Ectoparasites

Signs and Symptoms

• Pubic or genital itch (especially at night with scabies)
• Rash

• Scabies: genital papulonodules with or without generalised itch

• Pubic lice: debris in underwear

Complications

Scabies: complications uncommon and mostly occur in crusted scabies

• Fever (children)
• Pain on movement
• Sleep disturbance
• Secondary bacterial infection

Pubic lice:

• Complications uncommon
• Fever, lethargy, irritability (more common in the young and frail)
• Secondary bacterial infection

Test

Considerations

Pubic lice:

Direct visualisation with or without magnification of crab or nits (egg)

Adult lice infest coarse hairs (pubic hair, eyebrows, eyelashes, chest, axillae)

Eggs (nits) are strongly attached to the hairs

Scabies:

Often a clinical diagnosis

If available dermatoscopy can be useful to identify burrows and mites

Other methods not usually practical in general practice.  Laboratory diagnosis by microscopy has very poor sensitivity, and is not usually recommended

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 and nipples)

Infection

Recommendation

Alternative treatment

Scabies

Apply permethrin 5% cream or lotion topically to dry skin from the scalp to soles of feet, paying particular attention to hands and genitalia. Avoid contact with eyes. Apply 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

On day of treatment environmental decontamination should be performed by hot washing bedding and clothing

Repeat treatment and washing in 1 week

Family members and close contacts should be examined and treated if necessary

Ivermectin 200 microgram/kg as a single dose

Repeat treatment in 7 days

Requires special authority, including discussion with dermatologist, infectious diseases (ID) physician or clinical microbiologist

Pubic lice

Apply permethrin 5% cream or lotion to all hairy parts of the body apart from the eyelids and scalp and wash off after 10 minutes

Repeat treatment in 7-10 days if live lice are still found

Ivermectin 250 microgram/kg as a single dose (unapproved indication/not funded)

Repeat treatment in 7 days

Situation

Recommendation

Complicated infection, e.g. crusted scabies

Occurs when mite population is very high due to poor host immune response. The patient may not be itchy

Consider HIV serology

Seek specialist advice for treatment (dermatology, ID or clinical microbiologist)

Persistent infection

Note it is common for itch to persist after scabies infestation for a few weeks after treatment (post scabietic itch)

Ongoing symptoms may be due to:

• Lack of thorough treatment application
• Lack of synchronising treatment with known close contacts leading to re-infection
• Resistance to treatment
• Development of irritant contact dermatitis due to topical scabicide

Seek specialist advice for treatment (dermatology, ID or clinical microbiologist)

Pregnancy and breastfeeding

Permethrin is safe in pregnancy and during breastfeeding

Infants

Seek specialist advice

Allergy or contraindications

Seek specialist advice for treatment (dermatology, ID or clinical microbiologist)

Eyelash infestation

Permethrin should not be applied near the eyes. Lice and nits can be removed by using a pair of fine forceps. Alternatively, petroleum jelly can be smeared on the eyelashes twice daily for at least 3 weeks. This suffocates the lice and their nits

Follow Up:

• Not required unless symptoms persist or recur

Test of cure:

• Not required

Retesting:

• Consider testing for other sexually transmitted infections (STIs), if not undertaken at first presentation, or retesting after the window period