PEEP R RREREVEEVVIEWED DERMATOLOGY DETAILS Updates on the Management of Canine Demodicosis Sandra N. Koch, DVM, MS, DACVD University of Minnesota Canine demodicosis is a common inflammatory establish prognosis and provide a successful parasitic skin disease believed to be associated with treatment, it is very important to evaluate the: a genetic or immunologic disorder. This disease • Age of onset allows mites from the normal cutaneous biota to proliferate in the hair follicles and sebaceous • Extent and location of skin lesions glands, leading to alopecia, erythema, scaling, • Presence of secondary infections hair casting, pustules, furunculosis, and secondary • General health of the dog.1,3,5 infections.1-3 The face and forelegs to the entire 1-3 body surface of the dog may be affected. Independent of age, it is important to identify and treat any predisposing or contributing factors Three morphologically different types in order to achieve a successful outcome.1-3 of Demodex mites exist in dogs: 1. Demodex canis: The most common form of Demodex (Figure 1) 2. D cornei: A short-body form, likely a morphological variant of D canis4 (Figure 2, page 78) 3. D injai: A long-body form1-3 (Figure 3, page 78) Published studies indicate similar efficacy of treatment regardless of the type of mite.1,2 THERAPEUTIC APPROACH Effective treatment of generalized demodicosis requires a multimodal approach.1,2 In order to FIGURE 1. Demodex canis identified on skin scrapings. JANUARY/FEBRUARY 2017 TVPJOURNAL.COM 77 PEER REVIEWED AGE OF ONSET Adult-Onset Juvenile-Onset In dogs older than 18 months of age, demodicosis may occur as a result of immunosuppression due to Demodicosis may occur in dogs 18 months of age drugs (eg, glucocorticoids, ciclosporin, oclacitinib or younger as a result of an immunocompromised maleate, chemotherapy) or systemic disease (eg, state associated with endoparasitism, malnutrition, hyperadrenocorticism, hypothyroidism, neoplasia, or health debilitation. Puppies may also develop malnutrition, parasitism).1,3 Therefore, dogs with demodicosis due to an immature immune system adult-onset demodicosis should have a detailed or mite-specific immunoincompetency.1,3 The physical examination and full diagnostic workup increased prevalence in certain breeds indicates a (Table 1) performed to identify underlying diseases. hereditary basis for juvenile-onset demodicosis, particularly for the generalized form.3 Evidence has indicated that successful treatment of an underlying disease may contribute to remission of demodicosis.1,3 However, up to 56% of dogs with adult-onset canine demodicosis have been reported to have no detectable underlying disease.2 EXTENT & LOCATION OF LESIONS Localized Form1 • Four skin lesions or fewer • Lesion diameter ≤ 2.5 cm Prognosis for localized demodicosis is good, as most lesions resolve spontaneously within 6 to 8 weeks.1,3 Topical therapy with benzoyl peroxide shampoo or gel may be recommended.1,3 FIGURE 2. Short-bodied form: Demodex cornei. Generalized Form1 • More than 4 skin lesions • Lesion diameter > 2.5 cm (Figures 4 and 5) • And/or feet are affected TABLE 1 Demodicosis: Diagnostic Analysis Complete blood count Serum biochemical profile Urinalysis Heartworm and fecal tests Lymph node aspirates Thyroid and adrenal testing Abdominal ultrasound FIGURE 3. Long-bodied form: Demodex injai. Chest radiographs 78 DERMATOLOGY DETAILS PEER REVIEWED Overall prognosis for resolution of skin lesions is Relapses of generalized demodicosis are not uncommon.1 good (Figure 6), but prognosis depends on the Dogs may be euthanized as owners may be unable to patient’s health status and underlying conditions afford cost of therapy or commit to the necessary intense or presence of immunosuppression.1,3 management.1-3 In some patients with refractory or noncurable demodicosis, treatment may be lifelong.1,2 Spontaneous remission in a subset of young dogs has been reported to be 30% to 50%3; however, PRESENCE OF SECONDARY the true incidence of spontaneous resolution INFECTIONS of generalized demodicosis is unknown. Secondary bacterial and yeast skin and ear infections are common problems associated with canine demodicosis, which aggravate the skin disease and cause or contribute to pruritus.1,3 Identifying and treating these secondary infections is very important to the successful treatment of demodicosis.1,3 Topical and/or oral antibiotics may be prescribed according to clinical signs and cytology. Bacterial culture and susceptibility testing should be performed in patients that do not respond to antibiotic therapy or have a history of multiple antibiotic courses, in an attempt to identify and treat resistant bacteria. Most dogs benefit from weekly antimicrobial baths FIGURE 4. Generalized demodicosis. with