The association between seropositivity to human toxocariasis and childhood asthma in northern Iran: a case-control study

Background: Besides the well-known risk factors, Toxocara infection is thought to play a significant etiological role in the development of childhood asthma. To further explore this association, the prevalence of Toxocara infection in sera of asthmatic children and healthy controls in northern Iran was investigated. Methods: In this case-control study, cases were 145 physician-confirmed asthmatic children diagnosed according to the Global Initiative for Asthma (GINA) guidelines. Controls were 115 age–sex–residence-matched children who did not have physician-diagnosed asthma. The presence of anti-Toxocara immunoglobulin G (IgG) was tested using enzyme-linked immunosorbent assay. Univariate and multivariate logistic regression methods were used for case-control comparisons. Results: Seropositivity rate was 4.1% (95% CI, 3.4–4.7%) in asthmatic children and 0.86% (95% CI, 0.71–1.0%) in controls, suggesting a strong association (P-value < 0.02). Moreover, Toxocara infection was not significantly more prevalent (P-value = 0.12) in children with moderate sustainable asthma (9.3%, 3/32) than in children with mild sustainable asthma (2.3%, 3/113). Mean total immunoglobulin E (IgE) level was significantly higher in Toxocara-infected children (222.3 ± 367.1) than in non-infected children (143.19 ± 218.05) in the case group (P-value < 0.05). Conclusions: Our findings indicated that Toxocara infection can play an important role in childhood asthma. Further experimental and epidemiological studies are needed to clarify this hypothesis.