Clinical Topic A-Z Clinical Speciality

Pubic lice

Pubic lice
D010373Lice Infestations
D020061Phthirus
Infections and infestationsSexual healthSkin and nail
2011-12-01Last revised in December 2011

Pubic lice - Summary

Pubic lice infestation is caused by the louse Phthirus pubis.

Pubic lice are blood-sucking insects, and are obligate parasites of humans.

Pubic lice are transmitted by close body contact, which can be from sexual contact or from close family contact. Children with pubic lice infestation are usually thought to have acquired this innocently, but the possibility of sexual abuse should be considered.

Pubic lice are probably not transmitted via clothing, bed linen, towels, or toilet seats (but some experts disagree with this view).

The complications of pubic lice infestation include:

Excoriation and skin infection (e.g. impetigo or furunculosis) caused by scratching.

Blepharitis, conjunctivitis, or corneal epithelial keratitis when pubic lice infestation involves the eyelashes.

Itchy red papules are the most common presenting complaint, and this is due to hypersensitivity. Itching takes 1–3 weeks to develop after the first infestation, but may occur immediately following reinfestation. Itching is worse at night.

The diagnosis is confirmed by finding adult lice and/or viable eggs.

Pubic lice may be found in any coarse hair, such as moustaches, beards, axillary hair, hair on the chest, abdomen, or back, as well as pubic and perianal hair.

The eyebrows and eyelashes can also be affected.

Pubic lice can also be found around the scalp margins. Lice are most likely to be found when the hair shafts are widely spaced.

Blue macules are occasionally visible at feeding sites, particularly on the thighs and lower abdomen.

Scatterings of minute dark-brown specks (louse excreta) are sometimes seen on the skin and underwear.

People presenting with suspected or confirmed pubic lice infestation acquired via sexual contact should be referred to a genito-urinary medicine (GUM) clinic for treatment, screening for other sexually transmitted infections, contact tracing, and follow-up.

If an appointment at the GUM clinic is not possible, screening for chlamydia and other sexually transmitted infections should be arranged. Follow-up in a GUM clinic should be considered in about a week.

People with pubic lice (including those who have not acquired pubic lice by sexual contact) should:

Be treated with a topical insecticide.

Avoid close body contact until they, and their current partner (if relevant), have been treated.

If relevant, inform their partner(s) of the previous 3 months that they should be examined for pubic lice and treated if infested.

Infestation of the eye lashes should be treated with an occlusive ophthalmic ointment or a topical insecticide.

Follow up should be arranged for about 7 days after treatment.

If pubic lice infestation is unresponsive to initial insecticide treatment, treatment failure may be due to inadequate application technique, insecticide resistance, or reinfestation. If insecticide resistance is suspected, a different class of insecticide should be used.

Have I got the right topic?

6months3060monthsBoth

This CKS topic covers the management of pubic lice infestation.

There are separate CKS topics on Head lice and Scabies.

The target audience for this CKS topic is healthcare professionals working within the NHS in the UK, and providing first contact or primary health care.

How up-to-date is this topic?

How up-to-date is this topic?

Changes

Last revised in December 2011

November 2011 — reviewed. A literature search was conducted in October 2011 to identify evidence-based guidelines, UK policy, systematic reviews, and key RCTs published since the last revision of the topic. This identified the United Kingdom National Guideline in the Management of Phthirus pubis infestation (2007) produced by the British Association of Sexual Health and HIV [BASHH, 2007]. Recommendations within this guideline are consistent with the current CKS topic therefore no changes to recommendations have been made. Issued in December 2011.

Previous changes

March 2011 — topic structure revised to ensure consistency across CKS topics — no changes to clinical recommendations have been made.

November 2007 — minor update to text. Malathion is now licensed for a second application after 7 days. (The recommendation for a second application of insecticide 7 days after the first is unlicensed for permethrin, and is different to the information supplied by the manufacturers: their package inserts state that a single application is sufficient.) Issued in December 2007.

February to May 2007 — converted from CKS guidance to CKS topic structure. The evidence-base has been reviewed in detail, and recommendations are more clearly justified and transparently linked to the supporting evidence.

There are no major changes to the recommendations.

August 2003 — reviewed. Validated in December 2003 and issued in February 2004.

November 2000 — rewritten. Validated in March 2001 and issued in June 2001.

June 1998 — reviewed.

September 1997 — written.

Update

New evidence

Evidence-based guidelines

No evidence-based guidelines since 1 October 2011.

HTAs (Health Technology Assessments)

No new HTAs since 1 October 2011.

Economic appraisals

No new economic appraisals relevant to England since 1 October 2011.

Systematic reviews and meta-analyses

No new systematic review or meta-analysis since 1 October 2011.

Primary evidence

No new randomized controlled trials published in the major journals since 1 October 2011.

New policies

No new national policies or guidelines since 1 October 2011.

New safety alerts

No new safety alerts since 1 October 2011.

Changes in product availability

No changes in product availability since 1 October 2011.

Goals and outcome measures

Goals

To support primary health care professionals:

To eradicate live pubic lice and viable eggs

To alleviate symptoms associated with pubic lice infestation

To prevent transmission of pubic lice to others

To detect and manage coexisting sexually transmitted infections in the person and their partner(s)

Background information

Cause

What causes pubic lice infestation?

Pubic lice infestation is caused by the louse Phthirus pubis.

The pubic louse is also called the crab louse because of its appearance under the microscope: the second and third pairs of legs have crab-like claws adapted for grasping hair.

Pubic lice infestation is colloquially known as crabs; in the medical literature it is sometime called pediculosis pubis.

Pubic lice are blood-sucking insects, and are obligate parasites of humans (i.e. they do not usually live on other animals). They live on coarse hair, notably in the pubic and perianal areas, but can also be found on the eyelashes, abdomen, back, in the axillae, and on the head.

The pubic louse is grey-brown in colour and about 2 mm long (smaller than a match-head).

The female lays eggs (smaller than a pinhead) on the hair shaft, near to the body. The eggs hatch about 6–10 days after laying. The empty eggshells (nits) are tightly attached to the hair and cannot be brushed off.

The female louse lays up to 300 eggs during her lifetime of 1–3 months.

[Ibarra, 1998; Chosidow, 2000]

Prevalence

How common is infestation with pubic lice?

