Consultant on Call Dermatology Peer Reviewed

Sarcoptic

Adam P. Patterson, DVM, DACVD Texas A&M University

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Definition n Sarcoptic mange (ie, sarcoptic ) is a transmissible dermatosis caused by the burrowing acarid scabiei. n , referred to as , often results in acute and intense pruritus. n Common in domestic dogs and rare in cats, sarcoptic mange can affect other mammalian species (eg, foxes, rabbits, guinea pigs, ferrets, sheep, goats, cattle, pigs, Spanish ibex, humans). n Scabies occurs worldwide but is more prevalent in some regions because of envi- o S scabiei var suis (pig) Although transmission n ronmental conditions. Variants tend to infect certain hosts but may occur otherwise, * can cause disease in other species. Signalment★ o Feline scabies is caused by Notoedres direct contact with a scabies- n No age, sex, or breed predilections cati; however, S scabiei has reportedly infested , especially 1 n Young patients may be at increased risk caused disease in cats (rare). n in an overcrowded area, because of exposure in overcrowded areas Location of the mite anus helps dis- (eg, shelter, kennel, pet store, breeding tinguish between S scabiei var canis increases the risk for mill, boarding or training facility). and N cati (terminal in the former, dorsal in the latter). transmission. Causes Risk Factors n S scabiei is an obligate parasite that n spends its entire 14–21-day life cycle on While not always necessary, direct con- the host. tact with an infested animal, especially in n Scabies are named as variants of an overcrowded area, increases the risk their preferred host species. for transmission. n o S scabiei var canis (dog) Other risk factors include fox-dense o S scabiei var vulpis () regions and immunosuppression. o S scabiei var ovis (sheep)

o S scabiei var bovis (cattle)

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Pathophysiology hocks, and ventral trunk and hyperkeratotic calluses on n Clinical disease can develop when an (Figure 2) elbows and hocks affected animal’s mites are transmit- o May become widespread as alope- o Aural hematoma can occur at any ted to the skin of another animal. cia becomes more severe disease stage. n After the mites penetrate the skin, o Dorsum and paws are often o Some dogs may not develop skin they burrow, feed, and reproduce in spared (Figure 3). lesions despite intense pruritus (ie, superficial skin layers, often in areas n Lesions scabies incognito), while others (ie, with little hair. o Peracute: Lesional pruritus that immunosuppressed) have wide- n Pruritus occurs may mimic allergic skin disease spread lesions with minimal pruri- o When mite population increases o Acute: Erythematous maculopap- tus (ie, crusted or Norwegian o Through suspected hypersensitiv- ular eruptions that eventuate into scabies). ity reaction to mite antigens crusted papules with excoriations n Secondary skin infection n Because S scabiei and house dust and alopecia o Superficial pyoderma and/or mites share similar antigens, antibody o Chronic: Diffuse exfoliation with Malassezia spp are cross-reactivity (influencing allergy hyperpigmented lichenification common sequelae. test interpretation) and cosensitiza- tion are possible.

History n Historical clues suggestive of scabies may include o Acute and severe nonseasonal pruritus o Exposure to roaming foxes o Recent history of adoption or boarding o Cohabitation with multiple , several of which may 1 be pruritic o Lack of acaricidal therapy in Sarcoptic mange presenting as crusting excoriation along the left caudolateral elbow of a dog. monthly ectoparasite preventives o Fair-to-poor response to previ- ously administered antiinflamma- tory glucocorticoids and/or cyclosporine o Humans in the household may be pruritic and have erythematous papules.

Clinical Signs Dogs n Pruritus o Moderate to extreme o Observable at physical examination n Distribution o Sparsely haired body regions: 2 Pinnal margins (not otic canals), periocular skin, elbows (Figure 1), Pruritic papular with lichenification on ventral trunk of a dog with sarcoptic mange.

