Ectoparasites

Pubic lice | Genital scabies | Crabs | Mites |

Overview

  • The most common genital and pubic ectoparasites infestations are scabies and pubic lice (Pediculosis pubis or crabs).
  • Scabies is associated with crowded living/sleeping conditions and institutional outbreaks have been reported.
  • Pubic lice is found typically in sexually active young people.

Cause

Clinical presentation

Symptoms

Pubic or genital itch (especially at night with scabies) &/or rash

Scabies: genital papulonodule

Crabs: debris in underwear
Complications
Scabies:Complications uncommon and mostly in crusted scabies (institutionalised)
  • Fever (children)
  • Pain on movement
  • Sleep disturbance
  • Secondary infection
Pubic lice: fever, lethargy, irritability (more common in the young and frail)

See STI Atlas for more images.

Scabies:

scabies

Pubic lice:

pubic lice

Special considerations

Scabies:

  • Clinical signs are due to allergy to bites (?blood feeds) by the mite
  • Close, prolonged (15-20min) skin contact, person-person transmission
  • Fomite transmission possible
  • May survive >3 days off host in tropics but <36hrs usually.

Pubic lice:

  • Transmitted by close body contact
  • Survive less than 24 hours off host
  • Fomite transmission plays little role
  • Not a vector for other diseases.

Diagnosis

TestSite/Specimen

Crabs: direct visualisation +/- magnification of crab or nits (egg)

Adult lice infest strong hairs (pubic hair, eyebrows and eyelashes).

Eggs (nits) are strongly attached to the hairs.

Scabies: usually a clinical diagnosis.

Multiple methods requiring moderate degree of skill and equipment. Not usually practical in General Practice.

Characteristic nodule and silvery skin burrows sometimes seen e.g. nodule on glans penis and scrotum concurrently, labial fold nodule, burrows (inter-digital folds, wrists and elbows, around breast nipples in women).

Investigations

Crabs:

Scabies: 

Specimen collection 

Scabies:

Management

Principal Treatment Options
SituationRecommendedAlternative
Scabies

Apply permethrin cream 5% topically to dry skin from the neck down, paying particular attention to hands and genitalia, and under the nails with a nailbrush. Leave on the skin for a minimum of 8 hours (usually overnight) and reapply to hands if they are washed.

The time may be increased to 24 hours if there has been a treatment failure. Repeat treatment in 1 week to improve success rate.

Apply benzyl benzoate 25% emulsion topically to dry skin from the neck down, paying particular attention to hands and genitalia, and under the nails with a nailbrush. Leave on for 24 hours and reapply to hands if they are washed.

Repeat treatment in 7 days.

Pubic lice

Apply permethrin 1% cream rinse to pubic and other hair infested with lice and wash off after 10 minutes.

Repeat treatment in 1 week

Bioallethrin with piperonyl butoxide.

Crusted scabies (formerly called Norwegian scabies) occurs when the mite population is very high due to poor host immune response, such as people with HIV infection, and also in remote Indigenous communities. Seek specialist advice for treatment.

Treatment advice

Scabies:

Pubic lice:

Other immediate management

Special treatment situations

Special considerations

Consider seeking specialist advice before treating any complicated or persisting presentation.

SituationRecommended
Complicated or disseminated infection

For less severe crusted scabies, use ivermectin 200mcg/kg PO, on day 1, and second dose between day 8-14.

An additional dose maybe required for moderate–severe scabies, but seek specialist advice.

If secondary bacterial infection (impetigo) is severe, pre-treat with antibiotics to cover S. aureus and/or S. pyogenes before administering anti-scabetic treatment.

Persistent infection

Ivermectin 200mcg/kg PO, on days 1 and 8-14, not before 4 weeks after failure of both topical Permethrin and Benzyl Benzoate.

Pregnant women 
 pregnancy
Permethrin is safe in pregnancy and during breast feeding.
Allergy to principal treatment choice

Seek specialist advice.

Regional/Remote

No special differences. Scabies may affect entire small remote communities where a whole community treatment regimen may be required. Seek local advice.

Eye lash infestation Permethrin 1% lotion keeping the eyes closed during the 10 min application.
Ophthalmic-grade petrolatum ointment bd 10 days (prescription needed and compounding pharmacist to make).

Contact tracing

Scabies:

Pubic lice:

Follow up

Review in 1 week provides an opportunity to:

Test of Cure (TOC)

Not required.

Retesting

Not required but provides an opportunity to consider testing for other STIs, if not undertaken at first presentation, or retesting post the window period.

Special considerations

If itch and rash persist, reassurance and anti-pruritics (as above) may be helpful.

Auditable outcomes

Last Updated: Wednesday, 11 July 2018