Transmission is via direct person-to-person contact
Pathophysiology
The fertilized, female mite tunnels into the superficial skin layer (stratum corneum), forming burrows in which she lays her eggs and deposits feces (scybala).
After 2 months, the female parasite dies on site.
Following a period of 3 weeks, the larvae mature into adult mites, maintaining the infestation cycle.
The excretions of the mites and their decomposing bodies contain antigens which cause an immunological response (see type IV hypersensitivity reaction), presenting as severe pruritus and excoriations.
Clinical features
Intense pruritus that increases at night
The name “scabies” comes from “scratch”
The warmth of the skin, especially under blankets and pajamas, can stimulate mite movement and activity, increasing pruritus.
Skin lesions
Burrows of 2–10 mm in length
Predilection sites
Wrists (flexor surface)
Medial aspect of fingers
Interdigital folds (hands and feet)
Male genitalia (e.g., scrotum, penis)
All other intertriginous areas of the skin (anterior axillary fold, buttocks)
