What is the life cycle of the S scabiei var hominis (scabies) mite?

Updated: Oct 13, 2020
  • Author: Megan Barry, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

The female S scabiei var hominis mite lays 60-90 eggs in her 30-day lifespan, although less than 10% of the eggs result in mature mites. The average patient is infected with 10-15 live adult female mites at any given time. Life cycle stages are as follows (see the images below) [6] :

  1. Eggs incubate and hatch in 3-4 days (90% of the hatched mites die)

  2. Larvae (3 pairs of legs) migrate to the skin surface and burrow into the intact stratum corneum to make short burrows, called molting pouches (3-4 days)

  3. Larvae molt into nymphs (4 pairs of legs), which molt once into larger nymphs before becoming adults

  4. Mating takes place once, and the female is fertile for the rest of her life; the male dies soon after mating

  5. The female makes a serpentine burrow using proteolytic enzymes to dissolve the stratum corneum of the epidermis, laying eggs in the process; she continues to lengthen her burrow and lay eggs for the rest of her life, surviving 1-2 months

  6. Transmission of impregnated females from person-to-person occurs through direct or indirect skin contact

In crusted scabies, sections show multiple mites ( In crusted scabies, sections show multiple mites (arrows) within the hyperkeratotic stratum corneum. The epidermis is spongiotic (hematoxylin and eosin; original magnification, 100X).
In routine scabies, a single mite is seen. Eosinop In routine scabies, a single mite is seen. Eosinophilic spongiosis may be present (hematoxylin and eosin; original magnification, 400X).

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