Psocoptera spp. (book louse):: a new major household allergen in Mumbai

Background: Exposure and sensitization to indoor allergens of house dust mites and insects is well established. However, there are no reports on the allergenicity of Psocoptera spp. (book louse). These insects are known to inhabit various terrestrial habitats such as tree bark (bark lice), old papers, books, stored food products, etc and gain entry into human dwellings through these modes. They have the potential to sensitize individuals with an occupational exposure to them. Objective: Our objective is to use clinical and immunologic techniques to evaluate the extent of sensitization to Psocoptera in patients with nasobronchial allergy. We also have the objective to determine the extent of Psocoptera infestation in houses in Mumbai (Bombay). Methods: An entomologic analysis of dust samples in houses in Mumbai was carried out and Psocoptera found in these samples was mass-cultured. Two hundred patients were checked for allergy to the Psocoptera extracts using skin test. Total IgE and specific IgE to Psocoptera in sera from Psocopotera-sensitive patients' sera were estimated by enzyme immunoassay. IgE-binding proteins of Psocoptera were determined by immunoblotting experiments. Results: Among the 75 house dust samples from Mumbai analyzed for the presence of Psocoptera, 25% were found to be infested by Psocoptera. Strong skin sensitivity to Psocoptera was found in 20% of patients. Total IgE levels > 150 IU/mL were found in these patients and high levels of specific IgE to Psocoptera were detected by ELISA. Immunoblot analysis revealed 67, 59, 43, and 27 kD proteins as major allergens of Psocoptera. Conclusions: Psocoptera is an important allergen in Mumbai as it causes IgE mediated responses in 20% of the allergic population studied.