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.
SeminarScabies
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
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2023, American Journal of Infection ControlCitation Excerpt :People who are immunocompromised, old, and debilitated are more easily to acquire crusted scabies.1,5 Typical symptoms include skin lesions such as papules, burrows, and rash.2,6 It can also cause severe pruritus.2,6