- 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.
- Pubic lice is caused by Pthirus pubis
- Scabies is caused by Sarcoptes scabiei var hominis.
Pubic or genital itch (especially at night with scabies) &/or rash
Scabies: genital papulonodule
|Crabs: debris in underwear|
|Scabies:Complications uncommon and mostly in crusted scabies (institutionalised)
|Pubic lice: fever, lethargy, irritability (more common in the young and frail)|
See STI Atlas for more images.
- 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.
- Transmitted by close body contact
- Survive less than 24 hours off host
- Fomite transmission plays little role
- Not a vector for other diseases.
Crabs: direct visualisation +/- magnification of crab or nits (egg)
Adult lice infest strong hairs (pubic hair, eyebrows and eyelashes).
Scabies: usually a clinical diagnosis.
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).
- Usually a clinical diagnosis with or without the aid of a magnifying glass. Mite or egg attached to a hair can be removed from the patient and attached to glass slide with cellotape and viewed under a light microscope.
- Not generally available in general practice, seek specialist advice.
- Skin scrapings taken from burrows with a fine needle to reveal the mite after examination under light microscopy.
|Principal Treatment Options|
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.
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.
Apply permethrin 1% cream rinse to pubic and other hair infested with lice and wash off after 10 minutes.
|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.
- Avoid close body contact
- Patient and recent partner/s should complete treatment
- Apply cream at night, including finger webs and do not wash hands after applying cream
- Isolate clothes, towels and bed linen from previous 3 days and launder as usual the day after first treatment. Or simply isolate these items for >1 week while mites die
- Avoid more than 2 applications of treatment to prevent persistent irritation
- Symptoms/signs may not clear for 2 weeks
- Anti-pruritic treatments (antihistamine oral medication; calamine lotion and topical steroid creams e.g. hydrocortisone 1% can be helpful).
- Isolate clothes, towels and bed linen from previous 3 days and launder as usual the day after first treatment.
- Shaving pubic hair and/or removal of eggs is not required.
- Compared with head ice, resistance to permethrin treatment of pubic lice has not been demonstrated.
Other immediate management
Special treatment situations
Consider seeking specialist advice before treating any complicated or persisting presentation.
- Simultaneous treatment of sexual contacts/all household members of the past month.
- Simultaneous treatment of recent sexual contacts/all household members.
Review in 1 week provides an opportunity to:
- Confirm patient adherence with treatment and assess for symptom resolution
- Confirm contact tracing procedures have been undertaken or offer more contact tracing support
- Provide further sexual health education and prevention counselling.
Test of Cure (TOC)
Not required but provides an opportunity to consider testing for other STIs, if not undertaken at first presentation, or retesting post the window period.
If itch and rash persist, reassurance and anti-pruritics (as above) may be helpful.
- 100% of diagnoses of pubic lice and scabies are treated with permethrin 1% and 5% as first line therapy, respectively.
- 100% of patients diagnosed with pubic lice and scabies have STI and HIV testing.