16 cliniciansbrief.com • June 2014 Distribution pattern of disease for canine scabies.2 Common Less Common Cats n gatoi infestation 3 n Otodectic mange n Cheyletiellosis n n Herpesvirus dermatitis n Allergic skin disease

Laboratory Testing Indicated n Skin surface cytology to exclude concurrent bacterial and/or fungal infection n Extracutaneous signs n Paucity of S scabiei exists when dogs o Lethargy are hypersensitive to mite antigens, May be Indicated o Depression so negative skin scrapings and/or n ELISA serologic testing for IgG o Inappetence fecal examination do not exclude against Sarcoptes spp antigens o Weight loss scabies. o Available in some countries, but o Peripheral lymphadenomegaly n Mites are usually numerous and easy to false-positive (eg, cross-reactivity n Nonclinical carriers may exist. find on skin scrapings from immuno- with house dust mite) and negative suppressed dogs (crusted scabies). (eg, dogs receiving glucocorti- Cats coids) results can occur. n n Pruritus is nonexistent to moderate. Differential Skin biopsy to exclude other n Distribution on bridge of nose, face, Dogs differentials n CBC, serum chemistry panel, urinal- pinnae, paws, and tail n Folliculitis (eg, superficial pyoderma, ysis, and feline retroviral testing n Lesions include crusted papules and , ) when other comorbidities are sus- alopecia. n Malassezia spp dermatitis pected as based on history and physi- n Extracutaneous signs include poor n Pelodera spp mange cal examination body condition and peripheral n Allergic skin disease n Before extralabel macrocyclic lactone lymphadenomegaly. n Contact dermatitis therapy n Ear margin dermatosis o Testing for heartworms when sta- n Zinc-responsive dermatosis 1-4 tus is unknown or questionable Diagnosis n Pemphigus foliaceus o ABCB1Δ genetic testing to screen n Neoplasia Definitive for avermectin sensitivity in iver- mectin-sensitive dogs (eg, herding n Definitive evidence involves micro- dogs, sight hounds) before the use scopic finding of scabies mites, mite of extralabel macrocyclic lactone eggs, or mite feces (Figure 4) on therapy superficial broad skin scrapings from representative nonexcoriated lesions or fecal flotation findings. Treatment1-4,8,9 n Circumstantial evidence includes his- tory, signs, and positive pinnal–pedal n Dogs with unexplained pruritus, par- response (uncontrollable scratching/ ticularly unresponsive to glucocorti- thumping with a pelvic limb when the coids (eg, prednisone 1 mg/kg q24h) *ipsilateral pinnal margin is scratched). 4 should receive trial therapy for sca- o Clinical resolution following bies before making a diagnosis of ★appropriate scabicidal therapy also Sarcoptic acariasis mite allergy. indicative Courtesy of Dr. Thomas Craig, Texas A&M University MORE * June 2014 • Clinician’s Brief 17 ★ Consultant on Call

