Mites in house dust and human allergoses

The literary data on the study of the house-dust mites during the period from 1864 till 1983 are given. The methods of the house dust samples collection in flats and the methods of the house-dust mites isolation from the house dust are evaluated. The house-dust mites fauna including more than 130 species is described. The synantropic mites-pyroglyphides are the main part of the fauna, the stored products mites and predatory cheyletid and gamasid mites occur regularly. The rest part of the fauna consists of the different mites got into house by chance. The literary data on the influence of temperature and relative humidity on the development and growth of the mite population are given. The house-dust mites feeding and digestion processes bearing relation to the formation of the mite allergen are reviewed. The original data complete the literary data on the fauna and distribution of the house-dust mites in Moscow.     

House-dust mites allergen for specific immunotherapy by oral administration: experimental study

The oral medicinal form of house-dust allergen has been prepared with the use of new technology. To produce the preparation, the standard water-saline extract obtained from house-dust mites (Dermatophagoides farinae) allergen has been used. This preparation is chemically stable and does not lose its biological activity for 2 - 3 years of storage. The microbiological purity of the allergen meets the requirements for oral preparations. The allergen has proved to be safe in cases of prolonged administration and has no chronic toxicity. As shown with the use of immunochemical methods, the preparation has high immunogenicity and lower allergenicity. This preparation may be recommended for clinical trials on a limited circle of subjects.     

Quantitative determination of Der p I allergen levels in allergenic extracts and house-dust samples

Summary House-dust mites are responsible for serious respiratory diseases in humans. An ELISA assay to detectDermatophagoides pteronyssinus (Dp) mites has been set up. This assay, based on quantitative determination of the majorDp allergen, called Der p I, has been applied for the analysis of growing mite cultures and house-dust samples.Der p I allergen levels in mite cultures are well correlated with the number of mites present as well as with the biological activity of the corresponding extracts. Different methods for detectingDp mites in house-dust samples were compared. The ELISA method shows good sensitivity and specificity, and is particularly suitable for routine analyses.     

Dampness,mites and respiratory allergy

Summary This paper reviews the relationships between humidity, house-dust mites and respiratory allergy. In vitro relationship between relative humidity and house-dust mite growth are quite clear cut. In real conditions also, there is a significant association between relative humidity and the presence of live mites. The relevance of house-dust mites for respiratory allergy lies on clinical, physiopathological and mostly on epidemiological data. The latter demonstrate a correlation between exposure to mites and risk of sensitization and development of overt allergic diseases. Lastly, humidity of dwellings is linked to respiratory allergy. These results should lead to building safer dwellings for allergic subjects, or modifying existing dwellings. In this respect, emphasis should be put on a proper ventilation rate and also a proper behaviour of inhabitants in order to minimize humidity production.     

The determination of allergen-specific IgE and IgG antibodies in patients sensitized to the house dust mite Dermatophagoides pteronyssinus

45 patients, hypersensitive to house-dust mites, were examined by the method of skin tests to D. pteronyssinus allergen. Besides, in their blood sera the levels of allergen-specific IgE antibodies were determined in the radioallergosorbent test and allergen-specific IgG antibodies, in the enzyme immunoassay. These tests revealed that in 91% of the patients the results of skin tests were positive, in 68% an elevated level of specific IgE antibodies and in 93% of the patients an elevated level of specific IgG antibodies were detected. All patients showed the positive result in one of the above-mentioned tests. The largest group of the patients (55%) included persons showing the positive result of the skin test and having elevated levels of allergen-specific IgG and IgE antibodies. Thus, in cases of hypersensitivity to house-dust mites the levels of allergen-specific IgG and IgE antibodies in the patients' blood sera should be determined.     

House-dust mite sensitivity among rural and urban asthmatics of West Bengal, India: a comparison

House-dust mite allergy is a fairly common problem in West Bengal among individuals sensitive to dust inhalation. House-dust mites belonging to the genusDermatophagoides are abundant in the homes of asthmatic patients residing in urban as well as rural areas of West Bengal. The frequency of positive skin reaction to different dust-related allergens tested was higher (χ²=5.4777, df = 1;P < 0.05) among patients of urban areas compared with that among the patients of rural areas. Urban patients showed more frequent skin reaction towards cockroach allergen, while rural patients are more sensitive to hay-dust allergen and these are very much related to their local environmental conditions. Analysis of radioallergosorbent test (RAST) results against house dust (HD) and mites reveal that 73 and 90% patients of both urban and rural areas responded positively towardsDermatophagoides pteronyssinus (DP) andDermatophagoides farinae (DF) antigens, respectively. The present study indicates no significant difference in house-dust mite sensitivity and mite levels in homes among the rural and urban asthmatics of West Bengal, India as evidenced from the results of analysis of dust samples, allergy skin test and detection of mite-specific IgE antibodies by RAST.     

