Search

Laboratory and field studies on the use of liquid nitrogen as an acaricide, combined with vacuum cleaning, demonstrated this inert freezing agent to be extremely efficient in reducing the number of live mites in mattresses when compared to vacuum cleaning only. Preliminary observations suggest this treatment does no physical damage to mattresses. Any strategy in the control of house dust mites should incorporate procedures both for the reduction of the mite population and the removal of the allergen pool of faecal pellets and dead mites. [ABSTRACT FROM AUTHOR]

Background: Control of dust mites using extremes of temperature is an alternative to the use of acaricides. In the past we have attempted control by freezing with liquid nitrogen. The present paper deals with the opposite extreme, the use of steam. Objective: To assess the feasability and effectiveness of a domestic steam cleaner for the control of dust mites, its effect on mite populations and concentrations of the allergen Der p I. Methods: A domestic stream cleaner was used to treat carpet squares that had been seeded in the laboratory with known numbers of dust mites (Dermatophagoides pteronysinnus). The number of live mites was monitored for a period of 4 months in eight treated carpet squares and eight controls. Dust samples were taken from 12 standardized areas of carpet in a tenement flat in Glasgow, UK, before and after steam cleaning treatment, and the concentration of allergen Der p I was compared with 12 adjacent, control areas. Results: No live mites were found at any time in the treated carpet squares, whereas in the control squares geometric mean mite population density rose from 11 after 3 days to 39 after 1 month, 66 after 2, 122 after 3 and 185 after 4 months. There was a mean reduction of 86.7% in Der p 1 concentration (3.3–.0.44 &mu/g) compared with a reduction of 4.7% (2.22–2.116 μg/g) in control areas, a difference that was statistically significant at the 5% level. Conclusion: These data indicate that steam cleaning has considerable potential as an highly effective and efficient method of killing dust miles and reducing concentrations of Der p 1 in domestic premises. [ABSTRACT FROM AUTHOR]

The median relative density of house dust mite populations was determined in mattresses in the homes of 23 people with atopic dermatitis (AD) who were mite-sensitive. It was significantly higher (total mites [dead and live] 174/0.1 g of dust; live mites 45.5/0.1g) than in those of 23 healthy non-atopics (total mites 52/0.1 g; live mites 7.5/0.1 g; P<0.05, <0.01, respectively; Mann-Whitney U-test). There was no significant difference between mite population densities in mattresses in damp homes (n = 27; total mites 188/0.1 g; live mites 36/0.1 g) and those in homes with no damp (n = 19; total mites 116/0.1 g; live mites 26/0.1 g). These data demonstrate a clear association between AD and exposure to large numbers of mites, independent of the presence of domestic damp. People with AD were exposed to densities of > 500 mites/0.1 g of mattress dust five times more frequently than nonatopics, corresponding to a relative risk of 25.0, but were exposed to densities of ≤ 50 mites/0.1 g five times less frequently. The overall relative risk for AD, with a cutoff of 50 mites (total)/0.1 g, was 8.1. There was an obvious positive correlation between magnitude of exposure and frequency of disease. It is hypothesized that the association between high densities of mites and AD is related to differences in lipid composition of the shed squames on which the mites feed; those of people with AD may be of greater nutritional value than those of non-atopics, thus enhancing mite population growth. [ABSTRACT FROM AUTHOR]

In a controlled clinical trial, patients with atopic dermatitis carried out house dust mite eradication procedures on their mattresses, using natamycin or a matched placebo spray, with or without vacuum cleaning, for 4 months. For the two groups that used vacuum cleaning, mite numbers fell significantly both by comparison of mean initial and final numbers and by calculating mean rates of reduction from regression analyses (P < 0.01 in all cases). There were no differences between the groups in the magnitude of the decreases. For the two groups that did not use vacuum cleaning, mite populations remained virtually unchanged. These results indicate vacuum cleaning not natamycin had the major effect on mite eradication. Mean symptom scores of patients in all four groups were slightly reduced by the end of the trial, but there was a greater reduction rate (P < 0.01) in the combined scores of the groups that did not use vacuum cleaning, demonstrating a lack of correlation between improvement in clinical score and lowered mite numbers. No patients entered remission and the maximum improvement in clinical score was only 47%. Natamycin and vacuum cleaning neither alone nor in combination proved valuable in reducing mite numbers sufficiently to provide clinical benefit. [ABSTRACT FROM AUTHOR]

