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Lice and scabies
GENITAL SKIN CONDITIONS
Lice and scabies
and, occasionally, the eyelashes. Scratching may cause secondary bacterial infection in the skin.
Chris Bignell
Scabies The adult mites of S. scabiei have a rounded body, four pairs of legs and are barely perceptible to the naked eye. They tunnel into the stratum corneum of the epidermis and feed on cellular material. Eggs are laid by fertilized females in the burrows. The eggs hatch into larvae, which crawl out of the burrow and progress through nymphal stages to adults.1,2 The cycle from egg to adult is completed in 10e13 days. Scratching, bathing and immunological reaction combine to prevent all but a few larvae surviving to adulthood. Typically, an infected adult with scabies carries about 10e15 mature mites in the skin.2 Unlike pediculosis, scabies is seen in all age groups with no peak in prevalence in young adults, confirming that non-sexual skin contact is an important mode of transmission. Certain patient groups can develop a severe form of scabies called crusted scabies, which is highly infectious and characterized by hyperkeratosis and a much higher burden of mites.3 It is seen in extremely physically incapacitated individuals and patients with immune dysfunction (including those with HIV). Secondary bacterial infection of the skin can occasionally cause significant morbidity.
Abstract Scabies and pubic lice are parasitic infections of the skin that are predominantly transmitted by close person-to-person contact. The principal symptom for both infections is itching. Diagnosis is established by clinical examination for pubic lice and clinical suspicion supplemented by microscopy for scabies. A single application of permethrin cream is the treatment of choice for both infections. Recent sexual partners should also receive treatment.
Keywords Infestations; itching; pediculosis; permethrin; scabies
Pediculosis pubis is caused by the pubic louse (crab louse) Phthirus pubis and scabies by the mite Sarcoptes scabiei. They are obligate human parasites that live on or within the skin and are transmitted by close person-to-person contact with an infected person. In developed countries pediculosis and scabies are considered to be sexually transmitted infections (STIs) because sexual intercourse affords a major opportunity for transmission between adults. Their presence in young adults should prompt screening for other STIs. Condoms do not provide protection. Non-sexual skin-to-skin contact (holding hands) is important in scabies transmission. Acquisition of scabies or pediculosis from shared bedding or clothing appears to be uncommon.
Clinical features: the mite causes generalized itching that is characteristically most intense at night. The rash is polymorphic.3,4 Symptoms develop after 3e6 weeks in primary infection and result from the development of an immune response to the mite. Symptoms develop rapidly on re-infection. Individuals with crusted scabies have milder itching but a much more dramatic rash.3 The pruritic lesions are typically distributed on the: interdigital web spaces of the hands flexor surface of the wrists extensor aspect of the elbows buttocks and genital area in males anterior axillary folds periumbilical region. Several types of lesion can occur in scabies.3,4 The characteristic lesion of scabies is the burrow (Figure 2) e a short, wavy, dirty-looking line, often extending from
Clinical features and diagnosis Pediculosis P. pubis is morphologically distinct from the other two species of louse that infect humans e the head louse, Pediculus humanus capitis, and the body louse, Pediculus humanus humanus. The pubic louse is short and has a width greater than its length. Enlarged claw-like middle and hind legs emerge close together from the anterior abdomen, giving it the appearance of a crab (Figure 1). Adult females lay eggs encased in a hard shell, fixed to the base of hairs. Development from egg through nymphal stages to adult takes 2e3 weeks.1,2 Crab lice are slowly mobile, feed on human blood and seldom survive more than 24 hours once removed from their host. Pubic lice are not known to transmit any disease. Clinical features: the predominant symptom of pediculosis is itching, which develops following allergic sensitization. Adult lice and their eggs (nits) are easily visible to the naked eye. Asymptomatic individuals may notice lice on themselves or rustcoloured spots on their underclothes. Examination may reveal asymptomatic, bluish macules (maculae caeruleae) in the infected area; these lesions are thought to represent sites of louse bites. Although crab lice are fairly sedentary, infection may spread from the genital area to the trunk, the axillae, the thighs
Chris Bignell FRCP is Consultant Physician in Genitourinary Medicine at Nottingham City Hospital, Nottingham, UK. Competing interests: none declared.
