Demodex

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Demodex canis - Wikimedia Commons
  • Demodex spp. found on all domestic mammals and in humans
    • Each host has its own species


Recognition

  • Cigar shaped
  • Four pairs of stumpy legs on the anterior end
  • Long and narrow to fit into hair follicles


Life cycle

  • Live as commensal organisms
  • Live in hair follicles and in sebaceous glands
  • Life cycle takes 3 weeks


Pathogenesis and epidemiology

Dogs

  • Initial infection is slight hair loss which may resolve spontaneously or could spread over the body
  • 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


Cats

  • Rare
  • Confined to the periocular region
  • Mild squamous type only


Cattle

  • Pea-sized nodules in the skin
    • Each nodule contains several thousand mites
  • Affects hide quality
    • Economically important in Australia


Goats

  • Becoming more common in goats
  • Disease similar to that in cattle


Pigs, Sheep and Horses

  • Rare


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