Toxocara infection in children with asthma: a systematic review and meta-analysis

Evidence linking zoonotic nematode Toxocara and asthma is mounting in children. We aimed to estimate the pooled prevalence of Toxocara seropositivity in asthmatic children and quantify the association. We searched PubMed, Embase and Web of Science for studies (through 18 June 2025) reporting Toxocara seropositivity in asthmatic children. A random effects model was used to estimate pooled seroprevalence and odds ratios (ORs). Heterogeneity was explored using τ2, I2 and Cochran's Q test, subgroup analyses, meta-regression and sensitivity analysis. Publication bias assessment (Egger's test, funnel plots, trim and fill) and risk of bias evaluation (Newcastle-Ottawa Scale) was performed. Twenty-six studies comprising 3246 asthmatic children were included, of which 7 were high-quality studies. Pooled Toxocara seropositivity among asthma was 22% (95% confidence interval 16 to 29) with significant country-wise heterogeneity. In 23 studies comparing cases and controls, asthmatic children had significantly higher odds of Toxocara seropositivity (pooled OR 2.56, p<0.0001), with significant variation by geographic region (p<0.0001) and asthma case definitions (p=0.0004), with stronger associations observed in studies using rigorous definitions such as the Global Initiative for Asthma criteria. Sensitivity analyses showed that while the direction of association remained consistent, the magnitude was influenced by a few outlier studies. There is a significant association between Toxocara seropositivity and childhood asthma; however, the strength of this association should be interpreted cautiously due to heterogeneity, potential cross-reactivity in serological assays and methodological differences across studies. Prospective longitudinal studies and randomized controlled trials evaluating the impact of antiparasitic treatment are needed to clarify temporal relationships and establish causality.