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PubMed1990

Development of Dermatophagoides pteronyssinus (Acari: Pyroglyphidae).

Developmental times (egg to adult) and fecundity of the European house dust mite, Dermatophagoides pteronyssinus (Trouessart), were determined for various temperatures that normally occur in the mite microhabitat in homes. Egg-to-adult developmental times were 122.8 +/- 14.5, 34.0 +/- 5.9, 19.3 +/- 2.5, and 15.0 +/- 2.0 d (means +/- SD) at 16 (61 degrees F), 23 (73 degrees F), 30 (86 degrees F), and 35 degrees C (95 degrees F), respectively. Developmental times of individual life stages were consistent proportions of the total egg-to-adult developmental times regardless of temperature. Duration of the egg and protonymphal and tritonymphal life stages were 20-26% of the total development times and for the larval stage, 28-33%. At 23 degrees C, females lived 31.2 +/- 11.1 d and produced 2.5 +/- 0.7 eggs per day during a reproductive period of 26.2 +/- 10.7 d. By comparison, at 35 degrees C, females produced 3.3 +/- 1.3 eggs per day, but female longevity and the reproductive period were reduced to 15.5 +/- 9.6 and 11.6 +/- 6.4 d, respectively. During a lifetime, females produced 68.4 +/- 30.4 and 48.0 +/- 29.6 eggs at 23 and 35 degrees C, respectively.

Animals↗
PubMed1990

Enzyme-linked immunosorbent assay for quantifying antigens of Dermatophagoides farinae and D. pteronyssinus (Acari: Pyroglyphidae) in house dust samples.

Double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody as capture and detector antibodies was developed for quantifying antigens of Dermatophagoides farinae Hughes and D. pteronyssinus (Trouessart) mites contained in house dust samples. This monoclonal antibody was directed against mite antigens that were also reactive to immunoglobulin E antibody in all of 10 serum samples obtained from patients allergic to mites. Histological study using fluorescent antibody revealed that the monoclonal antibody was bound to the major part of the D. farinae mite body section including fecal matter and cuticles. The detection limit of the assay system was 0.17 microgram of soluble antigens of both mite species and the antigen amount corresponding to 0.5 mites per microplate well, whether in live or dead mites. This system did not react to antigens of Tyrophagus putrescentiae (Schrank) and Cheyletus malaccensis Oudemans. Slight inhibition of less than or equal to 21.3% was observed with nonspecific substances contained in house dust, such as wool, cotton, human dander, human hair, soil, and biscuit, but no direct ELISA reactions were obtained with any of these materials. In 49 house dust samples, ELISA was significantly correlated with the conventional microscopic observation method.

Animals↗
PubMed1994

Antigen levels of Dermatophagoides mites (Acari: Pyroglyphidae) in dust samples collected in homes of allergic patients.

A medical service system for testing antigen levels of Dermatophagoides farinae Hughes and D. pteronyssinus (Trouessart) mites in house dust was established to allow physicians to monitor the environment of patients with allergies. Dust samples were collected from a 1-m2 area at different sites for 1 min using a commercial collection apparatus attached to a vacuum cleaner. Extracts from fine dust fractions were processed quantitatively for antigen by a sandwich enzyme-linked immunosorbent assay. Mean antigen levels contained in samples from carpets, tatamis, and futons ranged from 431 to 852 micrograms per unit weight of dust (g). When data were expressed as micrograms per m2, the mean antigen level obtained from carpets (41 micrograms/m2) was significantly higher than that obtained from tatamis (15 micrograms/m2) and futons (14 micrograms/m2). Comparison of 37 paired samples collected from 10 homes at an interval of 1 to 2 mo indicated that high antigen levels of > 50 micrograms/m2 at four sites (three carpets and one tatami) decreased sharply after improvement of hygienic conditions surrounding allergic patients.

Animals↗
PubMed1995

Rapid house dust mite (Acari: Pyroglyphidae) and storage mite (Acari: Glycyphagidae and Acaridae) allergen test.

