Phylogenetic relationships, stage-specific expression and localisation of a unique family of inactive cysteine proteases in Sarcoptes scabiei.

BACKGROUND: Scabies is worldwide one of the most common, yet neglected, parasitic skin infections, affecting a wide range of mammals including humans. Limited treatment options and evidence of emerging mite resistance against the currently used drugs drive our research to explore new therapeutic candidates. Previously, we discovered a multicopy family of genes encoding cysteine proteases with their catalytic sites inactivated by mutation (SMIPP-Cs). This protein family is unique in parasitic scabies mites and is absent in related non-burrowing mites. We postulated that the SMIPP-Cs have evolved as an adaptation to the parasitic lifestyle of the scabies mite. To formulate testable hypotheses for their functions and to propose possible strategies for translational research we investigated whether the SMIPP-Cs are common to all scabies mite varieties and where within the mite body as well as when throughout the parasitic life-cycle they are expressed. RESULTS: SMIPP-C sequences from human, pig and dog mites were analysed bioinformatically and the phylogenetic relationships between the SMIPP-C multi-copy gene families of human, pig and dog mites were established. Results suggest that amplification of the SMIPP-C genes occurred in a common ancestor and individual genes evolved independently in the different mite varieties. Recombinant human mite SMIPP-C proteins were produced and used for murine polyclonal antibody production. Immunohistology on skin sections from human patients localised the SMIPP-Cs in the mite gut and in mite faeces within in the epidermal skin burrows. SMIPP-C transcription into mRNA in different life stages was assessed in human and pig mites by reverse transcription followed by droplet digital PCR (ddPCR). High transcription levels of SMIPP-C genes were detected in the adult female life stage in comparison to all other life stages. CONCLUSIONS: The fact that the SMIPP-Cs are unique to three Sarcoptes varieties, present in all burrowing life stages and highly expressed in the digestive system of the infective adult female life stage may highlight an essential role in parasitism. As they are excreted from the gut in scybala they presumably are able to interact or interfere with host proteins present in the epidermis.

Scabies.

Scabies infestation in humans is a complex interplay between mite, host, and host environment. New techniques for diagnosis, treatment, and eradication are constantly in flux due to varying presentations of scabetic eruptions, a dearth of especially sensitive and specific measures for diagnosis, resistances to pharmacologic therapy, and disparate regional resources. This review will provide an update on the clinical variations, detection methods, and management options.

Escabiosis: importancia diagnóstica del examen directo / Scabies: diagnostic significance of direct examination

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Sarcoptes scabiei var. hominis: three-dimensional structure of a female imago and crusted scabies lesions by X-ray micro-CT.

The three-dimensional structure of scabies mites (Sarcoptes scabiei var. hominis) and keratin layers affected by crusted scabies lesions were obtained using X-ray computed tomography at sub-micrometer and micrometer resolution, respectively (X-ray micro-CT). Clear three-dimensional images including internal structure of scabies mites were obtained. Utilizing reconstructed micro-CT data, the sections of the capitulum (head part), digestive organs, and legs are shown. The reconstructed capitulum shows a jaw-like structure capable of penetrating the keratin layer of the skin. The tip of the forelegs of female scabies mites has a flat disk structure that may be used to grasp the skin surface. The keratin layer of a crusted scabies lesion spontaneously exfoliated from a patient was also reconstructed by the X-ray micro-CT technique. Extracted sections from CT data revealed a network structure of tunnels made by scabies mites with numerous larvae and eggs inside the tunnels.

Problems in diagnosing scabies, a global disease in human and animal populations.

Scabies is a worldwide disease and a major public health problem in many developing countries, related primarily to poverty and overcrowding. In remote Aboriginal communities in northern Australia, prevalences of up to 50% among children have been described, despite the availability of effective chemotherapy. Sarcoptic mange is also an important veterinary disease engendering significant morbidity and mortality in wild, domestic, and farmed animals. Scabies is caused by the ectoparasitic mite Sarcoptes scabiei burrowing into the host epidermis. Clinical symptoms include intensely itchy lesions that often are a precursor to secondary bacterial pyoderma, septicemia, and, in humans, poststreptococcal glomerulonephritis. Although diagnosed scabies cases can be successfully treated, the rash of the primary infestation takes 4 to 6 weeks to develop, and thus, transmission to others often occurs prior to therapy. In humans, the symptoms of scabies infestations can mimic other dermatological skin diseases, and traditional tests to diagnose scabies are less than 50% accurate. To aid early identification of disease and thus treatment, a simple, cheap, sensitive, and specific test for routine diagnosis of active scabies is essential. Recent developments leading to the expression and purification of S. scabiei recombinant antigens have identified a number of molecules with diagnostic potential, and current studies include the investigation and assessment of the accuracy of these recombinant proteins in identifying antibodies in individuals with active scabies and in differentiating those with past exposure. Early identification of disease will enable selective treatment of those affected, reduce transmission and the requirement for mass treatment, limit the potential for escalating mite resistance, and provide another means of controlling scabies in populations in areas of endemicity.

Sarcoptic mange in free-ranging pampas foxes in the Gran Chaco, Bolivia.

