Abundance of domestic mites in dwellings of children and adolescents with asthma in relation to environmental factors and allergy symptoms.

Exposure to house dust allergens, mainly from domestic mites, is an important cause of allergic reactions in sensitized asthmatic patients. A total of 63 dust samples were collected from 16 flats in Bytom (south Poland); in each flat a person (age 4-17 years) suffering from bronchial asthma lived with his/her family. Mite density was calculated as the number of specimens per g of dust. The results were compared with household features and the data were statistically analyzed. In total 566 mite specimens were isolated, including 526 members of the family Pyroglyphidae (93%). The dominant species were Dermatophagoides pteronyssinus (60% of the total count) and Dermatophagoides farinae (32%). Pyroglyphids were found in all mite positive samples (68%) of which 35% also contained non-pyroglyphids, including glycyphagids, cheyletids and gamasids. The results suggest associations between the density of some mite taxa (per g of dust) and the following indoor environmental factors: presence of pets, number of inhabitants, coal-stoves as a type of heating, cleaning frequency, higher relative humidity, presence of flowers and PVC windows. The severity of asthma seems to be associated with the numbers of D. farinae, total domestic mites and live mites per g of dust.

Mite control effect of branched chain fatty acid on the house dust mite Dermatophagoides pteronyssinus.

House dust mites, Dermatophagoides pteronyssinus are present in the indoor environments, such as pillows and carpets. In this study, we investigated the mite control effect of branched chain fatty acids (2-ethylhexanoic acid (iso-C8), 2-butyloctanoic acid (iso-C12), isopalmitic acid (iso-C16) and their mechanism of action. These fatty acids showed a higher acaricidal activity than the straight chain fatty acids. Among these, iso-C12 had the highest acaricidal activity (LC50: 13mM) and more than 50% repellence rate at 0.20% (8.0mM) concentration. In the fumigant mortality bioassay, iso-C8 was 4 times more toxic than iso-C12 and isoC-16 in the gas phase. However, all branched chain fatty acids showed higher acaricidal activities on direct contact than fumigation. As the concentration of these fatty acids decreased, the number of deaths decreased and the number of escapes increased. There was no significant change in the mite epidermis due to contact with any of the fatty acids used. All branched chain fatty acids immobilized more than half of the mites within 90min of exposure. These results were consistent with the tendency of immobilizer type miticides targeting the respiratory system.

Feeding Interactions Between Microorganisms and the House Dust Mites Dermatophagoides pteronyssinus and Dermatophagoides farinae (Astigmata: Pyroglyphidae).

The feeding interactions between house dust mites (HDM) and microorganisms are key factors in the survival of mites in human environments. The suitability of different microbes for HDM is not known. Here, microbial species isolated from HDM cultures were offered to HDM in food preference tests under laboratory conditions. The microbial species were added to the rearing diet of mites to reach 7% of Saccharomyces cerevisiae and 10% of each tested microorganism. The suitability of each microbe-supplemented diet for Dermatophagoides pteronyssinus and Dermatophagoides farinae was compared in terms of mite population growth and mite preference in a cafeteria test. The effect of mite feeding on the respiration of microorganisms in the diet was observed in microcosms. HDM were able to feed and reproduce on some bacterial and fungal species, but the suitability of microbial species differed. Increasing the yeast Sa. cerevisiae in the diet from 7 to 17% appeared the most suitable for both mite species. Staphylococcus spp. bacteria were preferred for D. farinae and were suitable for reproduction. The population growth and feeding preferences of D. pteronyssinus and D. farinae with respect to microorganisms indicate that D. farinae can develop on a diet with bacterial (Staphylococcus nepalensis and Staphylococcus kloosii) additions, whereas D. pteronyssinus was successful on a diet with fungal (Aspergillus jensenii and Aspergillus ruber) additions. The bacteria Kocuria rhizophila and Bacillus cereus decreased population growth in D. pteronyssinus, whereas the yeasts Hyphopichia pseudoburtonii, Hyphopichia burtonii, and Candida ciferrii decreased population growth in D. farinae. These results indicate that some microorganisms are an important food source for HDM.

Storage mite concentrations are underestimated compared to house dust mite concentrations.

