Evidence linking the zoonotic nematode Toxocara and asthma in children has been accumulating. The reviewed study aimed to quantify both the pooled seroprevalence of Toxocara antibodies among children with asthma and the strength of association between Toxocara seropositivity and pediatric asthma diagnosis through systematic review and meta-analysis.
The authors searched PubMed, Embase and Web of Science for eligible studies through 18 June 2025. Studies reporting Toxocara seropositivity in children with asthma were included. In total, 26 studies met inclusion criteria and were synthesized. Among these, seven studies were rated as high quality according to the Newcastle–Ottawa Scale.
A random-effects model was used to estimate pooled seroprevalence and pooled odds ratios (ORs) for case-control comparisons. Heterogeneity across studies was evaluated using τ2, I2 and Cochran's Q test. The authors explored sources of heterogeneity with subgroup analyses and meta-regression, and performed sensitivity analyses to assess the influence of individual studies. Publication bias was examined with funnel plots, Egger's test and the trim-and-fill method. Study quality was assessed using the Newcastle–Ottawa Scale.
Across the 26 included studies representing 3,246 asthmatic children, the pooled Toxocara seropositivity among children with asthma was 22% (95% confidence interval 16 to 29). The authors noted significant country-wise heterogeneity in prevalence estimates.
Twenty-three studies provided case-control data comparing asthmatic children with non-asthmatic controls. The pooled estimate showed that children with asthma had significantly higher odds of Toxocara seropositivity (pooled OR 2.56, p < 0.0001). The association varied significantly by geographic region and by the asthma case definitions used in individual studies.
Significant heterogeneity was documented. The authors reported that geographic region and country accounted for variation in effect sizes, and that differences in asthma case definitions also influenced results (subgroup p-values reported, including p < 0.0001 for geographic variation and p = 0.0004 for case definition differences). Studies using more rigorous diagnostic criteria—such as those based on the Global Initiative for Asthma—demonstrated stronger associations between Toxocara seropositivity and asthma.
Sensitivity analyses indicated the direction of association (higher odds of seropositivity among asthmatic children) remained consistent when individual studies were removed, but the pooled magnitude was affected by several outlier studies. Publication bias and small-study effects were assessed using funnel plots, Egger's test and trim-and-fill adjustment. Study quality was heterogeneous; seven of 26 studies were judged high quality on the Newcastle–Ottawa Scale.
The authors caution that, despite a significant pooled association, interpretation should be cautious because of: substantial heterogeneity across countries and studies; possible cross-reactivity in serological assays for Toxocara that can affect specificity; and methodological differences in study design and asthma case definitions. These factors limit inference about temporality and causality from the pooled observational data.
The meta-analysis highlights a consistent association between Toxocara seropositivity and pediatric asthma, but does not establish causation. The authors call for prospective longitudinal studies to clarify temporality and randomized controlled trials evaluating the effect of antiparasitic treatment on asthma outcomes to help determine causality and clinical utility.
This systematic review and meta-analysis of 26 studies found a pooled Toxocara seropositivity of 22% among children with asthma and a pooled OR of 2.56 for seropositivity in asthmatic versus non-asthmatic children. Significant heterogeneity, possible assay cross-reactivity and methodological variability across studies limit firm conclusions. Further longitudinal and interventional research is needed to confirm whether the observed association reflects a causal role of Toxocara infection in childhood asthma.