Ten years ago a simple technique was described for detecting guanine from house dust mite excretions. The level of guaninine correlated well with the level of house dust mite allergens. Detection of storage mites is becoming more and more important, and these mites also produce guanine. Therefore, the above-mentioned technique provides a good indication of levels of storage mite allergens.

Allergens↗
PubMed1995

Bioassay techniques for evaluating pesticides against Dermatophagoides spp. (Acari: Pyroglyphidae).

Three bioassay techniques for testing pesticides against the American house dust mite, Dermatophagoides farinae Hughes, and the European house dust mite, Dermatophagoides pteronyssinus (Trouessart), were evaluated using cypermethrin as a standard. All 3 bioassay techniques gave linear responses, and can be used for evaluation of different properties of compounds. The slide dip technique tests for contact activity, the plastic petri dish technique for residual activity on a nonporous surface, and the fabric technique for residual activity on a porous surface. The 2 species of house dust mites responded similarly to all 3 bioassays, indicating that these 2 species are equally susceptible to cypermethrin under a variety of test conditions. In further tests with the fabric technique, the composition of the fabrics used did not significantly affect the toxicity of the compound tested.

Animals↗
PubMed1996

Development and fecundity of Dermatophagoides farinae (Acari: Pyroglyphidae).

Duration of the life cycle at 16, 23, 30, and 35 degrees C and fecundity at 23 degrees C and 75% RH were determined for the American house dust mite, Dermatophagoides farinae Hughes. Lengths of the life cycles at 23 and 30 degrees C were 35.6 +/- 4.4 and 17.5 +/- 1.2 d, respectively. Few eggs completed development to the adult stage at 16 and 35 degrees C. At 23 degrees C and 75% RH, the preoviposition period was 3.7 +/- 1.1 d following emergence of the female from the tritonymph. The average reproductive period was 34.0 +/- 10.7 d with a mean total of 65.5 +/- 17.4 eggs produced per female. Female longevity after cessation of egg production was 63.3 +/- 64.6 d.

Animals↗
PubMed1996

Dispersal of American house dust mites (Acari:Pyroglyphidae) in a residence.

American house dust mites, Dermatophagoides farinae Hughes, were marked by adding a 4% solution of Sudan Red 7B, a microbiological stain, to mite rearing media. Marked mites were released onto a downstairs couch in a 2-story residence. Two children sat on the couch for approximately 3 h after which their clothes were examined for stained mites. Various parts of the house and family vehicle were vacuum sampled, and dust samples examined for presence of marked mites. Results of 2 trials showed the presence of marked mites on clothing, upstairs in the residence, as well as in the family vehicle. Clothing is shown to be a significant factor in the dispersal of American house dust mites. Even if concentrated in a small area (1 couch), mites were able to disperse throughout the house and into a family vehicle within a matter of weeks.

Animals↗
PubMed1997

Spetial and temporal distribution of house dust mite (Astigmata:Pyroglyphidae) allergens Der p 1 and Der f 1 in Barbadian homes.

House features contribute to house dust mite abundance and, therefore, exposure to mite allergens. Our study assessed the hypothesis that modernization of the domestic environment in a tropical setting may lead to a level of allergen from the house dust mites Dermatophagoides pteronyssinus (Trouessart) and D. farinae Hughes that previously has been defined clinically as at risk for people who suffer from allergic disease. Allergen (Der p 1 and Der f 1) levels were measured at 4 sites (mattress, bedroom floor, living room floor, and furniture) in 17 houses in Barbados during dry and rainy seasons. Der p 1(17 of 17 homes) at all 4 sites did not vary significantly from the dry to rainy season. Allergen levels varied according to site, and were highest in living room furniture in both seasons (geometric mean 40.37 and 64.17 micrograms/g, respectively). Concentration of Der p 1 allergens were higher in concrete than in wood or mixed concrete and wood houses. Der f 1(9 of 17 homes) levels were lower than Der p 1 by 1/1,000 (both seasons). Results indicate that season is less important in regard to levels of Der p 1 than house construction and confirm other studies that implicate D. pteronyssinus as a more abundant source of allergen than D. farinae in this tropical setting.

