Scabies is a neglected tropical disease caused by the ectoparasitic mite, Sarcoptes scabiei var. hominis (S. scabiei). Common scabies, the most prevalent clinical subtype of scabies, is characterized by pruritus, multiple skin lesions and low mite burden. In contrast, crusted scabies, an extremely contagious variant, is characterized by hyperkeratosis and high mite burden, with or without pruritus. Scabies can be diagnosed based on clinical manifestations, with confirmation obtained through microscopic identification of diagnostic features of S. scabiei. However, owing to the diversity and non-specific nature of its clinical manifestations and insufficient knowledge regarding early-stage clinical manifestations, the diagnosis of crusted scabies continues to be delayed. Herein, we present three cases of scabies with varying degrees of crusting and mite burden. Three patients with physical and microscopic results suggesting scabies were selected for this study. Case 1 had mild crusting and low mite burden, case 2 had severe crusting and high mite burden and case 3 had mild crusting and high mite burden. In this case report, ‘the initial stage of crusted scabies’ refers to the progression from common to crusted scabies. The discussion regarding the diagnostic characteristics of the initial stage of crusted scabies is expected to aid the early diagnosis of crusted scabies.

Scabies outbreaks cause significant morbidity and disruption in aged care facilities and other institutional settings. Failure to manage scabies outbreaks may be attributable to low awareness amongst healthcare workers. A survey was distributed to healthcare workers across aged care facilities in South-East Queensland, Australia. The survey captured demographics, prior scabies experience, knowledge-based questions, and attitudes. Scabies was common in aged care facilities, with 41% of 128 respondents encountering the disease while working in aged care. Participants demonstrated sound theoretical knowledge regarding scabies (median knowledge score 82%). Scabies knowledge was not associated with years of experience in the sector or educational level but was associated with respondent age (p = 0.017). Knowledge gaps were evident regarding diagnosis, incubation periods, and treatment. Respondents demonstrated an inconsistent ability to identify atypical clinical presentations of scabies, showing discordance between theoretical knowledge and its practical application. The ability to identify crusted scabies was low, reflecting the high frequency of misdiagnosis of index cases in scabies outbreaks. Respondents considered scabies to be a problem and were supportive of improved management guidelines. These study outcomes will inform the design of accessible, targeted educational resources for scabies to help prevent and reduce the impact of outbreaks.

Optical microscopy is the gold standard technique used to confirm the diagnosis of scabies. Multiple diagnostic features of the pathogen Sarcoptes scabiei var. hominis (S. scabiei) can be identified under a microscope and classified into 3 categories: mites, eggs and fecal pellets. However, mite and eggshell fragments can also be observed, which have been ignored in the 2020 International Alliance for the Control of Scabies (IACS) Criteria and by most researchers. In this study, we propose a novel morphological classification method that classifies multiple diagnostic features into 5 categories and 7 subcategories. Our results revealed that 65.2% (1893 of 2896) of the positive cases were confirmed through the identification of mites, eggs or fecal pellets, whereas up to 34.6% (1003 of 2896) of the positive cases were confirmed through the identification of mite or eggshell fragments. Therefore, the important diagnostic values of mite and eggshell fragments should be emphasized. Importantly, for the first time, mite and eggshell fragments were classified into 7 subcategories, some of which are easily ignored or confused with contaminating artefacts. We believe that this novel morphological classification method will be beneficial for operator training in interpreting slides and in improving the 2020 IACS Criteria.

Scabies is a parasitic infestation with high global burden. Mass drug administrations (MDAs) are recommended for communities with a scabies prevalence of >10%. Quantitative analyses are needed to demonstrate the likely effectiveness of MDA recommendations. In this study, we developed an agent-based model of scabies transmission calibrated to demographic and epidemiological data from Monrovia. We used this model to compare the effectiveness of MDA scenarios for achieving scabies elimination and reducing scabies burden, as measured by time until recrudescence following delivery of an MDA and disability-adjusted-life-years (DALYs) averted. Our model showed that three rounds of MDA delivered at six-month intervals and reaching 80% of the population could reduce prevalence below 2% for three years following the final round, before recrudescence. When MDAs were followed by increased treatment uptake, prevalence was maintained below 2% indefinitely. Increasing the number of and coverage of MDA rounds increased the probability of achieving elimination and the number of DALYs averted. Our results suggest that acute reduction of scabies prevalence by MDA can support a transition to improved treatment access. This study demonstrates how modelling can be used to estimate the expected impact of MDAs by projecting future epidemiological dynamics and health gains under alternative scenarios.