MEDICINE --:-
Figure 1 Crab louse.
1
Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bignell C, Lice and scabies, Medicine (2014), http://dx.doi.org/10.1016/j.mpmed.2014.04.008
GENITAL SKIN CONDITIONS
genital area is suggestive of scabies, particularly when there is a history of itching in a sexual partner or close domestic contact. Demonstration of the mite confirms the diagnosis but is not always possible. Mites, ova and faecal pellets may be identified by low-power microscopy of material from skin scrapings (Figure 4). A magnifying glass can be helpful for selecting an unexcoriated burrow, and a tiny vesicle containing the mite may be seen at one end. The burrow is moistened and the skin gently scraped with a scalpel blade until the top layer of skin is removed. The material is collected on a glass microscope slide and a cover slip added before microscopy. Indirect diagnostic tests, including serology, have so far proved unhelpful.5
Management Figure 2 The pathognomonic lesion of scabies is the burrow.
Pubic lice Two topical agents are widely recommended for the treatment of pubic lice: Permethrin 5% cream or malathion 0.5% aqueous lotion, both of which are applied to the body from the neck downwards and washed off after 12 hours. Resistance to treatment is reported and when treatment failure with one of these agents is suspected, the alternative should be applied.
an erythematous papule and usually located on the fingerwebs, wrists, elbows or penis. Small, erythematous, often excoriated papules attributed to feeding larvae and nymphs may occur at all of the above sites (Figure 3). Firm, reddish, nodular lesions may occur on the glans penis, penile shaft, scrotal skin, elbows and axillary folds. Viable mites are seldom found in these nodules, which may persist long after treatment. Excoriation of scabetic lesions is common, together with eczematization and secondary infection, which may considerably alter the appearance of the lesions. The crusted form of scabies has a scaling, psoriasiform appearance and may be widespread.
Scabies Topical permethrin (5% cream) appears to be the most effective treatment for scabies; it is the treatment of choice in the UK and is safe for pregnant women.5e7 It is applied to all body areas except the face and washed off after 8e12 hours. Malathion (0.5% aqueous lotion) has also been used successfully to treat scabies since the 1970s. There are no published controlled trials comparing the effectiveness of malathion with permethrin. Ivermectin is an oral treatment for scabies that has been the subject of several clinical trials and is used in the management of scabies epidemics in long-term care facilities and in treating crusted scabies. It is available only on a named patient basis. Crotamiton (10% cream) is a less effective scabicide, but may be used to ameliorate persistent itch. A sedating antihistamine at night may be helpful to relieve the itch in scabies.
Diagnosis: the diagnosis of scabies is often made on clinical suspicion.5 A pruritic rash involving the hands, trunk and male
Figure 4 Material from skin lesions is obtained by scraping, curettage or shave biopsy.
Figure 3 Erythematous papulae.
MEDICINE --:-
2
Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bignell C, Lice and scabies, Medicine (2014), http://dx.doi.org/10.1016/j.mpmed.2014.04.008
GENITAL SKIN CONDITIONS
Lindane was formerly a popular topical treatment for both lice and scabies, but has been discontinued in the UK because of toxicity. Although a single application of permethrin cream or malathion lotion has generally been reported to be effective, there is doubt whether these agents are ovicidal and the manufacturers recommend a second application after 7 days. In the usual forms of scabies in adults, treatment should be applied to the whole body surface, including the neck, scalp and ears, and left on for 8e12 hours, usually overnight. Patients should be informed that resolution of the irritation and skin lesions associated with scabies may take several weeks. Persistence of original skin lesions for more than 3 weeks after treatment, the development of new lesions or finding a live mite on microscopy suggest treatment failure, which may result from incorrect application, re-infestation or mite resistance. Worsening of itching may occur with some topical therapies because of allergic dermatitis.
