Bottle feeding and exposure to Toxocara as risk factors for wheezing illness among under-five Amazonian children: a population-based cross-sectional study

Abstract

We investigated the prevalence and risk factors for wheezing and asthma in young Amazonian children. A population-based cross-sectional survey of 606 children aged 6-59 months was performed in two small towns in Acre State, Northwestern Brazil. Information on outcome variables (recent wheezing and medical diagnosis of asthma) and demographic, socioeconomic, environmental, maternal and nutritional variables was obtained by interviewing children's mothers or guardians. Infections with intestinal parasites and antibodies to the zoonotic nematode Toxocara were diagnosed using standard laboratory techniques. Multiple unconditional logistic regression models were used to describe associations between independent variables and outcomes. The prevalence of recent wheezing (one or more reported episodes in the past 12 months) was 42.6%, but only 19.8% of wheezing children were also reported to have a medical diagnosis of asthma (prevalence, 8.5%); 21.5% of the children examined had antibodies to Toxocara. Increased risk of asthma was independently associated with early introduction of bottle feeding, defined as <4 months of exclusive breastfeeding [adjusted odds ratio (aOR) = 2.21, 95% confidence interval (95% CI), 1.07-4.59, P = 0.033], and seropositivity to Toxocara (aOR = 2.37, 95% CI 1.17-4.77, P = 0.016), suggesting two potential targets for public health interventions.