The incidence and prevalence of pubic lice infestation in the general population has not been documented, but, as with other sexually transmitted infections, it is found most commonly in young adults [Gratz, 1997; Ibarra, 1998].

In UK genito-urinary medicine (GUM) clinics, the numbers of reported diagnoses of scabies and/or pubic lice has been falling steadily, from 6446 in 1996, to 2561 in 2005 [HPA, 2006].

Transmission of pubic lice

How are pubic lice transmitted?

Pubic lice are transmitted by close body contact, which can be from sexual contact or from close family contact (e.g. from an infested beard or chest hair). Children with pubic lice infestation are usually thought to have acquired this innocently, but the possibility of sexual abuse should be considered [Chosidow, 2000].

Pubic lice are probably not transmitted via clothing, bed linen, towels, or toilet seats (but some experts disagree with this view [Chosidow, 2000]).

Some experts suggest bedding and clothes can be decontaminated by ordinary laundering [Scott, 2001; Wendel and Rompalo, 2002].

[Ibarra, 1998; Wendel and Rompalo, 2002; Flinders and De Schweinitz, 2004]

Complications

What are the complications of pubic lice infestation?

The complications of pubic lice infestation include:

Excoriation and skin infection (e.g. impetigo or furunculosis) caused by scratching.

Blepharitis, conjunctivitis, or corneal epithelial keratitis when pubic lice infestation involves the eyelashes [Lin et al, 2002; Manjunatha et al, 2006].

Prognosis

What is the prognosis of pubic lice infestation?

No studies of the natural history of pubic lice infestation could be found. However, cure is unlikely unless it is treated.

Diagnosis

Diagnosis of pubic lice

Diagnosis

How do I know my patient has it?

Itchy red papules are the most common presenting complaint, and this is due to hypersensitivity. Itching takes 1–3 weeks to develop after the first infestation, but may occur immediately following reinfestation. Itching is worse at night.

The diagnosis is confirmed by finding adult lice and/or viable eggs.

Pubic lice may be found in any coarse hair, such as moustaches, beards, axillary hair, hair on the chest, abdomen, or back, as well as pubic and perianal hair. Therefore, all hairy parts of the body should be examined.

The eyebrows and eyelashes can also be affected.

Pubic lice can also be found around the scalp margins. Lice are most likely to be found when the hair shafts are widely spaced.

The technique of detection combing using a fine toothed comb (as used to check for head lice infestation) has been suggested to be useful. See the CKS topic on Head lice for more information.

Blue macules (maculae caerulae) are occasionally visible at feeding sites, particularly on the thighs and lower abdomen.

Scatterings of minute dark-brown specks (louse excreta) are sometimes seen on the skin and underwear.

Basis for recommendation

Basis for recommendation

Recommendations for the diagnosis of pubic lice are based on expert opinion from text books [Ibarra, 1998; Burns, 2004] and review articles [Scott, 2001; Wendel and Rompalo, 2002].

Differential diagnosis

What else might it be?

Nits may be confused with:

Seborrhoeic scales, small crusts of scratched dermatitis, or hair muffs (secretions from the hair follicle that are wrapped round the hair shaft) — these can all be brushed off, in contrast to nits which are firmly glued to the hair.

Pubic lice may be confused with:

Clothing lice (Pediculus humanus), which are slightly larger than pubic lice, and are found only on clothes, not on body hairs.

Head lice (Pediculus capitis), which are slightly larger than pubic lice, and are found only on the scalp. For more information, see the CKS topic on Head lice.

Itchy red papules caused by pubic lice may be confused with:

Scabies (Sarcoptes scabiei var humanus), which causes an itch that may be similar to that resulting from public lice infestation. Scabies can colonise the same areas as pubic lice (e.g. axillae, male genitalia), but it is also found in areas where pubic lice are unlikely to be found (e.g. the interdigital web spaces of the hands, flexor surface of the wrists and elbows, and women's breasts). Scabies and pubic lice are often found together. For more information see the CKS topic on Scabies.

Basis for recommendation

Basis for recommendation

Information on the differential diagnosis of pubic lice is based on expert opinion from review articles [Chosidow, 2000; Flinders and De Schweinitz, 2004].

Management

Management

Scenario: Management : covers the management and treatment of people presenting with pubic lice infestation, including people who have failed to respond to an initial course of insecticide treatment.

Scenario: Management

Scenario: Management of pubic lice

6months3060monthsBoth

Overview of management

How is pubic lice infestation managed in primary care?

Review the individual and consider whether the pubic lice infestation has been acquired via sexual or non-sexual contact.

For adults and adolescents presenting with suspected or confirmed pubic lice infestation acquired via sexual contact:

Refer the individual to a genito-urinary medicine (GUM) clinic for treatment, screening for other sexually transmitted infections, and contact tracing.

If an appointment is not possible:

Screen the individual for Chlamydia and other sexually transmitted infections as appropriate.

Treat the individual with a topical insecticide: two applications of malathion 0.5% aqueous lotion or permethrin 5% dermal cream, 7 days apart.

Consider follow-up in a GUM clinic in about a week to screen for sexually transmitted infections.

Advise the individual to avoid close body contact until they, and their current partner, have been treated.

Recommend that the person informs their partners of the previous 3 months that they should be examined for pubic lice and treated if infested.

For children and other individuals who have acquired pubic lice infestation via non-sexual contact:

Treat the individual with an insecticide: two applications of malathion 0.5% aqueous lotion or permethrin 5% dermal cream, 7 days apart.

Advise the individual to avoid intimate body contact with others until the infestation has been treated.

Recommend that close contacts over the past 3 months be informed that they should be examined for pubic lice.

Although children usually acquire the infestation via non-sexual contact, consider the possibility of sexual abuse.

For people with infestation of the eye lashes:

Treat the eyelashes with an occlusive ophthalmic ointment or a topical insecticide.

Follow up about 7 days after treatment.

For pubic lice infestation unresponsive to initial insecticide treatment and acquired via sexual contact:

If the person has not yet been referred, refer them to a GUM clinic for confirmation of infestation, for treatment, and for screening for other sexually transmitted infections and contact tracing.

If treatment has been initiated by the GUM, refer the individual back to the GUM clinic for further investigation and treatment.

If referral is not possible, review treatment as for those with non-sexually acquired infestation (see below).