Dwellings are increasingly well insulated to save energy and this leads to higher humidity and temperature, which improves conditions for mites. Dermatophagoides antigens are the main allergens involved and tested in atopic asthma. We developed three new species-specific quantitative PCR (qPCR) methods for house dust mites (Dermatophagoides pteronyssinus and D. farinae) and storages mites (Acarus siro, Glycyphagus domesticus, Lepidoglyphus destructor). We sampled dust with electrostatic dust collectors, in the bedrooms, under beds and in the kitchens of patients with allergies (n = 24) and healthy controls (n = 18). Mite quantification was carried out with the three new qPCRs and the qPCR previously described for the Dermatophagoides genus. The qPCRs were highly specific and efficient for house dust mite species and the storage mites. Storage mite concentrations were higher than house dust mite concentrations and were higher in dwellings of patients with allergies. Consequently, allergists should test more often patients against the storage mite antigens by prick tests or IgE serology. Dampness is a major factor in storage mite development and the presence of effective mechanical ventilation can reduce storage mite concentrations four-fold. In addition, to limit exposure to dust mites, treatments should be used throughout dwellings and not only in patients' bedrooms.

Risk of exposure of a selected rural population in South Poland to allergenic mites. Part I: indoor acarofauna of one-family houses.

The aim of this study was to investigate the occurrence of mites in dust samples from houses in agricultural areas of South Poland, with particular reference to allergenic and parasitic species as a potential risk factor of diseases among people. A total of 250 dust samples from 50 single-family houses situated in Stryszawa and vicinity (Malopolskie province) were examined for the presence of domestic mites. Dust was taken from beds, floors in bedrooms, upholstery furniture, floors in family rooms and from floors in kitchens. Mites were found in 74.8% of samples collected. A total of 5340 mite specimens were isolated, including 2771 members of the family Pyroglyphidae (51.9%). Dominants were Dermatophagoides pteronyssinus (36.4% of all mites) and Gohieria fusca (25.1%), followed by Chortoglyphus arcuatus (18.3%) and D. farinae (15.1%). Dermatophagoides pteronyssinus was also the most frequent species (53.2% of the total count of samples examined), followed by G. fusca (42.4%), D. farinae (37.2%) and C. arcuatus (36.4%). Lepidoglyphus destructor was found more frequently than Glycyphagus domesticus in the examined samples. Density of D. pteronyssinus was associated with beds, presence of pets, coal stoves used for heating, lower number of rooms, higher cooking frequency, higher washing frequency, working housewife, open kitchen, wooden floors in kitchens, lower cleaning frequency, type of upholstery furniture in living rooms (arm chairs), lower humidity and higher temperature.

Dietary shifts have consequences for the repertoire of allergens produced by the European house dust mite.

Products manufactured from mass-cultured house dust mites, currently commercialized for the diagnosis and immunotherapy of allergy, are heterogeneous in terms of allergen composition and thus present concerns to regulatory authorities. The most abundant species, Dermatophagoides pteronyssinus (Trouessart) (Astigmata: Pyroglyphidae), produces 19 allergenic proteins. Many of these are putatively involved in mite digestive physiology and metabolism. This study aimed to evaluate the effects of mite-rearing media on allergen production. Mites were adapted to feed on culture media supplemented with proteins, lipids, carbohydrates or beard shavings, and collected to quantify major allergens (Der p 1 and 2) by immunodetection, transcription of allergen genes by real-time quantitative polymerase chain reaction, and allergen-related enzymatic activities. All culture media significantly affected the content of major allergens. Modification of macronutrients in the diet produced minor effects on the transcription of allergen genes, but significantly altered mite allergen-related activities. The most remarkable impacts were detected in mites feeding on beard shavings and were reflected in reductions in the content of major allergens, alterations in the transcription of nine allergen genes, and changes in eight allergen-related activities. These results demonstrate the importance of culture media to the quality and consistency of mite extracts used for pharmaceuticals, and highlight the need to further elucidate allergen production by mites in the laboratory and in domestic environments.

AT-RvD1 modulates the activation of bronchial epithelial cells induced by lipopolysaccharide and Dermatophagoides pteronyssinus.

Bronchial epithelial cells are essential to airways homeostasis; however, they are also involved in exacerbation of airway inflammatory responses of patients with conditions such as asthma. Dermatophagoides pteronyssinus (Dp), the most important allergen, and lipopolysaccharide (LPS), both of which are present in house dust mites (HDM), can activate immune and structural cells (such as bronchial epithelial cells) and modulate the airway inflammation in asthma patients. Resolvin D1 (RvD1) and its epimer aspirin-triggered-resolvin D1 (AT-RvD1) are lipid mediators that are produced during the resolution of inflammation and demonstrate anti-inflammatory and pro-resolution effects in several experimental models including experimental models of allergic airway inflammation. Here, we evaluated the effects of AT-RvD1 (10-12-10-10 M) on human bronchial epithelial cells (BEAS-2B) stimulated with LPS (2µg/ml) or Dp (10µg/ml). After 24h, the C-C motif chemokine ligand 2 (CCL-2) production was increased in cells that had been stimulated with LPS and Dp compared to the control. However, AT-RvD1 (10-11 and 10-10 M) significantly reduced the concentration of CCL-2 in a manner that was dependent on the N-formyl peptide receptor 2 (FPR2/ALX) and nuclear factor kappa B (NF-κB) pathways in cells stimulated with LPS or Dp compared to controls. In addition, AT-RvD1 reduced the phosphorylation of signal transducer and activator of transcription (STAT)6 and STAT1 in cells stimulated with Dp and LPS, respectively. In conclusion, AT-RvD1 demonstrated significant anti-inflammatory effects in bronchial epithelial cells that were stimulated with LPS or Dp, which provides new perspectives for therapeutic strategies to control inflammatory airway diseases.

