Scabies: Advances in Noninvasive Diagnosis

Prevalence of Nail Scabies: A French Prospective Multicenter Study

INTRODUCTION

To assess the prevalence of nail involvement in children <16 years old with a confirmed diagnosis of scabies.

STUDY DESIGN

Observational, prospective study in 7 French dermatology departments between June 2015 and January 2017. Children were included if they had scabies confirmed by dermoscopy and/or microscopy and if nails could be sampled. The first toenails and thumbnails as well as clinically affected nails were systematically sampled for microscopic examination. Individual data were recorded via a standardized questionnaire.

RESULTS

A total of 47 children with scabies were included (26 females [55.3%], mean age 3.6 ± 4.0 years). Pruritus was present in 42 children (89.3%); the relapse rate was 38.3% (n = 18). In 3 infants (6.4%), Sarcoptes mites were revealed by dermoscopy or microscopy of the first toenails (2 cases) and a thumbnail (1 case), but nails were normal in 2 children. Two of the 3 infants had already received treatment for scabies in the previous weeks.

CONCLUSION

Prevalence of nail involvement in children with confirmed scabies was 6.4%. Nails should not be overlooked during scabies treatment.

Scabies, crusted (Norwegian) scabies and the diagnosis of mite sensitisation

Scabies is observed with relatively high frequency in Allergy and Dermatology clinics in developing countries where poor sanitary conditions are prevalent and increasingly in some areas of the world with increased immigrant populations. Since the immunological response to scabies mites includes the production of IgE class antibodies to Sarcoptes scabiei allergens which cross-react with Dermatophagoides major allergens Der p 1 and Der p 2, positive immediate-type skin tests to house dust mite extracts should be interpreted cautiously. Additionally, scabies should be included routinely in the differential diagnosis of itchy rashes in patients living in those areas.

Molecular characteristics and serodiagnostic potential of chitinase-like protein from Sarcoptes scabiei

Scabies, caused by the mite Sarcoptes scabiei, is an allergic skin disease that affects millions of people and other mammals worldwide. This highly contagious parasitic disease is among the top 50 epidemic disease and is regarded as a neglected tropical disease. Diagnosis of scabies is difficult in the early stage, and the pathogenesis of scabies is not currently clear. Here, we expressed, identified and located the chitinase-like protein of S. scabiei (SsCLP), and evaluated its potential as an early-stage diagnostic antigen for rabbit scabies. Indirect ELISA using recombinant SsCLP (rSsCLP) exhibited diagnostic sensitivity of 94.4% (17/18) and specificity of 86.7% (26/30). Early diagnostic test after artificial infection of rabbits with S. scabiei for 1 week showed a positive detection rate of 96.7% (29/30). Immunolocalization assays showed that fluorescence signals were localized on the surface of mites and, in infected rabbits, were observed in keratinized skin and embedded mites. Intradermal skin tests of rabbits by injecting rSsCLP showed a wheal, flare and erythema reaction. These results suggest that S. scabiei chitinase-like protein is conducive to host invasion, participates in inducing the allergic response of the host, and is an effective antigen for the diagnosis of S. scabiei.

Ignoring the "Itch": The Global Health Problem of Scabies

Infestation with Sarcoptes scabiei var. hominis is a common human parasitic affliction endemic in tropical developing countries. Scabies is transmitted by close person-person contact, and outbreaks have been reported in reception centers for asylum seekers. Scabies presents clinically as extremely pruritic excoriated papules and linear burrows in the skin. This infestation predisposes to bacterial skin infections that can result in serious complications affecting the kidneys and possibly the heart. Treatment of individuals with scabies and their close contacts involves the use of antiparasitic agents. First-line treatment is topical 5% permethrin cream. Community mass drug administration, followed by active case finding with targeted treatment, is a promising approach that can reduce the prevalence of both scabies and bacterial skin infections. Organizations such as the International Alliance for the Control of Scabies are advocating for the development of integrated disease control strategies in an effort to decrease scabies infestation worldwide.

Scabies masquerading as bullous pemphigoid: scabies surrepticius

Scabies, a parasitic infestation caused by the mite Sarcoptes scabiei, is diagnosed by observing either the mite, its ova, or its excrement. The mite tracts, known as burrows and a characteristic presentation of the pruritic condition, are typically found on the web spaces between the fingers. Other cutaneous lesions include excoriated papules, pustules, and vesicles. However, atypical clinical variants of scabies, such as bullous, crusted, hidden, incognito, nodular, and scalp forms of the parasitic infestation, mimic the morphologic features of other non-parasitic dermatoses. A 76-year-old man presented with pruritic blisters and urticarial plaques that demonstrated not only pathology changes, but direct immunofluorescence also showed findings of bullous pemphigoid. His condition improved, but did not resolve, with topical corticosteroid cream for the management of the primary autoimmune blistering disorder. When other family members subsequently developed scabies, the correct diagnosis for his condition, bullous scabies, was established by demonstrating mites, ova, and scybala on a mineral oil preparation from a skin scraping of a newly appearing burrow. Bullous scabies can masquerade not only clinically, but also both pathologically and immunologically as bullous pemphigoid. Scabies serrupticius is introduced as a unifying term to designate all of the non-classic presentations of S. scabiei mite infestation.

Severe impact of sarcoptic mange on the movements and space use for one of its most important vector species, the raccoon dog

Sarcoptic mange is a highly contagious zoonotic skin disease that can have severe effect on population dynamics of many wild mammals. However, very little is known about its effect on the activity and space use of infected animals. In this study we equipped two raccoon dogs (Nyctereutes procyonoides) in a mange outbreak area with radio-collars and observed the spatial and temporal effects of sarcoptic mange to these individuals. Initially, the raccoon dogs had no external symptoms of mange infection, but developed these during the study period. One of the raccoon dogs died just 32 and the other 52days after collaring. During a relatively short period before their death, there was an abrupt and drastic decline in their home range size. For one of the animals it started about 1 month before its death and the home range size reduced >1000×, whereas for the other raccoon dog it took place within the last week, decreasing >200×. The daily covered distances also declined considerably. These results indicate that at the later stage sarcoptic mange affected the physiological state of the diseased animals so forcefully that made them almost immobile. Our results show for the first time how rapid and severe could the impact of sarcoptic mange be for one of its most important reservoir and vector species.