REFERENCES 1 Morse SA, Ballard RC, Holmes KK, et al. In: Atlas of sexually transmitted diseases and AIDS. 3rd edn. Oxford: Elsevier Science, 2003. 2 Leone PA. Scabies and pediculosis pubis: an update of treatment regimens and general review. Clin Infect Dis 2007; 44(suppl 3): S153e9. 3 Walton SF, Currie BJ. Problems in diagnosing scabies, a global disease in human and animal populations. Clin Microbiol Rev 2007; 20: 268e79. 4 Chosidow O. Scabies and pediculosis. Lancet 2000; 355: 819e26. 5 Leung V, Miller M. Detection of scabies: a systematic review of diagnostic methods. Can J Infect Dis Med Microbiol 2011; 22: 143e6. 6 Strong M, Johnstone P. Interventions for treating scabies. Cochrane Database Syst Rev 2010. Issue 3. Art. No.:CD000320. 7 Mounsey KE, McCarthy JS. Treatment and control of scabies. Curr Opin Infect Dis 2013; 26: 133e9.
Practice points
Bed linen and clothing After treatment patients should be advised to decontaminate bed linen, towels and clothing by machine-washing.
C
C C
Contacts Both pediculosis and scabies are transmitted only by intimate physical contact. It is important to treat sexual partners and, in the case of scabies, close household contacts to prevent reinfestation. A
MEDICINE --:-
C
C
3
Young adults with pediculosis or scabies should be screened for other STIs The itch of scabies is characteristically most intense at night The diagnosis of scabies should be considered in debilitated patients with crusted psoriasiform rash Adequate coverage of the whole body is achieved with 60 g of permethrin 5% cream Patients should be warned that the genital lesions and itch in scabies may take several weeks to resolve after treatment
Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bignell C, Lice and scabies, Medicine (2014), http://dx.doi.org/10.1016/j.mpmed.2014.04.008
Lice and scabies
and, occasionally, the eyelashes. Scratching may cause secondary bacterial infection in the skin.
Chris Bignell
Scabies The adult mites of S. scabiei have a rounded body, four pairs of legs and are barely perceptible to the naked eye. They tunnel into the stratum corneum of the epidermis and feed on cellular material. Eggs are laid by fertilized females in the burrows. The eggs hatch into larvae, which crawl out of the burrow and progress through nymphal stages to adults.1,2 The cycle from egg to adult is completed in 10e13 days. Scratching, bathing and immunological reaction combine to prevent all but a few larvae surviving to adulthood. Typically, an infected adult with scabies carries about 10e15 mature mites in the skin.2 Unlike pediculosis, scabies is seen in all age groups with no peak in prevalence in young adults, confirming that non-sexual skin contact is an important mode of transmission. Certain patient groups can develop a severe form of scabies called crusted scabies, which is highly infectious and characterized by hyperkeratosis and a much higher burden of mites.3 It is seen in extremely physically incapacitated individuals and patients with immune dysfunction (including those with HIV). Secondary bacterial infection of the skin can occasionally cause significant morbidity.
Abstract Scabies and pubic lice are parasitic infections of the skin that are predominantly transmitted by close person-to-person contact. The principal symptom for both infections is itching. Diagnosis is established by clinical examination for pubic lice and clinical suspicion supplemented by microscopy for scabies. A single application of permethrin cream is the treatment of choice for both infections. Recent sexual partners should also receive treatment.
Keywords Infestations; itching; pediculosis; permethrin; scabies
Pediculosis pubis is caused by the pubic louse (crab louse) Phthirus pubis and scabies by the mite Sarcoptes scabiei. They are obligate human parasites that live on or within the skin and are transmitted by close person-to-person contact with an infected person. In developed countries pediculosis and scabies are considered to be sexually transmitted infections (STIs) because sexual intercourse affords a major opportunity for transmission between adults. Their presence in young adults should prompt screening for other STIs. Condoms do not provide protection. Non-sexual skin-to-skin contact (holding hands) is important in scabies transmission. Acquisition of scabies or pediculosis from shared bedding or clothing appears to be uncommon.
