Scabies (mite)

Skin inflammatory (nontumor)
Infestations
Scabies (mite)

Author: Mowafak Hamodat, M.B.Ch.B., M.Sc.

Topic Completed: 1 July 2011

Revised: 3 September 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Scabies[TI] mite[TI]

See Also: Penis & scrotum chapter

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Table of Contents

Cite this page: Hamodat M. Scabies (mite). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumorscabies.html. Accessed October 14th, 2019.

Definition / general

Mite that produces burrows and extremely pruritic erythematous papules on interdigital skin, palms, wrists

Pathophysiology

Sarcoptes scabei spend their entire lifecycle on or in their human host (Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 531 [Accessed 29 August 2019])
- Female burrows into the outermost layer of the epidermis (the stratum corneum) to create a short burrow called a molting pouch
- Male penetrates this pouch and mates with the female
- Dispersed along the burrows are eggs, hatched larvae and excrements
Scabies mites generally do not survive > 2 - 3 days away from human skin (CDC: Scabies - Prevention & Control [Accessed 29 August 2019])
- Can survive longer in some cases (Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 531 [Accessed 29 August 2019])

Diagrams / tables

Images hosted on other servers:

Life cycle

Case reports

Elderly man with objects found in skin scrapings (Pritt: Creepy Dreadful Wonderful Parasites Blog - Case of the Week 531 [Accessed 29 August 2019])

Treatment

Topical permethrin (Can Fam Physician 2010;56:1005)

Microscopic (histologic) description

Burrow containing mite body parts appears as cleft in upper epidermis
Epidermis exhibitis acanthosis, parakeratosis, spongiosis, with dense eosinophilic dermal infiltrate
In the dermis, there is superficial perivascular and sometimes diffuse infiltrate of lymphocytes and histiocytes, sometimes accompaned by neutrophils and less often eosinophils
In nodular skin lesions, the dermal infiltrate may be very dense and atypical and hyperchromatic cells may be evident, in addition to histiocytes, plasma cells, eosinophils and lymphocytes
Mites (Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 531 [Accessed 29 August 2019]):
- Male mites range in size from 213 - 285 μm long by 162 - 240 μm wide
- Female mites range from 300 - 504 μm long to 230 - 420 μm wide
- Sarcoptes are round to ovoid when viewed from the back; when viewed from the side they are ventrally flattened and dorsally rounded (similar to a turtle)
- They possess short stumpy legs and have no internal or external respiration apparatus (stigmata or tracheae)
- Ventral surface contains a number of chitinized plates called apodemes, the dorsal surface is partially covered by wide angled, V shaped spines
- Cuticular surface is sculptured into numerous parallel ridges which superficially resemble human finger prints and the anus is at the posterior end of the mite
- The last segment (tarsus) of legs 1, 2 and 4 on males and legs 1 and 2 on females has a long, unjointed empodium or stalk with a small sucker-like pad at its end
  - These stalks are diagnostic for Sarcoptes