benzoyl peroxide or chlorhexidine shampoos.1,3 MITICIDAL THERAPIES Multiple conventional and newer therapeutic options currently exist for generalized demodicosis (Table 2, page 80);1-3,6 however, most of these therapies are extralabel, can be difficult to administer, and may lead to adverse effects. Miticidal therapy may need to be adjusted according to the dog’s response and tolerance. FIGURE 6. Patient from Figures 4 and 5 after treatment FIGURE 5. Generalized demodicosis. for demodicosis. JANUARY/FEBRUARY 2017 TVPJOURNAL.COM 79 PEER REVIEWED TABLE 2 Canine Generalized Demodicosis: Acaricidal Treatment Options DRUG DOSAGE ADVERSE EFFECTS COMMENTS LABELED FOR CANINE DEMODICOSIS Amitraz 0.025%–0.06% Hyperglycemia, • Good evidence for use (Mitaban, topical rinses bradycardia, • Labeled at 0.125% Q 2 weeks zoetisus.com) weekly to depression, lethargy, • Dogs > 4 months of age every 2 weeks polydipsia, polyuria, • Avoid other sedating agents, such as GABA agonists vomiting, diarrhea, (eg, benzodiazepines), alpha-adrenergic agonists transitory pruritus, (eg, xylazine), and heterocyclic antidepressants (eg, sedation amitriptyline) EXTRALABEL USE FOR CANINE DEMODICOSIS IN THE U.S. Afoxolaner 1 tablet PO Q Vomiting, diarrhea, • Further studies needed to establish protocol, (Nexgard, 2–4 weeks lethargy, dry/flaky skin efficacy, and safety merial.us) • Dogs ≥ 8 weeks of age • Use with caution in dogs with history of seizures • Safety has not been evaluated in breeding, pregnant, or lactating dogs Doramectin 0.6 mg/kg PO Lethargy; neurologic • Some evidence for use (Dectomax, or SC weekly signs, such as tremors, • 0.3 mg/kg twice weekly may reduce adverse effects zoetisus.com; or twice mydriasis, ataxia, coma, • Do not use in herding breeds and their crosses or Doramec, weekly death dogs with confirmed ABCB1-1Delta (MDR-1) gene agrovetmarket.com) mutation Fluralaner 1 tablet PO Q Vomiting, diarrhea, • Further studies needed to establish protocol, (Bravecto, 12 weeks anorexia, flatulence, efficacy, and safety merck.com) lethargy • Dogs ≥ 6 months of age • Safe for use in breeding, pregnant, and lactating dogs • Safe for use in dogs with ABCB1-1Delta (MDR-1) gene mutation, such as collies Ivermectin 0.3–0.6 mg/kg Lethargy; vomiting; • Good evidence for use (Ivomec 1%, PO Q 24 H neurologic signs, such • Do not use in herding breeds and their crosses or merial.us; as tremors, mydriasis, dogs with confirmed ABCB1-1Delta (MDR-1) gene Ivermax 1%, ataxia, coma, death mutation aspenveterinary • Do not use concurrently with spinosad (Comfortis resources.com) and Trifexis, elanco.us) due to resulting severe neurologic adverse effects Milbemycin oxime 1–2 mg/kg PO Lethargy; vomiting; • Good evidence for use (Interceptor, Q 24 H neurologic signs, such • Use with caution in herding breeds and their crosses elanco.us) as tremors and ataxia or dogs with confirmed ABCB1-1Delta (MDR-1) gene mutation Moxidectin 0.2–0.5 mg/kg Lethargy; neurologic • Good evidence for use (Cydectin, PO Q 24 H signs, such as tremors, • Do not use in herding breeds and their crosses or bi-vetmedica.com) mydriasis, ataxia, dogs with confirmed ABCB1-1Delta (MDR-1) gene lethargy, coma, death mutation Moxidectin + 1 tube/dog Local cutaneous • Good evidence for use Imidacloprid topical spot-on inflammation or • Dogs ≥ 7 weeks of age (Advantage weekly irritation, pruritus, • Do not use, or use with caution, in herding breeds Multi for Dogs, lethargy, reduced and their crosses or dogs with confirmed ABCB1- bayerdvm.com; appetite, and 1Delta (MDR-1) gene mutation known as Advocate hyperactivity in Europe) Sarolaner 1 tablet PO Q Vomiting, diarrhea, • Further studies needed to establish protocol, (Simparica, 4 weeks lethargy; may cause efficacy, and safety zoetisus.com) neurologic signs, such • Dogs ≥ 6 months of age as tremors, ataxia, and • Safety has not been evaluated in breeding, pregnant, seizures or lactating dogs 80 DERMATOLOGY DETAILS PEER REVIEWED Amitraz Therapy • Macrocyclic lactones should not be administered to herding breeds and their Amitraz (Mitaban, zoetisus.com) is a crosses, including collies, Shetland sheepdogs, monoamine oxidase inhibitor approved by the Old English sheepdogs, border collies, FDA for treatment of generalized demodicosis bearded collies, and Australian shepherds. 5 in dogs older than 4 months of age. • These dogs have a higher risk of depression, ataxia, coma, and death due to their predisposition to There is good evidence to recommend weekly amitraz the ABCB1-1Δ (MDR-1) gene mutation.3,6 rinses for the treatment of canine demodicosis.1,5 However, based on published reports, amitraz seems • Prior to prescribing macrocyclic lactones to be less efficacious in adult-onset demodicosis.1 in these breeds, it is recommended that evaluation