IL-23 secreted by bronchial epithelial cells contributes to allergic sensitization in asthma model: role of IL-23 secreted by bronchial epithelial cells.

IL-23 has been postulated to be a critical mediator contributing to various inflammatory diseases. Dermatophagoides pteronyssinus (Der p) is one of the most common inhalant allergens. However, the role of IL-23 in Der p-induced mouse asthma model is not well understood, particularly with regard to the development of allergic sensitization in the airways. The objective of this study was to evaluate roles of IL-23 in Der p sensitization and asthma development. BALB/c mice were repeatedly administered Der p intranasally to develop Der p allergic sensitization and asthma. After Der p local administration, changes in IL-23 expression were examined in lung tissues and primary epithelial cells. Anti-IL-23p19 antibody was given during the Der p sensitization period, and its effects were examined. Effects of anti-IL-23p19 antibody at bronchial epithelial levels were also examined in vitro. The expression of IL-23 at bronchial epithelial layers was increased after Der p local administration in mouse. In Der p-induced mouse models, anti-IL-23p19 antibody treatment during allergen sensitization significantly diminished Der p allergic sensitization and several features of allergic asthma including the production of Th2 cytokines and the population of type 2 innate lymphoid cells in lungs. The activation of dendritic cells in lung-draining lymph nodes was also reduced by anti-IL-23 treatment. In murine lung alveolar type II-like epithelial cell line (MLE-12) cells, IL-23 blockade prevented cytokine responses to Der p stimulation, such as IL-1α, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-33, and also bone marrow-derived dendritic cell activation. In conclusion, IL-23 is another important bronchial epithelial cell-driven cytokine which may contribute to the development of house dust mite allergic sensitization and asthma.

Reproductive biology of Euroglyphus maynei with comparisons to Dermatophagoides farinae and D. pteronyssinus.

The reproductive biology of the house dust mite, Euroglyphus maynei, is not well studied. This mite is usually less common in homes than Dermatophagoides farinae and D. pteronyssinus. When it is present, it usually co-inhabits with the Dermatophagoides spp. and is more restricted in geographical distribution. In this study, the duration of the life cycle (egg to adult) at 23 and 30 °C at 75% relative humidity (RH) and fecundity at 23 °C and 75% RH were determined for E. maynei and the data were compared to similar data for D. farinae and D. pteronyssinus. Adults hatched from eggs after 28 days at 23 °C and 20 days at 30 °C. Females produced 1.4 eggs/day during a reproductive period of 24 days at 23 °C. Euroglyphus maynei has a shorter life cycle than D. farinae and D. pteronyssinus at 23 °C but a longer life cycle at 30 °C. Euroglyphus maynei has a shorter reproductive period and produces fewer eggs than both D. farinae and D. pteronyssinus.

Interference in foraging behaviour of European and American house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae (Acari: Pyroglyphidae) by catmint, Nepeta cataria (Lamiaceae).

The European and American house dust mites, Dermatophagoides pteronyssinus and D. farinae, have a huge impact upon human health worldwide due to being the most important indoor trigger of atopic diseases such as asthma, rhinitis and atopic dermatitis. Preceding studies have shown that the behavioural response of house dust mites towards volatile chemicals from food sources can be assessed using a Y-tube olfactometer assay. In the current study, we used this assay to investigate, for the first time, the ability of the essential oil of the catmint plant, Nepeta cataria (Lamiaceae), known to repel other ectoparasites affecting human and animal health, to interfere with the attraction of D. pteronyssinus and D. farinae towards a standard food source (fish flakes). Two distinct chemotypes (A and B), enriched in the iridoid compounds (4aS,7S,7aR)-nepetalactone and (4aS,7S,7aS)-nepetalactone, and the sesquiterpene (E)-(1R,9S)-caryophyllene, were used. Initial assays with a hexane extract of fish flakes (FF extract) confirmed attraction of mites to this positive control (P < 0.001 and P < 0.05 for D. pteronyssinus and D. farinae respectively), but when presented in combination with either N. cataria chemotype, tested across a range of doses (10, 1, 0.1 and 0.01 µg), decreasing attraction of mites to their food source was observed as the dose augmented. Our study shows that N. cataria, enriched in iridoid nepetalactones and (E)-(1R,9S)-caryophyllene, exhibits potent repellent activity for house dust mites, and has the potential for deployment in control programmes based on interference with normal house dust mite behaviour.

