Multibacillary leprosy and the elderly: a field for further research

Introduction: Leprosy is an important public health problem in Brazil where 28,761 new cases were diagnosed in 2015 and 7.3% were among children, indicating active transmission. Objectives: This study was designed to analyse leprosy indicators in a Brazilian municipality (Mossoro, RN) and to identify the burden of Mycobacterium leprae infection among elderly residents using ML-Flow assay. Results: Leprosy continues to be hyperendemic in Mossoro and does not present signs of decline. However, both the general new case detection rate and the detection of MB cases were higher among 60-79 year olds. The percentage of new cases classified as MB increased progressively by age group and reached 67.7% among those with 60 or more years of age (180/266). A hyperendemic neighbourhood was selected for a diagnostic campaign and a total of 504 elderly individuals were tested with ML Flow test, which was strongly positive in four people (0.8%) and samples from skin biopsy of these subjects were also qPCR positive. Two new MB cases were confirmed, one of which had no cutaneous lesions. Conclusions: MB leprosy appears to be more frequent among the elderly regardless of whether the disease is experiencing or not a period of decline. According to our results and literature review we hypothesized that the greatest incidence of leprosy by age apparently is related to the life expectancy of the population. These characteristics suggest that active case finding campaigns for untreated MB leprosy among the elderly may be useful in endemic areas as an innovative complementary strategy to interrupt the transmission of M. leprae.