Distribution and Abundance of House Dust Mites, Dermatophagoides spp., in Different Climatic Zones of Southern California
ABSTRACT 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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ABSTRACT: The authors investigated the relationship between respiratory symptoms in adults and exposure to mite and cat allergens, the role of endotoxins in house dust, the effects of mixtures of several allergens, and interactions between allergen exposure and allergic sensitization. Within a nested case-control study, 405 subjects aged 25-50 yrs from two German cities answered a standardized questionnaire. Allergen-specific immunoglobulin-E was measured. Dust samples were taken from the subjects9 homes to determine exposure to mite (Dermatophagoides pteronyssinus antigen 1 Der p 1) and (D. farinae antigen 1 Der f 1) and cat (cat antigen d1 Fel d 1) allergen and endotoxin content in settled house dust. Exposure to Der f 1 and Der p 1 plus Der f 1 w10 mg?g-1 of mattress dust, respectively, increased the risk of wheeze and breathlessness (odds ratios (OR): 4.04, 95% confidence interval (CI): 1.53-10.64, OR: 2.78, 95% CI: 1.06-7.28). Fel d 1 w8 mg?g-1 was positively associated with cough at night (OR: 2.74, 95% CI: 1.22-6.17), noteworthy also in the nonsensitized subjects. Subjects exposed to elevated concentra- tions of more than one allergen had an up to seven-fold increase in the risk of respiratory symptoms, compared to nonexposed subjects. Sensitized subjects exposed to elevated concentrations of Der f 1o rFel d 1 were found to have the highest risk of asthma attacks and respiratory symptoms. No statistically significant association was found between exposure to endotoxins and respiratory health. Indoor exposure to Dermatophagoides farinae antigen 1 and cat antigen d1 is a risk factor for respiratory symptoms in adults, and for cat antigen d 1 even in nonsensitized subjects. The risk is increased if subjects are exposed to a mixture of allergens or if they are sensitized in addition to high exposure. Eur Respir J 2001; 18: 555-563.European Respiratory Journal - EUR RESP J. 01/2001; 18(3):555-563.
- The Journal of asthma research 08/1979; 16(4):131-48.
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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.