canis - Articles
Skin: demodectic mange
Synonym(s): Demodicosis
Introduction
- Inflammatory, parasitic skin disease of dogs.
- Cause: Demodex 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.
Presenting signs
- Localized demodicosis
: focal alopecia young dogs <12 months old. - Generalized demodicosis
: generalized lesions 
, secondary deep pyoderma 
, young dogs < 18 months old. - Adult-onset demodicosis: generalized lesions, secondary deep pyoderma, adult dogs >18 months old.
- Pododemodicosis
: feet only affected, secondary pyoderma common. - Otodemodicosis: ceruminous otitis externa.
- Demodex injae causes a greasy, mildly alopecic disease which may be pruritic and which predominantly affects the dorsum and head of adults.
Age predisposition
- Localized: <1 year old.
- Generalized: <1.5 years old.
- Adult onset: >1.5 years old.
Breed/Species predisposition
- Breed predispositions vary according to area and there is some evidence of variation over time as well.
- Staffordshire bull terrier Staffordshire bull terrier.
- Scottish terrier Scottish terrier.
- Weimaraner Weimaraner.
- Airedale terrier Airedale terrier.
- Alaskan malamute Alaskan malamute.
- Afghan hound Afghan hound.
- Shih Tzu Shih Tzu.
- Dobermann Dobermann.
- Great Dane Great Dane.
- Chihuahua Chihuahua - Long Coat.
- Old English Sheepdog Old English Sheepdog.
- Shar Pei Chinese Shar Pei.
- West Highland White Terrier West Highland White Terrier.
- Dalmatian Dalmatian.
- Boxer Boxer.
- German Shepherd Dog German Shepherd Dog.
- Cocker Spaniel English Cocker Spaniel.
- Bulldog Bulldog.
- Boston Terrier Boston Terrier.
- Dachshund Dachshund.
- Pug Pug.
- Pointer Pointer.
- Bull Terrier Bull Terrier.
- Cavalier King Charles Spaniel Cavalier King Charles Spaniel.
- Demodex injae disease seems to be more common in terriers, especially West Highland White terriers, and Shih Tzu.
Public health considerations
- None - Demodex sp do not cross species barriers.
Cost considerations
- Can be high for generalized demodicosis.
- Lower now with new treatments.
Pathogenesis
Etiology
- Three species of Demodex have been reported as normal commensals in the dog:
- Demodex canis Demodex canis
- follicular mite. - Demodex cornei.
- Demodex injae.
- Demodex canis Demodex canis
- Demodex canis is most commonly associated with generalized demodicosis.
Predisposing factors
Adult onset
- Serious metabolic disease.
- Immunosuppressive therapy.
- Malignant neoplasia Skin: neoplasia.
- Stress.
- Endoparasite infestation.
- Deep mycoses Skin: mycotic disease.
Specific
- Hyperadrenocorticism Hyperadrenocorticism.
- Glucocorticoid therapy.
- Hypothyroidism Hypothyroidism.
- Lymphosarcoma Lymphoma.
- Hemangiosarcoma Hemangiosarcoma.
- Mammary adenocarcinoma Mammary gland: neoplasia.
- Diabetes mellitus Diabetes mellitus.
- Estrus.
- Whelping.
- Malnutrition.
- Hookworm infestation Uncinaria stenocephala.
- Heartworm disease Canine cardiopulmonary dirofilariasis.
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.
- See also Demodex canis Demodex canis.
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
. - 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.
- Mueller R S, Rosenkrantz W, Bensignor E, Karaś-Tęcza J, Paterson T, Shipstone M A (2020) Diagnosis and treatment of demodicosis in dogs and cats: Clinical consensus guidelines of the World Association for Veterinary Dermatology. Vet Dermatol 31(1), 5-27 PubMed.
- 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