IgE antibodies to house dust mite in patients with scabies

Of 135 patients with scabies, forty-seven (35%) had a positive (Classes 1–4) radioallergosorbent test (RAST) to Dermatophagoides pteronyssinus (DP). Elevated serum IgE concentrations were found in sixty-one (45%) of the patients. Atopic disease was confirmed in twenty-eight (23%) of the 120 patients who completed a medical questionnaire satisfactorily. In a control group, well-matched for age and sex, of 201 employees at a local bank, only four (2%) had a positive RAST to DP, and eight (4%) had raised serum IgE levels. Atopic disease was confirmed in eighteen (9%) of them. These observations indicate that scabies infection stimulates the production of IgE antibodies, even in non-atopic individuals, and may suggest that IgE antibodies against the human pathogenic mite Sarcoptes scabiei cross-react with DP. Scabies infection in addition often seems to be associated with atopic disease.     

Human infestation by Sarcoptes scabiei var. bovis (cattle itch mite)

Infestation by Sarcoptes scabiei var. bovis in a farmer is reported. He presented with an intensely itching eruption of erythematous papules on forearm, neck and abdomen. An environmental investigation yielded that four of the farmer's cows had mange. Sarcoptes scabiei var. bovis was isolated from skin-scrapings of the cows. Histology from a self-induced lesion revealed that Sarcoptes scabiei var. bovis penetrates the human skin, but does not--in contrast to var. hominis--form burrows. This finding corresponds with the clinical picture. The mite lies subcorneally, compressing the thinned epidermis. The surrounding corneal tissue shows a marked exsudative reaction. The various ways in which mites may infest the human skin are discussed.     

Behaviour of Sarcoptes scabiei in its burrow in hyperkeratotic scabies. A scanning electron microscopic study

The behaviour of Sarcoptes scabiei var. hominis has been studied in the skin of 2 patients with hyperkeratotic scabies. After examination under the scanning electron microscope, the skin specimens can be reprocessed for light microscopic examination. Original aspects and the dynamics of the burrowing parasite are presented, namely its penetration into the epidermis, the elimination of digestive residues and the maturation of the parasite's eggs.     

Scanning electron microscopy of the scabies burrow and its contents, with special reference to the Sarcoptes scabiei egg

An entire burrow of a female Sarcoptes scabiei (var. hominis) mite was examined by scanning electron microscopy during serial transverse sectioning. The elevated roof and the wall were composed of compacted corneocytes. The floor had a smooth surface except at the anterior end. Here it was made up of nucleated stratum granulosum cells, etched in appearance, presumably having been chewed by the mite. The female mite, the larvae, scybala, and eggs were also examined. The ultrastructure of the eggshell surface revealed it to have a distinctive geometric patterning. Cross-sectioning showed this shell or chorion to be composed of an outer layer of minute, closely packed penta- and hexahedrons resting on a thin inner homogenous layer. The polyhedric surface pattern was exactly replicated in the cement substance which attached the egg to the burrow floor. Observations were made on the embryonic positioning which permitted the larvae to emerge from the eggshells in a uniform manner.     

The seasonality of scabies morbidity and the fertility of the itch mite Sarcoptes scabiei de Geer as an index of the activity of a population of the causative agent

The authors analyze the features of the epidemic process in scabies and review foreign and Soviet literature on the seasonal pattern of this condition. They have introduced the mite fertility index, that is determined by the number of eggs in the mite burrow, counted with the use of a new laboratory diagnostic technique with lactic acid. The studies have revealed that this index is high in September-December (11.5 +/- 1.0 - 12.6 +/- 1.3) and much lower in January-July (8.9 +/- 1.1 - 6.0 +/- 0.6). Another finding was that some females were in a latent state from December to July, when oogenesis was arrested and therefore the agent population activity dropped. The results have demonstrated regular seasonal changes in S. scabiei reproductivity, coinciding with the disease phenology; besides social and communal factors, these regularities also contribute to the epidemiology of scabies.     

Commercial availability of a house dust mite patch test.

