Canine Demodicosis: Old and New Treatments
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VETcpd - Dermatology Peer Reviewed Canine demodicosis: old and new treatments Canine generalised demodicosis is a common condition seen in dogs, especially in young dogs of certain breeds. Over the years there have been reports on several anti-ectoparasitic products used for the treatment of this condition. In the UK many of them are not licenced for dogs, but for large animal use. In recent years there have been some developments in the treatment of canine generalised demodicosis. This paper discusses the use of older preparations such as amitraz, and the newer preparations such as moxidectin, milbemycin, fl uralaner and afoxolaner in the treatment of the condition. It also mentions the use of unlicensed products such as Dr Anita Patel ivermectin and doramectin. BVM DVD MRCVS Key words: Demodicosis, amitraz, fl uralaner, moxidectin, milbemycin, RCVS Recognised Specialist afoxolaner, ivermectin, doramectin in Veterinary Dermatology Anita Patel runs a busy dermatology referral • Generalised (more than fi ve sites are service out of four clinics in London and Introduction seen on the individual - Figure 3). The the South East of England, she also lectures Demodex mites are normal residents of both in the UK and internationally. She is canine skin; however, they can cause skin clinical signs include multifocal patches recognised by the Royal College as a disease when they multiply excessively. of alopecia, scaling without alopecia, Specialist in Veterinary Dermatology. In dogs, three species – Demodex canis ulceration, crusting, comedones, (Figure 1), Demodex injai (Figure 2) and hyperpigmentation, follicular casts, She has over 20 years’ dermatological papules, pustules, draining sinuses and experience, gaining her certifi cate Demodex cornei, have been associated with sometimes nodules in certain breeds, (CertSAD) in 1993 and her Diploma in clinical disease. The mites are known 2002. As a Specialist, she has dedicated to transfer from the dam to the pup in such as Bull Terriers and Bulldogs. the last 14 years exclusively to small animal the fi rst three days after birth and are • Pododemodicosis occurs in many dogs dermatology. considered normal when present in small with generalised demodicosis; however, Anita co-authored a case based text book on numbers in healthy skin. Their entire life there are a small number of cases where small animal dermatology in the “Saunders cycle occurs on the animal and they feed the feet are the only aff ected site, and Solutions in Veterinary Practice” series, as on skin cells, sebum and epithelial debris. occasionally only a single foot is aff ected. well as chapters in various dermatology text Their excessive multiplication is thought In many cases there is also a concurrent books. She has published papers in refereed to result from a specifi c T-cell defect in deep pyoderma (Figure 4). and peer reviewed journals and is actively the host, which again is thought to be an • Adult-onset demodicosis occurs involved in all aspects of dermatology. inherited predisposition. Other predispos- when the condition develops in an ing factors include age, poor nutrition, t: 01883 623761 adult individual that, when young, did hormonal changes, endoparasitic infection e: [email protected] not have the disease. This form can be and neoplasia. Secondary pyoderma often localised, generalised, or restricted to complicates the condition, resulting in the feet. Adult-onset demodicosis is further immunosuppression of the host associated with systemic diseases such and multiplication of the mite. as hyperadrenocorticism (iatrogenic or The clinical forms of demodectic spontaneous), neoplasia, and with the use mange are: of immunosuppressive drugs (Figure 5). • Localised (less than fi ve small • Seborrhoea oleosa on the trunk, circumscribed patches of scaling and often accompanied by erythema, alopecia with or without erythema). hyperpigmentation and sometimes This form is usually seen in young dogs comedones, is seen in West Highland and the lesions tend to appear around White Terriers (Figure 6), Border Terriers and Fox Terriers. This syndrome For Dermatology Referrals in your the eyes, muzzle, limbs, and/or trunk. is often associated with Demodex injai. area: vetindex.co.uk/derm Generally the lesions are non-pruritic, unless there is secondary bacterial For Lab Tests and Equipment: • Facial pruritus and dermatitis is seen infection. In most individuals (90%) vetindex.co.uk/Lab in some breeds such as Shih Tzus and the lesions will resolve spontaneously West Highland White Terriers. Often Market your referrals in VetIndex! (within 1-3 months); however, in a small the dogs have concurrent Malassezia For further information call us on 01225 number they either persist, or go on to dermatitis and pyoderma. This presenta- 445561 or e-mail: [email protected] become generalised. tion is associated with Demodex injai. Page 14 - VETcpd - Vol 3 - Issue 2 VETcpd - Dermatology Diagnosis use in dogs, but used under the cascade, Treatment The diagnosis is confirmed by microscopy and some too expensive to implement for There are several treatments available for on deep skin scrapings and hair plucks. In some owners. Concurrent treatment of demodicosis and clinical guidelines for the cases with a purulent exudate, large num- pyoderma is an essential part of the treat- treatment of this condition were published bers of mites may be present in the exudate. ment, and not treating this will often lead in 2012 (Muller et al.). Many of them are In dogs with adult-onset demodicosis it to treatment failure of the demodicosis. off-label uses of drugs otherwise licensed is important to look for the trigger, or an The treatment for demodicosis should for dogs, or are only licensed for use in associated immunosuppressive condition. be continued for two weeks beyond two large animals. Since 2012, there have been consecutive negative skin scrapes, taken further developments, which are discussed Over the years, the condition has been two weeks apart. The first set of follow-up in this paper. treated with many different ectoparasiti- scrapes should be taken four weeks after cidal agents, some more effective than starting treatment. Amitraz others, some more difficult to adminis- Amitraz (Aludex; MSD) is one of the ter, some with serious adverse effects in This paper will now discuss some of the oldest products licensed for use in dogs some individuals, some not licensed for older and more recent treatments available. and a very effective acaricide of the formamidine family. It is a monoamine oxidase inhibitor, α-adrenergic agonist and prostaglandin inhibitor. Its mode of action is thought to be via the octopamine receptor in ectoparasites, resulting in neuronal hyperexcitability and death of the parasite. It is used mainly for the treatment of demodectic mange. A 250-500 ppm solution (0.025% w/v – 0.05% w/v) is applied every 7-14 days to the whole body including the feet. To maximise the efficacy of the Figure 1: Demodex canis mites on a hair pluck Figure 4: Doberman with pododemodicosis treatment, clipping of medium to long- haired dogs is essential and wetting of the skin in-between applications should be avoided. The treatment should be carried out in a well ventilated room and the manufacturer’s instructions followed regarding the disposal of the product. In practice, between 8-12 applications are generally needed for the complete resolution of a generalised demodicosis (Figures 7a and 7b). Figure 2: Demodex injai. Note the long body with Figure 5: Adult-onset demodicosis associated slender tail with glucocorticoid therapy in a West Highland White Terrier Figure 7a: Pre-treatment Figure 3: Generalised demodicosis. Note more than Figure 6: Greasy, erythematous skin associated Figure 7b: Post-treatment. 10 weekly applications five patches on the dorsum of an English bulldog with Demodex injai of amitraz Full article available for purchase at www.vetcpd.co.uk/modules/ VETcpd - Vol 3 - Issue 2 - Page 15.