Currently no national guidelines exist for the management of scabies outbreaks in residential or nursing care homes for the elderly in the United Kingdom. In this setting, diagnosis and treatment of scabies outbreaks is often delayed and optimal drug treatment, environmental control measures and even outcome measures are unclear. We undertook a systematic review to establish the efficacy of outbreak management interventions and determine evidence-based recommendations. Four electronic databases were searched for relevant studies, which were assessed using a quality assessment tool drawing on STROBE guidelines to describe the quality of observational data. Nineteen outbreak reports were identified, describing both drug treatment and environmental management measures. The quality of data was poor; none reported all outcome measures and only four described symptom relief measures. We were unable to make definitive evidence-based recommendations. We draw on the results to propose a framework for data collection in future observational studies of scabies outbreaks. While high-quality randomised controlled trials are needed to determine optimal drug treatment, evidence on environmental measures will need augmentation through other literature studies. The quality assessment tool designed is a useful resource for reporting of outcome measures including patient-reported measures in future outbreaks.

Scabies is a contagious skin infection commonly occurring in institutions such as care homes. However, a large proportion of vulnerable people in England receive domiciliary care in the community and their experience of scabies has not been described. We undertook a pragmatic cross-sectional survey of Health Protection Teams (HPTs) in England to determine the burden of scabies related to domiciliary care. Fifteen cases or outbreaks were notified to HPTs between January 2013 and December 2017. Although a relatively uncommon event for individual HPTs, they were complex to manage and required the co-ordination of multiple stakeholders. Diagnosis was often delayed and required several clinical consultations. A lack of guidance led to difficulties establishing stakeholder roles and responsibilities and sources of funding for treatment. The stigmatisation of scabies sometimes affected the quality of care provided to patients, such as use of excessive personal protective equipment. Our study demonstrates that scabies is an issue of public health importance for domiciliary care service providers and users, and research is required to better understand the impacts of the disease and to develop evidence-based guidance. More generally, there is a need for simpler treatment regimens and methods of diagnosing scabies.

Prevalence of skin sores and scabies in remote Australian Aboriginal communities remains unacceptably high, with Group A Streptococcus (GAS) the dominant pathogen. We aim to better understand the drivers of GAS transmission using mathematical models. To estimate the force of infection, we quantified the age of first skin sores and scabies infection by pooling historical data from three studies conducted across five remote Aboriginal communities for children born between 2001 and 2005. We estimated the age of the first infection using the Kaplan–Meier estimator; parametric exponential mixture model; and Cox proportional hazards. For skin sores, the mean age of the first infection was approximately 10 months and the median was 7 months, with some heterogeneity in median observed by the community. For scabies, the mean age of the first infection was approximately 9 months and the median was 8 months, with significant heterogeneity by the community and an enhanced risk for children born between October and December. The young age of the first infection with skin sores and scabies reflects the high disease burden in these communities.

Commonly thought of as a disease of poverty and overcrowding in resource-poor settings globally, scabies is also an important public health issue in residential care facilities for the elderly (RCFE) in high-income countries such as the UK. We compared and contrasted current local Health Protection Team (HPT) guidelines for the management of scabies outbreaks in RCFE throughout England. We performed content analysis on 20 guidelines, and used this to create a quantitative report of their variation in key dimensions. Although the guidelines were generally consistent on issues such as the treatment protocols for individual patients, there was substantial variation in their recommendations regarding the prophylactic treatment of contacts, infection control measures and the roles and responsibilities of individual stakeholders. Most guidelines did not adequately address the logistical challenges associated with mass treatment in this setting. We conclude that the heterogeneous nature of the guidelines reviewed is an argument in favour of national guidelines being produced.

Scabies outbreaks can be disruptive in institutional settings, and are associated with considerable but under-researched morbidity, especially in vulnerable populations. In this paper, we describe key findings from a retrospective review of scabies outbreaks reported in the literature over the past 30 years. We undertook this review to gain insights into the impact of institutional outbreaks, the burden in terms of attack rates, economic costs, treatment trends, the types of index cases and outbreak progression. We found 84 reports over 30 years, with outbreaks most frequently reported in aged care facilities (n = 40) and hospitals (n = 33). On average, scabies outbreaks persisted for 3 months, and the median attack rate was 38%. While 1% lindane was once the most commonly employed acaricide, 5% permethrin and oral ivermectin are increasingly used. Crusted scabies represented the index case for 83% of outbreaks, and scabies was misdiagnosed in 43% outbreaks. The frequency of reported scabies outbreaks has not declined consistently over time suggesting the disease is still highly problematic. We contend that more research and practice emphasis must be paid to improve diagnostic methods, surveillance and control, health staff education and management of crusted scabies to prevent the development of scabies outbreaks in institutional settings.