For pubic lice infestation unresponsive to initial insecticide treatment and NOT acquired via sexual contact:

If inadequate technique seems probable:

Review the treatment strategy with the individual.

Consider repeating the previous treatment with the correct technique (rather than switching to a different treatment).

If insecticide resistance is suspected:

Switch to a different class of insecticide, i.e. switch between malathion and permethrin.

If reinfestation seems likely:

Consider repeating the previous treatment (rather than switching to a different treatment).

Assess all close contacts for pubic lice and treat all positive cases simultaneously.

Basis for recommendation

Basis for recommendation

The basis for each recommendation is discussed in the specific management section.

Managing pubic lice infestation

How should I manage someone presenting with pubic lice infestation?

Consider if the pubic lice infestation has been acquired via sexual or non-sexual contact.

For adults and adolescents presenting with suspected or confirmed pubic lice infestation acquired via sexual contact:

Refer to a genito-urinary medicine (GUM) clinic for treatment, screening for other sexually transmitted infections (STIs), and contact tracing.

If an appointment at a GUM clinic is not possible:

Screen for Chlamydia and other STIs as appropriate.

Treat with an insecticide.

Consider follow-up in a GUM clinic in about a week to perform a full STI screen.

Advise to avoid close body contact until they and their current partner have been treated.

Recommend that the person informs their partners of the previous 3 months that they should be examined for pubic lice, and treated if necessary.

For children and individuals who have acquired pubic lice infestation via non-sexual contact:

Treat with an insecticide. Repeat after 7 days.

Advise to avoid close body contact with others until the infestation has been treated.

Encourage the person to inform close contacts of the past 3 months that they should also be examined for pubic lice.

Although children usually acquire the infestation via non-sexual contact, consider the possibility of sexual abuse.

Consider symptomatic treatment for itching.

Basis for recommendation

Basis for recommendation

The recommendations for managing pubic lice infestation acquired via sexual contacts are based on those published by the Royal College of General Practitioners (Sex, Drugs, and HIV Task Group) and the British Association for Sexual Health and HIV [RCGP and BASHH, 2006].

Transmission of pubic lice infestation requires close body contact and infestation is often regarded as a sexually transmitted disease [Gratz, 1997; Ibarra, 1998; Scott, 2001; CDC, 2006; RCGP and BASHH, 2006].

Referral to a GUM clinic is recommended as the expertise and resources for treatment, contact tracing, and screening for other sexual transmitted diseases are available.

For those infestations acquired via non-sexual contact, the recommendations for managing these individuals (including children) are extrapolated from the above and other published guidelines and expert opinion [Gratz, 1997; Ibarra, 1998; Scott, 2001; BNF 52, 2006; CDC, 2006; RCGP and BASHH, 2006].

For further information on treating pruritus (itching) associated with pubic lice infestation, see section on Large local reactions to bite or sting in the CKS topic on Insect bites and stings.

Infestation involving the eye lashes

How should I manage pubic lice infestation involving the eye lashes?

Treat pubic lice infestation of the eye lashes with either inert occlusive ophthalmic ointment (e.g. Simple eye ointment BP) or a topical insecticide (a cream rinse or shampoo should be used).

The choice between occlusive ointment and insecticide depends on individual preference and treatment history.

People might prefer treatment with an insecticide to treatment with an ointment because only two applications are required, or because they find it cosmetically more attractive.

However, some people might be reluctant to apply an insecticide near their eyes and prefer treatment with an ointment as a safer option.

An inert occlusive ophthalmic ointment is preferred for people under the age of 18 years, and for those who are pregnant or breastfeeding.

Removal of nits (empty shells) from the eyelashes is unnecessary.

Treat the eyelashes and the rest of the body at the same time to ensure complete eradication of pubic lice.

Additional information

Additional information

The choice between occlusive ointment and insecticide depends on individual preference and treatment history.

People might prefer treatment with an insecticide to treatment with an ointment because only two applications are required, or because they find it cosmetically more attractive.

However, some people might be reluctant to apply an insecticide near their eyes and prefer treatment with an ointment as a safer option.

For individuals under 18 and for women who are pregnant or breastfeeding, occlusive ointments are preferred over insecticides because:

This treatment removes the risk of absorption of insecticides.

With small children it is easy to smear the ointment across the eyelashes and it does not matter if the ointment also gets onto the eyes, but it is difficult to confine application of insecticide to the eyelashes.

Although they might not be cosmetically attractive, the presence of nits does not indicate active infestation if treatment has been successful in eradicating all live lice.

It has been suggested that nits do not need to be removed: they are eliminated fairly quickly as the lashes they are attached to fall and regrow [Ibarra, 1998].

Given that lice eggs are firmly attached to the hair, their removal using forceps is likely to be difficult and painful.

Basis for recommendation

Basis for recommendation

There are no clinical trials of treatments for pubic lice infestation of the eyelashes, thus the recommendations are based on expert opinion [Ibarra, 1998; Scott, 2001; CDC, 2006; RCGP and BASHH, 2006] and case reports [Rundle and Hughes, 1993; Manjunatha et al, 2006].

The individual should be treated for suspected pubic lice infestation across the whole body as it is unlikely that the infestation is isolated to the eyelashes.

Inert ophthalmic ointments and insecticides are not licensed for treating pubic lice infestation of the eyelashes but are commonly used for this purpose.

Treatment of children and women who are pregnant or breastfeeding

For individuals under 18 and for women who are pregnant or breastfeeding, occlusive ointments are preferred over insecticides because:

This treatment removes the risk of absorption of insecticides.

With small children it is easy to smear the ointment across the eyelashes and it does not matter if the ointment also gets onto the eyes, but it is difficult to confine application of insecticide to the eyelashes.

Presence of nits

Although they might not be cosmetically attractive, the presence of nits does not indicate active infestation if treatment has been successful in eradicating all live lice.

It has been suggested that nits do not need to be removed: they are eliminated fairly quickly as the lashes they are attached to fall and regrow [Ibarra, 1998].

Given that lice eggs are firmly attached to the hair, their removal using forceps is likely to be difficult and painful.

Treatment

Which insecticide preparation should I prescribe for pubic lice infestation?

Prescribe:

Malathion 0.5% aqueous lotion, or

Permethrin 5% dermal cream

The choice primarily depends on a response to previous treatment, patient's age and if the person is a pregnant, or breastfeeding woman.