Allergens↗
PubMed1997

Phospholipid metabolism in European house dust mite (Acari: Pyroglyphidae).

Phospholipid metabolism was studied in European house dust mite, Dermatophagoides pteronyssinus (Trouessart). Analysis of phospholipid metabolites in mite extracts suggested the presence of PLaseA1, PLaseA2, and PLaseC, which have important physiological roles in phospholipid metabolism. The optimum pH of PLaseA1 and PLaseA2 was 8 and 9, and the optimum temperature of PLaseA1 was 45 degrees C; the activity of PLaseA2 was not affected by temperature. The activity of PLaseA1 at pH 8 and 37 degrees C was 5 times higher than that of PLaseA2 in D. pteronyssinus. The optimum temperatures of diacylglycerol production were 25 and 45 degrees C.

Animals↗
PubMed1997

Kinetics of allergen expression in cultures of house dust mites, Dermatophagoides pteronyssinus and D. farinae (Acari: Pyroglyphidae).

Laboratory cultures of house dust mites Dermatophagoides pteronyssinus (Trouessart, 1897) and Dermatophagoides farinae Hughes, 1961 were used to study the population dynamics of the mites and the kinetics of antigen appearance. The analysis of extracts obtained after different incubation periods, carried out by SDS-PAGE, immunoblotting, and enzyme-linked immunosorbent assay, allows for the definition of 3 different growth phases: the latency phase (F1); the exponential growth phase (F2) during which the allergenic proteins, including the Der 1 and Der 2 major allergens, were expressed more intensely and in larger quantities; and a final phase (F3), death, in which the lowest rates of allergenic components with a clearly different pattern were seen. The data obtained from this work demonstrates that mite cultures during the maximum growth phase (F2) contain the largest amount of allergenic components as well as the highest major allergen concentrations.

Allergens↗
PubMed1998

Population dynamics of the house dust mites Dermatophagoides farinae, D. pteronyssinus, and Euroglyphus maynei (Acari: Pyroglyphidae) at specific relative humidities.

Experiments were conducted to determine the effects of relative humidity on the population dynamics of single and mixed species of Dermatophagoides farinae Hughes, D. pteronyssinus (Trouessart), and Euroglyphus maynei (Cooreman) at specific relative humidities maintained at 20 degrees C, with unlimited food. The population density of single and mixed species (D. farinae and D. pteronyssinus) increased exponentially when cultured at 65, 70, and 75% RH. The mean population growth rates were 17.3 +/- 4.4 SD and 32.5% +/- 4.7/wk for D. farinae and D. pteronyssinus, respectively. Mean population doubling times were 2.2 +/- 0.3 and 4.2 +/- 1.3 wk for D. pteronyssinus and D. farinae, respectively. Mixed species cultures, started with equal numbers of D. farinae and D. pteronyssinus, resulted in higher percentages of D. farinae than D. pteronyssinus. In cultures started with 75% of one species and 25% of the other, the more numerous species remained dominant and in similar ratios throughout the experiment. Both D. farinae and D. pteronyssinus population densities maintained at 85% RH declined over a 12-wk culture period because of mold growth. E. maynei were unable to survive at 65, 70, 75, and 85% RH, which indicated that their climatic requirements were different from those of D. farinae and D. pteronyssinus. Population densities of D. farinae and D. pteronyssinus cultures declined when held at 21-22 degrees C and relative humidities of < or = 50%; however, at 50% RH, significant proportions of the populations survived for 10 wk. Half-life for desiccation of D. farinae and D. pteronyssinus at 45% RH was 11.5 and 1.2 wk, respectively, but at 50% RH was 86.3 and 4.0 wk, respectively. The data indicated that a < or = 50% RH would have to be maintained for long periods to reduce both D. farinae and D. pteronyssinus by desiccation procedures. The results of this study show that D. farinae and D. pteronyssinus have high reproductive potentials and population growth rates, which indicate that mite reduction procedures must be thorough or mite densities will return to high levels quickly following remediation if adequate food and suitable microclimatic conditions exist.

