Canis ISSN: 2398-2942

Skin: demodectic mange

Synonym(s): Demodicosis

Contributor(s): Karen Campbell, David Godfrey

Introduction

  • Inflammatory, parasitic skin disease of dogs.
  • CauseDemodex canis Demodex canis and other species of Demodex mites present in hair follicle and sebaceous glands of normal dogs.
  • Unknown factor → proliferation of Demodex mites → inflammation and hair loss.
  • Secondary superficial and deep pyoderma common.
  • Signs: alopecia.
  • Diagnosis: skin scrape, histology.
  • Treatment: none unless secondary infection or generalized.
  • Prognosis: Isoxazolines have revolutionized treatment of generalized demodicosis; when previously it was guarded the prognosis is now good. 

Pathogenesis

Etiology

  • Three species of Demodex have been reported as normal commensals in the dog:
    • Demodex canis Demodex canis Demodex canis adult 01 - follicular mite.
    • Demodex cornei.
    • Demodex injae.
  • Demodex canis is most commonly associated with generalized demodicosis.

Predisposing factors

Adult onset

  • Serious metabolic disease.
  • Immunosuppressive therapy.

Specific

Pathophysiology

  • Not completely understood - probably due to an inability of the host to regulate mite numbers - possibly an inherited specific T cell deficiency +/- other immunosuppressive conditions.
  • Two distinct age groups affected by generalized disease:
    • Juvenile-onset <18 months of age.
    • Adult-onset >4 years with no previous history of disease - immunosuppressive disease may be present but not diagnosed until 12-18 months after onset of demodicosis.

Generalized demodicosis

  • Defined as:
    Either Five or more areas of localized disease.
    Or Pododemodicosis with two or more feet affected.
    Or An entire body region affected.
  • Squamous form - minimal erythema or discharge; patchy alopecia and exessive scale; pigmented comedone formation. Bacterial infection usually absent.
  • Pustular form - extensive bacterial infection with folliculitis and furunculosis; exudate, plaques, crusting and scaling; hyperpigmented skin and comedone formation at the margins of pustular areas; may be painful and sepsis may cause anorexia, lethargy and depression.

    Pyoderma can cause immunosuppression and further mite proliferation and subsequent failure of miticidal treatment.
Normal puppies
  • Demodex canis transferred from dam at 2-3 days old → low or moderate Demodex multiplication → no lesion or localized demodicosis with spontaneous healing.
Genetically predisposed puppies
  • Demodex canis infection at 2-3 days old → moderate Demodex multiplication and suppressor T-lymphocyte suppression (hereditary deficiency) → B-lymphocyte overactivity → production of humoral factor (parasitic antigen-antibody complex) → secondary generalized immunodeficiency → generalized demodicosis and deep pyoderma Skin: deep pyoderma.
  • Staphylococcal pyoderma may be involved in immunosuppression.

Timecourse

  • Weeks to years.

Epidemiology

  • Demodex canis lifecycle completely on host Lifecycle Demodex canis - diagram.
  • Fusiform egg → 6-legged larvae → 8-legged protonymph → adult.
  • Transmission by direct contact from bitch to puppies during first 2-3 days after birth.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Becskei C, Cuppens O & Mahibir S P (2018) Efficacy and safety of sarolaner against generalized demodicosis in dogs in European countries: a non-inferiority study. Vet Dermatol 29 (3), 203-e72 PubMed.
  • Synder D E, Wiseman S & Lilenberg J E (2017) Efficacy of lotilaner (Credelio™), a novel oral isoxazoline against naturally occurring mange mite infestations in dogs caused by Demodex spp. Parasit Vectors 10 (1), 532 PubMed.
  • Beugnet F, Halos L, Larsen D et al (2016) Efficacy of oral afoxolaner for the treatment of canine generalized demodicosis. Parasite 23, 14 PubMed.
  • Six R H, Becskel C, Mazaleski M M et al (2016) Efficacy of sarolaner, a novel oral isoxazoline, against two common mite infestations in dogs: Demodex spp and Otodectes cynotis. Vet Parasitol 222, 62-66 PubMed.
  • Fourie J, Liebenberg J E, Horak I G et al (2015) Efficacy of orally administered fluralaner (Bravecto) or topically applied imidacloprid/moxidectin (Advocate) against generalized demodicosis in dogs. Parasit Vectors 8, 187 PubMed.
  • Shipstone M (2000) Generalised demodicosis in dogs, clinical perspective. Aust Vet J 78 (4), 240-242 PubMed.
  • Chesney C J (1999) Short form of Demodex species mite in the dog - occurrence and measurements. JSAP 40 (2), 58-61 PubMed.
  • Paradis M (1998) Ivermectin in small animal dermatology Part II. Extralabel applications. Comp Cont Ed Prac Vet 20 (4), 459-469 VetMedResource.
  • Kwochka L W, Kunkle G A & Foil C O (1995) The efficacy of amitraz for generalised demodicosis in dogs - a study of two concentrations and frequencies of application. Comp Cont Ed Prac Vet (1), 8-17 VetMedResource.
  • Foley R H (1991) Parasitic mites of dogs and cats. Comp Cont Ed Prac Vet 13 (5), 783-800 VetMedResource.
  • Smith E K (1988) How to detect common skin mites through skin scrapings. Vet Med 83 (2), 165-170 VetMedResource.

Other sources of information

  • Miller W H Jr, Griffin C E & Campbell KL (2013) Canine demodicosis. In: Muller and Kirk's Small Animal Dermatology 7th editionW B Saunders, Philadelphia. pp 304-313 (Detailed dermatology textbook for in-depth reading.)
  • Kwochka K W (1993) Demodicosis. In: Current Veterinary Dermatology - the Science and Art of Therapy. Eds. C E Griffin, K W Kwochka & J M MacDonald. St Louis: Mosby Year Book. pp 72-84. (Excellent diagnostic criteria chart and treatment plan.)


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