexidine or ethyl lactate) should be used twice daily until lesions resolve. Medicated shampoos can be used alone if clipping the hair is not possible, although treatment failure may result. Systemic antibiotics are indicated if topical therapy does not resolve the infection or if areas are difficult to treat topically (eg, when infection extends into skin covered in dense hair).3,8 As with generalized pyoderma, empiric therapy should be based on typical susceptibility patterns of S pseudintermedius6; amoxicillin or penicillins should be avoided due to the prevalence of β-lactamase–mediated acquired resistance to these antibiotics found in S pseudintermedius isolates.1,9 Cephalexin (22-30 mg/kg q12h) is favored instead. Cefpodoxime (5-10 mg/kg q24h), a third-generation cephalosporin, has a similar spectrum of activity against Staphylococcus spp as compared with cephalexin and is often used in smaller animals to enable appropriate administration. Clindamycin can also be used empirically; however, resistance to this antimicrobial may occur.8 Antibiotics should be prescribed for an appropriate length of time, just as with other presentations of folliculitis or furunculosis. The standard course of therapy is typically 3 to 4 weeks (continued 1 week past clinical resolution) for superficial infections and 6 to 8 weeks (continued 2 weeks past clinical resolution) for deeper lesions.8
Antipruritic medications and, for some patients, an Elizabethan collar are also indicated, as self-trauma is key in lesion creation and perpetuation. A short course (ie, 3 days to 2 weeks) of anti-inflammatory prednisone or prednisolone (0.5-1.1 mg/kg) is recommended because fleabite hypersensitivity is often present and typically steroid responsive. Antimicrobial medications should be continued beyond discontinuation of steroids, as steroids can decrease lesion inflammation and obfuscate whether infection is truly resolved.6,10 Continuing antimicrobial medication until the skin has completely normalized (for topical medications) or is past clinical resolution (for systemic antibiotics) should help prevent relapse and recurrence. Other antipruritic options include labeled doses of oclacitinib and injectable caninized IL-31 monoclonal antibody. It is the authors’ opinion that potent topical steroids (eg, betamethasone, isoflupredone, triamcinolone) with or without topical antibiotics (eg, gentamicin, neomycin) should be avoided when treating AMD. Topical steroids may enhance bacterial growth or decrease localized antimicrobial defenses; often contain alcohol when formulated as a solution, which stings when applied to ulcerative lesions; and can counteract the patient’s local healing and immune responses, which can delay healing and perpetuate and exacerbate localized alopecia.2,11 In addition, the potential adverse effects of topical steroids—including iatrogenic Cushing’s disease, skin fragility, focal or generalized alopecia, and calcinosis cutis12—may not be fully understood by pet owners, which can lead to frequent and indiscriminate use of these products, further complicate cases, and prolong patient morbidity.
Prevention of AMD recurrence requires identifying and addressing the underlying cause. Because fleabite hypersensitivity is commonly associated with AMD, clinicians should ensure all pets in the household are receiving a consistent, high-quality flea preventive. Patients with AMD on the lateral face should be assessed for otitis externa.2 Once a patient is diagnosed with AMD, a recheck examination should be performed 3 to 4 weeks after the initial visit, thus helping to ensure clinical resolution and determination of when antimicrobial therapy can be discontinued.