Demodicosis

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Caused by Demodex

Pathogenesis and epidemiology

  • Squamous demodecosis
    • Less serious
    • Dry reaction
    • Alopecia, desquamation and skin thickening
    • Absent to mild pruritus
  • Follicular/pustular demodecosis
    • More serious
    • Skin invasion by staphylococci
    • Skin becomes wrinkled, thickened and contains pustules which ooze serum, blood or pus
    • Affected animals may be seriously disfigured
    • Severe pruritus is associated with secondary infection
  • Immune factors are important in determining the severity and occurrence of demodecosis
    • Familial susceptibility
    • Immunosuppression
    • Immunosuppressant therapy

Diagnosis

  • Liquid paraffin applied to a skin fold
  • Deep skin scraping

Control

  • Not easily accessible to acaricides due to their deep location in the skin
  • Repeat treatments needed
  • Recovery may take several months
  • To aid acaricide penetration, clipping a dog's coat and washing is recommended

=From Pathology

  • Demodex are normal inhabitants of hair follicles and sebaceous glands
  • Have to have increased number of immature mites to classify as infestation
  • Host-specific
  • Occurs in dogs, cattle, sheep, goats, pigs, horses and cats
  • Transmits during nursing from dam to offspring
  • Demodex canis in dogs:
    • Generalised or localised
    • Mainly young dogs affected or adults with other disease (hyperadrenocorticism, hypothyroidism)
    • Often inherited in pure bred
    • Grossly:
      • Localised: scaly, erythematous, macular, alopecic areas; usually face or front legs
      • Generalised: large, coalescing lesions, patches, erythema, alopecia, scales, crusts
    • Microscopically:
      • Localised: lymphoplasmacytic perifolliculitis with hyperkeratinisation, sebaceous adenitis, low pigment, intraluminal mites
      • Generalised: perifolliculitis and follicular hyperkeratosis, follicular pluggingf, bacterial proliferation, bacterial neutrophilic folliculitis
        • May cause folliculat rupture -> furunculosis, cellulitis, lymphadenitis and septicaemia

Dogs

Cats

Cattle

Goats

Pigs

Sheep

Horses