Risk levels for mite allergen: are they meaningful, where should samples be collected, and how should they be analyzed?

Rapid visual detection of the allergen Dermatophagoides farinae in house dust by loop-mediated isothermal amplification

Dermatophagoides farinae is considered to be an important factor causing some allergic diseases, such as urticaria, allergic rhinitis, asthma, and other interrelated diseases. Avoiding exposure to allergens is the most effective way to reduce allergic reactions. In this study, we successfully established a loop-mediated isothermal amplification (LAMP) method for the detection of D. farinae DNA target internal transcribed spacer (ITS) and D. farinae 1 allergen (Der f 1) genes. The turbidity-monitoring system and visual fluorescent reagents were used to verify the test results of LAMP assay. Following optimization of the primers and reaction temperatures, the amplification sensitivity, specificity, and efficiency of the method for detecting D. farinae were assessed. There was no cross-reaction with other arthropod species that are commonly found in indoor environmental dust, such as Dermatophagoides pteronyssinus, Alophagoides ovatus, Periplaneta americana, Anopheles sinensis, and Musca domestica. Furthermore, the sensitivity of LAMP assay for detecting D. farinae DNA was 10 times greater than that of conventional PCR. The positive detection rate by the LAMP method was greater than the conventional PCR for both single D. farinae mites and D. farinae mites in indoor dust. A new type of LAMP method for D. farinae based on the Der f 1 and ITS genes was, therefore, successfully established. This study is the first time to detect the D. farinae allergen using LAMP assay. This assay could be useful as a model for the rapid detection of allergens produced by other house dust mites in the future.

"A year-long, fortnightly, observational survey in three European countries of patients with respiratory allergies induced by house dust mites: Methodology, demographics and clinical characteristics"

BACKGROUND

House dust mite (HDM) allergens constitute the leading trigger for the symptoms of persistent respiratory allergies (such as allergic rhinitis and asthma). However, the fluctuating, pernicious nature of the symptoms has given rise to a perception that HDM-induced respiratory allergy is not a "real" disease.

METHODS

In order to assess the self-reported disease profile and behaviour of adult patients with a self-reported history of severe, poorly controlled, physician-diagnosed HDM respiratory allergy, we performed an observational, international, multicentre survey in three European countries (France, Italy and Spain). Participants were included in the survey if they passed a short Internet-based screening questionnaire. Following completion of a detailed post-inclusion questionnaire, 28 fortnightly telephone interviews were used to gather extensive data on the participants' symptom prevalence and intensity, medical consultations, disease burden, quality of life, and medication use from late May 2012 to early July 2013.

RESULTS

Twenty-two thousand nine hundred ninety five individuals completed the Internet screening questionnaire and 339 respondents (67 % female) met all the inclusion criteria. 313 of the 339 (92 %) completed the post-inclusion questionnaire (n = 114 in Italy, 92 in France and 107 in Spain). The median time since the first symptoms of HDM allergy was over 13 years in all three countries. The response rate for the fortnightly interviews averaged 75 % (range: 29 to 97 %). The reported fortnightly prevalence of nasal and ocular symptoms peaked in the autumn (September to November) and spring (March to May). These peaks in prevalence coincided with increased reports of symptom worsening and higher physician consultation rates. In participants not allergic to pollen, the autumn and spring peaks were accompanied by a third peak in late December 2012. Very few participants reported that their symptoms had never improved (4 %) or never worsened (11 %) during the survey period.

CONCLUSIONS

In a survey in France, Italy and Spain, patients with severe HDM-induced respiratory allergies experienced a complex set of changing, troublesome symptoms throughout the year, with peaks in spring, autumn and (to a lesser extent) mid-winter.

Indoor allergens in settled dust from kindergartens in city of Łódź, Poland

OBJECTIVES

The main objective of the study was to determine the levels of house dust mite (Der p1), dog (Can f1), cat (Fel d1) and cockroach (Bla g2) allergens in kindergartens localized in an urban agglomeration.

MATERIAL AND METHODS

A quantitative analysis of allergens was carried out in settled dust samples collected by vacuuming the floor surface in three kindergartens (N = 84) and children's clothing (N = 36). The samples were collected in spring-summer and autumn-winter periods as well as at the beginning and end of the week. The allergen dust concentration was determined by enzyme-linked immunoenzymatic assay (ELISA).

RESULTS

The mean geometric concentrations (±geometric standard deviations) of allergens Der p1, Can f1, Fel d1 and Bla g2 determined in kindergartens were: 0.02 ± 3.21 μg/g of dust; 0.97 ± 4.49 μg/g of dust; 0.30 ± 4.43 μg/g of dust and 0.01 ± 3.08 μg/g of dust, respectively. Younger classrooms (children aged from 3 to 4 years) were characterized by almost twice higher mean concentration of allergen Fel d1, as compared to older classrooms (children aged from 5 to 6 years) (p < 0.05). A significant impact of seasonality on the level of dog allergen Can f1 was found (p < 0.05). No significant weekly variation was found in average concentrations of the allergens. Children who had a dog and/or cat at home were characterized by high concentrations of allergens Can f1 and Fel d1 on their clothes (59.2 ± 5.39 μg Can f1/g of dust; 3.63 ± 1.47 μg Fel d1/g of dust), significantly higher than concentrations of allergens in children who did not have any pets (p < 0.001).

