Patterns of Migration and Risks Associated with Leprosy among Migrants in Maranhão, Brazil

Abstract

Leprosy remains a public health problem in Brazil with new case incidence exceeding World Health Organization (WHO) goals in endemic clusters throughout the country. Migration can facilitate movement of disease between endemic and non-endemic areas, and has been considered a possible factor in continued leprosy incidence in Brazil. A study was conducted to investigate migration as a risk factor for leprosy. The study had three aims: (1) examine past five year migration as a risk factor for leprosy, (2) describe and compare geographic and temporal patterns of migration among past 5-year migrants with leprosy and a control group, and (3) examine social determinants of health associated with leprosy among past 5-year migrants. The study implemented a matched case-control design and analysis comparing individuals newly diagnosed with leprosy (n = 340) and a clinically unapparent control group (n = 340) without clinical signs of leprosy, matched for age, sex and location in four endemic municipalities in the state of Maranhão, northeastern Brazil. Fishers exact test was used to conduct bivariate analyses. A multivariate logistic regression analysis was employed to control for possible confounding variables. Eighty cases (23.5%) migrated 5-years prior to diagnosis, and 55 controls (16.2%) migrated 5-years prior to the corresponding case diagnosis. Past 5 year migration was found to be associated with leprosy (OR: 1.59; 95% CI 1.07–2.38; p = 0.02), and remained significantly associated with leprosy after controlling for leprosy contact in the family, household, and family/household contact. Poverty, as well as leprosy contact in the family, household and other leprosy contact, was associated with leprosy among past 5-year migrants in the bivariate analysis. Alcohol consumption was also associated with leprosy, a relevant risk factor in susceptibility to infection that should be explored in future research. Our findings provide insight into patterns of migration to localize focused control efforts in endemic areas with high population mobility.

Author Summary

In Brazil, leprosy remains a significant public health problem in endemic clusters of high transmission risk throughout the country. Migration is thought to be a factor associated with continued leprosy transmission, as migration has also been found to be associated with other Neglected Tropical Diseases (NTDs). We analyzed the association between past five year migration and leprosy as part of a larger epidemiological study evaluating risk factors for infection among recently diagnosed leprosy cases (n = 340) and a matched clinically unapparent control group (n = 340) in the northeastern state of Maranhão. Among migrants with leprosy, 23.5% (n = 80) migrated in the past five years, with 16.2% (n = 55) of the control group. Past five year migration was significantly associated with leprosy, and remained significant after controlling for household and familial contact as potential confounders. Factors found to be associated with leprosy among past 5-year migrants included alcohol consumption, poverty, and household, family and other leprosy contact. Key patterns of movement emerged from the study that may aid future regional leprosy control efforts.