Elsevier

The Lancet

Volume 367, Issue 9524, 27 May–2 June 2006, Pages 1767-1774
The Lancet

Seminar
Scabies

https://doi.org/10.1016/S0140-6736(06)68772-2Get rights and content

Summary

Scabies is a neglected parasitic disease that is a major public health problem in many resource-poor regions. It causes substantial morbidity from secondary infections and post-infective complications such as acute post-streptococcal glomerulonephritis. Disease control requires treatment of the affected individual and all people they have been in contact with, but is often hampered by inappropriate or delayed diagnosis, poor treatment compliance, and improper use of topical compounds such as permethrin, lindane, or benzyl benzoate. In addition to concerns over toxicity with such compounds, parasite resistance seems to be increasing. Oral ivermectin is an alternative that has been used successfully in community control programmes. Plant derivatives such as turmeric, neem, and tea tree oil are also promising future treatments. The disease is strongly associated with poverty and overcrowding, and the associated stigma can ostracise affected individuals. Treatment of scabies in poor countries needs to integrate drug treatment programmes with efforts to improve the socioeconomic conditions and education programmes to reduce stigma. We expect the future to bring more sensitive and specific clinical and laboratory-based diagnostic methods, as well as new therapeutic strategies.

Section snippets

Parasite lifecycle and transmission

Once on human skin, female mites burrow into the epidermis for about 30 mins.4 The male mite explores the skin for an unfertilised female.2, 15 Female mites live for 4–6 weeks and produce 2–4 eggs per day, which are deposited in the burrowed tunnel.2 Larvae hatch 2–4 days after the eggs have been laid, and adult mites develop 10–14 days later.2, 3, 16

In a key experiment in the UK in 1940, Mellanby2, 17 showed that transmission occurs by body contact and that under normal conditions fomites

Epidemiology

Scabies can occur both epidemically and endemically. Sporadic cases are typically seen in industrialised countries, where epidemics usually occur in institutional settings or in socially deprived groups. Within a community, scabies is unevenly distributed, and prevalence in the general population is usually low.14, 20, 21, 22 However, the frequency of infested individuals can be 40–80% in some high risk groups, as studies in dermatology patients in sub-Saharan Africa, Indigenous communities in

Immune response

The signs and symptoms of scabies are the result of an adaptive immune response and only occur after sensitisation. This explains the delayed onset of symptoms in primary infestations. When patients are infested for a second time, hypersensitivity develops within a day.16 Protective immunity could explain why experimental re-infestation is difficult in sensitised patients, and why parasite load is usually lower in individuals with a second infestation compared with those being infested for the

Molecular biology

The absence of an animal model and in vitro methods for research for S scabiei has hampered research on the biology of the parasite and its relation with the host.7, 41 For a few years, S scabiei cDNA libraries and expressed sequence tag (EST) databases have been available.7, 42, 43, 44, 45 Fischer and colleagues45 used an EST approach to identify homologues of dust mite allergens in S scabiei.45 Several homologues have been cloned in the meanwhile.46, 47, 48 Thousands of cDNA clones have been

Clinical aspects

Scabies can mimic a broad range of skin diseases. Once a female mite has identified a suitable place on the skin, it rapidly penetrates into the epidermis and burrows more or less parallel to the corneal layers at a rate of 0·5–5 mm per day. The resulting tunnel is rarely visible. Clinically visible burrows, which can be seen after several days, probably occur when there is a local host reaction around the tunnel.

The burrow looks like a short wavy line, and is most commonly seen on the fingers,

Associated pathology

Pruritus, the result of a hypersensitive reaction to components of the saliva, eggs, and faecal material of the mites, typically worsens at night and can prevent patients from sleeping well. Breaks in the epidermis, scratching, and subsequent excoriations serve as an entry point for pathogenic bacteria. In the tropics, scabies is frequently associated with secondary bacterial infection of the lesions, and staphylococci or streptococci are common.52, 53, 54, 55, 56 Pyoderma is therefore a

Diagnosis

In primary infestation, signs and symptoms only develop after 3–4 weeks. A clinical diagnosis can be made when a burrow is detected at a typical predilection site and the lesion is severely itching. In this case, even a single burrow is pathognomonic. In practice, however, burrows are often obliterated by bathing, scratching, formation of crusts, or superinfection. In severely affected communities in developing countries and in Australia, burrows are rarely seen (Heukelbach J, unpublished).7

Case management

Immediate treatment of the patient with an effective drug and rigorous treatment of close contacts remains the mainstay in case management. Since individuals can be infested without showing symptoms, people they have been in contact with should be treated independently whether clinical symptoms are present or not.78

Surprisingly, few controlled studies have been done to compare the effectiveness of topical compounds on the market.79 As a result, treatment recommendations vary from one country to

Scabies in the developing world

Unlike in industrialised countries, scabies is a major public health threat in the developing world. Scabies is common in resource-poor urban and rural communities, with prevalence reaching up to 10% in the general population and 50% in children.6, 23, 29, 37, 130, 131, 132, 133 In an urban slum in Bangladesh, the incidence in children younger than 6 years was 952 per 1000 per year, meaning that nearly all children had had at least one S scabiei infection per year.37

The belief that scabies in

The future

A better understanding of factors associated with infestation and severe disease is of pivotal importance. The molecular characterisation of mites isolated from infested individuals could help to track the spread of S scabiei—eg, in a nursery, kindergarten, or resource-poor community. The identification of behavioural and environmental risk factors in defined sociocultural settings will provide the rationale to target control measures to the most vulnerable groups.

