Maternal exposure to pyrethroid insecticides during pregnancy and repeated measures of infection symptoms among early school-aged children in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE)

OBJECTIVE: Indoor residual spraying (IRS) using pyrethroids insecticides to control malaria results in high exposure to local populations. Pyrethroids are immunosuppressant and prenatal exposure has been associated with higher rates of infection-related symptoms such as fever and colds among preschool children. Whether associations persist at older ages is unclear. Furthermore, prior studies assessed symptoms based on recall periods of ≥1 year, which may introduce misclassification. The aim of this study was thus to estimate associations between prenatal exposure to pyrethroids and infections among early school-aged children from an IRS area using shorter recall periods. METHODS: We measured urinary concentrations of four pyrethroid metabolites in peripartum samples collected from mothers enrolled in the Venda Health Examination of Mothers, Babies, and their Environment (VHEMBE), a birth cohort study situated in Limpopo, South Africa, where IRS with pyrethroids is conducted annually. From age 5, we collected data on infection symptoms using up to 4 questionnaires each encompassing a three-month recall period. We used Poisson marginal structural models for repeated outcomes to estimate associations between maternal exposure to pyrethroids and infection symptoms. RESULTS: A 10-fold increase in maternal cis-DCCA, trans-DCCA and 3-PBA was associated with a doubling in the rates of persistent fever (cis-DCCA: Incidence Rate Ratio [IRR] = 1.9, 95% CI = 1.2, 3.2; trans-DCCA: IRR = 2.2, 95% CI = 1.4, 3.5; 3-PBA: IRR = 1.9, 95% CI = 1.0, 3.4). Higher trans-DCCA was also related to a 70% increase in diarrhea rates (IRR = 1.7, 95% CI = 1.0, 2.8). CONCLUSION: Maternal pyrethroid exposure may be related to elevated infection rates among early school-aged children from an IRS area. In addition to IRS, pyrethroids are widely used in agriculture and retail products. Results may thus have global implications.