Relationship between Bacille Calmette-Guérin vaccination, Mantoux test positivity, and geohelminth infection

Abstract

To investigate the potential protective effects of Bacille Calmette-Guerin (BCG) vaccination scar and sensitization to tuberculin against geohelminth infections, we conducted a cross-sectional study among school age children in rural communities in Pichincha Province in Ecuador where BCG vaccination is routinely given at birth. A total of 944 children aged 8-14 years were evaluated for the presence of BCG scars and sensitization to tuberculin, and underwent faecal examination for geohelminth parasites. BCG scars were present in 88.2% of children and positive Mantoux tests were observed in 19.1% of children. Geohelminth prevalence was high with 70.3% infected with any parasite, 52.1% with Ascaris lumbricoides, 52.3% with Trichuris trichiura, 7.6% with Ancylostoma duodenale, and 3.0% with Strongyloides stercoralis. In multivariate analyses, the presence of BCG vaccine scars was not significantly associated with infections with any geohelminth parasite (adjusted odds ratio [AOR] = 0.74, 95% CI 0.43-1.28, P = 0.28), but an inverse association was observed for infections with S. stercoralis that was of borderline statistical significance (AOR = 0.38, 95% CI 0.15-1.00, P = 0.05). There were no associations between sensitization to tuberculin and infection with geohelminth parasites. The data provide little support for an important protective role of neonatal BCG vaccination or current mycobacterial sensitization against geohelminth infections.

Tuberculin Skin-Test Reactions Are Unaffected by the Severity of Hyperendemic Intestinal Helminth Infections and Co-Infections

“…is probably explained by enhanced hygiene or frequent antihelminthic administration in health-care staff. Because almost all participants had intestinal helminth infections, similar to other studies in this region, 18,19 the current research could not meaningfully compare naturally infected versus uninfected individuals. However, our previous research in a nearby community 12 and research in other settings 19 have shown that TST results do not differ between individuals who are naturally infected versus naturally uninfected with intestinal helminths.…”

“…Because almost all participants had intestinal helminth infections, similar to other studies in this region, 18,19 the current research could not meaningfully compare naturally infected versus uninfected individuals. However, our previous research in a nearby community 12 and research in other settings 19 have shown that TST results do not differ between individuals who are naturally infected versus naturally uninfected with intestinal helminths. The present research extended this knowledge by showing that there was no association between TST results and low versus high helminth egg burden or co-infections with multiple helminth species.…”

“…18,19 Despite this, gastrointestinal symptoms were rare and were not associated with high helminth burden or helminth co-infections. 20 The stool microscopy was performed by staff blinded to information about participants, and it was striking that only health-care professionals were free from intestinal helminths.…”

Risk Factors for Soil-Transmitted Helminth Infections during the First 3 Years of Life in the Tropics; Findings from a Birth Cohort

“…Having a younger mother of Afro-Ecuadorian ethnicity, being lower in the birth order, and household overcrowding were also independently associated with childhood STH infections. Previous studies have identified similar factors as being associated with risk of STH infection [4], [17], [30], [31], [32], [33], [34]. Among public health interventions that could be implemented to reduce STH infection risk in pre-school children are the provision of sanitation, clean water, and education of mothers in appropriate hygienic behaviours.…”

Is there interference in the interpretation of the tuberculin skin test in children with intestinal parasitic infestation?

“…In 2003, 944 Ecuadorian children aged between 8 and 11 years were studied. 12 The prevalence of infested children was very high (70.3%), mostly with T. trichiura (52.3%) and A. lumbricoides (52.1%). No significant differences were found in the TST results between infested and non-infested children.…”