Animals↗
PubMed1998

Water balance of Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) maintained by brief daily spells of elevated air humidity.

A facility was constructed to expose cultured Dermatophagoides pteronyssinus (Trouessart) to 24-h cycles of changing relative humidity; low humidity was interrupted every day by a period of high humidity. The temperature was kept at 16 degrees C, a common temperature on the ground floor of Dutch houses. Partially dehydrated mites were exposed to various humidity regimes in the absence of food and liquid water. Some mites gained weight when moist air was given for only 1.5 h every day. In the presence of food, egg production was recorded when moist air was given for at least 3 h daily, whereas the average relative humidity was quite low and less than the critical equilibrium humidity of D. pteronyssinus. Brief spells of elevated humidity allowed populations to survive much longer in a microclimate that was otherwise too dry, and may be decisive for survival during the winter months. We found that average relative humidity was misleading as an indicator of mite survival and growth conditions.

Acari↗
PubMed1998

Survival, fecundity, and development of Dermatophagoides farinae (Acari: Pyroglyphidae) at fluctuating relative humidity.

We determined the survival, development, and fecundity of Dermatophagoides farinae Hughes exposed to fluctuating daily regimes of hydrating and dehydrating relative humidity. Larva emerged from 84, 92, and 94% of eggs incubated at a regime of 2, 4, and 8 h at 75% RH and 22, 20, and 16 h at 0% RH, respectively. No emerging offspring completed the life cycle when exposed to the 2 and 4 h of moist air daily but 44 and 53% survived for 70 d in the larval or nymphal stages, respectivley, and these completed development to adults when subsequently held at a constant 75% RH. Given 8 h of moist air daily, 41% of emerging offspring completed the life cycle but development was 1.6 times longer compared with development at a constant 75% RH. For all daily hydrating and dehydrating regimes, a greater percentage of offspring became males than females. Overall, survival of immatures was remarkable at these daily long periods of dehydrating conditions when a short period of hydrating moisture was provided. When exposed to a daily regime of 4 h of moist air (75% RH) and 20 h of dry air (0% RH), 84% of females survived 28 d and produced approximately 1/3 of the number of eggs produced at constant 75% RH (control).

Animals↗
PubMed1999

Enzymatic analyses of house dust mite extracts from Dermatophagoides pteronyssinus and Dermatophagoides farinae (Acari: Pyroglyphidae) during different phases of culture growth.

The majority of clinically important allergens of Dermatophagoides pteronyssinus (Trouessart, 1897) and Dermatophagoides farinae Hughes, 1961 present enzymatic activity. The allergenic enzymes described include cysteine proteases in group 1 allergens, trypsins in group 3, amylases in group 4, and chymotrypsins in group 6. Apart from these, other possibly allergenic enzymes also have been identified. Therefore, enzymatic profiles were studied during the 3 growth periods of the mite population--latency phase, exponential growth phase, and death phase. The activity of 19 different enzymes was analyzed by means of the Api Zym system, a method that has been used to study both mite extracts and other allergenic materials. Our study has demonstrated that the extracts contain a large variety of enzymes. It has been observed that enzymatic activity is caused exclusively by mites because the control carried out on the culture medium was negative for all the enzymes studied. Generally, the levels of diverse enzymatic activity increased with the growth of the culture, and decreased later, in both species. However, proteases are the exception; they maintain a high level of activity during the death phase of the cultured mites. The ratio between trypsin and chymotrypsin activity can be used as an excellent tool for quality control parameters during obtention of allergenic mite extracts.

Animals↗
PubMed1999

Fluctuating hydrating and dehydrating relative humidities effects on the life cycle of Dermatophagoides farinae (Acari: Pyroglyphidae).

