Investigation on house dust mites in different geographical regions of China.

In order to understand the distribution and species richness of mites in mattress dust in different geographical regions of China, mattress dust was collected by vacuum cleaner from south region (Guangzhou and Shenzhen, n=172), middle region (Shanghai and Nanchang,n=126) and north region (Beijing and Shenyang,n=112) respectively. Morphology identification analysis and statistical analysis then were followed. A total of 410 mattress dust samples were collected and mites were found in 242 (59.0%) dust samples. Of 8467 mite individuals were identified and distinguished as 11 families and 21 genera. Dermatophagoides pteronyssinus (south: 32.3%, east central: 46.6%, north: 38.2%) and Dermatophagoides farinae (south: 27.8%, east-central: 28.0%, north: 23.1%) were two predominant species in these three geographical regions. For nonpyroglyphid mites, Blomia tropicalis was found especially prevalent in south region of China (17.4%). Other species which accounted for more than 1% of the mites identified in each geographical region included Tyrophagus putrescentiae (south: 1.0%, north: 1.2%), Suidasia nesbitti (north: 5.8%), Cheyletus malaccensis (south: 3.7%, east-central: 1.2%, north: 1.2%), Acaropsis sollers (south: 2.2%),C. eruditus (east-central: 1.2%), Cheletomorpha lepidopterorum (north: 5.4%), Blattisocius keegani (east-central: 1.2%), etc. Mite positive rate (Chi-Square test, χ2=29.6, P0.001) and mite density (Kruskal-Wallis Test,χ2=41.8, P0.001) in south and central-east China were significantly higher than those in north China. The relationship between environmental variables and risk of mite sensitization (100 mites/gram) were analyzed. It was found that the risks in south and central-east regions were 7.4 (P0.001) and 8.6(P0.001) times higher than that in north region respectively. Mites in mattress dust at home and in campus dormitory had higher risk (Odds ratio:2.7 and 1.1), comparing with that in hotel. It was also found that the increase in floor level of sampling room could reduce the risk of mite sensitization (Odds ratio: 0.8; P=0.009). The study was the first investigation on distribution and species richness of mites in mattress dust in different geographical regions of China,which would help to prevent and treat the anaphylactic diseases against dust.