Abstract
BackgroundHelminth infections can negatively affect the immunologic host control, which may increase the risk of progression from latent Mycobacterium tuberculosis infection to tuberculosis (TB) disease and alter the clinical presentation of TB. We assessed the prevalence and determined the clinical relevance of helminth co-infection among TB patients and household contact controls in urban Tanzania.MethodologyBetween November 2013 and October 2015, we enrolled adult (≥18 years) sputum smear-positive TB patients and household contact controls without TB during an ongoing TB cohort study in Dar es Salaam, Tanzania. We used Baermann, FLOTAC, Kato-Katz, point-of-care circulating cathodic antigen, and urine filtration to diagnose helminth infections. Multivariable logistic regression models with and without random effects for households were used to assess for associations between helminth infection and TB.Principal findingsA total of 597 TB patients and 375 household contact controls were included. The median age was 33 years and 60.2% (585/972) were men. The prevalence of any helminth infection among TB patients was 31.8% (190/597) and 25.9% (97/375) among controls. Strongyloides stercoralis was the predominant helminth species (16.6%, 161), followed by hookworm (9.0%, 87) and Schistosoma mansoni (5.7%, 55). An infection with any helminth was not associated with TB (adjusted odds ratio (aOR) 1.26, 95% confidence interval (CI): 0.88–1.80, p = 0.22), but S. mansoni infection was (aOR 2.15, 95% CI: 1.03–4.45, p = 0.040). Moreover, S. mansoni infection was associated with lower sputum bacterial load (aOR 2.63, 95% CI: 1.38–5.26, p = 0.004) and tended to have fewer lung cavitations (aOR 0.41, 95% CI: 0.12–1.16, p = 0.088).Conclusions/SignificanceS. mansoni infection was an independent risk factor for active TB and altered the clinical presentation in TB patients. These findings suggest a role for schistosomiasis in modulating the pathogenesis of human TB. Treatment of helminths should be considered in clinical management of TB and TB control programs.
Highlights
Tuberculosis (TB), caused by Mycobacterium tuberculosis remains a challenging disease to control
Parasitic worm infections contribute to the down-regulation of the essential immune response against TB, and can increase progression from latent M. tuberculosis infection to active TB
We found that infection with the blood fluke Schistosoma mansoni was associated with active TB, while none of the other parasitic worms showed such an association
Summary
Tuberculosis (TB), caused by Mycobacterium tuberculosis remains a challenging disease to control. Where TB and helminth infections cooccur, they can affect the same individual and exacerbate the course of disease [6] Several conditions such as diabetes mellitus, malnutrition, and malignancies are known to increase the risk of progressing from latent M. tuberculosis infection to active TB [7]. The immune response to Epidemiology of TB and helminth co-infection helminth infections is characterized by the induction of CD4+ T-helper 2 (Th2) and down-regulation of CD4+ T-helper 1 (Th1) cells [12,13,14,15] This immunological imbalance has been suggested to increase the risk of progression from latent M. tuberculosis infection to active TB and to worsen the clinical outcomes.
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