Latent Tuberculosis Infections in Different Intensity of Exposure within Moroccan Population: Influence of Age and Bacille Calmette-Guérin Vaccination

Abstract

Background: In Morocco, latent tuberculosis infection (LTBI) is a public health concern affected by the country's location as transit area between sub-Saharan Africa with high TB burden to Europe. This study aimed to assess the influence of exposure intensity to Mycobacterium tuberculosis (Mtb), age, and Bacille Calmette-Guérin (BCG) vaccination on LTBI prevalence in Morocco.

Methods: A cross-sectional study of 131 participants, including 98 non-exposed healthy volunteers (NEHV) and 33 healthcare workers exposed to active TB (exposed healthcare workers [EHCW]), was conducted. The Interferon-γ Release Assay (IGRA) was used to detect LTBI, and results were analyzed according to participants' age and BCG vaccination status.

Results: EHCW showed a higher prevalence of LTBI than NEHV (36.7% vs. 57.6%) and of EHCW were positive for LTBI. In both groups, the mean age of those with LTBI was higher than those without. Furthermore, we showed within both groups, that LTBI prevalence was positively associated with subjects less covered by BCG vaccination in comparison with subjects likely totally covered by this vaccination (adjusted odds ratio [aOR], 2.783; 95% confidence intervals [CI], 1.180-6.57; P = 0, 01), (aOR, 6.717; 95% CI, 1.254-35.977; P = 0.02).

Conclusion: Our results showed that in the Moroccan TB epidemic context, the prevalence of LTBI still lower among healthy adults general population than within EHCW. Furthermore, this LTBI showed to be positively impacted by age in the two condition of exposure. We also showed that BCG vaccination seems to affect the prevalence of LTBI within both high and low intensity of exposure to Mtb infection.