Understanding the trends, clustering, and risk factors of pinworm infection in preschool settings: A repeated cross-sectional multi-center study between 2019 and 2024

Background: Pinworm (Enterobius vermicularis) remains the most prevalent helminth among preschool-aged children worldwide. Despite China’s rapid development and decades of mass deworming, pinworm infection persists as a significant paediatric public-health problem. In this study, we aimed to understand the trends, clustering, and risk factors of pinworm infection in preschool settings of Jiangsu, China. Methods: A repeated cross-sectional study was conducted in 45 counties of Jiangsu Province from 2019 to 2024. Multi-stage cluster convenience sampling was applied. Each year, one rural preschool and one urban preschool were selected per county. The sample size for each school was 229 to obtain a 5% margin of error, an arbitrary design effect of 1.5 for a prevalence estimate of 10%, and a 10% nonresponse rate. A total of 27,925 children were investigated. Adhesive cellophane tape swabs were collected for confirmation of pinworm infection. A preschool-level permutation approach was used to evaluate clustering effects of pinworm infections within preschools, measured by infection rate ratio (IRR). Risk factors of pinworm infections were assessed by multiple logistic regression. Mediation analysis was conducted between the risk factor and pinworm infection. Results: The overall pinworm infection rate was 0.48%, ranging form 1.22% in 2019 to 0.11% in 2024 and showing a downward trend (χ2 = 52.436, P