Psoroptes

• Causes psoroptic skin infestation

Recognition

• Oval shaped

• Long legs

• Funnel shaped suckers on segmented pedicels

• 1-2mm in length

Life cycle

• Confined to skin surface

• Feed on serous exudate by siphoning

• Adult female can lay up to 100 eggs during her life time (1 month)

• 10 day life cycle

• 2 nymphal stages

Psoroptes cuniculi

• Parasite of rabbits

• Common among conventional rabbits

• Transmitted via contact

• Adapted to living in an aural environment

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

Psoroptes ovis

• Adult females are large mites at 750μm in length

• Males identified by copulatory suckers and paired posterior lobes

• Males attach to deutonymphs (second moult after larval stage) in a process called copula
  • Males remain in copula until females moult for the last time
  • Copulation occurs

• Life cycle last 14 days

• Transmitted by direct contact between sheep

• Indirect transmission can also occur

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