Canine Demodicosis Current Therapeutic Trends

Despite the advent of newer demodicidal therapeutics, management of the chronic relapsing or refractory demodicosis cases remains a frustration. Conservative therapy continues to represent the preferred approach to localized demodicosis in the juvenile. Benzoyl peroxide gel or cream is often selected as an initial choice. Application is performed daily for 30 days then reassessed. Total body acaricidal therapy is not warranted or recommended for the localized form in most cases. Providing adequate opportunity for spontaneous remission should be encouraged. Use of benzoyl peroxide shampoos is recommended. The majority of localized cases will self limit, while others may progress to a generalized form.

Treatment of the generalized case often necessitates total body demodicidal therapy, although spontaneous recovery is observed. This is more likely in young dogs with multifocal lesions than those with diffuse generalized areas of involvement. Initiation of systemic or generalized demodicidal therapy is accompanied by the recommendation for neutering since spontaneous remission cannot be evaluated. Treatment options are influenced by previous therapy and response.

The mechanism of this disease occurs as a cosequence of immunological deficiency primarily affecting T-Lymphocyte activity allowing for the proliferation of Demodex canis. There are different manifestations of the disease depending upon the extent of involvement (localized vs. generalized) and whether accompanied by complication of bacterial infection.

Localized Demodicosis

Localized demodicosis is relatively common in young dogs and has a high tendency of spontaneous resolution. The face and forelimbs are most frequently involved and often accompanied by hyperpigmentation or comedone formation. Stress factors may potentiate the problem. Dogs between 3 and 6 months are most represented in this group. Lesions may be variable but limited to multifocal circumscribed areas of alopecia, erythema and scaling. Conservative therapy may be considered including the use of benzoyl peroxide gel or topical acaricidal ointment (Goodwinol Ointment ^(R) ) daily. Abstinence of systemic or generalized total body topical therapy allows the identification of those cases that will progress to generalized pattern. This distinction becomes important when consideration of the genetic potential for propagation of the disease if breeding were to be considered.

Generalized Demodicosis

The progression of localized demodicosis is less likely since the vast majority of localized cases will resolve with or without therapy. Generalized case usually occur between 3-18 months although adult onset generalized demodicosis is observed. Lesions may be multifocal but are more commonly regionalized or generalized. Again the distribution includes the face, forelimbs, feet, or generalized over a large percentage of the body. This form is accompanied by secondary pyoderma further complicating the condition. In addition to the typical alopecia, erythema, scaling and hyperpigmentation, papules, pustules, furuncles, draining tracts and fistulous pedal lesions may be observed. Pruitus may be observed in these cases and inappropriate steroid therapy may have been used prior to the diagnosis. Demodectic pododermatitis with secondary infection may be associated with discomfort and represents a problem that may take protracted time to resolve. Diagnosis is made by deep skin scraping with the identification of the mite population. Occasionally the diagnosis is made through skin biopsy in breeds with unusually thick skin (e.g. Shar Pei).