Mass Administration of Ivermectin for the Elimination of Onchocerciasis Significantly Reduced and Maintained Low the Prevalence of Strongyloides stercoralis in Esmeraldas, Ecuador

Mariella Anselmi,Rosanna Prandi,Marcia Racines Orbe,Monica Marquez,Marco Albonico,Angel Guevara Espinoza,Maria Gobbo,Juan Martin Moreira,Zeno Bisoffi,Dora Buonfrate,Antonio Montresor,Rick Speare

doi:10.1371/journal.pntd.0004150

Abstract

ObjectivesTo evaluate the effect of ivermectin mass drug administration on strongyloidiasis and other soil transmitted helminthiases.MethodsWe conducted a retrospective analysis of data collected in Esmeraldas (Ecuador) during surveys conducted in areas where ivermectin was annually administered to the entire population for the control of onchocerciasis.Data from 5 surveys, conducted between 1990 (before the start of the distribution of ivermectin) and 2013 (six years after the interruption of the intervention) were analyzed. The surveys also comprised areas where ivermectin was not distributed because onchocerciasis was not endemic.Different laboratory techniques were used in the different surveys (direct fecal smear, formol-ether concentration, IFAT and IVD ELISA for Strongyloides stercoralis).ResultsIn the areas where ivermectin was distributed the strongyloidiasis prevalence fell from 6.8% in 1990 to zero in 1996 and 1999. In 2013 prevalence in children was zero with stool examination and 1.3% with serology, in adult 0.7% and 2.7%.In areas not covered by ivermectin distribution the prevalence was 23.5% and 16.1% in 1996 and 1999, respectively. In 2013 the prevalence was 0.6% with fecal exam and 9.3% with serology in children and 2.3% and 17.9% in adults.Regarding other soil transmitted helminthiases: in areas where ivermectin was distributed the prevalence of T. trichiura was significantly reduced, while A. lumbricoides and hookworms were seemingly unaffected.ConclusionsPeriodic mass distribution of ivermectin had a significant impact on the prevalence of strongyloidiasis, less on trichuriasis and apparently no effect on ascariasis and hookworm infections.

Highlights

The Onchocerciasis Elimination Programme of the Americas (OEPA) is a regional initiative with the goal of eliminating morbidity and interrupting transmission of river blindness in six endemic countries in the Americas [1]
In the areas where ivermectin was distributed the strongyloidiasis prevalence fell from 6.8% in 1990 to zero in 1996 and 1999
Periodic mass distribution of ivermectin had a significant impact on the prevalence of strongyloidiasis, less on trichuriasis and apparently no effect on ascariasis and hookworm infections

Summary

Introduction

The Onchocerciasis Elimination Programme of the Americas (OEPA) is a regional initiative with the goal of eliminating morbidity and interrupting transmission of river blindness in six endemic countries in the Americas [1]. In Ecuador, the main endemic focus of onchocerciasis was in the province of Esmeraldas, North of the country, where the elimination of onchocerciasis was achieved thanks to a community-based, sustained effort, based on the mass drug administration (MDA) of ivermectin once a year from 1991 to 2000, twice, from 2001 to 2007 in all communities along Santiago river where onchocerciasis was endemic (while in the other endemic areas the treatment was carried on until 2009). Objective of this work is to estimate the effect of ivermectin MDA on the prevalence of S. stercoralis as well as of other soil transmitted helminths (STH) (Ascaris lumbricoides, Trichuris trichiura and hookworm) through: a) comparison of results from fecal surveys carried out before, during and after the distribution program; b) comparison of results from fecal and serological surveys carried out in areas targeted versus areas not targeted to ivermectin treatment, during and after the onchocerciasis elimination program

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