Sarcoptes scabiei infestation was diagnosed in two freshly dead free-ranging pampas foxes (Pseudalopex gymnocercus) in the Gran Chaco, Bolivia. Diagnosis was made based on histologic evaluation of skin biopsies and identification of the parasite from skin scrapings. Characteristic gross lesions consistent with mange were noted in 19 of 94 observations of free-ranging pampas foxes in the region from December 1998 to January 2000. None of 16 crab-eating foxes (Cerdocyon thous) observed during the same time period had visible lesions consistent with scabies. These are the first case reports of S. scabiei in pampas foxes.

Lice and scabies. Myths and reality.

Scabies mites are only distantly related to human lice. Nevertheless, the two groups have much in common as regards to structure and life-style. These similarities result from the two groups using parallel adaptations in order to solve some of the problems of being parasites. Understanding these adaptations may help us give better advice.

Coexistence of an unusual form of scabies and lepromatous leprosy. A case report.

A case of unusual crusted (Norwegian) scabies involving the entire skin of a 26 year old Brazilian patient with lepromatous leprosy is reported. The more prominent histopathological findings were acanthosis, hyperkeratosis and crusting with many mites of Sarcoptes scabiei. In the dermis, numerous foamy histiocytes filled with abundant acid-fast bacilli were seen.

The role of mast cells in treatment of scabies.

OBJECTIVE: The purpose of this study was to recognize the role of mast cells in the pathogenesis of scabies. METHODS: One hundred and fifty patients and 10 controls were included in the study. Group 1 included 20 patients without previous treatment. In group 2, 80 patients were treated with antiscabietic drugs. Group 3 had 50 patients who received an antiscabietic drug followed by 3 days of crotamiton. Diurnal and nocturnal skin biopsies were taken from group 1. In groups 2 and 3, the biopsies were taken after 2 weeks of treatment. Sections were cut and stained by hematoxylin and eosin and Giemsa stains. RESULTS: Mast cells were increased in diurnal and nocturnal biopsies. Evident degranulation of mast cells was detected in nocturnal biopsies. The mast cell number decreased to half its pretreatment number in patients treated with antiscabietic drugs and to its normal number in patients treated with antiscabietic drugs followed by 3 days with crotamiton. CONCLUSION: The number of mast cells are increased in scabietic lesions. This plays a role in the pathogenesis of the clinical and histologic picture of scabies. We recommend that an antiscabietic drug should be followed by 3 days of crotamiton in the treatment of scabies.

Introduction of a fluorescence-microscopic technique for the detection of eggs, egg shells, and mites in scabies.

A technique using the fluorescence microscope can prove helpful in the laboratory diagnosis of scabies. Specimens from fifteen patients with scabies were used in this study. All of the specimens were embedded with glycerine instead of potassium hydroxide (KOH) solution. The specimens were examined at 0 min, 30 min, 1 hr, 6 hrs, 24 hrs, and one week after mounting under light and fluorescence microscopes. Specimens embedded with non-fluorescent glycerine were not clear immediately after mounting but became so after about 1 hr. Eggs and egg shells were easily counted in the specimens under the fluorescence microscope but were very hard to identify under the light microscope. Mites were absent in half of the specimens; only eggs and egg shells were present in those specimens found by the fluorescence microscope. The above findings suggest that the detection of egg shells by the use of fluorescence microscope may be helpful for the diagnosis of scabies, in particular with mite negative specimens. Slides prepared with non-fluorescent glycerine were more stable and could be preserved for a long time. However, this method is time-consuming and requires expensive equipment.

[The variability of the itch mite Sarcoptes scabiei de Geer (Acariformes, Sarcoptidae) in relation to scabies epidemiology. 3. The geographical and seasonal variability]. / Izmenchivost' chesotochnykh kleshchei Sarcoptes scabiei de Geer (Acariformes, Sarcoptidae) v sviazi s épidemiologiei chesotki. Soobshchenie 3. Geograficheskaia i sezonnaia izmenchivost'.

The statistical modes of individual variability of Sarcoptes scabiei females, developed and described by the authors in two previous papers, has been used to analyze the geographic, seasonal variability and to compare the mite populations with due consideration for the clinical features of the disease. Statistically significant differences in the size and proportion of the samples were found in Moscow, the Moscow region, and the town of Bishkek in spring and summer. A relationship was revealed between the degree of the female back chetoid cover joining and the disease duration, number of burrows in the skin integument and their sites.

[The variability of the itch mite Sarcoptes scabiei De Geer (Acariformes, Sarcoptidae) in connection with the epidemiology of scabies. A rank system for the variability of the chaetoid integument in females]. / Izmenchivost' chesotochnykh kleshchei Sarcoptes scabiei De Geer (Acariformes, Sarcoptidae) v sviazi s épidemiologiei chesotki. Rangovaia sistema izmenchivosti khetoidnogo pokrova samok.

The variability of the naked section of the chaetoid cover of itch mite Sarcoptes scabiei De Geer females was studied. The sample used was divided into 5 grades by the number of undeveloped chaetoids. The structures surrounding the naked section, its size and dimensions of the female body were analysed in each grade of specimens. Such grade scale for describing the chaetoid cover proved to be useful for comparative analysis of human and animal forms of itch mite.