Lora, 4-year-old female cross breed dog, was presented for large area of erythema and pustules on the left flank and squamosis zones on the dorsum. There was a mild pruritus. This dog was diagnosed with erhlichiosis and anaplasmosis one month ago and she was treated with injectable dexamethasone and oral doxycycline by her veterinarian. The general condition during the first consultation a month ago was poor with lethargy, icterus and anorexia. 7 days before the presentation the general condition of the dog was much better but skin lesions started to appear. The dog has never had any skin problems before.
Clinical examination revealed small areas on the dorsum with squamosis (fig.1) and alopecia, some areas with alopecia, erythema, comedones and crusts (fig. 2). The most prominent lesion was a large area with erythema, papules, pustules and crusts on the left flank (fig.3 and fig 4).
Skin scrapings were positive with Demodex canis in all microscopic fields. There were more than 100 Demodex spp visible on skin scraping slide. Demodex canis was visible on the scotch tests as well (fig.5a and fig.5b). Microscopic observation of impression smears revealed pyogranulomatous inflammation (degenerated neutrophils and macrophages)(fig.6) with figures of phagocytosis (fig.7) and Demodex spp (fig.8) as well. The diagnosis is Demodicosis, probably secondary to treatment with corticosteroids, and secondary deep pyoderma.
Treatment The acaricidal therapy was with oral ivermectin. The ivermectin administation started with gradual dose increase from 0,05 mg/kg on day 1,0,1 mg/kg on day 2, 0,15 mg/kg on day 3, 0,2 mg/kg on day 4, 0,3 mg/kg on day 5, 0,4 mg/kg on day 6 and 0,5 mg/kg on day 7 and keeping this dose for 30 days until the first scraping control. Because of the presence of infection antibiotic treatment with amoxicillin-clavulonic acid was started (15 mg/kg BID for 30 days until first control).Topical antimicrobial therapy with benzoyl peroxide (Peroxyderm, Vetoquinol) every 3 days was also recommended. All kind of steroids was stopped.
Evolution The dogs supported very well all components of the treatment. 35 days after the first dose of ivermectin, skin scrapings were performed and there were 5 demodex ssp seen in total. The clinical lesions were gone at least 7 days ago, so the antibiotic was stopped, the shampooing was diminished in frequency (once weekly), the ivermectin was continued at 0,5 mg/kg for 30 more days. 65 days after the initial presentation, skin scrapings were performed and they stayed positive with 4 Demodex found on the slide. The ivermectin was continued for 30 more days. Approximately 95 days after the initial examination, skin scrapings were negative for the first time so the ivermectin was continued for 30 more days. 125 days after the initial presentation the skin scrapings were negative for second time. Complete resolution of the previous clinical lesions was seen in the first 30 days of the treatment, but the treatment stopped after 2 negative skin scrapings control. Pictures are taken 11 months after the first dermatological consultation (Fig. 9). There wasn`t any relapse for 7 months after the last ivermectin dose.
Discussion When the dogs first experience the disease at 4 years of age or older, they have true adult-onset demodicosis. This form of demodicosis is rare. When it occurs, different underlying conditions are recongnized. Such disorders are hypothyroidism, hyperadrenocorticism, leishmaniasis, malignant neoplasia, immunosuppressive treatments for cancer or autoimmune diseases. In more than 50% of cases, no underlying disease can be proven at the time of diagnosis demodicosis. In this case the precious corticosteroids treatment, the complete recovery and the lack of relapse for more than 6 months after the last ivermectin dose indicate that the main possible reason is the corticosteroid treatment.
Small Animal Dermatology, 7th edition, Miller, Griffin, Campbell, 2013