The Effect of Deworming on Tests of Tuberculosis Infection in Children With Recent Tuberculosis Exposure

BACKGROUND: Helminth infestations are associated with T-helper cell type 2 (Th2) immune responses, leading to suppression of Th1 responses required to control Mycobacterium tuberculosis infection. We hypothesized that deworming after documented M. tuberculosis exposure might improve Th1 immune responses. METHODS: This was a randomized controlled trial comparing the effect of early versus delayed (after 3 months) deworming on tuberculin skin testing (TST) and Quantiferon-Gold-in-tube responses among children from a setting with a known high burden of M. tuberculosis and helminth co-infection in Cape Town, South Africa. Children aged 6 to 15 years with documented M. tuberculosis exposure were enrolled. Ascaris lumbricoides status was measured by Ascaris-specific IgE and stool microscopy. RESULTS: A total of 250 children (mean age, 9.6 years) were enrolled; 11.9% (27/227) were Ascaris stool microscopy positive and 54.2% (135/249) were Ascaris stool and/or IgE positive (Ascaris status). In univariable analysis, deworming at enrollment was not associated with a negative TST at 3 months (odds ratio, 0.61; 95% confidence interval, 0.35-1.07; P = 0.08). In stratified analysis, children with a positive Ascaris status were more likely to be TST negative at 3 months if dewormed early (odds ratio, 0.49; 95% confidence interval, 0.23-1.04; P = 0.06). In multivariable analysis, deworming was not associated with TST status (adjusted odds ratios, 0.62; 95% confidence interval, 0.34-1.10; P = 0.10). There was no association between deworming and Quantiferon-Gold-in-tube status. CONCLUSIONS: Deworming in children with recent M. tuberculosis exposure is associated with a trend toward a negative TST result. Timing of deworming might influence interpretation of TST in settings with high burdens of tuberculosis and helminths.