Twenty one adult patients with asthma, with positive skin test responses to the European house dust mite, Dermatophagoides pteronyssinus, were randomly allocated to a control group or to a group applying house dust mite avoidance measures. These included an initial application of liquid nitrogen to mattresses and bedroom carpets to kill the live house dust mite population. Histamine airway responsiveness, symptom scores, peak expiratory flow rates (PEF), and house dust mite numbers were determined during the two week pretrial and eight week trial periods. Nine patients in each group completed the study. By the end of the study there was a significant reduction in live mites in the "avoidance" group but not in the control group. The avoidance group showed a significant improvement in symptom scores measured on a linear analogue scale, in the number of hours each day spent wheezing (mean reduced from 8.6 to 4.5 hours), and in PEF (l/min) both in the morning (from 364 to 388) and in the evening (from 368 to 392). These changes were not found in the control group. The provocative concentration (PC) of histamine causing a 20% fall in FEV1 (PC20FEV1) had increased significantly in the avoidance group at eight weeks (from 0.58 to 2.3 mg/ml), whereas no change was seen in the control group (from 0.93 to 1.21 mg/ml). These results show that house dust mite avoidance, combined with initial killing of the mite by liquid nitrogen, diminishes airway responsiveness and improves asthma symptom control over an eight week period in adult asthmatic patients with house dust mite allergy. [ABSTRACT FROM PUBLISHER]

. Glasgow's mild, high-rainfall climate, combined with a deteriorating quality of housing and low standards of living in many parts of the city, makes it a particularly suitable place for thriving populations of house dust mites. The acarofauna in 124 samples of house dust from beds and carpets in seventy-four homes in Glasgow, Scotland, comprised thirty-one species of which the most abundant were Dermatophagoid.es pteronyssinus (Trouessart) (64.3%), Glycyphagus domesticus (De Geer) (16.7%), Euroglyphus maynei (Cooreman) (11.6%), Tarsonemus sp. (1.6%), Cheyletus eruditus (Schrank) (1.5%), C.trouessarti Oudemans (0.9%), Tarsonemus fusarii Cooreman (0.8%) and Glycyphagus destructor (Schrank) (0.7%). Mites were present in all the homes surveyed and the mean population density was found to be 97/100 mg of dust (range 2-1210). Over 47% of homes visited showed signs of disrepair associated with damp, especially unmodernized flats in old tenement buildings and 1960s council housing stock, many of which contain deprived occupants. There was a high incidence of hygrophilic species such as Glycyphagus spp., Tarsonemus spp. and Euroglyphus maynei in such homes. Samples from homes of atopic asthmatics were found to contain significantly fewer mites than those from normal volunteers (x2=54.7). This was partly due to the use of house dust mite avoidance measures (e.g. regular vacuum cleaning of mattresses as well as carpets) by some of the asthmatics. [ABSTRACT FROM AUTHOR]

Raised levels of serum IgE antibodies to prawn antigens were found in 15 of 26 seafood factory process workers with respiratory symptoms and in one of 26 case-matched asymptomatic controls (P < 0.001). Raised lgG antibody titres against the same antigens were found in 18 subjects in each symptom grouping and the median titres of this antibody did not differ significantly between the groups. The prawn-specific IgE antibody response was significantly associated with atopy (IgE antibody response to common allergens) and with a history of cigarette smoking, confirmed by level of serum cotinine, a major nicotine metabolite. Non-atopic non-smokers were unlikely to become sensitized. The titre of the prawn-specific IgE antibody correlated with the duration of exposure and with the duration of' symptoms. Discriminant analysis of the serological profile (anti- prawn IgE, total IgE and cotinine) was sufficient to assign individuals correctly into symptomatic or asymptomatic categories in 77% of subjects. The titres of the IgE and IgG antibody responses to prawn antigens did not correlate, and the main factor which seemed to determine the antibody isotype response to these inhaled antigens was cigarette smoking. IgE antibody was produced mainly by smokers, whereas IgG antibody was the predominant isotype produced by non- smokers. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which is concerned with the proteolysis of human lgG by house dust mite allergens

This article focuses on the airborne allergens in house dust. Dust mites and domestic pets are sources of the most common airborne allergens in the home to which people with atopy are exposed and become sensitised. Successful control of airborne allergens in the home offers the prospect not only of alleviating symptoms of atopic asthma, rhinitis and eczema but also, by reducing pre-sensitisation exposure in the environment of infants at risk of inheritance of atopy, may prevent (or delay) sensitisation and onset of disease.

