Ascaris lumbricoides infection and parasite load are associated with asthma in children

Introduction: Association between Ascaris lumbricoides infection and asthma is a controversial subject that has been studied by several authors based on the hygiene theory. This work contributes to better understanding this issue. Methodology: This was a cross-sectional study involving 1,004 children from a neighborhood of low socioeconomic status in Campina Grande, Paraiba, northeastern Brazil. Asthma was diagnosed using the International Study of Asthma and Allergy in Childhood (ISAAC) questionnaire. Intestinal parasitosis was diagnosed by parasitological examination (the Ritchie technique), and parasite load determined by the Kato-Katz technique. The statistical analysis was descriptive, and hypotheses were tested according to odds ratios. Results: A total of 260 children were infected with A. lumbricoides, and 233 had asthma. Light parasite loads were significantly associated with asthma (wheezing more than three times per year); p = 0.003, OR = 0.41(IC 0.22 - 0.75), while the heavy parasite loads were not; p = 0.002, OR = 2.37(IC 1.35 - 4.18). Similar results were observed in almost all the symptoms of asthma. No association was found with maternal educational level. Conclusion: In children living in urban areas of low socioeconomic status, a light parasite load of A. lumbricoides is a protective factor against asthma and its symptoms. Meanwhile, heavy parasite load is a risk factor and contributes to the high prevalence of asthma and its symptoms among these children.