Use of the indirect hemagglutination inhibition reaction for evaluating the specific activity of allergens

To evaluate the specific activity of house-dust allergen, the passive hemagglutination inhibition test was used. Nine commercial batches of house-dust allergen were studied by means of this test. The results of the determination of the activity of house-dust allergen in the passive hemagglutination inhibition test, the skin tests and the indirect mast-cell degranulation test were in good correlation.     

Identification of house-dust mites

The term house-dust mite usually refers to those species of the mite family Pyroglyphidae, that are known to commonly occur, although sometimes regionally, in the dust of human dwellings. These species belong to five genera:Dermatophagoides, Euroglyphus, Hirstia, andMalayoglyphus. Related species ofDermatophagoides have the most world-wide occurrence, the commonest being:D. farinae, D. microceras, andD. pteronyssinus. A correct taxonomic identification of house-dust mites is very important, not only from a biological stand point, but also regarding the consequences of their respective allergenical properties. Several immuno-chemical studies revealed differences between the products of two hard to distinguish sibling species. A preliminary practical taxonomic key for the most common and important house-dust mites is presented.     

Protein chips for detection of mite allergens using Kunitz-type protease inhibitors

Stored-food and house-dust arthropods include many species of mites and beetles that affect human health. For diagnostic tests proteases such as trypsin are utilized as they are indicators of the presence of allergen contaminants in food. We recently characterized Kunitz-type protease inhibitors (KPIs) from Solanum palustre. Here we studied biotechnological applications of KPI-B1 and -B4. We manufactured a protein chip with immobilized KPI-B1 and -B4 and showed trypsin/chymotrypsin-binding specificity, indicating that the recombinant proteins have protease selectivity. We employed the protein chip to capture mite proteins belonging to the protease family with polyclonal anti-mite antibodies. The mite diagnostic chip can be useful for detecting mite allergens.     

Penetration of light into carpet, and responses of the European house-dust mite (Dermatophagoides pteronyssinus) to varying light intensity and diurnal cycle

This study examined the question of what effect exposure to light might play in determining the vertical distribution of house-dust mites in carpet, and the degree to which light penetrates worn and unworn carpets of different pile conformation (loop- versus cut-pile), height and colour. The effect on population increase of a diurnal lighting cycle versus continual darkness was also investigated. It was found that the penetration of light into carpets was largely unaffected by pile colour or conformation. Pile height was an important factor, however, and for a given height within the pile, light intensity was higher in carpets subjected to a greater degree of wear. This corresponded to the reduction in effective pile height that occurs with carpet use. Whilst the differences observed were sometimes large (up to two-fold for a given height within the pile), Petri dish studies suggested no mite preference for habitation of areas of low light intensity compared to high intensity. Additionally, culturing mites under a diurnal light cycle was shown to be no more efficient than culturing in complete darkness. These results suggest that exposure to light is not an important determinant of house-dust mite behaviour, or their ability to colonise textile substrates.     

Population growth and allergen accumulation of Dermatophagoides farinae cultured at 20 and 25 °C

House dust mites are cultured to obtain mite allergen material to produce allergen extracts (vaccines) for diagnostic tests, immunotherapy, and research purposes. Research laboratories and manufacturers have their own culturing protocols to grow these mites and these may vary between manufacturers and between research laboratories. The temperature at which mites are cultured may influence the allergen composition, allergen ratio of Der 1: Der 2 and endotoxin levels in the extracts produced from these cultured mites. In order to produce standardized and uniform extracts, across the industry and in various research laboratories, the influence of culture conditions must be understood. Here we determined how temperature affects mite population growth rates, dynamics of allergen production, Der f 1: Der f 2 ratio and endotoxin levels in extracts made from Dermatophagoides farinae mites cultured at 20 and 25 °C. We found that Der f 1 and Der f 2 accumulated exponentially in the cultures with Der f 1 accumulating faster than Der f 2. When the live mite populations peaked, the ratios for Der f 1: Der f 2 were 4.1 and 4.7 for cultures reared at 20 and 25 °C, respectively. Most of the Der f 1 and Der f 2 allergen in whole cultures is not in mite bodies and is lost when the mite material is washed. Thus, if the ratio of Der f 1 and Der f 2 is an important consideration for commercial and research extracts, then the temperature at which the mites are cultured and the collection procedure are important considerations.     

Introduction

Conclusion The editor and authors contributing to this special issue ofExperimental and Applied Acarology, which is dedicated to Professor Alex Fain, have compiled a very complete collection of articles about the various aspects of the allergenic house-dust mites. The result is a valuable document, worth the dedication to the acarologist who since November 1964 has contributed so much to our knowledge of the Pyroglyphidae.     

