Leprosy in the Wake of Helminth Immunomodulation: A study on the impact of deworming on leprosy outcomes in Vale do Rio Doce, Brazil Open Access
Jones, Cynthia (Spring 2019)
Published
Abstract
Background: Helminthic immunomodulation is believed to affect the human immune response to several diseases of public health importance, including leprosy. The implementation of a four-year school-based deworming and leprosy detection campaign throughout Brazil brings about an important opportunity to study the as-yet unidentified effects of soil-transmitted helminth treatment on the incidence of leprosy and its subtypes.
Methods: We conducted two analyses on incident cases of leprosy retrieved from SINAN, Brazil’s nationally notifiable disease surveillance system, between 2002 and early 2017. The first was a difference-in-differences analysis in which trends in leprosy outcomes within Vale Do Rio Doce, Minas Gerais, Brazil, were compared in the years leading up to the commencement of Brazil’s national school-based deworming campaign through the period during which anthelmintic treatment actively occurred in selected municipalities. Linear regression was used to compare the effect of school-based deworming on leprosy new case detection rate and percent multibacillary cases in the general population and among children. A spatial hotspot analysis was conducted and evaluated to complement the difference-in-differences models and to determine the effect of school-based deworming on inclusion in a leprosy hotspot.
Results: No significant effect of school-based anthelmintic treatment on new case detection rate, percent of multibacillary cases, or pediatric new cases and percent of multibacillary cases was observed from the aspatial difference-in-differences model. Minor changes in hotspot locations were observed throughout the study period; however, no statistically significant difference in hotspot changes between intervention and control groups was detected.
Conclusions: While no significant effect of anthelmintic treatment on leprosy incidence or percent of multibacillary cases was observed, the cluster analysis did reveal areas of consistently high leprosy transmission. These areas coincide largely with municipalities selected to take part in annual school-based deworming, presenting future opportunities for further integration of programs to eliminate and cooperatively control these diseases. Additional analyses are essential to identify the true effect of anthelmintic treatment on leprosy incidence and polarization, as well as further characterize the relationship between these diseases.
Table of Contents
Chapter I: Literature Review .............................................................................................. 1
Leprosy: past and present........................................................................................ 1
Leprosy: clinical profile, epidemiology, and risk factors ....................................... 1
Leprosy histopathology ........................................................................................... 4
Soil-transmitted helminthiases ................................................................................ 5
Helminthic immunomodulation .............................................................................. 7
Immunomodulation spill-over effects ..................................................................... 7
STH-leprosy co-infection studies ........................................................................... 8
Brazil’s Neglected Tropical Diseases (NTD) Campaign ........................................ 9
Goals of this Study ................................................................................................ 10
Chapter II: Manuscript ..................................................................................................... 11
Abstract: ................................................................................................................ 11
Introduction ........................................................................................................... 12
Methods................................................................................................................. 15
Results ................................................................................................................... 21
Discussion ............................................................................................................. 26
References ......................................................................................................................... 32
Tables ................................................................................................................................ 40
Figures............................................................................................................................... 48
Chapter III: Summary, Public Health Implications, Possible Future Directions ............. 60
Appendices ........................................................................................................................ 62
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