Diagnostic value of the molecular detection of Sarcoptes scabiei from a skin scraping in patients with suspected scabies

Scabies in infants and children - a narrative review

Scabies is a human ectoparasitosis caused by Sarcoptes scabei var. hominis. World-wide around 300 million patients are affected. Infants and children have the highest incidence rates. Poverty and overcrowding are social factors contributing to a higher risk of transmission and treatment failure. The leading symptom of the infestation is itch. Complications are bacterial infections that are responsible for mortality. Diagnosis is clinical. Non-invasive imaging technologies like dermoscopy can be used. Polymerase chain reaction (PCR) is less sensitive and specific than microscopy of skin scrapings. Treatment of choice is topical permethrin 5%. Ivermectin is the only oral drug FDA-approved for scabies. It should be used in cases non-responsive to topical therapy and in case of high number of infested patients in addition to topical therapy. Pseudo-resistance to treatment is not uncommon. New drugs are on the horizon. What is Known: • Pruritus is the leading symptom causing sleep disturbances and scratching with the risk of secondary bacterial infections. • Treatment failure is related to inappropriate application of topical drugs and asymptomatic family members. What is New: • COVID-19 pandemic and migration are contributing to an increased incidence of scabies. • New compounds to treat scabies are on the horizon.

Sight the Mite: A Meta-Analysis on the Diagnosis of Scabies

This meta-analysis was performed to assess the efficacy of the diagnostic tests for scabies infections that are currently in wide use. Scabies is most commonly diagnosed through clinical presentations; however, due to the wide array of symptoms, diagnosis is difficult. The most commonly used diagnostic test is skin scraping. However, this test relies on correctly selecting the site of mite infection for sampling. Due to the mobile nature of a live parasitic infection, the mite can often be missed based on its current location within the skin. The goal of this paper is to determine if a gold standard confirmatory test exists for the diagnosis of scabies by comparing Skin Scraping, Adhesive Tape, Dermoscopy, and PCR tests. Medline, PubMed, and Neglected Tropical Diseases databases were utilized in a literature review. Eligible papers were papers published in or after the year 2000, published in the English language, and mainly focused on the diagnosis of scabies. At the time of this meta-analysis, scabies is mostly diagnosed through a correlation of clinical symptoms in conjunction with diagnostic tests such as dermoscopy (sensitivity: 43.47%, specificity: 84.41%), adhesive tape tests (sensitivity: 69.56%, specificity: 100%) and PCR antigen detection (37.9% sensitivity, specificity: 100%). Due to a scarcity of data in the literature, the diagnostic efficacy of other diagnostic tests is difficult to assess. Overall, the efficacies of the tests analyzed vary depending on how similar scabies is to other skin disorders, how challenging it is to get a usable sample and the price and accessibility of essential tools. There is a need for standardized national diagnostic criteria to increase the diagnostic sensitivity of scabies infection.

Prevalence and molecular characterization of Sarcoptes scabiei from vicuñas (Vicugna vicugna) from Southern Peruvian Andes

Sarcoptic mange is a disease caused by an infectious parasite in the vicuñas (Vicugna vicugna) from South America. Although molecular studies have provided much information about the epidemiology of this disease, this information is still unknown in vicuñas. This study determined the prevalence and molecular characterization of Sarcoptes scabiei from vicuñas from Southern Peruvian Andes. During the 2018 shearing season, 181 vicuñas were clinically evaluated for lesions compatible with mange. Sarcoptes scabiei was detected in 35 (19.3%) vicuñas, and 50 mites from 25 vicuñas were selected for molecular analyses of the mitochondrial (cox1) and nuclear (ITS2) genetic markers. Molecular analyses of the cox1 and ITS2 sequences showed an identity of 94–99% and 99.8–100% with previous S. scabiei sequences registered in the GenBank, respectively. Sequence polymorphisms were more evident in the ITS2 than in the cox1, but only the cox1 had an association with the host. Phylogenetic analysis of S. scabiei cox1 sequences from vicuñas showed a cluster with S. scabiei cox1 sequences from canids, suggesting that the origin of S. scabiei from vicuña is associated with canid mites. This research is the first molecular analysis of S. scabiei from vicuñas. Future molecular studies will be necessary to determine the species variety, geographic segregation and host–parasite adaptation for this vicuña's mite.