CONCLUSIONS

Special attention should be paid to keeping the kindergarten rooms tidy and clean and to an appropriate choice of furnishings and fittings which would prevent the proliferation of the house dust mite and accumulation of allergens.

Sensitization to Dermatophagoides, Blomia tropicalis, and other mites in atopic patients

BACKGROUND

House dust mites (HDMs) are important causes of persistent allergic diseases, such as asthma and rhinitis. Various types of mites are found in the house dust of many countries, including Israel.

OBJECTIVE

To evaluate the prevalence of sensitization to various HDMs in patients with perennial allergic rhinitis and asthma.

METHODS

Sensitization of 117 patients with persistent rhinitis who attended the Allergy and Asthma Center in Tel Aviv (Israel) was evaluated by a skin prick test (SPT) using standardized allergenic extracts. The tested mites were Dermatophagoides farinae (DF), Dermatophagoides pteronyssinus (DP), Lepidoglyphus destructor (LD), Blomia tropicalis (BT), Tyrophagus putrescentiae (TP), Acarus siro (AS), Glycyphagus domesticus (GD), Blomia kulagini (BK), and Tetranychus urticae (TU).

RESULTS

Most patients (n = 95, 81%) had a positive SPT to at least one mite extract. The three most frequent positive reactions were to DF (78%), DP (75%), and, unexpectedly, BT (77%). The correlation between DF and DP sensitization was higher than the correlation between DF or DP to BT (r = .78 versus r = .60, p < .05). Six patients had positive skin reactions to at least one mite species other than DF, DP or BT, mainly LD (n = 2, 2.1%) and BK (n = 4, 3.8%).

CONCLUSIONS

The findings of this study identified the most ubiquitous mites to which Israeli patients with allergic rhinitis were sensitized and indicated the importance of BT as an allergen. Extracts of these mites may provide a more accurate diagnosis and effective treatment of respiratory diseases due to mite allergy in Israel and probably in other countries with similar climes.

Childhood asthma and indoor aeroallergens and endotoxin in Palestine: a case-control study

This study was carried out to evaluate the relationship between wheezing or sensitization and concentrations of mites, cat and dog allergens, and bacterial endotoxin in Palestine. A nested case-control involved analysis of mattress and floor dust from a 110 children's houses with reported wheezing and without wheezing. We found no consistent associations between allergen levels and either wheeze or specific atopic sensitization. Furthermore, no clear associations between mattress endotoxin levels and wheeze or atopy were found. Endotoxin in floor dust was inversely associated with atopic sensitization and wheeze, statistically significant only for atopic wheeze. Finally, a nonsignificant inverse association was observed between living room endotoxin and atopy within the non-wheezing control group. In conclusion, although our study found mostly negative results, it does suggest that endotoxin on living room floors might protect against atopic wheeze. However, this finding should be interpreted with caution due the relatively small sample size of the study and requires further confirmation.

Retrospective evaluation of epidermal skin prick tests in patients living in Aegean region

Sensitization to aeroallergens of Aegean region is not well decumented. In this study we evaluated the epidermal skin prick test results of the patients who applied to allergy outpatient department retrospectively. Epidermal skin prick test of the 5055 patients were evaluated. Of these patients 2638 (52 %) were female, 2417 (48 %) male, 1213 (24 %) adult and 3842 (76 %) pediatric patient, 1163 (23 %) patients were allergic rhinitis, 2477 (49 %) were bronchial asthma, 505 (10 %) were allergic rhinitis with bronchial asthma, 556 (11 %) were chronic urticaria, 253 (5 %) were wheezy infant and 101 (2 %) patients were atopic dermatitis, 2932 (58 %) had atopy history in their first and second degree relatives. Patients were aged between 3.5 months and 79 years (mean 14.1 3.2 years and median 11 years). In epidermal skin prick tests sensitization to house dust mites (D. farinae, D. pteroniyssinus), pollens (grass, cereals and trees), moulds, animal danders, foods (especially in early childhood) and cockroach were evaluated. Our data indicate that allergens that may be the cause of the high prevalence of allergic diseases in Izmir are probably produced by pollens and mites.

House dust mite allergen levels in German day-care centers

We investigated the levels of the major house dust mite allergens, Der p 1 and Der f 1, in dust collected from various locations in 41 day-care centers from two German cities (Düsseldorf and Bonn). One hundred and thirty-seven (96%) of 143 samples yielded detectable amounts of house dust mite allergen (range, < 15-85,000 ng/g; interquartile range, 210-1,480 ng group I allergen [sum of Der p 1 and Der f 1]/g dust), and 24 (17%) of the samples (8/34 mattresses; 11/46 cushions/soft toys; 5/43 carpeted floors, 0/20 smooth floors) exceeded the proposed "threshold" level of 2,000 ng/g dust in 18 (44%) of 41 day-care centers. Der p 1 and Der f 1 could be detected in nearly an equal number of samples. The highest concentrations of house dust mite allergens were found in dust from mattresses (geometric mean, 1,103 ng/g dust) and cushions/soft toys (geometric mean, 1,004 ng/g dust). The allergen load per unit area from carpeted floors exceeded that from smooth floors by more than two orders of magnitude. In comparison with dust samples from private homes within the same geographical area, the mite allergen levels in mattress dust (RR, 0.34; CI95, 0.18-0.64) and floor dust (RR, 0.21; CI95, 0.09-0.49) from day-care centers were significantly lower (p < 0.001). We conclude that day-care centers should be included as potential places of additional exposure to house dust mite allergens if avoidance measures are taken.