If appropriate treatment with one insecticide has not been successful, switch to a different class of insecticide (i.e. switch between malathion and permethrin rather than trying a different preparation containing the same class of insecticide).

Malathion is suitable for everyone — unless treatment with it has been unsuccessful.

Permethrin is suitable for individuals over the age of 18 years — unless they are pregnant, or breastfeeding, or treatment with it has been unsuccessful. It may be considered for people who are under the age of 18 years, or pregnant, or breastfeeding if malathion is ineffective or unsuitable.

Carbaryl should not be considered — unless resistance to both malathion and pyrethroid insecticides (permethrin or phenothrin) is suspected.

Aqueous preparations and dermal cream are preferred over alcoholic preparations.

Insecticides should not be used more than once a week, and should not be used for more than three consecutive weeks.

Basis for recommendation

Basis for recommendation

Because there is only limited evidence from three small clinical trials that insecticides can be effective treatments for pubic lice, the recommended strategy for management is based mainly on knowledge of the pubic louse's life cycle [Burgess et al, 1983; Burns, 2004] and the opinion of experts [Gratz, 1997; Ibarra, 1998; Scott, 2001; BNF 52, 2006; CDC, 2006; RCGP and BASHH, 2006].

There is no evidence from clinical trials to support a preference for one agent over another on the basis of effectiveness. In addition, no published data could be found regarding the incidence and level of resistance in pubic lice towards the different insecticides available in the UK.

Malathion and permethrin have been recommended based on the following considerations:

Malathion 0.5% aqueous lotion

This aqueous-based product is licensed for the treatment of pubic lice in people aged 6 months onwards [ABPI Medicines Compendium, 2006].

Malathion is preferred when treating people who are pregnant or breastfeeding because of concerns that the other insecticides have less evidence on possible adverse effects [NTIS, 1999; NTIS, Personal Communication, 2006].

Permethrin

Permethrin is offered along with malathion as it belongs to a different class of insecticide (a pyrethoid) to malathion (an organophosphate). This is to eradicate pubic lice that might have become resistant to a particular class of insecticide.

Permethrin is preferred for those who are pregnant or breastfeeding when malathion has been found to be ineffective.

Evidence, expert opinion and manufacturer's recommendation indicate this product to be safe in these people [BASHH, 2001; ATTRACT, 2004; ABPI Medicines Compendium, 2005; CDC, 2006].

Permethrin 5% dermal cream could be considered for children under 18 years if resistance to malathion is encountered.

This is an unlicensed indication as the product is not licensed for treating pubic lice in those under 18 years of age [ABPI Medicines Compendium, 2005]. However, this is a pragmatic recommendation as the product is licensed for treating scabies in those aged 2 months and over.

As a dermal cream, permethrin offers a formulation advantage for people who might find it difficult or uncomfortable to apply malathion aqueous lotion.

Carbaryl

As for the treatment of head lice, carbaryl should only be used to treat pubic lice infestation if resistance to both malathion and permethrin is encountered.

Carbaryl belongs to a different class of insecticide (a carbamate) to malathion (an organophosphate) and permethrin (a pyrethroid).

Carbaryl is not licensed for the treatment of pubic lice.

Carbaryl became a prescription-only medicine following reports of carcinogenicity in rodents subjected to continuous exposure [CMO, 1995]. The Committee on the Safety of Medicines (CSM) concluded that the risk is theoretical, and there are no reports of tumours in association with carbaryl use in humans.

Phenothrin

This alcohol-based preparation is licensed for use in adults and children from 6 months onward with pubic lice, but alcoholic preparations are not recommended (see below).

Phenothrin should not be used if permethrin proves ineffective (or vice versa) as they both belong to the same class of insecticides (both pyrethoids).

Alcoholic preparations

Alcoholic preparations are not recommended because:

Alcoholic formulations can irritate excoriated skin and the genitalia.

Alcoholic preparations can cause wheezing or irritate the skin, particularly in small children and people with asthma, eczema, or broken skin.

Some people dislike the smell of alcohol.

Alcoholic formulations are flammable and can pose a health hazard when used near a naked flame or heat source.

Treatments not recommended

What treatments are not recommended?

The following treatments are not recommended for the eradication of pubic lice:

Non-insecticidal treatments (other than occlusive ointments used to treat pubic lice infestation of the eyelashes)

Ivermectin

Wet combing using a fine toothed comb (such as those used for head lice)

Physical removal of pubic lice from eyelashes using forceps

Basis for recommendation

Basis for recommendation

Non-insecticidal treatments

Apart from the use of occlusive ointments for treating infestation of the eyelashes, non-insecticidal treatments are not recommended as there is no evidence to support their effectiveness.

Ivermectin

Ivermectin, an anti-parasitic drug taken orally, has been used to treat pubic lice. It is not recommended as it has only been evaluated in a few small studies [CDC, 2006]. In the UK, ivermectin is available on a named-patient basis [BNF 52, 2006].

Wet combing

Wet combing is not recommended as a method to treat pubic lice.

Although wet combing (as used in the treatment of head lice) has been advocated as a possible treatment option for pubic lice infestation [Ibarra, 1998], there are no trial data to support its use.

In addition, the technique may be poorly tolerated by patients: it is labour-intensive when covering all areas of the body and requires assistance from another individual.

Physical removal of pubic lice

Physical removal of pubic lice from the eyelashes using forceps is not recommended because:

Removal of lice using forceps requires considerable dexterity and care. There is a risk of injuring the eyes while extracting lice situated close to the roots of the eyelashes.

Because of their size, the nymphs and adult lice can be easily missed.

The procedure is likely to require assistance from another individual.

In addition, the technique might be impractical for some people (e.g. when performed on children unable to remain still).

How to apply

How should insecticide preparations be applied when treating pubic lice?

Apply the insecticide twice with applications one week apart.

Advise the person that the insecticide preparation should be applied to the whole body, paying particular attention to hairy areas, but that they should avoid getting it in the eyes.

When applying the insecticide to the whole body:

This includes the scalp, neck, ears and face.

Pay particular attention to the eyebrows and, if present, the beard and moustache.

Ensure sufficient product is applied to cover the pubic region, peri-anal region (around the anus), inner thighs down to the knees, and any hair that grows up from the pubic area to the chest/stomach.

