Guanine, mite, and cockroach allergens in Costa Rican homes

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Abstract
Previous studies of schoolchildren in Costa Rica have shown an asthma prevalence of 23% and a high level of sensitization, particularly to mite allergens. As a continuation of these studies, some 400 dust samples were collected from various places in Costa Rica, and parts of these were analyzed for specific mite and cockroach allergens, as well as for the number of mites and amount of guanine. Guanine was quantified by a diazo, as well as an HPLC method, which were found to be highly correlated. The concentrations of guanine by the diazo method, Der p 1, Der f 1, and the number of mites were higher in bed dust than in bedroom floor dust, and it was possible to quantify mite allergens and guanine in almost all bed-dust samples. The mean levels were 2-3 times higher than the proposed risk level for elicitation of symptoms in mite-sensitive asthmatics. Bed and bedroom floor dust contained more guanine and mite allergen in humid (> 2000 mm rain) than in drier places (P < 0.05), but the number of mites in bed and bedroom floor dust was higher in less humid places (P = 0.01). The guanine content in bedroom floor dust was higher in areas with a temperate climate than in areas with a warmer climate (P < 0.001, Bartlett's chi square [BCS]), as was the number of mites (P < 0.01, Kruskal-Wallis [KW], 0.04, BCS) and the Der p 1 concentration (P = 0.01, BCS; P = 0.02, KW). The Der f 1 concentration in bedroom floor dust was higher in a warmer than in a temperate climate (P < 0.001, BCS). More guanine and mites were found in urban than in rural bed dust (P = 0.03, KW). Dust samples from the metropolitan area (temperate climate) of Costa Rica contained higher levels of guanine (P < 0.01) and Der p 1 (P = 0.07) than the coastal areas, but very little Der f 1. In these samples, guanine and Der p 1 allergen were closely related, and 2 micrograms of the allergen was equivalent to 0.49 mg of guanine. Two-thirds of bed and floor samples collected on cotton filters contained Bla g 2 allergen at mean levels of 1.6 and 2.1 units/g dust, respectively. Cockroach allergen was, however, absent in all bed samples from the metropolitan area, but did occur in very high concentrations in the coastal bed dust samples collected with tighter polyester filters. In conclusion, the concentration of guanine and Der p 1 was very high in the bed dust of Costa Rican homes. Some factors, such as humidity, small houses for large families, and type of bedding, probably favored the heavy mite infestation, which is probably related to the widespread occurrence of bronchial asthma in this country.