n Duration of scabicidal therapy should Nutritional Aspects fine mist to entire skin surface encompass at least two mite life cycles n The patient should receive an q2–3wk 3 doses or 6 mL/kg (at least 4–6 weeks) regardless of the age-appropriate balanced diet. sponged on the skin q7d 4–6 doses product prescribed. n May be better reserved for subclinical n S scabiei can be transmitted to other Client Education close-contact dogs close-contact animals and humans; n Humans who develop itchy skin all close-contact animals (notably (± lesions) should contact their Feline Sarcoptic Mange dogs) should be treated concurrently. physician. Systemic n In general, systemic scabicidal ther- n : 0.2–0.3 mg/kg SC q2wk apy (including correctly applied sys- 3–4 doses temic spot-on) is more effective than 1-7, 9-12 Medications n Doramectin: 0.2–0.3 mg/kg SC as a topical treatment for scabies because single dose or repeated in 2 weeks of improved compliance. Note: Recommended treatments are n 2.5% + imidacloprid 10% n Assuming all close-contact animals mostly considered extralabel as described. topical spot-on: Applied q2wk 3–4 are treated, environmental decontam- doses (based on manufacturer’s ination is not typically needed, unless Canine Sarcoptic Mange established body weight range) scabies outbreak occurs in an over- n Selamectin topical spot-on: Applied crowded facility. Systemic n n *Ivermectin: 0.2–0.4 mg/kg SC q14d q2wk 3–4 doses (based on manufac- Scabies-infested dogs and cats can be turer’s established body weight range) treated as outpatients; use of topical ★3–4 doses or 0.2–0.4 mg/kg PO q7d amitraz dips (dogs) should be 4–6 doses reserved for in-hospital use. n Doramectin: 0.2–0.6 mg/kg SC q7d Topical 4–6 doses n Lime : 2%–3% solution applied Supportive Medical Care n Moxidectin: 0.2–0.3 mg/kg SC q7d to entire skin surface q7d 4–6 doses (see Medications) 3–4 doses or 0.2–0.3 mg/kg PO q7d o Do not rinse. o n Antiseborrheic can facilitate 4–6 doses May need to clip coat to facilitate removal of excessive surface scale and n Moxidectin 2.5% + imidacloprid 10% contact crusting. topical spot-on: Applied q2–4wk 2–4 n Concurrent pyoderma and/or Malas- doses (based on manufacturer’s Precautions & Drug Interactions sezia spp dermatitis must be treated. established body weight range) n Dogs with an ivermectin-sensitive o In dogs, systemic azole therapy n Selamectin topical spot-on: Applied genotype (eg, herding dogs, sight (inhibitor of P-glycoprotein) can- q2–4wk 3–4 doses (based on manu- hounds) should not receive extra- not be given concurrently with facturer’s established body weight label macrocyclic lactone therapy (eg, extralabel (high-dose) macrocyclic range) ivermectin, doramectin, moxidectin) lactones such as ivermectin (sub- o Dermatologists have safely used this because of risk for neurotoxicosis strate of P-glycoprotein), as doing protocol in herding canine breeds. signs. so may cause signs of ivermectin- n Neither spinosad-containing pre- sensitivity. Topical ventives nor systemic azole therapy o Sole topical therapy directed n Amitraz: 0.025%–0.03% solution (eg, ketoconazole, itraconazole) can against yeast may be needed to applied to entire skin surface q1–2wk be given concurrently with extralabel avoid potential drug interactions. 4–6 doses macrocyclic lactones in any dog n Worsening pruritus is normal during o Do not rinse. (neurotoxicosis). the first days of treatment, so sys- o May need to clip coat to facilitate n Amitraz dip treatment should be temic glucocorticoids (dogs, predni- contact used cautiously in small dogs and sone 1 mg/kg PO q24h 3–7d; cats, n Lime sulfur: 2%–3% solution applied should not be used for Chihuahuas. prednisolone 2 mg/kg PO q24h 3–7d) to entire skin surface q7d 4–6 doses o Do not administer concurrently or oclacitinib (dogs, 0.4–0.6 mg/kg o Do not rinse. with monoamine oxidase inhibi- PO q12h 3–7d) are often indicated. o May need to clip coat to facilitate tors in any dog. n Aural hematomas should be contact o Whether amitraz is optimal decompressed. o Fipronil spray: 3 mL/kg applied as should be strongly considered;

18 cliniciansbrief.com • June 2014 in-hospital application is recom- Complications mended, and administrative per- n Treatment failure may occur if Cost Key sonnel are at risk for adverse effects. o Using topical spot-on for patients $ = up to $100 n For nonclinical dogs, fipronil spray with body weights nearing the $$ = $101–$250 $$$ = $251–$500 may be cost-effective in a multidog upper limit of the manufacturer’s $$$$ = $501–$1000 household. recommended body weight range $$$$$ = more than $1000 (ie, underdosed therapy) o All close-contact animals (espe- Follow-up cially dogs) or secondary infec- Prognosis tions are not concurrently treated n Good Patient Monitoring n Pruritus should be significantly Prevention *improved after the first two doses of In General n Routine use of flea preventives con- scabicidal therapy (within 3 weeks), taining may lessen chances Relative* Cost ★but mild pruritus may linger for sev- for scabies after casual exposure to an eral weeks. ★n Canine sarcoptic mange: $–$$ infested animal. n cb n If skin lesions fail to improve after n Feline sarcoptic mange: $–$$ 3–4 weeks of therapy, skin culture n Sarcoptic mange in multipet house- See Aids & Resources, back page, for and/or biopsy may be indicated. hold: $$$–$$$$ references & suggested reading.

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