Demodicosis

References

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