Distribution and Abundance of House Dust Mites, Dermatophagoides spp., in Different Climatic Zones of Southern California
The distribution and abundance of house dust mites, Dermatophagoides spp., were studied in August, October, and December, 1975 in 4 different climatic zones in southern California. During these months, a total of 15 houses were sampled in each climatic zone. Ninety-three percent of the coastal houses were infested with mites, where D. pteronyssinus (Trouessart) dominated (78%) over D. farinae Hughes. Sixty percent of the Riverside (inland valley) houses sampled were infested, where D. farinae was dominant (67%). A 3rd species, D. evansi Fain, Hughes and Johnson, commonly occurring in birds' nests, was found once in a coastal and Riverside house. Densities of both D. pteronyssinus and D. farinae were considerably higher in coastal than in Riverside houses. Live mites were not found in the lightly mite infested houses sampled in the desert (54% positive) and mountains (27% positive). Relative humidity, which varied in houses located in different climatic zones of southern California, was noted to be the principal limiting factor influencing the distribution and abundance of D. pteronyssinus and D. farinae in these zones. Temperatures did not appear to be an important factor influencing distribution and abundance of these mites in the study zones.
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- "Mites are capable of dispersing from reservoir habitats on clothing and other fabric, and can be carried to other indoor locations (Mollet and Robinson, 1996). Abundance of D. farinae and D. pteronyssinus is likely to remain unchanged, due to problematic control and abundance of local or reservoir populations (Lang and Mulla, 1977; Fernandez- Caldas et al., 1990). Control generally includes application of chemicals to kill mites or neutralize allergens, regular vacuum cleaning of infested substrates, and reducing use of upholstered furniture and carpeting. "
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ABSTRACT: Pest status of household and structural pests is based primarily on their persistence in the urban environment. Persistence of pest populations is determined by availability of reservoir habitats that harbor large and stable populations, which supply individuals to maintain small, local infestations. Success of pest species in the urban environment is dependent on a network of infestations and reservoir populations. Decline of pest species is linked to reduction or elimination of reservoir populations. The role of reservoir habitats and populations in the persistence of German and American cockroaches, old house borer, and American and European dust mites is discussed. Blattella germanica survives as a pest only indoors in local infestations and a limited number of urban reservoir populations. The importance of these popula- tions is evident in the decline in abundance and reduced pest status of this cockroach. Periplaneta americana lives in local infestations outdoors and indoors, and is supported by reservoir populations in urban sewers. There is limited potential for reducing its reservoir habitats, and it is likely to maintain its pest status. A cerambycid Hylotrupes bajulus occurs only in local infestations of structural softwoods in urban and rural buildings, and in reservoir populations in lumber storage sites. Effective control of structural infestations and improvements in lumber storage have removed the key reservoirs needed for persistence of this pest. Dermatophagoides spp. dust mites depend on small, local populations to persist in the living space. Long- term pest status of these mites is expected because of the relative ineffectiveness of cleaning to remove enough of a pest population to achieve reduction, and the ease in which mites are carried to new sites or existing infestations.
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ABSTRACT: The concentration of house-dust mites (Dermatophagoides spp.) was investigated for four seasons in three locations in each of 50 Danish apartments. Simultaneously the absolute humidity was recorded and the previously known correlation between mite counts and indoor humidity was confirmed. It appeared, however, that apartments which had a low absolute indoor humidity in the winter period (due to low household load of water vapour) did not contain noticeable concentrations of house-dust mites in the summer and autumn despite the fact that the indoor absolute humidity in these apartments could be high enough to allow for a high peak-population of mites. Because of this it is suggested that in a temperate climate avoidance measures against house-dust mites should be supplemented at least by a drying out period in the winter, when this process is convenient to perform because of the low outdoor absolute humidity.
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