[Acarofauna of house dust in Barcelona and surrounding cities].

The study of the house-dust acarofauna has aroused great interest since Voorhorst and colls. (41), in 1964, showed the continual presence of Dermatophagoides pteronyssinus in this habitat; and considered by these authors to be mainly responsible for the allergenic capacity of housedust. Studies carried out by other authors around the world confirm the universal character of this acarus and its prevailing presence in house-dust biocenosis. Dermatophagoides pteronyssinus is usually accompanied with other species of the same Pyroglyphidae family (see table II and III), and by species belonging to other acarian families and groups (table I). In this work 182 house-dust samples have been analyzed; these samples were collected in Barcelona and its surrounding. All have been found to be positive to acari. Samples of 5 g of house-dust were used for the study. The number of acari present in each sample showed a great variation both in relation to the total of acari present and to the number of isolated Pyroglyphidae (table VII and VIII). Dermatophagoides pteronyssinus appeared to be the prevailing species, found in 175 of the 182 samples examined and representing 39.70% of the total population of the acari collected. Other Pyroglyphidae isolated were D. farinae (95 samples), Euroglyphus maynei (75 samples), D. microceras (19 samples), D. passericola (1 sample) and Malayoglyphus carmelitus (1 sample) (table VI). The frequency and density in which other species of acari appeared in house-dust samples studied are shown in table VII. If we compare our results with those obtained by others (1, 7, 11, 21, 23, 26, 28, 29, 38) we see a great difference according to the frequency of acarian infestation in house-dust. We think that the causes of this variation are the diverse methods and techniques employed in the isolation and enumeration of acari. The low infestation percentages given by some authors could be due to the following: a) a study of insufficient amounts of house-dust samples; b) the lack of a method used for processing the samples; c) the interaction of both factors. The discovery of three single D. passericola specimens found in one sample lets us assume that the pressence of this acarus in house-dust has been sporadic. We think it could originate from birds' feathers or nests. Despite the very high number of Tarsonemus sp. collected (37.17% of the acari total) the representative of this species is actually very low, since almost all of them were found in two different samples taken from the same house.