Psoroptic Mange

Caused by Psoroptes

• Occurs in cattle, sheep, horses, goats, rabbits and other animals
• Host-specific
• Psoroptes cuniculi in ear canals of rabbits, horses, goats and sheep

Pathogenesis

• The ears are painful and intensely pruritic

• Affected rabbits shake their heads and scratch their ears

• The inner surfaces of the pinnae are covered with brown, scaly, fetid material, and the skin beneath is raw

• Mites are grossly visible

• Histologically, there is chronic erosive and proliferative eosinophilic dermatitis
  • The mites are non-burrowing and thus are found only in the exudate, not in the tissue

Diagnosis

• Microscopic examination for mites (low magnification)

• Appearance

Control

• Infestations are difficult to eliminate from a colony
  • Ivermectin is usually effective.

• P.equi at base of mane, tail and forelock in horses
• P.ovis in sheep (sheep scab)and cattle
  • Thickened skin and dry scales and crusts
  • Starts at withers and spreads due to self trauma
  • Microscopically:
    • Spongiotic, hyperplastic or exudative superficial perivascular dermatitis
    • Eosinophils

Pathogenesis

• Economically important ectoparasite of sheep

• Causes sheep scab
  • Wool loss, restlessness, biting, scratching of infested area and decreased productivity through decreased weight gain
  • Usually seen in late autumn and early winter (although may also occur in late summer)
  • Population numbers decline after shearing due to a change in the micro-climate, then build up again as the fleece grows
  • Notifiable in UK

• Mites found under scabs and in skin folds

• Lesions most common on flanks, neck, back and shoulders

• Causes pruritic condition of cattle

• Active in keratin layer

• Mouthparts abrade the skin

• Antigenic material in mite faeces can lead to hypersensitivity reactions

Diagnosis

• Skin scraping

• KOH added

• Warm slide over a bunsen flame

• Examine under a microscope

Treatment

• Sheep
  • Plunge dipping; no less than 1 minute and must dip head at lease once
  • Can treat with avermectins or milbemycins by injection

• Cattle, horses and rabbits
  • No licensed product for horses in the UK
  • Cattle and rabbits can be treated with avermectins, milbemycins or topical acaricides