Ecological Study Of Domestic Mites

Domestic mites are generally acknowledged as the most important sources of indoor allergen related to asthma and related respiratory allergies. Information about distribution and abundance of domestic mites is necessarily for their control and antigen avoidance. Our study was divided into three parts. First, we conducted a larger scale survey of domestic mites from three different parts of the country. This study filled the gaps in the research field of China and provided a theoretical basic for the research of mite allergen vaccine. A total of 410 mattress dust samples was collected from home, campus dormitory and hotel in south (Shenzhen and Guangzhou cities, n= 172), central (Nanchang and Shanghai, n= 126) and north (Beijing and Shenyang, n= 112) regions of China. Mites were found in 242 (59.0%) dust samples and 8 467 mite individuals were identified. D. pteronyssinus and D. farinae were two predominant species in three geographical regions. In nonpyroglyphid mites, Blomia tropicalis was found especially prevalent in south region of China (17.4%). mite positive rate (X~2= 29.6, P<0.001) in south and central China was significantly higher than it in north China. The relationship of environmental variables and the risk of mite sensitization (100 mites/gram) were analyzed. It was found that the risks in south and central region are 7.4 (P<0.001) and 8.6 (P<0.001) times respectively higher than that in north region. The home and campus dormitory mattress had higher risk (Odds ratio: 2.7 and 1.1), compared with hotel mattress. It was found that the increase of floor level of sampling room could reduce the risk of mite sensitization (P=0.009). Second, our research also studied faunal survey and seasonal prevalence of house dust mites in the urban area of subtropical climate --- Shenzhen. This study was the first of monitoring house dust mites in Shenzhen throughout the year. It enriched the ecological study of domestic mites and provided a theoretical foundation for the allergic diseases of house dust mites. A total of 989 dust samples was collect by combining Random with fixed. Mites were found in 447 ( 45.2%) dust samples and 10 042 mites were identified by microscopy, and refered to 17 families and 20 genera. D. farinae and D. pteronyssinus were two predominant species in Shenzhen. Mites could find in the samples all the year round and the specie in july-september was most(23 species) and in January-March least(3 species).Domestic mites with seasonal prevalence showed two peaks of the average density of live mites, one was in January-March, another was in May-July. The peak of dead mites was in January-March and far higher than the same peak of live mites. In addition, in order to investigate the fauna of house dust mite in Shenzhen region more detailed, it was suggested in the other investigation of mites in mattress dusts collected from college dormitories in Shenzhen (n= 308) the mite occurrence rate was 88% ( 271/308 ). Mites (6 163 individuals) isolated from those dust samples refer to 14 families 15 genera. D. farinae,D. pteronyssinus and B. tropicalis were the most abundant mite species and respecitively occupied 29.7%,21.7%and 17.9% of total mites. It was found that student sex ( male vs. female ), mattress cover( bamboo matting vs. bed sheet ), air conditioner installation ( yes vs. no ) and daily using of air conditioner ( < 2h, 2-8 and > 8h ) had no significant influence on mite occurrence rate ( P value all > 0.05 ). The risk of using bed sheet was significantly higher than using bamboo matting (OR= 2.62, P= 0.013). Relative humidity (RH) in sampling place had significant influence on the prevalence of mite.