An ELISA for the detection of

Search strategy and selection criteria

MEDLINE, LILACS, and COCHRANE searches using the keywords “parasitic skin disease”, “scabies”, “sarna”, “escabiose” and “galle” were used as a primary source of reference. Reference lists found in Spanish, Portuguese, and French language textbooks on dermatology, parasitic diseases, and tropical medicine were also used. The inclusion or exclusion of individual manuscripts was based on the originality of the data and a robust study design.

References (137)

  • TF Cestari et al.

    Scabies, pediculosis, bedbugs, and stinkbugs: uncommon presentations

    Clin Dermatol

    (2005)
  • HC Whittle et al.

    Scabies, pyoderma and nephritis in Zaria, Nigeria. A clinical and epidemiological study

    Trans R Soc Trop Med Hyg

    (1973)
  • M Svartman et al.

    Epidemic scabies and acute glomerulonephritis in Trinidad

    Lancet

    (1972)
  • T Poon-King et al.

    Epidemic acute nephritis with reappearance of M-type 55 streptococci in Trinidad

    Lancet

    (1973)
  • HF Reid et al.

    Epidemic scabies in four Caribbean islands, 1981–1988

    Trans R Soc Trop Med Hyg

    (1990)
  • HM Bastian et al.

    Scabies mimicking systemic lupus erythematosus

    Am J Med

    (1997)
  • JE Gach et al.

    Crusted scabies looking like psoriasis

    Lancet

    (2000)
  • O Chosidow

    Scabies and pediculosis

    Lancet

    (2000)
  • A Kissmeyer

    Rapid ambulatory treatment of scabies with benzyl benzoate lotion

    Lancet

    (1937)
  • RS Purvis et al.

    An outbreak of lindane-resistant scabies treated successfully with permethrin 5% cream

    J Am Acad Dermatol

    (1991)
  • D Taplin et al.

    Community control of scabies: a model based on use of permethrin cream

    Lancet

    (1991)
  • SF Walton et al.

    Studies in vitro on the relative efficacy of current acaricides for Sarcoptes scabiei var. hominis

    Trans R Soc Trop Med Hyg

    (2000)
  • M Ramos-e-Silva

    Giovan Cosimo Bonomo 1663–1696: discoverer of the etiology of scabies

    Int J Dermatol

    (1998)
  • K Mellanby

    Biology of the parasite

  • LG Arlian

    Biology, host relations, and epidemiology of Sarcoptes scabiei

    Annu Rev Entomol

    (1989)
  • LG Arlian et al.

    Survival of adults and development stages of Sarcoptes scabiei var. canis when off the host

    Exp Appl Acarol

    (1989)
  • A Chakrabarti

    Some epidemiological aspects of animal scabies in human population

    Int J Zoonoses

    (1985)
  • DB Pence et al.

    Sarcoptic mange in wildlife

    Rev Sci Tech

    (2002)
  • A Fain

    Epidemiological problems of scabies

    Int J Dermatol

    (1978)
  • TA Morsy et al.

    Human scabies acquired from a pet puppy

    J Egypt Soc Parasitol

    (1994)
  • M Mitra et al.

    Sarcoptes scabiei in animals spreading to man

    Trop Geogr Med

    (1993)
  • B Heilesen

    Studies on Acarus scabiei and scabies

    Acta Derm Venereol

    (1946)
  • K Mellanby

    The development of symptoms, parasitic infection and immunity in human scabies

    Parasitology

    (1944)
  • K Mellanby

    The transmission of scabies

    Br Med J

    (1941)
  • JS McCarthy et al.

    Scabies: more than just an irritation

    Postgrad Med J

    (2004)
  • AM Downs et al.

    The epidemiology of head lice and scabies in the UK

    Epidemiol Infect

    (1999)
  • E Lonc et al.

    Scabies and head-lice infestations in different environmental conditions of Lower Silesia, Poland

    J Parasitol

    (2000)
  • MS Green

    Epidemiology of scabies

    Epidemiol Rev

    (1989)
  • JK Kristensen

    Scabies and Pyoderma in Lilongwe, Malawi. Prevalence and seasonal fluctuation

    Int J Dermatol

    (1991)
  • BJ Currie et al.

    Scabies programs in Aboriginal communities

    Med J Aust

    (1994)
  • JR Andrews et al.

    Scabies and pediculosis in Tokelau Island children in New Zealand

    J R Soc Health

    (1989)
  • K Mellanby

    Epidemiology of scabies

  • J Heukelbach et al.

    Epidemiology and morbidity of scabies and pediculosis capitis in resource-poor communities in Brazil

    Br J Dermatol

    (2005)
  • D Mimouni et al.

    Seasonality trends of scabies in a young adult population: a 20-year follow-up

    Br J Dermatol

    (2003)
  • WP Herrmann et al.

    Jahreszeitliche Morbiditätsschwankungen bei der Scabies (Seasonal morbidity variation in scabies)

    Hautarzt

    (1969)
  • J Christophersen

    The epidemiology of scabies in Denmark, 1900 to 1975

    Arch Dermatol

    (1978)
  • JR Andrews

    Scabies in New Zealand

    Int J Dermatol

    (1979)
  • Y Tuzun et al.

    The epidemiology of scabies in Turkey

    Int J Dermatol

    (1980)
  • AM Downs

    Seasonal variation in scabies

    Br J Dermatol

    (2004)
  • A Buczek et al.

    Epidemiological study of scabies in different environmental conditions in central Poland

    Ann Epidemiol

    (2005)
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