[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/) › Sarcoptes scabiei

[Microbiology](https://durgical.com/en/microbiology/) · [Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/)

# Sarcoptes scabiei

- Parasite
- Contact
- Exam priority: high

A tiny mite that burrows into the skin and causes intense itch, worse at night. It spreads by skin-to-skin contact and affects whole families.

Updated 2026-11-01

Also called: itch mite, scabies mite

## Key points

- Night-time itch with affected household members.
- Burrows in finger webs and wrists.
- Contact precautions; treat all contacts at once.
- Crusted scabies: highly contagious.
- Complication: impetigo and post-streptococcal glomerulonephritis.

## At a glance

**Shape**
Round, eyeless body with 4 pairs of short legs

**Family**
Sarcoptidae

**Type**
Mite (arthropod, arachnid), obligate ectoparasite

**Size**
Female 0.3–0.45 mm; male about half that size

## Morphology

- Female living in a serpiginous burrow in the stratum corneum.
- Oval eggs and faeces (scybala) inside the burrow, visible in scrapings.
- Larva with 3 pairs of legs; nymph and adult with 4 pairs.

## Transmission

- Prolonged skin-to-skin contact: household members, sexual partners, carers.
- Less often, shared bedding or clothing.
- In crusted scabies, with thousands of mites, clothing, beds and furniture also spread it.

**Reservoir:** Humans (animal varieties cause only transient infestation)

### Isolation precautions

What the care team adds to standard precautions.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

## Life cycle

- The fertilised female digs a serpiginous burrow in the stratum corneum and lays 2–3 eggs a day.
- Eggs hatch in 3–4 days; the six-legged larva comes to the surface.
- The larva digs short moulting pouches and becomes an eight-legged nymph.
- The nymph moults into an adult; males and females mate once on the skin.
- The female digs a permanent burrow and lays eggs for the rest of her life, 1–2 months.
- Spread happens when a fertilised female passes to another person by skin-to-skin contact.

## Virulence factors

- The itch is a hypersensitivity reaction to mites, eggs and faeces.
- With a first infestation symptoms take weeks to appear; with reinfestation, a few days.
- Scratching opens the way to impetigo by S. aureus and S. pyogenes, with a risk of post-streptococcal glomerulonephritis.
- In immunocompromised, elderly or institutionalised people, crusted scabies develops with thousands of mites.

## Diseases it causes

- Scabies [Scabies →](https://durgical.com/en/conditions/scabies/)
- Crusted (Norwegian) scabies in immunocompromised, elderly or institutionalised people

## Clinical picture

- Intense itch, worse at night, in several household members.
- Burrows and papules in finger webs, wrists, axillae, waist, genitals and areolae.
- In infants also palms, soles and scalp.
- Crusted scabies: thick crusts with little itch.

## Diagnosis

- Clinical diagnosis from lesion distribution, burrows and family itch.
- Scraping of a burrow with mineral oil: mites, eggs or scybala under the microscope.
- Extracting the mite from the end of the burrow with a needle.
- Dermoscopy: the mite seen at the end of the burrow.

## Treatment

Topical scabicides (permethrin, benzyl benzoate, sulphur ointment, malathion) or oral ivermectin; all contacts are treated at the same time. Crusted scabies needs combined therapy with keratolytics, and impetigo needs antibiotics.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Ivermectin](https://durgical.com/en/pharmacology/ivermectin/)

## Prevention

- Treat household members and close contacts at the same time.
- Hot-wash clothing and bedding used in the previous days, or seal them in a bag for several days.
- Contact precautions in hospitals and care homes.
- Mass ivermectin administration in high-prevalence communities.

## In Colombia

Common in children, crowded households, prisons, care homes and some Indigenous communities; institutional outbreaks are frequent.

## Memory aid

If it itches at night and itches the whole house, it's the mite: it digs by day and the itch arrives with the pillow.

## Test yourself

Think of the answer, then tap the question to see it.

## Which isolation precautions does a patient with scabies need?

Contact precautions, on top of standard precautions.

## Why are all household members treated at the same time?

To stop mites passing back to the person already treated and keeping the reinfestation going.

## Which form of scabies is highly contagious and seen in immunocompromised people?

Crusted (Norwegian) scabies, with thick crusts holding thousands of mites.

## Which kidney complication is linked to scabies?

Post-streptococcal glomerulonephritis after Streptococcus pyogenes impetigo.

## How is scabies confirmed in the laboratory?

With a burrow scraping showing mites, eggs or scybala under the microscope.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/sarcoptes-scabiei/)

## Related

- [Pediculus humanus and Pthirus pubis](https://durgical.com/en/microbiology/pediculus-humanus-and-pthirus-pubis/)
- [Tunga penetrans](https://durgical.com/en/microbiology/tunga-penetrans/)

## Related conditions

- [Scabies](https://durgical.com/en/conditions/scabies/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

**Droplet**
Surgical mask within about a metre; single room.

**Airborne**
N95 respirator and a negative-pressure room.

[← Back to the group: Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [CDC - DPDx - Scabies](https://www.cdc.gov/dpdx/scabies/index.html) (CDC, 2024); [Scabies](https://www.who.int/news-room/fact-sheets/detail/scabies) (WHO, 2023); [About Scabies | Scabies | CDC](https://www.cdc.gov/scabies/about/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/sarcoptes-scabiei/