Clinical features: the mite causes generalized itching that is characteristically most intense at night. The rash is polymorphic.3,4 Symptoms develop after 3e6 weeks in primary infection and result from the development of an immune response to the mite. Symptoms develop rapidly on re-infection. Individuals with crusted scabies have milder itching but a much more dramatic rash.3 The pruritic lesions are typically distributed on the: interdigital web spaces of the hands flexor surface of the wrists extensor aspect of the elbows buttocks and genital area in males anterior axillary folds periumbilical region. Several types of lesion can occur in scabies.3,4 The characteristic lesion of scabies is the burrow (Figure 2) e a short, wavy, dirty-looking line, often extending from
Clinical features and diagnosis Pediculosis P. pubis is morphologically distinct from the other two species of louse that infect humans e the head louse, Pediculus humanus capitis, and the body louse, Pediculus humanus humanus. The pubic louse is short and has a width greater than its length. Enlarged claw-like middle and hind legs emerge close together from the anterior abdomen, giving it the appearance of a crab (Figure 1). Adult females lay eggs encased in a hard shell, fixed to the base of hairs. Development from egg through nymphal stages to adult takes 2e3 weeks.1,2 Crab lice are slowly mobile, feed on human blood and seldom survive more than 24 hours once removed from their host. Pubic lice are not known to transmit any disease. Clinical features: the predominant symptom of pediculosis is itching, which develops following allergic sensitization. Adult lice and their eggs (nits) are easily visible to the naked eye. Asymptomatic individuals may notice lice on themselves or rustcoloured spots on their underclothes. Examination may reveal asymptomatic, bluish macules (maculae caeruleae) in the infected area; these lesions are thought to represent sites of louse bites. Although crab lice are fairly sedentary, infection may spread from the genital area to the trunk, the axillae, the thighs
Chris Bignell FRCP is Consultant Physician in Genitourinary Medicine at Nottingham City Hospital, Nottingham, UK. Competing interests: none declared.
MEDICINE --:-
Figure 1 Crab louse.
1
Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bignell C, Lice and scabies, Medicine (2014), http://dx.doi.org/10.1016/j.mpmed.2014.04.008
GENITAL SKIN CONDITIONS
genital area is suggestive of scabies, particularly when there is a history of itching in a sexual partner or close domestic contact. Demonstration of the mite confirms the diagnosis but is not always possible. Mites, ova and faecal pellets may be identified by low-power microscopy of material from skin scrapings (Figure 4). A magnifying glass can be helpful for selecting an unexcoriated burrow, and a tiny vesicle containing the mite may be seen at one end. The burrow is moistened and the skin gently scraped with a scalpel blade until the top layer of skin is removed. The material is collected on a glass microscope slide and a cover slip added before microscopy. Indirect diagnostic tests, including serology, have so far proved unhelpful.5
Management Figure 2 The pathognomonic lesion of scabies is the burrow.
Pubic lice Two topical agents are widely recommended for the treatment of pubic lice: Permethrin 5% cream or malathion 0.5% aqueous lotion, both of which are applied to the body from the neck downwards and washed off after 12 hours. Resistance to treatment is reported and when treatment failure with one of these agents is suspected, the alternative should be applied.
an erythematous papule and usually located on the fingerwebs, wrists, elbows or penis. Small, erythematous, often excoriated papules attributed to feeding larvae and nymphs may occur at all of the above sites (Figure 3). Firm, reddish, nodular lesions may occur on the glans penis, penile shaft, scrotal skin, elbows and axillary folds. Viable mites are seldom found in these nodules, which may persist long after treatment. Excoriation of scabetic lesions is common, together with eczematization and secondary infection, which may considerably alter the appearance of the lesions. The crusted form of scabies has a scaling, psoriasiform appearance and may be widespread.
