Abstract
BackgroundLeprosy remains a public health problem in Brazil. Although the overall number of new cases is declining, there are still areas with a high disease burden, such as Pará State in the north of the country. We aim to predict future trends in new case detection rate (NCDR) and explore the potential impact of contact tracing and chemoprophylaxis on NCDR in Pará State.MethodsWe used SIMCOLEP, an existing individual-based model for the transmission and control of M. leprae, in a population structured by households. The model was quantified to simulate the population and observed NCDR of leprosy in Pará State for the period 1990 to 2014. The baseline scenario was the current control program, consisting of multidrug therapy, passive case detection, and active case detection from 2003 onwards. Future projections of the NCDR were made until 2050 given the continuation of the current control program (i.e. baseline). We further investigated the potential impact of two scenarios for future control of leprosy: 1) discontinuation of contact tracing; and 2) continuation of current control in combination with chemoprophylaxis. Both scenarios started in 2015 and were projected until 2050.ResultsThe modelled NCDR in Pará State after 2014 shows a continuous downward trend, reaching the official elimination target of 10 cases per 100,000 population by 2030. The cessation of systematic contact tracing would not result in a higher NCDR in the long run. Systematic contact tracing in combination with chemoprophylaxis for contacts would reduce the NCDR by 40% and bring attainment of the elimination target two years forward to 2028.ConclusionThe NCDR of leprosy continues to decrease in Pará State. Elimination of leprosy as a public health problem could possibly be achieved around 2030, if the current control program is maintained. Providing chemoprophylaxis would decrease the NCDR further and would bring elimination forward by two years.
Highlights
Leprosy, known as Hansen Disease, is caused by Mycobacterium leprae
The cessation of systematic contact tracing would not result in a higher new case detection rate (NCDR) in the long run
Systematic contact tracing in combination with chemoprophylaxis for contacts would reduce the NCDR by 40% and bring attainment of the elimination target two years forward to 2028
Summary
Known as Hansen Disease, is caused by Mycobacterium leprae. Every year more than 210,000 new cases are detected worldwide [1]. Brazil was unsuccessful in bringing the prevalence of leprosy below the official WHO’s ‘elimination as public health problem’ goal of less than 10 cases per 100,000 population by the year 2000 [2]. In 2010 the leprosy prevalence rate in Brazil was 15.6 per 100,000 and the new case detection rate (NCDR) 18.2 per 100,000, the NCDR had dropped by about 35% between 2001 and 2010 [3]. The overall number of new cases is declining, there are still areas with a high disease burden, such as Pará State in the north of the country. We aim to predict future trends in new case detection rate (NCDR) and explore the potential impact of contact tracing and chemoprophylaxis on NCDR in Pará State
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