Demodex

Demodex canis - Wikimedia Commons

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

• Causes demodecosis

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