Latent Tuberculosis Infection in a Migrant Agricultural Community in Baja California, Mexico

Abstract

The objectives were to estimate the prevalence and identify correlates of latent tuberculosis infection (LTBI) among residents of a migrant agricultural community in San Quintín, Baja-California, Mexico. Residents completed a questionnaire and had their blood tested for LTBI using the QuantiFERON®-TB Gold In-Tube (QFT) assay. Among 133 participants, 39.8% (95% CI 31.5–48.7%) tested QFT-positive. Having crossed the U.S.-Mexican border since living in San Quintin (P = 0.03), consuming unpasteurized milk (P = 0.02) and receiving health care at IMSS-Oportunidades in the last 6 months (P = 0.03) were independently associated with QFT-positivity. High LTBI prevalence in this community emphasizes the need for TB education and LTBI treatment for its residents. Association with travel to the U.S. suggests the potential for TB transmission across borders. Higher QFT-positivity among those consuming unpasteurized milk could indicate M. bovis infection, previously reported among Mexican migrants living in U.S. border cities.

A Systematic Review on TST and IGRA Tests Used for Diagnosis of LTBI in Immigrants

“…Across the 51 studies, 34 studies looked at TST alone and 9 studies looked at IGRAs alone [57][58][59][60][61][62][63][64][65]; 8 studies compared TST and IGRAs [66][67][68][69][70][71][72][73]. Just 8 studies excluded those with active TB from their study [23,32,34,50,66,68,69,71].…”

“…Just 8 studies excluded those with active TB from their study [23,32,34,50,66,68,69,71]. Only 16 studies reported on BCG vaccination with 9 using BCG scar as evidence of vaccination [28,32,33,53,55,58,60,71,72], 5 using BCG self-reporting as evidence [23,29,35,66,69], and 2 using BCG vaccination schedule in country of origin as a proxy for BCG vaccination [48,73], although BCG vaccination rates varied considerably across studies (0-100 %). The characteristics of the 51 included studies are included in Table 1 and in the supplementary text, which summarizes each of the 51 studies included in the review.…”

“…Male gender was not found to be significantly associated with IGRA positivity in three studies [60,63,65], however two concluded significant association [58,62]. Country of origin was significantly associated with IGRA positivity in several studies [58,59,62,64,66,72], however three saw no association [60,63,67]. Increasing age was a significant factor for a positive IGRA in three studies [62,64,72], however the same conclusion was not found in one [67].…”

“…Age was not significant in 4 studies [27,35,36,67] although two studies [35,36] were performed in subjects\18 years old and therefore were not able to look at older age categories. Male gender was not found to be significantly associated with IGRA positivity in three studies [60,63,65], however two concluded significant association [58,62]. Country of origin was significantly associated with IGRA positivity in several studies [58,59,62,64,66,72], however three saw no association [60,63,67].…”

Is Bacille Calmette-Guérin (BCG) Vaccine a Known Risk Factor for Latent Tuberculosis Infection?: A Cross-sectional Study on 180 New Immigrants from BCG-vaccinated Countries to Kuwait

“…A similar significance in our research results of those participants having past history of exposures to various animals and positive BCG scar without LTBI diagnosis. On the contrary Grafein et al (2011) [23] concluded that there was an absence of a significant association between the presence of LTBI and a BCG scar, but presence of a significant association with consumption of unpasteurized (cows) milk in the past 6 months, which can be related to Mycobacterium bovis.…”