Veterinary Medicine - August 2008 - (Page 458)

Demodicosis PEER-REVIEWED Dodge) given orally at 400 µg/kg/day can be effective in treating generalized demodicosis.10,27,28 Moxidectin can be started at a lower dose and then gradually increased to 400 µg/kg/day similar to ivermectin, as outlined above. Consider treatments other than moxidectin for ivermectin-sensitive breeds.29 Recently, an imidacloprid (10% w/v) and moxidectin (2.5% w/v) spot-on (Advantage Multi—Bayer Animal Health) was introduced in the United States as a heartworm, intestinal parasite, and ea preventive. A similar European product (Advocate—Bayer HealthCare) is labeled to treat and prevent ea infestation, treat ear mite infestation, treat sarcoptic mange, treat demodicosis (caused by D. canis), prevent heartworm disease, and treat gastrointestinal nematodes. This spot-on product was evaluated in the treatment of generalized demodicosis through a multicenter, randomized, blinded eld trial during the registration process in Europe.30 Another group of dogs with generalized demodicosis was treated with daily milbemycin oxime and served as the control group. Dogs were treated with the spot-on two to four times, at four-week intervals, with the test product at the recommended dose of at least 0.1 ml/kg. Up to ve body sites were scraped each month to look for Demodex species mites. Treatment was discontinued when two subsequent monthly skin scrapings were negative for living mites or at the last examination on day 84. At study end, 87% of the treated dogs and 88% of the control dogs had no live mites on skin scrapings with no difference in clinical response between the groups. A limitation of the study is the exclusion of dead mites and mite segments from evaluation. It is also unknown whether dogs cleared of mites relapsed after the study because skin scrapings were not obtained after treatment discontinuation. Although this moxidectin spot-on appears to be equally effective when compared with milbemycin oxime in the treatment of generalized demodicosis using the criteria of this study, more long-term studies with stricter evidence for parasitologic cure 12. An adult Demodex cati mite (50X). are needed to corroborate these ndings. Based on the experience of our European colleagues, treatment failures with this product are not uncommon. 13. An adult Demodex gatoi mite (100X). complete cure is declared if no relapses occur within 12 months from the time of treatment discontinuation.12 Doramectin—Doramectin, another avermectin, has been used in a study involving 23 dogs that received weekly subcutaneous injections of 600 µg/kg.10,31 None of the animals showed adverse effects with doramectin; however, this drug should not be used in ivermectin-sensitive breeds of dogs. More research is needed to evaluate doramectin for treating demodicosis.10 FELINE DEMODICOSIS: CLASSIFICATION AND DIAGNOSIS Cats have two recognized species of Demodex mites. Microscopically, Demodex cati is similar in appearance to the canine mite D. canis (Figure 12).32 Likewise, it lives in the hair follicle. Although dif cult to nd, D. cati may be seen in clinically healthy cats as part of the normal cutaneous ora. The short-bodied cat Demodex mite is Demodex gatoi. Like D. cornei in dogs, it resides in the stratum corneum layer of the epidermis. Demodex gatoi is about 55% shorter than the average length of D. cati and has a rounded opisthosoma (tail) (Figure 13).33,34 This species is considered potentially contagious to other cats. Monitoring Clinical signs and microscopic examination of skin scrapings are used to guide treatment for generalized demodicosis. Repeat skin scrapings every two to four weeks during treatment. Sample at least four to six affected body sites including the face and paws at each recheck. Obtain samples from the same body areas to consistently monitor the mite population. Once all scrapings are negative for mites at any developmental stage, including dead mites or mite fragments, a parasitologic cure can be declared.8,12 If eggs or immature mite numbers do not decrease over four to eight weeks, consider altering the dose or frequency of the given treatment. Miticidal treatment continues until two consecutive negative skin scrapings collected two to four weeks apart are obtained. Chronic cases bene t from an additional month of therapy beyond the two negative scrapings. A Clinical signs Clinical signs of feline demodicosis secondary to D. cati infection are generally similar to those of canine demodicosis secondary to D. canis infection. Alopecia, erythema, crusting, and ceruminous otic discharge can all occur with D. cati infection. Pruritus may or may not be present. Clinical demodicosis due to D. cati infection in cats is often related to mite overgrowth secondary to an underlying systemic disease or immunosuppression.35,36 Cats with demodicosis secondary to D. gatoi infection typically present for 458 August 2008 VETERINARY MEDICINE

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Veterinary Medicine - August 2008 Contents Editors' Note Leading Off ClinQuiz Idea Exchange Practical Matters Diagnosing and Treating Canine Copper-Associated Hepatopathies Canine and Feline Demodicosis CE Form Advertiser Index Product Preview Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - August 2008

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