Allergenic Dermatophagoides mites causing asthma among schoolchildren at Ain-Shams District, Cairo, Egypt.

The present study was performed on house dust samples collected from ten homes of schoolchildren suffering from asthma at Ain-Shams district, over a period of two years (2008 & 2009). The data revealed that the total annual density of the two allergenic mites (Dermatophagoides pteronyssinus (Trouessart) & Dermatophagoides farinae (Hughes) was 202 individual mites with 22 asthmatic children in the first year, and individual mites increased to 268 with 36 asthmatic children in the second year. The two house dust mites were more abundant in bedrooms than in living ones (292 & 187 mites, respectively). The prevalence of the house dust mites on the mattresses and furniture were higher in bedrooms and living rooms than on the floors (340 & 140 mite, respectively). Winter season recorded the highest prevalence for both mites in the first and second year (87 & 110, respectively). Summer represented the lowest values (19 & 25, respectively).

The fauna and distribution of house dust mites in residential homes of Bandar Abbas District, Southern Iran.

This study was designed to determine the occurrence, distribution and abundance of house dust mites (HDM) in residential homes in Bandar Abbas (Hormozgan Province), because of numerous complaints of allergies in this oriental city. The study area was divided in five sampling zones based on population density and geographical distribution. In each sampling zone 10 houses were randomly selected. A total of 50 home dust samples were collected using a portable vacuum cleaner for 2 min from 1 m(2) of the surface of mattresses, carpets, sofas and furniture in residential houses. After collection, samples were immediately frozen. Mite species were identified and counted using standard methods and keys. Of the sampled houses 88% (44 houses) were contaminated with at least one HDM species. Three species were identified: Dermatophagoides pteronyssinus (63.1%), D. farinae (32.8%) and D. evansi (4.1%) (Pyroglyphidae). Our findings indicate a relationship between HDM density and moisture and temperature of residential places. The high contamination rate of residential houses (88%) and the favourable environmental conditions for these arthropods stress that they should be considered as important allergic causing agents.

Identification of neryl formate as the airborne aggregation pheromone for the American house dust mite and the European house dust mite (Acari: Epidermoptidae).

The American house dust mite, Dermatophagoidesfarinae Hughes, and European house dust mite, Dermatophagoides pteronyssinus Trouessart, are major pests of medical importance throughout the developed world, causing atopic diseases such as asthma, rhinitis, and atopic dermatitis. Previous studies in our laboratory have shown that the behavioral responses of house dust mites toward volatiles from food sources could be assessed using a Y-tube olfactometer assay. The current study used this Y-tube assay to investigate house dust mite pheromones. A hexane extract of D.farinae, along with fractions of the extract prepared by microscale liquid chromatography over Florisil, were tested for behavioral activity. One of the chromatographic fractions was shown to be significantly attractive (P < 0.05) for D. farinae, compared with a solvent control. Coupled gas chromatography-mass spectrometry analysis of this behaviorally active fraction indicated that neryl or geranyl formate was the major component. Peak enhancement by gas chromatography, using authentic samples of the neryl and geranyl isomers prepared in high purity by chemical synthesis, confirmed the identity of the major peak as neryl formate. In Y-tube assays, male and female D. farinae and D. pteronyssinus both were significantly attracted to synthetic neryl formate at doses of 100 and 10 ng, respectively (P < 0.05). No significant differences were found for D. farinae and D. pteronyssinus when synthetic neryl formate and house dust mite extracts containing natural neryl formate were tested at the same level. Dynamic headspace collection of D. farinae and D. pteronyssinus colonies showed that neryl formate was released as a volatile organic compound by both species. Our study shows that neryl formate is an aggregation pheromone for D. farinae and D. pteronyssinus, and has the potential to be used as part of a novel lure-and-kill system for house dust mite control.

Transition matrix population model for dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae).

