Distribution and abundance of dust mites within homes.

The distribution and abundance of dust mites can be modelled on three scales: the microhabitat scale (different habitats within homes), the macrohabitat scale (between homes), and the regional scale. This paper focuses on the first. Those parts of a home in which dust mite populations thrive will tend to be homogeneous in respect of key habitat suitability determinants. The more widespread such determinants, the greater the risk of high mite populations and allergen load. Habitat suitability determinants include an adequate textile substratum, optimal temperature and humidity, and food resources of appropriate quality, as well as other, currently unknown, requirements. Each determinant will have a characteristic distribution within any home, and they can be conceptualized as a series of overlays, or three-dimensional Venn diagrams, with the areas of overlap representing the most suitable sites for mite survival. That a population of dust mites is focused by constraining biotic and abiotic determinants means that spatial and temporal distribution and abundance are predictable, because the characteristics of the principal foci define optimal conditions for population growth. This concept, known as "focality", provides a framework for prediction of sites of high density of mite population and allergen exposure, as well as a basis for manipulating the microenvironment for control purposes.