House dust mite species and allergen levels in Galicia, Spain: a cross-sectional, multicenter, comparative study

Mites are important sources of allergens in Galicia, Spain. The objective of this study were to identify the main mite species and to determine allergen levels in mattresses from different locations in Galicia.

Dust samples were collected with a portable vacuum cleaner for 2 minutes from 2 m2 of the surface of the mattress used by mite allergic patients and controls. After collection, samples were immediatel frozen. Mite species were collected, identified, and counted, and the results expressed as mites per gram of dust. Mite allergen levels (Der p 1 and Der f 1) were measured using monoclonal antibodies. All individuals answered a questionnaire about the characteristics of their homes.

A total of 332 dust samples were collected (112 from mite allergic patients and 220 from controls). Thirty-two species were identified. The mean age +/-SD of all the participants was 32.4 +/- 20.8 years and of the mattresses 7.6 +/- 5.9 years. The geometric mean of the total mite counts was 910.2 mites per gram (896.2 mites per gram in the mattresses of mite allergic patients and 917.3 in the mattresses of control subjects; P > .05). The main species was Dermatophagoides pteronyssinus, which was present in 97.6% of the samples (geometric mean, 584.7 mites per gram). The geometric mean level of Der p 1 was 13.1 microg/g of dust: 11.9 in the mattresses of mite allergic patients and 13.8 in the mattresses of control subjects. The geometric mean level of Der f1 was 1.1 microg/g: 1.5 in the mattresses of mite allergic patients and 0.8 in the mattresses of control subjects. Environmental risk factors associated with high mite counts included obvious signs of humidity in the bedroom and the age of the mattress.

The mite fauna in Galicia is comprised of many species, several of which are known to be of allergologic importance. The total population is exposed to very high levels of mite allergens.