A transition matrix model of the population dynamics of the European house dust mite, Dermatophagoides pteronyssinus (Trouessart) (Acari: Pyroglyphidae), is described. It can model continuously varying conditions by forming transition matrices by interpolation between known transition matrices constructed from experimental data. Finite carrying capacity is modeled by modifying the population distribution vector at each time-step by using a form of the Skellam model, which is derived from the assumption that in competition each successful animal gets all it requires, and the unsuccessful animals get insufficient resources for survival or reproduction. The transition matrix model does not require all mites to have the same survivorship, life-stage durations, fecundity, and so on. Life table data to drive the model is taken from two sources, one source of which requires using the mean and standard deviation of the duration of each stage to synthesize a range of duration times and a range of transition probabilities to the next stage, thus ensuring variability between mites. Where synthesized data are used, significant long-lasting oscillations in dust mite levels are modeled, which does not happen when modeling with unsynthesized data, and is unlikely to occur in the field. Under conditions normally met with in the microenvironment (bedding, base of carpet, soft furnishing) of D. pteronyssinus, finite carrying capacity is essential to prevent unbounded population growth. The model is compared with other workers' field data with fair agreement. It is argued that shortcomings in the available data rather than the model are the principal reasons for differences between field and modeled results.

[Investigation of house dust mite incidence related to social factors]. / Ev tozu akarlarinin görülme durumunun sosyal degiskenler açisindan incelenmesi.

House dust mites are found everywhere there are temperatures of 25-27 degrees C and humidity of 70-80 percent. The amount of acari varies according to social conditions. The aim of this study was to determine the relationship between social factors and the observable rate of acari. A total of 303 dust samples were examined and according to results of questionnaires, increase of acari populations was observed under the following conditions: crowded homes, wooden houses, using second hand furniture, poor ventilation, insufficient cleaning, no vacuum cleaner, lack of sunlight indoors, high humidity, and presence of pets in the garden. Even though the acari density was sometimes found to be high, relationships with factors were not statistically significant. Advice to allergic patients about precautions concerning the factors may be useful.

Predicting the population dynamics of the house dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) in response to a constant hygrothermal environment using a model of the mite life cycle.

A generalised model of the life cycle of a house dust mite, which can be tailored to any particular species of domestic mite, is presented. The model takes into account the effects of hygrothermal conditions on each life cycle phase. It is used in a computer simulation program, called POPMITE, which, by incorporating a population age structure, is able to predict population dynamics. The POPMITE simulation is adapted to the Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) (DP) mite using published data on the egg development period, total development period, adult longevity, mortality during egg development, mortality during juvenile development, and fecundity of individual DP mites held at a range of constant hygrothermal conditions. An example is given which illustrates how the model functions under constant hygrothermal conditions. A preliminary validation of POPMITE is made by a comparison of the POPMITE predictions with published measurements of population growth of DP mites held at a range constant hygrothermal conditions for 21 days. The POPMITE simulation is used to provide predictions of population growth or decline for a wide range of constant relative humidity and temperature combinations for 30 and 60 days. The adaptation of the model to correctly take account of fluctuating hygrothermal conditions is discussed.

A simple model for predicting the effect of hygrothermal conditions on populations of house dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae).

A simple mite population index (MPI) model is presented which predicts the effect on house dust mite populations of any combination of temperature and relative humidity (RH). For each combination, the output is an index, or multiplication factor, such that 1.1 indicates 10% population growth and 0.9 indicates 10% population decline. To provide data for the model, laboratory experiments have been carried out using lab cultures of Dermatophagoides pteronyssinus. The population change was observed for mites held in steady-state conditions at different combinations of temperature and RH over 21 days. From the results, a best-fit equation has been derived which forms the basis of the MPI model. The results also enable a new term to be defined: the Population Equilibrium Humidity, PEH, the RH for a given temperature at which house dust mite populations neither grow nor decline. It is similar to Critical Equilibrium Humidity, the RH below which house dust mites are unable to maintain water balance, but relates to a population of mites (rather than a physiological phenomenon) and is more able to take account of the observed effects of extremes of temperature and RH. Compared with previous population models, the MPI model is potentially more accurate and comprehensive. It can be combined with other simple models (described in previous papers), such as BED, which simulates the average hygrothermal conditions in a bed, given room conditions, and Condensation Targeter II, which simulates room conditions given a range of easily obtainable inputs for climate, house type and occupant characteristics. In this way it is now possible, for any individual dwelling, to assess the most effective means of controlling mite populations by environmental means, such as by improving standards of ventilation and insulation, or by modifying the occupant behaviour that affects the hygrothermal environment within a dwelling. Although the MPI model requires further development and validation, it has already proved useful for understanding more clearly how the different hygrothermal conditions found in beds and bedrooms can affect mite populations. It has also demonstrated that there is considerable scope for controlling mites by environmental means in cold winter climates such as the UK.