Prenatal exposure to DDT and pyrethroids and humoral response to vaccines among South African children from an area sprayed for malaria control

Abstract

OPS 60: Social factors and environmental health across the world, Room 210, Floor 2, August 27, 2019, 1:30 PM - 3:00 PM Background/Aim: Animals studies strongly suggest that exposure to insecticides such as DDT and pyrethroids may inhibit immune response to vaccines. However, few human studies have investigated this question and none have done so in communities where insecticides are used to control malaria as part of Indoor Residual Spraying programs. These communities experience high exposure to insecticides and may be particularly susceptible to their toxic effects due to poverty, malnutrition and poor health. Our objective was thus to evaluate whether prenatal exposure to DDT and pyrethroids was associated with reduced immune response to vaccines at age 3.5 and 5 years among South African children participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) birth cohort study. Methods: Between August 2012 and December 2013, we enrolled 752 women when they presented for delivery at Tshilidzini hospital in the city of Thohoyandou. We collected urine and blood samples at delivery for the measurement of pyrethroid metabolites and DDT via gas chromatography-mass spectrometry, respectively. At age 3.5 and 5 years, we measured measles, tetanus and Haemophilus influenzae b (Hib)-specific antibody titers in serum via enzyme-linked immunosorbent assay (ELISA). Results: Percentages of fully-vaccinated children with antibody titers below protective levels were 5.6% for measles, 31.1% for tetanus and 29.1% for Hib. Prenatal exposure to pyrethroids was associated with elevated risks of low measles (but not tetanus and Hib) antibody titers at 3.5 years. Each 10-fold increase in maternal urinary concentrations of 3-PBA, trans-DCCA and cis-DCCA was associated with relative risks of 1.85 (95%CI=0.98, 3.49), 1.84 (95%CI=1.09, 3.09) and 2.43 (95%CI=1.38, 4.29), respectively. No associations were found with DDT and DDE. Associations with antibody titers at age 5 will also be presented. Conclusion: Results suggest that prenatal exposure to pyrethroids may inhibit immune response to vaccines among South African children.