Sarcoptes scabiei

Taxonomic classification

• Class Arachnida

• Sarcoptes scabiei (sarcoptic mange mite, itch mite)

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

Geographic distribution

• Probably worldwide

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.

Sarcoptes scabiei, the scabies or itch mite

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 in

to 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

Site of infestation

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

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 reactio

n, self-mutilation may occur

A severe case of scabies of the hand. 

Crusted appearance on hands

Treatment

Lindane shampoo or dip, phosmet (ParamiteR), or Amitraz (MitabanR)

• ivermectin weekly for four weeks orally or subcutaneously

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.