[182] Tuberculosis and Latent Tuberculosis Infection Screening Among Asylum Seekers in Milan, Italy

Introduction

Since 2015, migratory flows to Italy from countries with high incidence of tuberculosis (TB), especially those in Sub-Saharan Africa and the Indian subcontinent, have increased. Social issues and political conflicts represent major reasons of migration. TB in the European Union affects mainly poor and marginalized people, including asylum seekers (AS) living in metropolitan areas. This study aimed at assessing incidence of TB and prevalence of latent TB infection (LTBI) among AS in the city of Milan, as well as the performance of the city surveillance and management system during the biennium 2016–2017.

Methods

To face this public health issue in the Milan area, a 2-level surveillance system was developed to screen AS for both TB and LTBI. AS hosted in receiving facilities could at any time self-report symptoms requiring further radiological and microbiological evaluations. However, all AS underwent an initial screening with tuberculin skin test (TST) and a questionnaire. Those presenting with a positive result were considered eligible for a chest X-ray (CXR) to assess signs compatible with TB. People under 35 years of age with negative CXR underwent further testing by interferon gamma release assay (IGRA) and received prophylactic treatment for LTBI if found to be positive to both TST and IGRA. Observed TB incidence and LTBI prevalence categorized by country and region were compared with literature data using incidence rate ratio (IRR) for incidence and Chi-square test for prevalence. A molecular surveillance, based on a 24-locus mycobacterial interspersed repetitive units/variable-number tandem repeats (MIRU/VNTR) typing system, was also implemented to evaluate if recent transmission had occurred.

Results

A total of 5,324 AS were enrolled. 89% belonged to the age groups 15-49; most were males (84%) and from Sub-Saharan African countries (69%). In 2016-17, a total of 69 active TB cases (rate 1,236/100,000 population) and a total of 865 persons with LTBI (prevalence 20%) were diagnosed. The incidence was 1,003 (IRR = 4.357; p < .001) among AS from World Health Organization African Region (WHO AFR) countries and 3,043 (IRR = 26.932; p < .001) among those from the WHO Eastern Mediterranean Region (WHO EMR) countries, that includes Somalia (20 TB cases). TB treatment success rate and defaulting rates were 80% and 12%, respectively. LTBI prevalence among AS from WHO AFR countries was 23%, similar to that observed in their countries of origin (p = .081), while a lower rate (11%) was observed in those coming from WHO EMR countries compared to that in their countries of origin (p = .012). A high rate of acceptance (93%) and adherence (90%) to LTBI prophylactic treatment were observed. The molecular surveillance by 24-MIRU/VNTR typing system allowed to determine that only 3 TB cases were due to recent transmission within Milan receiving centers.

Conclusions

Our study shows that TB incidence is high among AS and that well-coordinated screening measures are critical to early diagnosis and treatment. The high defaulting rate needs to be addressed through urgent community interventions. Prophylactic treatment of LTBI is feasible and successful in Milan, probably due to its short duration (3 months rifampicin and isoniazid). The attrition observed between the 2 levels of the surveillance system could be reduced through better data sharing, i.e., including CXR data in databases.