Dust mite species and allergen concentrations in beds of individuals belonging to different urban socioeconomic groups in Brazil.

BACKGROUND: Dermatophagoides pteronyssinus, Dermatophagoides farinae and Blomia tropicalis dust mites are among the most important agents of hypersensitivity reactions in human beings. However, a role of other mites in the etiology of these reactions has not yet been excluded.

OBJECTIVES: To investigate the nature of the dust mite fauna and the presence of Der p 1 (allergen 1 of Dermatophagoides pteronyssinus) and Blo t 5 (allergen 5 of Blomia tropicalis) on beds used by individuals with different socioeconomic backgrounds in Salvador, a major Brazilian city and to investigate possible associations of mite frequencies and allergen levels with (a) season of the year, (b) housing characteristics, (c) bed cleaning behaviors that could affect mite densities, and (d) allergy history.

METHODS: Dust samples were collected from 459 beds of 101 residences from two groups with different socioeconomic levels (hereafter called wealthy and poor groups) in the city of Salvador, Brazil, for the identification of mite species and determination of Der p 1 and Blo t 5 levels. History of allergy was collected using the ISAAC phase I questionnaire.

RESULTS: Eighty nine percent of the beds analyzed harbored at least one mite species. B. tropicalis was found in 71.8%, D. pteronyssinus in 39.9%, Cheyletus sp. in 33.9%, and Gohieria fusca in 21.1% of the beds. B. tropicalis was found with a similar frequency in beds of the two socioeconomic groups; D. pteronyssinus was found more frequently in the beds of the wealthy than of the poor group, whereas the reverse was observed with G. fusca. The concentrations of Der p 1 and Blo t 5 allergens exceeded the cut-off for sensitization of 2 microg/g of dust in 94.0% and 69.3% of the wealthy and poor group beds, respectively. No associations were found between history of allergy and mite species or between history of allergy and the concentrations of mite allergens.

CONCLUSIONS: The observation of B. tropicalis and D. pteronyssinus as the most frequently found mites is consistent with previous reports from tropical regions. The higher frequency of G. fusca in beds of individuals from the poor group than those from the wealthy group could be a consequence of different bed cleaning behaviors between the two groups.