An assessment of allergenic mite species and allergens in vehicles and homes, with particular reference to dust mite transfer in clothing

Abstract

Dust mite allergens cause conditions including asthma, atopic dermatitis and allergic rhinitis in people globally. Most studies investigating aspects of mite ecology and epidemiology have focussed on Pyroglyphid mites, which include those species generally most abundant in homes and have formed the basis for allergen sensitisation thresholds over the last two decades. Some studies have highlighted that mite species outside of the Pyroglyphidae family also harbour important allergens capable of causing sensitisation, yet these are regularly left unreported in research examining house dust mites. Additionally, knowledge gaps regarding the presence and quantity of allergenic mites in specific biotopes thus far exist, with no comprehensive research conducted on allergenic mite fauna in Irish homes to date. The aim of Chapters 2 and 3 of this thesis is to bridge important research gaps in the determination of quantities and species of allergenic mite fauna in previously understudied biotopes. In the first study described in this thesis, mites in dust from 30 homes with pets were compared with 30 homes without pets, with a view to assessing the influence that domestic pets have on allergenic mite densities and species composition within the home. Mite species richness was greater in homes with pets compared to homes without pets, suggesting that the presence of pets can result in a wider variety of epidemiologically important mite species within households. Vehicles have been greatly understudied with regard to quantifying dust mites and their associated allergens, with no published research thus far concerning mite densities and allergen levels in child car seats, an important void given that young children are most susceptible to developing conditions associated with dust mite allergens. A survey of 106 cars found 12 species of mites, with 80% of driver seats and 77% of child car seats containing mites. There was a significant correlation between the number of mites per gram of dust and the levels of Der p 1 allergen in the car seats sampled, with over 12% of driver seats and 15% of child car seats containing dust mite quantities sufficient to be risk factors for sensitisation and allergic reactions. Although clothing is the one of the main suspected mechanisms by which dust mites are dispersed and come to colonise new habitats, no research to date has investigated the physical properties that determine quantities transferred. Since dust mites were found in abundance in the vehicle-based survey, the dynamics involved in the transfer of dust mites from car seat material to modern clothing fabrics were hence investigated. Fabric type, mite condition (live or dead) and the applied force between the fabrics were all shown to have a significant effect on the transfer efficiency of house dust mites, while duration of contact was found to have no effect.