Scabies is an important public health problem in residential care homes. Delayed diagnosis contributes to outbreaks, which may be prolonged and difficult to control. We investigated factors influencing outbreak recognition, diagnosis and treatment, and staff experiences of outbreak control, identifying areas for intervention. We carried out a semi-structured survey of managers, affected residents and staff of seven care homes reporting suspected scabies outbreaks in southern England over a 6-month period. Attack rates ranged from 2% to 50%, and most cases had dementia (37/39, 95%). Cases were diagnosed clinically by GPs (59%) or home staff (41%), none by dermatologists. Most outbreaks were attributable to avoidably late diagnosis of the index case. Participants reported considerable challenges in managing scabies outbreaks, including late diagnosis and recognition of outbreaks; logistically difficult mass treatment; distressing treatment processes and high costs. This study demonstrates the need for improved support for care homes in detecting and managing these outbreaks.

Scabies is an infectious disease that is endemic in poorly resourced communities, and also common in industrialized countries. Although the disease, which is caused by infestation of Sarcoptes scabiei, is generally mild, the need for a vaccine against S. scabiei is proposed. The immunological mechanisms that control S. scabiei infection are discussed and the current status of scabies vaccine development reviewed. Future directions for scabies vaccine development are also addressed.

We have cloned a cDNA encoding a novel antigen from a Sarcoptes scabiei (Acari) cDNA library by immunoscreening with sera from S. scabiei-infected dogs. The antigen is encoded by a 2157 bp mRNA with a predicted open reading frame of 719 amino acids (molecular weight 79 kDa). Our sequence analysis identified the presence of a MADF domain in the N-terminus, and downstream of this domain there was a region of low sequence complexity. This latter region contained several blocks of triplets and quadruplets of polar amino acids (Asn, Gln and Ser), and these 3 amino acids represented 39·7% of all amino acids. The antigen was named Atypical Sarcoptes Antigen 1 (ASA1) since the MADF domain normally is found in proteins involved in transcriptional regulation. In addition, 15 out of 62 S. scabiei-infected dogs reacted with a purified recombinant version of ASA1 in Western blot analysis. With immunohistochemistry we could show that ASA1 is expressed throughout the parasite, and that IgG specific for ASA1 binds to the inside wall of the mite's burrow. To our knowledge, this is the first description of an antigen containing an MADF domain.

Sarcoptes scabiei is an important parasitic mite in both man and animals. Little is known about the molecular interactions between this pathogen and its host. This is in part explained by the paucity of mite-derived material, including antigens. To extend the knowledge of the molecular repertoire in S. scabiei, we have performed a gene survey by an expressed sequence tag (EST) analysis. A total of 1020 ESTs were generated from an S. scabiei cDNA library. The average sequence read was 510 bp after editing and the overall sequencing success was 89%. Clustering of the sequences resulted in 76 clusters, comprising 36% of the ESTs. Sequence similarity searches showed that almost half of the S. scabiei ESTs could be assigned a putative identity. Many of these transcripts shared similarity with genes involved in basic metabolism and cellular organization. In the data set we also identified several proteases and other types of potential allergens implicated in various disease mechanisms. A relatively large fraction of the ESTs coded for different proteins carrying protease inhibitor-like domains. The clones with no similarity to previously identified genes constituted 11% of our transcripts. The EST data generated in this study will be a valuable resource in further studies of the biology of S. scabiei and in the identification of genes that can serve as potential targets in the control of the parasite.

The burrowing mite Sarcoptes scabiei is the causative agent of the highly contagious disease sarcoptic mange or scabies. So far, there is no in vitro propagation system for S. scabiei available, and mites used for various purposes must be isolated from infected hosts. Lack of parasite-derived material has limited the possibilities to study several aspects of scabies, including pathogenesis and immunity. It has also hampered the development of high performance serological assays. We have now constructed an S. scabiei cDNA expression library with mRNA purified from mites isolated from red foxes. Immunoscreening of the library enabled us to clone a full-length cDNA coding for a 102.5 kDa protein. Sequence similarity searches identified the protein as a paramyosin. Recombinant S. scabiei paramyosin expressed in Escherichia coli was recognized by sera from dogs and swine infected with S. scabiei. We also designed a small paramyosin construct of about 17 kDa that included the N-terminal part, an evolutionary variable part of the helical core, and the C-terminal part of the molecule. The miniaturized protein was efficiently expressed in E. coli and was recognized by sera from immunized rabbits. These data demonstrate that the cDNA library can assist in the isolation of important S. scabiei antigens and that recombinant proteins can be useful for the study of scabies.