Scabies Topical permethrin (5% cream) appears to be the most effective treatment for scabies; it is the treatment of choice in the UK and is safe for pregnant women.5e7 It is applied to all body areas except the face and washed off after 8e12 hours. Malathion (0.5% aqueous lotion) has also been used successfully to treat scabies since the 1970s. There are no published controlled trials comparing the effectiveness of malathion with permethrin. Ivermectin is an oral treatment for scabies that has been the subject of several clinical trials and is used in the management of scabies epidemics in long-term care facilities and in treating crusted scabies. It is available only on a named patient basis. Crotamiton (10% cream) is a less effective scabicide, but may be used to ameliorate persistent itch. A sedating antihistamine at night may be helpful to relieve the itch in scabies.
Diagnosis: the diagnosis of scabies is often made on clinical suspicion.5 A pruritic rash involving the hands, trunk and male
Figure 4 Material from skin lesions is obtained by scraping, curettage or shave biopsy.
Figure 3 Erythematous papulae.
MEDICINE --:-
2
Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bignell C, Lice and scabies, Medicine (2014), http://dx.doi.org/10.1016/j.mpmed.2014.04.008
GENITAL SKIN CONDITIONS
Lindane was formerly a popular topical treatment for both lice and scabies, but has been discontinued in the UK because of toxicity. Although a single application of permethrin cream or malathion lotion has generally been reported to be effective, there is doubt whether these agents are ovicidal and the manufacturers recommend a second application after 7 days. In the usual forms of scabies in adults, treatment should be applied to the whole body surface, including the neck, scalp and ears, and left on for 8e12 hours, usually overnight. Patients should be informed that resolution of the irritation and skin lesions associated with scabies may take several weeks. Persistence of original skin lesions for more than 3 weeks after treatment, the development of new lesions or finding a live mite on microscopy suggest treatment failure, which may result from incorrect application, re-infestation or mite resistance. Worsening of itching may occur with some topical therapies because of allergic dermatitis.
REFERENCES 1 Morse SA, Ballard RC, Holmes KK, et al. In: Atlas of sexually transmitted diseases and AIDS. 3rd edn. Oxford: Elsevier Science, 2003. 2 Leone PA. Scabies and pediculosis pubis: an update of treatment regimens and general review. Clin Infect Dis 2007; 44(suppl 3): S153e9. 3 Walton SF, Currie BJ. Problems in diagnosing scabies, a global disease in human and animal populations. Clin Microbiol Rev 2007; 20: 268e79. 4 Chosidow O. Scabies and pediculosis. Lancet 2000; 355: 819e26. 5 Leung V, Miller M. Detection of scabies: a systematic review of diagnostic methods. Can J Infect Dis Med Microbiol 2011; 22: 143e6. 6 Strong M, Johnstone P. Interventions for treating scabies. Cochrane Database Syst Rev 2010. Issue 3. Art. No.:CD000320. 7 Mounsey KE, McCarthy JS. Treatment and control of scabies. Curr Opin Infect Dis 2013; 26: 133e9.
Practice points
Bed linen and clothing After treatment patients should be advised to decontaminate bed linen, towels and clothing by machine-washing.
C
C C
Contacts Both pediculosis and scabies are transmitted only by intimate physical contact. It is important to treat sexual partners and, in the case of scabies, close household contacts to prevent reinfestation. A
MEDICINE --:-
C
C
3
Young adults with pediculosis or scabies should be screened for other STIs The itch of scabies is characteristically most intense at night The diagnosis of scabies should be considered in debilitated patients with crusted psoriasiform rash Adequate coverage of the whole body is achieved with 60 g of permethrin 5% cream Patients should be warned that the genital lesions and itch in scabies may take several weeks to resolve after treatment
Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bignell C, Lice and scabies, Medicine (2014), http://dx.doi.org/10.1016/j.mpmed.2014.04.008