Abstract
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 (M.tb) infection. We hypothesized that deworming following documented M.tb 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 (QTF) responses among children from a setting with a known high burden of M.tb and helminth co-infection in Cape Town, South Africa. Children aged 6-15 years with documented M.tb exposure were enrolled. Ascaris lumbricoides status was measured by Ascaris-specific IgE and stool microscopy.
RESULTS: 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 enrolment was not associated with a negative TST at 3 months (OR 0.61, 95% CI 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 (OR 0.49, 95% CI 0.23-1.04, p=0.06). In multivariable analysis, deworming was not associated with TST status (aOR 0.62, 95% CI 0.34- 1.10, p=0.10). There was no association between deworming and QTF status.
CONCLUSIONS: Deworming in children with recent M.tb exposure is associated with a trend towards a negative TST result. Timing of deworming might influence interpretation of TST in settings with high burdens of TB and helminths.