Migration and leprosy in Brazil

Background: Leprosy is among the Neglected Tropical Diseases (NTDs), and is an endemic public health problem in high-risk clusters throughout Brazil. Leprosy is caused by the intracellular bacteria Mycobacterium leprae, affecting the skin and peripheral nerve function. The disease can cause significant disabilities through nerve damage and secondary infection. Nasal mucosa is considered the primary transmission site due to the presence of active bacilli. However, transmission continues to remain unclear. Environmental risk has also been considered, as leprosy has been found in local water and soil sources in endemic areas, and leprosy mycobacteria can survive outside of the body for up to 60 days.
While household contact with multibacillary cases (>5 lesions) remains the primary risk factor for leprosy, genetic relationships are thought to be a risk independent of physical contact. Socioeconomic factors and conditions of poverty, such as inadequate housing and sanitation, poor nutrition and household density, also related to leprosy contact proximity, have been found to be risk factors in Brazil and other countries. These factors can increase the risk for both leprosy transmission and onset of leprosy symptoms, particularly when factors associated with poverty compromise immune response.
Migration is considered to be a social determinant of NTDs, including leprosy. Social disparities and conditions associated with migration place non-immune migrants at risk for infection when exposed to disease. Migration can additionally influence the distribution of disease through movement of baciliferous individuals into previously non-endemic areas. Thus, leprosy control may be hindered by increased transmission and distribution due to migration. In Brazil, leprosy new case incidence at 1.77/10.000 inhabitants nationally remains above the World Health Organization elimination goal of <1 case per 10,000, with some states exceeding 5.0 cases per 10,000 in the North, Central West and Northeast areas of the country.
Objectives: The overarching goal of this PhD research was to support the Brazilian Leprosy Control program to improve targeted service delivery towards migrating populations, by investigating social, behavioral and other factors associated with migration and leprosy in the Northeast of Brazil.
There were four primary objectives: 1) to identify motives and determinants for residence change after leprosy diagnosis; 2) to describe factors influencing migration before and after diagnosis among those infected with leprosy; 3) to identify social, environmental and behavioral factors associated with migration in individuals newly diagnosed with leprosy, compared to an uninfected reference population; and 4) to determine patterns of migration and migration risks associated with leprosy infection among past five year migrants.
Methods: This study entailed two comprehensive population-based epidemiological studies conducted in areas identified by the Brazilian Ministry of Health as highly endemic clusters for leprosy transmission, in the states of Tocantins and Maranhão in the Northeast of Brazil. In four municipalities of Maranhão, individuals newly diagnosed with leprosy in 2009 and 2010 and an uninfected reference population matched by age, sex and geographic location were interviewed. In Tocantins, individuals newly diagnosed with leprosy in 79 municipalities between 2006 and 2008 were interviewed, using structured questionnaires.
Results: Leprosy was found to be associated with migration, and more severe multibacillary leprosy was prominent among migrants. Among past five year migrants, leprosy was associated with household and family leprosy contact, past five year alcohol consumption and poverty. Many of the factors associated with leprosy infection were also associated with migration among those with leprosy. Migration was largely facilitated through familial relationships and was associated with poverty and indicators of poverty, and past five year alcohol consumption. These factors were unique to those with leprosy in comparison to an uninfected reference population. Family separation was also associated with migration, although this was significant among all migrants and not only those with leprosy. Limited access to health services was a barrier that was associated with migration among those with leprosy, although the majority of residence change after diagnosis was for lifestyle changes and not for the purpose of seeking medical care.
Conclusion: The relationship between internal migration and leprosy, and social and behavioral aspects influencing migration among those with leprosy has been investigated. Leprosy was associated with migration, and further investigation identified social and behavioral factors unique to migrants such as poverty, alcohol consumption, as well as lifestyle stressor separation from family and friends’ which was associated with both migration and leprosy infection. Additionally, late diagnosis is evident in migrants with multibacillary leprosy. Future research should assess the role of alcohol consumption and life stressors in leprosy transmission and symptom onset.
National control efforts should take into account factors which distinguish migrants from non-migrant and uninfected populations. Based on these, interventions targeting risk factors, i.e. substance abuse and stress in affected populations, could help to reduce leprosy transmission. The extension of clinic hours and health service availability that meet the needs of migrating populations is recommended in order to increase early leprosy diagnosis and reduce disability.