Sarcoptes scabiei

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Sarcoptes scabiei
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Taxonomic classification

• Class Arachnida
• Sarcoptes scabiei (sarcoptic mange mite, itch
  mite)

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Host spectrum

• Domestic (sheep, goats, cattle, pigs, equids,
  dogs , rabbits) and wild animals, humans, other
  primates
• Each host is considered to have its own strain or
  variety, e.g. Sarcoptes scabiei var. equi and
  Sarcoptes scabiei var. hominis

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Geographic distribution

• Probably worldwide

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Morphology

• Adults - rounded body females 0.33-0.6 mm long
  and 0.25-0.4 mm wide, males 0.2-0.24 mm long,
  0.15-0.2 mm wide 8 short legs, posterior 2 pairs
  do not extend beyond the body margin unsegmented
  pedicels mouthparts have a rounded appearance.

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Sarcoptes scabiei, the scabies or itch mite
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Life cycle (stages)

• Female mites tunnel into the epidermis , lay 3-5
  eggs per day for a total of 40-50 eggs
• Six-legged larvae hatch from eggs
• Larvae and nymphs (proto- and deuto-) burrow into
  the stratum corneum and form pockets where they
  molt and feed
• Adult males and females develop and mate
• Life cycle requires 2-3 weeks to complete

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Site of infestation

• Skin (epidermis) females, eggs, larvae and
  nymphs in tunnels or pockets, males on the skin
  surface.

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Pathogenesis/clinical signs

• Initial lesions occur on the hand, elbows,
  axillary or inguinal regions
• Lesions are initially erythematous, then become
  papular papules rupture and skin becomes crusty
• Alopecia, thickening of the skin, pruritus
• Secondary bacterial infection, allergic reaction,
  self-mutilation may occur

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A severe case of scabies of the hand. 
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Crusted appearance on hands
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Treatment

• Lindane shampoo or dip, phosmet
  (ParamiteR), or Amitraz (MitabanR)
• ivermectin weekly for four weeks orally or
  subcutaneously

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Public health significance

• Humans may be infested with the strains from
  animals and these infestations may be mild to
  intensely pruritic, but they are self-limiting.