The house dust mite long has been studied for its potential role in atopic dermatitis. Its part in the pathogenesis of asthma and allergic rhinitis has been studied and is accepted. Testing for the dust mite allergen in this arena is performed with radioallergosorbent tests (RASTs) and prick testing. For several reasons, including the lack of a standardized testing tool, the difficulty in removing dust from the environment and the lack of association of dust and skin disease by patients, the role of the house dust mite in the pathogenesis of atopic dermatitis and skin disease has been questioned. Chemotechnique Diagnostics (Malmo, Sweden) now provides a standardized dust mite allergen in petrolatum in 2 concentrations. Dermatophagoides mix is a 50:50 mix of Dermatophagoides pteronyssinus and D. farinae at concentrations of 20% and 30%. The availability of a standardized patch test allergen for the house dust mite provides a better tool to investigate the role of this allergen as a contactant.     

Atopic dermatitis, house dust mite allergy and month of birth

An analysis of the month of birth in 210 patients with atopic dermatitis and a positive prick test towards the house dust mite (Dermatophagoides pteronyssinus) showed a significantly higher prevalence of birth in the interval May to November when compared with the expected distribution (p less than 0.01). A subdivision of the AD patients due to the concomitant presence of asthma showed no differences as the relative risk was nearly the same in the two subgroups. This observation indicates that a consistent seasonal preference of birth in patients with atopic dermatitis only applies to the skin disease and not to coexistent asthma.     

Scanning electron microscopic observation of Sarcoptes scabiei var. hominis

Scanning electron microscopy of Sarcoptes scabiei var. hominis was carried out on a single mite. The ultrastructural morphology of Sarcoptes is illustrated.     

Biological behavior of Sarcoptes scabiei var. suis in swine epidermis. A scanning electron microscopy study in hyperkeratotic (or Norwegian) scabies of swine

The behaviour of Sarcoptes scabiei var. suis has been studied in hyperkeratotic scabies of pigs (fig. 1). The scanning electron microscope enabled us to observe the outer surface of the eggs in the burrow and even within the cut body of the fertilized female mite (fig. 2). Early events during hatching of the eggs and the first steps of the newborn larva (fig. 3) are shown. The presence of crystals containing calcium and phosphate is shown to occur in places where huge amounts of faecal material are collected (fig. 4). Although some of these aspects have not been published previously we observed many similarities in behavior between Sarcoptes scabiei var. hominis and suis in their respective hosts affected with hyperkeratotic scabies. As to the therapeutic aspect of scabies in humans, carefully selected drugs currently used in the systemic treatment of scabies in pigs would be worth a trial in patients difficult to treat.     

A study of the role of house dust mite in atopic dermatitis

Subjects with positive skin-prick tests to house dust mite (HDM) solution, including those with and without atopic dermatitis, participated in a double-blind, controlled study of the role of HDM exposure in the pathogenesis of atopic dermatitis. HDM solution and diluent control were applied daily to mildly eczematous or clinically uninvolved skin of the antecubital or popliteal fossae, without prior abrasion, for 5 days. Responses were assessed by a clinical grading system and by measurement of area of dermatitis; pruritus was recorded on visual analogue scales. The clinical grading system showed that marked or moderate delayed local reactions developed in one third of patients with atopic dermatitis in response to HDM application to both mildly eczematous and clinically uninvolved skin. Relative to control sites, significant increases in area of dermatitis and degree of pruritus were also recorded in response to HDM application to mildly eczematous sites. Application of HDM solution to normal, unabraded skin of prick test positive subjects without a history of dermatitis, produced pruritus and immediate urticarial responses which were not seen at control sites, findings which demonstrate that HDM antigen may be rapidly absorbed in normal skin. Application of vehicle or antigen solution to which subjects were negative on prick testing, produced no significant local reactions. This study provides objective evidence for a role for cutaneous HDM exposure in the pathogenesis of atopic dermatitis.     

Increase in skin mast cells following chronic house dust mite exposure

Application of inhalant allergens in high concentration to the mildly abraded skin of sensitive patients with atopic dermatitis gave rise to eczematous skin responses at 48 h. These lesions, infiltrated by basophils, eosinophils and mononuclear cells, are examples of cutaneous basophil hypersensitivity. Repeated application of allergen induced an increase in skin mast cells by 6 days, the mast cell hyperplasia replacing the earlier basophil infiltration. No electron microscopic evidence of mast cell heterogeneity among the recruited cells was found.     

