Effect of animal contact and microbial exposures on the prevalence of atopy and asthma in urban vs rural children in India

Background: Environmental factors, including microbial exposures and close animal contact, are implicated in the lower prevalence of asthma and allergy in rural vs urban children. Objectives: To determine (1) the prevalence of asthma, rhinitis, eczema, and atopic sensitization in rural and urban children in India; (2) differences in microbial and animal exposures in these locales; and (3) whether differences in environmental exposures account for the different rates of asthma and atopy in these locales. Methods: One child from each of 50 urban (Mysore) and 50 rural (Vinobha) households in southern India was randomly selected for data analysis. Allergy, asthma, health, environment, and lifestyle information was obtained using a questionnaire and household inspections. Atopy was determined via skin prick testing for common allergens. Endotoxin content was measured in house dust samples. Results: Children from rural vs urban areas had lower prevalences of self-reported asthma (8% vs 30%; P =.005), rhinitis (22% vs 42%; P =.03), and atopic sensitization (36% vs 58%; P =.03). Higher median dust endotoxin loads were found in rural vs urban households (6.50 X 10(4) EU/m(2) vs 1.27 X 10(4) EU/m(2); p <.001). In multivariate analysis, close indoor animal contact (adjusted odds ratio [OR] 0.2; 90% confidence interval [CI], 0.05-0.9), outdoor animal contact (OR, 0.3; 90% Cl, 0.1-0.8), and exclusive breastfeeding for at least 6 months (OR, 0.2; 90% Cl, 0.1-0.5) were associated with lower atopic sensitization; mud flooring was associated with lower self-reported wheezing (OR, 0.1; 90% Cl, 0.02-1.0). Conclusion: Children in India who live with close animal contact and mud flooring and who were exclusively breastfed in infancy are less likely to develop asthma, rhinitis, and atopic sensitization.