Minimize contact with the eyes. If the product is accidentally introduced into the eyes, rinse immediately with plenty of water and reassure the person that this brief contact will not cause problems.

With malathion 0.5% aqueous lotion:

Leave on for 12 hours or overnight before washing.

With permethrin 5% dermal cream:

Leave on the skin for 24 hours before washing.

The cream should be applied to clean, dry, cool skin to reduce absorption through the skin.

When rubbed gently into the skin, the appearance of the cream will disappear. Consequently, there is no need to continue to apply cream to the skin until it remains detectable on the surface.

Basis for recommendation

Basis for recommendation

Applying insecticide

This recommendation for two applications, 7 days apart, is based on expert opinion [BASHH, 2001; BNF 52, 2006; RCGP and BASHH, 2006].

It is a pragmatic and unlicensed approach, intended to eliminate lice hatching from eggs that survive the first application of insecticide.

No insecticide has been shown to be 100% effective in killing head lice and eggs after one application. There is a lack of clinical trials evidence for pubic lice infestation but it is assumed to be similar.

This is an unlicensed use of permethrin, and is different to the packaging information which states that a single application is sufficient. Malathion is now licensed as a course of two applications of insecticide 7 days apart [ABPI Medicines Compendium, 2007].

Insecticides should be used not more than once a week, and should be used for not more than three consecutive weeks [BNF 52, 2006].

Contact time

Malathion: a contact time of 12 hours is recommended based on expert opinion [BNF 52, 2006; RCGP and BASHH, 2006].

Permethrin: a contact time of 24 hours is based on manufacturer's recommendation [ABPI Medicines Compendium, 2005].

Applying aqueous-based preparations and dermal cream formulation

The recommendations for applying aqueous-based preparations and dermal cream formulation are based on manufacturers' recommendations [ABPI Medicines Compendium, 2005; ABPI Medicines Compendium, 2006] and expert opinion [BNF 52, 2006; RCGP and BASHH, 2006].

The aim is to ensure that these products are applied correctly and no pockets of the infestation have escaped treatment.

Application to the head (apart from eye brows, moustache and beard) is an unlicensed indication when insecticides are used to treat pubic lice.

Follow up

How should I follow up someone treated for pubic lice?

Follow up after about 7 days to assess if treatment has been successful.

Treatment is successful if no adult lice or nymphs are found 7 or more days after completion of treatment.

Inspect all hairy areas for pubic lice.

To be sure that pubic lice have been eradicated, all hairy areas need to be inspected and confirmed to be free of lice. Pay particular attention to:

The pubic region, peri-anal region (around the anus), inner thighs down to the knees, and any hair on the trunk (abdomen, chest, back)

Facial hair (e.g. moustache and beard)

Eyebrows and eyelashes

The technique of detection combing using a fine toothed comb (as used to check for head lice infestation) has been suggested to be useful. For more information, see the CKS topic on Head lice.

Treatment is successful if no adult lice or nymphs are found 7 or more days after completion of treatment.

Nits (non-viable eggs) may remain adherent to hairs. This does not imply treatment failure, since the presence of nits does not indicate active infestation with live pubic lice (see Diagnosis).

Basis for recommendation

Basis for recommendation

A follow-up inspection is necessary to assess if treatment has been successful in eradicating pubic lice infestation.

It is important to identify treatment failure to prevent the person from infesting or re-infesting other close contacts.

The risk of treatment failure should be borne in mind: there is limited evidence regarding the efficacy of pubic lice treatments, and resistance of pubic lice to pyrethrins has been documented [Speare and Koehler, 2001].

Based on clinical experience that no treatment is 100% effective against head lice (e.g. due to incorrect application technique, non-adherence to treatment, or insecticide resistance), it is reasonable to assume that treatment failure can occur with pubic lice treatments.

It is pragmatic to check the individual 7 days after the completion of treatment to detect newly hatched pubic lice, because louse eggs take 6–10 days to hatch and treatments may not kill 100% of louse eggs.

Unresponsive to treatment

How should I manage someone with pubic lice unresponsive to treatment?

For pubic lice infestation unresponsive to initial insecticide treatment and acquired via sexual contact:

If the person has not yet been referred, refer them to a genito-urinary medicine (GUM) clinic for confirmation of infestation, treatment, screening for other sexually transmitted infections, and contact tracing.

If treatment has been initiated at a GUM, refer the individual back to the GUM clinic for further investigation and treatment.

If referral is not possible, manage as for those with non-sexually acquired infestation (see below).

For pubic lice infestation unresponsive to initial insecticide treatment and acquired via non-sexual contact:

Consider whether treatment failure is due to inadequate application technique, insecticide resistance, or reinfestation:

Treatment failure due to inadequate application technique can be identified by checking how the treatment was applied by the individual (and/or carer).

Resistance to insecticide is likely when treatment has no effect on the infestation and the health professional is certain that the treatment has been correctly applied.

Reinfestation should be suspected if pubic lice reappeared after successful eradication. Check if other contacts were examined or treated for pubic lice.

If inadequate application technique seems probable:

Review the treatment strategy with the individual (e.g. application method, amount of insecticide used, contact time).

Consider repeating the previous treatment with the correct technique (rather than switching to a different treatment).

If the individual has problems applying the product, consider changing the formulation (e.g. from topical lotion to dermal cream or vice versa).

If insecticide resistance is suspected:

Switch to a different class of insecticide (i.e. switch between malathion and permethrin).

Consider carbaryl if resistance to both malathion and permethrin is encountered or suspected.

If reinfestation seems probable:

Consider repeating the previous treatment (rather than switching to a different treatment).

Recommend to the individual that all close contacts be assessed for pubic lice and that all positive cases be treated simultaneously.

Basis for recommendation

Basis for recommendation

Because there is no direct evidence from clinical trials of treatments of pubic lice, this strategy for managing treatment failure and reinfestation is based on the strategy recommended in the section on Unsuccessful treatment in the CKS topic on Head lice.

Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC) (http://medicines.org.uk/emc), or the British National Formulary (BNF) (www.bnf.org).

Issues prescribing an insecticide

What issues do I need to consider when prescribing an insecticide to treat pubic lice?

Choice for pubic lice infestation

Which insecticide preparation should I prescribe for pubic lice infestation?

