The colonisation of new and retrofitted houses by the house dust mite Dermatophagoides pteronyssinus

Abstract

House dust mites are known to be a major cause of asthma and allergic disease worldwide. Little is known about the ecology of house dust mites in New Zealand houses. This study was undertaken to discover how quickly house dust mites are able to colonise new houses and what environmental factors are significant for their survival. A pilot study was carried out in 1995 to determine what experimental techniques were appropriate to collect house dust mites in people's houses and once these were determined a full-scale study commenced. Six new or retrofitted houses were studied for one year each. Mites were collected from sites in the front room and the master bedroom every two months. Allergen was also collected from these rooms. Analysis of the data showed that the rate of house dust mite colonisation in New Zealand houses is highly variable. The main factor influencing the colonising house dust mite populations appears to be food availability, which is closely linked to the occupancy rate of the houses. Mites colonise a house with a high occupancy rate (and therefore more food) faster than they colonise a house with a low occupancy rate. This is suggested by the 'boom and bust' cycles evident in the colonisation of some of the houses, which are assumed to be caused by the mites eating the available food faster than it accumulates.