Insects

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 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


Transmission: General
Highly contagiousClose contact often requiredGeneral life cycleFemales lay eggs on host or in environmentEgg hatches into larvaLarva  nymph  adultDirect contact with susceptible host Center for Food Security and Public Health, Iowa State University, 2012

Site of infestation

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

Human Scabies

Severe pruritus Especially at night Papular rash or nodules Burrows pathognomonic Secondary infections possible Norwegian scabies Severe form found in immunocompromised people
Center for Food Security and Public Health, Iowa State University, 2012

SIGNS and SYMPTOMSscabies rash

Classical sites of scabies rash... between fingers wrists auxiliary areas female breasts (particularly the skin of the nipples) the umbilical area penis and scrotum buttocks inside of legs ankles

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

Tissue section

Crusted appearance on hands


Diagnosis
Skin scraping ink test

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.