Prescribe:

Malathion 0.5% aqueous lotion, or

Permethrin 5% dermal cream

The choice primarily depends on a response to previous treatment, patient's age and if the person is a pregnant, or breastfeeding woman.

If appropriate treatment with one insecticide has not been successful, switch to a different class of insecticide (i.e. switch between malathion and permethrin rather than trying a different preparation containing the same class of insecticide).

Malathion is suitable for everyone — unless treatment with it has been unsuccessful.

Permethrin is suitable for individuals over the age of 18 years — unless they are pregnant, or breastfeeding, or treatment with it has been unsuccessful.

However, if malathion is ineffective or unsuitable, permethrin may be considered for people who are under the age of 18 years, or pregnant, or breastfeeding.

Carbaryl should not be considered — unless resistance to both malathion and pyrethroid insecticides (permethrin or phenothrin) is suspected.

Aqueous preparations and dermal cream are preferred over alcoholic preparations.

Insecticides should not be used more than once a week, and should not be used for more than three consecutive weeks.

Basis for recommendation

Because there is only limited evidence from three small clinical trials that insecticides can be effective treatments for pubic lice, the recommended strategy for management is based mainly on knowledge of the pubic louse's life cycle [Burgess et al, 1983; Burns, 2004] and the opinion of experts [Gratz, 1997; Ibarra, 1998; Scott, 2001; BNF 52, 2006; CDC, 2006; RCGP and BASHH, 2006].

There is no evidence from clinical trials to support a preference for one agent over another on the basis of effectiveness. In addition, no published data could be found regarding the incidence and level of resistance in pubic lice towards the different insecticides available in the UK.

Malathion and permethrin have been recommended based on the following considerations:

Malathion 0.5% aqueous lotion:

This aqueous-based product is licensed for the treatment of pubic lice in people aged 6 months onwards [ABPI Medicines Compendium, 2006].

Malathion is preferred when treating people who are pregnant or breastfeeding because of concerns that the other insecticides have less evidence on possible adverse effects [NTIS, 1999; NTIS, Personal Communication, 2006].

Permethrin:

Permethrin is offered along with malathion as it belongs to a different class of insecticide (a pyrethoid) to malathion (an organophosphate). This is to eradicate pubic lice that might have become resistant to a particular class of insecticide.

Permethrin is preferred for those who are pregnant or breastfeeding when malathion has been found to be ineffective.

Evidence, expert opinion and manufacturer's recommendation indicate this product to be safe in these people [BASHH, 2001; ATTRACT, 2004; ABPI Medicines Compendium, 2005; CDC, 2006].

Permethrin 5% dermal cream could be considered for children under 18 years if resistance to malathion is encountered.

This is an unlicensed indication as the product is not licensed for treating pubic lice in those under 18 years of age [ABPI Medicines Compendium, 2005]. However, this is a pragmatic recommendation as the product is licensed for treating scabies in those aged 2 months and over.

As a dermal cream, permethrin offers a formulation advantage for people who might find it difficult or uncomfortable to apply malathion aqueous lotion.

Carbaryl:

As for the treatment of head lice, carbaryl should only be used to treat pubic lice infestation if resistance to both malathion and permethrin is encountered.

Carbaryl belongs to a different class of insecticide (a carbamate) to malathion (an organophosphate) and permethrin (a pyrethroid).

Carbaryl is not licensed for the treatment of pubic lice.

Carbaryl became a prescription-only medicine following reports of carcinogenicity in rodents subjected to continuous exposure [CMO, 1995]. The Committee on the Safety of Medicines (CSM) concluded that the risk is theoretical, and there are no reports of tumours in association with carbaryl use in humans.

Phenothrin:

This alcohol-based preparation is licensed for use in adults and children from 6 months onward with pubic lice, but alcoholic preparations are not recommended (see below).

Phenothrin should not be used if permethrin proves ineffective (or vice versa) as they both belong to the same class of insecticides (both pyrethoids).

Alcoholic preparations are not recommended because:

Alcoholic formulations can irritate excoriated skin and the genitalia.

Alcoholic preparations can cause wheezing or irritate the skin, particularly in small children and people with asthma, eczema, or broken skin.

Some people dislike the smell of alcohol.

Alcoholic formulations are flammable and can pose a health hazard when used near a naked flame or heat source.

How to apply

How should insecticide preparations be applied when treating pubic lice?

Inform the individual that the recommended regimen is two applications of insecticide, 7 days apart.

Advise the person that the insecticide preparation should be applied to the whole body, paying particular attention to hairy areas, but that they should avoid getting it in the eyes.

Clarification / Additional information

When applying the insecticide to the whole body:

This includes the scalp, neck, ears and face.

Pay particular attention to the eyebrows and, if present, the beard and moustache.

Ensure sufficient product is applied to cover the pubic region, peri-anal region (around the anus), inner thighs down to the knees, and any hair that grows up from the pubic area to the chest/stomach.

Minimize contact with the eyes. If the product is accidentally introduced into the eyes, rinse immediately with plenty of water and reassure the person that this brief contact will not cause problems.

With malathion 0.5% aqueous lotion:

Leave on for 12 hours or overnight before washing.

With permethrin 5% dermal cream:

Leave on the skin for 24 hours before washing.

The cream should be applied to clean, dry, cool skin to reduce absorption through the skin [ABPI Medicines Compendium, 2005].

When rubbed gently into the skin, the appearance of the cream will disappear. Consequently, there is no need to continue to apply cream to the skin until it remains detectable on the surface [ABPI Medicines Compendium, 2005].

Basis for recommendation

This recommendation for two applications, 7 days apart, is based on expert opinion [BASHH, 2001; BNF 52, 2006; RCGP and BASHH, 2006].

It is a pragmatic and unlicensed approach, intended to eliminate lice hatching from eggs that survive the first application of insecticide.

No insecticide has been shown to be 100% effective in killing head lice and eggs after one application. There is a lack of clinical trials evidence for pubic lice infestation but it is assumed to be similar.

This is an unlicensed use of permethrin, and is different to the packaging information which states that a single application is sufficient. Malathion is now licensed as a course of two applications of insecticide 7 days apart [ABPI Medicines Compendium, 2007].

Insecticides should be used not more than once a week, and should be used for not more than three consecutive weeks [BNF 52, 2006].