Assessment of the specific activity of commercial allergen preparations made of house dust in the bacteriosorption reaction: a comparison with the results of the radioallergosorbent inhibition test

The activity of the commercial batches of house-dust (HD) allergens was compared in the inhibition of the radioallergosorbent test (RAST) and in the direct bacteriosorbent test (BST), detecting IgG to the antigens by adsorption on the complexes of whole staphylococcal cells containing protein A. BST was made with rabbit antiserum to HD allergen. This antiserum inhibited RAST by 76% and, therefore, contained antibodies to most of the allergenic determinants of HD. At the same time, no significant correlation between the activity of 15 batches of HD allergen was revealed in RAST inhibition and in BST with the above antiserum. Nevertheless, the exhaustion of the antiserum with a batch of HD allergen showing low activity in RAST inhibition, but high activity in BST made it possible to obtain BST results significantly correlating with the data resulting from RAST inhibition in two series of experiments.     

Seasonal abundance of xerophilic fungi and house-dust mites (Acarida: Pyroglyphidae) in mattress dust

Summary Arthropods and xerophilic fungi in dust from 5 mattresses and air-borne fungi were identified and counted every 4 weeks from January 1976 to October 1977.The arthropod fauna consisted mainly of the pyroglyphid mites Dermatophagoides pteronyssinus (58%) and Euroglyphus maynei (30%). The fungal flora consisted of Aspergillus restrictus (48%), A. glaucus (16%), Wallemia sebi (3%) and Penicillium spp. (25%). Air-borne fungi belonged to the same taxa but in different frequencies, 30, 7, 21 and 27%, respectively. Mattresses differed in quantities of mites and Penicillium.In July 1977, the highest population density of pyroglyphid mites was encountered: 69 specimens/g of dust. In the same month the numbers of A. restrictus rose significantly, reaching a maximum of 3.8×10⁴ diaspores/g of dust. Most air-borne fungi were isolated in the winter period of 1976/1977. No positive correlation was found between the numbers of air-borne and mattress-dust fungi. The summer of 1976 was exceptionally dry resulting in both a premature decline of the mite populations and a low level of A. restrictus diaspores.The seasonal peaks of A. restrictus and pyroglyphid mites correspond and suggest a synergistic cooperation which may result in an increased house-dust allergen production in the environment of asthmatic patients.Supported by grant no. 230 of the Dutch Asthma Foundation     

Effects of five insect growth regulators on laboratory populations of the North American house-dust mite,Dermatophagoides farinae

The potential of insect growth regulators (methoprene, hydroprene, fenoxycarb, diflubenzuron and triflumuron) to control populations of the North American house-dust miteDermatophagoides farinae (Hughes) was assessed in laboratory bioassays. Methoprene was most effective at suppressing population growth, especially at concentrations of 1.0% (10 000 ppm) and 5.0% (5000 ppm) active ingredient. Hydroprene, structurally related to methoprene, also suppressed house-dust mite populations but not as consistently as methoprene. Fenoxycarb may be effective at controlling house-dust mites but at greater concentrations than were tested. Diflubenzuron and triflumuron, two chitin-synthesis inhibitors, failed to suppress mite numbers and may, in fact, stimulate reproduction in some cases. Almost all concentration of the insect growth regulators were shown to be ineffective when assayed 90 days after treatment.     

Intensity of parasitic mite infection decreases with hibernation duration of the host snail

Temperature can be a limiting factor on parasite development. Riccardoella limacum, a haematophagous mite, lives in the mantle cavity of helicid land snails. The prevalence of infection by R. limacum in populations of the land snail Arianta arbustorum is highly variable (0-78%) in Switzerland. However, parasitic mites do not occur in host populations at altitudes of 1290 m or higher. It has been hypothesized that the host's hibernation period might be too long at high elevations for mites and their eggs to survive. To test this hypothesis, we experimentally infected snails and allowed them to hibernate at 4°C for periods of 4-7 months. Winter survival of host snails was negatively affected by R. limacum. The intensity of mite infection decreased with increasing hibernation duration. Another experiment with shorter recording intervals revealed that mites do not leave the host when it buries in the soil at the beginning of hibernation. The number of mites decreased after 24 days of hibernation, whereas the number of eggs attached to the lung tissue remained constant throughout hibernation. Thus, R. limacum survives the winter in the egg stage in the host. Low temperature at high altitudes may limit the occurrence of R. limacum.     