The presence of the enzymatically active allergens equivalent to Der p I (cysteine protease), Der p III (serine protease) and amylase in extracts of Dermatophagoides pteronyssinus, D. farinae and Euroglyphus maynei was determined using appropriate enzymatic techniques. Biochemical equivalents of all three allergens were present in each extract studied. Studies also showed that the mite extracts contained a variety of other biochemically active enzymes including trypsin, chymotrypsin, carboxypeptidase A and B, glucoamylase and lysozyme. Marked differences in the relative concentrations of some of these enzymes in different mite extracts were observed, particularly trypsin and carboxypeptidase A. The enzymes were physicochemically similar to equivalent enzymes from vertebrate and invertebrate sources. Chromatofocusing studies of faecal extracts derived from D. pteronyssinus and D. farinae showed that several isoforms of each enzyme were present. The data indicated that there were more trypsin isoforms, with pI over a wider range, in extracts prepared from D. pteronyssinus. Proteases and carbohydrases were also found in extracts prepared from faecally enriched material suggesting that they were endoperitrophic and associated with mite digestion. The data suggest that not only are the group I, III and amylase allergens a consistent feature of most pyroglyphid dust mites but also that other proteases and carbohydrases present in mite faeces are allergenic.

A rapid, sensitive, chemiluminescent immunoblotting method was used to identify IgE-binding components of Dermatophagoides pteronyssinus and Euroglyphus maynei that were recognized by sera of 16 D. pteronyssinus-sensitive patients with atopic dermatitis. Some 28 components (14-200 kD) were found in the D. pteronyssinus extract, and sera bound between 1 and 13 of them (mean 6.0). At least one of four components (97, 28, 24 and 14 kD) were bound by 14/16 sera. E. maynei had 25 components (14-227 kD), 13 in common with those of D. pteronyssinus by molecular size. Sera bound between 1 and 11 of them (mean 5.2) and 14/16 sera bound 1 of 38 kD (unique to E. maynei) and/or 1 of 175 kD. There were positive correlations between the number of D. pteronyssinus and E. maynei components bound and anti-D. pteronyssinus and E. maynei serum IgE values (p less than 0.001 in both cases) and between the number of D. pteronyssinus and E. maynei components bound and total serum IgE values (p less than 0.01 in both cases). These results demonstrate a very considerable diversity of IgE antibody responses to domestic mite allergens amongst patients with atopic dermatitis.

The acarofauna and Der p I allergen concentrations in dust samples from mattresses and lounge room carpets obtained from 20 homes from two coastal cities. Perth and Bunbury, were determined. All samples were shown to contain mites and the geometric mean numbers of total mites/g of mattress and carpet dust for Perth and Bunbury were 480 and 263, and 585 and 992, respectively. Carpets from both centres had a significantly (P less than 0.02) greater mean number of mite species (Perth 9.1, Bunbury 9.0) than mattresses (Perth 5.2, Bunbury 5.7). The predominant mite species were D. pteronyssinus, E. maynei and Tarsonemus spp. D. farinae was found to be absent from all dust samples examined. E. maynei was present in the 10 Bunbury homes and in 50% of the Perth homes, ranging from 0 to 81% of mites identified. The arithmetic mean Der p I concentrations in the mattresses and carpets in Perth and Bunbury were 4.2 and 4.1, and 3.8 and 9.2 micrograms/per gram of fine dust, respectively, and Der p I concentration correlated with mite counts (r = 0.75; P less than 0.001). The concentration of Der p I equivalent per 100 mites was 1.5 micrograms. The data are consistent with the view that asthmatic patients in Western Australia have significant exposure to a variety of house dust mites and that E. maynei may be clinically significant.