House dust mite allergy – Indian perspective

Background : An increasing trend in the prevalence of allergic diseases has been noticed from the developing countries due to many factors like metamorphic change in ambient air quality due to rapid urbanization and industrialization, subsequent increase in air pollution, change in living and dietary habits etc. Mites being in house dust represent a major source of allergens resulting various allergic manifestations and information regarding the house dust mites (HDMs) is of great importance to provide the patients with best possible diagnosis and management. As expected, information in this regard is mostly available from western and developed countries.

Methodology : The present study represents a comprehensive information on their diversity, habitat preference, seasonal occurrence in Kolkata Metropolis and their probable role in nasobronchial allergic manifestations through allergy skin test, quantification of total IgE  antibody and detection of allergen specific IgE antibodies.

Results & Discussion : During last ten years study period, a total of 54 species of mites belonging to 34 genera and 13 families under 3 orders have been identified, of which 5 species are new to science. Dermatophagoides pteronyssinus is the most predominant mite species, comprising 47% of total acarine fauna. Species diversity Index indicates that the maximum number and variety of mites are found in Pre-monsoon period and minimum in Winter. Patients' bed contains higher mite population than the corresponding bed-room floor dust. Results of Skin Prick Test (SPT) revealed that sensitivity towards house dust and house dust mites are 96% and among them more than 75% patients are sensitive to Dermatophagoides pteronyssinus, 63% to D. farinae and 72% to Blomia tropicalis mite allergens. Information regarding sensitivity to Blomia tropicalis mite is new to Indian population. The difference between patients and control mean serum IgE level is statistically significant (p< 0.05) and 93.5% patients are with elevated (300 IU/ml) serum IgE level. Identification of allergen specific IgE antibodies by Immuno CAP Syatem shows that 79.77% patients respond to HD allergen, 71.91 % to DP and 88.76% to DF allergens while 90% patients respond to BT allergen which further confirms the result of SPT.