Clinical Significance of Skin Reactions to Mite Extracts in Children with Asthma

The mite Dermatophagoides pteronyssinus has been identified in dust from the houses of children in Birmingham suffering from asthma. Skin tests were carried out on 150 asthmatic children with extracts of D. pteronyssinus, of the related species D. farinae, of other mites found in house dust, and of crude house dust. Though positive reactions to D. pteronyssinus were obtained more frequently and were of greater size than those to the other extracts, it was considered that D. farinae is a suitable substitute for D. pteronyssinus for skin testing.In further tests on 302 asthmatic children with mite extracts and with extracts of allergens obtained commercially reactions to the former extracts were much more common than reactions to the latter.Major skin reactions (weals with diameter of 5 mm. or more) were present in 77% of children with a history of perennial asthma and house-dust sensitivity. Hence allergy to house-dust mites, particularly D. pteronyssinus, is of considerable importance in childhood asthma, and further study of the ecology and control of the mites in dust is desirable.     

The effect of sub-floor heating on house-dust-mite populations on floors and in furniture

It is well known that dehydrating conditions for house dust mites can be created by simply raising the temperature, causing loss of body water and eventually death. Thus, it can be expected that conditions for dust mites are less favourable on floors supplied with sub-floor heating. This was examined in a study of 16 houses with sub-floor heating and 21 without. The pattern of changes in air humidity and temperature on the floors was investigated and compared to known data of the tolerance of dust mites. Also the resident mite populations were compared. Floors with sub-floor heating had, on average, fewer mites, but the difference with unheated floors was small. It was remarkable that mite numbers were also lower in upholstered furniture. Another important observation was that some houses with sub-floor heating had high mite numbers, indicating that this type of heating is compatible with a thriving mite population. Temperature and humidity conditions of heated floors may allow mites not only to survive, but also to remain active in winter. A moderate increase in temperature, a moderate decrease inf (absolute) air humidity, or a combination of both, will suffice to keep the humidity all winter below the Critical Equilibrium Humidity, the level of air humidity that is critical for mite growth and reproduction, hence for allergen production. However, it is argued that measures to suppress allergen production by house dust mites are likely to be far more effective if taken in summer rather than in winter. This revised version was published online in July 2006 with corrections to the Cover Date.     

Population growth and allergen accumulation of <Emphasis Type="Italic">Dermatophagoides pteronyssinus</Emphasis> cultured at 20 and 25°C

The house dust mites, Dermatophagoides pteronyssinus and D. farinae are cultured commercially and in research laboratories and material is harvested from these cultures to make extracts that are used for diagnosis, immunotherapy and research. Temperature and other climatic conditions can influence population growth rates, dynamics of allergen production, and the associated endotoxin, enzyme and protein levels of the mite material harvested from these cultures. Here we determined how temperature affected these parameters. Dermatophagoides pteronyssinus was cultured at 20 and 25°C at 75% relative humidity, and at 2-week intervals the concentrations of mites, Der p 1 and Der p 2 allergens, endotoxin, and selected enzymes were determined. Mite density increased exponentially but growth rate and final population density were greater at 25°C compared to 20°C. The combined allergen (Der p 1 + Der p 2) concentrations accumulated in the cultures at about the same rate at both temperatures. However, individual Der p 1 and Der p 2 accumulation rates varied independently at the two temperatures. Der p 1 accumulated faster at 20°C whereas Der p 2 accumulated faster at 25°C. The amount of Der p 1 in whole cultures was greater than the amount of Der p 2. The concentration of allergen for washed mites harvested from the cultures was much less than for the whole cultures. Our study demonstrated that temperature is an important factor in population growth and the dynamics of allergen production in cultured mites.     

Positive correlation of trophic level and proportion of sexual taxa of oribatid mites (Acari: Oribatida) in alpine soil systems

We investigated community structure, trophic ecology (using stable isotope ratios; ¹⁵N/¹⁴N, ¹³C/¹²C) and reproductive mode of oribatid mites (Acari, Oribatida) along an altitudinal gradient (2,050–2,900 m) in the Central Alps (Obergurgl, Austria). We hypothesized that (1) the community structure changes with altitude, (2) oribatid mites span over four trophic levels, (3) the proportion of sexual taxa increases with altitude, and (4) the proportion of sexual taxa increases with trophic level, i.e. is positively correlated with the δ¹⁵N signatures. Oribatid mite community structure changed with altitude indicating that oribatid mites occupy different niches at different altitudes. Oribatid mites spanned over 12 δ¹⁵N units, i.e. about four trophic levels, which is similar to lowland forest ecosystems. The proportion of sexually reproducing taxa increased from 2,050 to 2,900 m suggesting that limited resource availability at high altitudes favors sexual reproduction. Sexual taxa more frequently occurred higher in the food web indicating that the reproductive mode is related to nutrition of oribatid mites. Generally, oribatid mite community structure changed from being decomposer dominated at lower altitude to being dominated by fungal and lichen feeders, and predators at higher altitude. This supports the view that resources from dead organic material become less available with increasing altitude forcing species to feed on living resources such as fungi, lichens and nematodes. Our findings support the hypothesis that limited resource accessibility (at high altitudes) favors sexually reproducing species whereas ample resource supply (at lower altitudes) favors parthenogenetic species.