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

Introduction: This study measured the prevalence and correlates of latent tuberculosis infection (LTBI) among residents of a migrant agricultural community (colonia) in San Quintín, Baja California, Mexico. Methods: A representative sample of colonia residents ≥18 years old were invited over a 2-day period to complete a questionnaire and have their blood tested for TB infection using the QuantiFERON®-TB Gold In-Tube (QFT) assay. Information regarding sociodemographics, history of tuberculosis (TB), TB knowledge, and travel patterns were assessed. Participants with symptoms suggestive of active TB were referred to a municipal health clinic for diagnosis and care. Results: Among 133 participants, 39.8% (95% CI 31.5%-48.7%) were QFT-positive. Only 10 (7.3%) participants reported symptoms suggestive of active TB; none had active TB. The prevalence among men (38.3%) and women (42.2%) was not statistically different. Having crossed the U.S. Mexican border since living in the Colonia (p=0.02), consuming unpasteurized milk (p=0.017) and receiving health care at IMSS Oportunidades, a clinic for underprivileged rural Mexican families, in the last six months (p=0.04) were independently associated with QFT-positivity in multivariate analysis. Conclusion: The high prevalence of LTBI among residents of this community emphasizes the importance of LTBI treatment as a strategy for improved TB control. Association with travel history to the U.S. suggests that TB transmission may occur beyond Mexican borders. Furthermore, the association with consuming raw milk could indicate M. bovis infection, which has lower survival compared with M. tuberculosis and has been reported among Mexican migrants living in U.S. border cities.