Sarcoptes scabiei.ppt

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 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

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 reaction, 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.