Reducing relative humidity to < 50% in homes is recommended as one means of reducing dust mite populations in the homes of those who suffer allergies to house dust mites. Because of some activities in the home (e.g., bathing, cooking, opening windows), it may not be possible to keep relative humidity constantly < 50%. We determined how the fluctuating daily regimes of hydrating (75%) and dehydrating (35%) relative humidities affected the development of Dermatophagoides farinae Hughes. The life cycle was completed (egg to adults) when mites were given regimes of 24 h at 75% RH, 8 h at 75% and 16 h at 35% RH, 6 h at 75% and 18 h at 35% RH, and 4 h at 75% and 20 h at 35% RH. The time required to complete development was inversely related to the amount of moist air given daily. Development took 58.3 +/- 1.44, 64.7 +/- 1.87, and 82.4 +/- 2.39 d for 8, 6, and 4 h of moist air daily, respectively. In comparison, the life cycle was completed in 41.1 +/- 0.50 d when development occurred at a constant 75% RH. Egg incubation time was significantly longer for fluctuating ambient relative humidity compared to a continuous 75 or 35% RH. Of the emerging larvae 53.8, 72.7, 62.7, and 85.0% completed the life cycle when given 4, 6, 8, and 24 h 75% RH daily and 35% RH for the remainder of the day. This study revealed that D. farinae can complete development when given only short periods of moist air daily but the rate of development is much slower than development at a constant 75% RH. Therefore, reducing ambient relative humidity does reduce the rate of development of mite populations and the accumulation of dust mite allergen.

Animals↗
PubMed2005

Development of Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) at constant and simultaneously fluctuating temperature and humidity conditions.

House dust mites are found in almost all dwellings in New Zealand and are a major risk factor in the development of asthma and perennial allergic rhinitis. We studied the longevity, life stage length, and fecundity of a New Zealand strain of European house dust mite, Dermatophagoides pteronyssinus (Trouessart), at constant (23 degrees C, 75% RH) and the fluctuating conditions typically found in dry (18-25 degrees C, 60-38% RH) and damp (18-23 degrees C, 70-55% RH) New Zealand dust mite microhabitats in carpets. All the adult mites placed in the "dry" conditions died within 18 d. Mites in the "da conditions had developmental times, oviposition, and death rates that were not significantly different from constant conditions. These mites are tolerant of fluctuating temperatures, but they are more susceptible to environments that strongly fluctuate in humidity.

Animals↗
PubMed1990

House dust mite sensitivity: a comparison of immune response with exposure to four species of Pyroglyphidae.

Twenty-five atopic children under 11 years of age were studied, using skin and RAST tests, for their specific IgE response to four species of pyroglyphid house dust mites, Dermatophagoides pteronyssinus, D. farinae, D. microceras and Euroglyphus maynei. All of the children were sensitive to D. pteronyssinus, 20 (80%) of these children were also sensitive to D. farinae and D. microceras, and 16 of the latter (64%) were also sensitive to E. maynei. Dust samples from various sites in the homes of the children revealed D. pteronyssinus in all homes studied but no D. farinae or D. microceras. E. maynei, although identified, was not present in significant numbers in any site. A control group of 20 atopic children of similar age who were not sensitive to house dust mite allergens had a similar exposure to the four mite species. These results suggest that factors in addition to mite exposure are important in the development of specific IgE responses to house dust mites.

Animals↗
PubMed2000

Cross-reactions between Dermatophagoides pteronyssinus and Dermatophagoides farinae (Acari: Pyroglyphidae) related to the different growth phases of cultures.

The allergenic cross-reactivity of both inter- and intraspecies of house dust mites, Dermatophagoides pteronyssinus (Trouessart, 1897) and Dermatophagoides farinae Hughes, 1961, taking into account the allergenic differences that exist throughout the growth curves, was evaluated by means of RAST-inhibition, using sera from patients allergic to these mites. The results demonstrate that extracts obtained from mite cultures during the maximum exponential growth phase are the best source of reagents to better discriminate cross-reactivity studies. The analyses obtained from this work, together with those obtained in previous reports, help to define the ideal conditions related to the allergenic diversity, avidity, and cross-reactivity of specific antibodies for the elaboration of allergenic extracts as a tool for use in diagnosis and specific treatment of IgE-mediated hypersensitivity caused by house dust mites.

Allergens↗