Contact time:

Malathion: a contact time of 12 hours is recommended based on expert opinion [BNF 52, 2006; RCGP and BASHH, 2006].

Permethrin: a contact time of 24 hours is based on manufacturer's recommendation [ABPI Medicines Compendium, 2005].

The recommendations for applying aqueous-based preparations and dermal cream formulation are based on manufacturers' recommendations [ABPI Medicines Compendium, 2005; ABPI Medicines Compendium, 2006] and expert opinion [BNF 52, 2006; RCGP and BASHH, 2006].

The aim is to ensure that these products are applied correctly and no pockets of the infestation have escaped treatment.

Application to the head (apart from eye brows, moustache and beard) is an unlicensed indication when insecticides are used to treat pubic lice.

How much to apply

How much do I need to apply when using an insecticide preparation to treat pubic lice?

Apply a sufficient amount of insecticide preparation to cover all hairy surfaces of the body.

This includes the scalp, neck, ears, face and if present, the beard and moustache.

Clarification / Additional information

For a single application to the whole body, the following quantities have been recommended to treat an adult individual for pubic lice [BNF 52, 2006]:

Cream preparations: 30–60 g

Lotions: 100 mL

For children and relatively hair-free individuals, a proportionately reduced amount will be required.

Basis for recommendation

The quantities recommended are based on expert opinion [BNF 52, 2006].

These are generally more than that recommended by the manufacturers because topical application of insecticides to areas above the neck is not licensed for the treatment of pubic lice [ABPI Medicines Compendium, 2005; ABPI Medicines Compendium, 2006].

Choice for treating infected eyelashes

Which insecticide preparation should I prescribe for treating eyelashes infested with pubic lice?

When an insecticide is required to treat eyelashes infested with pubic lice:

Prescribe permethrin 1% cream rinse.

Clarification / Additional information

Permethrin 5% dermal cream should not be used to treat the eyelashes.

Permethrin is not an eye irritant but the cream itself may cause marked irritation [Scott, 2001; ABPI Medicines Compendium, 2005].

Basis for recommendation

Shampoo and creme rinse preparations are preferred because they tend to cause less eye irritation than other formulations of the same insecticide.

Permethrin 1% creme rinse is preferred based on expert opinion [Scott, 2001; RCGP and BASHH, 2006].

Malathion 1% cream shampoo have been used to treat eyelashes with pubic infestation [Rundle and Hughes, 1993; Manjunatha et al, 2006].

This product is not prescribable on the National Health Service (NHS), but can be purchased from pharmacies.

How to apply to eyelashes

How should insecticide preparation be applied to eyelashes infected with pubic lice?

When applying an insecticide preparation to treat eyelashes infested with pubic lice:

Carefully apply the insecticide to the lid margins with a cotton bud or cotton swab.

Keep the eyelids closed throughout the treatment.

Leave for 5 to 10 minutes before washing the insecticide off with water.

Repeat treatment after 7 days.

If insecticide preparation irritates the eye, wash the eye immediately with plenty of water.

Clarification / Additional information

For permethrin 1% cream rinse, a contact time of 10 minutes has been recommended [Scott, 2001; RCGP and BASHH, 2006].

For malathion 1% cream shampoo, a minimal contact time of 5 minutes is required [Rundle and Hughes, 1993].

Basis for recommendation

The recommendations for applying insecticides to the eyelashes are based on expert opinion [Scott, 2001; RCGP and BASHH, 2006] and case studies [Rundle and Hughes, 1993; Manjunatha et al, 2006].

Similar to the treatment of the whole body, two applications, 7 days apart, is recommended.

This is a pragmatic approach, intended to eliminate lice hatching from eggs that survive the first application of insecticide.

Adverse effects

What adverse effects should I advise people to be aware of when treating pubic lice infestation with an insecticide?

Inform the individual or carer that adverse effects tend to be minor and that insecticide preparations can cause local irritation of the skin or the eyes.

Advise the individual:

To wash the insecticide preparation off the skin if irritation is a problem.

To wash the eyes with plenty of water if the insecticide gets into the eyes.

Warn the person that aqueous and alcoholic-based preparations may discolour permed, coloured, or bleached hair.

Basis for recommendation

The main adverse effect of insecticides when used to treat head lice and scabies is skin irritation. See the CKS topics on Head lice and Scabies.

The Committee on Safety of Medicines (CSM) found no evidence to indicate that carbaryl or malathion pose a health hazard to people using these insecticides [CMO, 1995; CSM, 2000].

The few published trials on insecticides used to treat pubic lice included too few participants to assess the risk of adverse effects — see Treatments for pubic lice.

Issues prescribing ointments for eyelashes

What issues do I need to consider when prescribing ophthalmic ointments to treat pubic lice in eyelashes?

Choice of occlusive ointment

Which occlusive ointments should I prescribe for treating eyelashes with pubic lice?

When treating eyelashes infested with pubic lice with an occlusive ointment:

Prescribe an inert ophthalmic ointment with a white or yellow soft paraffin base (e.g. Simple eye ointment BP, Larci-Lube®, Lubri-Tears®).

Basis for recommendation

The mechanism of action is through the suffocation of adult lice and nymphs (immature lice).

This is achieved by coating the lice with a greasy layer of ointment.

An inert ophthalmic ointment with a white or yellow soft paraffin base provides a suitable consistency to produce this effect.

Inert ophthalmic ointments (e.g. Simple Eye Ointment BP) are preferred over topical ointments that are not formulated for use in the eyes because there is no risk of adverse effects should the ointment spread to the eye. In addition, ophthalmic ointments are sterile prior to use, reducing risk of eye infection.

How to apply

How should occlusive ophthalmic ointments be applied to eyelashes infested with pubic lice?

When an occlusive ophthalmic ointment is used to treat eyelashes infested with pubic lice:

Ensure all the eyelashes are well covered by the ointment.

Apply the ointment twice daily to the eyelashes.

Before applying a new coating of ointment, gently wipe the eyelashes and eyelids clean with facial tissue paper.

Discard used facial tissue papers immediately.

Wash hands before and after applying the ointment.

Continue the treatment for at least 8 days, and until 10 days if lice (not nits or eggs) continue to be seen.

Basis for recommendation

Multiple applications are required to ensure the lice are covered.

Daily applications for at least 8 days (and until 10 days if lice continue to be seen) are recommended to kill nymphs hatching from eggs.