Mechanisms for a novel immune evasion strategy in the scabies mite sarcoptes scabiei: a multigene family of inactivated serine proteases

Parasitic infestation of the skin by the mite Sarcoptes scabiei is a significant problem worldwide, particularly in socially disadvantaged communities. A multigene family of at least 24 homologs of a serine protease allergen have been identified in S. scabiei. Surprisingly, the products of all but one of these genes are predicted to be catalytically inactive, due to mutations at a critical triad of amino acids at the active site. We discuss the possibility that these genes for inactivated proteases have been conserved because they mediate a novel host defense evasion strategy that the mite has evolved as an adaptation to parasitism of the epidermis. The identification of this family, and elucidation of its value to the parasite, may present an unanticipated approach to protective vaccination.     

Patch tests with house dust mite antigens in atopic dermatitis patients: methodological problems.

Patch tests with house dust mite allergens were performed in 21 atopic dermatitis patients with a positive prick test and RAST for house dust mite. Variables in methodology of patch testing, i.e. allergen concentration, application time, and intensity of tape stripping, were studied. Tests were performed with Dermatophagoides pteronyssinus solutions containing 20X, 100X and 500X the prick test concentration and purified HDM antigen: 10 and 50 micrograms/ml P1Ag solution. The series was applied on 8X or 15X tape-stripped and clinically normal skin on the back during 24 and 48 h. Non-specific reactions due to tape stripping, fixation tape or patch test occlusion were frequently observed: after 15X tape-stripping in 3/7 (24-h application) and 6/7 (48-h application) patients, after 8X tape-stripping in 2/19 (24-h application) and 8/19 (48-h application) patients. Reactions clinically assessed as specific occurred in 6/21 (29%) atopic dermatitis patients, 4/6 occurring in the 10 patients with a serum IgE greater than 1000 kU/l. High allergen concentrations and 48 h of application increased the number of patients with specific reactions. If 15X tape-stripping had been omitted, 2/3 patients tested in this manner and showing specific test reactions would have been negative. Further conclusions regarding the value and the preferable method of patch testing with atopic allergens require an in vitro control test.     

Effect of house dust mite avoidance measures in children with atopic dermatitis

BACKGROUND: House dust mite allergens are associated with atopic dermatitis (AD). OBJECTIVES: The aim of our study was to verify if house dust mite allergen avoidance measures can improve the clinical manifestations of AD in children. METHODS: Forty-one children (mean age 3.9 years) affected by AD associated with high total and/or specific IgE serum levels ('extrinsic' AD) were recruited. Clinical evaluation was performed utilizing the Severity Scoring of AD (SCORAD) index; dust was sampled from the children's beds and tested using an enzyme-linked immunosorbent assay. The study was planned in two parts. In the first part, a placebo-controlled trial of 2 months duration, mite allergen avoidance measures (encasing mattresses and pillows; a weekly hot wash of bedding; frequent vacuum cleaning of living room and bedroom; soft toys and carpets regularly cleaned or removed; no pets allowed) were recommended to group A patients, but not to group B. In the second part of the study, environmental avoidance measures were recommended to initial control group B patients also. One year after the start of the study the amounts of mite allergen in the home and clinical score of AD were measured in both groups. RESULTS: At the end of the first part of the study, significant decreases in major allergens of Dermatophagoides pteronyssinus (Der p1) and D. farinae (Der f1) load (from 393 to 94 ng m-2) and concentration (from 1.84 to 0.73 microg g-1 of dust) in children's beds were observed in treatment group A. At the same time, in this group the mean SCORAD index improved significantly (from 33 to 26; P = 0.022). After 12 months, when all patients had used allergen avoidance measures, Der p1 + Der f1 load, concentration and clinical score had improved, reaching similar values in both groups. CONCLUSIONS: Simple mite allergen avoidance measures should be recommended to families with children affected by extrinsic AD in order to control the clinical manifestations and prevent mite sensitization.