State-of-the-Art Techniques for Diagnosis of Medical Parasites and Arthropods

Conventional methods such as microscopy have been used to diagnose parasitic diseases and medical conditions related to arthropods for many years. Some techniques are considered gold standard methods. However, their limited sensitivity, specificity, and accuracy, and the need for costly reagents and high-skilled technicians are critical problems. New tools are therefore continually being developed to reduce pitfalls. Recently, three state-of-the-art techniques have emerged: DNA barcoding, geometric morphometrics, and artificial intelligence. Here, data related to the three approaches are reviewed. DNA barcoding involves an analysis of a barcode sequence. It was used to diagnose medical parasites and arthropods with 95.0% accuracy. However, this technique still requires costly reagents and equipment. Geometric morphometric analysis is the statistical analysis of the patterns of shape change of an anatomical structure. Its accuracy is approximately 94.0-100.0%, and unlike DNA barcoding, costly reagents and equipment are not required. Artificial intelligence technology involves the analysis of pictures using well-trained algorithms. It showed 98.8-99.0% precision. All three approaches use computer programs instead of human interpretation. They also have the potential to be high-throughput technologies since many samples can be analyzed at once. However, the limitation of using these techniques in real settings is species coverage.

Laboratory-based diagnosis of scabies: a review of the current status

Scabies is a neglected tropical disease (NTD) of the skin that is caused by the mite Sarcoptes scabiei. It is considered to be an important public health problem in many regions. The disease is at its most prevalent in low-resource countries where there are overcrowded living conditions coupled with poor hygiene. In some regions, mass drug administration using ivermectin is a key population-based approach to the control of scabies. Before starting a patient on specific treatment, confirming the diagnosis by accurate and rapid identification of the organism is critical. Different laboratory-based techniques for scabies have been developed in the last few decades. These include direct microscopy and histopathology. More recently, serological testing, dermoscopy and different molecular techniques have been developed as diagnostic methods for scabies. To date, none of these, apart from microscopy and dermoscopy, has been translated into routine clinical laboratory practice. A simple point-of-care or laboratory test would provide a rapid and confirmed diagnosis and early institution of effective treatment. In this review we present an update on the laboratory techniques currently in use for the identification of scabies.

Development of a rapid scabies immunodiagnostic assay based on transcriptomic analysis of Sarcoptes scabiei var. nyctereutis

Scabies is a highly contagious skin disease caused by the mite Sarcoptes scabiei that affects many mammals. However, the sensitivity of traditional tests for scabies diagnosis in humans is less than 50%. To simplify the diagnosis of scabies, methods that are simple, sensitive, specific, and cost-effective are required. We developed an immunodiagnostic test based on S. scabiei var. nyctereutis RNA-seq data collected from Japanese raccoon dogs with sarcoptic mange. Three candidate antigens-a highly expressed hypothetical protein "QR98_0091190," another mite allergen known as "SMIPP-Cc," and an abundant "vitellogenin-like protein"-were evaluated by western-blot analysis. A lateral flow immunoassay, using specific antibodies against the vitellogenin-like protein, successfully detected scabies in the skin flakes of S. scabiei-infected raccoon dogs. This assay can potentially diagnose scabies more accurately in wildlife, as well as in humans.

[Scabies-Renaissance of an ectoparasite infection : Diagnosis and therapy-How to proceed in practice]

Scabies or mange is currently a common dermatosis in Germany and other countries, and should be more important in health policy. It affects a cross-section of society, including all age groups, from infants to the aged. Locals and people with a migration background both suffer from this highly contagious ectoparasite infection with excessive, predominately nocturnal itching. Clinical diagnosis represents a challenge for the experienced dermatologist due to the variety of dermatosis to be considered in the differential diagnosis. It is still unclear whether treatment failure or the recurrences observed everywhere are due to in vitro and in vivo resistance of the pathogen agent Sarcoptes scabiei against permethrin or ivermectin. Therapeutic errors seem to play a role as often not all direct contact persons are recorded and treated with antiscabious treatment. They form the reservoir for reinfections. In the event of repeated nonresponse to topical (permethrin) and/or oral antiscabious treatment, alternative topical preparations-benzyl benzoate or crotamiton-should be used. Combination with ivermectin is mandatory.