This is a pragmatic approach, intended to eliminate lice hatching from eggs as lice eggs can take 6–10 days to hatch.

There is no evidence to indicate that lice eggs are affected.

Evidence

Evidence

Supporting evidence

Treatments for pubic lice

Evidence on treatments for pubic lice

Evidence from three small trials with large differences in failure rates suggests that pyrethrins can effectively treat infestations of pubic lice. One case report suggests that pubic lice can be resistant to pyrethrins.

CKS found no randomized trials of malathion or phenothrin for the treatment of pubic lice.

Three small randomized controlled trials of treatments for pubic lice have compared pyrethrins with lindane. Two trials reported complete clearance of pubic lice and symptoms, and one trial reported a failure rate of 43%. Details are shown in Table 1.

Lindane has been withdrawn from the UK market because of concerns about possible toxicity and the development of resistance by pubic lice [BASHH, 2001; Roos et al, 2001]. It is therefore not mentioned elsewhere in this CKS topic.

A case report documents pubic lice infestation in a 43-year-old man which failed to respond to four careful applications of a preparation containing 0.165% pyrethrins and 2% piperonyl butoxide [Speare and Koehler, 2001].

Table 1 . Evidence from randomized clinical trials of treatments for pubic lice.
Study Failure rate with: Comment
Permethrin Lindane*
[Newsom et al, 1979] 0% (0/15) 0% (0/15) 1 application for 10 minutes of 0.3% pyrethrins synergized by 3.0% piperonyl butoxide (RID) 1 application for 12 hours of lindane shampoo (Kwell) follow up at 1 week
[Smith and Walsh, 1980] 0% (0/15) 0% (0/15) 0.3% pyrethrins synergized by 3.0% piperonyl butoxide (RID) and lindane shampoo (Kwell) 1 application to pubic hair (and axilla if lice were present there); RID was rinsed off after after 4 minutes, lindane was rinsed off after 10 minutes; followed by combing with a fine toothed comb follow up at 1 week
[Kalter et al, 1987] 43% (12/28) 40% (10/25) 1% permethrin (Nix) cream rinse for 10 minutes 1% lindane shampoo (Kwell) for 4 minutes 1 application to the area between umbilicus and knees; followed by combing with a fine toothed comb follow up after 8–12 days
* Lindane is the primary synonym for gamma-hexachlorocyclohexane (HCH), which is also known as benzene hexachloride (BHC) and gamma benzene hexachloride (GBH).

Search strategy

Scope of search

A literature search was conducted for guidelines, systematic reviews and randomized controlled trials on primary care management of pubic lice.

Search dates

2007 - October 2011

Key search terms

Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline and these were adapted for other databases. Further details are available on request.

exp Lice infestations/, exp Phthirus/, public lice.tw., phthirus pubis.tw.

Table 1 . Key to search terms.
Search commands Explanation
/ indicates a MeSh subject heading with all subheadings selected
.tw indicates a search for a term in the title or abstract
exp indicates that the MeSH subject heading was exploded to include the narrower, more specific terms beneath it in the MeSH tree
$ indicates that the search term was truncated (e.g. wart$ searches for wart and warts)
Sources of guidelines

National Institute for Health and Care Excellence (NICE)

Scottish Intercollegiate Guidelines Network (SIGN)

NICE Evidence

National Guidelines Clearinghouse

New Zealand Guidelines Group

British Columbia Medical Association

Canadian Medical Association

Institute for Clinical Systems Improvement

Guidelines International Network

National Library of Guidelines

National Health and Medical Research Council (Australia)

Alberta Medical Association

University of Michigan Medical School

Michigan Quality Improvement Consortium

Royal College of Nursing

Singapore Ministry of Health

Royal Australian College of General Practitioners

Health Protection Agency

National Resource for Infection Control

CREST

World Health Organization

NHS Scotland National Patient Pathways

Agency for Healthcare Research and Quality

TRIP database

Patient UK Guideline links

UK Ambulance Service Clinical Practice Guidelines

RefHELP NHS Lothian Referral Guidelines

Medline (with guideline filter)

Driver and Vehicle Licensing Agency

Sources of systematic reviews and meta-analyses

The Cochrane Library :

Systematic reviews

Protocols

Database of Abstracts of Reviews of Effects

Medline (with systematic review filter)

EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

NIHR Health Technology Assessment programme

The Cochrane Library :

NHS Economic Evaluations

Health Technology Assessments

Canadian Agency for Drugs and Technologies in Health

International Network of Agencies for Health Technology Assessment

Sources of randomized controlled trials

The Cochrane Library :

Central Register of Controlled Trials

Medline (with randomized controlled trial filter)

EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

Bandolier

Drug & Therapeutics Bulletin

MeReC

NPCi

BMJ Clinical Evidence

DynaMed

TRIP database

Central Services Agency COMPASS Therapeutic Notes

Sources of national policy

Department of Health

Health Management Information Consortium (HMIC)

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

British National Formulary (BNF)

electronic Medicines Compendium (eMC)

European Medicines Agency (EMEA)

LactMed

Medicines and Healthcare products Regulatory Agency (MHRA)

REPROTOX

Scottish Medicines Consortium

Stockley's Drug Interactions

TERIS

TOXBASE

Micromedex

UK Medicines Information

References

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ATTRACT (2004) Is there any evidence on the safety of Lyclear (permethrin) in the treatment of scabies in pregnancy? ATTRACT..National Public Health Service for Wales.www.attract.wales.nhs.uk

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Ibarra, J. (1998) Phthiriasis. In: Figueroa, J., Hall, S. and Ibarra, J. (Eds.) Primary health care guide to common UK parasitic diseases. London: Community Hygiene Concern. Chapter 3. 21-24.

Kalter, D.C., Sperber, J., Rosen, T. and Matarasso, S. (1987) Treatment of pediculosis pubis. Clinical comparison of efficacy and tolerance of 1% lindane shampoo vs 1% permethrin creme rinse. Archives of Dermatology 123(10), 1315-1319. [Abstract]

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Manjunatha, N.P., Jayamanne, G.R., Desai, S.P. et al. (2006) Pediculosis pubis: presentation to ophthalmologist as Pthriasis palpebrarum associated with corneal epithelial keratitis. International Journal of STD & AIDS 17(6), 424-426. [Abstract]

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