Autochthonous leprosy in Spain: Has the transmission of Mycobacterium leprae stopped?

Background: The aim of this study is to explore whether transmission of M. leprae has ceased in Spain, based upon the patterns and trends of notified cases. Methodology: Data on new cases reported to the National Leprosy Registry between the years 2003–2018 were extracted. In absence of detailed travel history, cases were considered "autochthonous" or "imported" based on whether they were born within or outside of Spain. These data were analyzed by age, sex, clinical type, country of origin, and location of residence at time of notification. Principal findings: Data were available on 61 autochthonous and 199 imported cases since 2003. There were clear declines in incidence in both groups, and more imported than autochthonous cases every year since 2006. Autochthonous cases were more frequently multibacillary and had older age at diagnosis compared to imported cases. All the autochthonous cases had been born before 1985 and were more than 25 years old at diagnosis. Male-to-female ratio increased with time for autochthonous cases (except for the last time period). The imported cases originated from 25 countries, half of them from Brasil and Paraguay. Autochthonous cases were mainly distributed in the traditionally endemic regions, especially Andalucía and the eastern Mediterranean coast. Conclusions: Autochthonous and imported cases have different epidemiologic patterns in Spain. There was a clear decline in incidence rates of autochthonous disease, and patterns consistent with those reported from other regions where transmission has ceased. Autochthonous transmission of M. leprae is likely to have now effectively stopped in Spain. Author summary: There is increasing interest in the potential for cessation of transmission of M Leprae. In several European countries, as social and economic conditions have improved, leprosy rates have declined and transmission appears to have stopped. The epidemiology of leprosy is still not fully understood: the study of leprosy in countries with low incidence rates can give valuable information on its epidemiology that could inform eradication campaigns in other countries. Leprosy has been endemic in Spain for centuries and, despite very low incidence in the last decades, new autochthonous cases are diagnosed every year. In this study, we analyse the epidemiologic trends of autochthonous leprosy in Spain in recent years. Our data provide insights into the dramatic decline of leprosy in Spain since 1950, and, for the cases diagnosed after 2003, show a shift from a predominace of disease attributable to locally acquired infection to overwhelming predominance of disease attributable to infections acquired elsewhere. The comparison of patterns of disease between the autochthonous and imported cases shows important differences, suggesting that the most recent autochthonous cases were those with long incubation periods after infections which were acquired many years ago. The epidemiologic trends are similar to those found in other countries with declining incidence and suggest that transmission effectively stopped in Spain more than two decades ago. [ABSTRACT FROM AUTHOR]